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Late Jurassic lithological evolution and carbon-isotope stratigraphy of the western Tethys
Abstract
A new high-resolution carbon-isotope stratigraphy of the Late Jurassic has been generated from Tethyan carbonate sections. Sections chosen for this study are from the Helvetic nappes of the Swiss Alps, from the Jura Mountains, from the Provence (France) and from the Southern Alps (N. Italy). The limestones and marls used for this isotope geochemical investigation were deposited along the northern (Helvetics, Jura, Provence) and the southern (S. Alps) margin of the Alpine Tethys. Isotope curves were first established in well-dated sections of the Jura Mountains, the Southern Alps and the Vocontian Basin. Isotope curves generated from the poorly dated Helvetic nappe sections could then be correlated with the bisotratigraphically dated sections. This comparison produces greatly improved age control for the Helvetic sections and a more detailed composite δ 13C curve for the Late Jurassic than has been published previously. The composite δ 13C curve features two short-lived negative excursions in the Oxfordian, a δ 13C maximum in the Late Kimmeridgian and steadily decreasing δ 13C values throughout the Tithonian. These δ 13C events are consistent with previous, lower resolution data sets and are valuable tie-points, which can be used for correlating upper Jurassic successions among different lithologies and across different depositional settings. The new carbon isotope record is not only useful as a stratigraphic tool but it records fluctuations in Late Jurassic global carbon cycling. The negative carbon isotope events lasting up to a few 10 5 years are interpreted as primary perturbation signals recording anomalies in the atmospheric and marine carbon reservoirs. The perturbations of the global C-cycle were triggered by a sudden and massive release of methane stored in deep-sea gas hydrates. Positive carbon isotope excursions lasting up to millions of years record changes in carbonate and organic carbon production and sedimentation.
... All Results were reported in the conventional δ-notation in per mil relative to the Vienna Pee Dee Belemnite (V-PDB) and Sun et al., 1997;Wang et al., 2004b;Ding et al., 2013;Fang et al., 2016;Li et al., 2020). The reference age scale for the chronostratigraphy is from Ogg et al. (2016). M. = Middle; Lt. = Late. ...
... The continuing global subduction system has destroyed the majority of oceanic crusts prior to the Cretaceous (e.g., Jenkyns et al., 2002;Katz et al., 2005;Meyers, 2015), and there is thus a sparse record of successive Jurassic marine sedimentary rocks (Fig. 6). Padden et al. (2002) initially reported the Upper Jurassic δ 13 C carb succession of the Montsalvens section that consists of hemipelagic and pelagic carbonates along the northern margin of the Alpine Tethys and is regarded as representative of the Tethys δ 13 C record with relatively high resolution data. DSDP site 534, a drilling in the Atlantic with a precise magnetobiostratigraphic framework, spans the entire Upper Jurassic and provides a low-resolution δ 13 C carb record . ...
... Solid trend lines in the Amdo section are calculated within the PAST software using a LOWESS smoothing (α = 0.1) (Hammer et al., 2001). Time scale accords to Ogg et al. (2016). The A-G letters (pink for peak and yellow for trough) refer to peculiar characteristics of the carbon isotopes that can be correlated across the global records. ...
The Jurassic oceanographic and climatic evolution is considered to be related to the breakup of Pangaea. As a crucial component of the carbon cycle, atmospheric CO2 concentration (pCO2) has been postulated as a main driver for climate change during the Jurassic, and concomitant changes in paleo-oceanographic conditions occurred as a result. In this study, we present a high-resolution organic matter (kerogen) carbon isotope dataset (δ¹³Ckerogen) from Upper Jurassic marine sedimentary rocks in the Qiangtang Basin, Tibet. The δ¹³Ckerogen result contains a genuine record concerning the response of the eastern Tethys to exogenic carbon cycle perturbations in both marine and atmospheric reservoirs and is also consistent with the high-resolution bulk carbonate and organic matter carbon-isotope records from the Atlantic and western Tethys. The relative fractionation of carbon isotopes in organic matter vs. carbonate species, defined as Δ¹³C (δ¹³Ccarb-δ¹³Ckerogen), and the secular trend of atmospheric pCO2 over the Late Jurassic that is calculated from the high-resolution δ¹³Ckerogen values indicate a cold Callovian-Oxfordian transition, a long-term increasing but fluctuating Kimmeridgian and a prominent early Tithonian cooling event (ETCE). The pronounced temperature plateau during the late Kimmeridgian-early Tithonian was contemporaneous with the occurrence of major magmatic events during the Late Jurassic, while the ETCE has been possibly attributed to major changes in oceanic circulation patterns. Additionally, reconstructed atmospheric pCO2 values show very small differences to values using phytane- and stomatal density-based pCO2 calculations, providing an alternative estimate for accurate identification of the paleoclimatic framework of this enigmatic interval in the Mesozoic.
... (Sun et al., 1997;Wang et al., 2004;Ding et al., 2013;Fang et al., 2016). Time scale accords to Ogg et al. (2016). M. = Middle; Lt. = Late. ...
... The δ 13 C carb values range from +0.3‰ to +5.2‰ with the average + 2.3‰ in the Amdo section broadly corresponding to the coeval (Late Jurassic) range known from the western Tethys and Boreal Realm platforms and Atlantic pelagic deposits (e.g., Jenkyns, 1996;Bartolini et al., 1999;Padden et al., 2002;Rais et al., 2007;Coimbra et al., 2009Coimbra et al., , 2014Dera et al., 2011a). Representative Late Jurassic isotopic succession documented by pelagic and hemipelagic bulk carbonates from the Tethyan margin, Central Atlantic and Pacific, like Montsalvens section in Switzerland (Padden et al., 2002), the Xausa and Terminilletto sections in Italy (Weissert and Channell, 1989;Bartolini et al., 1999), the Jabal Nukhayl section from the Oman (Wohlwend, 2015;Wohlwend et al., 2017) and two Jurassic-Cretaceous deep-sea drillings in Atlantic (DSDP Site 534 and 105; Katz et al., 2005;Tremolada et al., 2006), improve the accuracy of the transcontinental stratigraphic correlation and thus establish the Upper Jurassic δ 13 C profile in eastern Tethys. ...
... The P-CIE 3 with amplitudes of 1.5‰ correlates to a similar positive excursion described for the Upper Kimmeridgian that is clearly documented in the Terminilletto section from Italy ( Bartolini et al., 1999) and the Eulenflucht-1 core from Germany (Bai et al., 2017). Ahead of the P-CIE 3, a short-term fluctuation of carbon-isotope curve at the lower Kimmeridgian enables a good correlation with the successions from the European Boreal region (Padden et al., 2002;Bai et al., 2017) and the western Panthalassa (Kakizaki and Kano, 2014). ...
An Upper Jurassic succession of deep-marine limestones, marls and claystones preserved in the Ambo section of the Qiangtang Basin (Tibet) contains information concerning the response of the eastern Tethys Ocean to multiple carbon cycle perturbations and to palaeoceanographic changes. Three positive δ¹³C excursions (P-CIE 1–3), dated as latest Callovian, middle Oxfordian and early Late Kimmeridgian, respectively, are observed in our section and related to high organic carbon burial episodes; they are correlatable with profiles from the Atlantic, western Tethys and western Paleo-Pacific regions. A significant decrease in δ¹³C values in our section in late Oxfordian to early Kimmeridgian times is attributed to the onset of upwelling of ¹³C-depleted watermasses caused by the opening of new seaways during the progressive collapse of Pangaea. A fourth positive δ¹³C excursions (P-CIE 4), dated as Late Kimmeridgian-Early Tithonian, is unlikely to be due to accelerated burial of organic carbon, but may be associated with the establishment of a stable low-latitude thermohaline circulation that replaced the upwelling zones. Due to the oceanic changes linked to the breakup of Pangaea, incursions of cold Arctic waters and associated changes in water mass density triggered a collapse in thermohaline circulation in the Tethys Ocean during the middle Early Tithonian (ca. ~151–150 Ma). As a consequence, an upwelling cold bottom current was formed, triggering global cooling and a significant reduction in the δ¹³C values. This study is the first to show continuous carbon isotope profiles for the eastern Tethys Ocean, and provides an inter-regional correlation and new paleoceanographic information.
... Carbon-isotope values from open marine strata (MA1-MA3) show only minor variability and range from 0.2 to 2.9‰ with median values of 1.8‰, 1.8‰ and 2.0‰, respectively, in accordance with Late Jurassic brachiopod-calibrated δ 13 C values from mid-latitudes (Prokoph et al., 2008) and Kimmeridgian-Tithonian pelagic bulk limestone signatures from the NW Tethys (Bartolini et al., 1996;Padden et al., 2002). However, the more restricted facies including peritidal and lagoonal facies (MA4-MA6) show a much broader scatter in δ 13 C and less positive median values of 0.7‰, 1.1‰ and −0.5‰, respectively (Fig. 5). ...
... The blue dashed boxes represent the interquartile of each dateset, and the lines within boxes show the median values. 1) Calculated δ 13 C data for mid-latitude ocean in Late Jurassic (Prokoph et al., 2008), 2) Kimmeridgian-Tithonian pelagic bulk limestones from NW Tethys (Bartolini et al., 1996;Padden et al., 2002). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) ...
... In the late Kimmeridgian, the different δ 13 C curves share important similarities in all three regions, including a δ 13 C increase followed by a decrease which extends into the Tithonian (Padden et al., 2002;Ruf et al., 2005;Colombié et al., 2011;Jach et al., 2014). A similar positive δ 13 C trend was also recognized in the Marlstone Member at Guppen, Switzerland (Weissert and Mohr, 1996), the Kimmeridge Clay of Dorset, UK (Morgans-Bell et al., 2001;Jenkyns et al., 2002), and the Trapanese domain in western Sicily (Cecca et al., 2001) and has been interpreted to reflect increased organic carbon burial. ...
Correlation of shallow-marine carbonate deposits with their coeval pelagic counterparts is often hampered by the lack of open-marine stratigraphic marker fossils and by the restrictions of regional biostratigraphic schemes. These difficulties can partly be overcome by the use of coupled δ¹³C and ⁸⁷Sr/⁸⁶Sr chemostratigraphy based on pristine shell calcite and bulk rock material. Here, a new high-resolution chemostratigraphic framework covering Kimmeridgian strata is presented based on three stratigraphic sections located in the Subboreal Lower Saxony Basin (LSB) of Northern Germany. Combined with sedimentological data, the bulk rock δ¹³C signal is critically evaluated for both diagenetic alteration and local environmental effects. In general, the δ¹³C signatures are considered to predominantly record the global marine signal. Diagenetic and facies-related discrepancies are restricted to dolomitic supratidal back ramp and intertidal back ramp deposits, respectively. Strontium-isotope stratigraphic data, obtained from diagenetically screened low-Mg calcite shells, refine the existing ostracod biostratigraphic scheme in the Lower Saxony Basin (LSB) and contribute to the existing global strontium-isotope dataset of the Kimmeridgian. These new results confirm the potential of well-preserved low-Mg calcite from shallow-marine settings to preserve a global marine Sr-isotope signal. Calibrated by the integrated biostratigraphic and strontium-isotope results, a high-resolution composite δ¹³C record for Kimmeridgian shoal-water deposits is established. Comparison of the new composite δ¹³C curve from the Subboreal Lower Saxony Basin (LSB) with existing Kimmeridgian records from the peri-Tethyan and Western Tethyan realms provides new insights into the long-term global carbon cycle during the Kimmeridgian.
... However, the particular sedimentological and palaeobiological features of the Middle-Upper Jurassic transition have been the subject of the interest of many researchers. Several detailed carbon isotope studies of marine carbonates and of marine and terrestrial organic matter have been carried out in the Callovian and Oxfordian from the western Tethys (e.g., Hoffman et al., 1991;Bill et al., 1995Bill et al., , 2011Bartolini et al., 1996;Jenkyns, 1996Jenkyns, , 2003Weissert and Mohr, 1996;Lavastre, 2002;Wierzbowski, 2002Wierzbowski, , 2004Wierzbowski et al., 2009;Dromart et al., 2003a;Padden et al., 2001Padden et al., , 2002Katz et al., 2005;Tremolada et al., 2006;Louis-Schmid et al., 2007a, b;Rais et al., 2007). Other studies have been carried out in Boreal/Subboreal areas (Pearce et al., 2005;Wierzbowski et al., 2006;Nunn et al., 2009;Rogov, 2010, 2011;Nunn and Price, 2010;Zheng et al., 2013), and in the Austral Ocean (Price and Gröcke, 2002). ...
... Deep burial cementation and recrystallization can result in the addition of isotopically depleted calcite to the bulk carbonate pool, shifting the bulk oxygen isotope towards lower values (e.g. Padden et al., 2002). The oxygen isotope values in this study are interpreted to be altered by burial diagenesis and, therefore, we consider these data as an unreliable proxy for palaeotemperature and/or palaeosalinity. ...
... However, during burial diagenesis, carbon isotope values are less prone to diagenetic alteration than oxygen isotope values (e.g. Marshall, 1992;Padden et al., 2002) because they are subject to a much smaller temperature-controlled fractionation. Our carbon isotope curves can be correlated with other European sections (Fig. 9), confirming the hypothesis that bulk carbonate curves record major perturbations of the carbon cycle on a global scale. ...
A bulk carbon-isotope stratigraphy, based on high-resolution sampling of five stratigraphic ammonite-dated sections from pelagic swells of the Subbetic basin (External Zones of the Betic Cordillera, southern Spain) is presented. The studied sections are characterized by Callovian–Oxfordian stratigraphic successions located in the South Iberian palaeomargin, a key area connecting the Central Atlantic to the Tethys oceans. The rocks are mainly nodular limestones with common extreme condensation (rosso ammonitico facies). Discontinuities with hiatuses of variable duration, submarine “hardgrounds” Fe-Mn ooids, limonite crusts, and neptunian dykes are observed around the Callovian/Oxfordian boundary. The stratigraphic record, although very time-averaged, allows for a consistent and accurate ammonite chronostratigraphy. The carbon isotopes of marine carbonates show a marked trend towards high δ¹³C values from Lower Oxfordian to the Middle Oxfordian (~4.3‰ near the Plicatilis/Transversarium boundary). The isotopic values stand between 2.7 and 3.0‰ at the Upper Oxfordian (Bifurcatus and Hypselum Zones) and lowermost Kimmeridgian (Bimammatum Zone); afterward δ¹³C values decrease and reach a relative minimum (~2.3–2.5‰) in the Lower Kimmeridgian (Bimammatum/Planula boundary). Finally, isotopic values increase again (~2.6–2.7‰) in the lower Kimmeridgian (mid part of the Planula Zone). Comparison of carbon-isotope stratigraphy between Subbetic and other Tethyan areas shows similar trends. The replacement of thin-shelled bivalves by planktonic foraminifers and radiolarians that took place in the Callovian/Oxfordian boundary can be associated to the widening of the trans-Pangaean seaway. This, in turn, triggered the global warming which increased nutrients concentration in upper water column due to intensified nutrient input by river plumes. These phenomena are concomitant with the major Oxfordian δ¹³C positive excursion and with a transgressive cycle.
... The stable oxygen and carbon isotope bulk carbonate compositions of samples from the studied section are affected by deep burial diagenesis (Schlanger and Douglas, 1974;Stoll and Schrag, 2000;Padden et al., 2002). In an alpine study, Padden et al. (2002) isotopically depleted calcite to the bulk carbonate pool, shifting the bulk oxygen isotope value towards lower numbers. ...
... The stable oxygen and carbon isotope bulk carbonate compositions of samples from the studied section are affected by deep burial diagenesis (Schlanger and Douglas, 1974;Stoll and Schrag, 2000;Padden et al., 2002). In an alpine study, Padden et al. (2002) isotopically depleted calcite to the bulk carbonate pool, shifting the bulk oxygen isotope value towards lower numbers. Analogous to conditions in alpine tectonic settings, we interpret the oxygen isotope values in this study as the result of deep burial diagenesis. ...
... Carbon isotope values are less prone to diagenetic alteration than oxygen isotope values during burial diagenesis (Hudson, 1977;Weissert, 1989;Banner and Hanson, 1990;Marshall, 1992;Padden et al., 2002) because they are subject to a much smaller temperaturecontrolled fractionation effect in a rock-dominated environment. Mudstones, marlstones, and calcareous shales are suitable for carbon isotopic analysis, which has been shown in numerous studies over the past several decades (e.g., Weissert and Channell, 1989;Padden et al., 2002;Herrle et al., 2004;Jarvis et al., 2006;Wendler, 2013). ...
During the Albian and Cenomanian, the Earth underwent profound climatic and oceanographic changes that were recorded in sedimentary successions on a global scale. Carbon isotope records spanning this time interval have been established in the western Tethys, eastern Pacific and North Atlantic Oceans, but not yet in the eastern Tethys Ocean. In this paper, we present biostratigraphic, chemostratigraphic and cyclostratigraphic characteristics of the uppermost Albian–lowermost Cenomanian in an eastern Tethyan section (Youxia, southern Tibet). Based on calcareous nannofossil biozones and the bulk rock δ¹³C curve, the Albian-Cenomanian boundary interval (ACBI) was identified and correlated to the western Tethys and Atlantic Oceans. In the Youxia section, δ¹³C values range from approximately 0‰ to +1.3‰ (−0.03‰ to +1.31‰). Four subevents (a, b, c and d) were distinguished in the ACBI carbon isotope curve via correlation with other sections. Based on a spectral analysis of the carbonate content, we recognized Milankovitch short eccentricity (~100 kyr) and precession (22.2 kyr) cycles, suggesting that orbital variations modulated depositional processes. The duration of the ACBI was estimated at ~311 kyr, while OAE 1d lasted for ~233 kyr in the eastern Tethys Ocean, consistent with the duration calculated from Atlantic Ocean records.
... The δ 13 C isotope data on the Tethys realm, which were mainly derived from car-LITHOLOGY AND MINERAL RESOURCES Vol. 52 No. 6 2017 RUD'KO et al. bonate rock samples (Padden et al., 2002;Žák et al., 2012), characterize so far only the western passive margin of the Tethys. Replenishment of the isotope information and extension of the possibility of detailed correlation within the Upper Jurassic stratigraphic interval need a systematic study of δ 13 C in the carbonate sediments of other Late Jurassic Tethyan marginal seas. ...
... Thus, we obtained new data on the sedimentation setting and postsedimentary transformations in the Crimean carbonate platform. Based on the SIS correlation of the studied sections, we compiled temporal δ 13 C variation plot that was compared with analogous plots for the western margin of the Tethys Ocean (Padden et al., 2002;Coimbra et al., 2009;Michalik et al., 2009;Žák et al., 2012). ...
... Among Upper Jurassic rocks with known δ 13 С values, the Crimean carbonate platform deposits are characterized by the heaviest carbon isotope composition. The δ 13 С values obtained for limestones in our work are 0.5-1‰ higher than for carbonate sediments from the western Tethys (Padden et al., 2002;Coimbra et al., 2009;Michalik et al., 2009;Žák et al., 2012). In addition, the values obtained for belemnite rostra are 1.5‰ higher than in the Subboreal and Boreal belemnites (Nunn and Price, 2010). ...
The paper presents the results of study of the Sr, C, and O isotope compositions in Upper Jurassic carbonate rocks of the Baidar Valley and Demerdzhi Plateau in the Crimean Mountains represented by different facies of the carbonate platform at the northern active margin of the Tethys. The ⁸⁷Sr/⁸⁶Sr value in them varies from 0.70699 to 0.70728. Based on the Sr chemostratigraphic correlation, the age of massive and layered limestones in the western part of the Ai-Petri and Baidar yailas (pastures) is estimated as late Kimmeridgian–early Tithonian, whereas the age of flyschoids of the Baidar Valley are estimated as late Tithonian–early Berriasian. The nearly synchronous formation of carbonate breccias of the Baidar Valley and Demerdzhi Plateau in late Tithonian–early Berriasian is substantiated. A summary section of Upper Jurassic rocks is compiled based on the Sr chemostratigraphic data. It has been established that δ¹⁸O values in the studied carbonate sediments vary from–2.9 to 1.3‰ (V-PDB). At the same time, shallow-water sediments in the internal part and the edge of the Crimean carbonate platform are depleted in ¹⁸O (–2.9 to +0.1‰) relative to sediments on the slope and foothill (–0.5 to +1.3‰). It is demonstrated that δ¹³C values do not depend on the facies properties and decrease in younger carbonate sediments from 3–3.5‰ to 1–1.5‰ in line with the Late Jurassic general trend. The δ¹³C values obtained for the Crimean carbonate platform turned out to be 0.5–1‰ higher than the values typical of the deep-water marine setting at the western margin of the Tethys. These discrepancies are likely related to peculiarities of water circulation and high bioproductivity in marine waters of the northern Peri-Tethys.
... Вариации δ 13 C в течение поздней юры хорошо изучены, в первую очередь, по данным изотопного состава ростров белемнитов суббореальных [Nunn, Price, 2010;Wierzbowski et al., 2013] и бореальных [Žák et al., 2012;Dzyuba et al., 2013] регионов. Изотопные данные по δ 13 C для Тетической области были получены, в основном по пробам карбонатных пород [Padden et al., 2002;Žák et al., 2012] и характеризуют пока только западную пассивную окраину Тетиса. Для пополнения изотопной информации и расширения возможностей детальной корреляции в пределах верхнеюрского стратиграфического интервала, необходимо систематическое изучение δ 13 C в карбонатных осадках других позднеюрских окраинных морей Тетиса. ...
... В районах БК и ПД впервые изучен изотопный состав С и О в известняках и раковинах моллюсков, в связи с этим получены новые данные об обстановках осадконакопления и постседиментационных преобразованиях отложений Крымской карбонатной платформы. На основе SIS-корреляции изученных разрезов построена кривая временных вариаций δ 13 C, она была сопоставлена с аналогичными кривыми для западной окраины океана Тетис [Padden et al., 2002;Coimbra et al., 2009;Мichalik et al., 2009;Žák et al., 2012]. Рис. 1. Cхема расположения районов изучения верхнеюрских отложений на Крымском полуострове. ...
... Среди верхнеюрских отложений с известным δ 13 С отложения Крымской карбонатной платформы характеризуются наиболее тяжелым изотопным составом углерода. Измеренные нами в известняках значения δ 13 С на 0.5-1‰ выше полученных для карбонатных пород западной части Тетиса [Padden et al., 2002;Coimbra et al., 2009; Мichalik [Nunn, Price, 2010]. Более тяжелый, по сравнению с отложениями западной окраины Тетиса, изотопный состав С в отложениях Крымской карбонатной платформы требует объяснения. ...
Изучен изотопный состав Sr, C и О в верхнеюрских карбонатных отложениях Байдарской котловины
и плато Демерджи Горного Крыма, представленных различными фациями карбонатной платформы
северной активной окраины Тетиса. Величина 87Sr/ 86Sr в них варьирует от 0.70699 до 0.70728. В ре-
зультате Sr-хемостратиграфической корреляции возраст массивных и слоистых известняков западной
части Ай-Петринской и Байдарской яйл определен как соответствующий позднему кимериджу – ран-
нему титону, а флишоидов Байдарской котловины – позднему титону – раннему берриасу. Обоснова-
но субсинхронное формирование известняковых брекчий Байдарской котловины и плато Демерджи
в позднем титоне – раннем берриасе. Составлен сводный разрез верхнеюрских отложений по данным
Sr-хемостратиграфии.
Установлено, что значения δ18O в изученных карбонатных отложениях варьируют от −2.9 до 1.3‰
(V-PDB), при этом мелководные отложения внутренней части и бровки Крымской карбонатной
платформы обеднены 18O (−2.9 – +0.1‰) по сравнению с отложениями ее склона и подножья
(−0.5 – +1.3‰). Показано, что значения δ13C не зависят от фациальных особенностей и уменьшают-
ся (от 3–3.5‰ до 1–1.5‰) по мере омоложения возраста карбонатных отложений, что соответствует
общему тренду позднеюрского времени. Значения δ13C, полученные для Крымской карбонатной плат-
формы, оказались выше (на 0.5–1‰) значений, характерных для глубоководных морских обстановок
западной окраины Тетиса. Предполагается, что эти различия обусловлены особенностями водной
циркуляции и повышенной биопродуктивностью морских акваторий Северного Перитетиса.
... The Middle-Upper Oxfordian positive excursion of the δ 13 C is recorded in the bulk carbonates and belemnite rostra of the Stankowa Skała outcrop (Fig. 5). This mid-Oxfordian positive δ 13 C shift has been also reported by numerous researchers (e.g., Jenkyns, 1996;Weissert and Mohr, 1996;Bartolini et al., 1995Bartolini et al., , 1999Cecca et al., 2001;Morettini et al., 2002;Padden et al., 2002;Wierzbowski, 2002Wierzbowski, , 2004Pearce et al., 2005;Louis-Schmid et al., 2007;Wierzbowski et al., 2013;Jach et al., 2014). ...
... The Upper Oxfordian-Lower Tithonian decrease in δ 13 C values of both bulk carbonates and belemnite rostra is also noted in the published carbon isotope records of the Western Tethys and peri-Tethyan basins (Weissert and Mohr, 1996;Bartolini et al., 1999;Cecca et al., 2001;Padden et al., 2002;Jenkyns et al., 2002;Weissert and Erba, 2004;Coimbra et al., 2009;Jach et al., 2014). However, the trigger for the declining δ 13 C values is not evident. ...
... However, the trigger for the declining δ 13 C values is not evident. Some authors suggest an enhanced erosion or continental weathering and subsequent riverine influx of 12 C to the global ocean (e.g., Padden et al., 2002;Price and Gröcke, 2002;Gröcke et al., 2003;Nunn and Price, 2010). Others indicate a decreasing organic and carbonate carbon burial ratio (e.g., Weissert and Mohr, 1996;Weissert and Erba, 2004) or a possibility of upwelling of cooler oceanic water enriched in 12 C (Gröcke et al., 2003). ...
... As a con se quence, the car bon iso to pic re cord is less sus cep ti ble to al ter ation by burial diagenesis than the ox y gen re cord (e.g., Ban ner and Hanson, 1990;Mar shall, 1992). Usu ally, the rock-fluid alter ation dur ing diagenesis re sults in a de crease of d 18 O values, whereas diagenetic mod i fi ca tion of d 13 C val ues may re main in sig nif i cant (e.g., Mar shall, 1992;Padden et al., 2002;Bojanowski et al., 2014). ...
... (6) Above the Late Callovian pos i tive d 13 C ex cur sion, the curves in all the sec tions show a steadily de creas ing trend (num ber 6 in Fig. 15; UAZs 9-11 in sam ple Dsr191 in Figs 3, 6-8). It is com pa ra ble to the gen eral pat tern, recorded in sev eral curves for the West ern Tethyan re gion (Pisera et al., 1992;Weissert and Mohr, 1996;Cecca et al., 2001;Padden et al., 2002;Weissert and Erba, 2004;Coimbra et al., 2009). This de creas ing trend is re garded as the most char ac ter is tic fea ture of the Late Ju ras sic d 13 C curves. ...
... In all these sec tions in creased val ues oc cur in the low er most part of the var ie gated radiolarites, which are dated as Mid dle-Late Oxfordian by means of radiolarian data (Polák et al., 1998, UAZ 9 in the sam ples GU-10, GU-11). It is plau si ble that the shift men tioned above (number 7 in Fig. 15) re flects the Mid dle Oxfordian ex cur sion, re corded in sev eral d 13 C curves (e.g., Jenkyns, 1996;Weissert and Mohr, 1996;Bartolini et al., 1995Morettini et al., 2002;Padden et al., 2002;Rey and Delgado, 2002;Wierzbowski, 2002;Pearce et al., 2005;Rais et al., 2007;Coimbra et al., 2009). ...
Middle–Upper Jurassic pelagic carbonates and radiolarites were studied in the Krížna Nappe of the Tatra Mountains (Central Western Carpathians, southern Poland and northern Slovakia). A carbon isotope stratigraphy of these deposits was combined with biostratigraphy, based on radiolarians, calcareous dinoflagellates and calpionellids. In the High Tatra and Belianske Tatra Mountains, the Bajocian and part of the Bathonian are
represented by a thick succession of spot ted lime stones and grey nodular limestones, while in the Western Tatra Mountains by relatively thin Bositra-crinoidal limestones. These deposits are referable to a deeper basin and a pelagic carbonate platform, respectively. The various carbonate facies are followed by deep-water biosiliceous facies, namely radiolarites and radiolarian-bearing limestones of Late Bathonian–early Late Kimmeridgian age. These fa cies pass into Upper Kimmeridgian–Lower Tithonian pelagic carbonates with abundant Saccocoma sp. The bulk-carbonate isotope composition of the carbonate-siliceous deposits shows positive and negative δ13C
excursions and shifts in the Early Bajocian, Late Bajocian, Early Bathonian, Late Bathonian, Late Callovian, Middle Oxfordian and Late Kimmeridgian. Additionally, the δ13C curves studied show a pronounced increasing trend in the Callovian and a steadily decreasing trend in the Oxfordian–Early Tithonian. These correlate with the trends known from the Tethyan region. The onset of Late Bathonian radiolarite sedimentation is marked by a decreasing trend in δ13 C. In creased δ13C values in the Late Callovian, Middle Oxfordian and Late Kimmeridgian (Moluccana Zone) correspond with enhanced radiolarian production. A significant increase in CaCO3 content is re corded just above the Late Callovian δ13C excursion, which coincides with a transition from green to variegated radiolarites.
... The Late Jurassic carbon isotope stratigraphy is marked by a positive carbon isotope excursion of ∼3‰ which has been dated as Middle Oxfordian in age [1]. This excursion has been identified in marine and terrestrial carbon isotope records from the western and northern Tethys and the Atlantic [1][2][3][4][5][6][7][8][9]. ...
... The Late Jurassic carbon isotope stratigraphy is marked by a positive carbon isotope excursion of ∼3‰ which has been dated as Middle Oxfordian in age [1]. This excursion has been identified in marine and terrestrial carbon isotope records from the western and northern Tethys and the Atlantic [1][2][3][4][5][6][7][8][9]. δ 13 C of marine carbonate (δ 13 C carb ) increased in several steps during the Early and the Middle Oxfordian, culminating in a distinct shift of 1‰ within few 10 5 yr at the end of the plicatilis ammonite zone. ...
... The decreasing part is dated to be of middle transversarium zone age, i.e., it is in a stratigraphically higher position than the negative shift in the δ 13 C org -record of our composite section. However, because of lacking biostratigraphical information, it was only assumed that the lower part of the section lies within the transversarium zone [1]. Based on lithological and δ 13 C carb -correlation, it is likely that the lower part actually comprises parts of the plicatilis zone. ...
The transition from the Middle to the Late Jurassic was characterized by
significant changes in oceanography and climate and by changes in global
carbon cycle as shown in the C-isotope record. A prominent mid-Oxfordian
positive excursion in bulk carbonate carbon isotope values (
δ13C carb) with an amplitude of more than
1‰ has been documented from many sections in the Northern Tethys
realm. In this study we present new bulk organic matter C-isotope data (
δ13C org) from northwestern Tethys that do
not record the mid-Oxfordian positive excursion in carbonate carbon. On
the contrary, δ13C org decreases during the
interval of the most rapid increase in δ13C
carb. We demonstrate that this decrease is not due to a
changing marine-terrestrial organic carbon partitioning but that the
contrasting isotope trends record peculiar environmental and climate
changes which occurred near the beginning of the Late Jurassic. Using a
simple carbon cycle model we show that an increase in atmospheric pCO
2 starting at modern levels could be the cause of contrasting
trends in δ13C carb and
δ13C org. We suggest that a reorganisation
of ocean currents related to the opening and/or widening of the
Tethys-Atlantic-Pacific seaway, and a massive spread of shallow-sea
carbonate production led to higher pCO 2. Model simulations
indicate that this increase in pCO 2 may have triggered
changes in the biological carbon pump and in organic carbon burial that
can explain the Middle Oxfordian C-isotope record.
... The break-up of Pangea from the Late Jurassic substantially influenced the global ocean circulation, and the expanded seaways between broken continents induced a humid climate along coastal areas (Weissert & Mohr 1996). Carbon isotope stratigraphies suggest that changes in the ocean circulation induced an extensive methane release and a global warming during the mid-Oxfordian (Padden et al. 2001(Padden et al. , 2002Louis-Schmid et al. 2007a,b). The circulation of carbon accelerated under an expanded humid climate raised temperature, and high atmospheric CO 2 . ...
... Another potential tool for age determination is carbon isotope stratigraphy, which has been applied for inter-regional correlation (e.g. Padden et al. 2002;Wissler et al. 2003;Louis-Schmid et al. 2007a;Ludvigson et al. 2010;Alexandre et al. 2011;Huck et al. 2011;Najarro et al. 2011;Hasegawa et al. 2012;Stein et al. 2012;Kakizaki et al. 2013). In this study, we firstly improve the carbon isotope stratigraphy of the Torinosu-type limestone for a period of ca. 9 myr from the late Kimmeridgian (Late Jurassic) to the early Berriasian (Early Cretaceous). ...
... The overlying section exposes an alternation of bioclastic pack/wackestone and oncoidal pack/ (Leinfelder et al. 2002). Location of the Montsalvens section (yellow star), and the Xausa and Frisoni sections (red star) are also shown for discussion (Padden et al. 2002). Please note that the Xausa and Frisoni sections appear to be at the same position on this scale; (b) Distribution of the Torinosu-type limestone and location of the study area, with the tectonic divisions of the Japanese Islands. ...
Carbon isotope stratigraphy of the Late Jurassic and earliest Cretaceous was revealed from Torinosu-type limestone, which was deposited in a shallow-marine setting in the western Paleo-Pacific, in Japan. Two sections were examined; the Nakanosawa section of the late Kimmeridgian to early Tithonian age (Fukushima Prefecture, Northeast Japan), and the Furuichi section of the late Kimmeridgian to early Berriasian age (Ehime Prefecture, Southwest Japan). The age-model was established using Sr isotope ratio and fossil occurrence. The limestone samples have a low Mn/Sr ratio (mostly <0.5) and lack a distinct correlation between δ13C and δ18O, indicating a low degree of diagenetic alteration. Our composite δ13C profile from the two limestone sections shows three stratigraphic correlation points that can be correlated with the profiles of relevant ages from the Alpine Tethyan region: a large-amplitude fluctuation (the lower upper Kimmeridgian, ∼152 Ma), a positive anomaly (above the Kimmeridgian/Tithonian boundary, ∼150 Ma), and a negative anomaly (the upper lower Tithonian, ∼148 Ma). In addition, we found that δ13C values of the Torinosu-type limestone are ∼1‰ lower than the Tethyan values in the late Kimmeridgian. This inter-regional difference in δ13C values is likely to have resulted from a higher productivity and/or an organic burial in the Tethyan region. The difference gradually reduces and disappears in the late Tithonian, where the Tethyan and our δ13C records show similar stable values of 1.5–2.0‰. This isotopic homogenization is probably due to changes in the continental distribution and the global ocean circulation, which propagated the 13C-depleted signature from the larger Paleo-Pacific to the smaller Tethys Ocean during this time.
... The stratigraphy and palaeontology of Upper Jurassic limestones have been studied in the Tethys Region, and subsequent studies during the last decade have demonstrated that chemostratigraphy based on carbon isotope geochemistry is a valuable stratigraphic tool (e.g. Padden et al., 2001Padden et al., , 2002Louis-Schmid et al., 2007a,b,c;Rais et al., 2007). These Tethyan studies outlined how high d 13 C values corresponded to accelerated carbon cycling with elevated organic carbon burial rates and probably elevated atmospheric pCO 2 levels (e.g. ...
... Outline of Southeast Asia refers to Metcalfe (2011). Locations of Switzerland (white star; Padden et al., 2002), Scotland (black star; Nunn et al., 2009;Nunn and Price, 2010) and Russian platform (doubled diamond; Podlaha et al., 1998;Price and Rogov, 2009) are also shown for discussion. (B) Map of Borneo Island. ...
... For comparison with d 13 C stratigraphy of the SSF section (Fig. 8), we have selected two Upper Jurassic sections reported from Switzerland by Padden et al. (2002); the Gemmi pass and Montsalvens sections, both of which were formed along the continental margin of the northwestern Tethys (their locations are shown in Fig. 1A). These two sections, consisting of pelagic and hemipelagic carbonates, represent relatively high resolution data, and the d 13 C profiles of bulk carbonate are regarded as representative Tethyan d 13 C records (Weissert and Erba, 2004;Weissert et al., 2008). ...
... Diagenetic alteration, including dissolution and post-depositional diagenesis, have a large influence on the isotopic composition, elemental composition, and calcareous nannofossil assemblages preserved in marine sediments, and thus can significantly alter their utility as paleoenvironmental indicators for paleoceanographic conditions (Roth and Krumbach, 1986;Padden et al., 2002;Bruno et al., 2020). ...
... Several studies suggested that when the relative abundance of Watznaueria barnesiae exceeds 40%, the assemblage is strongly influenced by diagenesis and no longer reflects the original nannofossil assemblage (Roth and Krumbach, 1986;Padden et al., 2002;Bruno et al., 2020). Accordingly, it appears that a majority of the studied samples from the Kangsha section have experienced a certain degree of diagenetic alteration, especially for the underlying Interval I (OAE1b interval, with average W. barnesiae abundance exceeding 72%), which is consistent with the observation that the overlying Interval II has betterpreserved nannofossil assemblages and increased WSI values (Fig. 5A). ...
Lower Cretaceous marine strata are widely distributed and well exposed in the Tingri area of Southern Tibet, which includes the Gucuocun and the overlying Gambacunkou Formations. However, the age of the boundary between these two lithologic formations is poorly constrained due to a scarcity of macrofossils. A detailed biostratigraphic study was carried out on the abundant, moderately preserved calcareous nannofossil assemblages obtained from the lower part of the Gambacunkou Formation and the underlying Gucuocun Formation in the Kangsha Section, Tingri. The first occurrence of the marker species Tranolithus orionatus (110.73 Ma) constrains the Gucuocun/Gambacunkou boundary to slightly below the lower boundary of Subzone NC8c (early Albian age), which correlates with Ocean Anoxic Event (OAE) 1b. The absence of Axopodorhabdus albianus and Eiffellithus turriseiffelii throughout the section suggests that the lower part of Gambacunkou Formation mostly falls within nannofossil Subzone NC8c (110.73–109.94 Ma; early Albian), with a mean sedimentation rate of 12.7 cm/kyr, which is higher than that typical of the open ocean. The consistently high total organic carbon (TOC) and CaCO3 contents in Interval I (Gucuocun Fm.) indicate that productivity was higher during OAE1b, possibly due to increased terrigenous input (as evidenced by elevated C/N and nutrient/fertility indices) that carried nutrients to promote productivity during this event. Nannofossil assemblages and geochemical proxies, including TOC and elemental ratios (Ti/Al, Zr/Al, K/Al), reveal a parallel upsection increase in surface water fertility and continental weathering intensity from Interval II-1 (0–60 m) to the overlying Interval II-2 (60–102 m) in the Gambacunkou Fm., suggesting that enhanced continental weathering contributed to increase the surface water fertility and dilute the sediment carbonate content. These data also indicate that the depositional environment in the Tingri area was aerobic to hypoxic during the early Albian. Our result confirms the presence of OAE1b at the top of the Gucuocun Formation.
... As with modern and other ancient carbonate systems, diagenetic alteration that is commonly observed in fine-grained carbonate sedimentary rocks remains a concern when interpreting δ 13 C values (Swart, 2015 and references therein). Deep burial cementation and recrystallization can result in the addition of isotopically depleted calcite to the bulk carbonate pool, shifting the bulk δ 18 O towards lower values (Padden et al., 2002). However, during burial diagenesis, δ 13 C values are less prone to diagenetic alteration than oxygen isotope values (Marshall, 1992;Padden et al., 2002) as the carbon isotope system is rock-dominated and the δ 13 C values are not significantly influenced by temperature. ...
... Deep burial cementation and recrystallization can result in the addition of isotopically depleted calcite to the bulk carbonate pool, shifting the bulk δ 18 O towards lower values (Padden et al., 2002). However, during burial diagenesis, δ 13 C values are less prone to diagenetic alteration than oxygen isotope values (Marshall, 1992;Padden et al., 2002) as the carbon isotope system is rock-dominated and the δ 13 C values are not significantly influenced by temperature. Therefore, to ascertain the possible global significance of measured changes in δ 13 C carb , diagenetic or local lithological influences must first be accounted for. ...
A stable carbon isotope (δ¹³C) profile of the Early Cretaceous to Paleogene (Berriasian – Danian) was generated from ditch-cuttings material recovered from well 30/2a-7, Central North Sea. The profile of δ¹³C values was integrated with calcareous nannofossil biostratigraphy and sequence stratigraphy from the Cromer Knoll Group to provide an integrated stratigraphic framework for the Early Cretaceous. Although, nannofossil data was not collected from most of the overlying Chalk Group, the associated δ¹³C profile was sufficiently resolved to correlate with other similar δ¹³C records from both the Boreal and Tethyan Realms. The δ¹³C profiles and nannofossil data from well 30/2a-7 were stacked with the nearby Shearwater A9 well data to create a composite section that provides a long-term near continuous record of the Early Cretaceous to Paleogene from the basinal deposits of the Central North Sea. Sequence stratigraphic analyses was conducted to provide an integrated bio-chemo-sequence stratigraphic framework for regional correlation. Several major globally recognized δ¹³C events that are recognized in the wells are seismically resolvable and can be correlated regionally across the Central North Sea, providing a chronostratigraphic framework for constraining hydrocarbon play elements for both exploration, production and carbon capture and storage projects.
... Interestingly, the bulk sediment samples display an overall decreasing trend in their δ 13 C values throughout the Late Jurassic, which is typical for the inorganic carbon curve with maximal δ 13 C values in the Gregoryceras transversarium Zone (Middle Oxfordian) (Jenkyns et al. 2002;Padden et al. 2002;Coimbra et al. 2014;O'Dogherty et al. 2018). In the present study, the bulk sediment samples from the Gregoryceras transversarium Zone show δ 13 C values as high as 2.9‰. ...
... In the present study, the bulk sediment samples from the Gregoryceras transversarium Zone show δ 13 C values as high as 2.9‰. Despite lower bulk sediment values recorded from the Late Oxfordian causing the curve to be slightly noisy, the maximum δ 13 C value from the Middle Oxfordian and the decreasing trend in δ 13 C values towards the end of the Jurassic are comparable to previously published data from around the western Tethys ocean in Spain, France, Switzerland, and Italy (Jenkyns 1996;Weissert and Mohr 1996;Jenkyns et al. 2002;Padden et al. 2002;Coimbra et al. 2014;O'Dogherty et al. 2018). ...
This study presents the first record of stable carbon and oxygen isotopes of well-preserved belemnites and bulk sediment from the Upper Jurassic pelagic carbonates of the Ouarsenis Mountains (northwestern Algeria), which were deposited at the southern margin of the Tethys ocean. Cathodoluminescence and scanning electron microscopy was used to eliminate potentially diagenetically altered specimens (brachiopods, aptychi, and some belemnites). Ultimately, 55 belemnite specimens were used to reconstruct water temperatures for the Middle Oxfordian to the Early Tithonian. Their δ18Ocarb values ranged from −0.35‰ to −3.88‰, suggesting warm and mostly stable temperature conditions during the Late Jurassic. Using a δ18Osea value of 0‰ for the tropical palaeolatitude of 15–20°N, the δ18Ocarb values of the well-preserved belemnite rostra translate into average temperatures of 27.8 °C in the Middle Oxfordian (Gregoryceras transversarium Zone), 27.0 to 27.5 °C in the Late Oxfordian (Epipeltoceras bimmamatum and Idoceras planula zones, respectively), 26.2 °C in the Early Kimmeridgian, and 27.3 °C in the Early Tithonian (Hybonoticeras hybonotum Zone).
... Jurassic: The Jurassic δ 13 C composite shown in Figure 11.11 is from Bartolini et al. (2013), Grabowski et al. (2019), Hesselbo et al. (2007), Katz et al. (2005), Louis-Schmid (2006), Louis-Schmid et al. (2007), Mercuzot et al. (2020), O'Dogherty et al. (2006, Oliveira et al. (2006), Padden et al. (2002, Pellenard et al. (2014aPellenard et al. ( , 2014b, Rais et al. (2007), Sandoval et al. (2008Sandoval et al. ( , 2012, Silva et al. (2011), Sucheras-Marx et al. (2013, and Weissert and Channell (1989). Two major positive δ 13 C excursions dominate the record, one at the base of the Jurassic (Planorbis Event, >+5‰), and the other within the early Toarcian (Toarcian Oceanic Anoxic Event, TOAE, >+4‰). ...
... Lomagundi-Jatuli Schröder et al. 2008 Shunga-Francevillian Zhong and Ma 1997Bekker et al. 2005Bekker et al. 2006Lindsay and Brasier 2002Melezhik et al. 1999Planavsky et al. 2012Kump et al. 2011Bekker et al. 2016Hodgskiss et al. 2019Whittaker et al. 1998Wilson et al. 2010 Brasier and Lindsay 1998Zhang et al. 2018Guo et al. 2013Semikhatov et al. 2009Frank et al. 2003Bartley et al. 2007Kah et al. 2012Kah et al. 1999Knoll et al. 1995Cox et al. 2016Kuznetsov et al. 2006Halverson 2006 Cramer & Jarvis GTS2020 FIGURE 11.2 Neoproterozoic AGE (Ma) Period Payne et al. 2004, Xie et al. 2007, Burgess et al. 2014 Tierney 2010 Cramer & Jarvis GTS2020 FIGURE 11.9 Preto et al. 2013Muttoni et al. 2014Muttoni et al. 2004Mazza et al. 2010Sun et al. 2016Korte et al. 2017, Bachan et al. 2012, van de Schootbrugge et al. 2008 Cramer & Jarvis GTS2020 FIGURE 11.10 Katz et al. 2005Mercuzot et al. 2020Silva et al. 2011, Oliviera et al. 2006Hesselbo et al. 2007Sandoval et al. 2008Suchéras-Marx et al. 2013O'Doherty et al. 2006Bartolini et al. 2013Pellenard et al. 2014Louis-Schmid 2006Louis-Schmid et al. 2007Rais et al. 2007Padden et al. 2002Grabowski et al. 2019 Cramer & Jarvis GTS2020 FIGURE 11.11 Cretaceous Early Late AGE (Ma) Grabowski et al. 2017Spovieri et al. 2006, Lini 1994, Garcia 2008, Emmanuel and Renard 1993Li et al. 2016Herrle et al. 2004Gale et al. 2011Mitchell et al. 1996Paul et al. 1994Jenkyns et al. 1994Jarvis et al. 2001Paul et al. 1999Jarvis et al. 2006Jenkyns et al. 1994Jarvis et al. 2006Thibault et al. 2016Linnert et al. 2018Voigt et al. 2010Thibault et al. 2012Schovsbo et al. 2008 ...
The ¹³C/¹²C value of dissolved inorganic carbon (DIC) in the ocean has varied through time and can be determined from the marine carbonate record as changes in δ¹³Ccarb. These variations provide insight into global carbon cycle dynamics, as well as relative age information (chronostratigraphy) that can be used to correlate sedimentary successions globally. The global carbon cycle includes both short- and long-term components, and their interactions dominate the isotopic record presented in this chapter. The partitioning and sequestration of carbon between organic and carbonate rock reservoirs, and their fluxes to and from the ocean–atmosphere–biosphere system, drive secular changes in the δ¹³C of DIC in the oceans that are ultimately recovered from the stratigraphic record. The pre-Cenozoic data presented here utilize bulk carbonate data for compilation, but a wide range of materials has been analyzed in the literature to produce previous composites. Care must be taken to consider what materials have been analyzed in comparing global carbon isotope records from the literature.
... However, as with modern and other ancient carbonate systems, diagenetic alteration that is commonly observed in fine-grained carbonate sedimentary rocks remains a concern when interpreting δ 13 C and δ 18 O values (Swart, 2015 and references therein). Deep burial cementation and recrystallization can result in the addition of isotopically depleted calcite to the bulk carbonate pool, shifting the bulk oxygen isotope towards lower values (Padden et al., 2002). However, during burial diagenesis, carbon isotope values are less prone to diagenetic alteration than oxygen isotope values (Marshall, 1992;Padden et al., 2002) as the carbon isotope system is rock-dominated and the δ 13 C values are not significantly influenced by temperature. ...
... Deep burial cementation and recrystallization can result in the addition of isotopically depleted calcite to the bulk carbonate pool, shifting the bulk oxygen isotope towards lower values (Padden et al., 2002). However, during burial diagenesis, carbon isotope values are less prone to diagenetic alteration than oxygen isotope values (Marshall, 1992;Padden et al., 2002) as the carbon isotope system is rock-dominated and the δ 13 C values are not significantly influenced by temperature. In order to ascertain the possible global significance of the measured changes in the δ 13 C values, diagenetic or local lithological influences on the records must first be accounted for and if possible excluded. ...
A highly resolved record of stable carbon isotope values (δ13C) of the Late Cretaceous to Palaeogene (Cenomanian – Danian) was generated from ditch-cuttings material recovered from the Shearwater A9 hydrocarbon production well, Shearwater Field, Central North Sea. The profile of δ13C values was integrated with calcareous nannofossil and foraminifera biostratigraphy to provide an integrated stratigraphy for the Late Cretaceous Chalk Group. Detailed correlation between Shearwater A9 carbon isotope stratigraphy and associated biostratigraphic events with other similar records from both the Boreal and Tethyan Realms, including several proposed and/or ratified Global Boundary Stratotype Sections and Points had enabled the identification of major Stage and sub-Stage boundaries. This study provides a long-term and near-continuous stratigraphic record of the Late Cretaceous and earliest Palaeogene from more basinal facies of the Central North Sea. The record is punctuated with several short duration hiatal intervals, and a longer hiatus is identified whereby most of the Cenomanian is missing at this location.
... A significant positive correlation between δ 18 O and δ 13 C may indicate a diagenetic imprint on both values as this phenomenon is observed in rocks affected strongly by deep burial or meteoric diagenesis (cf. Jenkyns and Clayton, 1986;Marshall, 1992;Padden et al., 2002;Jach et al., 2014). ...
... The decline is observed in both bulk carbonate and belemnite carbon isotope records of various Tethyan and Boreal sections (cf. Weissert and Channell, 1989;Skourtsis-Coroneou and Solakius, 1999;Cecca et al., 2001;Padden et al., 2002;Tremolada et al., 2006;Price and Rogov, 2009;Grabowski et al., 2010b;Nunn and Price, 2010;Fig. 10. ...
New biostratigraphical, chemical and stable isotope (C, O) data are presented from the Lókút section (Transdanubian Range, Hungary) representing a ca. 13 m thick continuous succession of Lower Tithonian–Lower Berriasian pelagic limestones. The study is conducted to verify timing of nannofossil events and major palaeoenvironmental changes at the Jurassic/Cretaceous transition including lithogenic input, palaeoredox and palaeoproductivity variations. Nannofossil zones from NJT 16b to NKT have been identified in the Lókút section and correlated with magnetostratigraphy, covering an interval from polarity zone M21r to M18r. The nannofossil Zone NJT 16b spans the interval from the upper part of M21r to lowermost part of M19n2n but its lower limit is poorly defined due to large diachronism in first occurrence (FO) of Nannoconus infans in various Tethyan sections. FOs of N. kamptneri minor and N. steinmannii minor are situated in the topmost part of the M19n2n and lowermost part of M19n1r magnetozones, respectively. They are located ca. 2–2.5 m above the J/K boundary defined as Intermedia/Alpina subzonal boundary, which falls within the lower half of magnetozone M19n2n. The position of first occurrences of these taxa is similar to that from the Puerto Escaño section (southern Spain) and slightly lower than in Italian sections (Southern Alps). Concentrations of chemical element proxies of terrigenous transport (Al, K, Rb, Th) decrease towards the top of the Lókút section, which suggests a decrease in input of terrigenous material and increasing carbonate productivity during the Early Tithonian and the Berriasian. Slight oxygen depletion at the sea bottom (decrease of Th/U ratio), and large increase in concentrations of productive elements (P, Ba, Ni, Cu) is observed upsection. Nutrients supply via upwelling seems to be the most likely explanation. Increase in phosphorus accumulation rate and a microfacies change from Saccocoma to calpionellid dominated took place in the polarity chron M19r, which apparently coincided with the worldwide Nannofossil Calcification Event, related to a bloom of strongly calcified calcareous nannoplankton taxa. Deposition in the Lókút area was probably affected by long-term climatic trends: aridization and warming. Decreasing δ¹³C values of bulk carbonates throughout the Tithonian and the Berriasian are interpreted as a result of a global trend of accelerated carbonate productivity supported by local factors such as increased upwelling intensity, and a possible change in the composition of carbonate mud.
... The Upper Jurassic d 13 C-values of 2Á0 to 2Á5& measured in the medium to coarse-grained calcarenites at the base of the Lower Sid'r Member correspond with values measured in pelagic limestones of the same age (e.g. Weissert & Channell, 1989;Padden et al., 2002). These calcarenites coincide with the sealevel lowstand documented on the Arabian Fig. 1 and Table 1 for location). ...
... Correlation of the carbon-isotope record from the Lower Sid'r Member (Jabal Nukhayl-I section) and the Huwar 2 Member (Jabal Huwar section) with a section from the Umbria-Marche Basin (modified after Sprovieri et al., 2006) and the Vocontian Basin (Anglesmodified after Godet et al., 2006). The Oxfordian to Lower Valanginian carbon isotope composite curve based on Weissert & Channell (1989), Channell et al. (1993) and Padden et al. (2002). Bulk rock Sr-isotope values (>1000 ppm) are plotted in red against the compiled belemnite strontium isotope curve from the Vocontian Basin (Bodin et al., 2015). ...
Remnants of a Mesozoic continental margin can be studied today in the nappe pile of the Oman Mountains. Successions of the Arabian carbonate platform and the adjacent deep Hawasina Basin are preserved in the nappe pile and in the foothills of this Mountain range. The Jurassic–Cretaceous sediment successions of the Hawasina Basin (Sumeini and Hamrat Duru Group) are focus of this study. These basinal archives contain information on the response of an eastern Tethyan equatorial ocean system to multiple perturbations of the carbon cycle and of climate during the Cretaceous. Turbiditic continental slope and basinal successions formed near the Calcite Compensation Depth are difficult to date with biostratigraphy and sequence stratigraphy. The available stratigraphic framework for the Hawasina successions was not sufficient for tracing palaeoceanography through the time window of interest in this study. Therefore, existing sequence stratigraphy and biostratigraphy are complemented by additional biostratigraphic data and with a newly established carbon and strontium isotope chemostratigraphy. The Hawasina Basin was affected by sea-level variations, by changes in oceanography and also by regional tectonics. A first major modification of oceanography occurred at the end of the Jurassic when pelagic Maiolica-type sediments were accumulated in the deep basin and on adjacent submarine highs (Lower Member of Huwar and Sid'r formations). Pelagic to hemipelagic conditions existed until the Valanginian, marked by a major carbon isotope excursion. Pelagic sediments were afterwards replaced by a succession of fine to coarse grained turbidites of Hauterivian to Aptian in age. The transition into the mid-Cretaceous is marked by a sudden shift to fine grained siliceous or chert deposits, at a time when sediments enriched in organic carbon were accumulated in the western Tethys and Atlantic Oceans. The continental slope as well as the Hawasina Basin seemed to have been well-ventilated during Early and mid-Cretaceous time. Siliceous limestones and chert are indicator of well-mixed and nutrient-rich surface water, while absence of black shales suggests young and oxygenated deep water with a possible source on the vast Arabian platform. These peculiar oceanographic conditions were most pronounced during the onset of the extreme greenhouse episodes of the Oceanic Anoxic Event 1a. This article is protected by copyright. All rights reserved.
... A positive anomaly in the Late Callovian-Oxfordian is also found in numerous inorganic carbon-isotope curves from southern France, northern Italy (Jenkyns, 1996;Padden et al., 2002), the Moscow area (Russia), New Zealand (Podlaha et al., 1998), Siberia (Zakharov et al., 2014) and the central Atlantic Ocean (Katz et al., 2005). However, the timing of the excursion is not always exact, making correlation somewhat imprecise. ...
... Organic carbon isotope curves from left to right: Isle of Skye, Scotland (Nunn et al., 2009), Central Spitsbergen ), Dorset, England (Morgans-Bell et al., 2001 and Siberia (Zakharov et al., 2014). Carbonate carbon isotope curves: Western Tethys (Padden et al., 2002), Moscow Area, Russia (Price and Rogov, 2009), Helmsdale, Scotland (Nunn and Price, 2010), Central Southern Europe (Jenkyns, 1996), New Zealand (Podlaha et al., 1998), Siberia (Zakharov et al., 2014) and the Atlantic Ocean (Katz et al., 2005). See Fig. 3 for lithologic legend. ...
We present the first complete organic carbon isotope curve from the Agardhfjellet Formation, central Spitsbergen (Svalbard). Samples from two drill cores (DH2 and DH5R) were analysed for δ13Corg, total organic carbon (TOC) and Rock Eval. Rock Eval, litho- and biostratigraphy demonstrate a similar development in the two cores, allowing construction of a composite δ13Corg curve covering the Bathonian to lowermost Cretaceous. There are only weak correlations between Rock Eval parameters and δ13Corg, suggesting the isotopic signal is not mainly controlled by type of kerogen/maturation but rather reflects regional or global environmental changes. The carbon isotope curves from the cores can be correlated with previously published curves from outcrops of the Slottsmøya Member and with more distant localities in the Barents Sea, Siberia, Great Britain and the Atlantic. Features in common with other published curves include a Callovian-Oxfordian positive excursion, a Kimmeridgian-Middle Volgian negative trend and a Middle Volgian negative excursion. These correlations allow refinement chronostratigraphy of the Jurassic of Svalbard.
... range between +1.3 and +2.8‰ compared with mid-Tithonian pectinatus-fittoni Zone values of −2.3 to −0.4‰. This negative trend has also been recorded in other Kimmeridgian-Tithonian successions and has been shown to continue through the Late Tithonian and into the Early Berriasian (e.g., Weissert and Mohr, 1996;Weissert et al., 1998;Bartolini et al., 1999;Padden et al., 2002;Weissert and Erba, 2004). Published Kimmeridgian-Tithonian carbon isotope data have typically been compiled from bulk rock records in the Western Tethys, although relatively low-resolution belemnite data for this interval have also been published from New Zealand (Gröcke et al., 2003) and the Falkland Plateau (Price and Gröcke, 2002). ...
... Russian δ 13 C curve from Podlaha et al. (1998), Riboulleau et al. (1998) and Price and Rogov (2009). Tethyan δ 13 C curve from Weissert and Channell (1989), Jenkyns (1996), Weissert and Mohr (1996), Padden et al. (2002), Dromart et al. (2003) and Sandoval et al. (2008). Ages from Gradstein et al. (2004). ...
Late Jurassic (Kimmeridgian-Tithonian) carbon isotope stratigraphy and palaeoclimate data from Helmsdale, northeast Scotland
... Weighted averages were then calculated for the dataset normalized to the δ 13 C of bulk sediment. Finally, in order to assess the timing of carbon cycle perturbations detected in the ISOORG δ 13 C p LOESS analyses, we compare them to similar LOESS analyses performed on δ 13 C CO2 (Barral et al., 2017;Tipple et al., 2011) and the δ 13 C carb compilation (Cramer and Jarvis, 2020) from GTS-2020(Bachan et al., 2012Bartolini et al., 2013;Burgess et al., 2014;Cramer et al., 2009;Emmanuel and Renard, 1993;Gale et al., 2011;Galfetti et al., 2007;Garcia, 2008;Grabowski et al., 2019;Herrle et al., 2004;Herrle et al., 2015;Hesselbo et al., 2007;Jarvis et al., 2006;Jarvis et al., 2001;Jenkyns et al., 1994;Katz et al., 2005; Mercuzot et al., 2020;Mitchell et al., 1996;Muttoni et al., 2004;Muttoni et al., 2014;O'Dogherty et al., 2006;Oliveira et al., 2006;Padden et al., 2002;Paul et al., 1999;Paul et al., 1994;Payne et al., 2004;Pellenard et al., 2014a;Pellenard et al., 2014b;Preto et al., 2013;Rais et al., 2007;Sandoval et al., 2012;Sandoval et al., 2008;Schovsbo et al., 2008;Silva et al., 2011;Sprovieri et al., 2006;Sucheras-Marx et al., 2013;Sun et al., 2016;Thibault et al., 2012;Thibault et al., 2016;van de Schootbrugge et al., 2008;Voigt et al., 2010;Xie et al., 2007). Loess analyses were used because the large spread of data in the ISOORG precludes the use of a running average, which is often used to characterize inorganic carbon isotope compilations, and so that all time series were analyzed in the same manner. ...
Whereas carbon isotope ratios of marine carbonates are well characterized through the Phanerozoic, the carbon isotope ratios of terrestrial plant organic matter (δ13Cp) are less so due to the variety of plant parts and materials in which carbon is preserved and the challenges involved in interpreting carbon isotope fractionation in deep time. In 2016, an initial effort to compile published terrestrial organic carbon isotope data for the Phanerozoic (δ13Cp; ISOORG16; Nordt et al. 2016) was accomplished, consisting of 6888 δ13Cp estimates derived from ten organic matter sources. Here, we present an updated version of the Cenozoic and Mesozoic portions of that database (ISOORG23), consisting of 20,334 data points with an expanded 12 groups of organic material (i.e., amber, biomarkers, bulk sediment, coal, copal, leaves, n-alkanes, n-alkanoic acids, paleosol organic matter, peat, wood, and other plant parts). In addition, the entire database was updated to align with the 2020 Geologic Timescale (GTS-2020), with most δ13Cp data points (19,313) placed in 5 Myr bins and hypothetical numerical ages assigned to the subset of 12,828 data points where dating methods were available. Not surprisingly, we found that most published data are from Cenozoic age materials. Mean δ13Cp values for plant material (excluding amber and C3 plants) showed overall depletion in δ13Cp from the Mesozoic (−24.4 ± 0.02‰; n = 7895) to Cenozoic (−25.9 ± 0.02‰ n = 10,230). Among the different organic materials analyzed in ISOORG23, amber showed the highest δ13Cp values (−23.1‰), compared to sub-modern peat and copal with the lowest values (−26.8 and − 27.5‰, respectively). LOESS analyses of the ISOORG23 database with assigned numerical ages were compared to similar analyses performed on a compilation of carbon isotopes of marine calcium carbonate (δ13Ccarb) included in GTS-2020, as well as earlier compilations of atmospheric CO2 δ13C (δ13CCO2) for the Cenozoic and the Cretaceous portion of the Mesozoic. Those comparisons reveal both periods of correspondence and divergence between δ13Cp and δ13CCO2 and δ13Ccarb values, potentially indicating that major carbon cycle and/or climatic events are present in the δ13Cp data, though interpretation is affected by low data density during specific periods. A key finding is a consistently increased discrimination in both δ13Cp and δ13CCO2 records that begins at the Miocene Climatic Optimum and continues to the present. However, from the combined Cenozoic and Mesozoic data, that decline in δ13Cp began as early as 135 Ma.
... The same is true even when conditions of lower salinity prevail within shallow and restricted basins (Wierzbowski et al., 2018), that is, the conditions that prevailed during the wet climate of the EMO-OHE. On the other hand, such a positive δ 18 Ocarb excursion also occurs in the Scottish record from belemnite rostra (Fig. 3b), as well as within other probably contemporaneous deposits, such as the Upper Black Shale of the Makar'yev section of the Russian Platform (Wierzbowski et al., 2013) and the bulk carbonate record from the Auenstein section in the Swiss Jura (Padden et al., 2002). All these positive excursions display a deviation of ~1.5‰, which could correspond to a decrease of ~7 • C in the temperature of bottom waters (Dera et al., 2011). ...
Arido-eustasy is a model that explains palaeoenvironmental change by linking the covariation of the carbon isotope record and the eustatic sea level to orbitally modulated hydroclimatic intensity. Orbitally forced wet climate modes periodically accelerate the water cycle in the biosphere, modulating the balance between terrestrial fresh-water reservoirs and the eustatic sea level and perturbating the carbon cycle through catastrophic weathering of terrestrial carbon reservoirs, resulting in excessive transfer of carbon into the oceans. These intervals of extreme hydroclimatic intensity and weathering, or Orbito-Hyetal Events (OHEs), are hypothesised to be responsible for major palaeoenvironmental crises such as oceanic anoxic events and biotic extinction events. Here, I consider the available data and show evidence for the occurrence of a strong and short-term OHE at the end of the middle Oxfordian. The event probably lasted ∼40 kyr and was bracketed by characteristic arido-eustatic traits, including a prominent sea level fall (the OX5), a contemporaneous extreme (>2‰) negative excursion in the marine carbonate and terrestrial organic-carbon isotope records, and regional occurrences of anoxic environments with organic-rich deposits. Important prolific source-rock reservoirs, such as the Smackover, Hanifa, and Khodjaipak Formations in the Gulf of Mexico, Arabian Gulf, and Uzbekistan, respectively, seem to have been created during this end-middle Oxfordian OHE.
... Beaulieu et al., 2012). In hemipelagic carbonates in the Jura Mountains and the Vocontian basin, Padden et al. (2002) found negative δ 13 C excursions in the Transversarium and Bifurcatus ammonite zones (i.e. below SB Ox 6; Fig. 3), which are explained by the release of methane, introducing light 12 C into the marine carbon reservoir. ...
Today and in the geologic past, climate changes greatly affect and have affected Earth surface processes. While the climatic parameters today can be measured with high precision, they have to be interpreted from the sedimentary record for ancient times. This review is based on the detailed analysis of stratigraphic sections of Oxfordian (Late Jurassic) age, with the aim to reconstruct and discuss the climate changes that controlled the sedimentation on the shallow marine carbonate platform that today is represented in the Swiss Jura Mountains. The sediments formed under subtropical conditions in which carbonate-producing organisms proliferated, and ooids and oncoids were common. The sections are composed of hierarchically stacked elementary, small-scale, and medium-scale depositional sequences wherein facies changes imply deepening–shallowing trends. The major sequence boundaries Ox 6, Ox 7, and Ox 8 can be correlated with those of other European basins and place the studied sections in a broader framework. The chronostratigraphic tie points imply that the medium- and small-scale sequences formed in tune with the orbital eccentricity cycles of 405 and 100 kyr, respectively, and the elementary sequences with the precession cycle of 20 kyr. Orbitally controlled insolation changes at the top of the atmosphere translated into climate changes: low insolation generally resulted in low amplitudes of sea level fluctuations at the 20 kyr frequency and in a cool and humid climate at the palaeolatitude of the Jura platform. Terrigenous material was eroded from the hinterland and distributed over the platform. High insolation led to sea level rise, as well as to warm and semiarid to arid conditions in which coral reefs could grow. However, nutrient input favoured growth of microbialites that encrusted the corals. The reconstruction of high-frequency sea level fluctuations based on facies analysis compares well with the curve of insolation changes calculated for the past 550 kyr. It is therefore assumed that the sea level fluctuations were mainly due to thermal expansion and retraction of ocean surface water. Two models are presented that explain the formation of elementary sequences: one for low and one for high insolation. Despite the important lateral facies variations typical of a shallow marine platform, and despite the uncertainties in the reconstruction of sea level changes, this study demonstrates the potential of carbonate ecosystems to record past climate changes at a time resolution of 20 000 years. Relatively short time windows can thus be opened in the deep geologic past, and processes and products there can be compared with those of the Holocene and the Anthropocene. For example, it appears that today's anthropogenically induced sea level rise is more than 10 times faster than the fastest rise reconstructed for the Oxfordian.
... The bulk carbon-isotope chemostratigraphy of Jurassic sections is of crucial importance in sequences impoverished in, or completely barren of index fossil remains. Relatively numerous carbon isotope data derive from Tethyan and peri-Tethyan Middle-Upper Jurassic deposits (e.g., Bartolini et al., 1999;Jenkyns et al., 2002;O'Dogherty et al., 2018), with one exception for the Callovian-middle Oxfordian interval, where such data are scarce and display some discrepancy in temporal trend (e.g., Bartolini et al., 1999;Cecca et al., 2001;Padden et al., 2002;Jach et al., 2014;Wierzbowski, 2015;Arabas, 2016;O'Dogherty et al., 2018). ...
... A similar scenario has previously been reported by Lécuyer and Allemand [27] and Vickers [28], from clumped isotopes and conventional oxygen isotope data, to interpretate the climatic change throughout Jurassic Cretaceous times. Furthermore, the covariance between oxygen and carbon isotopic compositions in marine carbonates ( Figure 8) is probably linked to period boundaries with climate change [29,30]. ...
Abstract:
Utilizing sophisticated tools in carbonate rocks is crucial to interpretating the origin and evolution of diagenetic fluids from the Upper Jurassic carbonate rocks along the Zagros thrust-fold Belt. The origin and evolution of the paleofluids utilizing in-situ strontium isotope ratios by high resolution laser ablation ICP-MS, integrated with stable isotopes, petrography and fieldwork are constrained. Due to the lack of information on the origin of the chemistry of the fluids, the cements that filled the Jurassic carbonate rocks were analysed from the fractures and pores. This allowed us to trace the origin of fluids along a diagenetic sequence, which is defined at the beginning from the sediment deposition (pristine facies). Based on petrography and geochemistry (oxygen-, carbon- and strontium-isotope compositions) two major diagenetic stages involving the fluids were iden- tified. The initial stage, characterized by negative δ13CVPDB values (reaching −10.67‰), involved evaporated seawater deposited with the sediments, mixed with the input of freshwater. The sec- ond stage involved a mixture of meteoric water and hot fluids that precipitated as late diagenetic cements. The late diagenetic cements have higher depleted O–C isotope compositions compared to seawater. The diagenetic cements display a positive covariance and were associated with extra- δ13CVPDB and δ18OVPDB values (−12.87‰ to −0.82‰ for δ18OVPDB and −11.66‰ to −1.40‰ for δ13CVPDB respectively). The distinction between seawater and the secondary fluids is also evident in the 87 Sr/86 Sr of the host limestone versus cements. The limestones have 87 Sr/86 Sr up to 0.72859, indicative of riverine input, while the cements have low 87Sr/86Sr (0.70772), indicative of hot fluid circulation interacting with meteoric water during late diagenesis.
https://www.mdpi.com/2073-4441/13/22/3284
... In particular, orogenic processes in Asia at the northern margin of the Tethys Ocean may have contributed to high-latitudinal cooling (see the text for a discussion and references). Major carbon-cycle perturbation, associated with negative carbon isotope excursions (CIEs), occurred upon the termination of cold phases: Triassic-Jurassic CIE (T/J-CIE): Lindström et al. (2020) and Ruhl et al. (2020); early Pliensbachian CIE (ePl-CIE): Korte and Hesselbo (2011) and Schöllhorn et al. (2020); Pliensbachian-Toarcian CIE (Pl-Toa-CIE) and Toarcian CIE (Toa-CIE): Hesselbo et al. (2000Hesselbo et al. ( , 2007 and Ruebsam and Al-Husseini (2020); Bajocian CIE (Baj-CIE): Hesselbo et al. (2003); Oxfordian CIE (Ox-CIE): Padden et al. (2001Padden et al. ( , 2002. determined for some of the negative CIEs, attest to the orbitally forced emission of 12 C-enriched carbon from climate-sensitive carbon reservoirs rather than reflecting simply volcanic CO 2 emissions (e.g. ...
The historical view of an equable Jurassic greenhouse world has been challenged by recent studies documenting recurrent alternation between contrasting climate modes. Cooling of high-latitudinal areas may have been caused by orogenic processes at the northern margin of the Tethys Ocean that reduced the heat-transport towards polar regions. Warm phases correlate to periods of intensified volcanism. The Jenkyns Event occurred during the transition from a late Pliensbachian Icehouse into an early Toarcian Greenhouse. Parallel evolution of different environmental processes, including sea level, climate, and carbon cycle indicate a causal mechanism tied to astronomical forcing. Insolation-controlled variations in the extent of the cryosphere (ice caps and permafrost) facilitated both orbitally-paced sea level cycles via waxing and waning of polar ice caps and negative carbon isotope excursions via the release of cryosphere-bound ¹² C-enriched carbon. This review and synthesis of sedimentological, geochemical, and paleontological paleoenvironment indicators and of simulations from climate models aims at reconstruction of particularly the high-latitudinal environmental condition during late Pliensbachian to early Toarcian times. Focus is laid on the extent of regions that were potentially suitable for hosting a cryosphere. Environmental response to cryosphere dynamics is considered to have been a key component of the Jenkyns Event.
... Three aliquots of each of the three limestone clasts (two of them with shatter cones) from the Blockhorizont yielded δ 13 C and δ 18 Table S4). These are typical values for Upper Jurassic marine limestones from north of the western Tethys 34 . In addition, three samples of a shatter cone from the Steinheim structure show δ 13 C values between 2.1 and 2.2‰, perfectly matching the values of the Blockhorizont clasts. ...
Impact ejecta formation and emplacement is of great importance when it comes to understanding the process of impact cratering and consequences of impact events in general. Here we present a multidisciplinary investigation of a distal impact ejecta layer, the Blockhorizont, that occurs near Bernhardzell in eastern Switzerland. We provide unambiguous evidence that this layer is impact-related by confirming the presence of shocked quartz grains exhibiting multiple sets of planar deformation features. Average shock pressures recorded by the quartz grains are ~ 19 GPa for the investigated sample. U–Pb dating of zircon grains from bentonites in close stratigraphic context allows us to constrain the depositional age of the Blockhorizont to ~ 14.8 Ma. This age, in combination with geochemical and paleontological analysis of ejecta particles, is consistent with deposition of this material as distal impact ejecta from the Ries impact structure, located ~ 180 km away, in Germany. Our observations are important for constraining models of impact ejecta emplacement as ballistically and non-ballistically transported fragments, derived from vastly different depths in the pre-impact target, occur together within the ejecta layer. These observations make the Ries ejecta one of the most completely preserved ejecta deposit on Earth for an impact structure of that size.
... The upper Jurassic Oxfordian contains significant positive and negative excursions in δ 13 C (e.g., Padden et al., 2002;Jenkyns et al., 2002;Gröcke et al., 2003;Weissert and Erba, 2004), of which a relatively brief, but pronounced positive peak within the upper Perisphinctes plicatilis ammonite zone might serve as useful global correlation horizon (e.g., Pearce et al., 2005;Głowniak and Wierzbowski, 2007;Wierzbowski, 2015). This positive excursion in carbon isotopes is within a broad elevated 13 C enrichment that is coeval with major carbon-rich sediment deposits that became the hydrocarbon source rocks of Saudi Arabia, the North Sea, Siberia, and other regions. ...
Ammonites underwent an evolutionary diversification after the mass extinction of the end Triassic induced by the formation of a Large Igneous province (LIP), and this group provides the most useful marine biostratigraphy. Only two levels within the Jurassic are relatively well determined using U–Pb dating from single zircons in ash beds, at the base Hettangian and the Pliensbachian–Toarcian boundary. Otherwise the Lower Jurassic is scaled using astrochronology and the Middle and Upper Jurassic scaled from Pacific seafloor spreading rates correlated to magnetic reversals. LIP activity during the Early Jurassic (Triassic–Jurassic boundary and Toarcian) perturbed global environments to extents not evidenced since the end Permian, and age relationships allow for a strong causal connection between these LIP eruptions and mass extinctions caused by major paleoenvironmental change, including ocean anoxia. Breakup of the supercontinent Pangea dominated paleogeography and paleoceanography and created shallow seaways that form sources and traps for hydrocarbons. Calcareous planktonic algae diversified and migrated from shallow seaways to open oceans to set the stage for the beginning of modern oceanic biogeochemical cycling; calcareous nannofossils provide additional widely used correlation tools.
... Orange bar indicates boundary between Saccocoma and calpionelid microfacies. 2001; Padden et al., 2002;Grabowski et al., 2010aGrabowski et al., , 2017Žak et al., 2011;Jach et al., 2014;Michalík et al., 2016;Pszczółkowski et al., 2016) and from Velykyi Kamianets (Fig. 13). The long-term decrease of δ 13 C values of bulk carbonates is regarded as a result of diminishing global burial rate of marine organic matter and/or increasing calcium carbonate productivity (Weissert and Channell, 1989;Weissert et al., 1998;Price et al., 2016). ...
A continuous sedimentary and stratigraphic record of Late Kimmeridgian – Early Berriasian age is presented from the pelagic succession from the eastern part of the Pieniny Klippen Belt (Velykyi Kamianets section, Ukraine). The studied section, 26-m-thick, was calibrated using biostratigraphy (calpionellids, calcareous dinocysts, calcareous nannofossils), magnetostratigraphy, stable isotope stratigraphy (δ¹³C and δ¹⁸O) and gamma ray spectrometry. Magnetic polarity zones from M23r to M18n were identified. The magnetostratigraphic calibration of calcareous dinocysts zonation around the Kimmeridgian/Tithonian boundary has been performed for the first time. The Carpistomiosphaera borzai/Committosphaera pulla calcareous dinocyst zonal boundary is situated at the bottom of magnetozone M22n, slightly lower than first occurrence of calcareous nannofossil Conusphaera mexicana minor and higher than the standard Kimmeridgian/Tithonian boundary (M22Ar/M22An; Hybonoticeras beckeri/Hybonoticeras hybonotum Ammonite Zone boundary). The position of the Tithonian/Berriasian boundary in the magnetosubzone M19n2n (Crassicollaria/Calpionella Calpionellid zonal boundary) has been confirmed. A decrease of terrigenous input and an increase of carbonate productivity correlate with increasing sedimentation rates from 0.7 to 1.1 m/Myr in the Upper Kimmeridgian (M23r to M22r) to 5–7 m/Myr in the uppermost Tithonian and Lower Berriasian (M19n to M18n). Transition between the Saccocoma and calpionellid microfacies occurs in a narrow time interval, mostly within polarity subchron M20n1r. This event is traceable in similar stratigraphic position in several Western Tethyan sections and correlates perfectly with Nannofossil Calcification Event of the early Late Tithonian.
... Leinfelder et al., 2002;Philip, 2003)．また白亜 紀になると，浮遊性有孔虫と石灰質ナンノプランクトンが爆発的に増加し，その遺骸が海底へと堆積 した．このように，炭酸塩の殻を形成する生物たちによって，大気-海洋系から大量の炭素が海中に 固定された． ジュラ紀後期から白亜紀前期の炭酸塩岩の炭素同位体変動の研究はヨーロッパ・テチスで行われて きた(e.g. Alps: Weisssert and Mohr, 1996;Weisssert et al., 1998;Padden et al., 2002, andWeisssert andErba 2004;Pyrenee : Bádenas et al., 2005)．多くの研究がなされてきたために，ジュ ラ紀後期から白亜紀前期にかけての海洋事変はヨーロッパ地域のテチス海域の層序学的記録に基づ いて定義されてきた．しかし，当時のヨーロッパ・テチスは北アメリカ大陸，ゴンドワナ大陸，ロー レシア陸塊群などに囲まれた内海のきわめて奥まった場所に位置し (Scotese, 2001)，この海域でのデ ータがこの時代の古海洋学的な変動をすべて代表しているとは考えにくい． 一方で，当時地球表面の約 60%を占めていた古太平洋海域の炭素同位体比を示した研究例は少ない (e.g. Gröcke, et al., 2004;Kakizaki and Kano, in press ...
... Leinfelder et al., 2002;Philip, 2003)．また白亜 紀になると，浮遊性有孔虫と石灰質ナンノプランクトンが爆発的に増加し，その遺骸が海底へと堆積 した．このように，炭酸塩の殻を形成する生物たちによって，大気-海洋系から大量の炭素が海中に 固定された． ジュラ紀後期から白亜紀前期の炭酸塩岩の炭素同位体変動の研究はヨーロッパ・テチスで行われて きた(e.g. Alps: Weisssert and Mohr, 1996;Weisssert et al., 1998;Padden et al., 2002, andWeisssert andErba 2004;Pyrenee : Bádenas et al., 2005)．多くの研究がなされてきたために，ジュ ラ紀後期から白亜紀前期にかけての海洋事変はヨーロッパ地域のテチス海域の層序学的記録に基づ いて定義されてきた．しかし，当時のヨーロッパ・テチスは北アメリカ大陸，ゴンドワナ大陸，ロー レシア陸塊群などに囲まれた内海のきわめて奥まった場所に位置し (Scotese, 2001)，この海域でのデ ータがこの時代の古海洋学的な変動をすべて代表しているとは考えにくい． 一方で，当時地球表面の約 60%を占めていた古太平洋海域の炭素同位体比を示した研究例は少ない (e.g. Gröcke, et al., 2004;Kakizaki and Kano, in press ...
... High-resolution δ 13 C chemostratigraphy offers highly resolved temporal correlations at a resolution finer than other chronological techniques (e.g., Weissert, 1989;Weissert and Breheret, 1991;Weissert et al., 1998;Veizer et al., 1999;Padden et al., 2002). It can provide independent tests for constraining and correlating lithofacies within carbonate systems and reveal paleogeographic, paleoclimatic, and paleo-oceanographic controls (e.g., Immenhauser et al., 2003;Tsikos et al., 2004;Swart and Eberli, 2005;Koch et al., 2014;Metzger et al., 2014). ...
Carbon isotope data (δ¹³C) can provide an essential means for refining paleogeographic and paleo-oceanographic reconstructions, and interpreting stratigraphic architecture within complex carbonate strata. Although the primary controls on global δ¹³C signatures of marine carbonates are well understood, understanding their latitudinal and regional variability is poor. To better constrain the nature and applications of δ¹³C stratigraphy, this study: 1) presents a new high-resolution δ¹³C stratigraphic curve from Middle to Upper Jurassic carbonates in the upper Tuwaiq Mountain, Hanifa, and lower Jubaila formations in central Saudi Arabia; 2) explores their latitudinal and regional variability; and 3) discusses their implications for stratigraphic correlations. Analysis of δ¹³C data identified six mappable units with distinct δ¹³C signatures (units 1–6) between up-dip and down-dip sections, and one unit (unit 7) that occurs only in the down-dip section of the study succession. δ¹³C data from the upper Tuwaiq Mountain Formation and the lower Hanifa Formation (units 1, 2), which represent Upper Callovian to Middle Oxfordian strata, and record two broad positive δ¹³C excursions. In the upper part of the Hanifa Formation (units 3–6, Early Oxfordian–Late Kimmeridgian), δ¹³C values decreased upward to unit 7, which showed a broad positive δ¹³C excursion. Isotopic data suggest similar δ¹³C trends between the southern margin of the Tethys Ocean (Arabian Plate; low latitude, represented by the study succession) and northern Tethys oceans (high latitude), despite variations in paleoclimatic, paleogeographic, and paleoceanographic conditions. Variations in the δ¹³C signal in this succession can be attributed to the burial of organic matter and marine circulation at the time of deposition. Our study uses δ¹³C signatures to provide independent data for chronostratigraphic constraints which help in stratigraphic correlations within heterogeneous carbonate successions.
... Outside the Boreal realm, Katz et al. (2005) recorded a marked negative excursion in δ 13 C carb in the Middle Tithonian of DSDP site 534A, Blake-Bahama Basin, which they correlated with another negative but less prominent excursion in the Western Tethys ( Padden et al. 2002). A small negative excursion is similarly recorded in middle Late Tithonian of the Northern Tethys ( Weissert and Mohr 1996). ...
... There is a remarkable negative shift in δ¹³Ccarb during the early transversarium ammonite zone (around the Middle-Late Oxfordian boundary) in the record from SE France, which has also been reported by previous studies [39,40] . Initially, the negative shift was correlated with a methane release episode [39] comparable to other known episodes such as the well-studied episode in the Palaeocene-Eocene boundary. ...
For 30 years, the initial sedimentation following the opening of the western Central Atlantic has been considered to be of Middle Callovian age (approximately 164.5 Ma) based on the biochronostratigraphical estimation for the basal sedimentary unit of the borehole from Site 534A of the Deep Sea Drilling Program (DSDP). That age has been used in kinematic models of the opening of the Central Atlantic. A reconsideration of the available biochronostratigraphical data and correlation of the δ¹³Ccarb record from Site 534A with those from the Tethyan and North Atlantic records suggest that the initial sedimentation at Site 534A is, in fact, of Middle Oxfordian age (approximately 160.6 Ma). The high biostratigraphic similarity among the basal sedimentary units of the boreholes at DSDP Site 534A and Ocean Drilling Program Site 801C in the Western Pacific suggest the same age for both sites. The Middle Oxfordian δ¹³Ccarb records from the different sites covary, marking the same palaeoenvironmental changes, although such an agreement was not previously acknowledged. A combination with additional data proposes that Middle Oxfordian age corresponds to the precise date of the opening of the Hispanic Corridor between the Atlantic and Pacific oceans.
... Previous δ 13 C data for the Upper Jurassic sediments of the Tethys region were obtained for its Western passive margin and Central Atlantics (Padden et al. 2002, Coimbra et al. 2009). These data have been acquired from precisely dated hemipelagic sediments containing index fauna and epioceanic Ammonitico-Rosso facies. ...
... Increasingly negative δ 18 O values are often correlated with elevated temperatures in environmental settings where continental ice volume is at a minimum and evaporation or freshwater inputs are minor factors. Similar trends have been observed elsewhere (e.g., Tremolada et al., 2006;Price and Rogov, 2009;Grabowski et al., 2010b), but not universally as other studies found opposite trends (e.g., Emmanuel and Renard, 1993;Padden et al., 2002). Larger datasets through the Late Jurassic and into the Cretaceous, based on the isotopic composition of fossil belemnites and brachiopods (e.g., Veizer, et al., 1999;Gröcke et al., 2003;Wierzbowski, 2004;McArthur et al., 2007;Riboulleau et al., 1998;Bodin et al., 2009Bodin et al., , 2015Price and Rogov 2009;Dera et al., 2011;Alberti et al., 2012;Price et al., 2000;2013;Meissner et al., 2015), also show a similar trends (Fig. 8). ...
... The most negative values were found at 148.7 Myr in their age model based on Gradstein et al. (1995), placing the excursion in the Pavlovia pallasioides zone. They correlate this excursion with a much less prominent negative excursion in the western Tethys (Padden et al. 2002). ...
We present δ13Corg curves for the Upper Jurassic to lowermost Cretaceous of central Spitsbergen. The three sections span the Slottsmøya Member
(Agardhfjellet Formation) at Janusfjellet and Knorringfjellet in the Sassenfjorden area. The results indicate that bulk organic carbon isotope chemostratigraphy
can be used as a tool for high-resolution, local chronostratigraphic correlation in central Spitsbergen, resolving problems of possible
overthrusts, slumping and diachronous lithological boundaries. Moreover, the curves can be compared with published data from carbonates on the
Russian Platform, recording a negative δ13C trend through the Lower Volgian followed by a positive trend from the lower part of the Middle Volgian
and into the Upper Volgian. The minimum in the curve in the lower Middle Volgian is sharply defined, and this negative excursion may provide a
useful chemostratigraphic marker for correlation between the Barents Sea and the Russian Platform, and possibly globally. The excursion is here
called VOICE (Volgian Isotopic Carbon Excursion). There are indications of a c. 400 kyr periodicity, which can be interpreted as a result of orbital
forcing (long eccentricity). In contrast, inorganic carbon and oxygen isotopes from carbonates in the Sassenfjorden area mainly reflect diagenetic
processes.
... Increasingly negative δ 18 O values are often correlated with elevated temperatures in environmental settings where continental ice volume is at a minimum and evaporation or freshwater inputs are minor factors. Similar trends have been observed elsewhere (e.g., Tremolada et al., 2006;Price and Rogov, 2009;Grabowski et al., 2010b), but not universally as other studies found opposite trends (e.g., Emmanuel and Renard, 1993;Padden et al., 2002). Larger datasets through the Late Jurassic and into the Cretaceous, based on the isotopic composition of fossil belemnites and brachiopods (e.g., Veizer et al., 1999;Gröcke et al., 2003;Wierzbowski, 2004;McArthur et al., 2007;Riboulleau et al., 1998;Bodin et al., 2009Bodin et al., , 2015Price and Rogov, 2009;Dera et al., 2011;Alberti et al., 2012;Price et al., 2000Price et al., , 2011Price et al., , 2013Meissner et al., 2015), also show a similar trends (Fig. 8). ...
Late Jurassic–Early Cretaceous carbon isotope stratigraphies derived from measured sections in the Bakony and the Gerecse Mts. (Hungary), constrained by ammonite, belemnite and calpionellid biostratigraphy together with magnetostratigraphy are presented. We evaluate whether a consistent pattern in carbon (and oxygen) isotope varia-tion can be established, particularly with respect to the Jurassic–Cretaceous boundary. We also assess the possible controls on carbon isotope variation and the correlation potential. Oxygen isotopes point to warming through this interval. We observe a decrease in carbon isotopes through the Late Jurassic, consistent with carbon isotope strati-graphies of the Western Tethys. A change to more positive carbon isotope values in the Early Cretaceous is manifest in the Valanginian Weissert event, potentially reflecting a change to increasingly nutrient-rich conditions and en-hanced carbon cycling. Biostratigraphic and magnetostratigraphic data allow us to accurately place the low point seen in the carbon isotope curve within these schemes. Locally a carbon isotope minimum appears in the upper part of magneto subzone M19n2n and towards the middle of calpionellid Zone B (i.e. the Alpina Subzone), but not resolved in the carbon isotope stack from across Tethys and the Atlantic. Aside from the well-defined Valanginian event, chemostratigraphic correlation across the Jurassic–Cretaceous boundary using the carbon isotope record is challenging due to relatively stable carbon isotope values resulting in a curve with a slope too slight.
... A subsequent warming during the mid-Oxfordian (Jenkyns et al., 2002;Wierzbowski, 2002) was probably related to a 'methane pulse' (Padden et al., 2001). During the late Oxfordian to earliest Berriasian, oceanic and coastal palaeoenvironmental conditions became increasingly stable (Abbink et al., 2001;Padden et al., 2002;Lindström and Erlström, 2011); from late Berriasian times onwards, the climate evolved towards more warm and humid conditions (McArthur et al., 2007;Bodin et al., 2009). At this stage, the fluctuations observed in the Late Jurassic to Early Cretaceous greenhouse climate are mainly documented from the marine realm, whereas information derived from continental rocks including terrestrial vegetation, is relatively scarce. ...
... There is oxygen-isotope evidence for short-term cooling in the early Aptian, immediately after deposition of black shales in some regions, e.g. in Northern Germany (from belemnites e Fischschiefer level) (Mutterlose et al., 2009), in the North Atlantic (from planktic foraminifera) (Huber et al., 2011), in France, Italy and Switzerland (from fish-teeth phosphate; Pucéat et al. (2005) and from bulk carbonates, e.g., Weissert et al., 1985;Weissert and Channell, 1989;Padden et al., 2002;Weissert and Erba, 2004)), in China, Thailand and Japan (from apatite phosphatic reptile remains; Amiot et al., 2011). This trend is supported by palynological data. ...
... A trend, observable in the Hlboča section, was accompanied by a decrease of organic C content in sediments. High positive δ 13 C values in the lowermost part of this section belonging to the dinoflagellate Fibrata Acme Zone (Reháková in Michalík et al. 1990;Reháková 2000) are comparable to the Oxfordian δ 13 C event of Jenkyns (1996) located in the Transversarium ammonite Zone (Padden et al. 2002). Due to low sedimentary rate and oxidic environment with effective organic matter biocycling, the water equilibrium has been shifted more to a negative value as a part of the decreasing δ 13 C trend in the Kimmeridgian and Tithonian part of the Tegernsee Formation (Fig. 11). ...
Magneto- and isotope stratigraphic studies in the Vysoká Nappe (Hlboca section, Fatric Unit, Malé Karpaty Mts, Slovakia) were performed. A generally decreasing delta13C isotope curve is interpreted as a primary trend from the Late Oxfordian (3.3 0/00 V-PDB) to the Late Tithonian (1.8-1.4 0/00 V-PDB). Data from the Tithonian part of the Tegernsee Formation probably reflect "local" basin processes connected with the breccia formation in the latest Tithonian/earliest Berriasian and/or with possible diagenetic overprint. The C-isotope record of the Berriasian Padlá Voda Formation is more homogeneous (1.4-1.8 0/00 V-PDB) and assumed to be primary. Magnetostratigraphic investigations were focused on the Jurassic/Cretaceous (J/K) boundary strata. Upper Tithonian nodular limestones of the Tegernsee Formation differ substantially from Lower Berriasian calpionellid limestones of the Padlá Voda Formation in rock magnetic properties. Hematite is present in the Tegernsee Formation, while magnetite is the only magnetic mineral of the Padlá Voda Formation. Additionally, the latter formation contains superparamagnetic magnetite, which significantly influences its magnetic susceptibility. Correlation of normal and reversed magnetic intervals with the Late Tithonian global polarity time scale was supported by microfossil stratigraphy. M21n to M20n magnetozones were distinguished, including the short reversed Kysuca (M20n1r) Subzone within M20n. Interpretation of Lower Berriasian magnetostratigraphy was more complex due to presence of breccia horizons and a stratigraphic gap at the J/K boundary in the lower part of the Padlá Voda Formation embracing M19r and most of M19n magnetozones. This formation was also partially affected by remagnetization. Detailed correlation between the isotope- and magnetic stratigraphy of the Tithonian-Berriasian interval between Hlboca and Brodno sections is also complex due to J/K stratigraphical gap within the Hlboca section. The primary B component accounts for counter-clockwise rotation of the Vysoká Unit with a magnitude of ca. 50°. Since the paleodeclination of Paleogene and Karpatian-Eggenburgian rocks in the area is similar, the rotation must have taken place after Early Miocene. The paleoinclinations of several Upper Tithonian-Berriasian sections of the Central Western Carpathians and western part of the Pieniny Klippen Belt are consistent and indicate paleolatitude of 27-30°N.
Relevance of the work. Black shale horizons may reflect abrupt paleoclimate changes. In the northeast of the Ulyanovsk-Saratov Trough (UST), two black shale horizons widely occur, the Middle Volgian Promzino Formation and the Lower Aptian Ulyanovsk Formation. Despite years of research, the role of paleoclimate in their accumulation is still under discussion. The aim of the research was to assess the climate as a factor of the accumulation of the Middle Volgian and Lower Aptian organic carbon-rich deposits in the northeastern UST. Methods. To reconstruct paleoclimate and to evaluate its impact on the black shale deposition, a comprehensive isotope study of calcitic and aragonitic shells of several groups of benthic and pelagic organisms was performed. Besides, the lithological and geochemical features of organic carbon-rich and host deposits were studied using optical microscopy, XRD, and pyrolysis. Results. Isotope study allowed to construct benthic and pelagic palaeotemperature curves and to reconstruct paleoclimate in the UST during the formation of black shales. Based on these data and data on lithological and geochemical features of sediments, the depositional mechanisms of the Promzino and Ulyanovsk Formations were clarified. Conclusions. No causal link has been revealed between climate changes and the deposition of the Middle Volgian black shales. At the end of the Middle Volgian, a short-term cooling has been recorded, probably related to the volcanic activity of the northern Tethyan margin. The Lower Aptian black shales were formed during the hyperthermal. This hyperthermal controlled the accumulation of organic carbon-rich sediments by increasing the input of nutrients and/or providing conditions for its stratification and stagnation.
The Middle–Late Jurassic opening of the central Atlantic and proto-Caribbean seaways connecting the Pacific with the Tethys Ocean combined with rising sea level led to a major oceanographic and climatic reorganization conducive to the development of widespread carbonate platforms and diverse reefs. The timing of this shift in carbonate production and opening of the Tethys Ocean is well-constrained from outcrops in Europe and western Asia and marked by a notable positive carbon isotope (δ13C) excursion in the middle Oxfordian Gregoryceras transversarium ammonite Zone, termed “MOxE”. However, the temporal constraints from the western arm of the circum-global seaway through the proto-Caribbean and Gulf of Mexico are not well resolved. Presented here are the first paired organic and carbonate carbon-oxygen isotope records from the Smackover Formation, Gulf of Mexico, that record a positive δ13C isotope excursion that is correlated to the middle Oxfordian transversarium Zone. These data are the first record of the MOxE in the Western Hemisphere and provide temporal constraints on the opening of the Gulf of Mexico. Furthermore, the existence of similar δ13C profiles from European basins strongly suggests a coeval response of the carbon cycle to the opening of the central Atlantic and proto-Caribbean seaways connecting the Pacific with the Tethys Ocean.
The Cauvery Basin at the southeastern tip of the Indian plate was an Albian to Danian marine embayment. The Dalmiapuram Formation is composed of bioclastic wackestone and coral boundstone. Benthic foraminifera and calcareous algae are relatively common in the Dalmiapuram Formation. The fossils support an age range of upper Albian to Cenomanian, which complements previously reported nannofossils that suggest an early Albian to Turonian age. The low diversity assemblage of foraminifera and calcareous algae and other organisms in the Dalmiapuram Formation is characteristic of a near-shore carbonate shelf or ramp. The low diversity and abundance of planktic species with coral and coral-algal buildups suggests more offshore conditions, probably within storm wave-base. The δ13C and δ18O values vary greatly. The absence of correlation between Mn and Sr indicates that these limestones retain their primary isotopic signatures. Gray shale/limestone unit has positive carbon isotope excursion (CIE) of ~ 0.8 to 1.0‰ that correlate with OAE 1c event. Similarly, significant positive CIE noticed in the lower part of the coral algal limestone is attributed to OAE 1d event. This suggests that oceanic conditions that created deep-water low oxygen conditions affected the shallow-water photic zone.
To obtain a stratigraphic standard section for the Upper Jurassic of the Lower Saxony Basin, we investigated a 325-m-long core using biostratigraphic (benthic foraminifers, ostracods, and palynology) and chemostratigraphic (stable carbon isotope data) methods. From the results, we were able to establish a detailed biozonation of the section.
: Ammonites exploded in diversity after the end-Triassic near-extinction of their precursor taxa and have been the main tool for global correlation for nearly two centuries. The Pangea super-continent split during mid-Jurassic into Laurasia and Gondwana separated by a Tethys-Atlantic seaway. Late Jurassic organic-rich shales would later provide nearly half of our oil-gas source rocks. Dinosaurs dominated the land surface, and their cousins took to the air.
Oxygen and carbon isotope values and elemental ratios of well-preserved belemnite rostra, brachiopod shells and bulk-carbonates from the Upper Callovian–Lower Kimmerdgian of the Polish Jura Chain, Kujawy (Poland) and Swabian Alb (Germany) are investigated to reconstruct environmental conditions and perturbations in the marine carbon cycle. Belemnite δ¹⁸O values show relatively constant temperatures (ca. 12°C) of bottom waters in the Polish Jura Chain basin during a major part of the Late Callovian–Middle Oxfordian, except for a short-term cooling (to ca. 9°C) at the Callovian–Oxfordian transition. Belemnite and brachiopod δ¹⁸O values show a gradual increase in temperature during the Submediterranean Late Oxfordian; the highest temperatures (ca. 16°C) are calculated for the Submediterranean Oxfordian–Kimmeridgian transition. Belemnite and brachiopod Mg/Ca and Sr/Ca ratios are disregarded as a palaeotemperature proxy because of their weak correlation with δ¹⁸O values.
Feedback mechanisms between carbon cycling, climate and oceanography: a combined geochemical, sedimentological and modeling approach
The isotopic composition of the global carbon reservoir integrates large kinetic fractionations from photosynthesis with small thermodynamic fractionations from carbonate precipitation. We present concordant delta 13C records of carbonates (delta 13Ccarb) and organic matter (delta 13Corg), along with new carbonate (Ccarb) and organic carbonate (Corg) fluxes for the past ˜205 myrs (Jurassic-Cenozoic) generated from bulk sediment samples from the Atlantic. The new delta 13Corg record greatly refines previous compilations (Hayes et al., 1999) by providing a sample resolution of ˜100-300 kyrs. Model simulations using these delta 13Ccarb and delta 13Corg data provide constraints on carbon sources (mantle and weathering) and sinks (carbonate and organic carbon sedimentation); comparisons with the flux records provide insight on the components of the geological carbon cycle. Stable isotope records indicate that long-term net depletion of 12C from mobile carbon reservoirs was a consequence of an organic carbon burial fraction increase of ˜0.05-0.1 that began in the Jurassic ( ˜200 Ma). Superimposed on the long-term trend are higher-order variations (5-10s of myrs) in delta 13Ccarb and delta 13Corg that show episodic intervals of elevated values. In contrast to paleoceanographic convention, organic carbon burial is often decoupled from global delta 13C variations on the 5-10s of myrs scale. Brief episodes of elevated Corg flux tend to occur near the onset and cessation of these intervals of elevated delta 13Ccarb and delta 13Corg values; prolonged episodes of elevated Ccarb flux tend to correspond to the cessation of extended intervals of elevated delta 13C values. In the latter part of the Cenozoic, the development of beta carboxylation and C4 photosynthetic pathways in phytoplankton and terrestrial plants increasingly influenced delta 13Corg, ultimately contributing to the reversal of the long-term trend in delta 13Ccarb. Thus, the geologic record of the global carbon cycle over the past 205 myr has been influenced by a combination of changes in carbonate burial, organic carbon burial, and biological fixation.
In this paper we present data from isotopic analyses on bulk carbonates taken from Holes 390, 390A, 391C, and 392A of DSDP Leg 44. Interpre- tation of the isotopic data gives clues to recrystallization processes in sediments which have been recrystallized. Bulk carbonate data gives clues to depositional environments in samples which have not been re- crystallized (nannofossil oozes). The conclusions obtained from bulk carbonate data are not as precise as those obtained from isotope studies on individual fossils which are very rare in all samples at hand. Most samples from Holes 390, 390A, and 392A are nannofossil oozes from the Blake Plateau; no samples of the fenestral limestone were taken. We studied samples from most of the stratigraphic sequence of Hole 391C. HOLE 392A The isotopic data obtained from nannofossil ooze of Hole 3 92A give values which correspond to recrystallized carbo- nates, or to those subjected to early diagenesis in warm, aerated shallow water with little biogenic CO2. Although samples were taken at widely spaced intervals, thus preclud- ing great precision, the differences in δ O18 contents bet- ween Samples 3-2, 105 cm and 3-1, 102 cm appear to reflect changes in depositional environment: hotter waters during the middle Albian, then return to cooler conditions similar to those which prevailed in the earlier Aptian during the Campanian.
Very similar high-resolution delta13Ccarb and delta13Corg curves are reported for the early Aptian ``Livello Selli'' (LS, oceanic anoxic subevent 1a) at two pelagic successions of the Alpine Tethys: ``Roter Sattel'' (Swiss Préalpes), deposited along the northwest margin, and ``Cismon'' (southern Alps of northern Italy), deposited along the southeast margin. The delta13Ccarb and delta13Corg curves are both divided into eight segments, six of which occur within the early Aptian Globigerinelloides blowi foraminiferal zone, indicating significant subzonal resolution. Most of the LS coincides with a chemostratigraphically defined ``Selli event'': a period of constant isotopic values (mean values of delta13Ccarb and delta13Corg ~+2.60/00 and -250/00 respectively) lasting 500 kyr to 1 Myr, rather than of positive excursion as previously supposed. This uniformity may reflect an equilibrium between Corg burial and increased recycling rates of 12C and nutrient-rich intermediate water resulting from the intensification of oceanic thermohaline circulation.
A detailed carbon- and oxygen-isotope stratigraphy has been generated from Upper Cretaceous coastal Chalk sections in southern England and the British Geological Survey (BGS) Trunch borehole, Norfolk. Data are also presented from a section through the Scaglia facies exposed near Gubbio, Italian Apennines. Both the Chalk and Scaglia carbon-isotopic curves show minor positive excursions in the mid-Cenomanian, mid- and high Turonian, basal Coniacian and highest Santonian-lowest Campanian; there is a negative excursion high in the Campanian in Chalk sections that span that interval. The remarkable similarity in the carbon-isotope curves from England and Italy enables cross-referencing of macrofossil and microfossil zones and pinpoints considerable discrepancy in the relative positions of the Turonian, Coniacian and Santonian stages. The oxygen-isotope values of the various Chalk sections, although showing different absolute values that are presumably diagenesis-dependent, show nonetheless a consistent trend. Regional organic-carbon burial, documented for this period, is credited with causing drawdown of CO2 and initiating climatic deterioration. Data from other parts of the world are consistent with the hypothesis that the Cenomanian-Turonian temperature optimum was a global phenomenon and that this interval represents a major turning point in the climatic history of the earth. -from Authors
Isotopic records across the "Latest Paleocene Thermal Maximum' (LPTM) indicate that bottom water temperature increased by more than 4°C during a brief time interval (<104 years) of the latest Paleocene (~55.6 Ma). There also was a coeval -2 to -3‰ excursion in the δ13C of the ocean/atmosphere inorganic carbon reservoir. A rapid δ13C shift of this magnitude is difficult to explain within the context of conventional hypotheses for changing the mean carbon isotope composition of the ocean and atmosphere. However, a direct consequence of warming bottom water temperature from 11 to 15°C over 104 years would be a significant change in sediment thermal gradients and dissociation of oceanic CH4 hydrate at locations with intermediate water depths. In terms of the present-day oceanic CH4 hydrate reservoir, thermal dissociation of oceanic CH4 hydrate during the LPTM could have released greater than 1.1 to 2.1 × 1018 g of carbon with a δ13C of approximately -60‰. -from Authors
A comprehensive stable isotopic, trace-element, and petrographic examination of 10 cores, in the Jurassic upper Smackover Formation at Oaks field, Louisiana, suggests that early meteoric diagenesis was directly responsible for the present observed porosity distribution in the field. An isotopic and geochemical model for near-surface meteoric diagenesis based on studies of Quaternary diagenesis is fundamental to understanding the diagenetic history of the Oaks field grainstones. Near-surface meteoric diagenesis develops a characteristic isotopic and chemical signature that is easily recognized when sampled closely in stratigraphic sequence. Rocks stabilized in high-flow freshwater phreatic lens show more negative meteoric ^dgr18O values, and low values of magnesium and strontium relative to the zones above and below. Furthermore, carbon isotopic values show a trend to lighter values upward toward the subaerial exposure surface, indicating partial cementation and recrystallization in the presence of isotopically light soil gas in the vadose zone. Data from Oaks field are interpreted in light of this diagenetic model. Porous zones in Oaks field are characterized by more negative ^dgr18O values and lower magnesium and strontium content. The carbon data show a trend to lighter values toward the tops of the wells. These data suggest early mineralogic stabilization of the now-porous intervals in a high-flow, near-surface meteoric phreatic lens. Upon burial, those intervals that had been stabilized early were less susceptible to solution compaction than those intervals retaining significant proportions of unstable mineralogy. Porosity reduction through solution compaction occurred because the unstable minerals were more soluble under burial conditions than stable low-Mg calcite. These relationships are noted in all wells here porosity and permeability are well preserved.
The results presented in this paper have to be considered as a contribution to an important project whose aim is the geological study and global sequence stratigraphie correlation (multidisciplinary approach) of the Middle Oxfordian to Tithonian of different French areas, from the Sub-Boreal sections of Boulonnais, Normandy, Charente, Quercy, to the Tethyan sections of the Vocontian Trough. The review includes shallow water as well as deep water sections. The concept of this project is similar to the SE France Berriasian study published by the same working group (JAN DU CHÊNE et al., 1993). A dinocyst stratigraphie distribution chart zone is proposed between the Middle Oxfordian Transversarium Zone and the basal Upper Kimmeridgian Acanthicum of the Mesogean deep water reference sections of Vergons and Châteauneuf-d'Oze (Vocontian Trough; SE France). The two sections studied are rich in ammonites and are there-fore easily correctable with other Vocontian Trough sections to propose a sequence stratigraphic break-up primarily based on bed geometry, lithofacies and stratonomic observation, complemented by palynological and geochemical data, such as Mn content. The 3rd order sequences are stratigraphically calibrated using biostratigraphic information based on ammonites and dinocysts. From Sequence Ox 5 to Kim 3, most of the 3rd order sequences proposed by HARDENBOL et al. (1998) are stratigraphically recognised correctly with the exception of Kim 2. Data given by different geological tools as well as from other areas (particularly from the north of the Aquitaine Basin) suggest a double sequence Kim 2. To avoid any confusion with the HARDENBOL et al. cycle chart, the sequences proposed in this paper are called Kim 2' and Kim 2" respectively at the base and at the top of the interval. Correlation with the Boreal and Sub-Boreal realms are also proposed. The correlation takes into account recent papers on ammonite distribution at the Oxfordian-Kimmeridgian boundary. The joint occurrence of both Amoeboceras bauhini(a boreal species common in the base of the Baylei Zone) and Taramelliceras hauffianum (a Mesogean species) in outcrops of South Germany strongly suggests that the base of the Baylei Zone (and consequently the Oxfordian-Kimmeridgian boundary) corresponds to the base occurrence of T. hauffianum in the uppermost part of the Hauffianum subzone in the Tethyan realm. Most of the important dinocyst species have been observed in fairly comparable stratigraphic position to those known in the Boreal and Sub-Boreal realms. Additional information will be given in the near future by integrated studies presently in progress along the Upper Jurassic margins of the Aquitaine Basin (Quercy and Charente) and in Normandy.
Synsedimentary tectonics rather than autocyclic processes influenced the architecture of Oxfordian basins of northern Switzerland. Sea-floor topography constitutes swells and depressions that subsided differentially as a result of the Pan-European stress-field reorganization taking place during the Late Jurassic. Linked to the reactivation of basement faults, relief reversals during the Oxfordian led to shallow environments becoming deep, while previously rapidly subsiding areas became stable and were filled by sediments, resulting in shallow environments. Palinspastically restored facies maps and basin cross-sections reveal that the facies boundaries and depocenters were spatially related to reactivated Paleozoic faults seated in the basement. As a consequence, the assumption that the Mesozoic of northern Switzerland reflects a period of tectonic quiescence needs to be revised. Furthermore, it is evident that tectonics played a major role in defining the paleoenvironments subordinately influenced by custatic sea-level. While tectonic movements were indeed unspectacular, reinterpretation of the Oxfordian facies nevertheless clearly shows that the opening of the North Atlantic and Tethyan Oceans affected the depositional domains situated between these two areas of extension.
Distinguishes between (1) phases of "healthy' progradation and aggradation, characterized by the presence of hermatypic organisms and development of oolitic shoals, and (2) phases of "unhealthy' platform growth, typified by the absence of hermatypic organisms and the evolution of widespread crinoid, oyster, and bryozoan biostromes, as well as by increased influx of siliciclastic detritus. These environmental conditions appear to have been regulated by weathering rates on the adjacent European continent and by the increased input of detritus and nutrients. -from Authors
The manganese contents of the Oxfordian-Kimmeridgian pelagic carbonates in the section at Châteauneuf d'Oze (Vocontian Basin, Hautes Alpes, France) are used to define 11 geochemical units. These units are interpreted in terms of sequence stratigraphy and grouped into 6 third-order sequences, which then are compared with those of the sequence-chronostratigraphic chart of Hardenbol et al. (1998). Using this approach, two modifications to the chart are proposed: (i) the Oxfordian-Kimmeridgian boundary in the Tethyan realm should be set in the upper part of the Hauffianum subzone, as clearly proposed by biostratigraphic studies from Wierzbowski (1991), Atrops et al. (1993), and Schweigert and Callomon (1997). (ii) a new sequence (Kim2′) should be introduced in the Hypselocyclum zone, and the sequence Kim2″ (Hypselocyclum - Divisum zones) becomes the equivalent of the cycle chart Kim2 sequence.
A comprehensive stable isotopic, trace-element, and petrographic examination of 10 cores, in the Jurassic upper Smackover Formation at Oaks field, Louisiana, suggests that early meteoric diagenesis was directly responsible for the present observed porosity distribution in the field. Rocks stabilized in high-flow freshwater phreatic lens show more negative meteoric delta¹â¸O values, and low values of magnesium and strontium relative to the zones above and below. Furthermore, carbon isotopic values show a trend to lighter values upward toward the subaerial exposure surface, indicating partial cementation and recrystallization in the presence of isotopically light soil gas in the vadose zone. Data from Oaks field are interpreted in light of this diagenetic model. Porous zones in Oaks field are characterized by more negative delta¹â¸O values and lower magnesium and strontium content. The carbon data show a trend to lighter values toward the tops of the wells. These data suggest early mineralogic stabilization of the now-porous intervals in a high-flow, near-surface meteoric phreatic lens. Upon burial, those intervals that had been stabilized early were less susceptible to solution compaction than those intervals retaining significant proportions of unstable mineralogy. Porosity reduction through solution compaction occurred because the unstable minerals were more soluble under burial conditions than stable low-Mg calcite. These relationships are noted in all wells where porosity and permeability are well preserved. 12 figures.
The commonly used phosphoric acid procedure for the determination, of oxygen isotope abundances in carbonates involves a large kinetic isotope effect. The value of the fractionation factor, , defined as: has been measured for several alkaline earth and transition metal carbonates. The value of 1000 In ranges from 9.9 to 11.2. The previously used assumption that calcite and dolomite have the same value of a leads to an overestimate of the dolomite-calcite oxygon isotope fractionation by 0.8 per mil.
Two pelagic limestone sections in the Southern Alps spanning the Kimmeridgian (Late Jurassic) to Barremian (Early Cretaceous) interval yield magnetostratigraphies which can be correlated to oceanic magnetic anomalies M1-M3 and M8-M23. This includes the interval M11-M13 which has not previously been correlated to a sedimentary section. Detailed investigations of nanofossils and calpionellids in these sequences allow precise correlation of polarity chrons to biostratigraphic events and these results compare favorably to those of previous studies. The close correspondence in polarity pattern between that interpreted from the M8 to M15 interval in the Hawaiian lineations and that recorded at the Capriolo section, suggests that sedimentation rates in this sequence and spreading rates in the Hawaiian lineations were rather constant during this interval. In contrast, the sedimentation rate at the Xausa section appears to increase up-section with the facies transition from the Rosso Ammonitico to the Maiolica Formation.
Petrographic and cathode luminescence studies of Alpine ophicalcites are combined with stable isotope data of pelagic sediments and associated ophiolite relicts, to document multiple phases of fluid-rock interaction related to sea-floor processes and Alpine orogeny. Internal sediments and primary carbonate microstructures in ophicalcites provide evidence for early sea-floor fragmentation, cementation and fluid activity in the Jurassic Tethys. Ca-carbonate cementation is comparable to cementation in modern transform setting analogues, where alkaline and Ca-enriched fluids are associated with serpentinites. Local mineralization and isotopic compositions of serpentine in ophicalcites are interpreted as signs of hydrothermal activity at temperatures of 100–150 °C.
Differences in the degree of oxygen isotope re-equilibration reflect differences in fluid/rock interaction during Alpine accretionary tectonics and continent-continent collision. Regional-scale homogenization of oxygen isotopes in carbonates and cherts indicate the presence of pervasive metamorphic fluids in the pelagic sediments during early Alpine recrystallization. In contrast, a lack of oxygen isotope re-equilibration in serpentine may reflect lower permeabilities and more limited fluid flow in serpentinites during Alpine metamorphism. Cathode luminescence and preliminary oxygen isotope data of late vein-forming phases suggest that late metamorphic fluids were channelled along discrete brittle fractures in a closed, rock-dominated system.
Investigation of four sections of Tithonian to Valanginian pelagic limestone have led to refinement of the correlation of calpionellid zones to the magnetic polarity time scale. The correlations are self-consistent but differ slightly from those previously published. The discrepancy with the published correlation from the Bosso section [1] has been resolved by re-evaluation of the biostratigraphy of this sequence. The revised correlation places the base of the Chitinoidella Zone in the lower part of polarity chron CM21n, the base of Zone A near the top of CM20n, the A/B boundary at the base of CM18, the B/C boundary in the upper part of CM17, the C/D boundary at the top of CM16 and the D/E boundary at the top of CM14.
There were three negative seawater strontium-isotope excursions (shifts to lower 87Sr/86Sr values) during the Jurassic and Cretaceous that were of relatively short duration (5-13 my) and showed a relatively quick recovery to pre-excursion 87Sr/86Sr ratios. These excursions occurred in the Pliensbachian-Toarcian (Early Jurassic), Aptian-Albian, and Cenomanian-Santonian (Early and Late Cretaceous respectively). Each excursion coincided closely in time with an Oceanic Anoxic Event (OAE) marked by sediments unusually rich in organic carbon. The Jurassic OAE occurred at the end of the strontium-isotope excursion, whereas the two Cretaceous OAEs occurred at the onset of the accompanying strontium-isotope excursions. The possible causes of these excursions were evaluated by successively examining the changes in the riverine strontium fluxes, riverine 87Sr/86Sr ratios, or hydrothermal strontium fluxes required to produce each excursion. A range of seawater strontium budgets was used to encompass the uncertainties in modern and ancient cycles. To produce the excursions, we calculate that the riverine strontium fluxes would have had to decrease by 6 to 15 percent or the fluvial 87Sr/86Sr ratios by 0.00019 to 0.00046. The uncertainties largely stem from the assumed magnitude of the hydrothermal strontium flux at the onset of each excursion. Alternatively, increases in sea-floor hydrothermal activity of 7 to 104 percent could also have produced the strontium-isotope excursions. This large range is due mostly to uncertainties in the relative flux of strontium from axial high-temperature hydrothermal systems and low-temperature off-axis systems. Only a small portion of this range stems from uncertainties in the riverine strontium terms. The possible causes of the excursions were further evaluated by examining several geologic factors that could have affected riverine strontium, including climate change, sealevel, and the eruption of flood basalts. We conclude that neither variations in riverine strontium fluxes nor in 87Sr/86Sr ratios is the likely cause of the strontium-isotope excursions. The most probable explanation is increased rates of hydrothermal activity related to increased ocean-crust production at the mid-ocean ridges. The close correlation in time between the strontium-isotope excursions and the major Oceanic Anoxic Events (OAEs) is compatible with a causal linkage. We propose that increased ocean-crust production led to enhanced CO2 outgassing and global warming, which in turn led to several processes that acted to make surface ocean waters more productive. However, because OAEs did not occur throughout the proposed periods of enhanced hydrothermal activity, it appears that these processes only preconditioned the oceans for the OAEs: sealevel rise may have been the final trigger. This model explains why all three OAEs did not occur at the same time relative to the onset of excess hydrothermal activity and why OAEs are not associated with every sealevel rise documented in the stratigraphic record.
Four Late Jurassic carbonate successions deposited in the Tethys-Atlantic Ocean record a negative carbon isotope excursion of at least 20/00. The excursion is present in both organic and carbonate carbon records and is comparable in magnitude and duration to isotopic changes during the late Paleocene thermal maximum. Our results indicate that during the Late Jurassic, long considered a warm greenhouse time, additional greenhouse gas was input to the atmosphere by a sudden release of methane from buried gas hydrate. A potential triggering mechanism may have been the opening of an oceanic gateway through the early Atlantic between the ancient Tethys and Pacific Oceans.
The Liesberg Beds form the transition between the lower Oxfordian dark coloured marls and the middle Oxfordian reefal limestones. Carbon isotope compositions of crinoid stems of Millericrinus spp and echinoid spines of Paracidaris spp were used as an isotopic marker because of their abundance throughout the section and the small variations of δ13C within one fossil and between fossils from the same stratigraphic level. The heavy δ13C values (≃2-2.3‰) in the lower Liesberg Beds are interpreted as a transition from an oxygen-limited environment to the Liesberg Beds Member. The lowest δ13C values (≃1-1.5‰) correspond to a large input of dissolved nutrients to the platform under oxidizing conditions. The ensuing positive shift however, seems to correspond to a general trend of opening up of the platform and connection to open marine waters. Positive δ13C values in the upper Liesberg Beds are interpreted as a result of important accelerated extraction of organic carbon from the ocean reservoir, that occurred possibly during periods of warm and humid climate. -from Authors
Significant short-term carbon isotope fluctuations are present in Cretaceous pelagic limestones from widely distributed onshore sections in the Circum-Atlantic-western Tethyan region. More than 1000 closely spaced samples were analyzed during this study. At least seven major delta/sup 13/C excursions can be correlated from section to section. The most important heavy events occur near the Aptian-Albian and Cemonanian-Turonian boundaries, whereas light events are near the Jurassic-Cretaceous, Albian-Cemonanian, Turonian-Coniacian, and Cretaceous-Tertiary boundaries. The association of events with stage boundaries and the consistent correlation of events between stratigraphic sections provides a significant new tool for time-rock correlation independent of standard biostratigraphic techniques. The temporal association of these carbon isotope events with stage boundaries (faunal and floral events), global eustatic sea-level variations, and oceanic anoxic events demonstrates the potential usefulness of carbon isotope studies in interpreting variations in paleo-oceanic circulation. Furthermore, the association of carbon isotope variations with anoxic events is potentially useful for evaluation of the precise timing and the magnitude of preservation of organic matter in deep-sea and continental-margin sediments. Thus, isotopic studies may aid in estimating potential hydrocarbon resources in largely unexplored oceanic basins or along continental margins. 12 figures, 1 table.
The carbon isotope record in four pelagic carbonate sections from the
Southern Alps (northern Italy) across the Jurassic-Cretaceous boundary
has been correlated to biostratigraphy and magnetostratigraphy. The
carbon isotope curve from bulk carbonates shows a decrease from
Kimmeridgian to Early Tithonian (CM24-CM22) values of
δ13C=+2.07 (± 0.14)‰ to Late Tithonian
and Berriasian (CM18-CM14) values of δ13C=+1.26
(± 0.16)‰. The change in the carbon isotope record
coincides with changes in Tethyan calcite and silica accumulation rates,
with a drop in the calcite compensation depth in the Atlantic and Tethys
oceans and with changes in organic carbon burial along the Eurasian
margin of the Tethys. Reduced surface water productivity due to
diminished transfer rates of biolimiting elements into the Atlantic and
Tethys oceans can explain these observations. The decreased transfer
rates of elements such as silica or phosphorus from continents into the
oceans resulted from drier climatic conditions and decreased water
runoff on continents bordering the Tethys and Atlantic oceans. The
proposed changes in Tithonian - Berriasian ocean chemistry and
paleoclimate suggest that variations in the global carbon cycle were
coupled with changes in the global hydrological cycle and in associated
material cycles.
The Early Cretaceous carbonate carbon isotope stratigraphy established in pelagic limestones is marked by several pronounced excursions towards positive δ13C values. We investigated a biostratigraphically and palaeomagnetically calibrated Aptian section to see whether C isotope stratigraphy could be recognized in shallow-water carbonates. The chosen carbonate platform sections are located in southern Italy and have been dated by biostratigraphy. Bulk samples, chosen from the Barremian-Albian part of the sequence, were analysed for their O and C isotope compositions. The C isotope curve established shows two major positive excursions which can be correlated with the synchronous and globally recognized Aptian C isotope events. The data provide evidence that C isotope stratigraphy can be used as a powerful correlation tool between pelagic and shallow-water limestone sequences.
Studies on Cretaceous pelagic limestones have shown a close correspondence between putative sea-level curves and the carbon-isotope profile, suggesting a possible relationship between the two phenomena. Such a relationship could relate to shelf-sea area governing the global burial rate of organic carbon which, in turn, controls the 13C/12C ratio of dissolved inorganic carbon in the oceanic reservoir. In order to see whether or not this relationship might be of more general applicability, the major mid-Oxfordian (Jurassic) transgression is documented to zonal level and appropriate carbon-isotope data are presented. Although the applicability of ammonite zonation to the mid Oxfordian is problematic on a regional scale, a clear δ13C excursion is present in the trunsversariurn Zone, which is coincident with regional overstep and/or evidence of shoreline retreat and/or evidence of bathymetric deepening in Europe and elsewhere. The use of the carbon-isotope curve as a proxy for shelf-sea area or relative sea level is worthy of further exploration.
Jurassic radiolarians are sensitive to palaeoclimatic–palaeoceanographic changes, recorded by the stable carbon-isotope curve. Carbon-isotopic variations have been linked to changes in ocean structure, productivity and concentrations of greenhouse gases in the atmosphere. In the Middle–Upper Jurassic Terminilletto section of the Umbria–Marche–Sabina Apennines (central Italy), well preserved radiolarians are present in a sequence of cherty limestones interbedded with platform-derived carbonates. The δ13C curve in the Aalenian–Kimmeridgian interval indicates three main positive δ13C `events' in the lower Bajocian, late Bathonian–lower Callovian and middle Oxfordian. The positive δ13C shifts are correlated to increases in visible chert in the outcrop and may represent periods of increased biological productivity of surface sea-water. Spumellaria/Nassellaria ratios and the fluctuations of relative abundance of selected genera tend to correlate with δ13C and chert abundance values, and seem to be related to episodes of high nutrient mobilisation. From the base of the Bajocian, the radiolarian associations show a slight tendency towards diversification, coincident with increasing δ13C values. In the upper part of the middle Bajocian, last appearances prevail over first appearances associated with the peak of the δ13C event. This may indicate maximum eutrophic conditions. Coincident with the late Bathonian–early Callovian positive δ13C shift, the radiolarian associations record a different trend with respect to the Bajocian event. When the δ13C values are increasing to a maximum, radiolarian associations tend to be reduced in species diversity, followed by a small diversification trend when the δ13C values are decreasing. We speculate that during the Callovian a more `stressful' palaeoenvironment, due to high level of eutrophication, is indicated by the combination of high productivity of biogenic silica and low carbonate input. Although varying preservational conditions may have influenced the observed trends in the radiolarian associations, the good correlation between changes of sedimentation patterns, radiolarian assemblages and δ13C positive anomalies, open interesting avenues for further investigations concerning the palaeoecology of Mesozoic radiolarians.
The climate of the Late Jurassic has been characterized by high atmospheric CO2 levels and by a monsoonal rainfall pattern. In this study we traced the evolution of the global carbon cycle through the Late Jurassic with the help of carbonate carbon isotope stratigraphy. The Oxfordian-Tithonian δ13C curve is marked by one major positive carbon isotope excursion with an amplitude (Middle to Late Oxfordian) and a second, minor positive excursion with an amplitude (Late Kimmeridgian). The Early Kimmeridgian and Early Tithonian δ13C-values fluctuate around and contrast with the less positive δ13C-values of Early Oxfordian and Late Tithonian age (). A comparison of the Late Jurassic carbonate carbon isotope curve with the occurrence of organic-rich sediments suggests that not only fluctuations in organic carbon burial but also in carbonate carbon burial had an impact on the C-isotope record. The Oxfordian C-isotope excursion appears to correspond to a time of overall increased organic carbon burial triggered by increased nutrient transfer from continents to oceans during a time of rising global sea level. However, episodes of enhanced organic carbon burial during the Kimmeridgian and Early Tithonian are not reflected by prominent spikes in the C-isotope record. Favourable conditions for carbonate platform growth at a time of high global sealevel may have resulted in the stabilisation of the C org/C carb burial ratio and hence maintained the δ13C record at steady but relatively positive values. The Middle and Late Tithonian C-isotope values drop below . A similar shift to less positive C-isotope values was recognized in other C-isotope records from the Tethys and Atlantic Oceans and reflects a decrease in the C org/C carb burial ratio possibly related to a reorganisation of the global climate system.Globally widespread marine black shale-mature quartzose sandstone assemblages suggest that the relative efficiency of the Late Jurassic carbon pumps was controlled by weathering, erosion and runoff causing widespread marine eutrophication. Eutrophication favoured the organic carbon pump but it diminished the carbonate-platform growth potential. The monsoonal rainfall distribution pattern may explain why Late Jurassic carbonate platforms experienced less severe growth crises than Early Cretaceous carbonate platforms.
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