Article

Influence of Oceanic Anoxic Events on the evolution of mid-Cretaceous Radiolaria in the North Atlantic and Western Tethys

March 1997
Marine Micropaleontology 30(1-3):139-158

March 1997
30(1-3):139-158

Authors:

Bundesanstalt für Geowissenschaften und Rohstoffe

Mid-Cretaceous (Aptian-Turonian) extinction/radiation events of radiolaria from the North Atlantic and western Tethys are summarized in relation to Oceanic Anoxic Events (OAE) from investigations of radiolarian faunas, black shales and stable carbon isotopes. Extinction and radiation events of radiolaria can be observed from the late early Aptian, the earliest Albian, the latest Albian and the Cenomanian/Turonian boundary.These events correlate well with organic carbon-rich sediments that contain type II kerogen and show positive δ13C excursions. They correspond to the Oceanic Anoxic Events (OAE) in the early Aptian (OAE 1a, Selli Level), early Albian (OAE 1b), late Albian (OAE 1d) and latest Cenomanian (OAE 2, Bonarelli Level). Detailed investigations of the two most significant events, the Selli and the Bonarelli Level in the Umbria-Marche Basin of central Italy show that extinctions coincide with the first occurrence of marine black shales (type II kerogen) and the most prominent rise of δ13Corg values. Stepwise extinctions and continuous radiations precede and follow the events. Similar patterns are evident for the OAE 1b and 1d. Black shales dominated by terrestrial organic matter (type III kerogen e.g., OAE 1c) are not characterized by isotopic excursions or by radiolarian extinction/radiation events.Contemporaneous drowning events documented from carbonate platforms around the investigated basins provide a link to a model where flooding of lowlands and leaching of nutrients during a relative rise of sea-level lead to an increased productivity and an expansion of the oxygen minimum zone (OMZ). Because of the loss of deep habitats, deeper dwelling forms become extinct. Shallower dwelling radiolarians survive. A narrowing of the OMZ during highstands and relative sea-level falls together with a coupled decrease of the nutrient supply leads to the development of new niches and therefore to radiation.

THE ECOLOGICAL RESPONSE OF PLANKTON TO MAJOR MESOZOIC AND CENOZOIC CLIMATE EVENTS

Conference Paper

Jan 2021

Marine depositional signatures of the Aptian Oceanic Anoxic Events in the Eastern Tethys, Lower Indus Basin, Pakistan

Article

Aug 2021

The depositional signatures of the Cretaceous OAE1a and OAE1b intervals in the Parh Formation, Lower Indus Basin, Pakistan, Eastern Tethys, have been studied to better constrain the Aptian–Albian ocean–climate system. Based on the microfacies attributes, an outer ramp to deep basin is suggested for the deposition of Parh Formation. The quasi-periodic occurrences of radiolarian-rich microfacies and the cyclicity between the outer ramp and deep basin settings throughout the section suggest eutrophication in this part of the Eastern Tethys influenced by Milankovitch cycles. The clastic influx during OAE1a and OAE1b intervals indicate the role of continental runoff in the eutrophication of the basin. The overall negative covariance between radiolarian-rich microfacies and clastic input suggests that upwelling was a major driver of nutrient enrichment rather than continental runoff. The organic enrichment along with pyrite framboids and lack of burrows suggest that dysoxic–anoxic bottom water conditions were common throughout the Aptian and not just in the OAE1a and OAE1b intervals. The poor ventilation of the sea floor was a result of restricted circulation and may have triggered sustained anoxia during Aptian in this part of the Eastern Tethys. Bottom-water currents recharged coarser clastics to the deeper part of the basin during OAE1a and OAE1b intervals. However, the effects of deep ventilated oxic water during the events were reduced by persistent ocean anoxia. Furthermore, the dominance of carbonate sediments throughout the Aptian–lower Albian succession suggests relatively alkaline oceans in this part of Eastern Tethys. A pronounced sea-level rise, as suggested elsewhere was not observed during OAE1a and OAE1b intervals in this part of the Tethys. • KEY POINTS • The Aptian–Albian hemipelagic sequence of the Parh Formation, Lower Indus Basin, Pakistan, Eastern Tethys has been deposited in an outer ramp to deep basin environment. • The quasi-periodic occurrences of radiolarian-rich microfacies and cyclic alternation of depositional environments suggest eutrophication of the basin influenced by Milankovitch cycles. • Organic enrichment, pyrite framboids and lack of burrows suggest dysoxic–anoxic bottom-water conditions throughout the Aptian to early Albian.

Paleoenvironmental changes and biotic response to Aptian–Albian episodes of accelerated global change: Evidence from the western margin of the proto-North Atlantic (central-eastern Mexico)

Article

May 2021
CRETACEOUS RES

The Aptian-Albian interval represents a time of distinctive atmospheric and oceanic changes. A major perturbation of the carbon cycle induced by intense volcanic activity produced episodes of environmental change affecting the abundance and evolution of marine plankton. Several studies based on pelagic and hemipelagic sections have used biostratigraphic events and carbon isotope stratigraphy tools to identify biotic responses to environmental perturbations. Few studies have included Aptian-Albian planktic microfossil communities and paleoenvironmental changes in Mexico, a region that was part of the western proto-North Atlantic margin. The aim of this study is to interpret paleoenvironmental and paleoceanographic conditions through a microfacies analysis of a carbonated succession of the Tamaulipas Formation from central-eastern Mexico (Tampico-Misantla Basin), within a temporal framework based on planktic foraminiferal and colomiellids biostratigraphy. The studied section, 92 m thick, consists of a continuous pelagic succession. Facies contain abundant planktic microfossils and span the stratigraphic interval between the Globigerinelloides blowi and Ticinella praeticinensis Zones. The Aptian/Albian Boundary in the studied section was established on the highest occurrence (HO) of planktic foraminifera such as Paraticinella rohri and the presence of Microhedbergella spp., followed by the LO of colomiellids such as Colomiella recta. Detailed quantification of microfossil assemblages reveals variations in abundance of planktic foraminifera, radiolarians, praecolomiellids, colomiellids, dinocyst and echinoderm fragments. These variations related to fabric characterization and bioturbation indexes allow us to infer fluctuations in ancient trophic conditions in the water column, which might be associated with episodes of global environmental change such as Oceanic Anoxic Events.

PLANKTONIC FORAMINIFERAL BIOSTRATIGRAPHY OF LATE ALBIAN- CENOMANIAN PELAGIC SEQUENCES FROM THE UMBRIA-MARCHE BASIN (CENTRAL ITALY) AND THE MAZAGAN PLATEAU (NORTHEAST ATLANTIC OCEAN)

Article

Full-text available

Nov 2020

appearance of new lineages is observed throughout the Albian and Cenomani-an. The middle-late Albian is marked by the appearance of trochospiral genera characterized by finely perforate to macroperforate shell perforations and thick (genus Ticinella) to muricate (genera Muricohed-bergella, Praeglobotruncana) wall textures, by muricate to smooth planispiral taxa (genus "Globigerinelloides", see Taxonomic Remarks) with also peripheral keel (genus Planomalina), and by the appearance of biserial taxa Abstract. Planktonic foraminifera were studied in the upper Albian to Cenomanian sedimentary sequence of the Monte Petrano and Le Brecce stratigraphic sections located in the Umbria-Marche Basin (central Italy), and of Hole 547A and Site 545 drilled by the Deep Sea Drilling Project (DSDP) on the Mazagan Plateau (offshore Morocco, northeast Atlantic Ocean). Biostratigraphic results allow the identification of a stratigraphically ordered sequence of bioevents that have proved to be reliable for regional and interregional correlations, from older to younger: the lowest occurrences (LOs) of Th. appenninica, Pl. buxtorfi, Pa. libyca, Th. brotzeni in the Albian, and the LOs of Th. globotrunca-noides, Th. greenhornensis and Rt. cushmani in the Cenomanian sediments. We remark the difficulty in the identification of the Th. reicheli Zone used in the Tethyan biozonation because of the rarity and absence of the species in many low to mid-latitude pelagic sequences. To overcome the problem, we use the Th. greenhornensis Zone defined as the strati-graphic interval between the lowest occurrence (LO) of Th. greenhornensis and the LO of Rt. cushmani. The LO of Th. greenhornensis is a solid bioevent with the nominal species characterized by a wide geographic distribution and occurring close to the LO of Th. reicheli where the latter species is present. The studied stratigraphic sections are compared with the coeval Mont Risou section in the Vocontian Basin and the record from Blake Nose in the western North Atlantic to verify the correlation and synchronicity of biostra-tigraphic and chemostratigraphic events including the Oceanic Anoxic Events 1d (OAE1d) and the Mid Cenomanian Event (MCE).

PLANKTONIC FORAMINIFERAL BIOSTRATIGRAPHY OF LATE ALBIAN- CENOMANIAN PELAGIC SEQUENCES FROM THE UMBRIA-MARCHE BASIN (CENTRAL ITALY) AND THE MAZAGAN PLATEAU (NORTHEAST ATLANTIC OCEAN)

Article

Jan 2000

Maria Rose Petrizzo

Ecological Response of Plankton to Environmental Change: Thresholds for Extinction

Article

Full-text available

May 2020

Severe climatic and environmental changes are far more prevalent in Earth history than major extinction events, and the relationship between environmental change and extinction severity has important implications for the outcome of the ongoing anthropogenic extinction event. The response of mineralized marine plankton to environmental change offers an interesting contrast to the overall record of marine biota, which is dominated by benthic invertebrates. Here, we summarize changes in the species diversity of planktic foraminifera and calcareous nannoplankton over the Mesozoic–Cenozoic and that of radiolarians and diatoms over the Cenozoic. We find that, aside from the Triassic–Jurassic and Cretaceous–Paleogene mass extinction events, extinction in the plankton is decoupled from that in the benthos. Extinction in the plankton appears to be driven primarily by major climatic shifts affecting water column stratification, temperature, and, perhaps, chemistry. Changes that strongly affect the benthos, such as acidification and anoxia, have little effect on the plankton or are associated with radiation. ▪ Fossilizing marine plankton provide some of the most highly temporally and taxonomically resolved records of biodiversity since the Mesozoic. ▪ The record of extinction and origination in the plankton differs from the overall marine biodiversity record in revealing ways. ▪ Changes to water column stratification and global circulation are the main drivers of plankton diversity. ▪ Anoxia, acidification, and eutrophication (which strongly influence total marine fossil diversity) are less important in the plankton. Expected final online publication date for the Annual Review of Earth and Planetary Sciences, Volume 48 is May 29, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

RADIOLÁRIOS DO CRETÁCEO MÉDIO DAS BACIAS DO PARÁ-MARANHÃO E BARREIRINHAS, MARGEM EQUATORIAL BRASILEIRA

Thesis

Full-text available

Aug 2023

Vladimir de Souza

Cretaceous radiolarians from the Siquisique Ophiolite (northern Venezuela) – A solved problem and an open question

Article

Apr 2023
J S AM EARTH SCI

The Siquisique Ophiolite is one of the few remnants of the proto-Caribbean Seaway. Located in northern Venezuela, in the border between Lara and Falc´on states. At Los Algodones, the type locality, the ophiolite is composed of cumulate gabbros, basalts, and stratigraphically overlying dark cherts. Mafic complexes identical to Siquisique have been identified in three other localities of northern Venezuela: the extended outcrop of Chorrerones-Macure, and the reduced outcrops of Llanaditas and Limon. A previous study reported Bajocian–Bathonian ammonites in inter-pillow sediment of basalt blocks from Las Petacas Creek in Los Algodones area. These ammonites were associated with the Siquisique Ophiolite, hence considered as a remnant of the Jurassic proto-Caribbean seaway. However, recent detailed geological mapping has shown that these ammonites are associated with basaltic blocks of unknown origin embedded in a Paleogene-Eocene turbidites (Matatere Formation). Radiolarians recovered in a black chert sample obtained from the Middle Jurassic ammonite locality yields a Bajocian-Bathonian age. Thus, the Middle Jurassic age given by ammonites and radiolarians could reflect the presence of older deposits that are not part of the Siquisique Ophiolite. Aditionally, poorly preserved radiolarians were recovered in a green to black laminated ribbon bedded cherts of the Guaparo creek area (Chorrerones-Macuere), in stratigraphic contact with basaltic breccias. The determined assemblage includes Parvimitrella communis (Squinabol), Dictyomitra sp. cf. D. multicostata, Dictyomitra sp. cf. D. communis, Dictyomitra sp., Diacanthocapsa sp., Praeconocaryomma sp., Archaeodictyomitra sp., Rhopalosyringium sp. aff. R. fossile, indicating a Cretaceous (Albian–Coniacian) deposit.

Geochemical factors associated with deposition of lower Aptian organic-rich sediments during OAE1a in the Basque-Cantabrian Basin, northern Spain

Article

Full-text available

Mar 2023

Introduction: The Early Aptian Oceanic Anoxic Event 1a (OAE1a) is characterized by organic matter (OM) bearing rocks identified worldwide, which also occur in the hemipelagic succession of the Cuchía section, North Basque-Cantabrian Basin (NBCB) in Northern Spain. Previous works identified OAE1a using δ13C calibrated with biostratigraphy of planktonic foraminifera, calcareous nannoplankton, and ammonites. However, the geochemical characteristics that controlled OM sources and the redox conditions during OAE1a are yet to be determined. Therefore, here we present the results of a high-resolution complementary study along 67 m of the succession at Playa de los Caballos beach that highlights how local factors in the basin modulated the effects of increased precipitation during enhanced global hydrological cycles. Methods: Samples were analyzed for total inorganic carbon (TIC), total organic carbon (TOC), δ13C, major elements (Al, Ti, Si), redox sensitive trace elements (RSTEs), clay mineralogy, bulk mineralogy, and biomarkers. Results and Discussion: Carbon isotope segments C2 to C6 were recognized to determine the age of the outcrop. Lipid biomarkers indicated that OM is predominantly marine with significant terrestrial contribution. Terrigenous OM was carried to the basin through pulses of fluvial input as attested by the major elements and by high relative proportions of quartz, feldspar, and clay minerals. Increased terrestrial inputs also enhanced primary production and facilitated OM preservation. Periods with hightened RSTE content correspond with increases in the major elements, thus implying their common provenance. High sedimentation rates together with the presence of less labile OM and the interaction with clay minerals most likely played a major role in preserving the OM. This study further highlights how enhanced hydrological cycles significantly influenced the marine conditions that controlled the expression of OAE1a in the NBCB.

Comparison of mid-Cretaceous (Cenomanian–Turonian) high-latitude palynofloras from Patagonia and New Zealand: Richness, ecology, and provincialization

Article

Sep 2022
PALAEOGEOGR PALAEOCL

The Cenomanian–Turonian is considered the warmest interval of the last 150 million years. It was characterized by major disturbances to the global carbon cycle, resulting in elevated pCO2 levels and global temperatures, and witnessed the rise to dominance of angiosperms floras. In this paper, we assess changes of fossil floras during the Cenomanian–Turonian interval based on palynological studies of two distantly-spaced localities in high southern paleolatitudes: the Mata Amarilla Formation of Patagonia, southern South America and the Tupuangi Formation of the Chatham Islands, New Zealand. Richness estimations for each stratigraphic unit and cluster analysis were conducted to assess the vegetation changes. Palynological dominance and the presence/absence of taxa were compiled for these units and compared with others from the Cenomanian of southern Gondwana. We recognize a peak in richness during the Mid-Cenomanian Event in Patagonia, with a fall in richness after the event due to species being displaced by dominant taxa. Several richness peaks are also recognized in New Zealand, but the lack of stratigraphic control prevents correlation with marine-based events. Oceanic Anoxic Event 2 is not recorded in either study area. The inclusion of Gondwanic palynological records demonstrate that the Tupuangi Formation cluster with sites from the Antarctic Peninsula and south-eastern Australia conforming a ‘polar cluster’. However, this area has its own palynological signature, constituting a newly proposed Taxodiaceaepollenites Subprovince. The abundances of key plant groups of the Mata Amarilla Formation cluster with those of Bathurst Island (northern Australia), but also show important differences, likely owing to their geographic separation and latitudinal difference. This work actualizes the Southern Gondwana palynological provinces scheme for the mid-Cretaceous and provides novel data sets for Patagonia and New Zealand which can be use as reference on palynological and paleoecological studies of coeval floras worldwide.

Albian-Cenomanian depositional cycles transgressed from Chihuahua trough to Western Interior

Conference Paper

Jan 2001

First Record of Oceanic Anoxic Event 1d at Southern High Latitudes: Sedimentary and Geochemical Evidence From International Ocean Discovery Program Expedition 369

Article

Full-text available

May 2022
GEOPHYS RES LETT

Oceanic anoxic event 1d (OAE 1d) has been well studied at northern low latitudes (i.e., in Tethys and the North Atlantic); however, the paleoenvironmental response to this event at high latitudes has not been documented and the triggering mechanism remains unknown. Here, we address both of these shortcomings by presenting the first detailed sedimentary and multi‐proxy geochemical record of the OAE 1d at southern high latitudes (60–62°S), obtained from sediments using Site U1513, IODP Expedition 369. Biostratigraphic and chemostratigraphic data support correlation of the interval studied with OAE 1d, and the sedimentary mercury proxy reveals that at least at Site U1513, OAE 1d is associated with the Central Kerguelen large igneous province volcanism. Furthermore, the significant increase in continental runoff and consequent terrigenous input from southwestern Australia in the southeastern proto‐India Ocean might have resulted in regionally weakened bottom‐water oxygenation and strengthened organic matter burial during OAE 1d.

Late Cretaceous Paleoceanographic Evolution and the Onset of Cooling in the Santonian at Southern High Latitudes (IODP Site U1513, SE Indian Ocean)

Article

Full-text available

Jan 2022

The latest Cenomanian to Santonian sedimentary record recovered at IODP Expedition 369 Site U1513 in the Mentelle Basin (SE Indian Ocean, paleolatitude 60°S at 85 Ma) is studied to interpret the paleoceanographic evolution in the Southern Hemisphere. The planktonic foraminiferal assemblage changes, the depth ecology preferences of different species, and the surface and seafloor temperature inferred from the stable isotopic values measured on foraminiferal tests provide meaningful information to the understanding of the Late Cretaceous climate. The hothouse climate during the Turonian‐Santonian, characterized by weak latitudinal temperature gradients and high atmospheric CO2 concentrations, is followed by a progressive cooling during the Campanian. At Site U1513 the beginning of this climatic transition is nicely recorded within the Santonian, as indicated by an ∼1‰ increase in δ¹⁸O values of planktonic foraminifera suggesting a decline in surface water paleotemperatures of 4°C. The onset of cooling is mirrored by changes in the planktonic foraminiferal assemblages including extinctions among surface and deep dwellers, appearances and diversification of newly evolving taxa, and changes from predominantly epifaunal oxic to infaunal dysoxic/suboxic taxa among co‐occurring benthic foraminifera. Overall, the data presented here document an interval in the Santonian during which the rate of southern high latitude cooling increased. Both surface and bottom waters were affected, although the cooling signal is more evident in the data for surface waters. This pattern of cooling ascribes the deterioration of the Late Cretaceous climate to decreased CO2 in the atmosphere and changes in the oceanic circulation correlated with enhanced meridional circulation.

Exploring the paleoceanographic changes registered by planktonic foraminifera across the Cenomanian-Turonian boundary interval and Oceanic Anoxic Event 2 at southern high latitudes in the Mentelle Basin (SE Indian Ocean)

Article

Full-text available

Aug 2021
GLOBAL PLANET CHANGE

Planktonic foraminiferal population dynamics and benthic foraminiferal and radiolaria distributions combined with δ¹³C and δ¹⁸O measurements of both bulk carbonate and foraminifera provide clues concerning the paleoceanographic changes across the Cenomanian-Turonian boundary interval and the Oceanic Anoxic Event 2 (OAE 2) at southern high latitudes. Samples analyzed are from Integrated Ocean Discovery Program (IODP) Expedition 369 Site U1516 in the Mentelle Basin (eastern flank of the Naturaliste Plateau, Indian Ocean, SW Australia). Site U1516 was located at 60°–62°S paleolatitude during the mid-Cretaceous, and it is the first high latitude locality in the Southern Hemisphere where planktonic foraminifera are consistently recorded across the OAE 2 interval and its associated positive δ¹³C excursion. The sedimentary record at Site U1516 consists of a sequence of alternating black, dark greenish gray, and light greenish gray claystone in the Cenomanian that grade to white and light gray calcareous chalk interbedded with chert in the Turonian. The correlation between the δ¹³C and δ¹⁸O profiles at Site U1516 and the European reference section at Eastbourne (England) coupled with the integrated calcareous plankton biostratigraphy and stable isotopic data at Site U1516, indicate that a complete record of OAE 2 at Site U1516 was recovered. Below and in the lower part of OAE 2, the planktonic foraminiferal assemblages are dominated by small-sized (125–38 μm) opportunistic species of Microhedbergella and radiolaria indicating a dominantly eutrophic regime. Above the onset of OAE 2, a trough in the δ¹³C profile (Plenus Carbon Isotope Event: P-CIE) coinciding with a δ¹⁸O increase may correspond to the Plenus Cold Event as observed at low latitudes, although no evidence of cooling is registered in the microfossil assemblages. At Site U1516, the middle part of OAE 2 at the initiation of the plateau phase of the δ¹³C profile is masked by absence of carbonate, by the highest TOC values, and high biogenic silica (dominance of radiolaria) indicating this interval corresponded to a time of highly stressed eutrophic conditions with possible shoaling of the Carbonate Compensation Depth (CCD). Above this interval, bulk isotopic results yield lower δ¹³C values, and the CaCO3 increases are associated with the presence of even smaller-sized Microhedbergella showing cyclic fluctuations in absolute abundances with benthic foraminifera indicating dominantly eutrophic conditions likely affected by upwelling of nutrient-rich and δ¹³C-depleted intermediate water masses. Toward the top of OAE 2 and across the Cenomanian-Turonian boundary interval, the planktonic foraminiferal assemblages show changes in composition (e.g., Microhedbergella is replaced by Muricohedbergella), species occupying relatively deep ecological niches appear and an overall increase in diversity is observed. These features coupled with the foraminiferal species-specific δ¹³C and δ¹⁸O patterns reveal that Site U1516 occupied a paleoceanographic setting still affected by eutrophy likely related to enhanced input of nutrients but with episodes of stability with ecological/thermal separation in the surface waters. This interval also records the highest sea surface water paleotemperatures values estimated as 20°–23°C based on δ¹⁸O values of foraminiferal test and assuming seawater δ¹⁸O values of −1‰V-SMOW. Mesotrophic to oligotrophic conditions persisted after the OAE 2 and throughout the Turonian as evidenced by a diverse planktonic foraminiferal assemblage with different species occupying separate ecological niches in the mixed layer and thermocline.

Late Cretaceous pelagic laminites at the northwestern margin of Indian plate, Pakistan: implications for basin bathymetry and ophiolite emplacement

Article

Full-text available

May 2021

The present study aims to evaluate the microfacies attributes and planktonic foraminiferal biostratigraphy of the late Cretaceous Parh Formation of the Kirthar Range and their implications for the ophiolitic emplacement. Two planktonic foraminiferal biozones were identified namely Dicarinella asymetrica and Globotruncanita elevata biozones suggesting Santonian to Campanian age to the carbonate unit of Parh Formation. The detailed petrographic studies divulged four microfacies showing deposition in the middle shelf to deep basin. Based on facies variation and foraminiferal ecology, six transgressive and regressive sequences were identified. The facies distribution shows diverse fluctuation in sea level during deposition of the rock unit. Although the Campanian pelagic limestone is interbedded with Waziristan ophiolites and its synchronous sedimentary and volcanic interbedded sequence are also recorded in Chagai and Raskoh arc. However, the final emplacement of ophiolite on the northwestern margin of the Indian plate is recorded later in Maastrichtian and early Paleocene. Furthermore, lateral facies variations of the Parh Formation, its diverse lower and upper contacts as well as variation in thicknesses are caused by paleobathymetry due to the underlying hotspots. The hotspots have caused the outpouring of massive volcanic lava resulting in the formation of Bibai volcanics and Deccan Trap.

Middle Albian climate fluctuation recorded in the carbon isotope composition of terrestrial plant matter

Article

Apr 2020
J ASIAN EARTH SCI

This study presents the carbon isotopic record for terrestrial plant matter (δ¹³CTPM) in the Jinju Formation, Gyeongsang Basin, Korea, during the middle Albian. The measured δ¹³CTPM provides continuous high-resolution temporal variations for reconstructing climate change during the middle Albian, which has previously been poorly understood. We found that the δ¹³CTPM variation mostly exceeds the isotopic variation of the contemporaneous atmospheric CO2, indicating that the variation was primarily governed by climate change rather than the atmospheric source. The δ¹³CTPM values corrected to modern atmospheric CO2 show cyclic fluctuations (-27.8‰ to -23.3‰), reflecting a temporal variation of water availability and/or a related taxonomic turnover of plant communities in the hinterland of Jinju Lake. Based on a transfer function for estimating mean annual rainfall (MAR) from measured δ¹³CTPM values, the climate of the basin was found to vary from sub-humid to humid conditions (MAR: 500 to 1500 mm) during the middle Albian. This variability suggests that Albian climate change at middle latitudes occurred more frequently than previously interpreted. The temporal increase in aridity observed in the basin (35° - 38° N) has not been detected in the isotopic records of the Cretaceous Hokkaido section (42° - 45° N) in Japan. This implies the possibility of a periodic northward shift or expansion of the northern hemisphere subtropical high pressure belt.

Data-model comparison reveals key environmental changes leading to Cenomanian-Turonian Oceanic Anoxic Event 2

Article

Full-text available

Feb 2020
EARTH-SCI REV

The middle Cretaceous was a period characterized by elevated sea-floor spreading rates, enhanced volcanism, high atmospheric CO2 levels, warming temperatures, and the peak eustatic highstand of the Mesozoic. Two well-known perturbations in the global carbon cycle mark this interval – the Cenomanian-Turonian Oceanic Anoxic Event 2 (OAE2) and the Mid-Cenomanian Event (MCE). Although studies during the past two decades have arrived at a consensus that the Caribbean Large Igneous Province (LIP) likely played a key role in triggering OAE2, arguably the most significant perturbation of the Late Cretaceous, the detailed environmental developments during the Mid-Late Cenomanian leading up to it have only recently been the focus of investigations. This study, based on previous studies of the Middle Cenomanian – Early Turonian climate, tectonics, sea level, and carbon isotope chemostratigraphy, tests plausible environmental scenarios to explain the behavior of the Middle Cenomanian to Early Turonian carbon cycle, via isotope-mass balance calculation in a simple carbon cycle box model. The model experiments successfully reproduce two distinctive features observed in the Mid-Late Cenomanian δ¹³C curves - 1) decoupling of δ¹³Ccarb and δ¹³Corg reflecting increasing isotope fractionation in response to steadily rising pCO2, driven by enhanced volcanic degassing of mantle-derived CO2, which likely preceded the presumed peak volcanism of the Caribbean LIP; and 2) a long-lived, secondary positive excursion that documents enhanced organic carbon burial in shallow shelf seas that expanded during global sea-level rise and highstand. We demonstrate a plausible combination of environmental forcings that pre-conditioned the mid-Cretaceous ocean-atmosphere system for a massive perturbation, OAE2.

Environmental magnetic characterization for the Pialli Level and the Cretaceous Oceanic Red Bed 7 (Late Albian, Poggio le Guaine core, central Italy)

Article

Oct 2023
GLOBAL PLANET CHANGE

The mid-Cretaceous is known as the most extreme greenhouse period in the last 150 Myr and was punctuated by repeated environmental perturbations. The mid-Cretaceous was also characterized by the emplacement of major Large Igneous Provinces and the deposition of organic-rich layers known as Oceanic Anoxic Events. Here, we present a high-resolution environmental magnetic and stable isotopic records of the western Tethyan pelagic interval in the Poggio le Guaine (PLG, Italy) core, deposited during the late Albian. Environmental magnetic data are here applied to detect redox and paleoproductivity variations across the OAE 1d and CORB 7 events. Combing the magnetic data and geochemical data from carbon (δ13C) and oxygen (δ18O) isotopic records, we document changes in the paleoenvironmental conditions across the Pialli Level and CORB 7 events in the Tethyan realm. The magnetic properties of the 10-m-thick pelagic marine sediments of the PLG core record the onset between upper part of Cretaceous Oceanic Red Bed 7 (CORB 7) and the Pialli Level that is a part of the Oceanic Anoxic Event (OAE) 1d. An increase in the magnetic mineral concentrations with hematite and goethite as the main magnetic carrier characterizes the upper CORB 7 sediments. Variations in “hard” isothermal remanent magnetization and the S-ratio during the upper CORB 7 are interpreted as changes in aeolian dust input into the Umbria-Marche Basin. During the interval between the upper part of CORB 7 and OAE 1d (Pialli Level), the magnetic mineral concentration decreases, and the magnetic mineralogy changes from hematite to magnetite, suggesting a change in the oceanic system. This change might be associated to an increase in orbital forcing capable of modulating the monsoon activity at the onset of the Pialli Level. First-order reversal curves for all samples from the PLG core are similar and indicate a dominance of detrital magnetite. The absence of magnetically non-interacting single domain biogenic particles suggests that an increase in primary productivity was not significant or variation of the anoxic-oxic boundary could have also occurred. Finally, our records show cyclic alterations that reflect changes in the terrigenous input that was triggered by a period of enhanced orbital forcing paced by monsoonal systems. Highlights • The studied record spans the onset of Pialli Level and CORB 7 at Poggio le Guaine section, Italy. •Hematite content reflects enhanced aeolian supply during the CORB 7. •Low primary productivity is inferred by absence of magnetofossils and/or variation of the anoxic-oxic boundary.

Astronomical calibration of the OAE1b from the Col de Pré-Guittard section (Aptian–Albian), Vocontian Basin, France

Article

Jun 2023
CRETACEOUS RES

Aptian Oceanic Anoxic Event 1a in the shallow, carbonate-dominated intrashelf Kazhdumi Basin, Zagros Mountains

Article

Jun 2023
SEDIMENTOLOGY

The early Aptian Selli Oceanic Anoxic Event 1a (ca 120 Ma) is a major Mesozoic episode of biotic, climatic, environmental, and geochemical perturbations associated with the extensive burial of organic matter. Based on the new sedimentological, biostratigraphic, and carbon-isotope data from the Kazhdumi Intrashelf Basin, this study tracks the Oceanic Anoxic Event 1 associated perturbations along the north-eastern margin of the Arabian Plate. The studied succession has five complete third-order sequences with three facies associations: (i) deep open-marine and intrashelf basin; (ii) shallow open-marine mid-ramp; and (iii) inner ramp. The Oceanic Anoxic Event 1aequivalent deposits include the former two facies associations – (i) and (ii) – and are 25 to 31 m thick, which corresponds to the accumulation rates of ca 1.9 to 3.1 cm kyr�1 (uncorrected for compaction) based on the 1.0 to 1.3 Myr duration of the event. The interval retained a high-resolution record of carbon-isotope and sea-level fluctuations, which enables correlation across the Arabian Plate and Tethys. The Oceanic Anoxic Event 1a onset is marked by a biotic change from ostreid-dominated shallow-marine limestone with abundant foraminifera (Palorbitolina lenticularis and Choffatella decipiens) to dark grey deep-water planktonic foraminifera-rich and radiolaria-rich limestone with chert and organic-rich shale (Radiolarian Flood Zone). The upper oceanic anoxic event part of 1a is characterized by the shallowing-upward, backstepping facies marking the return to a shallow open-marine setting, albeit without recovery of the Palorbitolina–Choffatella association. Deep open-marine deposition (Kazhdumi Tongue) was restored early during the Oceanic Anoxic Event 1a recovery in the latest early Aptian. A return to shallow open-marine environments with Mesorbitolina-rich limestone marks the beginning of the late Aptian, followed by a major sea-level fall and karstification. This study resolves some of the uncertainties related to the order and timing of the events influencing the environmental disturbances across the eastern Arabian Plate during Oceanic Anoxic Event 1a and stresses the importance of shallow carbonate-dominated intrashelf basins as faithful recorders of carbon-isotope and sea-level oscillations and palaeoenvironmental changes during global oceanic perturbations.

Ostracods of the Cenomanian-Turonian transition in the Ksour and Amour Mountains (Saharan Atlas, Algeria): systematic and palaeobiogeographic implications

Article

Full-text available

May 2023

The study of ostracods from the Cenomanian-Turonian transition in the Ksour and Amour Mountains (Saharan Atlas, Algeria) has allowed the identification of fossil assemblages characterising this relevant time interval characterized by global environmental changes. The ostracod assemblages consist of fifteen species and seven genera, and are dominated by the Family Cytherellidae (mainly genus Cytherella), and secondarily by the families Paracyprididae (exclusively Paracypris) and Trachyleberididae (mainly Cythereis). Less common are components of families Bairdiidae, Bythocypridae and Macrocyprididae. The studied ostracod assemblages were compared with those assemblages from basins belonging to palaeobiogeographic provinces of North Africa-Middle East (Gondwana palaeomargin) to search for possible similarities among basins. Thus, the results obtained show the proximity of the ostracod fauna of the Moroccan and Egyptian basins, to which the two basins belonging to the Middle East (Jordan and Oman) are related, the strong similarity between the basins of the Saharan Atlas (Algeria and Tunisia) and finally, the isolation of the ostracod fauna of the Lebanese Basin. This palaeobiogeographical topology shows the probable existence of communication routes during the Cenomanian-Turonian transition or equivalent palaeoenvironmental conditions in different basins.

Schistes Lustrés in a hyper‑extended continental margin setting and reinterpretation of the limit between the Mont Fort and Tsaté nappes (Middle and Upper Penninics, Western Swiss Alps)

Article

Full-text available

Mar 2023
SWISS J GEOSCI

The Schistes Lustrés form a large and complex unit at the top of the Penninic nappe stack of the Alpine belt. Calcschists, partly of Late Cretaceous age, constitute the dominant lithology. They are closely associated both with blueschist facies Piemont-Ligurian ophiolites and continent-derived Mesozoic metasediments. The question of whether the Schistes Lustrés originated on continental or oceanic crust has been extensively debated among Alpine geologists and is locally still controversial. We present here new structural and stratigraphic observations, as well as Raman graphite thermometry (RSCM) data, for the Schistes Lustrés complex of the Combin zone in the Hérens, Dix and Bagnes valleys. Our observations indicate that the basal part of this Schistes Lustrés complex (defined as the Série Rousse) is systematically devoid of ophiolitic material, and rests in stratigraphic contact on the underlying Triassic - Lower Cretaceous metasediments and Paleozoic basement of the Mont Fort nappe (Prepiemont paleogeographic domain). The unconformity at the base of the Schistes Lustrés complex is interpreted as resulting from the sedimentation of the Série Rousse on a paleorelief formed by remnants of Jurassic normal fault scarps, and not as an Alpine tectonic contact, as previously proposed. The lithostratigraphic comparison with the Breccia nappe in the Prealps, as well as a foraminifer discovery, allows us to better constrain the age of the Série Rousse. It extends from the middle of the Early Cretaceous (Aptian?) to the Late Cretaceous (Campanian to earliest Maastrichtian?). In contrast, the upper contact of the Série Rousse with the ophiolite-bearing Schistes Lustrés clearly corresponds to an Alpine thrust. The thrust zone is underlined by thin and discontinuous slices of highly strained continental-margin derived Mesozoic metasediments (Frilihorn slices). RSCM data show that the recrystallization of the organic matter progressively increases on both sides towards this contact. This contact, internal to the Schistes Lustrés complex, is reinterpreted as the major tectonic contact separating the Middle Penninic Mont Fort nappe from the Upper Penninic Tsaté nappe (defined here as including only the ophiolite-bearing Schistes Lustrés and associated meta(ultra-)basites). This study clearly documents that the Schistes Lustrés consist of sediments either deposited on oceanic crust, showing locally preserved stratigraphic contacts with ophiolitic or serpentinized sub-continental mantle slivers, or sediments still resting stratigraphically on a former hyper-extended continental margin.

The Mont Fort nappe, its Mesozoic cover and relations to the Upper Penninics (Western Swiss Alps)

Thesis

Full-text available

Dec 2022

Adrien Pantet

This study focuses on the Pennine Alps, in the central part of the Alpine Arc. As this massif offers a wide section through the Alpine nappe stack, and as its geological structure and tectonometamorphic evolution have been extensively studied, it constitutes an ideal setting for the study of continental collision processes. Although the major tectonic units of the Pennine Alps were defined more than a century ago, and despite the countless studies conducted since then, fundamental questions such as the position of some major tectonic boundaries or first order geometries of some nappes, are still debated. In particular, the questions regarding the position of the boundary between the Middle Penninic Mont Fort nappe and the Upper Penninic Tsaté nappe as well as the tectonic attribution and paleogeographic origin of the Frilihorn and Cimes Blanches units have been debated for decades. These questions constitute the main topics of this study. This work is mainly based on an important structural and stratigraphic field study over an area extending between the Bagnes and the Matter valleys. It provides new and detailed data concerning the nature of the studied contacts and allows to revise several tectonic interpretations. Both the basal contact of the Lower Triassic to Lower Cretaceous Evolène Series and the basal contact of the p.p. Upper Cretaceous non-ophiolitic Schistes Lustrés of the Série Rousse are reinterpreted as stratigraphic. These two series would therefore constitute together the autochthonous sedimentary cover of the Mont Fort nappe. Several sections of the basal contacts of these series are discordant. They are interpreted as corresponding to remnants of high-amplitude Jurassic normal paleofaults. The contact between the Série Rousse and the overlying ophiolite-bearing Schistes Lustrés is marked by the presence of the thin Triassic-Jurassic Frilihorn tectonized slices. This contact, located within the Schistes Lustrés complex of the Combin zone, is interpreted as representing the major tectonic boundary separating the Middle and Upper Penninic units. A redefinition of the Tsaté nappe is proposed, excluding the Série Rousse, and including only the ophiolite-bearing Schistes Lustrés and associated meta(ultra-)basites. In the Täschalpen area, east of Zermatt, the Permian-Jurassic Faisceau Vermiculaire series (incl. Cimes Blanches and Frilihorn Series) is in contact with the basement forming the Alphubel anticline. This contact is interpreted as stratigraphic, and the ensemble formed by the basement of the Alphubel anticline, the Faisceau Vermiculaire and the Série Rousse is interpreted as constituting the prolongation of the Mont Fort nappe, east and south of the Dent Blanche klippe, in the lower limb of the Mischabel backfold. The proposed tectonic scheme emphasizes the significance of the Mont Fort nappe. This nappe derived from the Prepiemont distal margin constitutes a link between the Briançonnais units and the Piemont ophiolites which appears to be essential for the understanding of the structure of the Penninic nappe stack.

Aptian Planktonic Foraminiferal Biostratigraphy and Microfacies Analyses of Mudurnu-Nallıhan Sequence (Ankara, Turkey)

Thesis

Full-text available

Jul 2019

Deniz Yağmur Kayhan

The Mudurnu – Nallıhan Sequence that comprises the Upper Jurassic – Lower Cretaceous carbonate succession was cut by diabase dykes and intercalated with volcano-sedimentary rocks in the Nallıhan region, Ankara, Turkey. The sequence consists of the Yosunlukbayırı Formation and the Soğukçam Limestone. This study focuses on the high-resolution biostratigraphy and microfacies analyses of the Soğukçam Limestone widely exposed in the north of the Nallıhan town. For this purpose, the stratigraphic section was measured (94.73 m thick) and a total of 44 samples were collected from limestone, shale and diabase dyke. By using planktonic foraminiferal bioevents, the following biozones were established in ascending order: Globigerinelloides blowi Zone (Early Aptian), Leupoldina cabri Zone (Early Late Aptian) and Globigerinelloides ferreolensis Zone (Late Aptian). Eight species of Hedbergella, three species of Globigerinelloides, and Leupoldina cabri were identified in the study. Only the presence of these r-mode opportunistic planktonic foraminifera, Hedbergella and Globigerinelloides, in the studied samples indicates that eutrophic environmental conditions prevailed in the Aptian time in the studied region. The elongated chamber forms, such as Hedbergella roblesae and Leupoldina cabri, low-oxygen planktonic foraminifers suggests that the Oceanic Anoxic Event 1a (the Selli Event) has possibly been recorded in the Leupoldina cabri Zone of the studied sequence. In addition, small benthic foraminifera, radiolaria and Cadosina sp. were recorded through the measured section. Based on both lithofacies analysis (determination of the depositional texture), and biofacies analysis (fossil assemblages), microfacies types were defined as MF-1: Radiolarian mudstone / wackestone, MF-2: Planktonic foraminiferal and radiolarian wackestone / packestone and MF-3: Planktonic foraminiferal mudstone / wackestone. In the light of the microfacies analyses, the depositional environments of the Aptian part of the Soğukçam Limestone were determined as toe of slope to deep water basin. Keywords: Planktonic foraminifera, Biostratigraphy, Aptian, Soğukçam Limestone, Nallıhan/Ankara

Planktonic foraminifera document palaeoceanographic changes across the middle Cenomanian carbon-isotope excursion MCE 1: new evidence from the UK chalk

Article

Full-text available

Nov 2022

Planktonic foraminifera were studied at Lydden Spout, near Folkestone (southeast England, UK), the reference section of the middle Cenomanian Event 1 (MCE 1) characterized by a prominent double-peak δ ¹³ C excursion of 1 ‰ identified in different ocean basins and considered a global event. Biostratigraphic and quantitative analysis of planktonic foraminifera are correlated to the δ ¹³ C perturbation, to the positive δ ¹⁸ O shifts identified within MCE 1 and to the occurrence of Boreal macrofossils (the bivalves Chlamys arlesiensis and Oxytoma seminudum , and the belemnite Praectinocamax primus ). Variations in abundance and species richness of planktonic foraminifera and the inferred palaeoecological preferences of taxa permit the identification of distinct palaeoenvironmental settings across MCE 1. The stratigraphic interval corresponding to MCE 1 is characterized by the absence of oligotrophic rotaliporids, and by the evolutionary appearance of meso-eutrophic dicarinellids and of Muricohedbergella portsdownensis , a cold-water species that occurs at the same level as the Boreal macrofossils. These observations indicate a palaeoceanographic scenario characterized by reduced stratification of surface waters and absence/disruption of the thermocline in a dominantly eutrophic regime during MCE 1. Evidence provided by planktonic foraminifera, Boreal macrofossils and δ ¹⁸ O records documented for the late Cenomanian Plenus Cold Event (PCE) at Eastbourne (UK) reveal similarities that confirm the periodic inflow of cold Boreal seawater originating in the Norwegian Sea as previously postulated to explain the occurrence of Boreal fauna in the Anglo-Paris Basin. The southerly extension of this water mass may be related to the reorganization of circulation driven by the long eccentricity cycle.

UNRAVELLING THE MICROFOSSILS RECORD OF LATE CRETACEOUS OCEANIC ANOXIC EVENT 2 IN THE SOUTHERN HIGH LATITUDES (IODP SITES U1513 AND U1516, SE INDIAN OCEAN)

Conference Paper

Jan 2022

Paleoenvironmental and Bio-Sequence Stratigraphic Analysis of the Cretaceous Pelagic Carbonates of Eastern Tethys, Sulaiman Range, Pakistan

Article

Full-text available

Jul 2022

The Cretaceous pelagic carbonate succession, i.e., Goru Formation was studied in the Chutair Section, Sulaiman Range, representing part of the eastern Tethys for the paleoenvironment and bio-sequence stratigraphy. Eight planktonic foraminiferal biozones are identified which include: 1. Muricohedbergella planispira Interval Zone; 2. Ticinella primula Interval Zone; 3. Biticinella breggiensis Interval Zone; 4. Rotalipora appenninica Interval Zone; 5. Rotalipora cushmani Total Range Zone; 6. Whiteinella archeocretacea Partial Range Zone; 7. Helvetoglobotruncana helvetica Total Range Zone; and 8. Marginotruncana sigali Partial Range Zone representing Albian-Turonian age. The pet-rographic studies revealed five microfacies: 1. Radiolarians-rich wacke-packestone microfacies; 2. Radiolarians-rich wackestone microfacies; 3. Planktonic foraminiferal wacke-packestone microfa-cies; 4. Planktonic foraminiferal wackestone microfacies; and 5. Planktonic foraminiferal packestone microfacies; indicating deposition of the Goru Formation in outer-ramp to deep basinal settings. Based on the facies variations and planktonic foraminiferal biozones, the 2nd and 3rd order cycles are identified, which further include six transgressive and five regressive system tracts. The sea level curve of the Goru Formation showed fluctuation between outer-ramp and deep-basin, showing the overall transgression in the 2nd order cycle in the study area, which coincides with Global Sea Level Curve; however, the 3rd order cycle represents the local tectonic control during deposition of the strata.

Mesozoic biological events and ecosystems in East Asia

Article

May 2022

Since the late twentieth century, palaeontological and geological evidence from East Asia has contributed to significant advances in the understanding of the Mesozoic world. Geological Society Special Publication 521 covers a wide range of topics that subdivide into four themes. These include: (1) clues and evidence from vertebrate fossils; (2) clues and evidence from invertebrate and plant fossils; (3) significant fossils from amber; and (4) palaeoenvironments and palaeoecosystems. The volume features 18 articles by 53 authors from different disciplines, including geochronology, palaeontology, stratigraphy, sedimentology, tectonics and geochemistry.

The Origin of Silica of Marine Shale in the Upper Ordovician Wulalike Formation, Northwestern Ordos Basin, North China

Article

Full-text available

Sep 2021

The shale of the Wulalike Formation developed in the northwestern Ordos Basin is considered to be an effective marine hydrocarbon source rock. One of the key factors for successful shale gas exploration in the Wufeng–Longmaxi Formation in the Sichuan Basin is the high content of biogenic silica. However, few people have studied the siliceous origin of the Wulalike shale. In this study, we used petrographic observation and element geochemistry to analyze the origin of silica in the Wulalike shale. The results show that the siliceous minerals are not affected by hydrothermal silica and mainly consist of biogenic and detrital silica. A large number of siliceous organisms, such as sponge spicules, radiolarians, and algae, are found under the microscope. It has been demonstrated that total organic carbon has a positive correlation with biogenic silica and a negative correlation with detrital silica, and biogenic silica is one of the effective indicators of paleoproductivity. Therefore, the enrichment of organic matter may be related to paleoproductivity. Through the calculation of element logging data in well A, it is found that biogenic silica is mainly distributed in the bottom of the Wulalike Formation, and the content of biogenic silica decreases, while the content of detrital silica increases upward of the Wulalike Formation. Biogenic silica mainly exists in the form of microcrystalline quartz, which can form an interconnected rigid framework to improve the hardness and brittleness of shale. Meanwhile, biogenic microcrystalline quartz can protect organic pores from mechanical compaction. Therefore, it may be easier to fracture the shale gas at the bottom of the Wulalike Formation in well A.

Planktonic foraminiferal biostratigraphy of the Cretaceous strata, Indus Basin, Pakistan, Eastern Tethys: implications for oceanic anoxic events

Article

Jun 2021
AUST J EARTH SCI

Stratigraphic horizons of the Cretaceous oceanic anoxic events (OAEs) are constrained for the first time at the northwestern margin of the Indian Plate, Pakistan, using high-resolution planktonic foraminiferal biostratigraphy. In this study, 15 planktonic foraminiferal biozones have been erected, suggesting an early Aptian to early Maastrichtian age for the studied section. Based on the established biozones, the stratigraphic positions of the Cretaceous OAEs are defined. The lowermost organic-rich interval occurs in the Hedbergella delrioensis and Globigerinelloides algerianus zones of the early to late Aptian, which correlate with the Selli (OAE 1a) and Fallot events. The next interval with the abundant presence of organic matter occurs in the Ticinella bejaouaensis zone (latest Aptian) and correlates with OAE1b. The third organic-rich interval falls in the Biticinella breggiensis zone of the middle to late Albian and correlates with the OAE1c. The fourth organic-rich horizon straddles the Cenomanian − Turonian boundary and corresponds to OAE2. The fifth organic-rich interval falls in the Globotruncana ventricosa zone of middle to late Campanian age and correlates with the Campanian isotopic event. The evolution of planktonic foraminifera in this part of the Tethys Ocean, is driven by OAEs, e.g. at the base of OAE2, a mass extinction of foraminiferal species, mainly rotaliporids, occurred, and at the end of OAE2, simultaneous appearances of the whiteinellids, marginotruncanids and dicarinellids indicate the fastest rate of speciation.

High-Resolution C-Isotope, TOC and Biostratigraphic Records of OAE 1a (Aptian) From an Expanded Hemipelagic Cored Succession, Western Tethys: A New Stratigraphic Reference for Global Correlation and Paleoenvironmental Reconstruction

Article

Mar 2021

A high‐resolution δ13Ccarb record from Cau (Spain) is proposed as a new global reference for stratigraphic correlation of the Aptian The ultrahigh‐resolution record of the onset of OAE 1a documents a long‐term negative excursion in C‐isotope values, punctuated by several marked negative spikes Evidence for the importance of OM burial as a feedback mechanism in response to increased carbon inputs into the ocean‐atmosphere system

Fossil evidence for vampire squid inhabiting oxygen-depleted ocean zones since at least the Oligocene

Article

Feb 2021

Dirk Fuchs

Fossil evidence for vampire squid inhabiting oxygen-depleted ocean zones since at least the Oligocene

Article

Full-text available

Feb 2021

A marked 120 My gap in the fossil record of vampire squids separates the only extant species (Vampyroteuthis infernalis) from its Early Cretaceous, morphologically-similar ancestors. While the extant species possesses unique physiological adaptations to bathyal environments with low oxygen concentrations, Mesozoic vampyromorphs inhabited epicontinental shelves. However, the timing of their retreat towards bathyal and oxygen-depleted habitats is poorly documented. Here, we document a first record of a post-Mesozoic vampire squid from the Oligocene of the Central Paratethys represented by a vampyromorph gladius. We assign Necroteuthis hungarica to the family Vampyroteuthidae that links Mesozoic loligosepiids with Recent Vampyroteuthis. Micropalaeontological, palaeoecological, and geochemical analyses demonstrate that Necroteuthis hungarica inhabited bathyal environments with bottom-water anoxia and high primary productivity in salinity-stratified Central Paratethys basins. Vampire squids were thus adapted to bathyal, oxygen-depleted habitats at least since the Oligocene. We suggest that the Cretaceous and the early Cenozoic OMZs triggered their deep-sea specialization.

High‐Resolution C‐Isotope, TOC and Biostratigraphic Records of OAE 1a (Aptian) From an Expanded Hemipelagic Cored Succession, Western Tethys: A New Stratigraphic Reference for Global Correlation and Paleoenvironmental Reconstruction

Article

Full-text available

Mar 2021

A high‐resolution carbonate C‐isotope stratigraphy for the Aptian is presented for the Cau core (Spain). The biostratigraphically calibrated C‐isotope stratigraphy of the core is used to refine the previously defined C‐isotope segments of the Aptian. Thirteen C‐isotope segments have been identified and correlated, and further subdivisions are presented. Correlation with other sections worldwide demonstrates the robustness of the C‐isotope stratigraphy of the Cau core. The studied succession includes a continuous record of the early Aptian Oceanic Anoxic Event (OAE 1a). Its onset has been studied at an ultrahigh‐resolution scale (0.2–0.5 kyr spacing), revealing a succession of sharp δ¹³Ccarb negative spikes, interpreted as a record of pulses of volcanism and methane emissions. The largest spike was rapid (<10 kyr) and marks the base of OAE 1a, which occurs within a longer‐term falling δ¹³Ccarb trend. The C‐isotope profile across OAE 1a perfectly records the negative (C3/Ap3), positive (C4/Ap4), steady (C5/Ap5), and positive (C6/Ap6) segments that were defined from Cismon (Italy) and subsequently identified worldwide. The Ap7 to Ap14 segments record a C‐isotope negative excursion, coupled with high TOC contents, probably related to regional paleogeography. The links with global environmental changes, episodes of widespread deposition of organic matter, and ultimately to major volcanic episodes are discussed. We propose the Cau core as a new reference section for the Aptian, and specifically for OAE 1a, based on its expanded and well‐preserved sedimentary, geochemical and biotic archives, which provide further insights into the environmental and biotic changes that occurred during this time interval.

Biotic response to the latest Cenomanian drowning and OAE2: A case study from the Eastern Desert of Egypt

Article

Feb 2021
P GEOLOGIST ASSOC

The changes in macrofauna and microfauna, before, during and after the latest Cenomanian global Oceanic Anoxic Event (OAE2), from the Eastern Desert of Egypt are documented, along with an inferred paleoenvironment. The age of the studied OAE2 interval is constrained by the last occurrence of the marker calcareous nannofossils species Axopodorhabdus albianus along with the previously identified positive δ13C excursion from the coeval ammonite Vascoceras cauvini Zone (= Neocardioceras juddii Zone), enabling correlation with the peak “b” of the OAE2. Based on the studied microfaunal assemblages, a warm shallow restricted lagoonal environment with mesotrophic conditions and strong seasonality is inferred. The presence of a rare ammonite and ostracods attest to the intermittent introduction of marine waters within this inner ramp setting. In terms of sequence stratigraphy, two 3rd order depositional sequences are recorded. The top surface of the first depositional sequence, at the sequence boundary, SB Ce 5 (the start of the OAE2), is marked by an abrupt faunal change with reduced abundances of the macrofaunal elements. This is in tune with other Egyptian records of relatively smaller loss (10%) at the Cenomanian-Turonian boundary, as compared to much higher numbers (53 to 79% of species), globally. This faunal (biotic bottleneck) and lithological change (from siliciclastic-dominated deposits to a largely carbonate-dominated one) at the SB Ce 5 is attributed as a response to the latest Cenomanian drowning (the highest sea-level during the Phanerozoic) that also resulted in the formation of carbonate platform.

Major and trace element characterization of Oceanic Anoxic Event 1d (OAE 1d): Insight from the Umbria-Marche Basin, central Italy

Article

Dec 2020
CHEM GEOL

The Pialli Level in the Umbria-Marche Basin (central Italy) correlates with the lowermost part of the positive carbon isotopic excursion characterizing the late Albian-early Cenomanian Oceanic Anoxic Event 1d (OAE 1d). High-resolution litho-, bio-and chemostratigraphic data from the Monte Petrano and Le Brecce sections allow for a bed-by-bed comparison of the two successions, and discriminate local from basin-scale signals. We present new X-ray fluorescence, ICP-MS and TOC data for both the limestones and the Pialli Level shales integrated with available carbonate carbon isotopes and nannofossil temperature and nutrient indices. Data indicate a homogenous background sedimentation dominated by pelagic carbonates, biogenic silica with little contribution by clays. The limited variation in lithogenic elements points to an essentially homogeneous detrital source area with limited fluvial terrigenous input. Higher Mn concentrations coupled with low enrichments in redox-sensitive elements, such as U, Fe, S, Re, Mo, Ag, suggest that the Pialli Level shales represent temporary suboxia without reaching anoxia. Furthermore, P, authigenic Ba, Cd and Ni enrichments, together with nannofossil nutrient index indicate generally low primary productivity conditions along the entire succession, with only minor increases for some of the black-to-dark grey shales of the Pialli Level. The nannofossil temperature index highlights a warm climate during the OAE 1d, with the warmest conditions experienced during the deposition of the Pialli Level shales. During the late Albian, the warm and humid climate was interrupted by brief episodes of relatively warmer and less saline surface waters ensuring slower rates of bottom water renewal and producing temporary suboxic conditions. Such paleoceanographic dynamics would be the continuation of episodic warmer and humid pulses characterizing the late Albian interval in the Umbria-Marche Basin. As such, the Pialli Level can be considered the result of a last episode closing a cycle before the establishment of a steadier climate during the early Cenomanian.

Albian (Lower Cretaceous) Carbon Isotope Chemozones, Texas Comanche Shelf and Mexican Chihuahua Trough: Implications for OAEs

Article

Mar 2020

Organic-carbon-rich black shale beds that are associated with positive carbon isotope excursions and yield pelagic fossils are evidence of short-term changes in ocean water mass and are important chronostratigraphic correlation tools. Five recognized Cretaceous Oceanic Anoxic Events (OAEs) are well documented in many basins on the Texas Comanche Shelf and the northern Mexico Chihuahua Trough: lower Aptian OAE 1a, Aptian-Albian OAE 1b, upper Albian OAE 1c, uppermost Albian OAE 1d, and Cenomanian-Turonian OAE 2. Two of these chemozones have previously been documented in Mexico and Texas, OAE 1b by a positive δ¹³C excursion of 2 ‰ and OAE 1d with a positive δ¹³C excursion of 1.6-1.9 ‰. Here we document for the first time OAE 1c in gray marine shale of the Boracho Formation in West Texas by a positive δ¹³C excursion of 1 ‰; the Boracho records the late Albian flooding of the Western Interior. On the interior shelf in shallow water carbonates the absence of carbon isotopic excursions suggests that dysaerobic waters did not affect the upper part of the water column. Review of biotic assemblages of each Gulf of Mexico Albian OAE suggests that water depths ranged from at least 300 m to just below storm wave base at about 15-30 m. These Albian OAEs were identified in the Mediterranean area and in the deep Atlantic Ocean and are recognized on the North American cratonic blocks, which supports the hypothesis that ocean/climate conditions favoring low-oxygen water masses were widespread although deposition was in local basins.

Onshore–offshore correlations of Cretaceous fluvial-deltaic sequences, southern Baltimore Canyon trough

Article

Feb 2020
AAPG BULL

We evaluate Cretaceous depositional sequences on approximately 4400 km (∼2700 mi) of newly released multichannel seismic profiles and five wells on the continental shelf in the southern Baltimore Canyon trough and tie the data to three wells drilled onshore in the Maryland coastal plain. Seismic geometries coupled with facies and biostratigraphy from the wells are used to delineate mid-Cretaceous (Aptian–Turonian) depositional sequences and paleogeography. Beneath these sequences, 400–1000 m (1300–3300 ft) of Lower Cretaceous sedimentary rocks underlie the modern shelf. They thicken along strike to the southwest, implying a southern sediment source. Aptian to Cenomanian sediments were deposited in shelf to nearshore settings. A landward movement of the depocenter and a shift toward facies indicative of deeper paleodepths marks a 10^7-yr mid-Cretaceous transgression, within which we identify five sequences. A composite maximum flooding surface (MFS) within the uppermost of these retrogradational units is associated with the Cenomanian–Turonian boundary and ocean anoxic event 2. Shingled, lower Turonian seismic reflections prograde across the outer shelf, downlapping onto the composite MFS, and are truncated by a mid-Turonian sequence boundary. The Upper Cretaceous section thickens seaward and along strike to the northeast, implying a northern source and little Late Cretaceous accommodation beneath the modern shelf. Mid-Cretaceous strata offshore Maryland are likely sand-prone, considering their proximity to the correlative fluvial facies of the onshore Potomac Group. These potential reservoir sands are capped by regional confining units generated by 10^7-yr global mean sea-level flooding events and are excellent targets for supercritical carbon storage.

Spatio-temporal variability in microfossil and geochemical records of Cenomanian-Turonian Oceanic Anoxic Event-2: A review1

Article

Full-text available

Jun 2024

Benthic foraminifera across the Albian–Cenomanian transition and their paleoceanographic significance during OAE1d in the western Tethys (Umbria–Marche Basin, Italy)

Article

Sep 2023
PALAEOGEOGR PALAEOCL

The benthic foraminiferal assemblages from the upper Albian-lower Cenomanian interval of the Scaglia Bianca Formation in the Monte Petrano (MP) and Le Brecce (LB) sections (Umbria–Marche Basin; Italy) provide a detailed record of the faunal changes across the Oceanic Anoxic Event 1d (OAE 1d). Fluctuations in abundance, diversity, and species composition reflect variations in bottom-water oxygenation and organic carbon fluxes. Benthic foraminifera are integrated with planktonic foraminifera, calcareous nannofossils, and geochemical proxies to reconstruct the bottom and surface water conditions across the OAE 1d in the Umbria–Marche Basin. The pre-OAE 1d interval was characterized by benthic foraminifera that thrived under stable mesotrophic condition in bottom waters. In surface waters, planktonic foraminifera indicate dominant mesotrophic conditions in agreement with calcareous nannofossil assemblages suggesting a regime of higher fertility under cooler conditions. During the OAE 1d interval, benthic foraminifera display an increase in the abundance of infaunal taxa, suggesting mesotrophic conditions in bottom waters. Nevertheless, within the Pialli Level, the six laminated black-to-dark grey shale horizons (MP1/LB1 to MP6/LB6), benthic foraminifera are absent or highly impoverished (MP1, MP2, MP4, MP6, LB5, LB6), suggesting hypoxic/anoxic conditions in bottom waters. Planktonic foraminifera in this interval reflect mesotrophic to oligotrophic conditions under the presence of an expanded mixed layer and deeper thermocline in the surface waters. Calcareous nannofossils record warm conditions and lower fertility starting just prior to and across the OAE 1d. However, higher values of fertility are recorded in the black-to-dark grey shales MP3/LB3, MP4/LB4 and MP5/LB5 of the Pialli Level. The post-OAE 1d interval is marked by an increase in the diversity of benthic foraminifera, indicating a restoration of the oxygen conditions in a continuous mesotrophic regime in bottom waters. The surface waters experienced oligotrophic conditions based on the planktonic and calcareous nannofossils. A minor discrepancy between benthic foraminifera and geochemical reconstruction of oxygenation levels of bottom waters was recorded, especially in the Pialli Level. The benthic microfaunas appear to be very sensitive to very short-term oxygen depletion at the seafloor when geochemical proxies suggest temporary suboxia. This might indicate that very rapid redox changes are not resolved by bulk elemental data. Otherwise, benthic foraminifera might be much more responsive to very low concentrations of oxygen in bottom waters and temporarily disappear under strong suboxia before reaching fully anoxic conditions.

Environment and Geochemistry of Sediments

Book

Full-text available

Jun 2023

This reprint considers a vast range of questions devoted to environmental geochemistry. The Special Issue “Environment and Geochemistry of Sediments” includes 10 papers. The themes of research cover different problems of the geochemistry of sediments, such as the reconstruction of the paleoenvironment in the lake basins in the high latitude zones on the base of geochemical indicators, the processes of the sedimentary environment and climate evolution during the Late Carboniferous–Early Permian period in the central Junggar Basin (China), and the study of the paleoenvironment and bio-sequence stratigraphy in the Cretaceous pelagic carbonate succession part of the eastern Tethys. Several articles discuss the features of the geochemistry of sedimentation in places of prehistoric anthropogenic activity, for example, based on lithological and geochronological analyses, magnetic susceptibility, and microcharcoal studies, the anthropogenic sources of metals in south-eastern Baltic lake sediments from the Neolithic to the Medieval Age were determined. A new approach using the geochemical indication was developed for the determination of the functional zones of prehistoric archaeological sites in Eastern Europe. The application of geochemical multi-element and geochronological analyses of the Iron Age and early Roman cultural layers was considered at the archaeological site in the Netherlands. Some papers explore to the pollution hazard problem concerning for example the accumulation and distribution of a hazardous contaminant, mercury (Hg), in the basin of Onega Lake, Russia, the second largest lake in Europe, and the distribution of arsenic in the soils of the Verkhnekamskoe potassium salt deposit, Perm Krai, Russia. The ecological state of basins as a result of technogenic processes using a geochemical approach is illuminated in the papers devoted to the mineralogical and geochemical contents of the bottom sediments of Al-Kharrar and Al-Shuaiba Lagoons, Red Sea, Saudi Arabia. The Guest Editors of this Special Issue would like to thank all of the authors for their valuable contributions.

Chemo- and cyclostratigraphic records of the Albian from the Tethyan Himalaya of southern Tibet, China

Article

Sep 2022
GLOBAL PLANET CHANGE

The Albian Age is characterized by frequent short-lived perturbations of the global carbon cycle, including a series of Oceanic Anoxic Events (OAEs). Carbon Isotope Excursions (CIEs) document these OAEs in detail. A strong influence of orbital forcing on oceanographic and climatic conditions in the Albian has been documented, but the relationship between orbital changes and the carbon cycle is still unclear. The Albian CIEs are well recorded globally, except in the eastern Tethys. The major forcing mechanisms of Mesozoic carbon cycling have long remained a conundrum. Here, we present bulk carbon (δ¹³Ccarb) and oxygen (δ¹⁸Ocarb) isotope data, magnetic susceptibility (MS) and total organic carbon (TOC) data from the Nirang Section in the Tethyan Himalaya of southern Tibet, China. The δ¹³Ccarb record for the first time documents the long-term secular variations in δ¹³C during the Albian in the Tethyan Himalaya in high resolution. The δ¹³C curve obtained in Nirang can be correlated well with reference sections in other basins. OAE1b and 1c were identified as troughs in the δ¹³C profile in the lowermost and upper part of the section. Cyclostratigraphic analysis of MS, δ¹³Ccarb and TOC content from the Nirang Section reveals the imprint of the orbital cycles of eccentricity (~100 kyr and ~ 405 kyr) and a long-term amplitude modulation of either obliquity or eccentricity (~1.2 Myr). The band-pass filters of the ~100 kyr periodicity in MS provide the estimation of 563 kyr for the duration of OAE 1c and 677 kyr for that of the negative shift between OAE 1b and 1c. A detected ~1.1 Myr periodicity is the most significant cycle, providing strong evidence for astronomically paced climate change in the eastern Tethys during the Albian. The band-pass filters of the ~1.1 Myr periodicity in MS and TOC display a close correspondence, suggesting that the productivity and/or preservation potential of organic matter was likely controlled by orbitally forced changes in terrigenous input. Increasing δ¹³C values correspond to higher values of MS and TOC content and vice versa, indicating that the δ¹³C values of the eastern Tethys during the Albian were influenced by the intensity of the terrigenous flux and the subsequent burial of organic matter paced by orbital change. This work implies that cyclic changes in carbon reservoirs in the low latitudes of the Southern Hemisphere during the Albian were controlled by seasonal variations in terrigenous input driven by the influence of orbital cycles on regional hydrological processes.

Biotic and Paleoceanographic Changes Across the Late Cretaceous Oceanic Anoxic Event 2 in the Southern High Latitudes (IODP Sites U1513 and U1516, SE Indian Ocean)

Article

Full-text available

Sep 2022

Oceanic Anoxic Event 2, spanning the Cenomanian/Turonian boundary (93.9 Ma), was an episode of major perturbations in the global carbon cycle. To investigate the response of biota and the paleoceanographic conditions across this event, we present data from International Ocean Discovery Program sites U1513 and U1516 in the Mentelle Basin (offshore SW Australia; paleolatitude 59°–60°S in the mid‐Cretaceous) that register the first complete records of OAE 2 at southern high latitudes. Calcareous nannofossils provide a reliable bio‐chronostratigraphic framework. The distribution and abundance patterns of planktonic and benthic foraminifera, radiolaria, and calcispheres permit interpretation of the dynamics of the water mass stratification and provide support for the paleobathymetric reconstruction of the two sites, with Site U1513 located northwest of the Mentelle Basin depocenter and at a deeper depth than Site U1516. The lower OAE 2 interval is characterized by reduced water mass stratification with alternating episodes of enhanced surface water productivity and variations of the thickness of the mixed layer as indicated by the fluctuations in abundance of the intermediate dwelling planktonic foraminifera. The middle OAE 2 interval contains lithologies composed almost entirely of radiolaria reflecting extremely high marine productivity; the low CaCO3 content is consistent with marked shoaling of the Carbonate Compensation Depth and ocean acidification because of CaCO3 undersaturation. Conditions moderated after deposition of the silica‐rich, CaCO3‐poor rocks as reflected by the microfossil changes indicating a relatively stable water column although episodes of enhanced eutrophy did continue into the lower Turonian at Site U1516.

Diversity dynamics of microfossils from the Cretaceous to the Neogene show mixed responses to events

Article

Full-text available

Jul 2022

Microfossils have a ubiquitous and well‐studied fossil record with temporally and spatially fluctuating diversity, but how this arises and how major events affect speciation and extinction is uncertain. We present one of the first applications of PyRate to a micropalaeontological global occurrence dataset, reconstructing diversification rates within a Bayesian framework from the Mesozoic to the Neogene in four microfossil groups: planktic foraminiferans, calcareous nannofossils, radiolarians and diatoms. Calcareous and siliceous groups demonstrate opposed but inconsistent responses in diversification. Radiolarian origination increases from c. 104 Ma, maintaining high rates into the Cenozoic. Calcareous microfossil diversification rates significantly declines across the Cretaceous–Palaeogene boundary, while rates in siliceous microfossil groups remain stable until the Paleocene–Eocene transition. Diversification rates in the Cenozoic are largely stable in calcareous groups, whereas the Palaeogene is a turbulent time for diatoms. Diversification fluctuations are driven by climate change and fluctuations in sea surface temperatures, leading to different responses in the groups generating calcareous or siliceous microfossils. Extinctions are apparently induced by changes in anoxia, acidification and stratification; speciation tends to be associated with upwelling, productivity and ocean circulation. These results invite further micropalaeontological quantitative analysis and study of the effects of major transitions in the fossil record. Despite extensive occurrence data, regional diversification events were not recovered; neither were some global events. These unexpected results show the need to consider multiple spatiotemporal levels of diversity and diversification analyses and imply that occurrence datasets of different clades may be more appropriate for testing some hypotheses than others.

Foraminiferal biostratigraphy, facies and sequence stratigraphy analysis across the K-Pg Boundary in Hazara, Lesser Himalayas (Dhudial Section)

Article

Sep 2021

The sedimentary strata were sampled in the lesser Himalayas to probe paleoenvironmental changes across the Cretaceous-Paleogene (K-Pg) boundary in the eastern Tethys. The study provides an integrated lithologic and bio-sequence stratigraphic analysis, leading to paleoecology and paleoenvironmental interpretations. The planktic foraminiferal limestone of the late Cretaceous is overlain by lateritic sandstones and sandy foraminiferal limestones, the latter being of Paleocene age. Though the deposition of cretaceous strata mainly occurred in transgressive and high stand system tracts, the top of cretaceous is marked by type-I sequence boundary and low stand system tract, corresponding to the Paleocene Hangu Formation. Deposits below the K-Pg boundary zone interval have been correlated to the late Cenomanian Rotalipora reichel biozone to early Campanian Globotruncana ventricosa zone, with absence of Maastrichtian fauna. A marked change in fauna above the K-Pg boundary zone interval has been observed and manifested by presence of larger benthic foraminifera such as Lockhartia Davies, 1932 and Globanomalina Haque, 1956 genera. The boundary occurs at the contrasting inter-facial contact of the two rock units and advocates an early lowered sea-levels or dead ocean model. An organic bed of late Turonian-early Coniacian corresponds to the probable presence of the OAE3 and could represent a missing link in the late Cretaceous of lesser Himalayas in the Pakistani domain. Prior to the K-Pg event and Indo-Eurasian collision, an influx of siliciclastics suggests a major episode of uplift and shortening caused by ophiolite obduction or magmatic upwelling during the Campanian. The subsequent erosion and its re-deposition shaped the platform, evolving it from relatively steeper ramp geometry in the Campanian to gentler epeiric ramp in the Selandian and Thanetian, and triggered deposition of shallow ramp larger benthic foraminiferal facies. The boundary is similar in nature with erosional phase in the whole region but its duration was prolonged in the study section and its upper limit has some regional changes. As finding of this study, the late Cretaceous “Nara Sandstone Member” of the Kawagarh Formation in Hazara area of earlier workers could be revised as Paleocene Hangu Formation.

References

Chapter

Mar 2021

Multiproxy strategy for determining palaeoclimate parameters in the Ruby Ranch Member of the Cedar Mountain Formation

Article

Aug 2020

A multiproxy approach for evaluating palaeoclimate parameters in deep-time can result in improvements to inter-related factors affecting palaeohydrology. Here we utilize diverse geochemical tools to improve palaeoclimate estimates for the Cedar Mountain Formation (CMF). Prior research utilized stable carbon and oxygen isotopes to develop chemostratigraphic correlations to the late Aptian–early Albian, hypothesized aridity during a positive carbon isotope excursion (CIE) and estimated p CO 2 through this event. This study refines estimates using petrographical analyses, bulk geochemical proxies for mean annual precipitation (MAP) and clumped isotope palaeothermometry. MAP rates range from 736 to 1042 mm a ⁻¹ with a slight decrease during the hypothesized aridity event. We interpret warm-biased temperatures (with an average of 32.9°C) that do not vary significantly through the study section. Carbonate nodules are likely to have precipitated in highly evaporative conditions as indicated by the presence of dolomite. Utilizing a simple Rayleigh fractionation model and two estimates of δ ¹⁸ O of water, we suggest that evaporation of 2–57% is necessary to result in an enriched end member δ ¹⁸ O w . These data suggest that an increase in aridity is a result of lower MAP rates and greater evaporation during seasonal extremes. Lastly, revised p CO 2 calculations suggest overestimates but indicate a shift towards greater concentrations during the positive CIE.

Bioevents and paleoenvironmental changes in Mid-Cretaceous

Article

Sep 1999

New Albian (Cretaceous) radiolarian age constraints for the Dumak ophiolitic mélange from the Shuru area, Eastern Iran

Article

Mar 2020

Early Cretaceous black shale in the Fajiaying Formation (Lingshan Island, East China): Terrestrial record of hothouse climate

Article

Dec 2019
J ASIAN EARTH SCI

The significance of Cretaceous hothouse climate in terrestrial systems is currently unclear, and its records in terrestrial strata are rarely reported. This study investigated the sedimentary environment of the Fajiaying Formation, characterised by abundant black shale and soft-sediment deformation structures. Five lithofacies have been identified for the Fajiaying Formation, e.g. Facies A: black shale with siltstone inter-bedding, Facies B: black and gray-black shale and siltstone alternations with minor sandstone, Facies C: black and gray-black shale interbedded with gray-black sandstone, Facies D: pebbly sandstone and Facies E: gray-black shale and siltstone. The average TOC content of the shales decreases from facies A (av. 1.32%) to facies E (av. 0.46%) through facies B (av. 0.57%) and facies C (av. 0.40%). The paleosalinity gradually decreases from lithofacies A to lithofacies E, corresponding to the change of paleoclimate. In addition, Bivariate Scatter Plot of SiO2 and Al2O3 + K2O + Na2O and the clay mineral assemblages suggest an arid climate. Combined with distribution characteristics and paleontology of saliferous strata in eastern China, we determine that hothouse climate influenced the salification of lakes located in eastern China during the Early Cretaceous. Furthermore, the Fajiaying Formation in Lingshan Island was deposited in a terrestrial salified lake. Salinization of the sedimentary water bodies of the Fajiaying Formation might be related to an oceanic anoxic event. The black shale developed extensively in the Fajiaying Formation and represents the terrestrial record of hothouse climate.

A Middle Jurassic-Early Cretaceous low-latitude radiolarian zonation based on Unitary Associations and age of Tethyan radiolaritees

Article

Full-text available

Jan 1984
Eclogae Geol Helv

Peter Oliver Baumgartner

Evolution patterns of radiolaria and organic matter variations: A new approach to identify sea-level changes in mid-Cretaceous pelagic environments

Article

Full-text available

Jun 1996

The relation between sea-level changes, plankton productivity, and evolution, as well as the occurrence of anoxic sediments, provides an interesting avenue of paleooceanographic research. In this context, we examined mid-Cretaceous radiolarian faunas, carbonate isotopic and organic matter type data of Deep Sea Drilling Project and Ocean Drilling Program cores from the North Atlantic, and samples from outcrops of the western Tethys from central and northern Italy. Former studies indicate that an expansion of the oxygen minimum zone caused plankton extinctions at the Cenomanian-Turonian boundary. An expanded oxygen minimum zone would destroy deeper habitats of planktic foraminifera, causing the extinction of deeper dwelling forms. Although this model is well established for the Cenomanian-Turonian boundary, not much is known about the causes of extinctions and radiations during the entire mid-Cretaceous (Aptian-Turonian). We demonstrate that the dimension of the oxygen minimum zone, which depends on the relative sea level and the corresponding nutrient supply, causes the complex pattern of evolution and radiation of planktic protozoa and the sedimentation of black shales in the mid-Cretaceous. This new depositional model allows correlation of micropaleontologic data and different types of black shales in the pelagic realm within a sequence stratigraphic framework.

Chronology of fluctuating sea levels since the Triassic (250 million years ago to present)

Article

Full-text available

Jan 1987

The Cenomanian/Turonian Boundary Event in the Indian Ocean: a Key to Understand the Global Picture

Chapter

Full-text available

Jan 1992

Radiolaria from Leg 17 of the Deep Sea Drilling Project

Article

Full-text available

Aug 1973

Ted Moore

Micropaléontologie, paléoécologie et sédimentologie d'une plate-forme carbonatée de la marge passive de la Téthys: l'Urgonien du Vercors septentrional et de la Chartreuse (Alpes occidentales)

Article

Full-text available

Mar 1980

Annie Arnaud Vanneau

Tome 1 : Stratigraphie-sédimentologie : reconstitution de la plate-forme urgonienne de la Chartreuse et du Vercors septentrionnal. - 267 p.-Tome : 2 : Micropaléontologie et paléoécologie des foraminifères benthiques de la plate-forme urgonienne de la Chartreuse et du Vercors. - [609] p.Tome 3 : Atlas des microfacies et de la microfaune de la plate forme urgonienne entre la Chartreuse et le Dévoluy. - [141] p. et f.-[115] f. de pl

Radiolaria from Deep Sea Drilling Project Leg 89

Article

Full-text available

Sep 1986

André Schaaf

Radiolarian faunas from Leg 89 are scarce and poorly preserved. Upper Cretaceous assemblages are reworked. The oldest and lowest assemblage recognized was of the Archaeospongoprunum cortinaensis Zone in Hole 585. The biochronology of two levels in Hole 462A are revised as follows: the lowest assemblage of species useful for biochronology is of the Cecrops septemporatus Zone (early Hauterivian); the age of a higher sample is late Tithonian-early Berriasian, indicating rweorking of older sediment into the Nauru Basin.-Author

Chemostratigraphy versus biostratigraphy: Data from around the Cenomanian-Turonian boundary

Article

Full-text available

Feb 1993

A detailed isotopic profile is presented for a stratigraphically expanded Cenomanian-Turonian boundary section in Chalk facies exposed at Eastbourne, Sussex and compared with data from Pueblo, Colorado. In both sections macro- and micropalaeontological markers (first appearances and disappearances) are well-constrained, and their relative positions and relationship to the structure of the carbon-isotope curve are identical. This consistent relationship between two independent phenomena, one geochemical, the other biostratigraphical, is taken as evidence for the likely synchroneity of both the biostratigraphical markers and the carbon-isotope excursion in these two areas. This interpretation contrasts with suggestions made recently by other authors whose data have been taken to imply a lack of correlation between the carbon-isotope excursion in Europe and North America.

Site 398

Chapter

Full-text available

Jan 1979

Site 398 is located on the southern apron of Vigo Seamount, 160 km off the western coast of the Iberian Peninsula. A thick Cenozoic section was encountered above an even thicker Cretaceous series. Drilling terminated in Hauterivian pelagic limestones belonging to the acoustical basement clearly of sedimentary origin.

The Cenomanian/Turonian Boundary Event (CTBE) at Hole 641A, ODP Leg 103 (Compared with the CTBE interval at Site 398)

Article

Full-text available

Dec 1988

Drilling at ODP Site 641 (on the western margin of Galicia Bank, off northwestern Spain) revealed a thin, but pronounced, interval of black shale and gray-green claystone. Our high-resolution study combines the sedimentology, micropaleontology (palynomorphs and others), organic and inorganic geochemistry, and isotopic values of this layer to demonstrate the distinct nature of the sediment and prove that the sequence represents the local sedimentary expression of the global Cenomanian/Turonian Oceanic Anoxic Event (OAE) of Schlanger and Jenkyns (1976), Arthur and Schlanger (1979), and Jenkyns (1980), also called the Cenomanian/Turonian Boundary Event (CTBE). The most striking evidence is that the strong positive 513C excursion characterizing the CTBE sequences in shallow areas can be traced into a pronounced deep-sea expression, thus providing a good stratigraphic marker for the CTBE in various paleosettings. The isotopic excursion at Site 641 coincides with an extremely enriched trace metal content, with values that were previously unknown for the Cretaceous Atlantic. Similar to other CTBE occurrences, the organic carbon content is high (up to 11%) and the organic matter is of dominantly marine origin (kerogen type II). The bulk mineralogy of the CTBE sediments does not differ significantly from the general trend of Cretaceous North Atlantic sediments (dominance of smectite and zeolite with minor amounts of illite and scattered palygorskite, kaolinite, and chlorite); thus, no evidence for either increased volcanic activity nor a drastic climatic change in the borderlands was found. Results from Site 641 are compared with the CTBE section found at Site 398, DSDP Leg 47B (Vigo Seamount at the southern end of the Galicia Bank).

The Cenomanian-Turonian Oceanic Anoxic Event, I. Stratigraphy and distribution of organic carbon-rich beds and the Marine delta 13C excursion.

Article

Full-text available

Jan 1987

Marine strata deposited during late Cenomanian and early Turonian time display lithological, faunal, and geochemical characteristics which indicate that significant parts of the world ocean were periodically oxygen deficient. At, or very close to, the Cenomanian-Turonian boundary, between 90.5 and 91.5Ma ago, oxygen deficiencies were particularly marked over a period of <1Ma. This short-lived episode of oceanic oxygen deficiency has been termed the Cenomanian-Turonian 'Oceanic Anoxic Event' (OAE). The widespread distribution of anoxic sediments deposited synchronously during such a short-lived event indicates that such sediments are not simply the product of coincidental local climatic or basinal water mass characteristics but are the result of a global expansion and intensification of the Cenomanian-Turonian oxygen-minimum zone related to feedback between sea level rise and regional palaeoceanography. The palaeoceanography of the Cenomanian Turonian OAE is discussed in detail in a companion paper by Arthur et al, 1987.-from Authors

Orbitally induced cycles in benthonic foraminiferal morphogroups and trophic structure distribution patterns from the Late Albian "Amadeus Segment" (Central Italy)

Article

Full-text available

Dec 1993

A detailed analysis was made of benthonic foraminiferal distribution patterns and morphogroups in the late Albian “Amadeus Segment” of the Aptian-Albian organic-rich Scisti a Fucoidi Formation outcropping over a widespread area of the Umbria-Marche region, Central Italy. Rhythmic changes in the trophic structures and composition of benthonic foraminiferal assemblages suggest cyclical fluctuations of the sea floor environment which appear to be orbitally induced. Benthonic foraminiferal assemblages varied significantly through the section and appear to contain a strong paleoecological signal. Fluctuations in both bottom water oxygenation and the surface primary productivity as a result of the orbital forcing are interpreted to have been the primary controls on benthonic foraminiferal distribution patterns.

Mesozoic Calciturbidites in Deep Sea Drilling Project Hole 416ARecognition of a Drowned Carbonate Platform

Article

Full-text available

Jun 1980

Wolfgang Schlager

This Tithonian-Hauterivian section contains c 10% limestone and marlstone interbedded with shale and sandstone. Depositional structures, grain composition, and diagenetic fabrics of the limestone beds as well as association with graded sandstone and brown shale suggest their deposition by turbidity currents below CCD. Carbonate material was initially shed from a shallow-water platform with ooid shoals and peloidal sands. Soft clasts of deep-water carbonate muds were ripped up during downslope sediment transport. Shallow-water mud of metastable aragonite and Mg calcite was deposited on top of the graded sands, forming the fine tail of the turbidite; it has been subsequently altered to tight micritic limestone. Drowning of the platform during the Valanginian is inferred from the disappearance of the micritic limestones, the increase in abundance of phosphorite, of ooids with quartz nuclei, and of the quartz content in the calciturbidites. In Hauterivian time, the carbonate supply disappeared completely. -from Author Rosenstiel School of Marine and Atmospheric Science, Division of Marine Geology and Geophysics, University of Miami, Miami, Florida.

Impact of Cretaceous Sea Level Rise and Anoxic Events on the Mesozoic Carbonate Platform of Yugoslavia

Article

Full-text available

Jun 1991
AAPG BULL

Hugh C. Jenkyns

The Adriatic/Dinaric carbonate platform of Yugoslavia was influenced by rapid sea level rise and an oceanic anoxic event during the Cenomanian-Turonian. Open-marine biota such as planktonic foraminifera, radiolarians, and locally even ammonites, associated with and bracketed by successions of typical shallow-water carbonates, indicate partial drowning of substantial areas of the platform during this time, suggestive furthermore that the rate of increase of water depth was locally great enough to outpace carbonate production. The presence of carbon-rich and fish-bearing platy limestones, commonly cherty, as an associated coeval facies indicates the development of anoxic or euxinic environments, and the stromatolitic laminations in such rocks are attributed to the action of bacterial mats. It is suggested that an extensive column of deoxygenated water developed in the neighboring Marche-Umbrian-Adriatic deep-water basin and was carried on to the carbonate platform during the Cenomanian-Turonian transgression.

A review of terrestrial and marine climates in the Cretaceous with implications for modelling the ‘Greenhouse Earth’

Article

Full-text available

Mar 1992
GEOL MAG

From the unique perspective of the geological record, it appears that the ‘Greenhouse Earth’ was a feature of climate for up to 80 % of the last 500 Ma, and that therefore our present glacially dominated climate is an anomaly. The Cretaceous in particular was a time of global warmth, an extreme greenhouse world apparently warmer than our current Earth. The geological record provides perspective and constraints against which the success of climate models can be evaluated. At present there are no ways of evaluating model predictions for the future of our ‘Greenhouse Earth’ until after the event. Retrodicting the past is therefore a very useful way of testing model sensitivity and robustness. The geological record tells us that the characteristics of the Cretaceous greenhouse world were a shallower equator-to-pole temperature gradient, shallow, well-stratified epicontinental seas with a tendency towards periodic dysaerobism, and a well-developed terrestrial flora extending to the high latitudes. Both marine and non-marine data show a global cooling trend throughout Late Cretaceous time, a trend that seems to correlate with declining atmospheric carbon dioxide.

Carbon- and oxygen-isotope stratigraphy of the English Chalk and Italian Scaglia and its palaeoclimatic significance

Article

Full-text available

Jan 1994
GEOL MAG

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

Oceanic Ridge Volumes and Sea-Level Change - An Error Analysis

Chapter

Jan 1984

Michelle Kominz

Oxygen and carbon isotopes from bulk carbonates and foraminiferal shells at DSDP sites 400, 401, 402, 403 and 406.

Article

Jan 1979

Isotope analyses have been performed on planktonic and benthic foraminifers from levels widely spaced in time (2 to 4 my) at Hole 400A and Site 401. In addition, isotope analyses of bulk carbonates from 250 levels from Holes 400A, 402A, and Sites 401, 403 and 406 are interpreted in terms of paleoceanographic changes. Their evolution is compared with the thermal evolution that can be deduced from foraminiferal analyses. -Authors

Cretaceous planktonic foraminiferal biostratrigraphy and evolutionary trends from the Bottacioine section, Gubbio, Italy

Article

Jan 1994

The "Scisti a Fucoidi" in the Umbria-Marche area: The Apecchiese road sections

Article

Jan 1989

Radiolaria

Article

Jan 1993

R.E. Casey

Carbon Isotope Fluctuations in Cretaceous Pelagic Limestones: Potential Stratigraphic and Petroleum Exploration Tool

Article

Jan 1980
AAPG BULL

Michael A. Ar Peter A. Scholle

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 1,000 closely spaced samples were analyzed during this study. At least seven major ^dgr13C excursions can be correlated from section to section. The most important "heavy events" occur near the Aptian-Albian and Cenomanian-Turonian boundaries, whereas "light events" are near the Jurassic-Cretaceous, Albian-Cenomanian, 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 stan ard 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.

The Mid-Cretaceous Organic-Rich Sediments from the Vocontian Zone of the French Southeast Basin

Chapter

Jan 1994

J.-G. Bréhéret

During Cretaceous time, the Vocontian basin, which is a part of the French “Bassin Subalpin Méridional”, was characterized by a pelagic sedimentation more or less diluted by fine siliciclastic supplies. In the series, several intervals display organic-rich sediments which are distributed from the Upper Hauterivian to the Lower Turonian. At least, certain organic-rich horizons or intervals appear to constitute local records of widespread oceanographical phenomena. These have been called oceanic anoxic events (OAE) by Schlanger and Jenkyns (1976), and this term has subsequently been used by a number of authors. However, the concept of OAE suffers from a certain vagueness as, for instance, it applies to relatively short-lived episodes (as for the Cenomanian-Turonian event) as well as to periods of more than 20 million years as for Aptian-Albian. More recently, a distinction was made of “subevents” (OASEs) in this last stratigraphical interval (Arthur et al. 1990). The accuracy of this terminology is discussed, thanks to the detailed study of the Aptian-Albian Marnes Bleues Formation. This Marnes Bleues Formation displays a variety of organic-rich sediments. They are recognized as belonging to four types according to their fabric (essentially degree of lamination) and to their organic content (as total organic carbon or TOC), following the example of Bralower and Thierstein (1984). They correspond to class 1 to class 4, from the poorest (< 0.7 % TOC) to the richest ones (usually > 2.5 % and up to 8 % TOC). The arrangement of the organic-rich layers in the series is not at random, but corresponds to an organization into a hierarchy. The study of this organization relies on the identification of sedimentary sequences at different scales. The Marnes Bleues are composed, for the most part, of the stacking of sequences of different orders which are superimposed. A banding is mainly distinguished thanks to a weak contrast in color (from light to dark gray). It presents a very high frequency, and the couplet “dark-light” may be referred to elementary sequences (Ferry 1991). This banding is not always detectable and in several intervals it displays a complex pattern. Most of dark layers belong to class 1 and class 2. Less order sequences are depicted, which very usually group five elementary sequences. These bundles occur very regularly and are particularly well identifiable. Nearly all of them are easily correlated on sections all over the basin. The analogy of these sequences with the genetic sequences described by Cross (1988) and by Guillocheau (1991) in other contexts is strong enough to suggest that they may be another expression of the same kind of sedimentary units generated by fluctuations in relative sea level. In several intervals (as the Lower Albian), these sequences are punctuated by black shales belonging to class 3 and often grouped by two or three. The crushing majority of organic-rich beds occur in such a way, and thus are typically periodites. The frequency (estimated within the limits of the stratigraphical resolution) of these sets of five elementary couplets suggests a possible consequence of variations in Earth’s orbital eccentricity. The close study of the position of organic-rich beds within the genetic sequences allows one to distinguish two types. A first type, “condensed”, occurs more or less in phase with carbonate-rich layers. It is interpreted as formed during lowerings in detrital supply, corresponding to episodes of small rises in relative see level and/or dry climatic phases. A second type, “fed”, is in opposite phase with carbonate-rich layers. It is better explained by small falls in relative sea level and/or wet climatic phases. In any case, these black-shale periodites correspond to a normal recurrent sedimentation which lasts during million years. As a whole, they represent the consequence of long-term trends in global climatic and oceanographic parameters. However, at present, no accurate inter-basinal correlations have been made for individual beds. On the other hand, several horizons are particularly noteworthy firstly because of their high organic content, secondly because they break the regular stacking of the basic sedimentation. They are composed of thin sequences with contrasted facies which record large fluctuations in oceanographical conditions. These beds are rare and aperiodic, and they constitute key beds at the scale of the Vocontian basin. Furthermore, these markers are recognized also in different basins at regional or even at global scale. They may be viewed as records of real events. They come within the framework of low-order sequences (third or second order according to the schemes of Vail et al. 1977). They correspond to the condensation of a whole genetic sequence or even of several, and are the result of episodes of major flooding. Their genesis was only possible because of the propensity for oceanic water to suboxia or anoxia.

Polycystine radiolarian distributions and enhancements related to oceanographic conditions in a hypothetical ocean

Article

Jan 1982
Trans Gulf Coast Assoc Geol Soc

Entwicklung und Paläoozeanographie mittelkretazischer Radiolarien der westlichen Tethys (Italien) und des Nordatlantiks

Article

Jan 1994

Jochen Erbacher

Mesozoic Radiolaria from the Atlantic Basin and its Borderlands

Article

Dec 1977

Helen P. Foreman

Mesozoic Radiolaria, primarily from Deep Sea Drilling cores, are surveyed. Maps indicate localities, ages, and usefulness of the occurrence. The new Amphipyndax tylotus Zone is defined and the next lower Amphipyndax enesseffi Zone is emended.

Oceanic anoxic conditions around the Cenomanian/Turonian boundary and the response of the biota

Article

Jan 1986

Planktonic Foraminifers from the Bermuda Rise, Deep Sea Drilling Project Legs 51, 52 and 53

Article

Feb 1980

Microstratigrafia e stratigrafia sequenziale. Studi sui depositi di piattaforma carbonatica, Cretacico del Monte Maggiore (Appennino Meridionale)

Article

Jan 1993

Radiolaria from the North Pacific, Deep Sea Drilling Project, Leg 32

Article

Aug 1975

H.P. Foreman

(A new biochronologic radiolarian zonation for the Early and Middle Cretaceous).[Un nouveau canevas biochronologique du Cretace inferieur et moyen: les biozones a Radiolaires.]

Article

Jan 1985

André Schaaf

The observation and sequential analysis of Radiolarians faunas collected in 42 oceanic sites (DSDP) and in a continental sampling (Maiolica lombarde) defines a new biozonation of Lower and Middle Cretaceous. Twenty-one zones, during 56 My (from -132 to -84 My) have been correlated with foraminifers and nannoplankton biozones as well as with the paleomagnetic scale.-from English summary

A carbonate carbon-isotope record from Aptian-Albian sediments of the Vocontian Trough (SE France)

Article

Jan 1991

The carbonate carbon isotope record established in sediments from the Vocontian Trough is more noisy than carbon isotope curves derived from pelagic sections. A correlation of the diagenetically altered Vocontian carbon isotope stratigraphy with a carbon isotope curve from a Tethyan pelagic section shows that an original, marine pattern was not completely destroyed. -from Authors

Cyclostratigraphy and foraminifera palaeoecology in Aptian/Albian pelagic sedimentary cycles in the Umbro-Marchean Apennines, central Italy[Zyklostratigraphie und Foraminiferen-Palokologie in pelagischen Sedimentationszyklen des Apt/Alb im Umbrisch-Marchischen Apennin (Mittelitalien)]

Article

Jan 1993

S.U. Noe

Aptian/Albian pelagic sedimentary cycles in the Umbro-Marchean Apennines (Central Italy), the Scisti a Fucoidi, were used for the investigation of a high-resolution cyclo- and biostratigraphy. Cyclicity reflects the ca. 20-ka precession cycle and the ca. 100-ka cycle of orbital eccentricity. The distributional patterns of the planktonic and benthonic foraminifera do not show any distinct relation to the small-scale climatic fluctuations. The distributional patterns of the planktonic foraminifera are the result of a generally high productivity in the surface water modified by periodic dissolution of the tests in the deep water. The benthonic foraminiferal assemblage strongly depends on the bottom water oxygenation. -from English summary

Lithostratigraphy and planktonic foraminiferal biostratigraphy of the Aptian-Albian "Scisti a Fucoidi' in the Piobbico core, Marche, Italy: background for cyclostratigraphy

Article

Jan 1989

Describes a varicolored pelagic sequence of thinly interbedded red and green marlstones and calcareous marlstones, dark gray to black Corg-rich calcareous shales, and light green-gray marly limestones and limestones. The variable colored lithotypes appear to be rhythmically deposited. Planktonic foraminiferal abundance varies from layer to layer. The variance is interpreted as due 1) to diagenesis in the Aptian interval, 2) to primary dissolution at the sediment-water interface in the middle darker portion of the core, and 3) to the alternation of stable to unstable conditions of the upper water column in the Late Albian, apparently in accord with orbital variations. -from Authors

Cretaceous radiolarians of the north Atlantic Ocean: ODP Leg 103 (Sites 638, 640, and 641) and DSDP Legs 93 (Site 603) and 47B (Site 398)

Chapter

Dec 1988

J. Thurow

Radiolarians form a remarkable part of the fossil plankton for Cretaceous sediments of the North Atlantic. Selected sites with long-term sedimentary successions of deep facies were studied. Preservation of the radiolarian faunas is generally poor, and the faunal abundance and diversity reflect the diagenetic history of the host sediment rather than the original faunal productivity. Several exceptions include abundant and some well-preserved radiolarian faunas from lower Campanian, Cenomanian/Turonian boundary, upper Albian, lower Albian, and Barremian sediments. These increases in radiolarian abundance and preservation coincide with well-established Cretaceous oceanic events in the north Atlantic. Typical faunal associations of these sections are described, and faunal associations from the Cenomanian/Turonian Boundary Event are documented for the first time in the North Atlantic. -from Author

Atlas Tethys Paleoenvironmental Maps

Book

Jan 1993

Milankovitch climatic origin of mid-Cretaceous black shale rhythms in central Italy

Article

Jun 1986

Timothy D Herbert

The Earth's orbital variations, reflected in Pleistocene ice volume, were also recorded in non-glacial times. Carbonate production in pelagic mid-Cretaceous sediments, quantified by calcium carbonate and optical densitometry time series, reflects the orbital eccentricity and precessional cycles. Minimal eccentricity brought deep-sea anoxia. Most of the sedimentary variability of this 100-Myr-old sequence lies within the Milankovitch (orbital) frequency band.

Biochronology and Paleontology of Mid-Cretaceous Radiolarians from Northern Apennines (Italy) and Betic Cordillera (Spain)

Article

Jan 1994

Luis O'Dogherty

Highly diverse radiolarian faunas of middle Cretaceous age have been recovered from pelagic and hemipelagic sequences recording the Barremian-Turonian interval in Mediterranean Regions. Several lithologies (limestones, cherty limestones, marls and siliceous shales) were thoroughly examined for radiolarian occurrences in continuous successions of deep-water facies. The study includes localities in the Umbria-Marche Apennines (Apulian Block) and on the External Zones of the Betic Cordillera (Southern Iberian Paleomargin). The taxonomy and biochronology of the Mid-Cretaceous radiolarians has been studied in order to construct a precise radiolarian zonation in the Western Mediterranean, on the basis of their vertical distribution. Only the true sequence of species in the fossil record allows one to establish the order in which they evolved. Therefore a detailed biochronological analysis was used as a basis for tracing evolutionary lineages and to elucidate the phylogenetic relationships of the examined taxa. Finally, generic and suprageneric classifications have been partly revised based on my own analysis of the faunal succession. The biochronology has been carried out by means of Unitary Association Method (Guex 1977, 1991). A database recording the appearance of 303 species in 29 superposed horizons selected from six hundred samples of seven sections has been used to establish a sequence of 21 Unitary Associations. Each of these associations is defined by the totality of characteristic species pairs. The biochronological analysis has allowed the definition of nine new radiolarian biochronologic units for the middle Cretaceous, each of which is labelled either as a zone or a subzone. These biochronologic units are tied to chronostratigraphy by means of planktonic Foraminifera and calcareous nannofossils previously studied by other authors at the same localities. Two major radiolarian faunal changes coincide with well established major Cretaceous oceanic anoxic events (OAE): early Aptian to late Albian (OAE 1A- OAE 1C) and Cenomanian-Turonian boundary (OAE 2). All radiolarian species (303) used in the biochronology have been described with complete synonymies. Illustrations include several specimens of each species in order to elucidate the morphologic variability. Three families, 17 genera and 84 species are described as new.

Ice age interludes during the time of Cretaceous greenhouse climate

Article

Jan 1991

The “Bonarelli Horizon” in the Central Apennines (Italy): Radiolarian biostratigraphy

Article

Jun 1991

The “Bonarelli Horizon”, of Cenomanian to Turonian age, is a thin (approximately one metre) layer within the Scaglia Bianca Formation of the Umbria sequence of central Italy. It consists of black mudstones rich in organic matter, silty shales and beds of radiolarian siltones and fine sandstones. The abundance of organic matter reflects the anoxic conditions prevailing during its deposition.Several sections (Valle del Bottaccione, Valle della Contessa, Monte Petrano, Valle del Burano and Gola del Furlo) show that the Bonarelli Horizon includes a “lower” radiolarian assemblage characterized by the presence of Novixitus mclaughlini, Thanarla pulchra, Holocryptocanium astiensis, Archaeodictyomitra sliteri, Pseudodictyomitra carpatica, and an “upper” assemblage where Alievium superbum is present in association with Crucella cachensis and Pseudoaulophacus putahensis. The transition between the “lower” and “upper” assemblages represents a faunal event that, on the basis of current knowledge of radiolarian biostratigraphy, suggests a correlation with the Cenomanian-Turonian boundary.

Distribution of Cenomanian Turonian organic facies in the western Mediterranean and along the adjacent Atlantic margin

Article

Jan 1990

Pre-Cenomanian sediments of the western Mediterranean and adjacent Atlantic margin are characterized by low total organic content (TOC) with an important terrestrial component. During the Cenomanian, TOC increased and the marine component became dominant, culminating around the Cenomanian-Turonian boundary with TOC up to 40%. After the Turonian, organic-rich sediments progressively disappeared and were replaced by more oxygenated sediments. Study methods include considering data from outcrops, DSDP/ODP sites, or petroleum wells. Detailed data from onshore locations allowed the development of high-resolution stratigraphy, analysis of depositional environment, and calculation of sedimentation rates. Analysis of these data indicates Cenoamnian-Turonian organic-rich sediments can be observed in a wide range of bathymetric settings. They are widespread in the western Mediterranean and Atlantic and have been especially studied in Italy (Apennines, southern Alps), Tunisia (Bahloul), Algeria, Morocco (Rif Mountains, Atlas Mountains, Tarfaya), Gibraltar arch, Spain (Betics, Bay of Biscay, Galicia margin), Senegal (Cape Verde basin, Casamance), and Nigeria (Benue, Calabar flank).

Mid-Cretaceous of the Gibraltar Arch Area

Article

Jan 1986

Mid-Cretaceous depositional environments of the Gibraltar Arch and adjacent areas exhibit at the Cenomanian-Turonian boundary a special type of organic carbon-rich siliceous sedimentation which is intercalated in all the different environments—from the shelf down to the deep—of this area. This will be called the Cenomanian-Turonian Boundary Event (CTBE). Summarizing the most important features of the CTBE it can be pointed out: (1) the initiation of the CTBE is nearly coeval; (2) very high TOCs, especially at the base of Turonian; (3) kerogen is exclusively of type (I-) II in the undiluted strata; (4) independent of given palaeogeographic setting (e.g. E. and W. margin of the Atlantic ocean); (5) bituminous sedimentation is also very pronounced in environments with high detrital input and strong dilution (e.g. deep sea fans). Here too, most strata comprise kerogen of type II; (6) as far as we know, there is a striking co-occurrence of these sediments with strong enrichment in biogenic silica from diagenetically altered radiolaria, but there is no link between good preservation of radiolaria and bituminous sediments (e.g. Scaglia-facies); (7) rich radiolarian faunas are common in the carbon-rich and carbon-free sediments of shallow marine and deep sea environments; (8) the important change in the evolution of planktonic organisms (foraminifera/radiolaria) which marks the Cenomanian-Turonian boundary coincides with the peak of anoxic conditions and biogenic silica-rich sedimentation. All these features of the CTBE observed in the Gibraltar Arch area are comparable with coeval DSDP-facies in the North Atlantic and allow on-shore-off-shore tracing of the CTBE.

Phosphogenesis, carbon-isotope stratigraphy, and carbonate-platform evolution along the Lower Cretaceous northern Tethyan margin

Article

Jun 1994

The paper distinguishes three different stages in the evolution of the Tithonian (Late Jurassic) to Aptian (Early Cretaceous) northern Tethyan carbonate platform: 1) carbonate production in the coral-oolite mode, 2) carbonate production in the crinoid-bryozoan mode, and 3) platform retrogradation and destruction, condensation, and phosphogenesis. The δ13C stratigraphies obtained from Valanginian-Hauterivian and Aptian-Albian hemipelagic successions beyond the platform correlate well with the Early Cretaceous pelagic δ13C record. -from Authors

Variable marine productivity and high eolian input recorded by rhythmic black shales in Mid-Cretaceous pelagic deposits from central Italy

Article

Dec 1986

Rhythmic interbedding of dark gray to black, laminated, calcareous shale (black shale) with lighter colored limestone, marlstone, or mudstone is a prominent feature of the Aptian-Albian Scisti a Fucoidi in the Italian Apennines. Organic carbon contents of most black shales in the Scisti are less than 1.5%. Sedimentary structures and levels of bioturbation indicate that periods of poorly oxygenated benthic conditions alternated with more extended periods of well-oxygenated benthic conditions during deposition of the Scisti. Geoochemical, isotopic, and visual studies of organic matter indicate variable marine productivity (generally low) and relatively high input of eolian dust during deposition of the Scisti black shales. One organic-rich black shale near the middle of the formation may represent a brief period of stimulated marine fertility and high productivity coincident with benthic stagnation. Production of warm saline brines in evaporitic coastal settings, sinking of these brines into deepwater basinal settings, and development of stable salinity stratification is suggested as a causal linkage between arid climate, strong winds, and poorly oxygenated bottom waters in the Alpine-Mediterranean Tethys during mid-Cretaceous time.

Valanginian to Aptian calcareous nannofossil stratigraphy and correlation with the upper M-sequence magnetic anomalies

Article

Mar 1987
Mar Micropaleontol

Timothy J Bralower

Calcareous nannofossil stratigraphy has been investigated in Lower Cretaceous Italian sections at Gorgo a Cerbara, Presale and Frontale (all in the Umbrian Apennines) and at Cismon (Southern Alps). A modified sample preparation technique has allowed a thorough stratigraphic study of the well-lithified Maiolica limestone and although nannofossil preservation is generally quite poor, the major Valanginian to Aptian marker species can be detected. Nine nannofossil events can be determined and correlated to magnetic stratigraphies previously established in these sections. Nannofossil stratigraphy confirms most magnetostratigraphic correlations made between sections and allows a more precise correlation of magnetic Chrons M-0 to M-11 with the Valanginian, Hauterivian, Barremian and Aptian stages. The results obtained differ considerably from previous timescales. Nannofossil events recorded in the various sections may be time-transgressive by as much as one magnetic chron, probably due to differential preservation.

La pyrolyse Rock-Eval et ses applications. Deuxi??me partie

Article

Nov 1985

Conçue pour répondre aux besoins de l'exploration pétrolière, la méthode de pyrolyse Rock-Eval est maintenant largement utilisée. Elle fournit, en effet, et d'une façon rapide, différentes informations sur le contenu organique des roches, telles que le potentiel pétrolier des séries rencontrées, la nature des kérogènes, leur état de maturation. En ce qui concerne le matériel, deux nouvelles versions ont été mises au point à l'Institut Français du Pétrole (IFP) depuis l'apparition en 1977 des premiers appareils Rock-Eval : un Rock-Eval II complètement automatisé grâce à un microprocesseur et doté, en option, d'un module de dosage du carbone organique; un Rock-Eval III (Oil Show Analyzer) qui se distingue du précédent par le fait qu'il analyse séparément le gaz et l'huile et qu'il effectue le dosage du carbone organique à la place du pic S3. En ce qui concerne l'interprétation de la méthode, l'expérience acquise tant par les applications aux bassins sédimentaires que par les études expérimentales menées en laboratoire a permis de mieux connaître les paramètres utilisés (pics S1, S2, S3, température de pyrolyse Tmax) à travers leurs variations et, de là, de mieux discerner les limites d'application de la méthode. En ce qui concerne l'application de la méthode, la représentation verticale des résultats sous forme de logs géochimiques conduit à une interprétation à la fois efficace et pratique. Des abaques et des diagrammes de référence permettent de caractériser les roches mères (potentiels pétroliers, types de matière organique, degré d'évolution, altérations. . . ) ainsi que les phénomènes de migration. L'établissement de cartes géochimiques à l'échelle du bassin devient alors possible. Enfin la méthode est sortie du domaine de l'exploration pétrolière proprement dite pour trouver des applications à l'étude des charbons, des roches bitumineuses, des sédiments récents et même aux techniques du raffinage et de la récupération secondaire des bruts. The Rock-Eval pyrolysis method was designed to meet the needs of petroleum prospection and has now gained widespread use. It quickly provides different data on the organic content of rocks, such as the petroleum potential of series encountered, the nature of kerogens and their state of maturity. Two new versions of this equipment have been developed by Institut Français du Pétrole (IFP) since the appearance of the first Rock-Eval devices in 1977. One is a Rock-Eval II that is completely automated thanks to its microprocessor and is also equipped with a module for determining the organic-carbon content. The other is a Rock-Eval III (Oil Show Analyzer) which is different from the preceding one in that it makes a separate analysis of gas and oil as well as determining the organic-carbon content in place of peak S3. Concerning the interpretation of the method, experience gained both by applications to sedimentary basins and by experimental investigations in the laboratory has provided a better understanding of the parameters used (peaks S1, S2 and S3, pyrolysis temperature Tmax) through their variations and, from this, better insight into the application limits of the method. Concerning the application of the method, the vertical representation of results in the form of geochemical logs leads to an interpretation that is both effective and practical. Reference charts and diagrams are used to characterize source rocks (petroleum potentials, types of organic matter, degree of evolution, weathering, etc. ) as well as migration phenomena. The compiling of geochemical maps on a basin-wide scale then becomes possible. Likewise, the method has left the field of petroleum prospection per se and found applications in the analyzing of coals, bituminous rocks, recent sediments and even techniques of the refining and secondary recovery of crude oils.

Equivalent radiolarian ages from ophiolitic terranes of Cyprus and Oman

Article

Jan 1985
GEOLOGY

Radiolarian biostratigraphy shows that umberiferous strata overlying the Troodos ophiolite in Cyprus are Turonian in age and are thus essentially contemporaneous with similar strata that overlie the Samail ophiolite in Oman. However, this radiolarian age is markedly older than Campanian isotopic ages measured on the underlying rocks of the Troodos ophiolite. The revised age for the umbers indicates that the Troodos lavas were formed no later than Turonian time. The presence of overlying autochthonous Maastrichtian chalks restricts the emplacement of the Troodos ophiolite to the Late Cretaceous (Santonian to early Maastrichtian).

Evolution patterns of radiolaria and organic matter variations: A new approach to identify sea-level changes in mid-Cretaceous pelagic environments

Article

Jun 1996
GEOLOGY

A water depth model for the evolution of the planktonic Foraminifera

Article

Jul 1980

Malcolm B. Hart

Recent papers on the evolution of the planktonic Foraminiferida have stressed the importance of repeated patterns1,2 in the Neogene and Palaeogene, as well as in the Cretaceous1–4. Most authors have recognized the importance of gross morphological characters (the biocharacters of Steineck and Fleischer2) and used them to illustrate the evolution of the superfamily Glo-bigerinacea, as well as a prime tool in classification. Cifelli1 and Frerichs4 relate such patterns of evolution to the available palaeotemperature data5, and while temperature is clearly important I shall show that it is not the complete story. Here the evolution of the planktonic Foraminiferida is reconsidered in the light of recent advances in the understanding of distributional controls of the modern fauna. I suggest that well-known ‘iterative’ trends indicate successive attempts at colonizing deeper levels in the water column.

Organic Petrology of Deep Sea Sediments: A Compilation of Results from the Ocean Drilling Program and the Deep Sea Drilling Project

Article

Nov 1994

A comprehensive overview of the organic petrology of Triassic to Recent deep sea sediments is presented. The data, which are derived from studies in the framework of the Ocean Drilling Program and the former Deep Sea Drilling Project, are discussed with respect to the plate tectonic setting and the oceanographic environment. The discussion reveals the following trends: (1) Early stages of the evolution of oceans are often characterized by deposition of sediments with high proportions of terrigenous organic matter including wood and coal on the one hand and by the deposition of black-shales, rich in marine macerals, in silled basins with restricted water circulation on the other hand. (2) Turbidity sedimentation which carries terrigenous material into the deep ocean plays an important role along passive continential margins, e.g., in submarine fans. Here, the inertinite/vitrinite ratio increases with increasing distance to the continents. The organic matter in central oceans is consequently also characterized by high proportions of often small-sized inertinite. A very special depositional setting occurs within central oceans on top of drowning volcanoes. There, alginite- and vitrinite-rich sediments are deposited in shallow water. Vitrinite is derived from plants on the adjacent still subaerial volcanic areas. (3) Sediments deposited along active continental margins in trench-slope transition zones are often rich in recycled vitrinite. This is caused by the erosion of sedimentary rocks in the near mountain ranges and the extreme frequency of turbidity currents transporting the reworked organic matter into the deep ocean. (4) Organic sedimentation not only depends on the flux of terrigenous material, but also on bioproductivity. Therefore, upwelling-related high productivity may greatly affect the maceral composition along active and passive continental margins. Organic matter-rich sediments in upwelling areas are usually characterized by very high proportions of amorphous organic matter of marine origin. (5) Similar to rifted continental margins, a variety of sedimentary processes occur in back-arc basins. For example, black shales rich in marine macerals and turbidites and slumps often rich in terrigenous macerals may be deposited. Back-arc basins and areas where midocean ridges are subducted are characterized by thermal hydrocarbon generation at shallow depth.

Influence of Oceanic Anoxic Events on the evolution of mid-Cretaceous Radiolaria in the North Atlantic and Western Tethys

Abstract

No full-text available

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