Fig 1 - uploaded by Aurora Grandal-d'Anglade
Content may be subject to copyright.
A. Map of the Iberian Peninsula showing two major rivers mentioned in text and location of area in Part B. B. Map of the area around Cova da Arcoia, the cave from which Stalagmite ESP03 was taken.
Source publication
A small stalagmite from Cova da Arcoia in the Serra do Courel of northwestern Spain provides a record both of general climate change across the Holocene and of shorter-term shifts between wetter and drier conditions. Nineteen U-series dates from 9.3 ka to the present provide a chronology of the stalagmite with uncertainties of commonly only decades...
Contexts in source publication
Context 1
... 7. Data from Galician stalagmite ESP03 in the context of data from other palaeoenvironmental records. A. Plot of abundance of ice-rafted debris in the North Atlantic (Bond et al., 2001). B. Plot of stable isotope data from Greenland ice cores from Johnsen et al., 2001. C. Markers for preserved intervals from Fig. 6, where each is designated PI1, PI2, etc. D. Markers for surfaces listed in Table 2 and represented in Fig. 6. Thicker bars, rather than lines, indicate surfaces at which a signi fi cant hiatus is inferred. “ E ” s indicate Type E surfaces; longer vertical black lines also represent Type L surfaces. E. Stable isotope data from ESP03. Small numerals next to symbols for stable isotope data indicate numbers of speci fi c samples mentioned in text; these numbers are also used in Figs. 2, 5, and 8. Vertical bars showing intervals of calcite with lesser values of δ 18 O at Kaite Cave are from Domínguez-Villar et al. (2009). F. Qualitative interpretation of changing climatic conditions, as suggested by Fig. 8. G. Selected pollen data from Laguna Lucenza, a lake near the cave from which Stalagmite ESP03 was taken (see Fig. 1).
...
Context 2
... the broadest scale, the Holocene is considered a period of relative climate stability, in contrast to the variability in climate from interglacial to glacial maximum in the 100,000 years that preceded the Holocene. However, signi fi cant climate change has occurred in the Holocene (Roberts, 1998; Old fi eld, 2003), and recent work has documented signi fi cant temporal and geographic variation of major climatic intervals within the Holocene (e.g., Davis et al., 2003; Fisher and Koerner, 2003; Mayewski et al., 2004). Furthermore, work of the last few decades has documented that some climate change has been remarkably abrupt (e.g., Berger and Labeyrie, 1987; National Research Council, 2002). As a contribution to the emerging picture of climate change in the Holocene, this paper reports on a stalagmite from northwestern Spain that spans the last ten thousand years. Stalagmites have many characteristics from which palaeoclimate can be inferred (Gascoyne, 1992). These include radiometric age (Harmon et al., 1975; Edwards et al., 1987; Lauritzen, 2003), variation of C and O stable isotopes (McDermott, 2004), trace element chemistry (Verheyden, 2004; Fairchild and Treble, 2009), UV-stimulated fl uorescence (Shopov et al., 1994; Baker et al., 1998), pollen content (McGarry and Caseldine, 2004), varying detrital content (Railsback et al., 1999; Webster et al., 2007), petrographic relationships (Railsback, 2000; Turgeon and Lundberg, 2001; Frisia et al., 2002) and, perhaps most fundamentally, changing mineralogy (González and Lohmann, 1988; Railsback et al., 1994; Frisia et al., 2002). With regard to the two principal CaCO 3 minerals, aragonite and calcite, many studies have linked precipitation of aragonite to more extensive evaporation (Murray, 1954; Pobeguin, 1965; Siegel, 1965; Siegel and Dort, 1966; Thrailkill, 1971; Cabrol and Coudray, 1982) and to higher temperature (Burton and Walter, 1987; Morse et al., 1997) than the conditions in which calcite forms. The stalagmite described herein contains both calcite and aragonite in layers bounded by critical petrographic surfaces and characterized by abrupt shifts in C isotope composition. These characteristics, combined with 19 radiometric ages, provide a record of both long-term trends and shorter shifts in climate in the Atlantic-facing highlands of northwestern Spain during the Holocene. The stalagmite described here, which was designated Stalagmite ESP03 in the Sedimentary Geochemistry Laboratory of the University of Georgia (U.S.A.), comes from Cova da Arcoia in the Serra do Courel in the westernmost Cordillera Cantabrica (Fig. 1). Cova da Arcoia is at 42° 36 ′ 44.39 ′′ N latitude and 7° 05 ′ 06.32 ′′ W longitude, near the village of Céramo in the province of Lugo, in the easternmost portion of the autonomous community of Galicia, in northwestern Spain. Cova da Arcoia sits at 1240 masl, whereas the summits upslope from the cave have elevations of 1500 to 1600 m, and the valley fl oors below are at 900 to 1100 m. The cave is on a north-facing slope. Mean annual precipitation in the region around Cova da Arcoia is about 2500 mm (Leira and Santos, 2002), with most precipitation in the cooler months (Walter and Lieth, 1960). The native vegetation represents a transition from Eurosiberian to Mediterranean (Izco Sevillano et al., 1982, cited in Leira and Santos, 2002), although the present landscape is largely scrubland and pasture (Leira and Santos, 2002). The whole zone has been affected during the Pleistocene by the Quaternary glaciations, developing the main karstic systems under the ice accumulations and helped by the subglacial melt waters. The fauna that occupied the territory during the Upper Pleistocene to Holocene, including the human species, is known in detail. The Holocene fossil record in Arcoia and surrounding caves includes Brown bear ( Ursus arctos ) and aurochs ( Bos primigenius ) in the early Holocene, along with Epipaleolithic human remains (Grandal-d'Anglade et al., 2010). Domestic faunas (mainly cattle, sheep and goat) are the most common fi nds of Middle to Late Holocene age in the region. Brown bear have been found in Arcoia and Sima Paleira caves, both at high altitude, since the Pleistocene. There is a hiatus in the macromammal fossil record during the glacial maximum. Remains of Holocene brown bears have been found in several caves in the area (Purruñal, Tarelo, Sima Paleira and A Tara), but they only reoccupied caves at high altitude (Sima Paleira) in the climatic optimum, after the cold episode at 8.2 ka (Grandal-d'Anglade et al., 1997; Vidal Romaní et al., 2010; García-Vázquez et al., in press). The stalagmite was located about 50 m from the present cave entrance, at the back of a room about 8 m by 10 m in size. It was less than 10 m from an original cave entrance that was sealed by a collapse that took place more than 40 kyr BP. The stalagmite had grown on the top of one of the limestone blocks that had fallen in the collapse of the original entrance. That collapse buried the bones of Ursus arctos , the brown bear dated at more than 40 kyr (Grandal-d'Anglade et al., 2010), which yields the minimum age for the collapse of the original entrance, long before the deposition of Stalagmite ESP03. The thickness of the rock over the cave at the stalagmite's location is at most 5 m. The pH of the drip water onto the stalagmite at the time of collection was 8.25, and the temperature of that water was 8.1 °C. Drip water concentrations of Mg and Ca were 0.32 and 47.9 mg/kg respectively, yielding a molar Mg/Ca ratio of 0.011. Meteoric precipitation in the region has values of δ 18 O that range from monthly averages of − 9 to − 6 ‰ relative to SMOW during cooler and wetter months and averages of − 6 to − 3 ‰ in warmer and drier months (Walter and Lieth, 1960; IAEA, 2006), suggesting a weighted average of − 6 to − 7. Domínguez-Villar et al. (2008) showed that δ 18 O of rainwater increases with temperature in the northwestern Iberian Peninsula, and most relevantly at the inland stations of Léon and Bragança, each of which is about 130 km from Cova da Arcoia. Their Table 3 also shows that δ 18 O of rainwater decreases with increasing rainfall in the region and thus shows a typical “ amount effect ” . Nineteen samples of ca. 100 mg each were drilled along the central growth axis of the ESP03 stalagmite and dated by inductively coupled plasma mass spectrometry (ICP-MS) in the Stable Isotope Laboratory at the University of Minnesota following procedures described in Edwards et al. (1987) and Cheng et al. (2000). The dating results were calculated using half-lives determined by Cheng et al. (2000) and reported with analytical errors of 2 σ of the mean (Table 1). We corrected for initial 230 Th, using a generic “ bulk earth ” atomic 230 Th/ 232 Th ratio of 4.4 ×10 − 6 . We have assumed an error of ±50% in this value. The error in the “ corrected ” age incorporates this uncertainty. This error estimate is robust toward lower 230 Th/ 232 Th values, as zero is the theoretical limit, and documented values under 2 ×10 − 6 are rare. Whereas 230 Th/ 232 Th values higher than our upper limit have been documented, our estimate in this direction is reasonable. For C and O stable isotope analyses, 104 powdered samples numbered from 007 to 110 from lowest to highest were taken from the stalagmite with a dental handpiece and fi ne dental bur. X-ray diffraction showed that four of these samples contained mixtures of calcite and aragonite, and so they were discarded. 100 samples thus remained and are reported here. The layers of ...
Context 3
... stalagmite described here, which was designated Stalagmite ESP03 in the Sedimentary Geochemistry Laboratory of the University of Georgia (U.S.A.), comes from Cova da Arcoia in the Serra do Courel in the westernmost Cordillera Cantabrica (Fig. 1). Cova da Arcoia is at 42° 36′ 44.39″ N latitude and 7° 05′ 06.32″ W longitude, near the village of Céramo in the province of Lugo, in the easternmost portion of the autonomous community of Galicia, in northwestern Spain. Cova da Arcoia sits at 1240 masl, whereas the summits upslope from the cave have elevations of 1500 to 1600 m, and ...
Context 4
... in Figs. 2, 5, and 8. Vertical bars showing intervals of calcite with lesser values of δ 18 O at Kaite Cave are from Domínguez-Villar et al. (2009). F. Qualitative interpretation of changing climatic conditions, as suggested by Fig. 8. G. Selected pollen data from Laguna Lucenza, a lake near the cave from which Stalagmite ESP03 was taken (see Fig. ...
Similar publications
The Meso-Neoproterozoic strata are wildly distributed in North China Craton (NCC), of which Changchengian strata are most widely developed. Taking Changchengian strata in south margin of NCC as the study object, and combined with comprehensive analysis of isotopic chronology and petrology, it can be concluded that the Xiong'er rift is a plume rift...
Citations
... The same process was postulated for the formation of elongated secondary pores along the boundaries of neighboring calcite crystals (cf. Railsback et al., 2011Railsback et al., , 2013Perrin et al., 2014). Jones (2009) also demonstrated highly irregular solutionally enlarged intercrystalline boundaries of calcite crystals coated with P-rich precipitates resulting from the activity of microorganisms (actinomycetes). ...
Interactions between bat guano and speleothems were studied in caves of Slovakia (Domica, Drienovská, and Jasovská caves) and Poland (Nietoperzowa Cave). This contribution focuses on the estimation of the rate of guano-induced corrosion of carbonates and on the transformations of speleothems caused by the corrosion. The intense interaction between bat guano accumulations and cave carbonates is mainly controlled by the chemical composition of guano. Corrosion of carbonates by guano leachates, suggested by negative calcite saturation index, was confirmed by weight loss of experimental carbonate tablets exposed to interaction with guano in situ in caves, and under laboratory conditions. The calculated corrosion rate of the tablets was up to 0.111 mm/y. However, measurements of selected corrosion forms in the studied caves, compared to the guano 14C age, suggest rates of the corrosion up to 0.65 mm/y. Transport of aggressive guano leachates is possible in the presence of water; increased drip water supply is considered as contributing to the higher dissolution rates. Crystallization of phosphates as byproducts of the interaction of guano with carbonates can also alter the dissolution process. Phosphates, represented by ardealite, brushite, and hydroxylapatite, were observed on the surfaces of experimental tablets and speleothems alike. Interestingly, hydroxylapatite was the only mineral associated with guano-related hiatuses within speleothem sections. Phosphates are usually accompanied by various dissolution features, such as corrosion pits and considerably dissolved calcite crystals. Dissolution features currently forming on speleothem surfaces are analogous to those identified in the fossil record. U-series dating of guano corrosion episodes within stalagmites from Domica and Drienovská caves indicates their Pleistocene age, while within a flowstone from Nietoperzowa Cave, a Holocene age. Considerable guano accumulations are common in low-latitude caves, whereas in temperate climatic zones guano accumulates irregularly in space and time. The guano accumulations are usually restricted to cave sections distant no more than few hundred meters from the nearest entrance. Considering the widespread distribution of bats across the globe, this process is expected to be common in caves. Nevertheless, the random distribution of guano in caves and its temporal deposition, but also the climate-dependent availability of water, suggest that guano-induced corrosion can be regarded as a site specific process.
... This lowering in lake water level corresponds with one of the main Holocene rapid climate changes (Mayewski et al., 2004) that corresponds to a globally detected dry and cold event centred at 9.3 ka cal BP (Fletcher and Zielhofer, 2013;Haas et al., 1998;Rasmussen et al., 2006), expressed as an episode of reduced rain fall and decreasing fluvial activity in Mediterranean areas (Magny et al., 2002) and dry episodes in the western Mediterranean (Budsky et al., 2019;Fletcher et al., 2010;Fletcher and Zielhofer, 2013;Frigola et al., 2007). This situation agrees with the interpre tations of northward shift of the westerly storm track (Budsky et al., 2019;Walczak et al., 2015), as pointed out by records of increased moisture from Scandinavia (Bakke et al., 2009) and reduced moisture from southern France (Genty et al., 2006;Wirth et al., 2013) and northern Iberia (Aranbarri et al., 2014;Railsback et al., 2011) at this time. ...
... Some variations in facies and geo chemical indicators are also shown throughout fluvial sediments of Unit 4 (Figures 3, 4 and 6); the variations in PC1 to PC4 through time could indicate environmental and climatic changes, apparently related to Bond events (Bond et al., 2001) but their timing and paleoenvironmental meaning must be cautiously con sidered since a better chronological control for Unit 4 would be desirable. Dry conditions across much of Iberia between ca. 8 and 5 kyr BP are suggested by many stalagmite records (Baldini et al., 2019;Moreno et al., 2017;Railsback et al., 2011), and a sharp decrease of precipitation in northern Iberia (Stoll et al., 2013). Other lake records from Spain JambrinaEnríquez et al., 2014;Moreno et al., 2011) and the pollenbased climate reconstruction from Mauri et al. (2015), as well as the lacustrine δ 18 O record from ostracod shells in Morocco (Zielhofer et al., 2019), support relatively drier conditions increasing in Iberia and north Africa. ...
Volcanic eruptions are key drivers of climate variability, with complex environmental consequences at regional and local scales that are rarely documented
in high-resolution sedimentary records. In this work we present the results of a 15 m long paleolake core (Pla de les Preses core, Vall d’en Bas, Girona,
NE Spain) covering the Late Pleistocene-Holocene transition. Multiproxy analyses including chronostratigraphy, sedimentology, micropalaeontology
and geochemistry are used to reconstruct the paleoenvironmental framework of the Late Pleistocene-Holocene transition and to detect the youngest
Holocene volcanic eruptions in the Garrotxa Volcanic Field (GVF) and the Iberian Peninsula. The studied sedimentary record covers the last ca. 13.5 ka
cal BP and was punctuated by several rapid climatic changes including the 9.3, 8.2 and 7.1 ka events, affecting the hydrological evolution of a barrier-lake
formed due to the volcanic damming of the Fluvià river. Sedimentological and geochemical analyses unveil the environmental history of Vall d’en Bas valley;
the formation of a lacustrine area within a fluvial environment around 13.5 ka cal BP and later a wetland phase between 9.3 and 8.2 ka cal BP. Abrupt
sedimentary changes marking the onset and demise of the wetland phase were linked to hemispheric cooling and drying events (e.g. 9.3 and 8.2 ka cal BP),
provoking a decline in the water table during these phases. In addition, 30 tephra layers are detected thorough the core, showing previously unknown
intense volcanic activity from 13.5 to 8.3 ka cal BP in the GVF. In that sense, the Pla de les Preses sequence provides, for the first time, evidence for early
Holocene volcanic activity in NE Iberia that should be taken into account in future tephra studies in the western Mediterranean realm.
... Trace element data corroborates this shift with distinct changes of several element/calcium ratios, where Mg/Ca is higher in calcite compared to aragonite and Sr/Ca, U/Ca, and Ba/Ca are all lower in calcite than aragonite (Fig. 2a). This calcite-to-aragonite transition in itself supports a shift towards drier conditions because aragonite is preferentially deposited with more extensive evaporation and PCP or PAP [58][59][60] . The darker, dirty layer between the calcite-aragonite transition marks a hiatus between the two deposition phases ( Supplementary Fig. S5). ...
The 4.2-kiloyear event has been described as a global megadrought that transformed multiple Bronze Age complex societies, including the Indus Civilization, located in a sensitive transition zone with a bimodal (summer and winter) rainfall regime. Here we reconstruct changes in summer and winter rainfall from trace elements and oxygen, carbon, and calcium isotopes of a speleothem from Dharamjali Cave in the Himalaya spanning 4.2-3.1 thousand years ago. We find a 230-year period of increased summer and winter drought frequency between 4.2 and 3.97 thousand years ago, with multi-decadal aridity events centered on 4.19, 4.11, and 4.02 thousand years ago. The sub-annually resolved record puts seasonal variability on a human decision-making timescale, and shows that repeated intensely dry periods spanned multiple generations. The record highlights the deficits in winter and summer rainfall during the urban phase of the Indus Civilization, which prompted adaptation through flexible, self-reliant, and drought-resistant agricultural strategies.
... Consistently, lake records present in the central-southern region of the pre-Pyrenees show a delay in the onset of wet conditions (9.5 kyr BP) and a decrease in humidity after 5e4.5 kyr BP (Morell on et al., 2009), a pattern that is supported by terrestrial proxies obtained from western Mediterranean marine records (Fletcher et al., 2013;Frigola et al., 2007). Several Holocene speleothem records have also been obtained from caves in northern Spain, but some are discontinuous (e.g., Serra do Courel; Railsback et al., 2011) or do not cover the entire interglacial (Martín-Chivelet et al., 2011;Rossi et al., 2018). In general, orbital forcing clearly exerted a first-order control on speleothem growth, as shown by an increase in the relative abundance of speleothems (Stoll et al., 2013). ...
... The onset of the Holocene has not been well captured by Iberian speleothems as most of them started to grow after 10e9.5 kyrs BP (Railsback et al., 2011;Stoll et al., 2013;Walczak et al., 2015), once optimum climatic conditions in terms of temperature and humidity were attained. Even so, there are few speleothem records in northern Spain that cover the climate transition between the YD and the Holocene (Baldini et al., , 2019Bernal-Wormull et al., 2021;Moreno et al., 2017;Rossi et al., 2018). ...
... Material Fig. S8 and Fig. S10) while speleothem growth in southern Iberia stopped (Walczak et al., 2015). Generally dry conditions across much of Iberia between ca. 8 to 5 kyr BP are suggested by positive d 13 C excursions in the northwest Iberian Cova de Arcoia (Railsback et al., 2011), the GAR-01 stalagmite (Baldini et al., 2019), stalagmites from caves in the Iberian range growing during 8.5e4.8 ka and a sharp decrease of precipitation derived from growth rates of 11 stalagmites on the Cantabrian coast (Stoll et al., 2013). Similarly, the long-term trend in carbon and oxygen isotopic variability of the composite record of six stalagmites from Buraca Gloriosa (BG) in western Portugal (Thatcher et al., 2020) support increasingly dry conditions in Iberia and North Africa during the Northgrippian. ...
Recent hydroclimate studies on the Iberian Peninsula have shown a complex regional pattern in timing and intensity of climate change spanning the Younger Dryas and the Holocene. These changes are due to multifaceted interactions between climate variability that characterizes the Atlantic Ocean region and hydroclimatic processes associated with the Mediterranean climate, thus making it difficult to reconstruct centennial-and millennial-scale variability in rainfall. In this study we present a composite and continuous isotopic record (d 13 C and d 18 O) consisting of four stalagmites from Mendukilo cave (MEN composite) in the western Pyrenees covering the Younger Dryas and the entire Holocene. This record reveals millennial-scale shifts in carbon isotopes in response to changes in the hydroclimate in the northern part of Iberia. The MEN oxygen isotopes show little variation on millenial time scales but reveal centennial changes that correlate with North Atlantic events (e.g., the 8.2 kyr BP cooling event). We observe a delay in the onset of humid conditions in the early Holocene and a subsequent trend towards drier and colder conditions between 6.0 and 2.5 kyr BP. This new, high-resolution and replicated spe-leothem record denotes the complex connection that exists between the North Atlantic and Western Europe during last millennia and the strong regional heterogeneity of the hydroclimate of Iberia during this time.
... Due to its proximity to the North Atlantic, south-western Europe is a climatologically important region for studying the impact of AMOC perturbations (Baldini et al., 2015). Several highquality speleothem records describe the Holocene climate of this region in terms of rainfall amount and/or seasonality (Domínguez-Villar et al., 2008;Railsback et al., 2011;Smith et al., 2016;Moreno et al., 2017;Baldini et al., 2019;Benson et al., 2021). Specifically, the regional climatic impact of the 8.2 ka event has mainly been described in terms of hydrological change from these studies. ...
... The majority of regional studies report the event as a wet interval (e.g. Railsback et al., 2011;Baldini et al., 2019;Benson et al., 2021) although with conflicting interpretations of whether it was a change in total annual rainfall amount or changes in the seasonal distribution of rainfall (i.e. more winter rainfall), whilst some ambiguity remains over event timing. Additionally, in Kaite Cave (northern Spain) two δ 18 O anomalies, separated by ∼ 140 years, have been interpreted to trace modifications of the isotopic composition of the ocean surface in response to successive discharges of isotopically depleted meltwaters of lakes Agassiz and Ojibway (Domínguez-Villar et al., 2009). ...
... precipitation) at the 8.2 ka event in south-western Europe are not yet clearly understood. -Villar et al., 2009-Villar et al., , 2017, GdL (Galeria das Lâminas; Benson et al., 2021), Chaara (Chaara Cave; Ait Brahim et al., 2019), Asiul (Cueva de Asiul; Smith et al., 2016), Arcoia (Cova da Arcoia; Railsback et al., 2011) and Villars (Villars Cave; Ruan, 2016). Location of the Santander GNIP station is indicated by an orange triangle. ...
The 8.2 ka event is regarded as the most prominent climate anomaly of the Holocene and is thought to have been triggered by a meltwater release to the North Atlantic that was of sufficient magnitude to disrupt the Atlantic Meridional Overturning Circulation (AMOC). It is most clearly captured in Greenland ice-core records, where it is reported as a cold and dry anomaly lasting ∼ 160 years, from 8.25 ± 0.05 until 8.09 ± 0.05 ka (Thomas et al., 2007). It is also recorded in several archives in the North Atlantic region; however, its interpreted timing, evolution and impacts vary significantly. This inconsistency is commonly attributed to poorly constrained chronologies and/or inadequately resolved time series. Here we present a high-resolution speleothem record of early Holocene palaeoclimate from El Soplao Cave in northern Spain, a region pertinent to studying the impacts of AMOC perturbations on south-western Europe. We explore the timing and impact of the 8.2 ka event on a decadal scale by coupling speleothem stable carbon and oxygen isotopic ratios, trace element ratios (Mg / Ca and Sr / Ca), and growth rate. Throughout the entire speleothem record, δ18O variability is related to changes in effective recharge. This is supported by the pattern of changes in δ13C, Mg / Ca and growth rate. The 8.2 ka event is marked as a centennial-scale negative excursion in El Soplao δ18O, starting at 8.19 ± 0.06 ka and lasting until 8.05 ± 0.05 ka, suggesting increased recharge at the time. Although this is supported by the other proxies, the amplitude of the changes is minor and largely within the realm of variability over the preceding 1000 years. Further, the shift to lower δ18O leads the other proxies, which we interpret as the imprint of the change in the isotopic composition of the moisture source, associated with the meltwater flux to the North Atlantic. A comparison with other well-dated records from south-western Europe reveals that the timing of the 8.2 ka event was synchronous, with an error-weighted mean age for the onset of 8.23 ± 0.03 and 8.10 ± 0.05 ka for the end of the event. This compares favourably with the North Greenland Ice Core Project (NGRIP) record. The comparison also reveals that the El Soplao δ18O is structurally similar to the other archives in south-western Europe and the NGRIP ice-core record.
... Different types of bounding surfaces in speleothems have been described and their mode of formation and significance in terms of changes in environmental conditions have been discussed by several authors (Luetscher et al., 2011;Railsback et al., 2011Railsback et al., , 2013Perrin et al., 2014;Martín-Chivelet et al., 2017). Detailed analysis of the discontinuities recognized petrographically in MOU 4 reveals that a combination of these different types also occurs, suggesting that bounding surfaces may better be considered as a group of particular events occurring at a given time during speleothem growth and as such are difficult to be categorized in pre-defined types. ...
... The bounding surface S2 is materialized by a growth interruption and microdissolution of the underlying calcite crystals. This corresponds to a type E surface (Railsback et al., 2011) indicating that drip water was undersaturated relatively to calcite, due to an increase of precipitation and a rapid path of feeding water which limited CO 2 degassing. Such interpretation is further corroborated by the fact that just above S2, a continuous light brownish layer testifies to an OM infiltration event resulting from intensified discharge. ...
... The middle Holocene record in stalagmites from NW Spain shows that the humid climate continued, but was alternating with episodes of non-carbonate precipitation or very slow drip rate in Atapuerca speleothems (Martínez-Pillado et al., 2014). Similarly, stalagmite record from Cova da Arcoia (NW Spain) suggest a period of warmer and drier conditions between 8.0 and 6.5 kyrs, evidenced by type L surfaces indicating episodes of drier conditions on the order of decades to roughly two hundred years (Railsback et al., 2011). The MOU 4 record shows that the climate was still humid enough to allow slightly higher drip rates than for the preceding interval and abrupt infiltration events evidenced by the minor discontinuity S6-7a. ...
A stalagmite from Moulis Cave in the northern Pyrenean piedmont in SW France provides a discontinuous record between the last interglacial and the Holocene. Petrography, microstratigraphy and internal architecture of the stalagmite combined together, document paleohydrological history of the drip site during speleothem growth, including infiltration conditions and calcite saturation state of water feeding the stalagmite. Following diagenetic screening which demonstrates the excellent state of preservation of the speleothem, a set of petrographical, mineralogical and geochemical analytical techniques was used to characterize: 1. the successive growth units and their bounding surfaces, including facies and nature of processes occurring at level of each discontinuity, and 2. the morphological changes of the stalagmite apex and stacking pattern.
Results reveal that each bounding surface results from a particular group of events, the nature and effects of which are petrographically clearly identifiable. During the interstadials 5b-5a of the last interglacial, the stalagmite developed at a relatively moderate growth rate and under stable drip rate conditions, except at the onset of the 5b cooling. Highest growth rates are recorded during the Bølling-Allerød to Younger Dryas, and the Early-Middle Holocene. During the Younger Dryas, cold and humid climate is suggested on the northern piedmont of the Pyrenean range. Temperate and humid conditions prevailed during the Early Holocene. Middle Holocene was still humid North of the Pyrenees, except during the cold and dry event at ~6.2 kyrs. During the last growth phase of the stalagmite, growth rate slowed down drastically in relation to increasing frequence of high infiltration events, possible floodings and a decreasing saturation of drip water relatively to calcite.
... In other Spanish caves, aragonite formation was identified, such as Cova da Arcoia (Galicia Province, Railsback et al., 2011), at El Soplao and Torca Ancha Caves Cantabria, (G azquez et al., 2012;Rossi and Lozano, 2016), at Cueva Mayor, Atapuerca (Martínez-Pillado et al., 2010), at Valporquero cave (Dur an Valsero et al., 2000) …. Until now, however, no specific study has been conducted on possible diagenetic alteration. ...
Two stalagmites from Nerja cave (Andalusia, Spain) were studied. The cave is well known because of its long human occupation from the Upper Palaeolithic to the Chalcolithic and its abundant parietal prehistoric Art. The aims of this study were twofold: i) to compare uranium/thorium (²³⁰Th/²³⁴U) and Carbon-14 (¹⁴C) ages obtained all along the growth axis of the stalagmites in order to understand the consequences of diagenetic processes on the validity of radiometric ages; ii) as one of the stalagmites contains black layers, attributed to combustion soot, to establish when these intense hearths were used and by which culture.
²³⁰Th/²³⁴U and ¹⁴C ages were coupled with mineralogical studies using FTIR (Fourier-transform infrared spectroscopy) and thin section observations. The first stalagmite (GN16-9b) displays ²³⁰Th/²³⁴U ages in stratigraphic order, and compatible with ¹⁴C ages corrected for a few percent of dead carbon. Homogeneous composition of aragonitic crystals characterized by their needle-like texture is observed throughout this speleothem. For the second stalagmite (GN16-7), in contrast, ²³⁰Th/²³⁴U ages display large significant inversions and discordant results on the upper part and at the base of the stalagmite, suggesting a possible open system behavior for this chronometer. Interestingly, ¹⁴C ages are in stratigraphic order all along the stalagmite and are compatible with ²³⁰Th/²³⁴U ages only in its central part. Mineralogical studies display evidence of aragonite to calcite transformation at the top and a complex mineralogical assemblage with interlayered silicates (possibly clays) and calcitic mineralogy for the base of GN16-7. In these parts, discordant ²³⁰Th/²³⁴U ages were measured. In the middle part of the stalagmite, however, where the fibrous aragonite is well preserved, the ¹⁴C and ²³⁰Th/²³⁴U ages agree. Our data suggest that in the case of aragonite to calcite transformation as shown here, ²³⁰Th/²³⁴U ages are biased, but ¹⁴C ages seem to remain accurate, as already observed in aragonitic marine bio minerals. ¹⁴C ages obtained are used for the chronology of the soot layer, determined here between 7900 and 5500 years Cal BP, coherent with previous analysis of charcoals in the same sector of the cave. This study highlights the importance of working with at least two chronometers when stratigraphic age verification is not possible, as is the case of some parietal CaCO3 thin layers used for rock art dating. Recent ²³⁰Th/²³⁴U ages published for carbonate deposits on Spanish parietal Art are discussed in light of this demonstration.
... Isotopic signals can tell the degree of wetness or dryness; but for the same isotopic signal, there can be a variety of petrographic textures giving additional information, for example, the degree of degassing or evaporation, fluid super saturation, kinetics of growth processes, discharge, presence of growth inhibitors in the solution, the mechanisms of transport of ions from the solution to the crystal surface and so on (Frisia, Borsato, Fairchild, & Frank McDermott, 2000). Despite such importance of petrographic work, to date, few attempts have been made in this direction to understand the origin and evolution of different microfabrics in speleothems with the changing climate conditions (Ayalon, Bar-Matthews, & Kaufman, 1999;Fairchild, Frisia, Borsato, & Tooth, 2006;Frisia, 1996Frisia, , 2014Frisia et al., 2000;Railsback et al., 2011). Therefore, the present study is an attempt for coupling the petrological microfabrics with stable isotopes proxy in speleothems to reconstruct the palaeo-precipitation variability in Uttarakhand, northwest Himalaya. ...
Speleothems are widely used terrestrial archives for the reconstruction of regional paleoclimatic conditions using mainly stable oxygen isotopes. However, the isotopic signals are quite vulnerable to post‐depositional recrystallization, and in the absence of detailed petrographic characterization, the validity of the isotopic dataset remains elusive. The present study is an attempt to bridge the gap between speleothem physical and geochemical proxies, their interrelationship and applicability, to reconstruct the regional climatic conditions in the northwestern Himalayas. We have identified different zones of depleted/enriched oxygen isotopes linked with the enhanced/decreased regional rainfall with strong/weak Indian summer monsoon. Prograding growth laminae and distinct columnar crystalline texture in calcite are associated with depleted oxygen isotopes. This suggests ample water availability and a higher drip rate in the cave, and further approves the wetter regional climate. Whereas, retractional growth laminae with dark micrite and microspar point towards slower drip rate and high evaporation associated with decreased rainfall. The presence of microspar in the studied stalagmite may indicate possible diagenetic alteration. However, oxygen isotopes data is unable to detect these small‐scale changes. Nevertheless, a coherency exists between isotopes and petrographic proxies for regional climate variability on a larger scale, and diagenesis in the studied sample possibly occurred during the early stage of precipitation. Therefore, isotopic studies coupled with detailed petrography can better ascribe paleoclimate conditions, and minimize the chances of erroneous interpretation because of diagenetic alterations of carbonate.
... Courel Mountains UGGp shows singular fluvial and slope landforms and deposits, as well as local karst, glacial and periglacial features (Fig. 5a) landslides. Speleological teams documented 25 main karst caves 7 km in length, hosting stalagmite palaeoclimate records up to 550 ka (Railsback et al. 2011(Railsback et al. , 2017. Courel Mountains commonly exhibit stratified talus deposits and other periglacial features, some of them formed before 44 ka (Pérez-Alberti and Cunha 2016; Viana-Soto and Pérez-Alberti 2019). ...
The management of a UNESCO Global Geopark (UGGp) requires a vast wealth of miscellaneous scientific knowledge that
can be successfully organised using a Geographical Information System (GIS). This paper presents a pragmatic GIS database
to assist in the suitable governance of the Courel Mountains UGGp (2017) in Northwest Spain. The database is structured in
66 coverages compiled from public sources and previous works or produced through traditional mapping (combining fieldwork
and photointerpretation) and GIS tools. The acquired data was later homogenised and validated by a multidisciplinary
team and archived in independent coverages. Forty thematic maps illustrate the broad range of cartographic information
included in the GIS database. Among them, 25 basic maps provide an overview of the UGGp and 15 new maps focus on
crosscutting and technical issues. All maps illustrate the huge potential of GIS to create new resources combining coverages
and adapting the legend according to their purpose and audience. The database facilitates the suitable publishing of consistent
outputs (e.g., brochures, books, panels, webpages, web serves), as well as the elaboration of technical data to assist the
park management. The database furnishes information on the design of education actions, touristic routes, activities and
Geopark facilities. The GIS database is also a supportive tool for scientific research and provides the necessary knowledge
to conduct geoconservation actions based on land use, geological hazards and the occurrence of natural and cultural heritages.
Altogether, the GIS database constitutes a powerful instrument for policy-making, facilitating the identification and
evaluation of alternative strategy plans.
... Notably, the values of lithogenic elements (Ti, K, Ca, Co, Rb, Zr) present within the core decrease until ~5.3 ka cal BP (Fig. 3), indicating drier conditions (Kylander et al., 2011). Special arid conditions in the NW Iberian Peninsula 5126 years ago (U/ Th age series) (Cova Arcoia, Fig. 7a) are inferred from the ESP05 stalagmite (Railsback et al., 2011). Based on speleothem data (El Refugio cave, Fig. 7a), the Mid-Holocene aridity preceded the onset of the Mediterranean climate at 5.3 ka BP in southern Iberia (Walczak et al. 2015). ...
The Iberian Central System (ICS) is a clue region to reveal Mediterranean/Atlantic inferences over Iberia. We present a multidisciplinary study from western Spain conducted in the Navamuño depression (ND), covering the last 16.8 ka (cal BP). A reconstruction of the palaeotemperature from the resulting geochemical data highlights four cold and dry intervals, namely, the Oldest Dryas, Older Dryas, Intra-Allerød Cold Period (IACP), and the Younger Dryas, along with warmer intervals: the Bølling (14.7-14 ka) and the Allerød (12.9-12.6 ka); however, the Greenland Interstadial GI-1c (13.4-13.1 ka) is barely distinguishable in the ND. Despite the shortage of biomass to sustain fire, the earliest charcoals are from ~14.4-13.8 ka. Evidence of ash/dust events overprinting the geochemical background starts at ~13.8-12.8 ka. Significant fire activity in the Early Holocene at ~11.7-10.6 ka affected the ND, matching the westernmost ICS data. This period includes short oceanic spells inferred from Cl peaks at ~10.9-10.2 ka and three cold intervals at 11.4, 9.3, and 8.2 ka disrupted the progressive temperature increase. The Mid-Holocene showed a continuously increasing trend towards an arid climate, peaking at 4.2 ka under a pervasive dust influx from North Africa, which has prevailed since almost ~7.9 ka. A prominent volcanic event at ~6.8-5.8 ka is in Navamuño and Roñanzas (Asturias, N Spain; Gallego et al., 2013) identified from heavy metal-rich layer, synchronous with the last known eruption of the Calatrava volcanic field (South-Central Spain; Poblete-Piedrabuena et al., 2019). This volcanic eruption could affect many other regions half north of Iberia. The pervasive presence of oceanic aerosols in the last three millennia (2.8 ka ~) allowed the formation of a Cl-rich peat layer during the Ibero-Roman humid period ~2.1 ka, before a changing around ~0.4 ka toward colder and drier conditions at the Little Ice Age (LIA) period.
