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The Arctic Ocean is rapidly warming. In this paper, we document changes in the source, distribution, and accumulation rate of organic matter (OM) for three sediment cores in the Bering and Chukchi seas to investigate changes to the oceanic carbon cycle over the past ∼75 years. Analyses were undertaken using bulk properties, such as total organic carbon (OC), total nitrogen (TN), stable carbon isotope (δ13C), OC to TN molar ratio (C/N), and biomarkers (lignin phenols). The OC, TN, and lignin (Σ8, in mg (g sediment)−1) contents were found to be significantly related to the fraction of sand (Sand%) as a result of sediment sorting and/or different sediment sources. Using an end-member mixing model, we estimated marine OM accounted for ∼67% of all organic matter in all cores, being the dominant source. Moreover, terrestrial OM mainly originated from angiosperm non-woody tissue, while moss contribution was negligible. In the Bering Sea shelf, OC% has not changed over time, but there have been some extreme peaks around the 1960s–1970s and in 2005, which correspond to increased terrestrial input from North American rivers. In the southern core from the Chukchi Sea, the OC% showed an apparent decrease after 2000, accompanied by an increase in sand content, likely due to enhanced delivery of volcanic rocks by the Pacific Inflow from the Bering Sea. In contrast, in the northern core from the Chukchi Sea, the OC% showed a significant increasing trend, with some peaks occurring at the same time as in the Bering Sea core. The mean increase rate was compared to the increase in Siberian riverine discharge, which both could be caused by long-term climate changes. The results highlight the regional differences in the response of OC preservation to climate change and other controlling factors. Further studies with higher spatial resolution are required to better understand the preservation of OC in response to climate change. [Display omitted] • The main vegetation source was vascular plant, contribution from moss was limited. • Marine source accounted for ∼67% of the sedimentary OC in the (sub)Arctic cores. • OC preservation changed differently in the (sub)Arctic Ocean in past decades. [ABSTRACT FROM AUTHOR]

The Cretaceous period is a typical representative of a 'greenhouse climate' in geological periods, and is also an important period for the formation of hydrocarbon source rocks, which has become a hot spot in the study of palaeoclimate and organic matter enrichment. In order to further explore the mechanism of action between paleoclimate and organic matter enrichment, the response mechanism of organic matter enrichment to palaeotemperature and palaeorainfall is finely characterised by synthesising the analysis of sporopollen, biomarkers and n-alkane carbon isotopes in this study. The sporopollen indicates that the palaeoclimate is generally temperate, semiarid to semihumid, and the n-alkane and n-alkane carbon isotopes indicate that the palaeoclimate and palaeorainfall have obvious fluctuations and synchronous characteristics of rainfall and heat. Based on the differences in palaeotemperature and palaeorainfall, the palaeoclimate can be further divided into three stages: cool-temperate and semiarid, warm and semihumid, and cool-temperate and semiarid. The trend of palaeoatmospheric pCO 2 recovered from the carbon isotopes of normal alkanes C 27 , C 29 , and C 31 is roughly the same as that of palaeotemperature, indicating that pCO 2 is important in regulating palaeotemperature. According to the distribution pattern of organic carbon, different layers are divided into three sedimentary Units: I, II and III. Different sedimentary Units have good corresponding relationships with different palaeoclimatic stages. Under the cool-temperate and semiarid climate, lower palaeotemperature and higher palaeosalinity are not conducive to the prosperity of lake organisms. The formation of light grey mudstone, silty mudstone and carbonate has lower TOC, and the organic matter types are mostly II 1 and II. Under a warm and semihumid climate, higher palaeotemperature and moderate palaeorainfall are conducive to the prosperity of lake organisms. The formation of oil shale and shale has higher TOC, and the organic matter types are mostly I and II 1. However, excessive palaeorainfall brings much terrigenous debris, leading to the organic matter dilution. Therefore, palaeoclimate and palaeorainfall not only affect the abundance of organic matter, but also affect the types of organic matter. In the paper, the mechanism of organic matter enrichment is improved by delicately characterising the palaeotemperature and palaeorainfall. • Reconstruction of the early Cretaceous paleoclimate using n-alkanes and sporopollen in terrestrial sediments. • High precision recovery of atmospheric pCO 2 in the Early Cretaceous using carbon isotopic of n-alkanes. • Revealed the impact of paleoclimate on organic matter enrichment. [ABSTRACT FROM AUTHOR]

Climate modelling and palaeotemperature reconstructions derived from several proxies (TEX 86 , δ18O) suggest that the Late Cretaceous was one of the warmest intervals in Earth history. The greenhouse climate reached its acme near the Cenomanian-Turonian boundary (CTB) interval with sea surface temperatures over 35 °C in low and mid- palaeolatitudes, coinciding with the highest sea level stands of the Phanerozoic. Following this warming phase, a general cooling trend punctuated by short-term hot snaps characterized the rest of the Cretaceous. Palaeotemperature and palaeoenvironmental changes are well documented in deep-water carbonate deposits based on variations in geochemical proxies and distribution patterns of macro- and microfauna. However, such climatic and environmental fluctuations severely impacted carbonate platforms, sedimentary environments that are particularly sensitive to external perturbations. Palaeontological data show major changes within the main carbonate platform producers (rudists and benthic foraminifera) during the early Late Cretaceous. Both groups experienced major taxonomic turnovers at the CTB, followed by a further re-radiation in the middle/late Turonian. The lack of detailed palaeoclimatic reconstructions in shallow water carbonate succession hampers the possibility to investigate a possible causal relationship between temperature changes and faunal evolution. In this paper, we report integrated geochemical, sedimentological, and palaeontological data from the Adriatic Carbonate Platform (Friuli, north-east Italy). Benthic foraminifera biostratigraphy and isotope stratigraphy (δ13C and 87Sr/86Sr) were used to precisely constrain the stratigraphy of the late Cenomanian-middle Turonian interval. δ18O analysis on both well-preserved rudist shells and bulk rock samples enabled the construction of high-resolution palaeotemperature curves. The resulting temperature trends are comparable with those from the deep-water record across the late Cenomanian-Turonian interval. The warmest phase was in the Early Turonian with sea surface palaeotemperatures as high as 41–45 °C recorded in rudist shells. Data show temperature fluctuation from the late Cenomanian to the Early Turonian with a magnitude >7 °C. Benthic foraminifera and rudist evolution responded to these palaeotemperature fluctuations, and their decline in the late Cenomanian and full recovery in the Turonian suggest a strong link with temperature changes. • Reconstructed temperatures from carbonate platforms during the Cenomanian -Turonian interval are missing • High resolution paleotemperatures reconstruction and biota evolution (rudists and benthic foraminifera) from Friuli Carbonate Platform is presented • Paleotemperatures estimated using δ18O analyses on bulk rock and well preserved bivalve samples (rudists and Chondrodonta) • δ18O analyses in bivalve shells suggest warmest Temperatures °>40°C in the Early Turonian • Rudists and benthic foraminifera distribution/abundance strongly modulated by temperature changes [ABSTRACT FROM AUTHOR]

Abstract Floral communities in terrestrial habitats such as steppes are highly sensitive to regional climate changes. Here, we generated carbon and nitrogen isotope profiles for soil organic matter (SOM) in the Weinan loess-paleosol section in order to investigate changes in floral communities on the Chinese Loess Plateau (CLP) and their relationship to climate variation since 75 ka. δ13C SOM at Weinan ranges from −23.6 to −18.0‰ and δ15N SOM ranges from +3.4 to +5.5‰. Modeling based on the δ13C SOM record suggests that the proportion of C4 plants (%C4) has varied from lower during cold intervals (with minima of 24–32% at 73.1 ka, 20.9 ka (LGM), and 0.6 ka) to higher during warm intervals (with maxima of 62–64% at 53.0 ka and 8.2 ka). The δ13C SOM and δ15N SOM profiles are strongly correlated (r = +0.82; p(α) <0.001), suggesting that the N-isotope composition of SOM was also largely controlled by inputs of C4 versus C3 plants, consistent with known patterns of N-isotope variation among modern plants. The %C4 profile exhibits significant covariation with reconstructed mean annual temperatures (MAT) (r = +0.42; p(α) <0.001), mean annual precipitation (MAP) (r = +0.42; p(α) <0.001), and summer monsoon intensity (r = +0.50; p(α) <0.001), suggesting that paleovegetation was controlled by each of these climate variables to a degree. Comparing the Weinan record to SOM profiles across the CLP region, we identified three zones of varying monsoonal influence, with the East Asian Summer Monsoon (EASM) exerting the strongest influence on the southeastern margin of the CLP, and the East Asian Winter Monsoon (EAWM) greater influence on its northwestern margin. This paper provides new insights into deciphering paleovegetation patterns and their links to paleoclimate change on the basis of paired C- and N-isotope records. Highlights • Analysis of δ13C and δ15N of soil organics in Weinan section, Chinese Loess Plateau • δ13C SOM and δ15N SOM profiles exhibit strong correspondence since 75 ka • Both C- and N-isotope compositions controlled mainly by inputs of C3 vs C4 plants • Paleovegetation type strongly influenced by summer monsoon intensity [ABSTRACT FROM AUTHOR]

During the Albian and Cenomanian, the Earth underwent profound climatic and oceanographic changes that were recorded in sedimentary successions on a global scale. Carbon isotope records spanning this time interval have been established in the western Tethys, eastern Pacific and North Atlantic Oceans, but not yet in the eastern Tethys Ocean. In this paper, we present biostratigraphic, chemostratigraphic and cyclostratigraphic characteristics of the uppermost Albian–lowermost Cenomanian in an eastern Tethyan section (Youxia, southern Tibet). Based on calcareous nannofossil biozones and the bulk rock δ 13 C curve, the Albian-Cenomanian boundary interval (ACBI) was identified and correlated to the western Tethys and Atlantic Oceans. In the Youxia section, δ 13 C values range from approximately 0‰ to +1.3‰ (−0.03‰ to +1.31‰). Four subevents (a, b, c and d) were distinguished in the ACBI carbon isotope curve via correlation with other sections. Based on a spectral analysis of the carbonate content, we recognized Milankovitch short eccentricity (~100 kyr) and precession (22.2 kyr) cycles, suggesting that orbital variations modulated depositional processes. The duration of the ACBI was estimated at ~311 kyr, while OAE 1d lasted for ~233 kyr in the eastern Tethys Ocean, consistent with the duration calculated from Atlantic Ocean records. [ABSTRACT FROM AUTHOR]

The early Aptian oceanic anoxic event (OAE 1a) is well known in the western Tethys, the North Atlantic and the Pacific Ocean, but has not been reported in the eastern Tethys to date. In this paper, we present bulk organic carbon isotope data and ammonite biostratigraphy of a lower Aptian succession from the Gucuo area (southern Tibet). These findings document the occurrence of the OAE 1a for the first time from the eastern Tethys. The studied sequence can be attributed to the D. forbesi and D. deshayesi ammonite zones of the lower Aptian. The δ 13 C org data can be correlated with published early Aptian carbon isotope records from the western Tethys and the Pacific. A distinctive negative carbon isotope excursion of 2.4‰ in the upper part of the section corresponds to segment C3 of the OAE 1a, and the following positive excursion correlates to segment C4. The absolute values of the carbon isotope ratio in the Gucuo area are higher than those of known sections in the western Tethys and equatorial Pacific. We suggest that diagenetic alteration is the major cause of the higher absolute values in the Gucuo area. [ABSTRACT FROM AUTHOR]

The Early Bajocian witnessed a global environmental perturbation, characterized by faunal and floral turnovers and a positive carbon isotope excursion. In Italy, this environmental perturbation coincided with an eutrophication event and a carbonate crisis, but this has so far not been adequately reported from other settings, leaving doubt about the extent and nature of these phenomena. In this paper, we are reporting on an extensive neritic carbonate factory demise that occurs in the upper Lower Bajocian of Morocco, more precisely in the upper Propinquans – lower Humphriesianum Zones. This demise coincided with the acme of the global carbon isotope perturbation, recorded by a 3‰ positive carbon isotope excursion in the bulk organic matter of Morocco, but not in the micritic phase, due to the fact that the Moroccan carbonate δ 13 C record is more sensitive to local rather than global influences. Furthermore, we observe that the Lower Bajocian of Morocco is relatively enriched in arenitic siliciclastic deposits, suggesting increased weathering and nutrient levels along the northwestern margin of Africa during the Early Bajocian. However, comparison with neighboring European basins highlights the non-uniqueness and different timing of the response of shallow-water carbonates to the Early Bajocian environmental perturbations, as some regions present no sign of carbonate factory crisis. Hence, we postulate that local factors were important in mediating the response of neritic carbonate factories to this global environmental perturbation. We notably highlight the role of large Early Bajocian sea-level fluctuation as a trigger for carbonate factory change and demise in Morocco. [ABSTRACT FROM AUTHOR]

Abstract: In their recent paper, ; Anti-phase oscillation of Asian monsoons during the Younger Dryas period: Evidence from peat cellulose δ13C of Hani, Northeast China, Palaeogeography, Palaeoclimatology, Palaeoecology 297, 214–222) discuss bulk peat sample cellulose δ13C data from a fen in northeast China as a proxy for East Asian summer monsoon intensity during the Late Glacial period. Based on their own results, cited papers, and an extensive re-interpretation of sedimentological and palynological data from nearby Lake Sihailongwan, construct a hypothesis of contrasting moisture conditions in northern and southern China, with wet conditions in the north during the Younger Dryas period and an anti-phase behaviour of Indian- and East Asian summer monsoon intensity. However, we do not approve of the re-interpretation of our Lake Sihailongwan data by and must strongly reject it. We show here that neither the fen data, nor the Lake Sihailongwan data or any other cited data allow for the sound assumption of an intensified East Asian summer monsoon in northeastern China during the Younger Dryas. The Late Glacial variability of the fen data found by can be easily explained by changes in the plant assemblage down core and thus by the composition of the peat. Furthermore, the use of bulk peat cellulose δ13C data as a precipitation proxy remains unproven for that area. Hence, there is no basis for a model contrasting Indian and East Asian summer monsoons during that period. [Copyright &y& Elsevier]

The South Qinling Belt is a key area for understanding the collisional history of the South China and North China blocks during the Lopingian (late Permian) and Triassic. This paper establishes the first integrated timescale based on conodont biostratigraphy and δ13C carb records from a continuous end Permian to the end-Early Triassic succession at Yiwagou, South Qinling Platform (SQP). Ten Early Triassic conodont zones are established. They are, in ascending order, Hindeodus parvus , H. postparvus , Neospathodus dieneri , Eurygnathodus costatus and E. hamadai , Novispathodus waageni - Scythogondolella mosheri , Pachycladina - Parachirognathus assemblage, Triassospathodus hungaricus , Ns. robustispinus and T. clinatus zones. Our record of δ13C carb fluctuations shows close correspondence to known Early Triassic carbon isotope fluctuations and, in combination with the conodont data, helps achieve a high-resolution age model for the region. The use of E. costatus as a good auxiliary marker for the Induan-Olenekian boundary (IOB), within palaeolatitudes of 40°N-40°S, is supported but it can not replace the use of Nv. waageni , because the former is absent in higher-latitude and cooler regions. The conodont faunas from the Palaeo-Tethyan Yiwagou section closely resemble those from the Northern Yangtze Platform (NYP), but they differ somewhat from the contemporaneous Nanpanjiang Basin at species level. Thus, the Qinling Sea was likely well connected with the NYP in the Early Triassic, but was more isolated from the Nanpanjiang Basin. The remarkable reappearance of Hindeodus fauna around the IOB at Yiwagou implies that the shallow-water Qinling Sea was a refuge area for this genus long after its disappearance elsewhere. • Conodont biostratigraphy and δ13C carb records from end Permian to the end-Early Triassic succession at Yiwagou, South Qinling Platform. • Discussion of index conodont for the Induan-Olenekian boundary. • Comparison of the conodont faunas between the eastern Paleo-Tethyan Yiwagou, South China and the western Paleo-Tethyan Europe. • The shallow-water Qinling Sea was a refuge area for Hindeodus fauna after Griesbachian. [ABSTRACT FROM AUTHOR]

The carbon and oxygen isotope composition of well-preserved belemnite rostra and bulk carbonates from uppermost Aalenian to Lower Tithonian outcrops of the Pieniny Klippen Belt in the Carpathians is under discussion in this paper. New isotope and elemental data from the open marine basin in a rarely studied, northern part of the Tethys Ocean, corroborate the world-wide δ 13 C variations and global temperature changes of a seawater. The δ 13 C temporal trends display prominent positive shift in the Upper Callovian–Middle Oxfordian, as well as a declining trend in the Kimmeridgian–Tithonian interval. δ 18 O values of belemnite rostra suggest a decrease in temperatures during the latest Aalenian–Early Bajocian. The Upper Jurassic temperatures, estimated on the basis of oxygen isotope values and Mg/Ca ratios of belemnite rostra, indicate a warming of the seawater of ca. 5.5 °C in the Late Oxfordian–Early Kimmeridgian. This temperature rise is interpreted to be a result of the global climate warming present during the early Late Jurassic. [ABSTRACT FROM AUTHOR]

The paper describes Late Jurassic–Early Cretaceous seep carbonate boulders from the Russian Arctic island of Novaya Zemlya, collected in 1875 by A.E. Nordenskiöld during his expedition to Siberia. The carbonates are significantly depleted in heavy carbon isotopes (δ 13 C values as low as ca. − 40‰) and show textures typical for carbonates formed under the influence of hydrocarbons, such as fibrous carbonate cements and corrosion cavities. The rocks contain index fossils of Late Oxfordian–Early Kimmeridgian, Late Tithonian (Jurassic) and latest Berriasian–Early Valanginian (Cretaceous) age. The fossil fauna is species rich and dominated by molluscs, with subordinate brachiopods, echinoderms, foraminifera, serpulids and ostracods. Most of the species, including two chemosymbiotic bivalve species, likely belong to the ‘background’ fauna. Only a species of a hokkaidoconchid gastropod, and a possible abyssochrysoid gastropod, can be interpreted as restricted to the seep environment. Other seep faunas with similar taxonomic structure are suggestive of rather shallow water settings, but in case of Novaya Zemlya seep faunas such structure might result also from high northern latitude. [ABSTRACT FROM AUTHOR]

In this paper, we present organic carbon isotope records from continental sediments spanning the late Paleocene-middle Miocene (57.9–15.0 Ma) in the Lanzhou Basin, northeastern Tibetan Plateau to investigate terrestrial ecosystem-response to global climate change. The continuous sediment δ13C TOC values that we obtained range from −27.83‰ to −20.05‰. Combining these data with the sediment C/N ratios and n-alkane distribution, we infer that the major source of sediment organic matter was terrestrial C 3 plants. Furthermore, we note that both sediment δ13C TOC and δ13C n-alkanes values gradually become more positive from 57.9 to 26 Ma and then become relatively more negative from 26 to 15 Ma. These δ13C values vary closely with global temperature changes. We propose that global temperature controlled δ13C values with cooler conditions resulting in less rainfall in inland Asia, and vice versa. Therefore, mainly driven by the global temperature, the regional climate in the Lanzhou Basin gradually changed from warm-wet to cold-dry conditions during 57.9–26 Ma, and the climatic conditions became warmer and wetter again after 26 Ma. This long-sequence terrestrial ecologic environment study obtained from the northeast Tibetan Plateau powerfully demonstrates the first-order role of global climate in regulating the long-term evolution of regional environment. • We obtained continuous organic carbon isotope records on the NE Tibetan Plateau at 57.9–15 Ma. • δ13C TOC and δ13C n-alkanes values vary negatively with global temperature. • Rainfall dominated by global temperature affects plant δ13C change within terrestrial ecosystem. [ABSTRACT FROM AUTHOR]

The present paper documents and discusses a new Albian–early Cenomanian carbon isotope (δ 13 C carb and δ 13 C org ) curve from the subequatorial Eastern Pacific in Peru. Chemostratigraphic evidences for the expression of the OAE1b set and for OAE1c and OAE1d are presented. This dataset is relevant inasmuch as previous work is strongly biased towards study sites in North America (Western Interior Basin), in Europe (Tethys) and the Pacific realm. A comparison of the carbon isotope stratigraphy obtained in Peru with published sections from the Central and Western Pacific, the Western Atlantic and Northern and Western Tethys reveals an overall good agreement supporting the global nature of the isotope patterns described here. The δ 13 C from Peru record is constrained by biostratigraphic evidence and 87 Sr/ 86 Sr isotope stratigraphy using well-preserved oyster shells. Furthermore, we document the development of a heterozoan epeiric–neritic mixed carbonate–siliciclastic ramp in the Western Platform of Peru and its corresponding sedimentary facies associations. This dataset was used to elucidate the complex interplay of climatic changes, nutrient supply, and platform drowning, leading to the following conclusions: (i) an upper Aptian–lower Albian major change from siliciclastic-dominated to carbonate sedimentation coincided with the impact of the Kilian Level, (ii) a lower Albian incipient platform drowning linked to the impact of the Paquier Level, (iii) A lower middle Albian major demise of neritic carbonate production that coincides with the Leenhardt Level, followed by middle Albian condensed sedimentation that reports prominent negative values in δ 13 C carb prior to the onset of OAE1c and (iv) finally, renewed carbonate ramp production during the upper Albian–lower Cenomanian. The data shown here represent the foundation for future work documenting the mid-Cretaceous of Peru and its implications for the palaeoceanography of the SE subequatorial Pacific. [ABSTRACT FROM AUTHOR]

This paper presents and discusses vegetation changes between ca. 14,910 and 11,620 cal. BP, which are recorded in the deposits of a small mire located in south-eastern Poland. Particular attention is paid to arboreal taxa. Changes in arboreal vegetation are reconstructed on the basis of pollen analysis, including pollen accumulation rate (PAR), and analysis of plant macrofossils, these being supported by radiocarbon chronology. Before the onset of the GI-1 warming (14,910 ± 310–14,810 ± 280 cal. BP) a mosaic of Pinus and Betula wood patches and/or isolated stands of trees, along with heliophilous Juniperus thickets were dispersed within patches of herb steppe and tundra communities. Thermal amelioration at the GS-2–GI-1 transition (ca. 14,810 ± 280–14,510 ± 200 cal. BP) led to the spread of Salix and to a lesser extent of tree birches ( Betula ), pines ( Pinus ) and Hippophaë rhamnoides . In the light of PAR values, from ca. 14,550 ± 210 cal. BP there were open pine–birch woodlands there, which ca. 14,270 ± 160 cal. BP turned into dense forests. Cold-oscillations such as GI-1d, GI-1c2 and GI-1b, dated in the profile at ca. 14,190 ± 120–13,870 ± 140, 13,740 ± 120–13,490 ± 80 and 13,120–12,870 ± 60 cal. BP respectively, are visible as declines in the PAR of arboreal taxa. From ca. 13,770 ± 120 cal. BP Picea abies , whose nearest glacial refugia were located in the Western Carpathians, probably reached the site surroundings (50°N). In the Younger Dryas (GS-1) climate deterioration caused a decline in birch population in the first phase, a slight retreat of forests and the simultaneous expansion of Artemisia –Poaceae steppe communities and Juniperus thickets. The PAR values reflect a division of the Younger Dryas into two distinct phases: an older phase, more severe for tree populations, probably due to longer and cooler winters, and a younger phase with milder winters which begun ca. 11,960 ± 110 cal. BP. [ABSTRACT FROM AUTHOR]

In the present paper we report the most complete fossil avifauna from the southern cone of South America. The specimens here described were collected in the Paso Otero locality, at the middle stream of the Quequén Grande River, Pampean Region (Buenos Aires Province, Argentina). The fossiliferous levels belong to the La Chumbiada Member of Luján Formation (37,800 ± 2300 yr BP, late Pleistocene). The assemblage is represented by 60 specimens belonging to at least 22 taxa. The radiocarbon age indicates that Paso Otero birds represent the oldest late Pleistocene avifauna known from the South American continent and the first coming from a clear interstadial event (MIS3). Available evidence indicates similar environmental conditions during the MIS3 interstadial in the Pampean Region of Argentina and the post-Last Glacial Maximum stadials in southeastern Brazil. The absence of significant extinction events in the latest Pleistocene–early Holocene avifaunas of Brazil and Argentina suggests that the main avifaunal composition along southeastern continental lowlands may not be affected by the cyclic retraction and extension of open environments. On the contrary, the fossil record of Peru and Ecuador demonstrates that a large number of taxa, including aquatic and predatory-scavenger birds, have gone extinct along Andean environments at the Pacific coast, and late Pleistocene climatic oscillations may have played a more dramatic impact in these avian communities. [ABSTRACT FROM AUTHOR]

Abstract: Whether there are terrestrial responses to the Oceanic Anoxic Events (OAEs) remain enigmatic. In this paper, we report a case study in the Lower Cretaceous continental and transitional sequences of coastal southeastern China. It may represent the first late Aptian to Albian terrestrial carbon isotope record from China. Several organic-rich black shale and grayish black mudstone horizons were found to develop widely in the coastal southeastern China during the period from 113±3Ma to 99±3Ma, when the Cretaceous OAEs were recorded primarily in marine sequences. Organic carbon isotope (δ13Corg), total organic carbon (TOC), and total nitrogen (TN) were analyzed for the black shales from two sections, i.e., the Shipu transitional and Chong'an continental sections. Five negative δ13Corg excursions can be recognized for both the sections, termed as SI–SV and CI–CV events for the Shipu (S) and Chong'an (C) sections, respectively. Correlations between δ13Corg, TOC and N/C ratio suggest that the SI–SIII and CI–CIII events might have been caused by global factors, i.e., the OAE1b event based on analogs to typical OAE1b reported in the Tethyan and Pacific basins. They archived the terrestrial carbon isotope response to the OAE1b accompanied with a disturbance of carbon isotope in carbon reservoir of the global ocean–atmosphere system under a warm and humid climate. [Copyright &y& Elsevier]

Abstract: The carbon, oxygen and strontium isotope geochemistry is the most widely applied chemostratigraphic tool in the reconstruction of paleoenvironments and indirect regional or global correlations for the Neoproterozoic times. Relatively good preserved carbonate rocks of the West Congo Supergroup, i.e. the Schisto-Calcaire Subgroup of the Democratic Republic of Congo and Gabon, and the Mbuji-Mayi Supergroup, i.e. the BII group from the Democratic Republic of Congo, make these Neoproterozoic successions unique for chemostratigraphical studies. In this paper, we propose to discuss on the fidelity of δ13Ccarb and Sr signatures in Neoproterozoic carbonates on the basis of a severe diagenetic control, using trace and major geochemistry, combined with C and O stable isotope analysis. Our result highlights that the δ13Ccarb fluctuations of the Schisto-Calcaire Subgroup reflect (i) facies variations, (ii) exchanges between isotopically light carbon in meteoric waters and carbonate during lithification and early diagenesis, and/or (iii) regional metamorphism grades rather than temporal signals of ocean chemistry, while in the unmetamorphosed carbonates of the Mbuji-Mayi Supergroup, reported to the Bitter Springs anomaly (~810Ma), the use of δ13C ratios are worldwide applicable for inter-basin correlations. [Copyright &y& Elsevier]

Abstract: Marine oxygen isotope records show that the Cenozoic global climate has undergone remarkable fundamental changes. However, how terrestrial ecosystems respond to these changes remains unclear. The Xining Basin on the northeastern Tibetan Plateau holds continuous fine fluvial-lacustrine sediments from the early Eocene to the early Miocene (between ~52Ma and 17Ma). This paper first presents total organic carbon isotope (δ13CTOC) and pollen records from the Xiejia section in the Xining Basin, as indicators of the long-term terrestrial paleoecosystem and paleoclimate changes in the Asian interior of NW China. The δ13CTOC record shows a long term persistently decreasing trend (from ~−20‰ to −23.5‰) superimposed with obvious cycles of five distinctive phases of heavier and lighter δ13CTOC values, along with short pulses of especially low values occurring at ~32.5Ma, 23Ma, 21.5Ma, and 18Ma. These variations generally correlate with changes of gymnosperm content or the ratio of gymnosperm to angiosperm (G/A); i.e., heavier δ13CTOC values correspond with higher gymnosperm content or higher G/A, as well as with global temperatures (for both long term trends and shorter term fluctuations). We propose that global temperatures might provide the major factor controlling the evolution of the gymnosperm content (and the G/A ratio) that determines the δ13CTOC in the sediments. The East Asian monsoon may not have reached this region during the deposition of the sediments, or alternatively, its signals could not clearly be identified in these low resolution paleoecologic records. [Copyright &y& Elsevier]

Abstract: The Jurassic–Cretaceous (J–K) boundary is one of the most problematic points on the geological timescale. The boundary is not defined by a Global Stratotype Section and Point (GSSP) because of the absence of well-defined (by significant faunal turnover), widely correlatable biostratigraphic levels to fix the base of the Berriasian. A distinct earliest Berriasian positive carbon isotope excursion is identified in the Boreal marine carbonate (belemnites) carbon records from the Maurynya River (Northern Urals) and the Nordvik Peninsula (northern East Siberia). The excursion is found within the top part of the upper Volgian Craspedites taimyrensis ammonite Zone, slightly above the J–K boundary, which was established by palaeomagnetic data. Because a significant positive δ13C shift was also observed immediately above the J–K boundary in the Tethyan Guppen-Heuberge pelagic-carbonate section (Switzerland), this positive carbon isotope event can be regarded as a useful marker for a Panboreal and Boreal–Tethyan correlation of J–K boundary beds. This δ13C excursion is interpreted as a record of increased rates of organic carbon burial. The δ13C data obtained previously for the upper Volgian and Ryazanian in different Boreal regions are also analysed in this paper. Other well-documented carbon isotope excursions with less global significance allow the creation of a composite carbon-isotope curve for Boreal regions that characterises the upper Volgian and Ryazanian in detail. [Copyright &y& Elsevier]

Abstract: High-resolution uranium analyses as well as oxygen, carbon and strontium isotopes data through Permian–Triassic Boundary (PTB) in the marine sections of three offshore wells in Persian Gulf are illustrated in this paper. A decreasing trend in U content from Upper Permian strata toward the PTB is recorded in all wells. Such a trend could not be adequately explained by the facies changes, diagenetic events, salinity variations, dolomitization or total organic carbon (TOC) content of the samples. Distinct and negative uranium anomalies coincide with the onset of the carbon isotope shifts, which might indicate influx of anoxic waters. The Th/U ratios below the PTB in the studied sections are mainly less than 2, reinforcing this possibility. Reducing conditions associated with the anoxia would have gradually increased the rate of U fixation on the deep-sea floor, resulting in low U concentration in the shallow water carbonates. A negative δ18O shift of about 4‰ could be seen at the PTB in all studied wells. Such excursion indicates a meteoric diagenesis below the boundary. Also, abnormally higher 87Sr/86Sr ratios below the PTB indicate significant input of radiogenic 87Sr during subaerial exposures at the end of Permian. This palaeoexposure surface is also reflected in depleted oxygen isotope values of this interval. Biostratigraphic studies also show that some important guide forms of Late Permian are absent in studied wells that could be due to several factors including non-sedimentation, subaerial exposure and erosion. Thus a near surface meteoric realm or emergent surface could be considered for the PTB in studied wells. [Copyright &y& Elsevier]

Abstract: The relationship between environmental conditions and the δ18O and δ13C values of soil and groundwater carbonates in Europe is poorly understood. Consequently, the use of the isotopic composition of these carbonate palaeoclimatic indicators in European sedimentary sequences is restricted. In this study we examine the δ18O and δ13C values of soil and groundwater carbonates from western and southern Europe. In western Europe there is no relationship between carbonate δ18O values and carbonate δ13C values. The δ18O values of soil carbonate appears to be driven by temperature, whilst the δ13C value of soil and groundwater carbonate reflects the persistent dominance of C3 vegetation in this region during the Quaternary. The δ18O and δ13C values of soil carbonates from Spain and Crete show a strong degree of co-variance suggesting that they are being controlled by the same environmental factor. This is suggested to be aridity. δ18O values are controlled by soil moisture evaporation whilst δ13C value is controlled by soil moisture degassing, vegetation abundance and possible C3/C4 vegetation inputs. The paper concludes by highlighting the fact that, although currently under-utilised, the δ18O and δ13C values of soil and groundwater carbonates have a huge potential for providing important palaeoenvironmental information from sites across Europe. [Copyright &y& Elsevier]

Abstract: Stratigraphic descriptions and radiocarbon data from eleven field locations are presented in this paper to establish a chronostratigraphic framework for offshore to nearshore deposits of Lake Bonneville. Based on key marker beds and geomorphic position, the deposits are interpreted to have accumulated during the period from the late transgressive phase, through the overflowing phase, into the regressive phase of the lake. Radiocarbon ages of sediments associated with the Provo shoreline indicate that Lake Bonneville dropped rapidly from the Provo shoreline at about 12,600 14C yr BP (15,000 cal yr B.P.). The presence of one or more sand beds in the upper part of the Provo-aged marl indicates rapid lowering of lake level or storm events at the end of the Provo episode. An accurate understanding of the timing and nature of Lake Bonneville''s climate-driven regression from the Provo shoreline is critical to correlations with records of regional and hemispheric climate change. The rapid descent of the lake from the Provo shoreline correlates with the decline of Lakes Lahontan and Estancia, and with the onset of the BØlling–AllerØd warming event. [Copyright &y& Elsevier]

Abstract: In their comment on our paper (Boulila S. et al. 2010 — Orbitally forced climate and sea-level changes in the Paleoceanic Tethyan domain, marl–limestone alternations, Lower Kimmeridgian, SE France, Palaeogeog. Palaeoclim. Palaeoecol., 292, 57–70), Mattioli and co-authors (E. Mattioli et al., Comment on "Orbitally forced climate and sea-level changes in the Paleoceanic Tethyan domain (marl–limestone alternations, Lower Kimmeridgian, SE France) " by S. Boulila, M. de Rafélis, L. A. Hinnov, S. Gardin, B. Galbrun, P.-Y. Collin [Palaeogeography Palaeoclimatology Palaeoecology 292 (2010) 57–70], Palaeogeography Palaeoclimatology Palaeoecology, this issue) criticize our depositional model of Lower Kimmeridgian marl-limestone alternations in the Vocontian Basin (SE France) and contest the nannofossil contribution to the build-up of micritic limestones. The model that we proposed links maxima of orbitally forced insolation with high sea-level, weaker continental erosion, and reduced detrital input, and insolation minima to low sea-level, increasing erosion of detrital materials and their transport to the basin. This involves a competition between multiple variable fluxes, and is supported by a multi-proxy study (magnetic susceptibility, weight percent carbonate, manganese content coupled with cathodoluminescence analysis, oxygen and carbon stable isotopes, and calcareous nannofossil analysis) on a 8.5-m thick interval from a ~40m-thick section at Châteauneuf-d''Oze (SE France). This differs substantially from previous models suggesting that detrital input to this part of the Vocontian Basin constitutes ‘background noise’, and that the main mechanism inducing the marl–limestone rhythms was orbitally forced carbonate mud export from the Jura Platform. [Copyright &y& Elsevier]

Abstract: Haslam and Petraglia raise three broad questions concerning our paper ‘Environmental impact of the 73ka Toba super-eruption in South Asia’, by Martin A. J. Williams, Stanley H. Ambrose, Sander van der Kaars, Carsten Ruehlemann, Umesh Chattopadhyaya, Jagannath Pal, Parth R. Chauhan [Palaeogeography, Palaeoclimatology, Palaeoecology 284 (2009) 295–314]. (a) What was the relationship between the ∼73ka Toba eruption and the cold stade between the Dansgaard–Oeschger interstades 20 and 19? (b) What was the regional impact of the eruption on vegetation? (c) What was the possible effect of the eruption upon humans and mammals? In response to questions (a) and (b) we note that the ∼73ka Toba eruption was followed by several centuries of intense cooling and wind-blown dust accession in the Greenland GISP2 ice core, by a change from forest to grassland or open woodland in central India (carbon isotopic analysis) and in the wider region (pollen analysis of a marine sediment core in the Bay of Bengal). In regard to (c), the genetic evidence is as yet too imprecisely dated to demonstrate causality as is the archaeological evidence cited by Haslam and Petraglia in favour of minimal impact. Future work supported by higher resolution chronologies than are presently available is needed to provide a less equivocal picture of the environmental impact of the ∼73ka Toba eruption. [ABSTRACT FROM AUTHOR]

Abstract: This paper documents the occurrence of the Little Ice Age (LIA) in the El Azufre and El Peñón glaciers at 35°S and in the Las Choicas and Las Damas glaciers at 34°55′S in the headwaters of the Rio Grande basin in the Central Andes of Argentina. Moraine morphology, stratigraphic relationships, radiocarbon ages obtained from peat on these glacial deposits and the proximity to the active glaciers enabled us to reconstruct the LIA advance in this area. The LIA maximum advance occurred between cal. yr 1550 and 1720 AD, and a readvance occurred around cal. yr 1830 AD. In addition, glacier fluctuations of the Las Vacas and Güssfeltd glaciers (33°S) and El Peñón and El Azufre glaciers were documented from the end of the 19th century to the present based on historical and aerial photographs, and satellite images. The glaciers showed a marked retreat during 1894–2007. Minor readvances occurred in the 1980s and 1990s, which could be related with strong warm ENSO events during these decades. Our results are consistent with observations made by other authors in the region. [Copyright &y& Elsevier]

The discussion on our paper on Paleoproterozoic glaciation arises out of the failure of previous geological mapping in the Sausar belt to identify many features, which were reported earlier, and to examine the outcrops critically for evidence of volcanism and glaciation in Central India. The details of these are given in this reply. [ABSTRACT FROM AUTHOR]

Abstract: Local environmental conditions under dense canopy are known to result in depletion in 13C abundance in plants compared to an open land context. This canopy effect has been observed in tropical as well as in mid-latitude forest ecosystems. However, the impact of the canopy effect on tissue 13C abundance of temperate and boreal forest-dwelling herbivores has not been thoroughly explored. Nevertheless, the canopy effect has been suggested to explain a decrease of about 3‰ in collagen δ 13C values in ancient large herbivores from western Europe during the forest expansion of the Late-Glacial–Early Holocene period (ca. 15,000–6000 cal BP). Some papers have considered the 13C decrease in large herbivore as the main result of global change in atmospheric CO2 content. A detailed review of δ 13C values of large herbivores (reindeer, red deer, roe deer, and bison) from open and closed environments from high and mid-latitudes confirm that the canopy effect observed in plants is passed on to their consumers. In the Paris Basin, the decline in δ 13C values of large herbivores at the Late-Glacial/Early Holocene transition around 10,000 years BP appears to be different according to the considered species, namely red deer, roe deer, and large bovines (bison and aurochs). Moreover, differences in the pattern of decrease in δ 13C values are observed in red deer between French northern Alps and French Jura. These differences among species in their isotopic response through time for a given geographical location, and within species from different locations, suggest variance in ecological responses of species that are associated with the relative use of forested habitat. As a result, 13C abundances in collagen can be considered as a direct tracker of the degree of closure of the habitat of ancient herbivores. [Copyright &y& Elsevier]

Abstract: Stable isotope ratios (reported as δ 13C) of organic carbon preserved in paleosols have potential utility as a valuable paleoecological indicator if the isotopic composition of paleobiomass is preserved in the paleosol organic carbon without fractionation. However, soil organic matter is in a constant state of decomposition in an open system, and frequently decomposes further during alteration after burial of the paleosol. During this decomposition, kinetic fractionation of 13C/12C in an open system results in concentration of 13C in the residual organic matter preserved in the soil and paleosol. This paper summarizes studies of modern soils which show that this 13C-enrichment follows a Rayleigh distillation process whereby the 13C/12C ratio is a function of the natural logarithm of the fraction of remaining soil organic carbon, leaving soil organic carbon 13C-enriched by up to ∼6‰ with respect to the original biomass. If the fraction of original biomass carbon remaining during these decomposition processes deviates significantly from 1, the soil organic carbon can be 13C-enriched by several per mil, and thus not a good paleoecological indicator of the δ 13C value of the original biomass. Therefore, effective paleoecological studies of δ 13C preserved in paleosol organic carbon must therefore demonstrate that the measured concentration of organic carbon in the paleosol is near its maximum concentration during soil formation, or that the paleosol organic matter does not include the 13C-enriched products of microbial decomposition. Suggestions are made for interpreting the effects of carbon isotope fractionation of organic matter, and for materials and methods most useful for paleoecological studies from bulk paleosol organic carbon. [Copyright &y& Elsevier]

Abstract: The natural abundance of C3 and C4 plants is affected by multiple environmental factors including temperature, moisture balance and atmospheric pCO2. The relative importance of these factors is a subject of considerable debate, and may vary in different natural ecosystems. Previous studies generally focus on single loess sequences in the Chinese Loess Plateau, and conflicting conclusions on C4/C3 have been reached when studying carbon isotope ratios in carbonate and organic matter. In this paper we report a comprehensive carbon isotopic characterization of total organic carbon (TOC) and individual higher plant leaf waxes from five loess sequences spanning the last 35 ka from the Chinese Loess Plateau (CLP). The five coring sites encompass large gradients of annual mean temperature (9.2–13.9 °C) and precipitation (402–673 mm), allowing us to assess the controlling mechanisms on C4/C3 plant ratios. Glacial–interglacial sequences provide carbon isotope data for comparison with other climatic and environmental proxies such as lithology and magnetic susceptibility. Our results demonstrate that increased C4/C3 ratios are positively correlated with higher temperature and increased summer rainfall which characterize stronger summer monsoon in all five sites. We conclude C4 abundance increases from the last glacial to the Holocene in response to greater monsoon activity and that the C4 expression is suppressed in the cold and drier intervals. [Copyright &y& Elsevier]

The middle–late Cambrian is a key interval between the Cambrian Explosion and the Great Ordovician Biodiversification Event (GOBE) that marks a major biologic evolutionary transition in the geologic record. Diversity (i.e. richness) patterns in this interval show that macro-biota experienced evolutionary setbacks for the first time. However, relatively little attention has been paid to this interval in previous macroevolutionary studies and very different conclusions about the diversity patterns in coarse time-resolution have been documented. As a dominate group of marine benthic organisms in the Cambrian, trilobites provide insightful information to understand the history of biodiversity in the Cambrian marine ecosystem from the Cambrian Explosion to the GOBE. South China is a region with relatively good preservation of Cambrian fossil materials and sections, and 4 out of 6 Cambrian GSSPs were established in South China. In this paper, we use constrained optimization (CONOP) to correlate 19 sections from South China to reduce the Signor-Lipps effect and integrate the results with high-resolution chronostratigraphic data to evaluate the middle–late Cambrian trilobite diversity pattern in South China. This study, for the first time, constructs a high time-resolution (about 60 kyr) trilobite species-level richness curve with estimated time from Age 4 to the Paibian. A double-peaked species diversification is separated by a minor extinction in Stage 4; this is followed by a gradual decline of species diversity over the entire Wuliuan Age. A radiation of three times increase of species diversity in the Drumian and Guzhangian is exhibited and the diversity remains high for most of the Guzhangian Stage; this is followed by a great extinction at the end of the Guzhangian with around 50% species lost. Detailed comparison with previous composite studies and fossil material from single sections revealed that the Signor-Lipps effect could produce large biases in diversity pattern. In addition, a precise analysis of species evolution features compared with environmental indices provides a perspective about trilobite evolutionary mechanisms associated with environmental changes related to the carbon cycle and biotic competition. • Middle-late Cambrian trilobite diversity trajectory of South China is established. • High temporal resolution of diversity pattern is produced with CONOP method. • The results reveal two major diversity losses and a biodiversification event in Guzhuangian. • Signor-Lipps effect may affect diversity pattern significantly. • Major extinctions of trilobites are correlative with carbon isotope excursions. [ABSTRACT FROM AUTHOR]

Abstract: The research reported by Jaesoo Lim et al. (2010) (Jaesoo Lim, Wook-Hyun Nahm, Jin-Kwan Kim, Dong-Yoon Yang, 2010. Regional climate-driven C 3 and C 4 plant variation in the Cheollipo area, Korea, during the late Pleistocene. Palaeogeography, Palaeoclimatology, Palaeoecology 298, 370–377) provides an interesting northeast Asian case for palaeoecological response to palaeoclimatic change. However the method used in the paper to determine the contribution of C3 and C4 plant in bulk organic carbon isotope values deserves discussion when the proportion of C3 and C4 plant is used as an important indicator for palaeoecological analysis. [Copyright &y& Elsevier]