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23. Spatial distribution of remaining movable and non-movable oil fractions in a depleted Maastrichtian chalk reservoir, Danish North Sea:Implications for CO2 storage

Author

Petersen, Henrik I., Blinkenberg, Kasper H., Anderskouv, Kresten, Rudra, Arka, Zheng, Xiaowei, Sanei, Hamed, Petersen, Henrik I., Blinkenberg, Kasper H., Anderskouv, Kresten, Rudra, Arka, Zheng, Xiaowei, and Sanei, Hamed

Abstract

Depleted oil and gas fields constitute potentially important storage sites for CO2 in the subsurface, but large-scale injection of supercritical (sc) CO2 in chalk has not yet been attempted. One of the risks is the adverse effect of the substantial amount of remaining oil in the chalk reservoirs on scCO2 injection. In order to counter an undesired effect on injectivity, a fundamental understanding of the spatial distribution and quantity of the movable, semi-movable, and non-movable oil, and solid bitumen/asphaltenes fractions of the remaining oil is critical. In this study a combination of organic geochemistry (gas chromatography of the saturated fraction and programmed pyrolysis), and reflected light microscopy was applied to evaluate and measure the spatial distribution, volume, and saturation of different oil fractions in a well-defined reservoir interval of a waterflooded Maastrichtian chalk reservoir in the Danish Central Graben, North Sea. A total of 127 samples from a slightly deviated vertical well and two ∼5 km-long horizontal wells from the Halfdan and Dan fields were analyzed. An original uneven distribution of oil saturation and composition or different production efficiency of different levels in the reservoir may account for variations in the total oil and oil fraction saturations. Gas chromatography shows that the solvent extractable oil is quite similar in composition, characterized by a dominance of polar compounds and a high content of asphaltenes. Extended slow heating (ESH) pyrolysis reveals that most of the remaining oil saturation consists of semi-movable oil and total non-movable oil (non-movable oil plus solid bitumen/asphaltenes). Reduced oil gravity values (API) are related to evaporation loss of the lightest hydrocarbon fraction during core storage and increase of the relative proportion of the heavier oil fractions by waterflooding during production. Microscopy disclosed three forms of oil: i) Patchy d

Published
2024

27. From land to sea: provenance, composition, and preservation of organic matter in a marine sediment record from the North‐East Greenland shelf spanning the Younger Dryas–Holocene

Author

Andreasen, Nanna, primary, Jackson, Rebecca, additional, Rudra, Arka, additional, Nøhr‐Hansen, Henrik, additional, Sanei, Hamed, additional, Bojesen‐Koefoed, Jørgen, additional, Seidenkrantz, Marit‐Solveig, additional, Pearce, Christof, additional, Thibault, Nicolas, additional, and Ribeiro, Sofia, additional

Published
2023
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28. From land to sea:provenance, composition, and preservation of organic matter in a marine sediment record from the North-East Greenland shelf spanning the Younger Dryas–Holocene

Author

Andreasen, Nanna, Jackson, Rebecca, Rudra, Arka, Nøhr-Hansen, Henrik, Sanei, Hamed, Bojesen-Koefoed, Jørgen, Seidenkrantz, Marit-Solveig, Pearce, Christof, Thibault, Nicolas, Ribeiro, Sofia, Andreasen, Nanna, Jackson, Rebecca, Rudra, Arka, Nøhr-Hansen, Henrik, Sanei, Hamed, Bojesen-Koefoed, Jørgen, Seidenkrantz, Marit-Solveig, Pearce, Christof, Thibault, Nicolas, and Ribeiro, Sofia

Abstract

The organic matter content of marine sediments is often used to infer past changes in ocean conditions. However, the organic carbon pool preserved in coastal sediments is a complex mixture derived from different sources and may not reflect in situ processes. In this study, we combine taxonomic identification of reworked palynomorphs with pyrolysis organic geochemistry and reflected-light organic petrographic microscopy to investigate the provenance, composition and preservation of organic matter in a marine sediment core retrieved from the NE Greenland shelf. Our study reveals continuous yet variable input of land-derived organic carbon to the marine environment throughout the late Younger Dryas–Holocene, with the highest input of inert carbon in the late Younger Dryas. Although the sediments contain some recent marine palynomorphs, there is no other evidence of fresh marine organic carbon. In contrast, our results indicate that these shelf sediments represent a significant sink of recycled organic carbon. The results of pyrolysis geochemistry revealed that ~90% of the total organic carbon in the sediments is inert. The organic petrography analyses revealed that >70–84% of the organic carbon in the sediment core is terrigenous. Reworked dinoflagellate cysts showed a continuous provenance of Cretaceous land-derived material, most likely from the nearby Clavering Island. Our study points to the importance of constraining the organic matter origin, composition and preservation in marine sediments to achieve more accurate palaeoenvironmental reconstructions based on organic proxies.

Published
2023

29. Triassic-Jurassic vegetation response to carbon cycle perturbations and climate change

Author

Marine palynology and palaeoceanography, Stratigraphy and paleontology, Marine Palynology, Bos, Remco, Lindström, Sofie, van Konijnenburg-van Cittert, Han, Hilgen, Frederik, Hollaar, Teuntje P., Aalpoel, Hendrik, van der Weijst, Carolien, Sanei, Hamed, Rudra, Arka, Sluijs, Appy, van de Schootbrugge, Bas, Marine palynology and palaeoceanography, Stratigraphy and paleontology, Marine Palynology, Bos, Remco, Lindström, Sofie, van Konijnenburg-van Cittert, Han, Hilgen, Frederik, Hollaar, Teuntje P., Aalpoel, Hendrik, van der Weijst, Carolien, Sanei, Hamed, Rudra, Arka, Sluijs, Appy, and van de Schootbrugge, Bas

Published
2023

30. Organic geochemical and petrographic characteristics of the Cambrian-Ordovician organic-rich marine shales in Scandinavia.

Author

Xiao-Wei Zheng, Schovsbo, Niels-H., Lei-Bo Bian, Rudra, Arka, and Sanei, Hamed

Abstract

This work used organic geochemistry and organic petrology to study the depositional environment, organic matter characteristics, and thermal maturity of the Cambrian-Ordovician organic-rich marine shales in the Baltic Basin. The main macerals in Cambrian samples include alginite, bituminite and solid bitumen, while zooclastic macerals become the major proportion of organic matter in the Ordovician samples. As the maturity increase, solid bitumen becomes abundant and dispersed. Semifusinite-like maceral was observed only in Furongian of well DBH15/73, which probably indicates the local intrusion of Permo-Carboniferous dolerite dikes. The programmed pyrolysis results show that immature, early mature, and over-mature samples are developed. However, the data of high-uranium Furongian samples were greatly altered by igneous intrusives from local dikes. HIo calculation model is simulated based on pyrolysis data and fitted according to the least-square fitting method. The simulated fitting HIo: 400mg HC/g TOC (369.5 mg HC/g TOC, 430.5 mg HC/g TOC as 95% confidence bounds) is within the worldwide marine shale HIo and indicates a marine anoxia and transgressive sea with shallow water column (organofacies B). [ABSTRACT FROM AUTHOR]

Published
2023
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34. Sinking krill carcasses as hotspots of microbial carbon and nitrogen cycling in the Arctic

Author

Franco-Cisterna, Belén, Glud, Anni, Bristow, Laura A., Rudra, Arka, Sanei, Hamed, Winding, Mie H.S., Nielsen, Torkel G., Glud, Ronnie N., Stief, Peter, Franco-Cisterna, Belén, Glud, Anni, Bristow, Laura A., Rudra, Arka, Sanei, Hamed, Winding, Mie H.S., Nielsen, Torkel G., Glud, Ronnie N., and Stief, Peter

Abstract

Krill represent a major link between primary producers and higher trophic levels in polar marine food webs. Potential links to lower trophic levels, such as heterotrophic microorganisms, are less well documented. Here, we studied the kinetics of microbial degradation of sinking carcasses of two dominant krill species Thysanoessa raschii and Meganyctiphanes norvegica from Southwest Greenland. Degradation experiments under oxic conditions showed that 6.0-9.1% of carbon and 6.4-7.1% of nitrogen were lost from the carcasses after one week. Aerobic microbial respiration and the release of dissolved organic carbon were the main pathways of carbon loss from the carcasses. Ammonium release generally contributed the most to carcass nitrogen loss. Oxygen micro profiling revealed anoxic conditions inside krill carcasses/specimens, allowing anaerobic nitrogen cycling through denitrification and dissimilatory nitrate reduction to ammonium (DNRA). Denitrification rates were up to 5.3 and 127.7 nmol N carcass-1 d-1 for T. raschii and M. norvegica, respectively, making krill carcasses hotspots of nitrogen loss in the oxygenated water column of the fjord. Carcass-associated DNRA rates were up to 4-fold higher than denitrification rates, but the combined activity of these two anaerobic respiration processes did not contribute significantly to carbon loss from the carcasses. Living krill specimens did not harbor any significant denitrification and DNRA activity despite having an anoxic gut as revealed by micro profiling. The investigated krill carcasses sink fast (1500-3000 m d-1) and our data show that only a small fraction of the associated carbon is lost during descent. Based on data on krill distribution, our findings are used to discuss the potential importance of sinking krill carcasses for sustaining benthic food webs in the Arctic.

Published
2022

37. Characterization of organic matter in marine sediments to estimate age offset of bulk radiocarbon dating

Author

Hansen, Katrine Elnegaard, Giraudeau, Jacques, Limoges, Audrey, Massé, Guillaume, Rudra, Arka, Wacker, Lukas, Sanei, Hamed, and Seidenkrantz, Marit-Solveig

Subjects
Radiocarbon dating, Marine sediments, Age offset, Holocene, Bulk organic matter, Organic pyrolysis
Abstract

Radiocarbon dating of Arctic marine sediment is often challenging due to the low availability of calcareous fossils. Consequently, bulk organic matter dating has at times been used to establish sediment core chronologies. Yet, radiocarbon dates based on bulk organic matter often appear to deviate vastly from dates based on fossils, mainly caused by input of allochthounous carbon, including terrigenous organic matter. In this study, we aim to examine the link between the composition of the bulk organic matter and the age offsets between the bulk radiocarbon dates and those obtained from calcareous foraminiferal tests. All samples are taken from the marine sediment core AMD14-204C from offshore Upernavik (eastern Baffin Bay). The radiocarbon dates for bulk organic matter are on average ~3000 years older than the radiocarbon dates based on foraminifera, but with changing age offsets throughout the record. To investigate the cause of this age offset and its variations over time, we applied core scanning, X-ray Fluorescence analysis, stable isotopes, organic pyrolysis and microscopic organic petrology to examine the distribution and characterization of the organic matter. The results show that the older organic matter includes clastic input of reworked sedimentary rocks potentially originating from West Greenland and/or the Canadian Arctic Archipelago. Changes in the input of contemporary marine algal produced organic matter versus both terrigenous input and reworked ancient organic matter appear to control the age offsets between the bulk and foraminifera dates. A low Hydrogen Index and low δ13Corg values together with a high Oxygen Index, indicative of high influence of terrigenous organic matter, seem to correspond to samples with the largest age offsets; 1000–2000 years greater than in other samples. To examine the cause of the variations in the age offsets, a new quantification of the autochthonous organic matter as a fraction of the TOC was calculated. This shows that samples with the largest age offsets contained the lowest fraction (as low as ~12%) of autochthonous organic matter in the TOC.

Published
2021

38. Characterization of organic matter in marine sediments to estimate age offset of bulk radiocarbon dating

Author

Hansen, Katrine, Giraudeau, Jacques, Limoges, Audrey, Massé, Guillaume, Rudra, Arka, Wacker, Lukas, Sanei, Hamed, Pearce, Christof, Seidenkrantz, Marit-Solveig, Hansen, Katrine Elnegaard, Aarhus University [Aarhus], Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Department of Earth Sciences, University of New Brunswick, University of New Brunswick (UNB), Takuvik International Research Laboratory, Université Laval [Québec] (ULaval)-Centre National de la Recherche Scientifique (CNRS), Variabilité de l'Océan et de la Glace de mer (VOG), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Laboratory of Ion Beam Physics, and Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)

Subjects
Radiocarbon dating, 010506 paleontology, Age offset, 010504 meteorology & atmospheric sciences, Stratigraphy, Geochemistry, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 01 natural sciences, law.invention, Organic pyrolysis, Foraminifera, Marine sediments, law, Earth and Planetary Sciences (miscellaneous), Organic matter, 14. Life underwater, 0105 earth and related environmental sciences, chemistry.chemical_classification, biology, Holocene, Terrigenous sediment, Stable isotope ratio, Sediment, Geology, biology.organism_classification, Bulk organic matter, chemistry, 13. Climate action, Clastic rock, Sedimentary rock
Abstract

Radiocarbon dating of Arctic marine sediment is often challenging due to the low availability of calcareous fossils. Consequently, bulk organic matter dating has at times been used to establish sediment core chronologies. Yet, radiocarbon dates based on bulk organic matter often appear to deviate vastly from dates based on fossils, mainly caused by input of allochthounous carbon, including terrigenous organic matter. In this study, we aim to examine the link between the composition of the bulk organic matter and the age offsets between the bulk radiocarbon dates and those obtained from calcareous foraminiferal tests. All samples are taken from the marine sediment core AMD14-204C from offshore Upernavik (eastern Baffin Bay). The radiocarbon dates for bulk organic matter are on average similar to 3000 years older than the radiocarbon dates based on foraminifera, but with changing age offsets throughout the record. To investigate the cause of this age offset and its variations over time, we applied core scanning, X-ray Fluorescence analysis, stable isotopes, organic pyrolysis and microscopic organic petrology to examine the distribution and characterization of the organic matter. The results show that the older organic matter includes clastic input of reworked sedimentary rocks potentially originating from West Greenland and/or the Canadian Arctic Archipelago. Changes in the input of contemporary marine algal produced organic matter versus both terrigenous input and reworked ancient organic matter appear to control the age offsets between the bulk and foraminifera dates. A low Hydrogen Index and low delta C-13(org) values together with a high Oxygen Index, indicative of high influence of terrigenous organic matter, seem to correspond to samples with the largest age offsets; 1000-2000 years greater than in other samples. To examine the cause of the variations in the age offsets, a new quantification of the autochthonous organic matter as a fraction of the TOC was calculated. This shows that samples with the largest age offsets contained the lowest fraction (as low as similar to 12%) of autochthonous organic matter in the TOC. ISSN:1871-1014

Published
2021
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43. A possible phytosaurian (Archosauria, Pseudosuchia) coprolite from the Late Triassic Fleming Fjord Group of Jameson Land, central East Greenland.

Author

MILÁN, JESPER, MATEUS, OCTÁVIO, MAU, MALTE, RUDRA, ARKA, SANEI, HAMED, and CLEMMENSEN, LARS B.

Subjects
FJORDS, CROCODILIANS, VERTEBRATES, SEDIMENTS, COPROLITES, MORPHOLOGY
Abstract

A large, well-preserved vertebrate coprolite was found in a lacustrine sediment in the Malmros Klint Formation of the Late Triassic Fleming Fjord Group in the Jameson Land Basin, central East Greenland. The size and internal and external morphology of the coprolite is consistent with that of crocodilian coprolites and one end of the coprolite exhibits evidence of post-egestion trampling. As the associated vertebrate fauna of the Fleming Fjord Group contains abundant remains of pseudosuchian phytosaurs, the coprolite is interpreted as being from a large phytosaur. [ABSTRACT FROM AUTHOR]

Published
2021
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45. Molecular structure and long-term stability of biochars.

Author

Rudra, Arka, Petersen, Henrik I., and Sanei, Hamed

Subjects
MOLECULAR structure, BIOCHAR, CARBON sequestration, ENVIRONMENTAL management, PYROLYSIS
Abstract

Biochars are increasingly used to improve the productivity of agricultural soils as well as for long-term carbon sequestration (Petersen et al., 2023). The wastes from biomass are used to manufacture biochar as a clean and sustainable environmental solution. The pyrolysis of biomass generates biofuel, which can be utilized for generating energy and solid biochar. However, there lacks an understanding about the structural stability of the biochars generated through various pyrolytic processes. The objective of the study is to understand the molecular structural remnants of the biochar from different biomasses and assess the long-term stability of the macromolecule. For this, various agricultural biomass, food wastes and urban sludge are pyrolysed at temperatures ranging from 450-900°C and converted into biochars, which are further analyzed with a pyrolysis-gas chromatography-mass spectrometry. The biochars were flash pyrolysed at 700°C (0.2 min) and the pyrolysis products were studied by GC-MS. The GC temperature was initially set at 50°C, and then ramped up to 300°C at a rate of 10°C/min. The results show that the pyrolysates from the studied biochars produced at lower temperatures (400-500°C) contain larger, 3-4 ring aromatic compounds (PAH) as well as their methylated compounds. Aliphatic compounds are entirely missing. Pyrolysates from the lower pyrolysis temperatures are susceptible to produce secondary compounds, leading to formation of alkylated aromatic compounds. The degree of methylation and aromaticity of biochars produced from different biomass is likely to be function of the ratio of labile:refractory carbon of the feedstock as well as the maximum temperature of pyro lysis at which biochars have been produced. Therefore, biochars produced at low temperatures having large macromolecular size and linked via methyl chains are susceptible to break off at the methylated bonds and further susceptible to microbial and thermal degradation. With the increasing biochar production temperatures, the degree of methylation decreases along with more condensation of the macromolecule. Therefore, the pyrolysates show no methyl bonds and only scarce amount of single or two ring aromatic compounds. Biochars having such condensed macromolecular structure can be utilized as longterm carbon sequestration. [ABSTRACT FROM AUTHOR]

Published
2023

46. Spatial and temporal changes in the organic matter supply during the Cenozoic basin evolution in the Danish North Sea.

Author

Zhiheng Zhou, Petersen, Henrik I., Schovsbo, Niels H., Rudra, Arka, and Sanei, Hamed

Subjects
ORGANIC compounds, CENOZOIC Era, CARBON sequestration in forests, FLUORESCENCE microscopy
Abstract

The mudstones of the Upper Eocene - Middle Miocene Lark Formation in the Danish North Sea have not been the subject of a detailed organic petrographic and geochemical investigation despite its importance for paleoclimate studies and as a regional seal for potential CO2 storage sites. This study investigates the characteristics and quantity of organic matter in 391 samples of cuttings obtained from 7 wells from the Danish North Sea. The Hawk pyrolysis was conducted on all cuttings samples while reflected light and fluorescence microscopy was conducted on 38 pellets for determining the reflectance of primary huminite (HRo), the volume percentage of huminite and inertinite (H+I, vol.%) and the intensity ratio of red to green light of alginite (R/G quotient). The results show that the organic matter in the Lark Formation is generally immature (Tmax < 430°C, HRo mean value = 0.3%, R/G mean value = 0.51) and mainly consists of Type III kerogen which is dominated by huminite macerals, with the total organic carbon (TOC) content ranging from 0.33 wt.% to 7.34 wt.% (mean value = 2.54 wt.%). In a north distal site, we observed a long-term decrease in hydrogen index (HI) caused by the increase in TOC outpaced S2 during Oligocene to Early Miocene. In the south distal sites in the Danish Central Graben, we noticed the increase in HI resulted from the jump in TOC and S2 during Early Miocene to Middle Miocene. The increase in TOC was proved to be the result of the increased influx of terrestrial organic matter as we established the positive correlation (R²>0.95) between the volume percentage of total organic carbon (TOC, vol.%) and that of huminite and inertinite (H+I, vol.%). This increased influx proved further being the result of changes in organic matter supply from N to NE and then ENE direction during the Cenozoic Basin Evolution in the Danish North Sea. [ABSTRACT FROM AUTHOR]

Published
2023

48. Characterization of organic matter in marine sediments to estimate age offset of bulk radiocarbon dating

Author

Hansen, Katrine Elnegaard, Giraudeau, Jacques, Limoges, Audrey, Massé, Guillaume, Rudra, Arka, Wacker, Lukas, Sanei, Hamed, Pearce, Christof, and Seidenkrantz, Marit-Solveig

Subjects
Radiocarbon dating, Marine sediments, Age offset, Holocene, 13. Climate action, 14. Life underwater, Bulk organic matter, Organic pyrolysis
Abstract

Radiocarbon dating of Arctic marine sediment is often challenging due to the low availability of calcareous fossils. Consequently, bulk organic matter dating has at times been used to establish sediment core chronologies. Yet, radiocarbon dates based on bulk organic matter often appear to deviate vastly from dates based on fossils, mainly caused by input of allochthounous carbon, including terrigenous organic matter. In this study, we aim to examine the link between the composition of the bulk organic matter and the age offsets between the bulk radiocarbon dates and those obtained from calcareous foraminiferal tests. All samples are taken from the marine sediment core AMD14-204C from offshore Upernavik (eastern Baffin Bay). The radiocarbon dates for bulk organic matter are on average similar to 3000 years older than the radiocarbon dates based on foraminifera, but with changing age offsets throughout the record. To investigate the cause of this age offset and its variations over time, we applied core scanning, X-ray Fluorescence analysis, stable isotopes, organic pyrolysis and microscopic organic petrology to examine the distribution and characterization of the organic matter. The results show that the older organic matter includes clastic input of reworked sedimentary rocks potentially originating from West Greenland and/or the Canadian Arctic Archipelago. Changes in the input of contemporary marine algal produced organic matter versus both terrigenous input and reworked ancient organic matter appear to control the age offsets between the bulk and foraminifera dates. A low Hydrogen Index and low delta C-13(org) values together with a high Oxygen Index, indicative of high influence of terrigenous organic matter, seem to correspond to samples with the largest age offsets; 1000-2000 years greater than in other samples. To examine the cause of the variations in the age offsets, a new quantification of the autochthonous organic matter as a fraction of the TOC was calculated. This shows that samples with the largest age offsets contained the lowest fraction (as low as similar to 12%) of autochthonous organic matter in the TOC., Quaternary Geochronology, 67, ISSN:1871-1014

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