52134
2018
2018
eng
126
135
10
123
article
Elsevier
Oxford
1
2018-05-25
--
--
Correction for the siderite effect on Rock-Eval parameters
Originally developed for use in the petroleum industry, Rock-Eval pyrolysis is a technique commonly applied to lake sediments to infer paleoenvironmental reconstructions. The standard Rock-Eval parameters provide information on the amount of total organic and inorganic carbon (TOC and MinC, respectively), and are usually interpreted as proxies for the source (aquatic or terrestrial) of the primary production of organic matter (Hydrogen Index vs Oxygen Index). Although this method usually provides valuable evidence, the common presence of siderite in tropical lake sediments can alter the primary signal of the sedimentary organic matter (SOM). Indeed, the CO2 and CO released by the pyrolysis of siderite are integral to the calculation of the SOM-related standard Rock-Eval parameters. In this study, we analyze sediments from a core collected in the Lake Barombi (southwest Cameroon) and describe the impact of siderite on standard Rock-Eval parameters. We propose a workflow that allows standard Rock-Eval parameters to be corrected, based on the analysis of thermograms. The proposed corrections provide siderite-effect-free parameters, accurately reflecting the changes in sedimentary organic matter composition. (C) 2018 Elsevier Ltd. All rights reserved.
Organic geochemistry : the international journal for rapid publication of current research in organic geochemistry and biochemistry
Application to the sediments of Lake Barombi (southwest Cameroon)
10.1016/j.orggeochem.2018.05.010
0146-6380
wos:2018
WOS:000441281900012
Sebag, D (reprint author), Normandie Univ, CNRS, UNICAEN, UNIROUEN,M2C, F-76000 Rouen, France., david.sebag@univ-rouen.fr
2021-10-11T13:41:46+00:00
sword
importub
filename=package.tar
76795896da38400b8498c4bfc6d0a89c
false
true
David Sebag
Yannick Garcin
Thierry Adatte
Pierre Deschamps
Guillemette Menot
Eric P. Verrecchia
eng
uncontrolled
Organic geochemistry
eng
uncontrolled
Rock-Eval pyrolysis
eng
uncontrolled
Van Krevelen diagram
eng
uncontrolled
Siderite
eng
uncontrolled
Tropical lake
eng
uncontrolled
Western Central Africa
Geowissenschaften
Institut für Geowissenschaften
Referiert
Import
52624
2018
2018
eng
348
362
15
191
article
Elsevier
Oxford
1
2018-05-26
--
--
Pedo-sedimentary constituents as paleoenvironmental proxies in the Sudano-Sahelian belt during the Late Quaternary (southwestern Chad Basin)
Climate and environmental changes since the Last Glacial Maximum in the tropical zone of West Africa are usually inferred from marine and continental records. In this study, the potential of carbonate pedo-sedimentary geosystems, i.e. Vertisol relics, to record paleoenvironmental changes in the southwestern part of Chad Basin are investigated. A multi-dating approach was applied on different pedogenic organo-mineral constituents. Optically stimulated luminescence (OSL) dating was performed on the soil K-rich feldspars and was combined with radiocarbon dating on both the inorganic (C-14(inorg)) and organic carbon (C-14(org)) soil fractions. Three main pedo-sedimentary processes were assessed over the last 20 ka BP: 1) the soil parent material deposition, from 18 ka to 12 ka BP (OSL), 2) the soil organic matter integration, from 11 cal ka to 8 cal ka BP (C-14(org)), and 3) the pedogenic carbonate nodule precipitation, from 7 cal ka to 5 cal ka BP (C-14(inorg)). These processes correlate well with the Chad Basin stratigraphy and West African records and are shown to be related to significant changes in the soil water balance responding to the evolution of continental hydrology during the Late Quaternary. The last phase affecting the Vertisol relics is the increase of erosion, which is hypothesized to be due to a decrease of the vegetation cover triggered by (i) the onset of drier conditions, possibly strengthened by (ii) anthropogenic pressure. Archaeological data from Far North Cameroon and northern Nigeria, as well as sedimentation times in Lake Tilla (northeastern Nigeria), were used to test these relationships. The increase of erosion is suggested to possibly occur between c. 3 cal ka and 1 cal ka BP. Finally, satellite images revealed similar geosystems all along the Sudano-Sahelian belt, and initial C-14(inorg) ages of the samples collected in four sites gave similar ages to those reported in this study. Consequently, the carbonate pedo-sedimentary geosystems are valuable continental paleoenvironmental archives and soil water balance proxies of the semiarid tropics of West Africa. (C) 2018 Elsevier Ltd. All rights reserved.
Quaternary science reviews : the international multidisciplinary research and review journal
10.1016/j.quascirev.2018.05.022
0277-3791
wos:2018
WOS:000437363000022
Diaz, N (reprint author), Royal Holloway Univ London, Dept Geog, Egham TW20 0EX, Surrey, England., Nathalie.Diaz@rhul.ac.uk
French National Research Institute for Sustainable Development (IRD); Swiss National Science Foundation (SNSF)Swiss National Science Foundation (SNSF) [200021-147038]; SNSFSwiss National Science Foundation (SNSF) [PZ00P2-167960, ND P2LAP2_174595]; Labex OT-Med
2021-11-12T11:07:46+00:00
sword
importub
filename=package.tar
64417972f31ab9aeb0c6e7bc398e95b0
Diaz, Nathalie
false
true
Nathalie Diaz
Fabienne Dietrich
David Sebag
Georgina E. King
Pierre G. Valla
Alain Durand
Yannick Garcin
Geoffroy de Saulie
Pierre Deschamps
Frederic Herman
Eric P. Verrecchia
eng
uncontrolled
Pedogenic carbonate nodules
eng
uncontrolled
Vertisol genesis
eng
uncontrolled
Soil water balance
eng
uncontrolled
Optical methods
eng
uncontrolled
Radiogenic isotopes
eng
uncontrolled
Quaternary
eng
uncontrolled
Monsoon
eng
uncontrolled
Western Africa
Geowissenschaften
Institut für Geowissenschaften
Referiert
Import
48940
2019
2019
eng
213
231
19
215
article
Elsevier
Oxford
Olorgesailie Drilling Project Sci
1
2019-05-29
--
--
Chronostratigraphic model of a high-resolution drill core record of the past million years from the Koora Basin, south Kenya Rift: Overcoming the difficulties of variable sedimentation rate and hiatuses
The Olorgesailie Drilling Project and the related Hominin Sites and Paleolakes Drilling Project in East Africa were initiated to test hypotheses and models linking environmental change to hominin evolution by drilling lake basin sediments adjacent to important archeological and paleoanthropological sites. Drill core OL012-1A recovered 139 m of sedimentary and volcaniclastic strata from the Koora paleolake basin, southern Kenya Rift, providing the opportunity to compare paleoenvironmental influences over the past million years with the parallel record exposed at the nearby Olorgesailie archeological site. To refine our ability to link core-to-outcrop paleoenvironmental records, we institute here a methodological framework for deriving a robust age model for the complex lithostratigraphy of OL012-1A. Firstly, chronostratigraphic control points for the core were established based on 4 Ar/39Ar ages from intercalated tephra deposits and a basal trachyte flow, as well as the stratigraphic position of the Brunhes-Matuyama geomagnetic reversal. This dataset was combined with the position and duration of paleosols, and analyzed using a new Bayesian algorithm for high-resolution age-depth modeling of hiatus-bearing stratigraphic sections. This model addresses three important aspects relevant to highly dynamic, nonlinear depositional environments: 1) correcting for variable rates of deposition, 2) accommodating hiatuses, and 3) quantifying realistic age uncertainty with centimetric resolution. Our method is applicable to typical depositional systems in extensional rifts as well as to drill cores from other dynamic terrestrial or aquatic environments. We use the core age model and lithostratigraphy to examine the inter connectivity of the Koora Basin to adjacent areas and sources of volcanism. (C) 2019 Elsevier Ltd. All rights reserved.
Quaternary science reviews : the international multidisciplinary research and review journal
10.1016/j.quascirev.2019.05.009
0277-3791
wos:2019
WOS:000474318200015
Deino, AL (reprint author), Berkeley Geochronol Ctr, 2455 Ridge Rd, Berkeley, CA 94709 USA., adeino@bgc.org
National Museums of Kenya; Oldonyo Nyokie Group Ranch; Peter Buck Fund for Human Origins Research (Smithsonian); William H. Donner Foundation; National Science FoundationNational Science Foundation (NSF) [EAR 1322017]; Smithsonian Postdoctoral FellowshipSmithsonian Institution; Geo. X, the Research Network for Geosciences in Berlin, Germany; Geo. X, the Research Network for Geosciences in Potsdam, Germany; Swiss National Science FoundationSwiss National Science Foundation (SNSF) [P300P2 158501]
2021-01-15T16:21:04+00:00
sword
importub
filename=package.tar
8ad682210e7d99b13ea546335e67dfe0
Deino, A. L
false
true
A. L. Deino
René Dommain
C. B. Keller
R. Potts
A. K. Behrensmeyer
E. J. Beverly
J. King
C. W. Heil
M. Stockhecke
E. T. Brown
J. Moerman
P. deMenocal
D. Deocampo
Yannick Garcin
N. E. Levin
R. Lupien
R. B. Owen
N. Rabideaux
J. M. Russell
J. Scott
S. Riedl
K. Brady
J. Bright
J. B. Clark
A. Cohen
J. T. Faith
A. Noren
V. Muiruri
R. Renaut
S. Rucina
K. Uno
eng
uncontrolled
Pleistocene
eng
uncontrolled
Paleolimnology
eng
uncontrolled
East Africa
eng
uncontrolled
Sedimentology
eng
uncontrolled
Radiogenic isotopes
eng
uncontrolled
Bayesian modeling
eng
uncontrolled
paleosol
eng
uncontrolled
Tephrostratigraphy
eng
uncontrolled
Magnetostratigraphy
eng
uncontrolled
Kenya Rift
Geowissenschaften
Institut für Geowissenschaften
Referiert
Import
36131
2012
2012
eng
106
126
21
4
79
article
Elsevier
Oxford
1
--
--
--
Hydrogen isotope ratios of lacustrine sedimentary n-alkanes as proxies of tropical African hydrology insights from a calibration transect across Cameroon
Hydrogen isotope values (delta D) of sedimentary aquatic and terrestrial lipid biomarkers, originating from algae, bacteria, and leaf wax, have been used to record isotopic properties of ancient source water (i.e., precipitation and/or lake water) in several mid-and high-latitude lacustrine environments. In the tropics, however, where both processes associated with isotope fractionation in the hydrologic system and vegetation strongly differ from those at higher latitudes, calibration studies for this proxy are not yet available. To close this gap of knowledge, we sampled surface sediments from 11 lakes in Cameroon to identify those hydro-climatological processes and physiological factors that determine the hydrogen isotopic composition of aquatic and terrestrial lipid biomarkers. Here we present a robust framework for the application of compound-specific hydrogen isotopes in tropical Africa. Our results show that the delta D values of the aquatic lipid biomarker n-C(17) alkane were not correlated with the delta D values of lake water. Carbon isotope measurements indicate that the n-C(17) alkane was derived from multiple source organisms that used different hydrogen pools for biosynthesis. We demonstrate that the delta D values of the n-C(29) alkane were correlated with the delta D values of surface water (i.e., river water and groundwater), which, on large spatial scales, reflect the isotopic composition of mean annual precipitation. Such a relationship has been observed at higher latitudes, supporting the robustness of the leaf-wax lipid delta D proxy on a hemispheric spatial scale. In contrast, the delta D values of the n-C(31) alkane did not show such a relationship but instead were correlated with the evaporative lake water delta D values. This result suggests distinct water sources for both leaf-wax lipids, most likely originating from two different groups of plants. These new findings have important implications for the interpretation of long-chain n-alkane delta D records from ancient lake sediments. In particular, a robust interpretation of palaeohydrological data requires knowledge of the vegetation in the catchment area as different plants may utilise different water sources. Our results also suggest that the combination of carbon and hydrogen isotopes does help to differentiate between the metabolic pathway and/or growth form of organisms and therefore, the source of hydrogen used during lipid biosynthesis.
Geochimica et cosmochimica acta : journal of the Geochemical Society and the Meteoritical Society
10.1016/j.gca.2011.11.039
0016-7037
wos:2011-2013
WOS:000299539400006
Garcin, Y (reprint author), Univ Potsdam, DFG Leibniz Ctr Surface Proc & Climate Studies, Inst Erd & Umweltwissensch, Karl Liebknecht Str 24,Haus 27, D-14476 Potsdam, Germany., yannickgarcin@yahoo.fr
German Science Foundation (DFG) [GA-1629/1-1]; DFG [SA-1889/1-1]; DFG
Leibniz Center for Surface Process and Climate Studies at Potsdam
University; MPI-BGC
Yannick Garcin
Valerie F. Schwab
Gerd Gleixner
Ansgar Kahmen
Gilbert Todou
Olivier Sene
Jean-Michel Onana
Gaston Achoundong
Dirk Sachse
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
37526
2014
2014
eng
482
500
19
142
article
Elsevier
Oxford
1
--
--
--
Reconstructing C-3 and C-4 vegetation cover using n-alkane carbon isotope ratios in recent lake sediments from Cameroon, Western Central Africa
Trees and shrubs in tropical Africa use the C-3 cycle as a carbon fixation pathway during photosynthesis, while grasses and sedges mostly use the C-4 cycle. Leaf-wax lipids from sedimentary archives such as the long-chain n-alkanes (e.g., n-C-27 to n-C-33) inherit carbon isotope ratios that are representative of the carbon fixation pathway. Therefore, n-alkane delta C-13 values are often used to reconstruct past C-3/C-4 composition of vegetation, assuming that the relative proportions of C-3 and C-4 leaf waxes reflect the relative proportions of C-3 and C-4 plants. We have compared the delta C-13 values of n-alkanes from modern C-3 and C-4 plants with previously published values from recent lake sediments and provide a framework for estimating the fractional contribution (areal-based) of C-3 vegetation cover (f(C3)) represented by these sedimentary archives. Samples were collected in Cameroon, across a latitudinal transect that accommodates a wide range of climate zones and vegetation types, as reflected in the progressive northward replacement of C-3-dominated rain forest by C-4-dominated savanna. The C-3 plants analysed were characterised by substantially higher abundances of n-C-29 alkanes and by substantially lower abundances of n-C-33 alkanes than the C-4 plants. Furthermore, the sedimentary delta C-13 values of n-C-29 and n-C-31 alkanes from recent lake sediments in Cameroon (-37.4%) to 26.5%) were generally within the range of delta C-13 values for C-3 plants, even when from sites where C-4 plants dominated the catchment vegetation. In such cases simple linear mixing models fail to accurately reconstruct the relative proportions of C-3 and C-4 vegetation cover when using the delta C-13 values of sedimentary n-alkanes, overestimating the proportion of C-3 vegetation, likely as a consequence of the differences in plant wax production, preservation, transport, and/or deposition between C-3 and C-4 plants. We therefore tested a set of non-linear binary mixing models using delta C-13 values from both C-3 and C-4 vegetation as end-members. The non-linear models included a sigmoid function (sine-squared) that describes small variations in the f(C3) values as the minimum and maximum delta C-13 values are approached, and a hyperbolic function that takes into account the differences between C-3 and C-4 plants discussed above. Model fitting and the estimation of uncertainties were completed using the Monte Carlo algorithm and can be improved by future data addition. Models that provided the best fit with the observed delta C-13 values of sedimentary n-alkanes were either hyperbolic functions or a combination of hyperbolic and sine-squared functions. Such non-linear models may be used to convert delta C-13 measurements on sedimentary n-alkanes directly into reconstructions of C-3 vegetation cover. (C) 2014 Elsevier Ltd. All rights reserved.
Geochimica et cosmochimica acta : journal of the Geochemical Society and the Meteoritical Society
10.1016/j.gca.2014.07.004
0016-7037
1872-9533
wos:2014
WOS:000342622400031
Garcin, Y (reprint author), Univ Potsdam, Inst Erd & Umweltwissensch, DFG Leibniz Ctr Surface Proc & Climate Studies, Karl Liebknecht Str 24,Haus 27, D-14476 Potsdam, Germany., yannickgarcin@yahoo.fr
German Science Foundation (DFG) [GA-1629/1-1, GA-1629/1-2]; DFG
Emmy-Noether Programme [SA-1889/1-1]; DFG Leibniz Center for Surface
Process and Climate Studies at Potsdam University; MPI-BGC Jena;
Yannick Garcin
Enno Schefuss
Valerie F. Schwab
Vincent Garreta
Gerd Gleixner
Annie Vincens
Gilbert Todou
Olivier Sene
Jean-Michel Onana
Gaston Achoundong
Dirk Sachse
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
38488
2015
2015
eng
35
49
15
88
article
Elsevier
Oxford
1
--
--
--
Dinosterol delta D values in stratified tropical lakes (Cameroon) are affected by eutrophication
In freshwater settings, dinosterol (4 alpha,23,24-trimethyl-5 alpha-cholest-22E-en-3 beta-ol) is produced primarily by dinoflagellates, which encompass various species including autotrophs, mixotrophs and heterotrophs. Due to its source specificity and occurrence in lake and marine sediments, its presence and hydrogen isotopic composition (delta D) should be valuable proxies for paleohydrological reconstruction. However, because the purity required for hydrogen isotope measurements is difficult to achieve using standard wet chemical purification methods, their potential as a paleohydrological proxy is rarely exploited. In this study, we tested delta D values of dinosterol in both particulate organic matter (POM) and sediments of stratified tropical freshwater lakes (from Cameroon) as a paleohydrological proxy, the lakes being characterized by variable degrees of eutrophication. In POM and sediment samples, the delta D values of dinosterol correlated with lake water delta D values, confirming a first order influence of source water delta D values. However, we observed that sedimentary dinosterol was D enriched from ca. 19 to 54% compared with POM dinosterol. The enrichment correlated with lake water column conditions, mainly the redox potential at the oxic-anoxic interface (E-h OAI). The observations suggest that paleohydrologic reconstruction from delta D values of dinosterol in the sediments of stratified tropical lakes ought to be sensitive to the depositional environment, in addition to lake water delta D values, with more positive dinosterol delta values potentially reflecting increasing lake eutrophication. Furthermore, in lake sediments, the concentration of partially reduced vs. non-reduced C-34 botryococcenes, stanols vs. stenols, and bacterial (diploptene, diplopterol and beta beta-bishomohopanol) vs. planktonic/terrestrial lipids (cholesterol, campesterol and dinosterol) correlated with Eh OAI. We suggest using such molecular proxies for lake redox conditions in combination with dinosterol delta D values to evaluate the effect of lake trophic status on sedimentary dinosterol delta D values, as a basis for accurately reconstructing tropical lake water delta D values. (C) 2015 Elsevier Ltd. All rights reserved.
Organic geochemistry : the international journal for rapid publication of current research in organic geochemistry and biochemistry
10.1016/j.orggeochem.2015.08.003
0146-6380
wos:2015
WOS:000363272900004
Schwab, VF (reprint author), Univ Jena, Inst Inorgan & Analyt Chem, D-07745 Jena, Germany., vf.schwab@uni-jena.de
MPI-BGC Jena; German Science Foundation (DFG) [GA-1629/1-1,
GA-1629/1-2]; DFG Emmy - Noether Programme [SA-1889/1-1]; DFG Leibniz
Centre for Surface Process and Climate Studies at Potsdam University
Valerie F. Schwab
Yannick Garcin
Dirk Sachse
Gilbert Todou
Olivier Sene
Jean-Michel Onana
Gaston Achoundong
Gerd Gleixner
eng
uncontrolled
Hydrogen
eng
uncontrolled
Isotope
eng
uncontrolled
Fractionation
eng
uncontrolled
Biomarkers
eng
uncontrolled
Dinosterol
eng
uncontrolled
Lake
eng
uncontrolled
Redox potential
eng
uncontrolled
Paleoenvironmental
eng
uncontrolled
Proxy
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
39419
2015
2015
eng
99
109
11
78
article
Elsevier
Oxford
1
--
--
--
Effect of aridity on delta C-13 and delta D values of C-3 plant- and C-4 graminoid-derived leaf wax lipids from soils along an environmental gradient in Cameroon (Western Central Africa)
The observation that the hydrogen isotope composition (delta D) of leaf wax lipids is determined mainly by precipitation delta D values, has resulted in the application of these biomarkers to reconstruct paleoclimate from geological records. However, because the delta D values of leaf wax lipids are additionally affected by vegetation type and ecosystem evapotranspiration, paleoclimatic reconstruction remains at best semi-quantitative. Here, we used published results for the carbon isotope composition (delta C-13) of n-alkanes in common plants along a latitudinal gradient in C-3/C-4 vegetation and relative humidity in Cameroon and demonstrated that pentacyclic triterpene methyl ethers (PTMEs) and n-C-29 and n-C-31 in the same soil, derived mainly from C-4 graminoids (e.g. grass) and C-3 plants (e.g. trees and shrubs), respectively. We found that the delta D values of soil n-C-27, n-C29 and n-C-31, and PTMEs correlated significantly with surface water delta D values, supporting previous observations that leaf wax lipid delta D values are an effective proxy for reconstructing precipitation delta D values even if plant types changed significantly. The apparent fractionation (epsilon(app)) between leaf wax lipid and precipitation delta D values remained relatively constant for C-3-derived long chain n-alkanes, whereas eapp of C-4-derived PTMEs decreased by 20 parts per thousand along the latitudinal gradient encompassing a relative humidity range from 80% to 45%. Our results indicate that PTME delta D values derived from C-4 graminoids may be a more reliable paleo-ecohydrological proxy for ecosystem evapotranspiration within tropical and sub-tropical Africa than n-alkane delta D values, the latter being a better proxy for surface water delta D values. We suggest that vegetation changes associated with different plant water sources and/or difference in timing of leaf wax synthesis between C-3 trees of the transitional class and C-3 shrubs of the savanna resulted in a D depletion in soil long chain n-alkanes, thereby counteracting the effect of evapotranspiration D enrichment along the gradient. In contrast, evaporative D enrichment of leaf and soil water was significant enough to be recorded in the delta D values of PTMEs derived from C-4 graminoids, likely because PTMEs recorded the hydrogen isotopic composition of the same vegetation type.
Organic geochemistry : the international journal for rapid publication of current research in organic geochemistry and biochemistry
10.1016/j.orggeochem.2014.09.007
0146-6380
wos:2015
WOS:000346389700010
Schwab, VF (reprint author), Univ Jena, Inst Inorgan & Analyt Chem, D-07745 Jena, Germany., vf.schwab@uni-jena.de
MPI-BGC Jena; German Science Foundation (DFG) [GA-1629/1-1,
GA-1629/1-2]; DFG Emmy-Noether Programme [SA-1889/1-1]; DFG Leibniz
Center for Surface Process and Climate Studies at Potsdam University
Valerie F. Schwab
Yannick Garcin
Dirk Sachse
Gilbert Todou
Olivier Sene
Jean-Michel Onana
Gaston Achoundong
Gerd Gleixner
eng
uncontrolled
Evapotranspiration
eng
uncontrolled
D-enrichment
eng
uncontrolled
Pentacyclic triterpene methyl ethers
eng
uncontrolled
PTMEs
eng
uncontrolled
n-Alkane
eng
uncontrolled
Compound-specific isotope
eng
uncontrolled
Paleo
eng
uncontrolled
Climate
eng
uncontrolled
Proxy
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
46262
2017
2017
eng
1
12
12
174
review
Elsevier
Oxford
1
--
--
--
Gradual or abrupt? Changes in water source of Lake Turkana (Kenya) during the African Humid Period inferred from Sr isotope ratios
Quaternary science reviews : the international multidisciplinary research and review journal
10.1016/j.quascirev.2017.08.010
0277-3791
wos:2017
WOS:000413385100001
van der Lubbe, HJL (reprint author), Vrije Univ Amsterdam, Fac Sci Geol & Geochem, De Boelelaan 1085, NL-1081 HV Amsterdam, Netherlands., hj.l.vander.lubbe@vu.nl; jacquelinekn@hotmail.com; annett.junginger@uni-tuebingen.de; yannick.garcin@geo.uni-potsdam.de; j.c.a.joordens@arch.leidenuniv.nl; g.r.davies@vu.nl; ccbeck@hamilton.edu; feibel@rci.rutgers.edu; tcj@d.umn.edu; hubert.vonhof@mpic.de
Netherlands Organisation for Scientific Research (NWO) [824.01.005]; Leakey Foundation
importub
2020-04-20T00:00:01+00:00
filename=package.tar
b2da952afb9afe60dcaf08e08b66ed91
H. J. L. van der Lubbe
J. Krause-Nehring
A. Junginger
Yannick Garcin
J. C. A. Joordens
G. R. Davies
C. Beck
C. S. Feibel
T. C. Johnson
H. B. Vonhof
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
Import
30786
2009
2009
eng
article
1
--
--
--
Late Pleistocene-Holocene rise and collapse of the Lake Suguta, northern Kenya Rift
http://www.sciencedirect.com/science/journal/02773791
10.1016/j.quascirev.2008.12.006
allegro:1991-2014
10105635
Quaternary science reviews. - 28 (2009), 9-10, S. 911 - 925
Yannick Garcin
Annett Junginger
Daniel Melnick
Daniel O. Olago
Manfred Strecker
Martin H. Trauth
Institut für Geowissenschaften
Referiert
55440
2017
2017
eng
58
69
12
459
article
Elsevier
Amsterdam
1
2017-11-30
2017-12-16
--
Short-lived increase in erosion during the African Humid Period
The African Humid Period (AHP) between similar to 15 and 5.5 cal. kyr BP caused major environmental change in East Africa, including filling of the Suguta Valley in the northern Kenya Rift with an extensive (similar to 2150 km(2)), deep (similar to 300 m) lake. Interfingering fluvio-lacustrine deposits of the Baragoi paleo-delta provide insights into the lake-level history and how erosion rates changed during this time, as revealed by delta-volume estimates and the concentration of cosmogenic Be-10 in fluvial sand. Erosion rates derived from delta-volume estimates range from 0.019 to 0.03 mm yr(-1). Be-10-derived paleo-erosion rates at similar to 11.8 cal. kyr BP ranged from 0.035 to 0.086 mm yr(-1), and were 2.7 to 6.6 times faster than at present. In contrast, at similar to 8.7 cal. kyr BP, erosion rates were only 1.8 times faster than at present. Because Be-10-derived erosion rates integrate over several millennia; we modeled the erosion-rate history that best explains the 10Be data using established non-linear equations that describe in situ cosmogenic isotope production and decay. Two models with different temporal constraints (15-6.7 and 12-6.7 kyr) suggest erosion rates that were 25 to 300 times higher than the initial erosion rate (pre-delta formation). That pulse of high erosion rates was short (similar to 4 kyr or less) and must have been followed by a rapid decrease in rates while climate remained humid to reach the modern Be-10-based erosion rate of,similar to 0.013 mm yr(-1). Our simulations also flag the two highest Be-10-derived erosion rates at 11.8 kyr BP related to nonuniform catchment erosion. These changes in erosion rates and processes during the AHP may reflect a strong increase in precipitation, runoff, and erosivity at the arid-to-humid transition either at 15 or similar to 12 cal. kyr BP, before the landscape stabilized again, possibly due to increased soil production and denser vegetation.
Earth & planetary science letters
evidence from the northern Kenya Rift
10.1016/j.epsl.2016.11.017
0012-821X
1385-013X
wos:2017
WOS:000393006500006
Garcin, Y (reprint author), Univ Potsdam, Inst Erd & Umweltwissensch, Karl Liebknecht Str 24,Haus 27, D-14476 Potsdam, Germany., yannickgarcin@yahoo.fr
2022-07-01T11:06:30+00:00
sword
importub
filename=package.tar
df3e5e87b55eb9ba8510628e9891626f
Garcin, Yannick
Yannick Garcin
Taylor F. Schildgen
Veronica Torres Acosta
Daniel Melnick
Julien Guillemoteau
Jane Willenbring
Manfred Strecker
eng
uncontrolled
northern Kenya Rift
eng
uncontrolled
Baragoi
eng
uncontrolled
paleo-delta
eng
uncontrolled
African Humid Period
eng
uncontrolled
erosion
eng
uncontrolled
Be-10
Geowissenschaften
Institut für Geowissenschaften
Referiert
Import
46608
2017
2017
eng
1431
1454
24
209
article
Oxford Univ. Press
Oxford
1
--
--
--
Slip along the Sultanhani Fault in Central Anatolia from deformed Pleistocene shorelines of palaeo-lake Konya and implications for seismic hazards in low-strain regions
Central Anatolia is a low-relief, high-elevation region where decadal-scale deformation rates estimated from space geodesy suggest low strain rates within a stiff microplate. However, numerous Quaternary faults have been mapped within this low-strain region and estimating their slip rate and seismic potential is important for hazard assessments in an area of increasing infrastructural development. Here we focus on the Sultanhani Fault (SF), which constitutes an integral part of the Eskisehir-Cihanbeyli Fault System, and use deformed maximum highstand shorelines of palaeo-lake Konya to estimate tectonic slip rates at millennial scale. Some of these shorelines were previously interpreted as fault scarps, but we provide conclusive evidence for their erosional origin. We found that shoreline-angle elevations estimated from differential GPS profiles record vertical displacements of 10.2 m across the SF. New radiocarbon ages of lacustrine molluscs suggest 22.4 m of relative lake-level fall between 22.1 +/- 0.3 and 21.7 +/- 0.4 cal. kaBP, constraining the timing of abrupt abandonment of the highstand shoreline. Models of lithospheric rebound associated with regressions of the Tuz Golu and Konya palaeolakes predict only similar to 1 m of regional-scale uplift across the Konya Basin. Dislocation models of displaced shorelines suggest fault-slip rates of 1.5 and 1.8 mm yr(-1) for planar and listric fault geometries, respectively, providing reasonable results for the latter. We found fault scarps in the Nasuhpinar mudflat that likely represent the most recent ground-breaking rupture of the SF, with an average vertical displacement of 1.2 +/- 0.5 m estimated from 54 topographic profiles, equivalent to a M similar to 6.5-6.9 earthquake based on empirical scaling laws. If such events were characteristic during the ultimate 21 ka, a relatively short recurrence time of similar to 800-900 yr would be needed to account for the millennial slip rate. Alternatively, the fault scarp at Nasuhpinar might represent a larger earthquake requiring more frequent smaller events to account for the millennial rate. The relatively fast slip rate of the SF over the past 21 ka is unlikely to have persisted over longer timescales and might reflect spatiotemporal variations in deformation rates within kinematically-linked fault systems within Central Anatolia, or a transient perturbation to the local stress field or fault strength. Such perturbation might have been related to climatically controlled changes in surface and near-surface loads and by interactions among the different tectonic processes that have been proposed to drive the overall slow uplift and associated extension in the Central Anatolian Plateau.
Geophysical journal international
10.1093/gji/ggx074
0956-540X
1365-246X
wos:2017
WOS:000408374300008
Melnick, D (reprint author), Univ Potsdam, Inst Erd & Umweltwissensch, Potsdam, Germany.; Melnick, D (reprint author), Univ Austral Chile, Inst Ciencias Tierra, Valdivia, Chile., melnick@geo.uni-potsdam.de
VAMP (Vertical Anatolian Movements Project) - DFG Leibniz Center for Surface Process and Climate studies at Potsdam University; TopoEurope initiative of the European Science Foundation (ESF) through the German Science Foundation (DFG) [STR 373/25-1]; DFG [ME-3157/4-2, STR-373/30-1, GA-1629/2-2]; TUBITAK [107Y333]; German Aerospace Center (DLR) [IDEM GEOL01119]
importub
2020-04-20T02:53:01+00:00
filename=package.tar
233b54c98b8e0a6aaa80825a06fabe51
Daniel Melnick
Cengiz Yildirim
Christian Hillemann
Yannick Garcin
T. Attila Ciner
Marta Perez-Gussinye
Manfred Strecker
eng
uncontrolled
Seismic cycle
eng
uncontrolled
Geomorphology
eng
uncontrolled
Continental neotectonics
eng
uncontrolled
Earthquake hazards
eng
uncontrolled
Tectonics and climatic interactions
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
Import
46355
2017
2017
eng
528
528
1
474
other
Elsevier
Amsterdam
1
--
--
--
Short-lived increase in erosion during the African Humid Period: Evidence from the northern Kenya Rift (vol 759, pg 58, 2017)
Earth & planetary science letters
10.1016/j.epsl.2017.07.027
0012-821X
1385-013X
wos:2017
WOS:000409150600053
Garcin, Y (reprint author), Univ Potsdam, Inst Erd & Umweltwissensch, Karl Liebknecht Str 24,Haus 27, D-14476 Potsdam, Germany., yannickgarcin@yahoo.fr
importub
2020-04-20T00:47:01+00:00
filename=package.tar
15de0d13c6a8d8bbfc1a57dd97f55398
Yannick Garcin
Veronica Torres Acosta
Daniel Melnick
Julien Guillemoteau
Jane Willenbring
Manfred Strecker
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
Import
35331
2013
2013
eng
691
714
24
5
22
article
Tübitak
Ankara
1
--
--
--
Plio-Quaternary extensional tectonics of the Central Anatolian Plateau a case study from the Tuz Golu Basin, Turkey
The Tuz Golu Basin is the largest sedimentary depression located at the center of the Central Anatolian Plateau, an extensive, low-relief region with elevations of ca. 1 km located between the Pontide and Tauride mountains. Presently, the basin morphology and sedimentation processes are mainly controlled by the extensional Tuz Golu Fault Zone in the east and the transtensional Inonu-Eskisehir Fault System in the west. The purpose of this study is to contribute to the understanding of the Plio-Quaternary deformation history and to refine the timing of the latest extensional phase of the Tuz Golu Basin. Field observations, kinematic analyses, interpretations of seismic reflection lines, and Ar-40/Ar-39 dating of a key ignimbrite layer suggest that a regional phase of NNW-SSE to NE-SW contraction ended by 6.81 +/- 0.24 Ma and was followed by N-S to NE-SW extension during the Pliocene-Quaternary periods. Based on sedimentological and chronostratigraphic markers, the average vertical displacement rates over the past 5 or 3 Ma with respect to the central part of Tuz Golu Lake are 0.03 to 0.05 mm/year for the fault system at the western flank of the basin and 0.08 to 0.13 mm/year at the eastern flank. Paleo-shorelines of the Tuz Golu Lake, vestiges of higher lake levels related to Quaternary climate change, are important strain markers and were formed during Last Glacial Maximum conditions as indicated by a radiocarbon age of 21.8 +/- 0.4 ka BP obtained from a stromatolitic crust. Geomorphic observations and deformed lacustrine shorelines suggest that the main strand of the Tuz Golu Fault Zone straddling the foothills of the Sereflikochisar-Aksaray range has not been active during the Holocene. Instead, deformation appears to have migrated towards the interior of the basin along an offshore fault that runs immediately west of Sereflikochisar Peninsula. This basinward migration of deformation is probably associated with various processes acting at the lithospheric scale, such as plateau uplift and/or microplate extrusion.
Turkish journal of earth sciences = Türk yerbilimleri dergisi
10.3906/yer-1210-5
1300-0985
wos:2011-2013
WOS:000323605600001
Ozsayin, E (reprint author), Hacettepe Univ, Dept Geol Engn, TR-06800 Ankara, Turkey., eozsayin@hacettepe.edu.tr
TOPOEUROPE initiative of the European Science Foundation; TUBITAK
[107Y333]; German Science Foundation [STR373/20-1, STR373/25-1];
Netherlands Organization for Scientific Research (NWO)
Erman Ozsayin
T. Attila Ciner
F. Bora Rojay
R. Kadir Dirik
Daniel Melnick
David Fernandez-Blanco
Giovanni Bertotti
Taylor F. Schildgen
Yannick Garcin
Manfred Strecker
Masafumi Sudo
eng
uncontrolled
Central Anatolia
eng
uncontrolled
Tuz Golu Basin
eng
uncontrolled
orogenic plateau evolution
eng
uncontrolled
extensional tectonics
eng
uncontrolled
kinematic analysis
eng
uncontrolled
lake shoreline
Institut für Geowissenschaften
Referiert
Open Access
Institut für Erd- und Umweltwissenschaften
35901
2012
2012
eng
335
346
12
10
331
article
Elsevier
Amsterdam
1
--
--
--
Steady rifting in northern Kenya inferred from deformed Holocene lake shorelines of the Suguta and Turkana basins
A comparison of deformation rates in active rifts over different temporal scales may help to decipher variations in their structural evolution, controlling mechanisms, and evolution of sedimentary environments through time. Here we use deformed lake shorelines in the Suguta and Turkana basins in northern Kenya as strain markers to estimate deformation rates at the 10(3)-10(4) yr time scale and compare them with rates spanning 10(1)-10(7) yr. Both basins are internally drained today, but until 7 to 5 kyr lake levels were 300 and 100 m higher, respectively, maintained by the elevation of overflow sills connecting them with the Nile drainage. Protracted high lake levels resulted in formation of a maximum highstand shoreline - a distinct geomorphic feature virtually continuous for several tens of kilometers. We surveyed the elevation of this geomorphic marker at 45 sites along >100 km of the rift, and use the overflow sills as vertical datum. Thin-shell elastic and thermomechanical models for this region predict up to similar to 10 m of rapid isostatic rebound associated with lake-level falls lasting until similar to 2 kyr ago. Holocene cumulative throw rates along four rift-normal profiles are 6.8-8.5 mm/yr, or 7.5-9.6 mm/yr if isostatic rebound is considered. Assuming fault dips of 55-65, inferred from seismic reflection profiles, we obtained extension rates of 3.2-6 mm/yr (including uncertainties in field measurements, fault dips, and ages), or 3.5-6.7 mm/yr considering rebound. Our estimates are consistent, within uncertainties, with extension rates of 4-5.1 mm/yr predicted by a modern plate-kinematic model and plate reconstructions since 3.2 Myr. The Holocene strain rate of 10(-15) s(-1) is similar to estimates on the similar to 10(6) yr scale, but over an order of magnitude higher than on the similar to 10(7) yr scale. This is coherent with continuous localization and narrowing of the plate boundary, implying that the lithospheric blocks limiting the Kenya Rift are relatively rigid. Increasing strain rate under steady extension rate suggests that, as the magnitude of extension and crustal thinning increases, the role of regional processes such as weakening by volcanism becomes dominant over far-field plate tectonics controlling the breakup process and the transition from continental rifting to oceanic spreading.
Earth & planetary science letters
10.1016/j.epsl.2012.03.007
0012-821X
wos:2011-2013
WOS:000306030500031
Melnick, D (reprint author), Univ Potsdam, Inst Erd & Umweltwissensch, D-14476 Potsdam, Germany., melnick@geo.uni-potsdam.de
German Research Foundation (DFG) [GRK1364, TR419/6-1, STR373/16-1];
Alexander von Humboldt fellowship; ISIS [156]
Daniel Melnick
Yannick Garcin
Javier Quinteros
Manfred Strecker
Daniel Olago
Jean-Jacques Tiercelin
eng
uncontrolled
continental rifting
eng
uncontrolled
East Africa
eng
uncontrolled
lake shorelines
eng
uncontrolled
Holocene extension
eng
uncontrolled
isostatic rebound
Institut für Physik und Astronomie
Referiert
35900
2012
2012
eng
322
334
13
331
article
Elsevier
Amsterdam
1
--
--
--
East African mid-Holocene wet-dry transition recorded in palaeo-shorelines of Lake Turkana, northern Kenya Rift
The 'wet' early to mid-Holocene of tropical Africa, with its enhanced monsoon, ended with an abrupt shift toward drier conditions and was ultimately replaced by a drier climate that has persisted until the present day. The forcing mechanisms, the timing, and the spatial extent of this major climatic transition are not well understood and remain the subject of ongoing research. We have used a detailed palaeo-shoreline record from Lake Turkana (Kenya) to decipher and characterise this marked climatic transition in East Africa. We present a high-precision survey of well-preserved palaeo-shorelines, new radiocarbon ages from shoreline deposits, and oxygen-isotope measurements on freshwater mollusk shells to elucidate the Holocene moisture history from former lake water-levels in this climatically sensitive region. In combination with previously published data our study shows that during the early Holocene the water-level in Lake Turkana was high and the lake overflowed temporarily into the White Nile drainage system. During the mid-Holocene (similar to 5270 +/- 300 cal. yr BP), however, the lake water-level fell by similar to 50 m, coeval with major episodes of aridity on the African continent. A comparison between palaeo-hydrological and archaeological data from the Turkana Basin suggests that the mid-Holocene climatic transition was associated with fundamental changes in prehistoric cultures, highlighting the significance of natural climate variability and associated periods of protracted drought as major environmental stress factors affecting human occupation in the East African Rift System. (
Earth & planetary science letters
10.1016/j.epsl.2012.03.016
0012-821X
wos:2011-2013
WOS:000306030500030
Garcin, Y (reprint author), Univ Potsdam, Inst Erd & Umweltwissensch, D-14476 Potsdam, Germany., yannickgarcin@yahoo.fr
German Research Foundation (DFG) [GRK1364, TR419/6-1, STR373/16-1];
Alexander von Humboldt Research Fellowship; INSU-CNRS-ECLIPSE
Yannick Garcin
Daniel Melnick
Manfred Strecker
Daniel Olago
Jean-Jacques Tiercelin
eng
uncontrolled
East African Rift System
eng
uncontrolled
Lake Turkana
eng
uncontrolled
Palaeo-shorelines
eng
uncontrolled
African Humid Period
eng
uncontrolled
Holocene
eng
uncontrolled
Tectonic deformation
Institut für Geowissenschaften
Referiert
53233
2018
2018
eng
3261
3266
6
13
115
article
National Acad. of Sciences
Washington
1
2018-02-26
2018-02-26
--
Early anthropogenic impact on Western Central African rainforests 2,600 y ago
A potential human footprint on Western Central African rainforests before the Common Era has become the focus of an ongoing controversy. Between 3,000 y ago and 2,000 y ago, regional pollen sequences indicate a replacement of mature rainforests by a forest-savannah mosaic including pioneer trees. Although some studies suggested an anthropogenic influence on this forest fragmentation, current interpretations based on pollen data attribute the "rainforest crisis" to climate change toward a drier, more seasonal climate. A rigorous test of this hypothesis, however, requires climate proxies independent of vegetation changes. Here we resolve this controversy through a continuous 10,500-y record of both vegetation and hydrological changes from Lake Barombi in Southwest Cameroon based on changes in carbon and hydrogen isotope compositions of plant waxes. delta C-13-inferred vegetation changes confirm a prominent and abrupt appearance of C-4 plants in the Lake Barombi catchment, at 2,600 calendar years before AD 1950 (cal y BP), followed by an equally sudden return to rainforest vegetation at 2,020 cal y BP. delta D values from the same plant wax compounds, however, show no simultaneous hydrological change. Based on the combination of these data with a comprehensive regional archaeological database we provide evidence that humans triggered the rainforest fragmentation 2,600 y ago. Our findings suggest that technological developments, including agricultural practices and iron metallurgy, possibly related to the large-scale Bantu expansion, significantly impacted the ecosystems before the Common Era.
Proceedings of the National Academy of Sciences of the United States of America
10.1073/pnas.1715336115
29483260
0027-8424
wos:2018
WOS:000428382400038
Garcin, Y (reprint author), Univ Potsdam, Inst Earth & Environm Sci, D-14476 Potsdam, Germany., yannickgarcin@yahoo.fr
ISIS-888 Project; French National Research Institute for Sustainable Development (IRD), its local office in Yaounde; LMI DYCOFAC; Deutsche Forschungsgemeinschaft (DFG)German Research Foundation (DFG) [GA1629/2]; Ministry of Science, Research, and Culture des Landes Brandenburg; Labex OT-Med project; EQUIPEX ASTER-CEREGE project; DFG-Research Center/Cluster of Excellence "The Ocean in the Earth System" at MARUM-Center for Marine Environmental Sciences
2021-12-21T10:45:24+00:00
sword
importub
filename=package.tar
94bd409798e436a57c338e3edc1ffa73
Garcin, Yannick
false
true
Yannick Garcin
Pierre Deschamps
Guillemette Menot
Geoffroy de Saulieu
Enno Schefuss
David Sebag
Lydie M. Dupont
Richard Oslisly
Brian Brademann
Kevin G. Mbusnum
Jean-Michel Onana
Andrew A. Ako
Laura Saskia Epp
Rik Tjallingii
Manfred Strecker
Achim Brauer
Dirk Sachse
eng
uncontrolled
Western Central Africa
eng
uncontrolled
late Holocene
eng
uncontrolled
rainforest crisis
eng
uncontrolled
paleohydrology
eng
uncontrolled
human activity
Historische Geografie
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
Import
Bronze Open-Access
52453
2018
2018
eng
E6674
E6675
2
29
115
other
National Acad. of Sciences
Washington
1
2018-07-03
2018-07-03
--
No evidence for climate variability during the late Holocene rainforest crisis in Western Central Africa REPLY
Proceedings of the National Academy of Sciences of the United States of America
10.1073/pnas.1808481115
29970424
0027-8424
wos:2018
WOS:000438892600002
Garcin, Y (reprint author), Univ Potsdam, Inst Earth & Environm Sci, D-14476 Potsdam, Germany., yannickgarcin@yahoo.fr
2021-10-29T07:41:10+00:00
sword
importub
filename=package.tar
e1d197ff5d851aeb41496917f2df8eb9
Garcin, Yannick
false
true
Yannick Garcin
Pierre Deschamps
Guillemette Menot
Geoffroy de Saulieu
Enno Schefuss
David Sebag
Lydie M. Dupont
Richard Oslisly
Brian Brademann
Kevin G. Mbusnum
Jean-Michel Onana
Andrew A. Ako
Laura Saskia Epp
Rik Tjallingii
Manfred Strecker
Achim Brauer
Dirk Sachse
Geowissenschaften
Institut für Geowissenschaften
Referiert
Import
Bronze Open-Access
52879
2018
2018
eng
E4735
E4736
2
21
115
other
National Acad. of Sciences
Washington
1
2018-05-22
2018-05-08
--
Human activity is the most probable trigger of the late Holocene rainforest crisis in Western Central Africa Reply
Proceedings of the National Academy of Sciences of the United States of America
10.1073/pnas.1805582115
29739892
0027-8424
wos:2018
WOS:000432663000002
Garcin, Y (reprint author), Univ Potsdam, Inst Earth & Environm Sci, D-14476 Potsdam, Germany., yannickgarcin@yahoo.fr
2021-11-30T10:22:20+00:00
sword
importub
filename=package.tar
eced8231f94f3a74f1a240d016d93b39
false
true
Yannick Garcin
Pierre Deschamps
Guillemette Menot
Geoffroy de Saulieu
Enno Schefuss
David Sebag
Lydie M. Dupont
Richard Oslisly
Brian Brademann
Kevin G. Mbusnum
Jean-Michel Onana
Andrew A. Ako
Laura Saskia Epp
Rik Tjallingii
Manfred Strecker
Achim Brauer
Dirk Sachse
Geowissenschaften
Institut für Geowissenschaften
Referiert
Import
Bronze Open-Access