TY  - JOUR
A1  - Garcin, Yannick
A1  - Schildgen, Taylor F.
A1  - Acosta, Veronica Torres
A1  - Melnick, Daniel
A1  - Guillemoteau, Julien
A1  - Willenbring, Jane
A1  - Strecker, Manfred
T1  - Short-lived increase in erosion during the African Humid Period
BT  - evidence from the northern Kenya Rift
JF  - Earth & planetary science letters
N2  - 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.
KW  - northern Kenya Rift
KW  - Baragoi
KW  - paleo-delta
KW  - African Humid Period
KW  - erosion
KW  - Be-10
Y1  - 2017
U6  - https://doi.org/10.1016/j.epsl.2016.11.017
SN  - 0012-821X
SN  - 1385-013X
VL  - 459
SP  - 58
EP  - 69
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Garcin, Yannick
A1  - Deschamps, Pierre
A1  - Menot, Guillemette
A1  - de Saulieu, Geoffroy
A1  - Schefuss, Enno
A1  - Sebag, David
A1  - Dupont, Lydie M.
A1  - Oslisly, Richard
A1  - Brademann, Brian
A1  - Mbusnum, Kevin G.
A1  - Onana, Jean-Michel
A1  - Ako, Andrew A.
A1  - Epp, Laura Saskia
A1  - Tjallingii, Rik
A1  - Strecker, Manfred
A1  - Brauer, Achim
A1  - Sachse, Dirk
T1  - Early anthropogenic impact on Western Central African rainforests 2,600 y ago
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - 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.
KW  - Western Central Africa
KW  - late Holocene
KW  - rainforest crisis
KW  - paleohydrology
KW  - human activity
Y1  - 2018
U6  - https://doi.org/10.1073/pnas.1715336115
SN  - 0027-8424
VL  - 115
IS  - 13
SP  - 3261
EP  - 3266
PB  - National Acad. of Sciences
CY  - Washington
ER  - 
TY  - GEN
A1  - Garcin, Yannick
A1  - Deschamps, Pierre
A1  - Menot, Guillemette
A1  - de Saulieu, Geoffroy
A1  - Schefuss, Enno
A1  - Sebag, David
A1  - Dupont, Lydie M.
A1  - Oslisly, Richard
A1  - Brademann, Brian
A1  - Mbusnum, Kevin G.
A1  - Onana, Jean-Michel
A1  - Ako, Andrew A.
A1  - Epp, Laura Saskia
A1  - Tjallingii, Rik
A1  - Strecker, Manfred
A1  - Brauer, Achim
A1  - Sachse, Dirk
T1  - Human activity is the most probable trigger of the late Holocene rainforest crisis in Western Central Africa Reply
T2  - Proceedings of the National Academy of Sciences of the United States of America
Y1  - 2018
U6  - https://doi.org/10.1073/pnas.1805582115
SN  - 0027-8424
VL  - 115
IS  - 21
SP  - E4735
EP  - E4736
PB  - National Acad. of Sciences
CY  - Washington
ER  - 
TY  - JOUR
A1  - Diaz, Nathalie
A1  - Dietrich, Fabienne
A1  - Sebag, David
A1  - King, Georgina E.
A1  - Valla, Pierre G.
A1  - Durand, Alain
A1  - Garcin, Yannick
A1  - de Saulie, Geoffroy
A1  - Deschamps, Pierre
A1  - Herman, Frederic
A1  - Verrecchia, Eric P.
T1  - Pedo-sedimentary constituents as paleoenvironmental proxies in the Sudano-Sahelian belt during the Late Quaternary (southwestern Chad Basin)
JF  - Quaternary science reviews : the international multidisciplinary research and review journal
N2  - 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.
KW  - Pedogenic carbonate nodules
KW  - Vertisol genesis
KW  - Soil water balance
KW  - Optical methods
KW  - Radiogenic isotopes
KW  - Quaternary
KW  - Monsoon
KW  - Western Africa
Y1  - 2018
U6  - https://doi.org/10.1016/j.quascirev.2018.05.022
SN  - 0277-3791
VL  - 191
SP  - 348
EP  - 362
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - GEN
A1  - Garcin, Yannick
A1  - Deschamps, Pierre
A1  - Menot, Guillemette
A1  - de Saulieu, Geoffroy
A1  - Schefuss, Enno
A1  - Sebag, David
A1  - Dupont, Lydie M.
A1  - Oslisly, Richard
A1  - Brademann, Brian
A1  - Mbusnum, Kevin G.
A1  - Onana, Jean-Michel
A1  - Ako, Andrew A.
A1  - Epp, Laura Saskia
A1  - Tjallingii, Rik
A1  - Strecker, Manfred
A1  - Brauer, Achim
A1  - Sachse, Dirk
T1  - No evidence for climate variability during the late Holocene rainforest crisis in Western Central Africa REPLY
T2  - Proceedings of the National Academy of Sciences of the United States of America
Y1  - 2018
U6  - https://doi.org/10.1073/pnas.1808481115
SN  - 0027-8424
VL  - 115
IS  - 29
SP  - E6674
EP  - E6675
PB  - National Acad. of Sciences
CY  - Washington
ER  - 
TY  - JOUR
A1  - Sebag, David
A1  - Garcin, Yannick
A1  - Adatte, Thierry
A1  - Deschamps, Pierre
A1  - Menot, Guillemette
A1  - Verrecchia, Eric P.
T1  - Correction for the siderite effect on Rock-Eval parameters
BT  - Application to the sediments of Lake Barombi (southwest Cameroon)
JF  - Organic geochemistry : the international journal for rapid publication of current research in organic geochemistry and biochemistry
N2  - 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.
KW  - Organic geochemistry
KW  - Rock-Eval pyrolysis
KW  - Van Krevelen diagram
KW  - Siderite
KW  - Tropical lake
KW  - Western Central Africa
Y1  - 2018
U6  - https://doi.org/10.1016/j.orggeochem.2018.05.010
SN  - 0146-6380
VL  - 123
SP  - 126
EP  - 135
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Deino, A. L.
A1  - Dommain, René
A1  - Keller, C. B.
A1  - Potts, R.
A1  - Behrensmeyer, A. K.
A1  - Beverly, E. J.
A1  - King, J.
A1  - Heil, C. W.
A1  - Stockhecke, M.
A1  - Brown, E. T.
A1  - Moerman, J.
A1  - deMenocal, P.
A1  - Deocampo, D.
A1  - Garcin, Yannick
A1  - Levin, N. E.
A1  - Lupien, R.
A1  - Owen, R. B.
A1  - Rabideaux, N.
A1  - Russell, J. M.
A1  - Scott, J.
A1  - Riedl, S.
A1  - Brady, K.
A1  - Bright, J.
A1  - Clark, J. B.
A1  - Cohen, A.
A1  - Faith, J. T.
A1  - Noren, A.
A1  - Muiruri, V.
A1  - Renaut, R.
A1  - Rucina, S.
A1  - Uno, K.
T1  - 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
JF  - Quaternary science reviews : the international multidisciplinary research and review journal
N2  - 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.
KW  - Pleistocene
KW  - Paleolimnology
KW  - East Africa
KW  - Sedimentology
KW  - Radiogenic isotopes
KW  - Bayesian modeling
KW  - paleosol
KW  - Tephrostratigraphy
KW  - Magnetostratigraphy
KW  - Kenya Rift
Y1  - 2019
U6  - https://doi.org/10.1016/j.quascirev.2019.05.009
SN  - 0277-3791
VL  - 215
SP  - 213
EP  - 231
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Melnick, Daniel
A1  - Yildirim, Cengiz
A1  - Hillemann, Christian
A1  - Garcin, Yannick
A1  - Ciner, T. Attila
A1  - Perez-Gussinye, Marta
A1  - Strecker, Manfred
T1  - 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
JF  - Geophysical journal international
N2  - 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.
KW  - Seismic cycle
KW  - Geomorphology
KW  - Continental neotectonics
KW  - Earthquake hazards
KW  - Tectonics and climatic interactions
Y1  - 2017
U6  - https://doi.org/10.1093/gji/ggx074
SN  - 0956-540X
SN  - 1365-246X
VL  - 209
SP  - 1431
EP  - 1454
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - GEN
A1  - Garcin, Yannick
A1  - Acosta, Veronica Torres
A1  - Melnick, Daniel
A1  - Guillemoteau, Julien
A1  - Willenbring, Jane
A1  - Strecker, Manfred
T1  - Short-lived increase in erosion during the African Humid Period: Evidence from the northern Kenya Rift (vol 759, pg 58, 2017)
T2  - Earth & planetary science letters
Y1  - 2017
U6  - https://doi.org/10.1016/j.epsl.2017.07.027
SN  - 0012-821X
SN  - 1385-013X
VL  - 474
SP  - 528
EP  - 528
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - van der Lubbe, H. J. L.
A1  - Krause-Nehring, J.
A1  - Junginger, A.
A1  - Garcin, Yannick
A1  - Joordens, J. C. A.
A1  - Davies, G. R.
A1  - Beck, C.
A1  - Feibel, C. S.
A1  - Johnson, T. C.
A1  - Vonhof, H. B.
T1  - Gradual or abrupt? Changes in water source of Lake Turkana (Kenya) during the African Humid Period inferred from Sr isotope ratios
JF  - Quaternary science reviews : the international multidisciplinary research and review journal
Y1  - 2017
U6  - https://doi.org/10.1016/j.quascirev.2017.08.010
SN  - 0277-3791
VL  - 174
SP  - 1
EP  - 12
PB  - Elsevier
CY  - Oxford
ER  -