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  - Calitri, Francesca
A1  - Sommer, Michael
A1  - Norton, Kevin
A1  - Temme, Arnaud
A1  - Brandova, Dagmar
A1  - Portes, Raquel
A1  - Christl, Marcus
A1  - Ketterer, Mike E.
A1  - Egli, Markus
T1  - Tracing the temporal evolution of soil redistribution rates in an agricultural landscape using Pu239+240 and Be-10
JF  - Earth surface processes and landforms : the journal of the British Geomorphological Research Group
N2  - Two principal groups of processes shape mass fluxes from and into a soil: vertical profile development and lateral soil redistribution. Periods having predominantly progressive soil forming processes (soil profile development) alternate with periods having predominantly regressive processes (erosion). As a result, short‐term soil redistribution – years to decades – can differ substantially from long‐term soil redistribution; i.e. centuries to millennia. However, the quantification of these processes is difficult and consequently their rates are poorly understood. To assess the competing roles of erosion and deposition we determined short‐ and long‐term soil redistribution rates in a formerly glaciated area of the Uckermark, northeast Germany. We compared short‐term erosion or accumulation rates using plutonium‐239 and ‐240 (239+240Pu) and long‐term rates using both in situ and meteoric cosmogenic beryllium‐10 (10Be). Three characteristic process domains have been analysed in detail: a flat landscape position having no erosion/deposition, an erosion‐dominated mid‐slope, and a deposition‐dominated lower‐slope site. We show that the short‐term mass erosion and accumulation rates are about one order of magnitude higher than long‐term redistribution rates. Both, in situ and meteoric 10Be provide comparable results. Depth functions, and therefore not only an average value of the topsoil, give the most meaningful rates. The long‐term soil redistribution rates were in the range of −2.1 t ha‐1 yr‐1 (erosion) and +0.26 t ha‐1 yr‐1 (accumulation) whereas the short‐term erosion rates indicated strong erosion of up to 25 t ha‐1 yr‐1 and accumulation of 7.6 t ha‐1 yr‐1. Our multi‐isotope method identifies periods of erosion and deposition, confirming the ‘time‐split approach’ of distinct different phases (progressive/regressive) in soil evolution. With such an approach, temporally‐changing processes can be disentangled, which allows the identification of both the dimensions of and the increase in soil erosion due to human influence
KW  - soil erosion
KW  - Be-10
KW  - Pu239+240
KW  - temporal evolution
KW  - moraine landscape
KW  - agricultural soils
Y1  - 2019
U6  - https://doi.org/10.1002/esp.4612
SN  - 0197-9337
SN  - 1096-9837
VL  - 44
IS  - 9
SP  - 1783
EP  - 1798
PB  - Wiley
CY  - Hoboken
ER  -