TY - JOUR
T1 - Active erosion-deposition cycles in the hyperarid Atacama Desert of Northern Chile
AU - Jungers, Matthew C.
AU - Heimsath, Arjun
AU - Amundson, Ronald
AU - Balco, Greg
AU - Shuster, David
AU - Chong, Guillermo
N1 - Funding Information:
This work was supported by an American Chemical Society Petroleum Research Fund grant to AMH and NSF grants 0447441 and 0345936 to RA. We are grateful for the constructive reviews offered by two anonymous reviewers.
Copyright:
Copyright 2013 Elsevier B.V., All rights reserved.
PY - 2013/6
Y1 - 2013/6
N2 - There is significant debate over the rates and types of fluvial activity at the Plio-Pleistocene boundary in the hyperarid Atacama Desert of Chile. To quantify fluvial processes and help resolve this debate, we measure terrestrial cosmogenic nuclide (TCN) (10Be and 21Ne) concentration depth profiles in three settings representing a chronosequence: (1) a late Pliocene alluvial fan representative of major regional deposits, (2) a modern, active channel and (3) an adjacent low terrace inset into the Pliocene alluvium. Late Pliocene deposits that are widely preserved in the region contain TCN profiles consistent with relatively rapid stripping of upland sediment at the Plio-Pleistocene boundary. Deposits inset into these Late Pliocene features record cut and fill cycles that rework sediment throughout the Quaternary. The TCN profile in the modern channel is best explained by sediment aggradation at 2.1mMyr-1 during the last 250,000yr. Similarly, the adjacent low terrace sediments contain TCN concentration profiles consistent with aggradation of 2.0mMyr-1 over a period of 250,000-750,000yr prior to the last 250,000yr of stability. In summary, depth profiles of two TCNs provide constraints on the rates of sediment deposition, sources of sediment and transport history, as well as the subsequent exposure conditions of the sediment following deposition. Our results are consistent with early Quaternary initiation of hyperaridity for the region. During the Quaternary, winter precipitation events experienced at our sites' latitude (24°S) drive active erosion-deposition cycles. The northward migration of the subtropical front during Quaternary glacial cycles may have enhanced precipitation at 24°S, leading to more active fluvial processes during cooler periods.
AB - There is significant debate over the rates and types of fluvial activity at the Plio-Pleistocene boundary in the hyperarid Atacama Desert of Chile. To quantify fluvial processes and help resolve this debate, we measure terrestrial cosmogenic nuclide (TCN) (10Be and 21Ne) concentration depth profiles in three settings representing a chronosequence: (1) a late Pliocene alluvial fan representative of major regional deposits, (2) a modern, active channel and (3) an adjacent low terrace inset into the Pliocene alluvium. Late Pliocene deposits that are widely preserved in the region contain TCN profiles consistent with relatively rapid stripping of upland sediment at the Plio-Pleistocene boundary. Deposits inset into these Late Pliocene features record cut and fill cycles that rework sediment throughout the Quaternary. The TCN profile in the modern channel is best explained by sediment aggradation at 2.1mMyr-1 during the last 250,000yr. Similarly, the adjacent low terrace sediments contain TCN concentration profiles consistent with aggradation of 2.0mMyr-1 over a period of 250,000-750,000yr prior to the last 250,000yr of stability. In summary, depth profiles of two TCNs provide constraints on the rates of sediment deposition, sources of sediment and transport history, as well as the subsequent exposure conditions of the sediment following deposition. Our results are consistent with early Quaternary initiation of hyperaridity for the region. During the Quaternary, winter precipitation events experienced at our sites' latitude (24°S) drive active erosion-deposition cycles. The northward migration of the subtropical front during Quaternary glacial cycles may have enhanced precipitation at 24°S, leading to more active fluvial processes during cooler periods.
KW - Atacama Desert
KW - Be
KW - Cosmogenic nuclides
KW - Fluvial processes
KW - Hyperarid
KW - Ne
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U2 - 10.1016/j.epsl.2013.04.005
DO - 10.1016/j.epsl.2013.04.005
M3 - Article
AN - SCOPUS:84878497953
SN - 0012-821X
VL - 371-372
SP - 125
EP - 133
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
ER -