TY - JOUR
T1 - Tephrostratigraphy and depositional environment of young (<2.94 Ma) Hadar Formation deposits at Ledi-Geraru, Afar, Ethiopia
AU - DiMaggio, Erin N.
AU - Arrowsmith, J. Ramón
AU - Campisano, Christopher J.
AU - Johnson, Roy
AU - Deino, Alan L.
AU - Warren, Mark
AU - Fisseha, Shimeles
AU - Cohen, Andrew S.
N1 - Funding Information:
We would like to thank the Authority for Research and Conservation of Cultural Heritage (A.R.C.C.H.) and the Ministry of Culture and Tourism of Ethiopia for permitting our research endeavors. For logistical and field support we are grateful to our Addis field crew, our A.R.C.C.H. representative Solomon Kebede, our kind Afar friends from the Mille area, and the Institute of Human Origins. We thank Gordon Moore as well as the personnel in the LeRoy Eyring Center for Solid State Science at ASU for their laboratory assistance and Dominique Garello for her help preparing and analyzing samples. This manuscript was greatly improved by comments from Kay Behrensmeyer, an anonymous reviewer, and the editor. This project was funded in part by the Leakey Foundation , the Wenner Gren Foundation for Anthropological Research, the Institute of Human Origins and School of Human Evolution and Social Change at Arizona State University and by NSF grant EAR-0725553 . This is contribution #4 of the Hominin Sites and Paleolakes Drilling Project.
Publisher Copyright:
© 2015 Elsevier Ltd.
PY - 2015/12/1
Y1 - 2015/12/1
N2 - The Pliocene Hadar Formation, exposed throughout the lower Awash Valley, Ethiopia, chronicles the evolution and paleoenvironmental context of early hominins. Deposition of the Hadar Formation continued until at least 2.94 Ma, but what transpired in the Hadar Basin after this time remains poorly documented due to an erosional event that truncated the formation throughout much of the valley. Here we present geologic mapping and stratigraphic analysis of a 26 m-thick section of sedimentary rocks and tephras exposed in the Ledi-Geraru project area in the region of Gulfaytu. The section contains Hadar Formation strata younger than 2.94 Ma, and sediments that we interpret are Busidima Formation in age, <2.7 Ma. We use this record to place additional constraints on depositional environments and the tectonic and paleogeomorphic history of the region. The lower ~20 m of section contains lacustrine deposits that conformably overly a 2.94 Ma marker bed (BKT-2U) that previously served as the uppermost dated tephra in the Hadar Formation. We identified seven post-BKT-2U tephras; three were analyzed for glass chemistry, and one yielded an 40Ar/39Ar age of 2.931 ± 0.017 Ma (1σ). Based on these analyses, the newly mapped deposits at Gulfaytu extend the top of the Hadar Formation, representing ca. 20 kyr of post-BKT-2 sedimentation. The Hadar Basin remained depositional following the BKT-2 eruptions, and paleolake Hadar was present at Gulfaytu at this time. An erosional surface marked by a conglomerate truncates the Hadar strata suggesting that the Gulfaytu region was also was influenced by significant changes to basin architecture well-documented elsewhere in the lower Awash Valley. In addition, geophysical models suggest that central Ledi Geraru hosts a thick subsurface lacustrine sedimentary record within the Hadar Basin. The results of this paper provide the outcrop and near surface characterization for the Hominin Sites and Paleolakes Drilling Project (HSPDP) effort at Gulfaytu.
AB - The Pliocene Hadar Formation, exposed throughout the lower Awash Valley, Ethiopia, chronicles the evolution and paleoenvironmental context of early hominins. Deposition of the Hadar Formation continued until at least 2.94 Ma, but what transpired in the Hadar Basin after this time remains poorly documented due to an erosional event that truncated the formation throughout much of the valley. Here we present geologic mapping and stratigraphic analysis of a 26 m-thick section of sedimentary rocks and tephras exposed in the Ledi-Geraru project area in the region of Gulfaytu. The section contains Hadar Formation strata younger than 2.94 Ma, and sediments that we interpret are Busidima Formation in age, <2.7 Ma. We use this record to place additional constraints on depositional environments and the tectonic and paleogeomorphic history of the region. The lower ~20 m of section contains lacustrine deposits that conformably overly a 2.94 Ma marker bed (BKT-2U) that previously served as the uppermost dated tephra in the Hadar Formation. We identified seven post-BKT-2U tephras; three were analyzed for glass chemistry, and one yielded an 40Ar/39Ar age of 2.931 ± 0.017 Ma (1σ). Based on these analyses, the newly mapped deposits at Gulfaytu extend the top of the Hadar Formation, representing ca. 20 kyr of post-BKT-2 sedimentation. The Hadar Basin remained depositional following the BKT-2 eruptions, and paleolake Hadar was present at Gulfaytu at this time. An erosional surface marked by a conglomerate truncates the Hadar strata suggesting that the Gulfaytu region was also was influenced by significant changes to basin architecture well-documented elsewhere in the lower Awash Valley. In addition, geophysical models suggest that central Ledi Geraru hosts a thick subsurface lacustrine sedimentary record within the Hadar Basin. The results of this paper provide the outcrop and near surface characterization for the Hominin Sites and Paleolakes Drilling Project (HSPDP) effort at Gulfaytu.
KW - Afar depression
KW - Hadar Formation
KW - Hominin paleoenvironments
KW - Pliocene
KW - Stratigraphy
KW - Tephrochronology
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U2 - 10.1016/j.jafrearsci.2015.09.018
DO - 10.1016/j.jafrearsci.2015.09.018
M3 - Article
AN - SCOPUS:84943748041
SN - 1464-343X
VL - 112
SP - 234
EP - 250
JO - Journal of African Earth Sciences
JF - Journal of African Earth Sciences
ER -