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Your search keyword '"Deino, Alan L"' showing total 175 results
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175 results on '"Deino, Alan L"'

1. The palaeoclimate potential of continental scientific drilling

Author

Obrist-Farner, Jonathan, Anderson, Lesleigh, Baker, Paul, Berke, Melissa A., Beverly, Emily J., Brigham-Grette, Julie, Brown, Erik, Castañeda, Isla S., Deino, Alan L., Fritz, Sherilyn C., Goldstein, Steven L., Kehrwald, Natalie M., Kirby, Matthew, Miller, Kenneth G., Olsen, Paul, Boush, Lisa Park, Robinson, Marci M., Russell, James, and Soreghan, Gerilyn S.

Published
2024
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11. A million year vegetation history and palaeoenvironmental record from the Lake Magadi Basin, Kenya Rift Valley

Author

Muiruri, Veronica M., Owen, R. Bernhart, Lowenstein, Tim K., Renaut, Robin W., Marchant, Robert, Rucina, Stephen M., Cohen, Andrew, Deino, Alan L., Sier, Mark J., Luo, Shangde, Leet, Kennie, Campisano, Christopher, Rabideaux, Nathan M., Deocampo, Daniel, Shen, Chuan-Chou, Mbuthia, Anthony, Davis, Brant C., Aldossari, Wadha, and Wang, Chenyu

Published
2021
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17. Long-distance stone transport and pigment use in the earliest Middle Stone Age

Author

Brooks, Alison S., Yellen, John E., Potts, Richard, Behrensmeyer, Anna K., Deino, Alan L., Leslie, David E., Ambrose, Stanley H., Ferguson, Jeffrey R., d’Errico, Francesco, Zipkin, Andrew M., Whittaker, Scott, Post, Jeffrey, Veatch, Elizabeth G., Foecke, Kimberly, and Clark, Jennifer B.

Published
2018

20. Late Pliocene Homo and Hominid Land Use from Western Olduvai Gorge, Tanzania

Author

Blumenschine, Robert J., Peters, Charles R., Masao, Fidelis T., Clarke, Ronald J., Deino, Alan L., Hay, Richard L., Swisher, Carl C., Stanistreet, Ian G., Ashley, Gail M., McHenry, Lindsay J., Sikes, Nancy E., van der Merwe, Nikolaas J., Tactikos, Joanne C., Cushing, Amy E., Deocampo, Daniel M., Njau, Jackson K., and Ebert, James I.

Published
2003

24. High‐Latitude, Indian Ocean, and Orbital Influences on Eastern African Hydroclimate Across the Plio‐Pleistocene Boundary.

Author

Mitsunaga, Bryce A., Lupien, Rachel L., Ouertani, Samantha, Stubbs, Brandon, Deino, Alan L., Kingston, John D., Stockhecke, Mona, Brown, Erik T., and Russell, James M.

Subjects
PLIOCENE-Pleistocene boundary, AGULHAS Current, OCEAN temperature, ATMOSPHERIC circulation, METEOROLOGICAL precipitation, GLOBAL cooling, GLACIATION, MILANKOVITCH cycles, CONTINENTS
Abstract

Terrestrial‐marine dust fluxes, pedogenic carbonate δ13C values, and various paleovegetation proxies suggest that Africa experienced gradual cooling and drying across the Pliocene‐Pleistocene (Plio‐Pleistocene) boundary (2.58 million years ago [Ma]). However, the timing, magnitude, resolution, and relative influences of orbitally‐driven changes in high latitude glaciations and low latitude insolation differ by region and proxy. To disentangle these forcings and investigate equatorial eastern African climate across the Plio‐Pleistocene boundary, we generated a high‐resolution (∼3,000‐year) data set of compound‐specific n‐alkane leaf wax δ2H values—a robust proxy for atmospheric circulation and precipitation amount—from the HSPDP‐BTB13‐1A core, which spans a ∼3.3–2.6 Ma sequence in the Baringo‐Tugen Hills‐Barsemoi Basin of central Kenya. In combination with the physical sedimentology, our data indicate that precipitation varied strongly with orbital obliquity, not precession, during the late Pliocene, perhaps imparted by variations in the cross‐equatorial insolation gradient. We also observe a marked shift toward wetter conditions beginning ∼3 Ma that corresponds with global cooling, drying in western Australia, and a steepening of the west‐east zonal Indian Ocean (IO) sea surface temperature (SST) gradient. We propose that northward migration of the Subtropical Front reduced Agulhas current leakage, warming the western IO and causing changes in the IO zonal SST gradient at 3 Ma, a process that has been observed in the latest Pleistocene‐Holocene but not over longer timescales. Thus, the late Cenozoic moisture history of eastern Africa is driven by a complex mixture of low‐latitude insolation, the IO SST gradient, and teleconnections to distal high‐latitude cooling. Key Points: We present new high resolution (3,000‐year) leaf wax δ2H data from central Kenya spanning 3.3–2.6 million years before present (Ma)Pronounced 41,000‐year variability throughout is potentially attributable to the cross‐equatorial insolation gradientLong‐term (>200,000‐year) variability in eastern African hydroclimate tracks the zonal Indian Ocean surface temperature gradient [ABSTRACT FROM AUTHOR]

Published
2023
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32. Oldest evidence of abundant C4 grasses and habitat heterogeneity in eastern Africa.

Author

Peppe, Daniel J., Cote, Susanne M., Deino, Alan L., Fox, David L., Kingston, John D., Kinyanjui, Rahab N., Lukens, William E., MacLatchy, Laura M., Novello, Alice, Strömberg, Caroline A. E., Driese, Steven G., Garrett, Nicole D., Hillis, Kayla R., Jacobs, Bonnie F., Jenkins, Kirsten E. H., Kityo, Robert M., Lehmann, Thomas, Manthi, Fredrick K., Mbua, Emma N., and Michel, Lauren A.

Published
2023
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38. Earliest known Oldowan Artifacts at > 2.58 Ma from Ledi-Geraru, Ethiopia, highlight early technological diversity

Author

Braun, David R., Aldeias, Vera, Archer, William A., Ramon Arrowsmith, J., Baraki, Niguss, Campisano, Christopher J., Deino, Alan L., DiMaggio, Erin N., Dupont-Nivet, Guillaume, Engda, Blade, Feary, David A., Garello, Dominique I., Kerfelew, Zenash, McPherron, Shannon P., Patterson, David B., Reeves, Jonathan S., Thompson, Jessica C., and Reed, Kaye E.

Subjects
Zoology
Abstract

The manufacture of flaked stone artifacts represents a major milestone in the technology of the human lineage. Although the earliest production of primitive stone tools, predating the genus Homo and emphasizing percussive activities, has been reported at 3.3 million years ago (Ma) from Lomekwi, Kenya, the systematic production of sharp-edged stone tools is unknown before the 2.58–2.55 Ma Oldowan assemblages from Gona, Ethiopia. The organized production of Oldowan stone artifacts is part of a suite of characteristics that is often associated with the adaptive grade shift linked to the genus Homo. Recent discoveries from Ledi-Geraru (LG), Ethiopia, place the first occurrence of Homo ∼250 thousand years earlier than the Oldowan at Gona. Here, we describe a substantial assemblage of systematically flaked stone tools excavated in situ from a stratigraphically constrained context [Bokol Dora 1, (BD 1) hereafter] at LG bracketed between 2.61 and 2.58 Ma. Although perhaps more primitive in some respects, quantitative analysis suggests the BD 1 assemblage fits more closely with the variability previously described for the Oldowan than with the earlier Lomekwian or with stone tools produced by modern nonhuman primates. These differences suggest that hominin technology is distinctly different from generalized tool use that may be a shared feature of much of the primate lineage. The BD 1 assemblage, near the origin of our genus, provides a link between behavioral adaptations—in the form of flaked stone artifacts—and the biological evolution of our ancestors. info:eu-repo/semantics/publishedVersion

Published
2020

41. Reconstructing the Environmental Context of Human Origins in Eastern Africa Through Scientific Drilling.

Author

Cohen, Andrew S., Campisano, Christopher J., Arrowsmith, J. Ramón, Asrat, Asfawossen, Beck, Catherine C., Behrensmeyer, Anna K., Deino, Alan L., Feibel, Craig S., Foerster, Verena, Kingston, John D., Lamb, Henry F., Lowenstein, Tim K., Lupien, Rachel L., Muiruri, Veronica, Olago, Daniel O., Owen, R. Bernhart, Potts, Richard, Russell, James M., Schaebitz, Frank, and Stone, Jeffery R.

Subjects
HUMAN origins, DRILL cores, PLIOCENE-Pleistocene boundary, CORE drilling, FOSSIL hominids, WATERSHEDS
Abstract

Paleoanthropologists have long speculated about the role of environmental change in shaping human evolution in Africa. In recent years, drill cores of late Neogene lacustrine sedimentary rocks have yielded valuable high-resolution records of climatic and ecosystem change. Eastern African Rift sediments (primarily lake beds) provide an extraordinary range of data in close proximity to important fossil hominin and archaeological sites, allowing critical study of hypotheses that connect environmental history and hominin evolution. We review recent drill-core studies spanning the Plio–Pleistocene boundary (an interval of hominin diversification, including the earliest members of our genus Homo and the oldest stone tools), and the Mid–Upper Pleistocene (spanning the origin of Homo sapiens in Africa and our early technological and dispersal history). Proposed drilling of Africa's oldest lakes promises to extend such records back to the late Miocene. High-resolution paleoenvironmental records are critical for understanding external drivers of human evolution. African lake basin drill cores play a critical role in enhancing hominin paleoenvironmental records given their continuity and proximity to key paleoanthropological sites. The oldest African lakes have the potential to reveal a comprehensive paleoenvironmental context for the entire late Neogene history of hominin evolution. [ABSTRACT FROM AUTHOR]

Published
2022
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49. East African lake evidence for Pliocene millennial-scale climate variability

Author

Wilson, Katy E., Maslin, Mark A., Leng, Melanie J., Kingston, John D., Deino, Alan L., Edgar, Robert K., and Mackay, Anson W.

Abstract

Late Cenozoic climate history in Africa was punctuated by episodes of variability, characterized by the appearance and disappearance of large freshwater lakes within the East African Rift Valley. In the Baringo-Bogoria basin, a well-dated sequence of diatomites and fluviolacustrine sediments documents the precessionally forced cycling of an extensive lake system between 2.70 Ma and 2.55 Ma. One diatomite unit was studied, using the oxygen isotope composition of diatom silica combined with X-ray fluorescence spectrometry and taxonomic assemblage changes, to explore the nature of climate variability during this interval. Data reveal a rapid onset and gradual decline of deepwater lake conditions, which exhibit millennial-scale cyclicity of ∼1400–1700 yr, similar to late Quaternary Dansgaard-Oeschger events. These cycles are thought to reflect enhanced precipitation coincident with increased monsoonal strength, suggesting the existence of a teleconnection between the high latitudes and East Africa during this period. Such climatic variability could have affected faunal and floral evolution at the time.

Published
2014
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50. The New CLOCIT Irradiation Facility for 40Ar/39Ar Geochronology: Characterisation, Comparison with CLICIT and Implications for High‐Precision Geochronology.

Author

Rutte, Daniel, Becker, Tim A., Deino, Alan L., Reese, Steven R., Renne, Paul R., and Schickler, Robert A.

Subjects
ARGON isotopes, IRRADIATION, NUCLEAR reactions, REFERENCE sources, NEUTRON flux
Abstract

The Cadmium‐Lined Outer‐Core Irradiation Tube (CLOCIT) is a new irradiation facility for 40Ar/39Ar geochronology at the Oregon State University TRIGA® reactor. We report fluence (i.e., time‐integrated flux) parameters from the first four CLOCIT irradiations and compare them with the existing Cadmium‐Lined Inner‐Core Irradiation Tube (CLICIT). CLOCIT provides an average neutron flux equivalent of 1.45–1.53 × 10−4 J h−1; about 55% of CLICIT. Radial fluence gradients were on the order of 0.2–4.2% cm−1. A planar fit of J‐values results in residuals in the range of uncertainty in the J‐value, but systematic deviations resolve a non‐planar component of the neutron flux field, which has also been observed in CLICIT. Axial neutron fluence gradients were 0.6–1% cm−1, compared with 0.7–1.6% cm−1 for the CLICIT. Production rate ratios of interfering reactions were (40Ar/39Ar)K = (4 ± 6) × 10−4 and (38Ar/39Ar)K = (1.208 ± 0.002) × 10−2, (36Ar/37Ar)Ca =  (2.649 ± 0.014) × 10−4, (38Ar/37Ar)Ca =  (3.33 ± 0.12) × 10−5 and (39Ar/37Ar)Ca =  (9.1 ± 0.28) × 10−4, similar to the CLICIT values. [ABSTRACT FROM AUTHOR]

Published
2018
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