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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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5. 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
Ar-Ar dating, geochronology, reference materials, argon isotopes, neutron fluence gradient, nuclear reactions, research reactor, Geochemistry, Geology, Geochemistry & Geophysics
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.

Published
2018

12. Intercalibration and age of the Alder Creek sanidine 40Ar/39Ar standard

Author

Niespolo, Elizabeth M, Rutte, Daniel, Deino, Alan L, and Renne, Paul R

Subjects
Geochemistry, Geology, Physical Geography and Environmental Geoscience, Paleontology
Abstract

The accuracy of 40Ar/39Ar geochronology relies in large part on precise and accurate calibration of the ages and K-Ar isotopic compositions of standards. A widely used standard for Quaternary samples, the ∼1.2 Ma Alder Creek sanidine (ACs), has published ages spanning a range of ∼2%. New measurements of ACs co-irradiated with the Fish Canyon sanidine (FCs) standard and sanidines from astronomically dated Miocene tuffs in Crete and Morocco yield results that enable both (i) a direct calibration of ACs relative to FCs, and (ii) stepwise calibrations between these two standards employing the Miocene intermediaries. Results are summarized by the parameter RFCsACs, defined as the ratio of (40Ar*/39ArK) of ACs to FCs, which embodies the fundamental age relationship between these standards that is independent of systematic variables such as decay constants or absolute ages of standards. Our new measurements, executed using three mass spectrometers and various irradiation and analytical protocols, yield a weighted mean RFCsACs = 0.041702 ± 0.000014 (σ). This result can be combined with previously published determinations of R values for ACs relative to the Miocene tuffs and to FCs to yield a recommended interlaboratory value ofRFCsACs = 0.041707 ± 0.000011. The weighted-mean age of ACs using this interlaboratory value, based on astronomically-calibrated ages of FCs and the Miocene intermediary sanidines, is tACs = 1.1848 ± 0.0006 Ma (±0.05%). Applying this result to the most precise published 40Ar/39Ar data for the Matuyama-Brunhes geomagnetic polarity reversal yields tMBB = 780.1 ± 0.8 ka. In addition, these new data for ACs support previous conclusions that U-Pb zircon ages from the Alder Creek rhyolite incorporate ∼13 ka of pre-eruptive residence time.

Published
2017

13. 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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19. Controls on Quaternary geochemical and mineralogical variability in the Koora Basin and South Kenya Rift

Author

National Science Foundation (US), Natural Sciences and Engineering Research Council of Canada, Research Grants Council (Hong Kong), Consejo Nacional de Ciencia y Tecnología (México), Owen, R. Bernhart, Rabideaux, Nathan, Bright, Jordon, Rosca, Carolina, Renaut, Robin W., Potts, Richard, Behrensmeyer, Anna K., Deino, Alan L., Cohen, Andrew S., Muiruri, Veronica, Dommain, René, National Science Foundation (US), Natural Sciences and Engineering Research Council of Canada, Research Grants Council (Hong Kong), Consejo Nacional de Ciencia y Tecnología (México), Owen, R. Bernhart, Rabideaux, Nathan, Bright, Jordon, Rosca, Carolina, Renaut, Robin W., Potts, Richard, Behrensmeyer, Anna K., Deino, Alan L., Cohen, Andrew S., Muiruri, Veronica, and Dommain, René

Abstract

The South Kenya Rift is comprised of a series of N-S-oriented grabens with sediments that preserve an approximate one-million-year environmental history that reflects the interplay of climate, tectonism and volcanism. This study attempts to disentangle the relative roles of these major controls by comparing the geochemical records preserved in three sedimentary basins. The study focuses on the Koora Basin using bulk geochemical data in a 139-m-long core. This record is then compared with geochemical data and environmental histories from a 196-m-long core at Magadi and outcrops in the Olorgesailie Basin. Four climatic phases (1000–850; 850–470; 470–400; 400–0 ka) are recognised at Koora, which can also be distinguished in the Magadi and Olorgesailie Basins. However, inter-basin contrasts also suggest that additional, non-climatic factors influenced these geochemical histories, particularly during four intervals. These include 1) the Magadi Transition (MT; ∼770–700 ka), 2) the Magadi Tectonic Event (MTE; ∼540 ka), 3) the Koora Instability Period (KIP; ∼325–180 ka), and 4) the Trona Precipitation Period (TPP; ∼105–0 ka). Prior to the MT, Zr/TiO, La/Lu, Mo, As, V and Na/Ca in Magadi and Koora cores were similar but afterwards diverged. Major reductions in transition metals at Magadi during the MTE reflect tectonically-induced cross-rift drainage diversion. This contrasts with the Koora and Olorgesailie basins where these metals were constant from ∼1000 to 300 ka. The KIP represents a significant increase in volcanic inputs to the Koora Basin and increased geochemical variability. Bromine (Br), which reflects peralkaline volcanic activity and/or evaporative concentration, is elevated during the KIP at Koora but is below detection limits in the rest of the Koora core. Br in the Magadi core does not correlate with that in the Koora record, suggesting contrasting accumulation processes. The TPP represents a phase of trona precipitation at Magadi but not at Koora. This diffe

Published
2024

23. 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

27. 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

31. 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. The evolution of hominoid locomotor versatility: Evidence from Moroto, a 21 Ma site in Uganda

Author

MacLatchy, Laura M., primary, Cote, Susanne M., additional, Deino, Alan L., additional, Kityo, Robert M., additional, Mugume, Amon A. T., additional, Rossie, James B., additional, Sanders, William J., additional, Cosman, Miranda N., additional, Driese, Steven G., additional, Fox, David L., additional, Freeman, April J., additional, Jansma, Rutger J. W., additional, Jenkins, Kirsten E. H., additional, Kinyanjui, Rahab N., additional, Lukens, William E., additional, McNulty, Kieran P., additional, Novello, Alice, additional, Peppe, Daniel J., additional, Strömberg, Caroline A. E., additional, Uno, Kevin T., additional, Winkler, Alisa J., additional, and Kingston, John D., additional

Published
2023
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33. Oldest evidence of abundant C 4 grasses and habitat heterogeneity in eastern Africa

Author

Peppe, Daniel J., primary, Cote, Susanne M., additional, Deino, Alan L., additional, Fox, David L., additional, Kingston, John D., additional, Kinyanjui, Rahab N., additional, Lukens, William E., additional, MacLatchy, Laura M., additional, Novello, Alice, additional, Strömberg, Caroline A. E., additional, Driese, Steven G., additional, Garrett, Nicole D., additional, Hillis, Kayla R., additional, Jacobs, Bonnie F., additional, Jenkins, Kirsten E. H., additional, Kityo, Robert M., additional, Lehmann, Thomas, additional, Manthi, Fredrick K., additional, Mbua, Emma N., additional, Michel, Lauren A., additional, Miller, Ellen R., additional, Mugume, Amon A. T., additional, Muteti, Samuel N., additional, Nengo, Isaiah O., additional, Oginga, Kennedy O., additional, Phelps, Samuel R., additional, Polissar, Pratigya, additional, Rossie, James B., additional, Stevens, Nancy J., additional, Uno, Kevin T., additional, and McNulty, Kieran P., additional

Published
2023
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39. 40Ar/39Ar Dating of Laetoli, Tanzania

Author

Deino, Alan L., Conard, Nicholas, Advisory editor, Fleagle, John G., Advisory editor, Hublin, Jean-Jacques, Advisory editor, MacPhee, Ross D. E., Advisory editor, Makovicky, Peter, Advisory editor, McBrearty, Sally, Advisory editor, Meng, Jin, Advisory editor, Plummer, Tom, Advisory editor, Silcox, Mary, Advisory editor, and Harrison, Terry, editor

Published
2011
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42. Reconstructing the Environmental Context of Human Origins in Eastern Africa Through Scientific Drilling

Author

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

Published
2022
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44. Age of the oldest known Homo sapiens from eastern Africa

Author

Vidal, Céline M., Lane, Christine S, Asrat, Asfawossen, Barfod, Dan, Mark, Darren F, Tomlinson, Emma L, Tadesse, Amdemichael, Yirgu, Gezahegn, Deino, Alan L, Hutchison, William, Mounier, Aurélien, Oppenheimer, Clive, Vidal, Céline M., Lane, Christine S, Asrat, Asfawossen, Barfod, Dan, Mark, Darren F, Tomlinson, Emma L, Tadesse, Amdemichael, Yirgu, Gezahegn, Deino, Alan L, Hutchison, William, Mounier, Aurélien, and Oppenheimer, Clive

Abstract

Efforts to date the oldest modern human fossils in eastern Africa, from Omo-Kibish 1–3 and Herto 4,5 in Ethiopia, have drawn on a variety of chronometric evidence, including 40 Ar/ 39 Ar ages of stratigraphically associated tuffs. The ages that are generally reported for these fossils are around 197 thousand years (kyr) for the Kibish Omo I 3,6,7 ,and around 160–155 kyr for the Herto hominins 5,8 .However, the stratigraphic relationships and tephra correlations that underpin these estimates have been challenged 6,8 .Here we report geochemical analyses that link the Kamoya’s Hominid Site (KHS) Tuff 9 ,which conclusively overlies the member of the Omo-Kibish Formation that contains Omo I, with a major explosive eruption of Shala volcano in the Main Ethiopian Rift. By dating the proximal deposits of this eruption, we obtain a new minimum age for the Omo fossils of 233 ± 22 kyr. Contrary to previous arguments 6,8 ,we also show that the KHS Tuff does not correlate with another widespread tephra layer, the Waidedo Vitric Tuff, and therefore cannot anchor a minimum age for the Herto fossils. Shifting the age of the oldest known Homo sapiens fossils in eastern Africa to before around 200 thousand years ago is consistent with independent evidence for greater antiquity of the modern human lineage 10 ., SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2022

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

Author

Cohen, Andrew S., Campisano, Christopher J., Arrowsmith, J. Ramon, 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, Stone, Jeffery R., Trauth, Martin H., Yost, Chad L., Cohen, Andrew S., Campisano, Christopher J., Arrowsmith, J. Ramon, 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, Stone, Jeffery R., Trauth, Martin H., and Yost, Chad L.

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.

Published
2022

46. Geochronology and glass geochemistry of major pleistocene eruptions in the Main Ethiopian Rift: Towards a regional tephrostratigraphy

Author

Vidal, Céline M., Fontijn, Karen, Lane, Christine S, Asrat, Asfawossen, Barfod, Dan, Tomlinson, Emma L, Piermattei, Alma, Hutchison, William, Tadesse, Amdemichael, Yirgu, Gezahegn, Deino, Alan L, Moussallam, Yves, Mohr, Paul, Williams, Frances, Mather, Tamsin A., Pyle, David M, Oppenheimer, Clive, Vidal, Céline M., Fontijn, Karen, Lane, Christine S, Asrat, Asfawossen, Barfod, Dan, Tomlinson, Emma L, Piermattei, Alma, Hutchison, William, Tadesse, Amdemichael, Yirgu, Gezahegn, Deino, Alan L, Moussallam, Yves, Mohr, Paul, Williams, Frances, Mather, Tamsin A., Pyle, David M, and Oppenheimer, Clive

Abstract

The Main Ethiopian Rift (MER) is renowned as a focus of investigations into human origins. It is also the site of many large volcanic calderas, whose eruptions have spanned the timeframe of speciation, cultural innovation, and dispersal of our species. Yet, despite their significance for dating human fossils and cultural materials, the timing and geochemical signatures of some of the largest eruptions have remained poorly constrained at best. Here, through a programme of field surveys, geochemical analysis and 40Ar/39Ar dating, we report the ages of MER ignimbrites and link them to widespread tephra layers found in sequences of archaeological and paleoenvironmental significance. We date major eruptions of Fentale (76 ± 18 ka), Shala (ca. 145–155 ka), Kone (184 ± 42 ka and ca. 200 ± 12 ka) and Gedemsa (251 ± 47 ka) volcanoes, and correlate a suite of regionally important tephra horizons. Geochemical analysis highlights the predominantly peralkaline rhyolitic melt compositions (7.5–12 wt% Na2O + K2O, 70–76 wt% SiO2) across the central MER and remarkable similarity in incompatible trace element ratios, limiting the correlation of deposits via glass composition alone. However, by integrating stratigraphic and geochronological evidence from proximal deposits, lake sediment cores and distal outcrops at archaeological sites, we have traced ash layers associated with the ca. 177 ka Corbetti, ca. 145–155 ka Shala and ca. 108 ka Bora-Baricha-Tullu-Moye eruptions across southern Ethiopia. In addition to strengthening the tephrochronological framework that supports paleoenvironmental and archaeological work in the region, our findings have wider implications for evaluating the hypothesis of a middle Pleistocene ‘ignimbrite flare-up’ in the MER, and for evaluating the impacts of these great eruptions on landscapes, hydrology, and human ecology., SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2022

48. 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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