Crevasse‐splay and associated depositional environments of the hominin‐bearing lower Okote Member, Koobi Fora Formation (Plio‐Pleistocene), Kenya

Lepre, Christopher J.

doi:10.1002/dep2.31

Cited by 15 publications

(16 citation statements)

References 83 publications

(252 reference statements)

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“…The BFB is a distinctive white tuffaceous crevasse-splay sandstone (13,19) that can be more than 10 m thick. It occurs within the upper part of the mostly red Petrified Forest Mb.…”

Section: Resultsmentioning

confidence: 99%

Empirical evidence for stability of the 405-kiloyear Jupiter–Venus eccentricity cycle over hundreds of millions of years

Kent

Olsen

Rasmussen

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

114

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The Newark-Hartford astrochronostratigraphic polarity timescale (APTS) was developed using a theoretically constant 405-kiloyear eccentricity cycle linked to gravitational interactions with Jupiter-Venus as a tuning target and provides a major timing calibration for about 30 million years of Late Triassic and earliest Jurassic time. While the 405-ky cycle is both unimodal and the most metronomic of the major orbital cycles thought to pace Earth's climate in numerical solutions, there has been little empirical confirmation of that behavior, especially back before the limits of orbital solutions at about 50 million years before present. Moreover, the APTS is anchored only at its younger end by U-Pb zircon dates at 201.6 million years before present and could even be missing a number of 405-ky cycles. To test the validity of the dangling APTS and orbital periodicities, we recovered a diagnostic magnetic polarity sequence in the volcaniclastic-bearing Chinle Formation in a scientific drill core from Petrified Forest National Park (Arizona) that provides an unambiguous correlation to the APTS. New high precision U-Pb detrital zircon dates from the core are indistinguishable from ages predicted by the APTS back to 215 million years before present. The agreement shows that the APTS is continuous and supports a stable 405-kiloyear cycle well beyond theoretical solutions. The validated Newark-Hartford APTS can be used as a robust framework to help differentiate provinciality from global temporal patterns in the ecological rise of early dinosaurs in the Late Triassic, amongst other problems.

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“…The BFB is a distinctive white tuffaceous crevasse-splay sandstone (13,19) that can be more than 10 m thick. It occurs within the upper part of the mostly red Petrified Forest Mb.…”

Section: Resultsmentioning

confidence: 99%

Empirical evidence for stability of the 405-kiloyear Jupiter–Venus eccentricity cycle over hundreds of millions of years

Kent

Olsen

Rasmussen

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

114

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“…Brown and Feibel () have documented the stratigraphic distribution of the Vertisols within the Koobi Fora formation. Lepre () studied the occurrence of Vertisols associated with fluvial avulsion deposits from Pleistocene intervals of the formation. Johnson and Raynolds () were among the first to recognize the presence of vertic features and relate these to past environmental conditions for the formation.…”

Section: Introductionmentioning

confidence: 99%

“…Brown and Feibel (1986) have documented the stratigraphic distribution of the Vertisols within the Koobi Fora formation. Lepre (2017) studied the occurrence of Vertisols associated with fluvial avulsion deposits from lasting on the order of 10 3 -10 4 years. In order to understand how magnetic properties and Fe oxides vary, the two paleosols were systematically sampled downprofile from surface horizon to parent material.…”

Section: Introductionmentioning

confidence: 99%

Constraints on Fe‐Oxide Formation in Monsoonal Vertisols of Pliocene Kenya Using Rock Magnetism and Spectroscopy

Lepre

2019

Geochem Geophys Geosyst

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Pliocene Vertisols from the Turkana Basin of northwest Kenya (~4°N latitude) have been examined using isothermal remanent magnetization (IRM) experiments, susceptibility measurements, and diffuse reflectance spectroscopy. The complete vertical profile of each paleosol is almost intact, measuring >2 m in thickness and being strongly magnetic (IRM at 1.0T ranges from 4 to 25 × 10−3 Am2/kg). Downprofile changes to the proxy indicators suggest uninterrupted pedodevelopment and a lack of stratigraphic inversions caused by argilli‐pedoturbation. Magnetic minerals consist of hematite to a lesser degree, and pedogenic ferrimagnets derived from moisture cycles that were controlled by monsoonal rainfall. Basal pedogenic zones of the paleosols are magnetically intense, and preserve the greatest slickenside development indicating pronounced seasonal wetting and drying. These observations indicate a deeper dry season water table as compared to poorly drained temperate/tropical Vertisols, which suffer reductive dissolution of Fe oxides in basal pedogenic horizons associated with weak magnetic intensities. Magnetic susceptibilities and the well‐represented presence of fine pedogenic ferrimagnets suggest that Pliocene rainfall was greater than the local modern rate of 200 mm/year and may have been within the range of 500–1,000 mm/year. The study highlights the need to expand the database on Vertisols Fe oxides and magnetism, especially considering the anomalously dry and bimodal rainfall seasonality of East Africa.

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“…In this paper, we (1) review the terrain, paleoanthropological sites, and lithostratigraphy of Area 130, (2) present new geochronology and paleomagnetic data, and (3) clarify the lithostratigraphic position of the boundaries for the Burgi, KBS, and Okote Members of the Koobi Fora Formation in Area 130. Furthermore, the implications of our findings are used to refine the sequence and chronology of the archeological and fossils sites from Frank (1976) and Lepre (2017) highlighting the distribution of the various stratigraphic sections studied as well as the location of the major archeological sites and hominin fossils within the area. Stratigraphic sections match the ones described in Figure 3.…”

Section: Introductionmentioning

confidence: 87%

“…There is also a large amount of facies variability within some members. For example, the KBS Member from northeast to southwest varies from fluvial sands, conglomerates, and mudstones to a series of lake-margin, lacustrine, and alluvial deposits across a distance of ∼30 km (Lepre et al, 2007;Lepre, 2017). These difficulties have hampered efforts of dating archeological sites and hominin fossils, and well as underscore the need to individualize chronostratigraphic information for different geographic areas.…”

Section: Background To the Study Areamentioning

confidence: 99%

Temporal and Stratigraphic Framework for Paleoanthropology Sites Within East-Central Area 130, Koobi Fora, Kenya

et al. 2019

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In the Koobi Fora region of the northeast Lake Turkana Basin (Kenya) dozens of archeological sites have been studied for decades in order to understand the behavior of Early Pleistocene hominins. Data collected from these sites have been important for demonstrating the manufacture styles of Oldowan stone-tool users, hominin dietary preferences, and processes of Early Stone Age site formation. A particularly rich locality is collection Area 130. Area 130 is noteworthy for hominin fossils KNM-ER 1805 (Homo) and 1806 (Paranthropus) as well as the FxJj 18 site complex, which represents one of the type localities for the Developed Oldowan of Koobi Fora. However, despite research beginning in the late 1960s, and several revisions to the stratigraphy and dating of the Koobi Fora Formation, few published studies provide a detailed chronostratigraphy for Area 130. The lack of a detailed chronostratigraphy has contributed to conflicting interpretations for the dates of the hominin fossils and archaeological sites. Here we present new geochronologic and paleomagnetic data to develop a chronostratigraphic framework that allows us to directly assess the age of the sediments, fossils, and artifacts from Area 130. Individual pumices from the Orange Tuff marker level and a previously unnamed tuff exposed near the FxJj 18 archaeological site complex (referred here as the FxJj 18 tuff) were analyzed for high-precision single crystal 40 Ar/ 39 Ar dating and dated at 1.763 ± 0.007 Ma and 1.520 ± 0.005 Ma respectively. Concurrently, we collected orientated paleomagnetic samples from stratigraphic levels of the KBS Member in Area 130 and used them to develop a magnetostratigraphic section. Our findings can be used to refine the sequence and chronology of the archaeological and fossils sites from Area 130 and other penecontemporaneous sites within the Lake Turkana Basin. Our data show that the first appearance of the Developed Oldowan for Koobi Fora does not correlate with any obvious evolutionary changes represented by the local hominin hypodigm nor with the arrival of a cognitively advanced hominin. Therefore we speculate that the advent of this more sophisticated type of stone tool was a response to a change in the diet of the genus Homo.

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Crevasse‐splay and associated depositional environments of the hominin‐bearing lower Okote Member, Koobi Fora Formation (Plio‐Pleistocene), Kenya

Cited by 15 publications

References 83 publications

Empirical evidence for stability of the 405-kiloyear Jupiter–Venus eccentricity cycle over hundreds of millions of years

Empirical evidence for stability of the 405-kiloyear Jupiter–Venus eccentricity cycle over hundreds of millions of years

Constraints on Fe‐Oxide Formation in Monsoonal Vertisols of Pliocene Kenya Using Rock Magnetism and Spectroscopy

Temporal and Stratigraphic Framework for Paleoanthropology Sites Within East-Central Area 130, Koobi Fora, Kenya

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