Fine resolution of early hominin time, Beds I and II, Olduvai Gorge, Tanzania

Carbonate horizons, paleosols, and lake flooding cycles: Beds I and II of Olduvai Gorge, Tanzania

“…Bed I sediments are interbedded with tuff deposits (Tuffs IAeIF) erupted from the Olmoti volcano: thin dolomite beds occur in the lacustrine sediments (Hay and Kyser, 2001) while laterally continuous paleosol horizons are more common in lake margin settings (Leakey, 1971;Liutkus et al, 2005). Bed II contains a major disconformity (w1.75 Ma) below which waxy claystone lake facies containing limestone layers and nodules predominate (Stanistreet, 2012). Above the disconformity beige to white earthy claystones, interpreted as spring-fed wetland deposits (Liutkus and Ashley, 2003), are interbedded with lacustrine waxy claystones.…”

“…The six horizons correlate over distances of several kilometers. Between Tuff IF and Tuff IIA dated at 1.71 Ma (Hay, 1976) there are at least 11 transgressive/regressive cycles (Stanistreet, 2012), so each cycle must reflect a period of about four thousand years (Stanistreet, 2012) and must be significantly shorter than Milankovitch periodicities.…”

Olduvai Gorge and the Olduvai Landscape Paleoanthropology Project

“…It also required the development of finer stratigraphic control on landscape-scale paleoanthropological samples than availed by traditionally relied upon tephra-chronostratigraphic markers, between which longer-term, more substantial changes to landscape ecology can be expected. A battery of paleoenvironmental expertise was added to OLAPP beginning in 2000, including specialists in general and volcaniclastic facies analysis (e.g., Stollhofen and Stanistreet, 2012;Stanistreet, 2012) as well as macroplant fossil (e.g., Bamford, 2012) analysis, phytolith (e.g., Albert and Bamford, 2012) analysis, and stable isotope analysis of carbonates (Bennett et al, 2012). Finer stratigraphic control was achieved by determinations of cross-basinal geochemical correlations of tephra (e.g., McHenry, 2012) and the introduction of sequence stratigraphy to the lake-centered paleo-Olduvai Basin (e.g., Stanistreet, 2012).…”

Landscape distribution of Oldowan stone artifact assemblages across the fault compartments of the eastern Olduvai Lake Basin during early lowermost Bed II times

“…We focus on the early portion of lowermost Bed II prior to valley incision. Referred to as pre-incisional Lower Bed II (Stanistreet, 2012), this interval was characterized by at least six major cycles of lake transgressions and regressions. It has an estimated duration of ca.…”

“…It has an estimated duration of ca. 20,000 years (Stanistreet, 2012), beginning after the deposition and reworking of Tuff IF at ca. 1.785 Ma (Blumenschine et al, 2003).…”