164-6 Evidence for Paleoenvironmental Changes During the Oldowan to Acheulean Technological Transition from Lower to Middle Bed II Sediments from Paleolake Olduvai

Session: Advances and Applications of Geochemistry in Archaeology

Presenting Author:

Trenton Meier

Authors:

Meier, Trenton H.¹, Herrmann, Edward W.², Brassell, Simon C.³, Hardman, Alice L.⁴, Njau, Jackson K.⁵, Schick, Kathy D.⁶, Toth, Nicholas P.⁷, Stanistreet, Ian G.⁸, Stollhofen, Harald⁹, McHenry, Lindsay J.¹⁰

(1) Department of Earth and Atmospheric Sciences, Indiana University Bloomington, Bloomington, IN, USA; SWCA Environmental Consultants, Austin, Texas, USA, (2) Department of Earth and Atmospheric Sciences, Indiana University Bloomington, Bloomington, IN, USA, (3) Department of Earth and Atmospheric Sciences, Indiana University Bloomington, Bloomington, IN, USA, (4) Department of Earth and Atmospheric Sciences, Indiana University Bloomington, Bloomington, IN, USA, (5) Department of Earth and Atmospheric Sciences, Indiana University Bloomington, Bloomington, IN, USA; The Stone Age Institute, Gosport, IN, USA, (6) The Stone Age Institute, Gosport, IN, USA, (7) The Stone Age Institute, Gosport, IN, USA, (8) Department of Earth and Ocean Sciences, University of Liverpool, Liverpool, United Kingdom; The Stone Age Institute, Gosport, IN, USA, (9) GeoZentrum Nordbayern, Friedrich-Alexander-University, Erlangen, Germany; The Stone Age Institute, Gosport, IN, USA, (10) Department of Geosciences, University of Wisconsin-Milwaukee, Milwaukee, WI, USA; The Stone Age Institute, Gosport, IN, USA,

Abstract:

The Bed II stratigraphic sequence of Olduvai Gorge (1.8 - 1.15 Ma) spans a dynamic interval across eastern Africa characterized by evidence for landscape aridification, enhanced lake alkalinity and salinity, multiple tectonic and volcanic events, and changes in hominin diversity and cranial capacity increases. It also encompasses the Oldowan to Acheulean technological transition, which records a shift from assemblages characterized by simple flakes and choppers to a more diverse suite of bifacial and specialized tools. Archaeological records from Olduvai Gorge place this technological evolution at circa 1.7 Ma, albeit as a gradual rather than abrupt transition. Consistent with prior studies, we hypothesize that environmental changes affecting water availability also impacted the resources available to hominins prompting developments in stone tool technologies. Our research aims to decipher depositional paleoenvironments of paleolake Olduvai for the stratigraphic succession from upper Bed I through lower to middle Bed II (~1.8 - 1.66 Ma). It explores temporal trends in isotopic and molecular proxies that reflect the vegetation response to changes in climate (δ¹³C_org; distributions and δ¹³C compositions of n-alkanes) in claystones from both stone/sediment cores and archaeological outcrops. Collectively, these data suggest variable, yet drier conditions in upper Bed I, with a dominance of C₄ grasses throughout the lower to middle Bed II sequence. Thus, the Oldowan to Acheulean transition occurs concomitantly with gradual changes in the landscape and vegetation rather than the marked climatic fluctuations manifested in the wet/dry cycles of upper Bed I. Hence, the development in tool technology may reflect hominin adaptation to changes in the availability of resources associated with a consistently dry environment.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7183

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