A multiscale stratigraphic investigation of the context of StW 573 Little Foot and Member 2, Sterkfontein Caves, South Africa
Dominic J Stratford,
Travis R Pickering,
Jason L. Heaton,
Kris J Carlson,
George M. Leader,
Ronald J. Clarke
Posted 29 Nov 2018
bioRxiv DOI: 10.1101/482711 (published DOI: 10.1016/j.jhevol.2019.05.008)
Posted 29 Nov 2018
The Sterkfontein Caves has an 80 year history of yielding remarkable evidence of hominin evolution and is currently the world's richest Australopithecus-bearing site. Included in Sterkfontein's hominin assemblage is StW 573 (Little Foot). Discovered in the Member 2 deposit in the Silberberg Grotto, StW 573 represents the most complete Australopithecus skeleton yet found. Because of its importance to the fossil hominin record, the geological age of Little Foot has been the subject of significant debate. Two main hypotheses have been proposed regarding the formation and age of Member 2 and by association StW 573. The first, proposes that Member 2 formed relatively rapidly, starting to accumulate at around 2.8 million years ago and that the unit is isolated to the Silberberg Grotto - the underlying chambers and passages forming later. The second proposes that Member 2 formed slowly, its accumulation starting before 3.67 million years ago and that the deposit extends into the Milner Hall and close to the base of the cave system. Both assume a primary association between StW 573 and Member 2, although which sediments in the Silberberg Grotto are associated with Member 2 has also been questioned. Recently a third alternative hypothesis questioning the association of StW 573 to Member 2 sediments proposed a two-stage burial scenario in which sediments associated with StW 573 represent a secondary and mixed-age deposit reworked from a higher cave. The stratigraphic and sedimentological implications of these hypotheses are tested here through the application of a multiscale investigation of Member 2, with reference to the taphonomy of the Little Foot skeleton. The complete infilling sequence of Member 2 is described and depositional units are tracked across all exposures of the deposit in the Silberberg Grotto and into the Milner Hall. Facies development follows patterns characteristic of colluvially accumulated taluses with 30-40 degrees angles of repose developing coarser distal facies. Sediments are generally stratified and conformably deposited in a sequence of silty sands eroded from well-developed lateritic soils on the landscape surface. Voids, clasts and bioclasts are organized consistently across and through Member 2 according to the underlying deposit geometry, indicating a gradual deposit accretion with no distinct collapse facies evident, no successive debris flow accumulation, and only localized intra-unit post-depositional modification. The stratigraphy and sedimentology of Member 2 supports a simple single-stage accumulation process through which Member 2 partially fills the Silberberg Grotto and extends into the deeper chambers and passages of the Sterkfontein Caves. Through this work we demonstrate at multiple scales the primary association between the sediments of Member 2 and the StW 573 Little Foot skeleton.
- Downloaded 1,691 times
- Download rankings, all-time:
- Site-wide: 15,213
- In paleontology: 20
- Year to date:
- Site-wide: 66,130
- Since beginning of last month:
- Site-wide: 50,226
Downloads over time
Distribution of downloads per paper, site-wide
- 27 Nov 2020: The website and API now include results pulled from medRxiv as well as bioRxiv.
- 18 Dec 2019: We're pleased to announce PanLingua, a new tool that enables you to search for machine-translated bioRxiv preprints using more than 100 different languages.
- 21 May 2019: PLOS Biology has published a community page about Rxivist.org and its design.
- 10 May 2019: The paper analyzing the Rxivist dataset has been published at eLife.
- 1 Mar 2019: We now have summary statistics about bioRxiv downloads and submissions.
- 8 Feb 2019: Data from Altmetric is now available on the Rxivist details page for every preprint. Look for the "donut" under the download metrics.
- 30 Jan 2019: preLights has featured the Rxivist preprint and written about our findings.
- 22 Jan 2019: Nature just published an article about Rxivist and our data.
- 13 Jan 2019: The Rxivist preprint is live!