Heritage Cases

In 2016, Profs L. Bruxelles and D. Stratford identified a new infill stratigraphically located underneath Member 1 Lower Bank at Swartkrans Cave. This was on the basis of breccia composition and slope orientation. This new deposit is characterized by abundant chert clasts, is orientated on a 45 degree slope dipping from south to north and mass has been preliminarily named the ‘pre-Member 1 infill’ (pM1). Further, it is differentiated from Member 1 Lower Bank, the latter is comprised of an unconsolidated, orange sediments that are horizontally bedded in the northern portion of the site. Th pM1 deposit is characterized by poorly-sorted, silty-to-sandy, dark brown (2.5YR 3/2) sediments with degrading and weathered chert clasts and flowstone fragments inclusions ranging from <1cm to >10cm in size, including large, chert blocks (i.e. >50cm). Most of the geological inclusions are heavily stained by manganese and some of the smaller chert clasts (<5 cm) have been rounded, which suggests that the pM1 infill is composed of surface weathered materials that were incorporated into a talus deposit through colluvial processes. To date, the pM1 deposit has been excavated in two areas where it is exposed at the surface level: (1) to the west of the cemented path leading to Member 4 (called the ‘Pathway Excavation’), and (2) in a pit to the east of the same path (called the ‘Pit Excavation’) (Fig. 1). The pM1 Pit Excavation consisted of a 2 x 3 m grid and took place in June/July and October of 2017, which removed ~400 cm3 of sediment and recovered 65 artefactual finds. The pM1 Pathway Excavation consisted of a 1 x 3 m grid and took place in October of 2019, which removed ~110 cm3 of sediment and recovered 87 artefacts, which are under analysis. Dating the pM1 deposit is critical for understanding is chronological position within the Swartkrans Formation and to test the hypothesis that it represents the oldest sedimentary infill known at the site. Six chert clasts were collected under SAHRA permit # 2598 from the pM1 Pit excavation and two from areas where the pM1 infill is exposed on site (Fig. 2). We propose to use these samples for cosmogenic nuclide dating, which has proven successful in dating the sedimentary members at Swartkrans