The revised stratigraphy of the hominin-bearing site of Kromdraai (Gauteng, South Africa) and associated perspectives

The Plio-Pleistocene site of Kromdraai B (South Africa), located in the ‘Cradle of Humankind’ area recognized in 1998 by UNESCO, corresponds to a Plio-Pleistocene paleokarst that yielded the holotype of Paranthropus robustus in 1938. Since that discovery, thousands of faunal remains (including additional hominin fossils) and stone tools have been discovered there. Here we report a new study of the karstic fillings of the hominin-bearing site of Kromdraai, which enables a reappraisal of its stratigraphy. The deposits correspond to a talus cone fed by one entrance that progressively filled the cave, which is larger than previously thought. Based on the stratigraphy, geometry, and composition of the breccias, we propose a new and more complex evolution of the cave. Four main periods of cave filling can be distinguished, corresponding to four kinds of deposits directly related to the evolution of the cave, and which show the progressive dismantling of the cavity and increasing influence from the landscape surface. This filling regime, however, is not continuous, and major unconformities identified may cover long periods of time. Despite this, an overall coherence emerges from the history of the cave and its deposits, the paleontological and paleoanthropological data, and the archaeological studies. It is now possible to reinterpret the discoveries from earlier investigations and place them in their general stratigraphic context. Our study shows that Kromdraai spans a much longer time span of hominin evolution than previously proposed. In addition, the breccias from the central part of the Kromdraai B site provide some of the first data on at least part of a hitherto unrecorded period at Sterkfontein: a phase marked by a major erosional unconformity between Members 4 and 5, before 2.20 Ma.