The Sterkfontein western breccias: statigraphy, fauna and artefacts

Ogola, Christine A.
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The Sterkfontein Caves are one of the dolomite cave systems located in Gaut- eng Province, South Africa. These caves are important to paleoanthropology because they have yielded a large number of fossils of early hominids, fauna, °ora and some of the earliest stone tools in South Africa. The caves contain deposits classi¯ed as stratigraphic members within the Sterkfontein Forma- tion. These members are named 1 to 6 in sequence of ascending order and age, and additional in¯lls, the StW 53 In¯ll and the Post-Member 6 In¯ll, have also recently been identi¯ed. There are in addition deposits in three separate cav- erns: the Jacovec Cavern and the Name Chamber located underground, and the Lincoln Cave located adjacent to the main cave deposits. Member 1 is a thick sterile deposit lying on the °oor of the Silberberg Grotto. Member 2 has produced the ¯rst and most complete Australopithecus hominid skull in direct association with its skeleton, together with other fossil faunal material, all of which are thought to comprise death trap assemblages. Member 2 is judged to be ca 3.3 mya by palaeomagnetic dating. Member 3 is the largest deposit in the Sterkfontein caves and shows localized concentrations of fossil bones on the exposed wall where lime miners have removed a massive stalagmite boss, but it remains unexcavated due to di±culties of access. Member 4 is located in the eastern area of the open breccias exposed at the surface through weathering of the dolomite cave roof and is estimated to date to between 2.14 and 2.4 mya. Member 4 has also produced a large col- lection of Australopithecus and other fossil fauna but has no artefacts. The deposit was originally thought to have ¯lled a large underground chamber and the northeastern part of Member 4 was originally named the Type Site by J.T. Robinson because it had yielded the type specimen of Australopithe- cus transvaalensis (TM1511), now classi¯ed as A. africanus. Member 5 was previously thought to be a single large underground in¯ll, but it has been sub-divided by Clarke and Kuman into the northern StW 53 In¯ll, an eastern Oldowan In¯ll, and Acheulean breccias in Member 5 West and East. This has been the revised stratigraphy to date. This study is aimed at clarifying the stratigraphy and sequence of the younger archaeological breccias in the western area of the Sterkfontein deposits. The goal is to provide a more complete picture of the contents of these deposits. The westernmost breccias in the main excavation were thus further excavated to reveal a cleaner pro¯le from which the sediments could be observed and to increase the sample sizes of materials from these deposits. Di®erent Member 5 breccia types have now been identi¯ed in the western pro¯le. This study argues that younger Member 4 deposits once ¯lled the western area, and Member 5 deposits formed within the space left by collapsed areas of Member 4 breccia. It is likely that Member 4 deposits still exist in the far western parts of the surface excavation area, beyond the current pro¯le exposed in the western face of Member 5. In other words, Member 4 breccia probably once ¯lled the entire ancient chamber, and remnants of it still remain in portions of the western (Member 5) area, while cavities formed through collapse and solution of Member 4 were subsequently ¯lled with Member 5. The mid-Pleistocene Member 6 breccia was also excavated but did not produce artefacts or additional fauna. The previously excavated faunal assem- blage was re-analysed for a more up-to-date taxa composition, adding taxa previously unidenti¯ed. It indicates that this deposit contains grassland en- vironment fauna. The Member 6 and Post-Member 6 In¯lls together contain rich mid- to late-Pleistocene assemblages from diverse environments accumu- lated and modi¯ed by multiple agents. Artefacts from the Post-Member 6 In¯ll are of Middle Stone Age (MSA) period, but they lack MSA diagnostic pieces and include some early Acheulean core types that appear to derive from older, eroded Member 5 breccia. This assemblage, however, di®ers from the Sterkfontein early Acheulean in the higher proportion of small °aking debris, use of quartz as opposed to quartzite as the dominant stone tool making raw material, and the relatively fresher condition of artefacts.