BY LAZARUS KGASI, PALAEONTOLOGY UNIT: DITSONG: NATIONAL MUSEUM OF NATURAL HISTORY
The Haasgat cave system is a fossil-bearing palaeocave that lies in the Monte Christo Formation of Malmani dolomites that forms part of the Schurveberg Mountain Range west of Pretoria (see Fig. 1). The site is 20 km northeast of the well-described early Pleistocene karst systems of Sterkfontein, Swartkrans and Kromdraai. It is located on the Leeuwenkloof 480 JQ farm, positioned between the Gondolin hominin-bearing palaeocave (4 km to the northeast), and the Malapa and Gladysvale australopith-bearing palaeocaves (5-7 km to the southwest). Substantial ex-situ palaeontological sampling by the Geological Survey of South Africa in the late 1980s produced a relatively large and diverse sample of extinct baboon, colobus monkey and ungulate species termed the HGD assemblage (Adams, 2012).
Starting in 2010, a collaboration between palaeontologist, Dr Justin W Adams and geo-archaeologist, Dr Andy I.R. Herries, with Stephany Potze and Lazarus Kgasi of the DITSONG: National Museum of Natural History (DNMNH) renewed excavation at Haasgat with the aim of more reliably determining the age of the deposit, conducting new excavations of the first in-situ deposits, and undertaking a thorough reanalysis of the previously recovered Haasgat HGD fossil sample.
Figure 1. View from the southeast of the locality (the cluster of trees in the centre of the picture marks the cave entrance, with the main dumpsite extending below to the valley floor).
In 1987, palaeontological deposits were first noted in the Haasgat karstic system and led to an initial geological description of the site and faunal study of fossils processed at the site from extensive ex-situ mineral rubble (Keyser, 1991). During the beginning of the 20th century, lime mining had removed a large portion of flowstone, stalagmites and stalactites that formed during a basal collapse and left extensive calcified sediment rubble on the excavated floor of the tube-like excavated cave.
Compared to many of the fossil-bearing palaeocaves in the area, the site is unique in that the present deposit preserves the original structure of the palaeocave (roof, walls and floor), consisting of a long tunnel that was completely filled with breccia, conglomerate and fine-grained laminated sediments and speleothems to the roof. A massive ex-situ dumpsite was generated from the lime mining, which was sampled and processed, yielding a diverse faunal sample (HGD assemblage) that includes the largest and most demographically diverse accumulations of two primate taxa (Papio angusticeps and Cercopithecoides haasgati: see fig. 2) from a single location in South Africa (Adams, 2012). Subsequent sampling from the dumpsites also yielded the first, and thus far only, hominin from the site (Leece et al., 2016).
Figure 2. (1) Cercopithecoides haasgati partial cranium and mandible, lateral view; (2) HGD 2452, cf. Cercopithecoides right mandible, lateral (above), oblique (middle), and occlusal below view. Scale bar equals 1 cm.
Dr Justin W. Adams was instrumental in reviving the history of Haasgat by starting the excavation with the permission from the landowner, the late Phillip Tetley and the community of Kalkheuvel. Many of the historical collection from Haasgat is housed at the Council of Geoscience and they were collected by the late Dr Andre Keiser. Majority of these specimens were still imbedded in breccia with the prefix HGD, meaning they were collected from the dump. Accessing the Haasgat fossil site is difficult because of where the site is positioned on the landscape.
More recent excavations under Dr Adams and Stephany Potze were undertaken with permits secured through SAHRA. All calcified sediment blocks were first recorded with a Leica Nova Multi total station; all blocks of breccia were removed with hand tools and brought back to the DNMNH (the designated repository for new Haasgat fossil materials under the SAHRA permits). Collected breccia blocks were processed at the DNMNH using acetic acid (see Fig. 3). All fossils recovered through processing were sorted and catalogued by methods described by Adams (2006) and DNMNH’s Palaeontology section’s Standard Operating Procedures. Future articles will share more information about the specimens discovered from Haasgat site.
Figure 3: A calcified sediment block from Haasgat being processed at the DITSONG: National Museum of Natural History in Pretoria.
Adams, J. (2012). “A revised listing of fossil mammals from the Haasgat cave system ex situ deposits (HGD), South Africa. .” Palaeontologia Electronica 15(3; 29A): 88.
Keyser, A. W. (1991). “The palaeontology of Haasgat: a preliminary account.” Palaeontologia africana 28: 29-33.
Leece, A., A. D. Kegley, R. S. Lacruz, A. I. Herries, J. Hemingway, L. Kgasi, S. Potze and J. W. Adams (2016). “The first hominin from the early Pleistocene paleocave of Haasgat, South Africa.” PeerJ 4: e2024.