Makapansgat Limeworks stratigraphy and the singular case of Member X

Lathan, Alf
Warr, Ginette
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Bernard Price Institute for Palaeontological Research, University of the Witwatersrand
Within the infilling sequence of the western Limeworks a newly recognized unit, Member X, lies stratigraphically between the Member 1 massive speleothem and the Member 2 red silts. Member X consists firstly of a subaqueous mammillary layer that is ubiquitous to the whole of the Limeworks. It is succeeded by a series of intercalated clastic sediments and calcite-rich layers that is confined to the area between the Original Ancient Entrance and the Classic Section and which is terminated by a second subaqueous carbonate layer. The evidence suggests that surface sediments were washed into a carbonate-rich pool created by seepage water and, from the presence of several articulated skeletons, the Original Ancient Entrance during this phase appears to have acted as an animal trap. There are a few blocks of Member X to be found in the Limeworks dumps that have been placed in the Member 2 rows but which should be prepared separately. From the evidence of the intercalated carbonate and clastic layers it appears that Member X was deposited slowly at first and then speeded up probably because erosion caused retreat of the entrance. Member X has several unusual features including a unique pseudo-breccia layer of co-deposited calcite-mud formations, deposition of aragonite that increases with height, and calcite-aragonite layers that invert the stratigraphy on overhanging walls and ceilings but not on the floors.
Makapansgat, Member X, stratigraphy, chronology, Kitching