Annals of the South African MuseumAnnale van die Suid-Afrikaanse Museum . extensive shell beds on the southern shore on the farms Geelbek, Abrahams-kraal, and Skrywershoek, demonstrate a more southerly extension in the Eem. The lagoon is separated from the Atlantic Ocean by a long ridge thatconnects Ysterfontein with the South Head granites. One can only surmisethat it developed as a prograding spit and tombolo or a barrier-beach its origin, it was reinforced by dune sand accumulation. The presentlagoon is the result of Flandrian flooding of a pre-existing dune landsca
Annals of the South African MuseumAnnale van die Suid-Afrikaanse Museum . extensive shell beds on the southern shore on the farms Geelbek, Abrahams-kraal, and Skrywershoek, demonstrate a more southerly extension in the Eem. The lagoon is separated from the Atlantic Ocean by a long ridge thatconnects Ysterfontein with the South Head granites. One can only surmisethat it developed as a prograding spit and tombolo or a barrier-beach its origin, it was reinforced by dune sand accumulation. The presentlagoon is the result of Flandrian flooding of a pre-existing dune landscape. The Geelbek deposits are a lagoon floor shelly limestone accumulationreaching an elevation of 2 m , and overlain by calcrete. The coquinaincludes quartz porphyry cobbles. Many of the bivalves are still mollusc assemblage is indicative of a shallow, sandy substrate, and con-tains several thermophilic molluscs (Tankard 1975, table 1), for exampleLoripes liratula, Tellina madagascariemis, and Venerupis dura. 104 ANNALS OF THE SOUTH AFRICAN MUSEUM. &/?,&& A Fig. 17. Planation platform on marine limestone, Churchhaven. At Churchhaven a shelly limestone has been locally planed at 1,2 m (Fig. 17). Thin-section examination shows the limestone to consist of 90 percent quartz and 10 per cent detrital shell with drusy calcite cement. All thedetritus is fine-grained and well rounded, and both quartz and shell are exten-sively corroded. Most of the shell grains are molluscan, with only occasionalechinoid spines and foraminifer tests. Figure 18, which shows the growth ofcalcite scalenohedra on the inside of an ostracode carapace (Uroeythereis sp.),demonstrates the extensiveness of diagenesis in these deposits. A layer of mollusc shells contains many articulated shells and unbrokenvalves. They are predominantly shallow water, sand-dwelling forms. Auriladayii and Aglaiella railbridgensis are common ostracodes (Fig. 8, Table 2).Ichnofossils include crab-burrows (
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