Simplified geological map of the West Coast, with ages of the igneous rocks in millions of years ago (Ma). 

View looking west from the top of ​Blaauwberg Hill, with Malmesbury shale outcrops and a WWII radar station. Recent white, calcareous sand dunes are visible in the distance.

Ferricrete (iron-oxide cemented sand) outcrop in the valley east of ​Blaauwberg.

The underlying bedrock of the BCA is Malmesbury Group shale (the Tygerberg Formation). The Malmesbury shale is the oldest rock in the area and volcanic rocks within it have been dated at Bloubergstrand at 555±5 million years old. The Malmesbury shale is well exposed on ​Blaauwberg Hill, which rises 231 m above sea level. Along with the Tygerberg, which rise to over 400 m above sea level to the east, ​Blaauwberg Hill forms a prominent hill on the coastal landscape. The reason the Tygerberg forms such prominent hills on the landscape is attributed to the intrusion of Cape granite, which has hardened the shale rock and made it more resistant to erosion. ​Blaauwberg Hill does not appear to have any granite intrusions and its resistance to erosion may reflect a greater presence of sandstone rather than shale beds. In the low-lying areas surrounding ​Blaauwberg Hill, the Malmesbury shale is covered with tens of metres of dune sand. The sand dunes are clearly visible along the coast looking west from the top of ​Blaauwberg Hill. These coastal sand dunes are recent and formed in the last tens of thousands of years. In places, the leached shell material has formed sub-surface limestone beds (calcrete). Older sand deposits occur inland on the landward (eastern) side of ​Blaauwberg Hill, and in places these sands have been intensely leached and form quartz-cemented silcrete and iron-oxide-cemented ferricrete outcrops.  
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