The first sedimentary sequence deposited on the new basement was the Cambrian to Ordovician Natal Group (490 million years ago).
Structures preserved in these sandstones indicate that the sediments were transported and deposited by rivers that drained highlands to the northeast. Close to their source, in northern KwaZulu Natal, deep valleys were infilled with thick accumulations of boulders and pebbles.
High rainfall, heavy folding and fracturing results in springs. Very high borehole yields on faults.