What if I told you that Africa was once in the grip of an ice age? Today we’re standing before the Mamba Valley glacial striations. These striations are silent witnesses to a time when glaciers carved their way across this very landscape.
Around 300 million years ago Durban was part of the supercontinent Gondwana. Gondwana was drifting through the polar regions. Conditions here were much like those Antarctica experiences today. Imagine vast ice sheets grinding relentlessly southward across the continent. They left scars and added character to the African landscape.
These aren’t just any rocks. The Mamba Valley glacial striations are fossilized deposits of glacial till. This bluish-grey rock contains ground-down lumps of granite sandstone and other rocky debris. These piles of rock represent the remains of a prehistoric ice age.
But how do we know this was a glacier? Geologists recognized similarities between these deposits and modern glacial tills in northern Europe. The effects of ice sheets milling the landscape are the same. The only difference is time. Our deposits have had 300 million years to consolidate.
The fine-grained groundmass is fossilized rock flour. It was pulverized by tons of ice juddering across the ancient surface. The Dwyka Tillite contains millions of fragments of sandstone and granite. These fragments were torn from the underlying rock by the bulldozing ice.
More spectacular are the striated pavements. Grooves gouged into the hard sandstone. These grooves were made by the glacier’s bedload as it ground its way across the surface. When the foundations were laid for the new geography building at the University of Durban-Westville a striated pavement was found.
Other examples occur on top of the Natal Table Mountain and on the Hopewell Farm. Dropstones are also visible in the road cuttings on Table Mountain Nagle Dam Road. These boulders rafted out on ice floes and then deposited into the sea floor muds.
Scientists also study the magnetic alignment in ancient lava flows. As lava cools iron minerals align with the magnetic poles. This alignment is preserved. By measuring this scientists can determine the position of the magnetic pole relative to the rock sample. Thousands of measurements reveal patterns of polar wanderings throughout Earth’s history. This helps confirm that southern Africa was once located much closer to the South Pole.
From the Dwyka River in the Cape to Zululand vast deposits of tillite are found. These striations tell a story of continental wanderings. They tell a story of an ice age that gripped us 300 million years ago. The Mamba Valley glacial striations offer a glimpse into a deep and frozen past. They are a reminder that even the most familiar landscapes have hidden stories to tell.