Ecca Group - drifting to warmer latitudes

Ecca Group

As Gondwana moved north towards the equator, thick clay and silt beds were laid down in a large sea that occupied the Karoo basin. These sediments now form shales of the Pietermaritzburg Formation. The shales are easily weathered and often present slope stability problems.

Ecca shale 

Ecca shale is typically dark-coloured as they are carbon-rich due to the high vegetation content of the original sediments. Fine bedding or laminations may also be noted, and the shales tend to easily crumbled.
Overlying the shale is a is a thick sequence dominated by light grey sandstones, called the Vryheid Formation. These sandstones were deposited along ancient sandy shorelines behind which lay vast swamplands with numerous Glossopteris plants. Close examination of the sandstones reveal numerous fossilised burrows formed by ancient soft bodied animals. These structures are similar to those formed by sand-burrowing crustaceans today.

 

Distribution of Glossopteris and Lystrosaurus fossils

When southern Gondwana emerged from below the ice, several tree- like plants had evolved. The most dominant plant was the tree like Glossopteris. These plants rapidly colonized the large deltas, where they grew in in extensive swamps. In these swamps, dead vegetation accumulated faster than it could decay. The burial of the vegetation in the swamps eventually formed coal which is mined in the Vryheid area.
 Glossopteris
 Glossopteris leaf
Glossopteris leafs from the Ecca group (near Cedara, KwaZulu-Natal). The original leafs have been oxidised and replaced by iron oxide.
Detailed view of a glossopteris leaf

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