The Dwyka Group includes the sedimentary

Sedimentary rock

Sedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution....

 geological formations found in Karoo Basin region of Southern Africa

Africa

Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

.

In the Eastern Cape Province the Karoo Basin fill commenced with the deposition of the Dwyka Group, followed by the Ecca Group

Ecca Group

The Ecca Group is the name given to the sedimentary geological formations found in Karoo Basin region of Southern Africa. It consists mainly of shales and sandstones, laid down in the sandy shorelines of swamplands, during the Permian Period....

, the Beaufort Group

Beaufort Group

The Beaufort Group is the third of the main subdivisions of the Karoo Supergroup of geological strata in Southern Africa. It follows conformably after the Ecca Group and consists essentially of sandstones and shales, deposited in the Karoo Basin from the Middle Permian to the early part of the...

, the Molteno

Molteno Formation

The Molteno Formation is a palaeontological formation of the Stormberg Group, located in the main Karoo Basin, South Africa. It dates to the Upper Triassic period and is rich in fossils....

, Elliot

Elliot Formation

The Elliot Formation is a geological formation dating to roughly 210 to 190 million years ago and covering the Norian to Sinemurian stages. The Elliot Formation is found in South Africa and Lesotho and is a member of the Stormberg Group. It consists mainly of limestone, sandstone, and mudstone...

, and Clarens Formation

Clarens Formation

The Clarens Formation is a prominent fossil site in the Tuli Basin, in the KwaZulu-Natal region of South Africa.-Fauna of the Clarens Formation:Unidentified dinosaur eggs have been recovered from the formation.-Bony fish:-Dinosaurs:-Synapsids:...

s and the igneous Drakensberg Group. The basin followed the typical evolution of foreland basin

Foreland basin

A foreland basin is a depression that develops adjacent and parallel to a mountain belt. Foreland basins form because the immense mass created by crustal thickening associated with the evolution of a mountain belt causes the lithosphere to bend, by a process known as lithospheric flexure...

s, with the Ecca Group representing the ‘flysch

Flysch

Flysch is a sequence of sedimentary rocks that is deposited in a deep marine facies in the foreland basin of a developing orogen. Flysch is typically deposited during an early stage of the orogenesis. When the orogen evolves the foreland basin becomes shallower and molasse is deposited on top of...

’ component and the Beaufort Group, the overlying Molteno and Elliot Formations representing the ‘molasse

Molasse

The term "molasse" refers to the sandstones, shales and conglomerates formed as terrestrial or shallow marine deposits in front of rising mountain chains. The molasse is deposited in a foreland basin, especially on top of flysch, for example that left from the rising Alps, or erosion in the Himalaya...

’-fluvial type sediments.

During the Late Carboniferous the lithosphere underlying the present day Karoo Supergroup migrated over the South Polar Region. This resulted in southern Gondwana being covered by a major ice sheet. Glacial deposits resulted in the Dwyka Group which includes diamictite

Diamictite

Diamictite : through and µεικτός : mixed) is a poorly or non-sorted conglomerate or breccia with a wide range of clasts, up to 25% of them gravel sized...

, varved

Varve

A varve is an annual layer of sediment or sedimentary rock.The word 'varve' is derived from the Swedish word varv whose meanings and connotations include 'revolution', 'in layers', and 'circle'. The term first appeared as Hvarfig lera on the first map produced by the Geological Survey of Sweden in...

 shale

Shale

Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...

 and mudstone

Mudstone

Mudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...

with dropstones, fluvioglacial gravel and conglomerate. The formation ranges in thickness from 600 m to 750 m.

The Dwyka Formation is considered to be Permo-Carboniferous in age, but due to ambiguities in the fossil record, a more precise dating is not available. Maximum age inferred from fossils found in underlying strata is Late Devonian or Early Carboniferous, and minimum age inferred from fossils in the upper glacial deposits is Early Permian.