geological formation
A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...
of the mid-
Triassic
The Triassic ( ) is a geologic period and system (stratigraphy), system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Year#Abbreviations yr and ya, Mya), to the beginning of the Jurassic Period 201.36 ...
Cabora Bassa Basin and Mana Pools Basin of southern Africa, consisting mainly of
sandstone
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks.
Most sandstone is composed of quartz or feldspar (both silicates ...
.
Description
Stratigraphy
The Angwa Sandstone is the lowest formation in the
Upper Karoo Group
The Upper Karoo Group is a sequence of Triassic to Early Jurassic sedimentary and volcanic rocks found in Botswana, Zambia, and Zimbabwe.
It comprises the Escarpment Grit (in the Mid-Zambezi and Limpopo basins) and the Angwa Sandstone (in the M ...
of the
Karoo Supergroup
The Karoo Supergroup is the most widespread stratigraphic unit in Africa south of the Kalahari Desert. The supergroup consists of a sequence of units, mostly of nonmarine origin, deposited between the Late Carboniferous and Early Jurassic, a peri ...
, underlying the
Pebbly Arkose Formation
The Pebbly Arkose Formation is a Late Triassic geologic formation found in southern Africa.
Geology Description
The formation comprises mainly coarse, arkosic sandstones.
Extent
The Pebbly Arkose Formation is found in Botswana, Zambia and ...
and overlying the Lower Karoo Group. The formation is divided into two members: the Alternations Member and the Massive Sandstone (Chirambakadoma) Member.
The Angwa Sandstone has been correlated to the
Molteno Formation
The Molteno Formation is a geological formation found in several localities in Lesotho and South Africa. It lies mainly south of Maseru, near Burgersdorp, Aliwal North, Dordrecht, Molteno, and Elliot. It extends as far north as Matatiele in the ...
of the Great Karoo Basin, South Africa, and to the Escarpment Grit of the Mid-Zambezi Basin.
Lithology
The formation is a sedimentary unit, consisting mainly of fluvial sands and silts.
It has been dated as covering rocks from much of the Triassic, with pollen and flora identified from the
Induan
The Induan is the first age of the Early Triassic epoch in the geologic timescale, or the lowest stage of the Lower Triassic series in chronostratigraphy. It spans the time between 251.902 Ma and Ma (million years ago). The Induan is sometime ...
, and
Ladinian
The Ladinian is a stage and age in the Middle Triassic series or epoch. It spans the time between Ma and ~237 Ma (million years ago). The Ladinian was preceded by the Anisian and succeeded by the Carnian (part of the Upper or Late Triassic ...
Mozambique
Mozambique (), officially the Republic of Mozambique ( pt, Moçambique or , ; ny, Mozambiki; sw, Msumbiji; ts, Muzambhiki), is a country located in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi ...
,
Zambia
Zambia (), officially the Republic of Zambia, is a landlocked country at the crossroads of Central, Southern and East Africa, although it is typically referred to as being in Southern Africa at its most central point. Its neighbours are t ...
,
Zimbabwe
Zimbabwe (), officially the Republic of Zimbabwe, is a landlocked country located in Southeast Africa, between the Zambezi and Limpopo Rivers, bordered by South Africa to the south, Botswana to the south-west, Zambia to the north, and ...