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 expo ...
of the mid-
Triassic
The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...
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 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 pe ...
, 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 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 of the Great Karoo Basin, South Africa, and to the
Escarpment Grit
The Escarpment Grit is a Triassic geologic formation. It is also referred to as the Nyoka Grit.
Geology
The formation is composed of fluvial sediments, mainly gritstones and coarse sandstones. Uranium is present in the Escarpment Grit of southern ...
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 somet ...
, 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) ...
to
Norian
The Norian is a division of the Triassic Period. It has the rank of an age ( geochronology) or stage (chronostratigraphy). It lasted from ~227 to million years ago. It was preceded by the Carnian and succeeded by the Rhaetian.
Stratigraphic ...
.
Occurrence
The Angwa Sandstone Formation is found in
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, Mala ...
,
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 ...
,
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 Mozam ...