The Yerrapalli Formation is a
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 ...
rock formation consisting primarily of
mudstones that outcrops in the
Pranhita–Godavari Basin in southeastern India.
The Yerrapalli Formation preserves fossils of freshwater and terrestrial vertebrates as well as
trace fossil
A trace fossil, also known as an ichnofossil (; from el, ἴχνος ''ikhnos'' "trace, track"), is a fossil record of biological activity but not the preserved remains of the plant or animal itself. Trace fossils contrast with body fossils, ...
s of invertebrates.
[Yerrapalli Formation]
at Fossilworks.org The
tetrapod
Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids ( reptiles, including dinosaurs and therefore birds) and synapsids ( pelycosaurs, extinct t ...
fauna includes
temnospondyl
Temnospondyli (from Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') is a diverse order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carbo ...
amphibians,
archosauromorph
Archosauromorpha ( Greek for "ruling lizard forms") is a clade of diapsid reptiles containing all reptiles more closely related to archosaurs (such as crocodilians and dinosaurs, including birds) rather than lepidosaurs (such as tuataras, l ...
reptiles, and
dicynodonts
Dicynodontia is an extinct clade of anomodonts, an extinct type of non-mammalian therapsid. Dicynodonts were herbivorous animals with a pair of tusks, hence their name, which means 'two dog tooth'. Members of the group possessed a horny, typicall ...
.
Geology
Most of the Yerrapalli Formation consists of red mudstones. The mudstones were deposited across a
floodplain
A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...
during the
Anisian
In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from million years ago until million years ago. The Anisian Age succeeds the Olenekian Age (part of the Lower Triassic ...
stage of the
Middle Triassic
In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided in chronostratigraphy. The Middle Triassic spans the time between Ma and ...
. Smaller
lenses
A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), ...
of
calcareous
Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.
In zoology
''Calcareous'' is used as an ad ...
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 ...
represent
ephemeral stream
A stream is a continuous body of surface water flowing within the bed and banks of a channel. Depending on its location or certain characteristics, a stream may be referred to by a variety of local or regional names. Long large streams ar ...
s that branched off from the larger channels that were the source of the floodplain sediments.
[ The climate of the region during the time is thought to have been ]monsoonal
A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal oscill ...
with both wet and dry seasons.
The Yerrapalli Formation overlies the Kamthi Formation, underlies the Bhimaram Formation, and is conformable
In mathematics, a matrix is conformable if its dimensions are suitable for defining some operation (''e.g.'' addition, multiplication, etc.).
Examples
* If two matrices have the same dimensions (number of rows and number of columns), they are ...
with both formations. Two members
Member may refer to:
* Military jury, referred to as "Members" in military jargon
* Element (mathematics), an object that belongs to a mathematical set
* In object-oriented programming, a member of a class
** Field (computer science), entries in ...
of the Yerrapalli Formation have been recognized; a lower member consisting of layers of red and purple clay with lenses of pale green clay and an upper member consisting of alternating layers of clay and fine-grained sandstone.[
]
Paleobiota
The paleobiota of the Yerrapalli Formation is similar to that of the overlying Maleri Formation, which also preserves fossils of temnospondyls and archosauromorphs. The main difference between the Yerrapalli and the Maleri faunae is the presence of dicynodonts in the former. The discovery of dicynodont fossils in the Pranhita-Godavari Basin in 1964 was one of the earliest indications that the Yerrapalli Formation represented a distinct paleofauna. Before this discovery, Yerrapalli strata were grouped within the Maleri Formation.[ The dicynodonts of the Yerrapalli Formation are similar to those of the ]Ntawere Formation
The Ntawere Formation is a Middle Triassic (Anisian) geological formation in Zambia, preserving fossils of synapsids, archosaurs, and temnospondyls.
Geology
Several different facies are present in the Ntawere Formation, reconstructing a floodp ...
in Zambia, which also dates back to the Anisian. During the Middle Triassic, what is now India and southern Africa formed one continuous landmass as part of the supercontinent Gondwana.
Synapsids
Reptiles
Amphibians
Fish
See also
* Donguz Formation
The Donguz Formation, Donguz Svita, or Donguz Rocks (russian: Донгузские скалы) is a Middle Triassic geological formation that crops out on the right bank of Donguz River in Orenburg Oblast, Russia, across the settlement of Pervoma ...
, contemporaneous fossiliferous formation of Russia
* Ermaying Formation
The Ermaying Formation is a sedimentary succession of Anisian (Middle Triassic) age. It is found in the Shaanxi Province of China. It is composed of an up to 600 m thick sequence of mudstone and sandstone. It is famous for its fossils of tetrapods. ...
, contemporaneous fossiliferous formation of China
* Manda Formation
The Manda Formation (also known as the Manda Beds) is a Middle Triassic (Anisian?) or possibly Late Triassic (Carnian?) geologic formation in Tanzania. It preserves fossils of many terrestrial vertebrates from the Triassic, including some of the e ...
, contemporaneous fossiliferous formation of Tanzania
* Ntawere Formation
The Ntawere Formation is a Middle Triassic (Anisian) geological formation in Zambia, preserving fossils of synapsids, archosaurs, and temnospondyls.
Geology
Several different facies are present in the Ntawere Formation, reconstructing a floodp ...
, contemporaneous fossiliferous formation of Zambia
* Omingonde Formation, contemporaneous fossiliferous formation of Namibia
References
{{reflist
Geologic formations of India
Triassic System of Asia
Triassic India
Anisian Stage
Mudstone formations
Fluvial deposits
Paleontology in India
Geology of Andhra Pradesh
Formations