The Ambolafotsy Formation is a
Turonian
The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous Epoch, or a stage in the Upper Cretaceous Series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded b ...
aged
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 ...
in the
Diego Basin of
Antsiranana Province
Antsiranana is a former province of Madagascar with an area of 43,406 km2. It had a population of 1,188,425 (July, 2001). Its capital was Antsiranana. A diversity of ethnic groups are found in the province, including Anjoaty, Sakalava, Antaka ...
in
Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
. It is a mostly terrestrial unit deposited during a marine regression close to the shoreline. The
dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
''
Dahalokely
''Dahalokely'' is an extinct genus of carnivorous abelisauroid theropod dinosaur from the Late Cretaceous (Turonian) of Madagascar.
Discovery
In 2007, during an expedition by Andrew Farke to the north of Madagascar, Joseph Sertich discover ...
'' has been discovered in the formation.
Description
The section containing the Dahalokely site is informally termed the "Ambolafotsy Formation" and is divided into lower, middle (containing the type locality), and upper units. The lower unit has produced several biostratigraphically informative
foraminifera
Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly ...
, including ''
Whiteinella aprica'', ''W. baltica'', ''
Helvetoglobotruncana praehelvetica'', and ''H. helvetica'', and the
nannofossil ''
Quadrum gartneri'', placing the sample within the ''Q. gartneri'' and ''H. helvetica'' zones. The upper unit contains the
ammonite ''
Subprionocyclus neptuni''.
[
The sediments of most of the middle unit of the Ambolafotsy Formation are interpreted as terrestrial, deposited during a marine regression. Carbonized plant fragments are quite common in the middle unit, along with claystones, shales, and cross-bedded sandstones. Marine microfossils and macrofossils are generally absent, although a deposit of ostreids several meters above the type locality for ''Dahalokely'' suggests that the area was deposited close to the shoreline.][Near Ampandriambengy, around the area of Antsiranana]
at Fossilworks.org
See also
* List of fossiliferous stratigraphic units in Madagascar
Several fossiliferous stratigraphic units in Madagascar have provided fossils, most notably the Maastrichtian Maevarano Formation and the Jurassic Isalo III Formation. The oldest fossil-bearing formations date to ages before the break-up of Mada ...
* Geology of Madagascar
The geology of Madagascar comprises a variety of rocks of Precambrian age which make up the larger part of the east and centre of the island. They are intruded by basalts and rhyolites of Mesozoic to Cenozoic age. In contrast, the western part of ...
References
{{reflist
Geologic formations of Madagascar
Cretaceous Madagascar
Paleontology in Madagascar
Upper Cretaceous Series of Africa
Turonian Stage
Shale formations
Sandstone formations
Formations