The Sankarewang Formation is an ?

Early Early may refer to: Places in the United States * Early, Iowa, a city * Early, Texas, a city * Early Branch, a stream in Missouri * Early County, Georgia * Fort Early, Georgia, an early 19th century fort Music * Early B, stage name of Jamaican d ...

Middle Eocene The Eocene ( ) is a geological epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''Ēṓs'', ' Dawn') a ...

-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 expo ...

Sumatra Sumatra () is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the list of islands by area, sixth-largest island in the world at 482,286.55 km2 (182,812 mi. ...

, Indonesia near Padang. It is among the very few Paleogene fossil deposits from Southeast Asia that preserves a freshwater ecosystem, and contains many of the earliest records of freshwater fish taxa that now predominate the region. Many of the fishes from this formation are well-preserved as articulated skeletons. The fossils of the formation have been known since the 1870s, although they only received significant attention during the 1930s and again starting from the mid-2010s. The age for this formation has long been disputed, with suggested ages ranging from the Cretaceous to the Miocene. Although the exact age still remains uncertain, most recent studies have settled on a tentative Paleogene age, with estimates ranging from the Paleocene to the Oligocene. More recently, Palynology, palynological data suggests that the overlying Sawahlunto Formation is of middle-late Eocene in age, which would most likely place the Sangkarewang Formation in the early-mid Eocene. It was deposited within the Ombilin Basin, a small Paleogene-aged Rift, rift basin that formed from deformation along the Great Sumatran fault. The Sangkarewang Formation was deposited within a freshwater rift lake that formed in this basin early on, with Anoxic waters, anoxic bottom waters allowing for the fossilization of the fish skeletons. The Sawahlunto Formation, long exploited for its Coal mining, coal seams, was later deposited in the lake on top of the Sangkarewang Formation. During the Oligocene, this gave way to a river delta (the Sawahtambang Formation), and was later flooded by the sea by the Miocene (the Ombilin Formation), before a tectonic uplift raised it above the sea. The formation has been explored for its Oil shale, oil shales.

Paleobiota

Bony fish

Partially based on Woodward (1901) & Sanders (1934). Sanders (1934) published a comprehensive monograph about the fishes of the formation using a large number of specimens. However, the vast majority of these specimens are now lost, and may have potentially been destroyed during World War II, preventing any further study of her specimens.

Birds

References

{{Reflist Eocene Asia Eocene Series Paleontology in Indonesia Oil shale formations