The Oscar Range is a small, low mountain range in

the Kimberley The Kimberley is the northernmost of the nine regions of Western Australia. It is bordered on the west by the Indian Ocean, on the north by the Timor Sea, on the south by the Great Sandy Desert, Great Sandy and Tanami Desert, Tanami deserts in t ...

region of

Western Australia Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...

. It is approximately 40 km long and 6–8 km wide. The range sits on the edge of the Lennard Shelf. It consists of

precambrian The Precambrian ( ; or pre-Cambrian, sometimes abbreviated pC, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of t ...

metamorphic Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causi ...

quartzite Quartzite is a hard, non- foliated metamorphic rock that was originally pure quartz sandstone.Essentials of Geology, 3rd Edition, Stephen Marshak, p 182 Sandstone is converted into quartzite through heating and pressure usually related to tecton ...

s and

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...

s folded to produce a trellis type drainage system. Lower hills surrounding the range are made up of carbonates. The range is known for the fossil reefs that surround its peaks. These

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

reefs are exceptionally well preserved. In Devonian times, the peaks of the Oscar Range were emergent as islands. The grouping of islands has been referred to as the Mowambini Archipelago, based on the Aboriginal name for the Oscar Range. The islands were surrounded by

stromatoporoid Stromatoporoidea is an extinct clade of sea sponges common in the fossil record from the Middle Ordovician to the Late Devonian.Stock, C.W. 2001, Stromatoporoidea, 1926–2000: ''Journal of Paleontology'', v. 75, p. 1079–1089. They can be cha ...

reefs, which have now been exposed by erosion.

References

{{reflist, 30em, refs= {{cite web , url = http://www.bonzle.com/c/a?a=p&p=4229&cmd=sp , title = Map of Oscar Range in Western Australia , publisher = bonzle.com , accessdate = 2014-01-08 {{cite journal, journal = The Journal of Geology , volume = 115 , number = 5 , pages = 583–600 , url = http://eprints.qut.edu.au/14230/ , accessdate = 2014-01-08 , title = Outer Rocky Shores of the Mowanbini Archipelago, Devonian Reef Complex, Canning Basin, Western Australia , author1 = Johnson, Markes E. , author2 = Webb, Gregory E. , year = 2007 , publisher = Williams College , doi=10.1086/519779, bibcode = 2007JG....115..583J , s2cid = 129190899 Mountain ranges of Western Australia Kimberley (Western Australia)