Emu Bay shale

Emu Bay shale

infobox Rockunit


caption = North Coast of Kangaroo Island, Emu Bay
© David Simpson
type = Geological formation
prilithology = Shale
otherlithology =
namedfor =
namedby =
region = The north coast of Kangaroo Island, around Emu Bay and Cape D'Estaing
country =South Australia, Australia.
coordinates = coord|35|35|S|137|30|E|region:AU-SA
unitof =
subunits =
thickness =
extent =
area =
age = Lower Cambrian. ca 525 mya
Stratigraphy: Emu Bay Shale

The Emu Bay Shale is a formation containing a major Konservat-Lagerstätten (fossil beds with soft tissue preservation) - one of two in the world containing Redlichiidan trilobites.

Its mode of preservation is the same as the Burgess shale, but the larger grain size at Emu Bay means that the quality of preservation is lower.citation
author = Glaessner, M. F.
year = 1979
journal = Alcheringa: An Australasian Journal of Palaeontology
volume = 3
issue = 1
pages = 21–31
url = http://www.informaworld.com/index/795083400.pdf
publisher = Taylor & Francis
doi = 10.1080/03115517908565437
]

Description

The Emu Bay Shale of Kangaroo Island, South Australia is Australia's only known Burgess-Shale-type Konservat-Lagerstätte, and includes faunal elements such as "Anomalocaris", "Tuzoia", "Isoxys", "Xandarella", and "Primicaris", in common with other Burgess-Shale-type assemblages, particularly the Chengjiang Fauna in China, the closest palaeogeographically, although somewhat older. The site is also the source of magnificent specimens of trilobites such as "Redlichia takooensis", "Emuella polymera", "Balcoracania dailyi", and "Estaingia (=Hsuaspis) bilobata". "Balcoracania" and "Emuella" are genera of the distinctive "Redlichiina" superfamily "Emuelloidea", known for numerous segments (over 60 in large "Balcoracania" specimens), and so far entirely restricted to Australia.

The depositional environment of the majority of Burgess-Shale-type assemblages is outer shelf, deeper water. The Emu Bay Shale in contrast, appears to represent relatively shallow water deposition, indicating that soft tissue preservation occurred in a range of environmental settings during the Cambrian. Some Emu Bay fossils display extensive mineralization of soft tissues, most often of blocky apatite or fibrous calcium carbonate, but some including the oldest phosphatized muscle tissue and the first thus far reported from the Cambrian. Mineralized soft tissues are apparently rare among Burgess-Shale-type biotas.

The type section of the Emu Bay Shale crops out on the east side of Emu Bay where it conformably overlies the White Point Conglomerate. Here it yields a rich assemblage of "Hsuaspis", "Redlichia", hyolithids, brachiopods, and the scleritome-bearing "Chancelloria". At the Big Gully locality (8 km east of White Point), its presumed correlative is unconformable on the White Point Conglomerate and yields soft-bodied fossils in addition to the trilobites, including the giant predator "Anomalocaris", "Isoxys", "Tuzoia", the presumed worm "Palaeoscolex", the problematic "Myoscolex", and a number of rarer elements. The Big Gully trilobites rarely preserve any trace of non-biomineralized tissue; a small number of specimens of "Redlichia" have been reported with antennae.

See also

* Lagerstätte - other fossil localities
* List of fossil sites "(with link directory)"


References

NOTE: Much of the text of this article was used with permission of Sam Gon III from his below referenced web site, in particular from the [http://www.trilobites.info/Emu.htm Emu Bay page]

See also

References about Australian Trilobites:

External links

* [http://members.tripod.com/~Cambrian/EmuBay2 The Palaeontology of the Lower Cambrian Emu Bay Shale]


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