Emu Bay Shale

The Emu Bay Shale is a lithostratigraphic formation in South Australia, which was deposited in the Cambrian some 525 million years ago BP. Included in it is a significant Konservatlagerstätte ( fossils with soft body preservation ), which leads trilobites from the order of Redlichiida.

The Emu Bay Shale is similar to the Burgess Shale, but he has a higher grain size and thus a total of slightly poorer preservation potential.

Description

The Emu Bay Shale, after its type locality, the Emu Bay, named. This is on the north side of Kangaroo Iceland east from Cape d' Estaing, 35.583333333333137.5Koordinaten: 35 ° 35 '0 "S, 137 ° 30' 0" E in South Australia. The Emu Bay Shale is Australia's only Konservatlagerstätte of Burgess Shale - type.

Stratigraphy and geological framework

The Emu Bay Shale is part of the more than 3500 meters thick expectant upper portion of the Kangaroo Iceland Group, which came to be deposited in a space formed by the active site shifts sedimentation, the Stansbury Basin. The Stansbury Basin was only part of a much weiträumigeren depression area, known as the Adelaide Geosyncline, the sediment content was moved during the Delamerischen orogeny in the direction of the Gawler Craton. The Emu Bay Shale can reach up to 150 meters in thickness and is either concordant or discordant with the White Point Conglomerate. He is eclipsed by the Boxing Bay Formation.

Lithology

The majority of Konservatlagerstätten of Burgess Shale - type were deposited in the deep waters of the outer shelf area. The Emu Bay Shale, however, is a purple -colored shale and seems to have come to the deposition under shallow water conditions ( lagoonal facies ). This leads to the conclusion that took place the soft body preservation in different facies in the Cambrian Period. Some fossils from the Emu Bay Shale show an intense mineralization of the soft body tissue, usually by granular apatite or fibrous calcite. Even phosphatisiertes muscle tissue was detected - so far the oldest find of its kind in the Cambrian. Mineralized soft body tissues are actually rare in the faunal communities of the Burgess Shale - type otherwise.

In shales, there are numerous traces and imprints of trilobites. At its base above the White Point conglomerate leads the Emu Bay Shale, sandy limestones and a Kalklage with Wühlspuren. Along with the White Point Conglomerate it can be correlated with the Oraparinna slate.

Occurrence

There are two significant deposits for the Emu Bay Shale:

  • The profile of the type locality to the east of Emu Bay. It lies conformably on the White Point Conglomerate and contains a rich fauna composed of Balcoracania, Redlichia, Hyolithiden, brachiopods and skleritführenden Chancelloria.
  • The 8 km further east Big Gully locality. The Emu Bay Shale lies unconformably over here to the White Point Conglomerate. In addition to the trilobite fossils occur in soft body condition on, such as the predatory Anomalocaris, Isoxys, Tuzoia, Paleoscolex (probably a string worm), Myoscolex ( problematic assignment) and several rarer finds. The soft body tissues of trilobites was largely mineralized. In a few Redlichia - finds antennas are available.

Fauna

The fauna of the Emu Bay Shale has generally compared to other localities of Burgess Shale - type on a very high number of individuals, but has only a very limited biodiversity. In accordance with other sites Faunengemeinschaft the Emu Bay Shale contains species such as Anomalocaris, Tuzoia, Isoxys, Xandarella and Primicaris; these types can also be in the Chinese Chengjiang Faunengemeinschaft find - palaeogeographic Although at that time relatively close, but this of older age.

Of great importance are also wonderful finds of trilobites such as Redlichia takooensis, Emuella polymerase, Balcoracania dailyi and Estaingia bilobata. The genera Balcoracania and Emuella belong to the superfamily Emuelloidea within the Redlichiina that (over 60 with large Balcoracania - found objects ) are known for a very high number of segments, and also found only in Australia.

Sorted list of the fauna by tribes

Phylum Porifera (sponges )

  • Chancelloria

Master Lobopodia ( Lobopoden )

Master Arthropoda ( Arthropods )

  • Anomalocaris briggsi
  • Anomalocaris sp.
  • Isoxys communis
  • Myoscolex ateles
  • Tuzoia australis
  • Xandarella spectaculum

Master Arthropoda - Class Trilobita

  • Balcoracania dailyi - order Redlichiida
  • Emuella dalgarnoi - order Redlichiida
  • Emuella polymerase - order Redlichiida
  • Estaingia bilobata - order Ptychopariida
  • Redlichia sp. - Order Redlichiida
  • Redlichia takooensis - order Redlichiida

Master Nematomorpha ( hairworm )

  • Paleoscolex antiquus
  • Vetustovermis planus

Photo Gallery

Emuella polymerase

Estaingia bilobata

Redlichia takooensis

Before Present Kangaroo Island List of fossil sites Digital Object Identifier
307832
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