Ordovician turbidites of the hotham group, eastern victoria: Sedimentation in deep-marine channel-levee complexes

Christopher L. Fergusson, Ray A.F. Cas, Ian R. Stewart

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Abstract

Ordovician successions in the Lachlan Fold Belt of southeastern Australia are dominated by quartz-rich sandstone and mudstone within a monotonous turbidite association. The Hotham Group of the Benambra terrane in eastern Victoria is a typical example. It is 5 km thick and dominated by four facies: amalgamated sandstones, thick-bedded turbidites, thin-bedded turbidites and mudstone, with less abundant chert and black shale. Depositional environments of the Hotham Group and regional relationships indicate that the Ordovician turbidite successions of the Benambra terrane formed in submarine channel-levee complexes developed on a turbidite-covered abyssal plain comparable in size to large modern submarine fans. Amalgamated sandstones and thick-bedded turbidites represent deposition in channels that possess largely unordered, vertical bed-thickness trends, whereas the fine grained facies were probably laid down in levee bank and interchannel environments. Flutes and scours in the channel facies indicate palaeoflow towards the east. This pattern is consistent with the distribution of pelagic facies (i.e. chert and black shale) which are much more common in the northeastern part of the Hotham Group. The southwestern part was therefore more proximal to the ancient continental margin and is characterized by a more differentiated succession with several mudstone horizons. Pelagic sediments are not found associated with any particular facies association as in other ancient successions.

Original languageEnglish
Pages (from-to)1-12
Number of pages12
JournalAustralian Journal of Earth Sciences
Volume36
Issue number1
DOIs
Publication statusPublished - 1 Jan 1989

Keywords

  • Black shale
  • Chert
  • Eastern Victoria
  • Hotham Group
  • Ordovician
  • Turbidites

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