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Terranes of the Tumut District, Southeastern New South Wales, Australia

Basden, H ; Franklin, B. J ; Marshall, B ; Waltho, A. E Leitch, Evan C ; Scheibner, Erwin

Terrane Accretion and Orogenic Belts, 1987, p.57-66 [Periódico revisado por pares]

Washington, D. C: American Geophysical Union

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  • Título:
    Terranes of the Tumut District, Southeastern New South Wales, Australia
  • Autor: Basden, H ; Franklin, B. J ; Marshall, B ; Waltho, A. E
  • Leitch, Evan C ; Scheibner, Erwin
  • Assuntos: Geology, Structural ; Orogeny
  • É parte de: Terrane Accretion and Orogenic Belts, 1987, p.57-66
  • Descrição: The Tumut Region of the Lachlan Fold Belt of southeastern New South Wales, has traditionally been interpreted in terms of intra‐arc rifting to form the Tumut Trough, followed by rift‐basin closure and inversion as part of the accretionary process. Implicit in this tectonic model is the notion that the relative position of all rock bodies, other than ophiolite slivers, was the same in the Late Silurian as it is today; that is, the rock bodies are parautochthonous. A dearth of “hard” palaeomagnetic, palaeobiogeographic and radiometric data, however, allows allochthonous interpretations and requires that terranes of the region be designated “suspect”. Five suspect terranes are recognised on the basis of lithostratigraphic, structural and metamorphic evidence, plus some radiometric dating and limited fossil data. The terranes are the Wagga‐Omeo, Tumut, Jindalee, Mooney Mooney, and Young terranes. Both the Jindalee and Tumut terranes are now composite and, perhaps with the Mooney Mooney terrane, may have formed a single composite terrane on which the Silurian Tumut Trough sequence was deposited as an overlapping assemblage. This would suggest terrane dispersion and amalgamation before the emplacement of Early Devonian stitching plutons and overlapping volcanics. The principal faults delimiting the terranes are the Gilmore fault zone, the Cootamundra‐Gundagai‐Killimicat fault system, and the Mooney Mooney fault system. Mapping suggests that the structures are steeply dipping, but the amounts and nature of displacements are generally unresolved, since they have mainly been determined from stratigraphic arguments based on a parautochthonous rift‐basin model. Such displacement data are only as strong as the tectonic model. However, on the eastern branch of the Mooney Mooney fault system, kinematic indicators within mylonites suggest that the structure is an east‐dipping, high angle reverse fault with a right lateral component. This is consistent with west–southwest thrusting of the Young terrane over the Mooney Mooney terrane. Major geophysical contrasts occur across the Gilmore fault zone. Geophysical data also support a high angle reverse fault interpretation of the Mooney Mooney fault system. It is unclear, however, as to whether or not the steeply dipping (at surface) faults pass down into a flat‐lying thrust system, but it is anticipated that at least the Tumut, Jindalee, Mooney Mooney, and Young terranes are interpreted slices above a major plane of delamination. This interpretation is consistent with a thrust‐tectonic, allochthonous model of amalgamation and accretion, and is opposed to the rift basin model of the Tumut Trough.
  • Editor: Washington, D. C: American Geophysical Union
  • Idioma: Inglês
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