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The AAPG/Datapages Combined Publications Database

Journal of Sedimentary Research (SEPM)

Abstract


Journal of Sedimentary Petrology
Vol. 36 (1966)No. 3. (September), Pages 719-732

Carboniferous Subaqueous Mass-Movement in the Manning-Macleay Basin, Kempsey, New South Wales

John F. Lindsay

ABSTRACT

An origin by subaqueous mudflows is proposed for unsorted sediments previously considered to be tillites. These sediments are in the Carboniferous Kullatine Formation at the northern end of the Manning-Macleay Basin in northeastern New South Wales. The lensoidal nature of the beds and the general lack of lateral continuity of the tilloids as a whole, along with the presence of large contorted masses of underlying sediments, makes it difficult to accept the earlier hypotheses. Grain size distribution, roundness, sphericity, and composition of the tilloid and water-sorted sediments show marked similarities and support a mass-movement origin for the tilloid by suggesting local mixing of the water-sorted sediments.

Linear elements in the fine fraction and the contorted masses of sediments contained in some beds suggests that a small number of the mudflows traveled in a laminar fashion; however, the majority of the mudflows probably traveled in a turbulent manner. Viscosity, controlled by the proportion of sand in the fine fraction of the mudflow, appears to be the factor controlling the flow mechanism. Pebble fabric data indicates that orienting forces in a subaqueous mudflow act on the broad faces and long edges of the pebbles, rather than on the long axes. In a fabric diagram, the long axes of the pebbles are contained in a broad girdle that dips in an upflow direction. Thin ends of most of the pebbles point upflow.

Approximately 4 percent of the sediments of the Kullatine Formation were involved in subaqueous mudflows. This figure represents a total of about 5.5^times1010 cubic meters of consolidated sediment.


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