Sedimentology and Stratigraphic Architecture of the Late Permian Betts Creek Beds, Queensland, Australia

Authors

Jonathan P. Allen, University of Nebraska-LincolnFollow
Christopher R. Fielding, University of Nebraska-LincolnFollow

Document Type

Article

Date of this Version

11-2007

Comments

Published in Sedimentary Geology 202:1-2 (November 15, 2007), pp. 5–34; doi: 10.1016/j.sedgeo.2006.12.010 ; Selected papers presented at the Eighth International Conference on Fluvial Sedimentology. Copyright © 2007 Elsevier B.V. Used by permission. http://www.sciencedirect.com/science/journal/00370738

Abstract

The Late Permian Betts Creek Beds form a succession of coal-bearing alluvial-coastal plain sediments in a basin marginal setting within the northeastern Galilee Basin, Queensland, Australia. The unit is ~ 50–60 m in thick­ness at Porcupine Creek National Park where outcrop is laterally continuous for several kilometers. Eight fa­cies have been identified within the formation and can be grouped into 2 facies associations: (A) channel depos­its and (B) floodbasin deposits. The channel association consists of conglomerate (A1) and trough cross-bedded multistorey sandstone facies (A2), both interpreted as deposits of low-sinuosity river systems, tidally influenced fluvial channels (A3), interbedded sandstone and siltstone (A4) interpreted as the abandonment fill of the al­luvial systems, and diamictite (A5) interpreted as debris flows. The floodbasin facies association is composed of sandy siltstone (B1; proximal–distal floodbasin), carbonaceous siltstone (B2; mire), and bioturbated siltstone (B3; estuarine) facies.

The overall sediment body architecture can be resolved into 6 unconformity-bounded cycles interpreted as sequences in the genetic sense, which are sheet-like in geometry and, in general, consist of amalgamated mul­tistorey, multilateral braided fluvial deposits at the base overlain by extensive sheet-like overbank mudstones, carbonaceous shales, and coals. Sea-level change is interpreted as the primary control on the sequence architec­ture of the formation, while the internal stratigraphic architecture, however, varies between sequences and is a function of a combination of sea level, tectonic, and autogenic controls.