ABSTRACT: The tectonic implications of rapid vertical facies changes in the Yule Island Section, Aure Trough, Papua New Guniea

King, Stuart James¹, David Haig², and Dr. Annette George²
(1) Woodside Energy Ltd, Perth, Australia
(2) The University of Western Australia, Perth, Australia

The Yule Island section is ~1.5km thick and was deposited over ~10.6my from the Middle Miocene to at least the Early Pliocene. Geological mapping and sedimentological and biostratigraphic analyses of the succession highlight six discrete lithofacies associations (LFAs) probably deposited during two separate cycles of tectonic uplift and subsidence within the Aure Trough. The six LFAs identified on Yule Island accumulated in two broad depositional settings; bathyal - characterised by interbedded, turbiditic, sandstone/mudstone lithofacies and low-oxygen, deep-water foraminiferal assemblages; and neritic - characterised by coarse-grained, bioclastic packstone lithofacies and diverse, in situ, shallow water faunal assemblages. Facies associations are repeated within the succession and two depositional 'sequences' are identified. Sequence one had a duration of ~6my, from ~14.8 to ~8.8 Ma, and sequence two had a duration of at least 4.6my, from ~8.8 to (no earlier than) ~4.2 Ma. Both 'sequences' are characterised by rapid and extreme bathymetric variations, which cannot be accounted for by eustatic sea level change. A strong tectonic influence is implied. Important tectonic events recorded within the succession include: 1) development of a proximal foredeep in response to tectonic loading possibly as a result of accretion of the Eastern Papuan Composite Terrane prior to ~14.8 Ma; 2) 'marginal' uplift associated with development and basinward propagation of a fold-and-thrust-belt from ~11.4 Ma; 3) subsidence associated with a second tectonic loading event, possibly accretion of the Adelbert-Finisterre volcanic terrane at ~8.8 Ma; and, 4) pervasive basin-wide uplift associated with development and propagation of a second and younger fold-and-thrust-belt from ~5.2 Ma.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia