Seismic sequence stratigraphic analysis of the late Tertiary sequences in the Exmouth Sub-basin, Northern Carnarvon Basin, NW Shelf, Australia

Abstract

Sequence stratigraphic analysis of 3-D seismic data from the southeastern margin of the Exmouth Sub-basin in the Carnarvon Basin, NW Shelf, Australia, reveals five sequences or sedimentary cycles in the mid-Oligocene and younger carbonate-dominated section, consisting of forced regressive, (highstand and/or lowstand) normal regressive, and transgressive systems tracts. The base-level curve, constructed using the Sequence Stratigraphic Interpretation System？？ (SSIS) of OpendTect, shows a corresponding cyclic pattern, characterized by a rapid fall followed by a slow rise. The coherency attribute of the top surfaces (21 Ma, 14 Ma, 10.5 Ma, and 3 Ma) of the forced regressive systems tracts shows the erosive nature of the surfaces and the paleo-shelf edge. The 21-Ma surface is characterized by a NNE-trending shelf edge and erosional features almost parallel to the shelf edge. The 14-Ma surface is characterized by thin, channel-like features extending from the NNE-trending shelf. The 10.5-Ma surface, not as erosive as the deeper forced regressive systems tracts, shows lineations, parallel to the very gentle NE-trending shelf. The change in the orientation of the shelf edge from the NNE to NE probably suggests a major change in physical and/or ecologic accommodation. The 3-Ma surface is characterized by dark and rough areas along the lowermost slope and a thin and winding feature that extends across the slope in strike direction. The slope area to the northwest of the thin feature, corresponding to a v-shaped trough, locally appears to be of low coherency.