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ABSTRACT

A regional programme of continuous seismic (boomer) profiling in the central Great Barrier Reef Province has identified a widespread shallow seismic discontinuity (reflector A) which is interpreted as the pre-Holocene surface.

Nine seismic facies units are distinguished primarily on the basis of the seismic records, but also with the aid of additional criteria such as location and surface sediment types. Two units underlie reflector A and are pre-Holocene. These units are interpreted as: (a) Permo-Carboniferous bedrock, and (b) Pleistocene/? Tertiary sediments, consisting of both shelf-wide terrigenous units, and carbonate mounds and platforms under present reefs. Seven units are post-glacial and overlie reflector A. These units are interpreted as: (c) fluvial/estuarine channel fill, (d) relict delta-front deposits, (e) relict transgressive veneer, (f) coastal coarse and (g) fine deposits, (h) modern reef and (i) reef talus.

In general post-glacial sediment cover is very thin and in many places on the mid-shelf the pre-Holocene units crop out. Substantial post-glacial accumulations are limited to protected coastal embayments and to offshore reef masses.