ABSTRACT: Outcrop and Seismic Stratigraphic Criteria for Documenting Relative Sea Level Changes in the Devonian of the Canning Basin, Western Australia

Ward O. Abbott, Robert B. Kirk

Four Devonian (and Carboniferous) unconformity bounded carbonate sequences have been identified by outcrop and seismic sequence analyses: the Pillara, Nullara, Yellow Drum, and Laurel sequences. Each sequence, characterized by a lowstand wedge in a marine onlap setting, probably resulted from a tectonically induced base-level drop with concomitant carbonate platform exposure and incision/bypass. The clastic wedges (lowstand systems tract) are followed by fine grained basin/slope and nearshore carbonate sediments of the transgressive systems tract. These, in turn, are followed by the highstand systems tract with a well-developed carbonate platform, and sometimes a well-established reef facies.

Each sequence is identified on seismic in the Yarrada/Meda and Blina areas of the northern margin of the Canning Basin and some pertinent geometries mapped. The sequence boundary separating the oldest two cycles (Nullara/Pillara) crops out, along with the Nullara lowstand wedge, in the McWhae Ridge area, as well as on the classic face in Windjana Gorge. The latter location clearly depicts the differing highstand character of the early sequences, namely the accreting Pillara sequence vs. the prograding Nullara sequence.

Geometrical analogies are found between these Devonian sequences and Permian carbonate sequences in the Delaware basin of west Texas, Cretaceous/Tertiary sequences in Australia, and Triassic sequences in the Dolomites of northern Italy.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990