--> Abstract: Characteristics of Lower Tertiary Sedimentary Rocks Along the Eastern Shore of Katmai National Park, Southwest Alaska, by W. S. Houston, F. G. Ethridge, J. E. Warme, and M. H. Gardner; #90987 (1993).

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HOUSTON, WILLIAM S., and FRANK G. ETHRIDGE, Colorado State University, Fort Collins, CO; JOHN E. WARME, Colorado School of Mines, Golden, CO; and MICHAEL H. GARDNER, Bureau of Economic Geology, University of Texas, Austin, TX

ABSTRACT: Characteristics of Lower Tertiary Sedimentary Rocks Along the Eastern Shore of Katmai National Park, Southwest Alaska

Four stratigraphic sections, with a total thickness of 8,400 feet (2,561 m), were measured along sea cliffs in Katmai National Park. The outcrops were mapped by previous workers as the Eocene(?) West Foreland Formation and the Oligocene(?) Hemlock Conglomerate and/or equivalents. The entire section is non-marine, and was deposited in the southern extension of the Cook Inlet Mesozoic-Cenozoic fore-arc basin.

Measured sections of the West Foreland Formation are dominantly cobble and pebble conglomerates containing sandstone lenses, infrequently capped by sandstone and/or siltstone beds. Fining-upward sequences are poorly expressed. Widespread scour surfaces separating multistory, amalgamated channel geometries suggest low accommodation potential on a broad braid plain. Measured sections of the Hemlock Conglomerate consist of pebble conglomerates, sandstones, siltstones and coals arranged in well defined, fining-upward packages. Lithologies include channel and non-channel facies. Higher accommodation potential is indicated by complete preservation of isolated channels, upright trees, and increased soft-sediment deformation, which suggest deposition in isolated, sinuous channels that downcut into overbank deposits. Modern analogs for both depositional settings are found in Katmai National Park.

The lithofacies in these measured sections contrast markedly with type sections of the two formations in the northern Cook Inlet Basin, where the Hemlock Conglomerate is coarser-grained and more quartzose, and the West Foreland Formation is finer-grained and less quartzose. The marked contrast in lithofacies between the northern and southern ends of the basin exemplifies the difficulties of long range lithostratigraphic correlation intectonically active basins.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.