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W. L. Coonrad

Publications and source records attributed to W. L. Coonrad.

At least 19 recordsLinked to original sources
USGS2005

The Togiak-Tikchik complex of southwestern Alaska, a replacement for the Gemuk Group: Stratigraphic nomenclature that has outlived its time

During early exploratory reconnaissance of southwestern Alaska in the 1940s and 1950s, the term "Gemuk Group" was used to name a varied assemblage of sedimentary and volcanic rocks in southwestern Alaska. Throughout the 1950s and early 1960s, the name was broadly applied in the region; yet by the end of the 1960s, it was no longer in use, and later maps assigned the rocks originally in this unit to various informal units and, later, to various terranes. The name "Gemuk Group" is herein abandoned, and the rocks previously assigned to the Gemuk Group, a diverse and structurally complex assemblage, are renamed the "Togiak-Tikchik Complex."

Alaska↗
USGS1978

A tuya in Togiak Valley, Southwest Alaska

The shape, composition, structure, and location of a conspicuous flat-topped mountain in the lower Togiak Valley, southwest Alaska, all indicate that it formed by a subglacial volcanic eruption of olivine basalt. Volcanoes of this type are known as "tuyas." The Togiak tuya erupted into an intraglacial lake in a hole thawed through a glacier that occupied Togiak Valley in Pleistocene time. The eruption was localized along the Togiak fault, which defines the east side of a shallow graben that is floored by older olivine basalt flows. The tuya, which has an area of 15 square kilometers, is a parallelogram. The flat summit, about 300 meters above the valley floor, is capped by glassy, fine-grained subaerial flows of alkali olivine basalt. To the north, the capping flows overlie palagonitized glassy tuffs; to the south, they overlie pillow basalts and breccia. The elevation of the pillow basalts indicates that surface of the melt-water lake was at least 250 m above present-day sea level. Basalt xenoliths in the tuffs and comparison with other better exposed tuyas suggest that the tuffs probably overlie an older pile of subaqueous pillow basalts that erupted beneath the intraglacial lake. The tuya overlies and is much younger than the preglacial flows on valley floor that yielded a potassium-argon age of 0.758±0.2 million years.

Alaska↗