GEOLOGIC MAP OF WRANGELL-SAINT ELIAS NATIONAL PARK AND PRESERVE, ALASKA

We have recently prepared a new geologic map of Wrangell-Saint Elias National Park and Preserve (WRST) in Alaska. Prepared digitally, the map is based on previously published mapping at 1:250,000 scale combined with extensive additions from published and unpublished 1:63,360 scale mapping.

WRST is a geologically unique park as it includes at least 7 tectonostratigraphic terranes that have impinged against North America since about 200 Ma. The oldest rocks in WRST are in the Windy-McKinley (WMK) terrane, which lies north of the Denali fault. Having ~450 km of right lateral offset, the Denali fault juxtaposes Devonian rocks of the WMK terrane against late Mesozoic flysch of the Nutzotin Mountains sequence (NM). The NM was deposited in a deep marine basin as Wrangellia (WR) and associated terranes (Alexander and Peninsular) approached the continent. The WR terrane includes Triassic flood basalt of the Nikolai Greenstone and the marine Chitistone and Nizina Limestone units, as well as the underlying late Paleozoic Tetelna-Skolai magmatic arc. Shield volcanoes of the Tertiary to Recent Wrangell volcanic field, easternmost products of the Aleutian convergent margin, overlie WR. The complex Border Ranges thrust fault system, separates the overriding WR terrane from melange and accretionary rocks of the Mesozoic Chugach terrane. Further south, another system of thrust faults, chief of which is the Contact fault, separates the Chugach terrane and deep sea fan and oceanic volcanic rocks of the Cenozoic Prince William terrane. The Yakutat terrane, the latest terrane to arrive, is bounded on the north by the active Fairweather strike-slip fault and the Chugach-St. Elias thrust fault system. It consists of Tertiary to Pleistocene marine and nonmarine sedimentary rocks and oceanic volcanic rocks and Cretaceous marine flysch probably equivalent to the Chugach terrane.

Digital compilation has facilitated the geologic compilation; in addition it allowed for the creation of a rich database of geologic attributes. Presently, lithology, form (flow, bed, etc.), and age are integral components of the database; planned additions are related attributes including radiometric age and pluton characteristics. In the future, specialized attributes will be added to facilitate Park Service resource management needs.