--> ABSTRACT: Calcareous Nannofossil Biostratigraphy of Chititu Formation, Wrangellia Terrane, Alaska, by William G. Siesser and Bruce C. Panuska; #91030 (2010)

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Calcareous Nannofossil Biostratigraphy of Chititu Formation, Wrangellia Terrane, Alaska

William G. Siesser, Bruce C. Panuska

The tectonostratigraphic terrane ("suspect terrane") concept has been a major catalyst in attempts to unravel the complex tectonic history of Alaska. Paleomagnetic work has suggested that the Wrangellia terrane in south-central Alaska had a paleolatitude of 32°N ± 9° in the Late Cretaceous, but was accreted to North America prior to the Eocene. A plate velocity of at least 24 cm/yr is implied by this latitude and time framework. If confirmed, this velocity will be one of the fastest plate velocities yet established.

Calcareous nannofossils from the Chititu Formation, Wrangellia terrane, have been investigated in order to provide a refined biostratigraphic framework for establishing the age of paleolatitudes determined for the Chititu. Thirty-one species of nannofossils were identified in a section of the Chititu measured on MacColl Ridge. These species allow assignment of the section to the internationally recognized Reinhardtites anthophorus (CC 15: late early to late Santonian) and Lucianorhabdus cayeuxii (CC 16: late Santonian to earliest Campanian) biozones. Calcareous nannofossils clearly have potential for use in age determinations in Wrangellia and other Alaskan tectonostratigraphic terranes with suitable marine sedimentary sections.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.