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Abstract: Proposed Basin Analysis of the Nutzotin Sedimentary Sequence, Southeast Central Alaska

MANUSZAK, JEFF, Purdue University, Department of Earth and Atmospheric Sciences, West Lafayette, IN

Collisional basins play an important role in understanding the tectonic development of convergent margins. The deposits within collisional basins record the denudation history, sedimentary provenance, and paleogeography of the evolving collisional margin through time. A current debate in the geologic literature concerns the complex accretionary history of the western margin of North America. For example, some authors believe that various terranes along the margin have experienced thousands of kilometers of margin parallel offset, while others interpret little to no displacement of these same terranes. In order to contribute to a better understanding of the margin's growth, this study will investigate the Nutzotin collisional basin, a relatively unstudied basinal sequence within the suture zone between the Wrangellia composite terrane and North America. The study will be a field-based analysis of the structural, sedimentological, and stratigraphic characteristics of the Nutzotin basin.

The Nutzotin sedimentary sequence is an ideal basin for such a study because (1) it can be defined as a collisional basin because of its position between a collisional/accretionary plate boundary; (2) up to 2 km of Jurassic to Cretaceous sedimentary rocks are well exposed; (3) unlike (lie belt of coeval basins which it is a part of, the Nutzotin collisional basin has experienced minimal metamorphism and structural complication; (4) no detailed sedimentological or structural analysis has been completed for this basin; and (5) the results of this study may have regional implications concerning the amount of displacement along the Denali fault system.

The goals of this project will be completed with a combination of fieldwork, lab work, and computer modeling. The proposed field work will include: (1) measuring stratigraphic sections on a bed-by-bed basis through die entire Nutzotin basin; (2) detailed lithofacies mapping; (3) collecting paleocurrent data from pebble imbrication and cross stratification; (4) gathering conglomerate clast count data; (5) collecting sandstone samples for petrographic point count and detrital zircon analysis; and (6) structural mapping at a scale of 1:30,000. This data will be processed in the lab and used to identify vertical and lateral changes in sedimentary facies, depositional environments, deformational history, and sedimentary source terranes. The final stages of the research will compile the field data into a single database where the depositional systems, basin architecture, and subsidence history of the Nutzotin basin will be interpreted. To develop this database while maintaining spatial accuracy, the ArcView 3-13 GIS software will be used.

AAPG Search and Discovery Article #90931©1998 AAPG Foundation Grants-in-Aid