43 GSA: Accreted Terranes of Western North America: An Update on Current Research on the Construction of the Cordillera III

Wednesday, 10 May 2006
1:20 PM - 5:00 PM

PALEOBIOGEOGRAPHIC ANALYSIS OF UPPER TRIASSIC SCLERACTINIAN CORALS FROM WRANGELLIA AND THE ALEXANDER TERRANE (ALASKA AND VANCOUVER ISLAND, CANADA)

Paper number: 43-3
Program: THEME SESSIONS
Time: 2:00 PM – 2:20 PM

Authors

Abstract

Paleobiogeographic and geological analysis was used to test the idea of amalgamation for Wrangellia and the Alexander terrane in the Carboniferous time period. Analysis of Upper Triassic (Norian-Rhaetian stages) silicified shallow-water corals does not support an amalgamation between these two terranes in the Triassic. An RCSI and PAUP test of silicified coral reveals dissimilarities in species-level faunal composition when comparing coral faunas from the Alexander terrane with northern and southern Wrangellia as well as to the Wallowa terrane and Peruvian Andes (Pucará Group). This study revealed a link between coral faunas of southern Wrangellia (Vancouver Island) and Peru suggesting the possibility for a southern hemisphere or equatorial position for both terranes during the Late Triassic. Mixed paleobiogeographic signals exist when comparing northern Wrangellia (Wrangell Mountains) and the Wallowa terrane. Previous results from Triassic mollusks suggested a link between northern Wrangellia (Wrangell Mountains) and the Wallowa terrane but RCSI tests of the corals did not support this paleogeographic relationship.

Systematic identification of forty-six species (6 new) were generated from 458 coral specimens collected at twelve principle localities from the Norian to Rhaetian limestone units of Keku Strait (Alexander terrane), Gravina Island (Alexander terrane), Wrangell Mountains (Wrangellia), Alaska and Vancouver Island (Wrangellia), Canada. Twenty-six species were recognized from 8 Alexander terrane localities and thirty-two species from four localities within Wrangellia. Nineteen (of twenty-six) species from the Alexander terrane and nineteen (of thirty-three) species from Wrangellia were not previously recognized from these two terranes. Of those nineteen species, ten from the Alexander terrane and eight from Wrangellia were previously only known from the Tethys and now discovered for the first time within the North American Cordillera. Likewise, two species from the Alexander terrane and four from Wrangellia are dated as Carnian. New species from both terranes are consistent with morphological characters from the genera: Gablonzeria Cuif, Margarastraea Frech, Pinacophyllum Frech, Retiophyllia Cuif, and Stylophyllum Reuss.