File:Siltstone turbidites in Stephens Passage Group.jpg

Summary

Stephens Passage Group sedimentary rocks of Marsh Island(Cretaceous): Volcaniclastic sandstone and siltstone turbidites, mudstone, clast-supported conglomerate, and matrix-supported debris flows. Generally coarser grained and more proximal facies than other Seymour Canal Formation rocks. Conglomerate clasts are dominantly sedimentary lithics, including chert, sandstone, mudstone, and limestone. Point counted sandstones contain dominantly volcanic lithics (Cohen, 1992). Marsh Island sandstones contain considerably less quartz than the Seymour Canal Formation sandstones on Zarembo and Kupreanof Islands. Unit contains Berriasian and Valanginian buchias and Albian ammonites. One locality has Kimmeridgian to Tithonian buchias. Includes dikes and thin pillow basalt flows of KJsv. Early Albian ammonites reported from Marsh Island (Berg and others, 1972; Cohen and Lundberg, 1993; Table 1). Marsh Island and western Etolin Island.

Copyright status:

This image is public domain because it was first published by the U.S. Geological Survey

Source:

http://pubs.usgs.gov/of/1999/of99-168/of99-168-pamphlet.html