GSA Today
Volume 29, Issue 11

Cover image

Early Jurassic blueschist facies metamorphic rocks from the Raspberry Schist on Kodiak Island, southern Alaska, preserved along the forearc-accretionary complex boundary of the outermost Early Jurassic arc in the Northern Cordillera. The outcrop shows interlayered quartz and Fe- and Mg-rich pelite, interpreted as a chert and mudstone protolith. The coeval development of the arc and subduction complex and later tectonic juxtaposition along the backstop of the Chugach accretionary complex indicate polarity of subduction was dipping east or north in present-day coordinates. Photo by Sarah Roeske.

© The Geological Society of America, Inc.