| Summary: | Glacier Bay in the northern part of Southeast Alaska contains a remarkably thick succession of middle Paleozoic (Silurian and Devonian) age strata. The stratigraphic framework for the Paleozoic succession of the Glacier Bay area was established by Rossman (1963), who formally named the Paleozoic formations present in the region. These included from presumed stratigraphic bottom to the top: Willoughby Limestone (late Silurian, about 425 million years old); Tidal Formation (late Silurian); Pyramid Peak Limestone (unfossiliferous, age unknown); Rendu Formation (unfossiliferous, age unknown); and Black Cap Limestone (Middle Devonian according to Rossman, but now known to contain Early Devonian fauna as well). These rocks are all part of the accreted Alexander terrane. In the Alexander terrane, thick Silurian carbonate shelf facies have been mapped from Prince of Wales Island in the south to Glacier Bay in the north. The limestone lithosome was named the Heceta Limestone on Prince of Wales
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