A 1:100,000-SCALE MAP OF SURFICIAL DEPOSITS IN GLACIER BAY NATIONAL PARK AND PRESERVE, SOUTHEAST ALASKA

During the last glacial maximum all but the highest peaks of this >13,000 km2 area were covered by ice. Much of the record of this glaciation was erased or buried by an extensive Neoglacial readvance that covered most of the lowland areas. Continuing retreat of this ice has left a wide range of glacial and related deposits that have been mapped in detail in only a few places. We have produced a map in a GIS that is intended for publication at the 1:100,000-scale of the surficial deposits of the lowland areas of the park and adjoining areas (specifically, the Icy Strait islands and the area of Canada that drains into the Bay proper) at the request of the National Park Service. The map has been compiled from previous, more localized, mapping efforts and from original mapping by us. Limited by budget, we relied upon aerial photographs, which were generally viewed in a non-stereo manner. Our preference was generally for the 1948 set of images as they largely cover the park and include the least amount of vegetation, but more recent images, such as the 1996 Digital Orthophoto Quarter Quadrangles, were used as well. We first classified map units into one of three categories based on their age (I – Modern/Active, II – Neoglacial/Holocene, or III – Pleistocene) and then subdivided them based on their interpreted genesis (e.g. outwash, beach, till, ice-contact stratified). The map is accompanied by a “user’s guide” that explains the park’s surficial geology in a manner understandable to educated non-experts such as park managers, scientists from non-geological fields, and the general public while preserving the technical details desired by geologists. The collective result is a product that will serve as a first stop for those interested in learning about Glacier Bay’s dynamic landscape history.