GEOLOGIC MAP GEODATABASE OF NEWBERRY VOLCANO, OREGON

Geologic mapping of the Pleistocene and Holocene Newberry Volcano in central Oregon is being digitally compiled as a spatial geodatabase in ArcGIS. Within the geodatabase feature classes have been created representing geologic lines (contacts, faults, lava tubes, etc.), geologic unit polygons, and volcanic vent location points. The geodatabase can be queried to determine the spatial distributions of different rock types, geologic units, and other geologic and geomorphic features. These data, in turn, can be used to better understand the evolution, growth, and potential hazards of this very large, rear-arc Cascades volcano. Queries of the database reveal that the total area covered by Newberry Volcano is about 3200 km2, encompassing all or parts of 37 U.S. Geological Survey 1:24,000-scale topographic quadrangles. Deposits from the volcano extend from the Crooked River on the north to the edges of the preexisting Big Hole and Hole-in-the-Ground maars to the south, a distance of about 115 km. Newberry Volcano is roughly 45 km wide at its widest point and spans the area between the Deschutes River on the west and Pine Mountain on the east. A printed version of the preliminary map at its intended publication scale of 1:50,000 is 8 ft high by 3.5 ft wide. The geologic mapping is incomplete, but more than 200 geologic units have been mapped so far. These units represent eruptive events, each commonly including a lava flow and its vent (dome, cinder cone, spatter cone, etc.). Some cinder cones have not been matched to lava flows, as the corresponding flows are probably buried, and some flows cannot be correlated with vents. Plotted map colors are being used to indicate compositions. The largest individual units on the map are basaltic, some extending nearly 50 km to the north through the cities of Bend and Redmond from vents on the low northern flank of the volcano. Andesite units are the least common, with only 13 recognized to date. Silicic lava flows are confined to the main edifice of the volcano, with the youngest rhyolite flows found in and near Newberry Caldera, including the rhyolitic Big Obsidian Flow, the youngest flow at Newberry Volcano (~1300 yr B.P.).