INTERPRETATION OF A BASALT FLOW IN THE HONEY LAKE BASIN, SUSANVILLE, CALIFORNIA

Recent geologic mapping of basalt and andesite lava flows has produced a new interpretation of a basaltic lava that flowed into tufa structures. The field area is five miles east of the Susanville Correctional Facility, Lassen County, on the western edge of the Honey Lake Basin and Skedaddle Mountain Range, Northern California. Lake Lahontan covered much of Nevada and northeastern California as early as 30ka (1) and is likely to have produced the tufa mounds where calcium carbonate-rich springs were present. Previous work and new field mapping of these volcanic rocks and the calcareous tufa mounds are used to interpret a northeast to southwesterly lava flow direction, consistent with other local basalts. Field data for this basalt flowing into a wet environment includes hyaloclastite debris, glassy basalt margins, and lava bombs. These observations along with the interfingered basalt and tufa, indicate the lavas were emplaced at the same time the tufas were forming. This, and ongoing work helps to develop our understanding of the style of volcanism and the geologic environment of this region of the Basin and Range province. (1) Bell & House, 2005.