DIGITAL MAPPING WITH UNDERGRADUATES PARTICIPATING IN USGS EDMAP AND STATEMAP PROJECTS: EXAMPLES FROM WESTERN MAINE

With support from the USGS EdMap and StateMap programs, undergraduates at Bates College have begun to incorporate digital techniques as they conduct bedrock geologic mapping for their senior thesis projects. We purchased 20 Trimble Juno SB units to perform the digital fieldwork and initially found using ArcPad to be frustrating. We have now successfully used Trimble’s Pathfinder Office software to develop a data dictionary modeled after the Maine Geological Survey’s mapping protocol. The dictionary includes the following fields: bedding strike and dip; foliation strike and dip; cleavage strike and dip; fold hinge line trend and plunge; fold axial plane strike and dip; fracture strike and dip; basalt strike and dip; lineation trend and plunge; rock ID; and a 50 character comment field. After loading background layers (hillshades, orthos, and/or drgs) and the data dictionary to the Junos in Pathfinder Office, we run TerraSync on the Junos to collect field data. We keep a set of backup hand-written notes that we use frequently for sketches and recording detail beyond the constraints of the data dictionary. Outcrop photographs are taken with our smart phones or digital cameras as the Juno camera is of low quality. Data files are exported from the Junos via Pathfinder Office and then saved as shapefiles on a Panasonic Explorer toughbook running ArcGIS v. 10.1. Given the rugged terrain we work in, bringing the Toughbook into the field is not optimal. In ArcGIS students merge daily files into master data files and draw contacts on their evolving geologic maps. Recent mapping has focused on the Bethel-Gilead-Newry region of western Maine where the bedrock is composed of migmatized Silurian (?) metasedimentary rocks intruded by Devonian (?) diorite-tonalite suites, Devonian to Permian (?) two mica granite, and widespread pegmatites. Preliminary results show that the nine meta-sedimentary units mapped correlate best with the Silurian Rangeley, Perry Mountain, Smalls Falls, and Madrid Formations and not the previously mapped Devonian Littleton Formation. These findings have significant implications for extensions of the stratigraphy into Maine and adjacent New Hampshire. The diorite-tonalite plutons are likely an extension of the Piscataquis Volcanic Arc that formed an integral part of the Acadian Orogeny.