APPLICATION OF GEOSPATIAL TECHNOLOGY IN MAPPING BEDROCK GEOLOGY OF TURNER MOUNTAIN, EAST-CENTRAL MAINE

This undergraduate research project mapped the bedrock geology around Turner Mountain, located approximately 30 miles east of Old Town of Maine, on the USGS Great Pond 7.5' Quadrangle, in early October of 2008. Garmin GPS was used to locate field stops and outcrops. ArcGIS was used to incorporate the data collected in the field into a GIS database that included previous work through a USGS STATMAP bedrock geologic mapping project. ArcGIS was also used to create geologic maps of the area.

The Turner Mountain area is geologically of interest because it is one of only a few areas in Maine containing syenite, and also because the Norumbega fault system (NFS) is well exposed in the area. The Turner Mountain syenite (TMS) is centered in the mapping area. It is a porphyritic, alkaline-rich feldspathic intrusive stock sandwiched within the NFS. Other rock units include two major lithotectonic terranes comprised of Silurian-Devonian metasedimentary rocks of predominantly turbidite, the Kearsarge-Central Maine Synclinorium and the Fredericton Trough; two large Acadian granitic plutons, the Lucerne and Deblois that are located to the south and southeast of the TMS; and a belt of unmetamorphosed sedimentary redbeds, which was deposited in a narrow, pull-apart basin that was created by strike-slip faulting of the NFS. The northwest margin of the Lucerne granite was ductilely sheared to become a 3-km-wide protomylonite-mylonite-ultramylonite zone within the NFS.

A recent geochronologic work on the syenite yielded an age of 411 Ma (unpublished data), indicating it is even older than the Lucerne and Deblois plutons. Our field observations have assisted in gathering evidence to support this dating that the TMS is at fault contact with both redbeds and ductile shear zone, suggesting it is simply a fault sliver that was exhumed from deeper level of the crust, and that was juxtaposed with the young and shallow redbeds by a later, significant reverse reactivation of the NFS.