Department or Program

Geology

Abstract

The bedrock geology of the Gilead 7.5’ Quadrangle was mapped for a more updated version using digital field mapping methods. This research was funded by the Billings Fund and the Maine Geological Society. Previous studies of this region is the current bedrock map by Moench, Hatch, and Lyons (1983). This study focuses on the plutonic history using thin section, estimated modes of QAP diagrams, and geochemical data from X-ray Fluorescence. The two igneous intrusions in this area of study are the Quartz Diorite Suite and the two-mica granites that are found as sills and plutons. The Quartz Diorite Suite is characterized as foliated synkinematic rocks and are closely related to the New Hampshire Plutonic Series (NHPS) associated with the Piscataquis Volcanic Arc. Data from the study show the close correlations with the Winnesepaukee Tonalite from a previous study conducted on the NHPS by Dorais (2003). The two-mica granites are homogeneous in nature with an abundance of pegmatites and are believed to be an extension of the Sebago Batholith that are Carboniferous to Permian in age. For the two-mica granites, the geochemical data did not correlate as well with Tomascak et al. (1996) data but did have a general trend. Based on the data, the hypothesis surrounding the plutons and tectonic history is explained through two or possibly three tectonic events, the Acadian, Neoacadian, and Alleghanian Orogeny. These finding as well as the new changes in the metasedimentary units have significant implications for regional Appalachian tectonics, and validate the importance of creating a new map.

Level of Access

Open Access

First Advisor

Dyk Eusden

Date of Graduation

Spring 5-2014

Degree Name

Bachelor of Arts

Number of Pages

68

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