Department or Program
Updated bedrock geology mapping and geochronology work in the southern portion of the Gilead, Maine 7.5’ Quadrangle provides relevant data in developing the stratigraphy, paleo-depositional setting and geological timeframe of the study area. The revised bedrock map consists of four units (proposed youngest to oldest): Pine Mountain Unit, Bog Brook Unit, Peaked Hill Unit and Chapman Hill Unit. The lithology of the units consists mostly of interbedded schists and quartzites with discontinuous layers of granofels and calc-silicate pods. The units alternate from gray to rusty in appearance. Detrital zircon geochronology of the Bog Brook granofels returned an age of 422 Ma placing the maximum age of deposition within the Late Silurian. Correlation to past work indicates the Bog Brook granofels is equivalent to the Rangeley Formation and supports the previously suggested revision of the traditional ages within the Rangeley Stratigraphy. Crystallization zircon ages of the two-mica granites returned ages of 349 and 355 Ma, Early Carboniferous. The two-mica granite ages constrains the deposition of the metasedimentary rocks, metamorphism and deformation from 422 to 349 Ma, a 73 Ma span. Rusty to gray lithologic contacts within the stratigraphy indicates the depositional basin went through a series of oxic to anoxic transitions while turbidity currents deposited sediments, aiding in understanding the paleo-depositional setting. Through detailed mapping and geochronology this study better constrains the exact stratigraphy, depositional setting and magmatic influences present in the Gilead, ME 7.5’ Quadrangle to further understand both the local and regional geology.
Level of Access
Eusden, Jr., Dykstra
Date of Graduation
Bachelor of Arts
Wheatcroft, Audrey, "Bedrock Geology, Stratigraphy and Geochronology in the Migmatite Terrain of the Southern Gilead 7.5’ Quadrangle, Western Maine" (2017). Honors Theses. 196.
Number of Pages
Components of Thesis
1 zip file (thesis_wheatcroft) containing two PDF documents:
1. the primary written thesis document (thesis_wheatcroft.pdf)
2. the map document (wheatcroft_GileadQuad_map.pdf)
Available to all.