Document Type

Thesis

Abstract

Structural features within the Columbia 7.5’ quadrangle extend north and south making the geology and age relations of these features paramount in understanding the broader geologic setting. Two metasedimentary belts crop out in the western Columbia quadrangle which are interpreted as part of the Arvonia Formation, a suite of quartzite, schist, phyllite and metagraywacke. From prior work it is unclear exactly what the contacts and age relations are between the Columbia granodiorite and the two metasedimentary belts. Regional mapping in this area has suggested that these two sedimentary belts are simple synclinal structures and either overlying or intruded by granodiorite, a more detailed look at the structural geology in this area provides a better explanation of the contacts and age relations. Detailed research in the study area reveals minimal differences in metamorphic grade and distinct differences in the degree of deformation between the two belts, and an insignificant distinction in lithology. Evidence suggests that the two metasedimentary belts are not isochronic. One metasedimentary belt is truncated by the granodiorite while the other unconformably overlies it. The northern belt, Long Island syncline, consists of a series of inclined folds with axes roughly trending 200° and plunging 45°. The southern belt, Arvonia syncline, is an asymmetric fold with an axis roughly trending 220° and plunging 20°. This research will also examine a stock of hornblende diorite located within the Long Island syncline recognized by Smith and others (1964) but neglected by Rader and Evans (1993) on the Virginia State Map.

Date Awarded

2002

Department

Geology

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