Document Type

Thesis

Abstract

The Central Piedmont Fault Zone (CPFZ) contains several NE-SW striking faults. In the Virginia Piedmont this includes the Lakeside Fault Zone (LFZ), the Hylas Zone, and possibly the Spotsylvania Zone (SZ). This study attempts to better understand the kinematics of the SZ, quantify its deformation and understand how it relates to regional geology. Based on kinematic indicators the SZ zone is dextral strike-slip. Subgrain boundaries in porphyroclasts indicate that feldspar began crystal-plastic deformation. Quartz lenses were mostly strain free, already recrystallized. The temperature of deformation ranges from 450- 550°C. Based on PHD analysis the rocks record a vorticity of Wm=0.5, general shear. These data are consistent with dextral transpression across the SZ. In the Mesozoic, brittle faulting occurred along the LFZ and dikes in the area appear dextrally offset. Because exposure is poor, a magnetic survey was completed to constrain the map pattern of these dikes. A dike in the Lakeside Village quadrangle was magnetically mapped. 1000 magnetic readings were taken using a proton-precession magnetometer along a series of traverses. The diabase is highly magnetic compared to the surrounding amphibolite, granitic gneiss, and mylonitic gneiss country rock and showed magnetic relief of up to 1500 gammas. Based on contoured magnetic data a single dike (~10-30 m thick) was recognized. The dike is characterized by two N-striking segments that are linked by a NNE-striking segment. Based on the total magnetic field profile we estimate that dike segments range widely in dip. The magnetic data are inconsistent with dextral offset of the diabase dikes; rather we interpret there to be a single dike with distinct segments of different orientations.

Date Awarded

2001

Department

Geology

Advisor 1

Christopher M. Bailey

Download

Share Feedback

Share

COinS