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CONTENTS

Abstract
Introduction
          Study Area
          Geologic Setting
          Previous Work on the Short Hill Fault
          Acknowledgments
Stratigraphy
          Middle Proterozoic Basement Rocks
          Late Proterozoic Rocks and Paleozoic Rocks
          Mesozoic Rocks
Structural Elements
          Faults
          Foliations
          Gneissic Foliation
          Lineations
          Folds
Field Relations of the Short Hill Fault
          Central Region
                    Hanging Wall
                    Footwall
                    The Weverton Drill Site and Core
                    Description and Interpretation of Microstructures
          Southern Region
                    Hanging Wall
                    Footwall
                    The Purcellville Drill Site and Cores
          Northern Region
                    Hanging Wall
                    Footwall
                    Elk Ridge Drill Site and Core
                    Rohersville Drill Site and Core
                    Description and Interpretation of Microstructures
          Summary
Kinematics of the Short Hill Fault
Regional Analogies
Tectonic Framework
Relation of the Short Hill Fault and Orogenic Events
References Cited

FIGURES

  1. Geologic map and cross sections of the BR-SMA
  2. Index map of the study area showing the trace of the Short Hill fault and a composite of previously mapped segments of the fault
  3. Maps showing geology, faults and folds, and dominant foliation and lineation orientations.
  4. Equal-area projections of poles to foliation in the footwall and hanging wall blocks of the Short Hill fault
  5. Photographs and illustrations of A cleavage, B phyllonitic foliation, C F2 folds, and D slickenlines
  6. Equal-area projections of lineations (L) and fold axes
  7. Schematic cross section of folds and foliations of the BR-SMA
  8. Geologic map and cross section of the central region
  9. Geologic map of the Hillsboro syncline and equal area projections
  10. Geologic map of the Weverton core site
  11. Structures in the Weverton core
  12. Photomicrographs of the SHF .
  13. Geologic map, cross section, and aeromagnetic image of the southern region
  14. Geologic map of the Purcellville cores.
  15. Geologic map and cross section of the northern region
  16. Geologic maps and cross section of the Elk Ridge core and Rohersville core sites
  17. Photographs of the SHF along Millbrook Creek
  18. Photographs of the SHF
  19. Photographs of A folds and B cleavage
  20. Stratigraphic separation diagrams
  21. Summary structural map of the SHF
  22. Side-looking airborne radar image of the northern and ground-based photographs
  23. Composite cross section and schematic illustration of the SHF
  24. Map-view of the sequence of deformation
  25. Structural map of the SHF
  26. Index map of the BR-SMA showing analogous faults
  27. Geologic map and cross sections of the BR-SMA
  28. Block diagram and schematic cross sections
  29. Tectonic map and schematic restored cross section

TABLES

  1. Geochronology and tectonic history of the BR-SMA, northern Virginia and southern Maryland
  2. Types and distinctive features of foliations and lineations along the Short Hill fault
  3. Relative chronology of deformation events, foliations, and lineations along the Short Hill fault

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