Geological Survey Professional Paper 1033 The Structure of the Olympic Mountains, Washington—Analysis of a Subduction Zone

Cover

Abstract

Introduction
   Summary of regional geology
   Procedure and acknowledgments

Structural geology of the eastern core
   Overview of the structure
      Major rock units
      Faults bounding the core
      Significance of top directions
   Tectonic versus soft-sediment slump structure
   Tectonic fabric
      Cleavage
      Folds
      Pencil structures
      Stretched clast lineations
   Major structural terranes
   Multiple folding
      Early folding—formation of the core units
      Late folding and doming—formation of the pencils
   Summary of the deformation
   Plate margin tectonics

References cited

Supplemental information
   Frequency diagrams for subdomains
   Computerized structural diagram program

FIGURE

1. Sketch map showing major geologic terranes of the Olympic Peninsula

2. Geologic map of the eastern core

3. Sketch map showing major folds and faults on the Olympic Peninsula

4-8. Photographs showing:

4. Beds sheared off by cleavage in zone of disruption, Hurricane Ridge fault zone south of Mount Angeles

5. Block of undisrupted thin-bedded sandstone and slate in broken formation, western Olympic lithic assemblage

6. Shear fold in thin-bedded sandstone with slate core, southwest of Mount Olympus

7. Sheared-off sandstone bed in weakly developed slate, south side Mount Appleton

8. Sketches showing beds in sandstone and slate disrupted by cleavage

9-15. Photographs showing:

9. Blocks and lenses of sandstone in contorted slate matrix, southeast of Muncaster Mountain

10. Tectonic lenses of sandstone in phyllite, southwest side Mount Barnes

11. Small blocks of sandstone in slate, east of Mount Christie

12. Disrupted beds and tectonic lenses in slate, west side Mount Olympus

13. Recumbent fold juxtaposed by faulting with inclined fold, northwest of Grand Pass

14. Sharply hinged fold in sandstone with slate interbeds, northeast shoulder McCartney Peak

15. Fold with rounded hinge in sandstone with siltstone laminations, north side Mount Cameron

16. Sketch showing folded isoclinal fold northwest of Mount Olympus

17. Large overturned drag fold on Mount Anderson

18-23. Photographs showing:

18. Folds in cleavage, phyllite, south ridge Mount Norton

19. Pencil structures in limestone northeast of Grand Pass

20. Pencil structures in slate, northwest McCartney Peak

21. Large pencils in slate and siltstone at high angle to bedding and fold axis, north of Mount Cameron

22. Crude pencils parallel to axial plane of fold northeast of Grand Pass

23. Lineated granule conglomerate, east of Ludden Peak

24-32. Sketches showing:

24. Pencil lineations in the eastern core

25. Domains and subdomains eastern core

26. Principal structural elements for each subdomain

27. Development of eastern core by folding, faulting, and shear folding

28. Ninety-five poles to bedding in volcanic rocks in the Crescent Formation

29. Summary diagrams, structural elements in Domain West

30. Summary diagrams, structural elements in Domain East

31. Intersection of principal shear cleavage, late stage deformation with girdle of early fold axes and constructed kinematic axis

32. Generalized section through Olympic Mountains at plate margin

33. Computer form for structural data

34. Computer output for structural program

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UNITED STATES DEPARTMENT OF THE INTERIOR
CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY
H. William Menard, Director

Library of Congress Cataloging in Publication Data

The structure of the Olympic Mountains, Washington

Geological Survey Professional Paper 1033
Bibliography: p. 24-25.
I. Geology—Washington (State)—Olympic Mountains. I. Cady, Wallace Martin, 1913- joint author. II. Title. III. Series: United States Geological Survey Professional Paper 1033.
QE176.038T3 557.97'94 76-606187

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