Washington Department of Natural Resources Geology and Earth Resources Division Bulletin No. 66 Geology of the Washington Coast between Point Grenville and the Hoh River Weldon W. Rau

Cover

COVER PHOTO—LOOKING NORTHWARD AT THE HOGSBACK AREA. For nearly 2-1/2 miles, the cliffs and promontories are composed of large resistant blocks of chaotically mixed sandstone and volcanic rocks act in a matrix of intensely broken and sheared siltstone. Little Hogsback, center, and Hogsback, in the distance, are very large resistant blocks of volcanic rocks that were left behind as the sea eroded the coastline eastward.

Foreword

Historical notes

Introduction
   Acknowledgements

PART I-ROCK FORMATIONS AND THEIR GEOLOGIC HISTORY

General statement

Volcanic rocks of middle Eocene age

Sedimentary rocks of late Eocene age

The Hoh rock assemblage
   General discussion
   Turbidites of the Hoh rocks
      Sedimentary structures
   Tectonic melange of the Hoh rock assemblage
   Interpretations of structure in the Hoh rock assemblage
      General discussion
      How and why
         Plate tectonics—sea floor spreading
         Piercement structures

The Quinault Formation
   General description
   Major sections of continuous strata
      North of Point Grenville
      South of Taholah
      Cape Elizabeth
      Duck Creek-Pratt Cliff
      Tunnel Island area

Late Cenozoic deposits
   General description
   Origin of sand and gravel deposits
      Ancient wave-cut surface
   Crustal warping and changes in sea level
   Summary of late Cenozoic geologic history

PART II—GEOLOGIC OBSERVATIONS AND INTERPRETATIONS ALONG SEGMENTS OF THE COAST

Selected additional reading

Figure

FRONTISPIECE—Looking north from Point Grenville to Cape Elizabeth

1. Looking eastward at Point Grenville

2. Geologic time chart

3. Dipping beds of well-stratified sandstone and siltstone exposed east of Point Grenville

4. Contorted and disarranged materials in the Hogsbacks area

5. Hogsback, as it appears from the air and offshore

6. Looking northeast at the southern part of Browns Point

7. Looking southwest at well-stratified, steeply dipping beds of siltstone and sandstone near Beach Trail 4

8. Overturned sandstone and siltstone beds at Beach Trail 4

9. Flamelike sedimentary structures indicate that strata are overturned

10. Large resistant boulders on the beach at Boulder Point

11. How rocks of the Olympic Mountains and of the west coastal area may have been formed

12. A continuous seismic profile recorded off the coast near Point Grenville

13. Microscopic fossils, "Foraminifera," from the Quinault Formation

14. Correlations of four major sections of the Quinault Formation

15. Contorted bedding in the Quinault Formation

16. Carbonized branches in massive sandstone near Cape Elizabeth

17. Looking northward at the Quinault Formation, exposed between Cape Elizabeth and the Quinault River

18. A contact between Hoh rocks and the overlying Quinault Formation

19. Elongated concretionlike structures in the cliffs north of Pratt Cliff

20. Disrupted bedding in siltstone of the Quinault Formation, Duck Creek area

21. Sandstone beach pebbles contain many fragments of various rock types

22. Two major sand and gravel units exposed in a sea cliff just south of Whale Creek

23. Red beach sands near Hogsback

24. Tunnel Island, off the mouth of the Raft River

25. Seastacks of sandstone north of Tunnel Island

26. Idealized cross section showing relations between major Pleistocene deposits and the land surfaces

27. Modern (piddock) clam borings

28. Fossil (piddock) clam borings in sandstone strata at Beach Trail 4

29. Point Grenville to Pratt Cliff—coastal map

30. Cross section of scour and fill structures, north of Point Grenville

31. Siltstone interbedded with volcanic rocks at Point Grenville

32. Massive siltstone of the Quinault Formation beneath late Pleistocene outwash, south of Taholah

33. A major landslide area about 1 mile north of Point Grenville

34. Willoughby Rock with mainland in the background

35. A landslide immediately north of Point Grenville

36. Pratt Cliff, viewed from the air

37. Jumbled Hoh rocks in fault contact with the Quinault Formation

38. Remains of a boiler used in 1913 for drilling operations, north of Taholah

39. Looking northward at high, nearly vertical cliffs, extending northward from Cape Elizabeth

40. Sandstone and conglomerate cliffs of the Cape Elizabeth area, about 1900

41. Cape Elizabeth, looking northwestward, 1972

42. Contorted Hoh rocks near Duck Creek

43. Looking northward at Cape Elizabeth, 1970

44. A view taken about 1902, looking northward at strata of Cape Elizabeth

45. Pratt Cliff to the Queets River—coastal map

46. Steeply dipping, well-stratified beds, immediately north of Hogsback

47. Looking westward through the tunnel beneath Tunnel Island

48. Split Rock

49. Little Hogsback, a resistant mass from jumbled Hoh rocks

50. Elephant Rock, at the south end of Tunnel Island

51. A pectenlike fossil in the sandstone of Tunnel Island

52. A distorted stump, in carbonaceous clay and silt, exposed in the cliff, north of Whale Creek

53. Piercement structure between Cape Elizabeth and Duck Creek

54. Destruction Island has a foundation of steeply dipping sandstone strata

55. Looking northward at the coastline between Whale Creek and the Queets River

56. Crossstratification in beds of sand and fine gravel, north of Whale Creek

57. Highly carbonaceous clay beds exposed in the bluffs north of Kalaloch

58. Looking easterly at the Kalaloch rocks

59. Queets River to Beach Trail 4—coastal map

60. Looking northward in the Browns Point area

61. Well-formed groove casts on the bottom side of a nearly vertical dipping sandstone bed on Destruction Island

62. Beach Trail 4 to the Hoh River—coastal map

63. Two major units of sand and gravel exposed in the cliffs immediately north of Beach Trail 6

64. Looking northward at steeply dipping sandstone strata at Browns Point

65. Starfish Point, just north of Beach Trail 4

66. Unstratified deposits of clay, silt, sand, gravel, and boulders exposed at Beach Trail 7

67. Looking north across a boulder-strewn beach near Beach Trail 6

68. South Rock, offshore between Beach Trail 7 and Ruby Beach

69. A close-up view of the bedrock of Abbey Island

70. Looking northward from the Abbey Island area

71. Abbey Island with Hoh Head in the distance

72. Colorful deposits of sand and gravel, about one mile south of the Hoh River

Photography by the author unless otherwise indicated.

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STATE OF WASHINGTON

DEPARTMENT OF NATURAL RESOURCES
BERT L. COLE, Commissioner of Public Lands
DON LEE FRASER, Supervisor

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GEOLOGY AND EARTH RESOURCES DIVISION
VAUGHN E. LIVINGSTON, JR., State Geologist

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Bulletin No. 66
GEOLOGY OF THE WASHINGTON COAST
BETWEEN
Point Grenville and the Hoh River

Part I.—Rock Formations and Their Geologic History
Part II.—Geologic Observations and Interpretations Along Segments of the Coast

A review of the geologic processes and events responsible for the forming of the rock formations and deposits along the Washington Coast

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BY
WELDON W. RAU
Geologist

1973
(Reprinted, 1975)

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