Makah Formation--A Deep*Marginal*Basin Sedimentary $Equence of Late Eocene and Oligocene Age in the Northwestern Olympic Peninsula, Washington
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Makah Formation--A Deep*Marginal*Basin Sedimentary $equence of Late Eocene and Oligocene Age in the Northwestern Olympic Peninsula, Washington GEO :LdXHCAL SURVEY P R OF E S SI O N A L P A P E R I 1 i6 2 - B Makah Formation--A Deep-Marginal-Basin Sequence of Late Eocene and Oligocene Age in the Northwestern Olympic Peninsula, Washington By P.O. SNAVELY, JR., A.R. NIEM, N.S. MAGLEOD, J.E. PEARL, and W.W. RAU SHORTER CONTRIBUTIONS TO STRATIGRAPHY GEOLOGICAL SURVEY PROFESSIONAL PAPER 1162-B A study of stratigraphy, petrology, paleontology, and paleogeology of a marine sedimentary sequence of the Olympic Peninsula UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1980 UNITED STATES DEPARTMENT OF THE INTERIOR CECIL D. ANDRUS, Secretary GEOLOGICAL SURVEY H. William Menard, Director For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS Page Page Abstract. ........................... 1 Physical characteristics Continued Introduction................................1 Falls Creek unit.....................15 Acknowledgments.............................2 Unnamed sandstone unit............... 15 Geologic setting and contact relations......3 Petrography................................ 15 Physical characteristics....................7 Reservoir potential of turbidite Baada Point Member.......................9 sandstone members........................ 16 Dtokoah Point Member.................... 12 Age and regional correlations.............. 17 Carpenters Creek Tuff Member............ 12 Depositional environment...................21 Klachopis Point Member.................. 13 Paleogeology...............................22 Third Beach Member...................... 13 Paleodispersal pattern..................24 Jansen Creek Member..................... 14 Source areas ............................25 Other units............................. 15 Summary....................................26 References cited...........................27 ILLUSTRATIONS Page Figure 1. Sketch map of northern Olympic Peninsula showing area of report and distribution of upper Eocene and Oligocene strata.......................................................................2 2. Generalized bedrock geologic map of the northwest Olympic Peninsula showing the relation of the Makah Formation to other Tertiary units....................................................4 3. Generalized geologic map showing the distribution of the Makah Formation at its composite reference section along the Hoko River...........................................................6 4. Composite type section of the Makah Formation from Waadah Island and Baada Point to Kydaka Point............................................................................................7 5. Composite reference section of the Makah Formation along the Hoko River......................................8 6-8. Photographs showing: 6. Northeast-trending sandstone dikes cutting a sandstone channel and thin-bedded siltstone and sandstone in the upper part of the Makah Formation.......................................9 7. Aerial view toward southeast of prominent headlands formed by the four turbidite members in the lower part of the Makah Formation....................................................... 9 8. Medium- to very thick-bedded turbidite sandstone beds of the Baada Point Member of the Makah Formation......................................................................... 1 0 9. Generalized stratigraphic sections of the four turbidite members of the Makah Formation at their type sections.......................................................................................11 10-11. Photograph showing: 10. Flute casts at base of thick amalgamated sandstone of the Dtokoah Point Member at its type section........................................................................... 12 11. Thick beds of turbidite sandstone in the Klachopis Point Member........................................ 13 12. Ternary diagram showing composition of sandstones in the Makah Formation.................................... 15 13-14. Photograph showing: 13. Calcite-cemented biotite-bearing arkosic sandstone in the Third Beach Member......... ................................................................................16 14. Lithic arkosic wacke from Baada Point Member........................................................... 16 15. Paleogeographic map showing the inferred margins of the Tofino-Fuca basin relative to other deep-water marginal basin facies in the Pacific Northwest.................................................23 16. Rose diagrams showing orientations of flute casts and groove casts in the Makah Formation and three of its members..................................................................................24 TABLES Table 1. Checklist of foraminifers from the Waadah Island section of the Makah Formation showing frequency of occurrence...................................................................................18 2. Checklist of foraminifers from the Hoko River section of the Makah Formation showing frequency of occurrence...................................................................................20 III Makah Format!on--A Deep-Marginal-Basin Sedimentary Sequence of Late Eocene and Oligocene Age in the Northwestern Olympic Peninsula, Washington By P.D. Snavely, Jr., A.R. Niem, N.S. MacLeod, J.E. Pearl, and W.W. Rau ABSTRACT INTRODUCTION The Makah Formation of the Twin River Group crops The Makah Formation is part of a thick deep-water out in a northwest-trending linear belt in the north- marine sequence of upper Eocene to lower Miocene sand westernmost part of the Olympic Peninsula, Wash. This stone, siltstone, turbidite sandstone, and conglom marine sequence consists of 2800 meters of predomi erate that crops out in the northwestern part of the nantly thin-bedded siltstone and sandstone that en Olympic Peninsula (fig. 1) in a northwest-trending closes six distinctive newly named members four linear belt more than 100 km long. The Makah Forma thick-bedded amalgamated turbidite sandstone members, tion was named and briefly described by Snavely, Niem, an olistostromal shallow-water marine sandstone and and Pearl (1978) from detailed geologic mapping in the conglomerate member, and a thin-bedded water-laid tuff western 35 kilometers of this belt, which includes the member. A local unconformity of submarine origin Makah Indian Reservation in the northwestern part of occurs within the lower part of the Makah Formation the study area. The Makah consists chiefly of well- except in the central part of the study area, where it bedded siltstone and thin-bedded turbidite sandstone forms the contact between the older Hoko River Forma and contains six lithologically distinctive and map- tion and the Makah. Foraminiferal faunas indicate pable members, described and formally named in this that the Makah Formation ranges in age from late report, and two informal sandstone units. The named Eocene (late Narizian) to late Oligocene (Zemorrian) members are four thick-bedded amalgamated turbidite and was deposited in a predominantly lower to middle sandstone members, a thin but distinctive tuff member, bathyal environment. and a penecontemporaneously deformed allochthonous The Makah Formation is part of a deep-marginal- sandstone and conglomerate member that initially was basin facies that crops out in the western part of the deposited in shallow water. Olympic Peninsula, in southwesternmost Washington and The type locality of the Makah Formation, desig coastal embayments in northwestern Oregon, and along nated by Snavely, Niem, and Pearl (1978) as the shore the central part of the coast of western Vancouver cliffs and wave-cut platform exposures along the Island. On the basis of limited subsurface data from Strait of Juan de Fuca from Waadah Island and Baada exploratory wells, correlative deep-marginal-basin Point to Kydaka Point (fig. 2), is herein redesignated deposits underlie the inner continental shelf of the type section. Rocks exposed in the lower reaches Oregon and the continental shelf (Tofino basin) along of the Sekiu and Hoko Rivers were selected as refer the southwestern side of Vancouver Island. ence sections (Snavely and others, 1978). Directional structures in the Makah Formation in The Makah Formation is equivalent to the middle dicate that the predominantly lithic arkosic sandstone member of the Twin River Formation of Brown and Gower that forms the turbidite packets was derived from the (1958). Snavely, Niem, and Pearl (1978) raised the northwest. A possible source of the clastic material Twin River Formation to group rank and divided the is the dioritic, granitic, and volcanic terranes in Twin River Group into three new formations, from old the vicinity of the Hesquiat Peninsula and Barkley est to youngest, the Hoko River, the Makah, and the Sound on the west coast of Vancouver Island. Vertical Pysht Formations. and lateral variations of turbidite facies suggest Excellent exposures in the mapped area make it that the four packets of sandstone were formed as possible to collect detailed sedimentological data on depositional lobes on an outer submarine fan. The dispersal patterns and lateral and vertical facies thin-bedded strata between the turbidite packets have changes in the turbidite sandstone units. These data characteristics of basin-plain and outer-fan fringe are used in this report to interpret the depositional deposits. environment, provenance,