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Fall 1985
Sedimentary Petrology, Depositional Environment, and Tectonic Implications of the Upper Eocene Quimper Sandstone and Marrowstone Shale, Northeastern Olympic Peninsula, Washington
William E. (William Ernst) Rauch Western Washington University
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Recommended Citation Rauch, William E. (William Ernst), "Sedimentary Petrology, Depositional Environment, and Tectonic Implications of the Upper Eocene Quimper Sandstone and Marrowstone Shale, Northeastern Olympic Peninsula, Washington" (1985). WWU Graduate School Collection. 741. https://cedar.wwu.edu/wwuet/741
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Date: SEDIMENTARY PETROLOGY, DEPOSITIONAL ENVIRONMENT, AND TECTONIC IMPLICATIONS OF THE UPPER EOCENE QUIMPER SANDSTONE AND MARROWSTONE SHALE, NORTHEASTERN OLYMPIC PENINSULA, WASHINGTON
A Thesis Presented to the Faculty of Western Washington University
In Partial Fulfillment of the Requirements for the Degree Master of Science
by
WILLIAM E. RAUCH December, 1985 SEDIMENTARY PETROLOGY, DEPOSITIONAL ENVIRONMENT,
AND TECTONIC IMPLICATIONS OF THE UPPER EOCENE
QUIMPER SANDSTONE AND MARROWSTCNE SHALE,
NORTHEASTEPN OLYMPIC PENINSULA, WASHINGTON
by
WILLIAM E. RAUCH
Accepted in Partial Completion of the Requirements for the Degree Master of Science
Advisory Committee
Chairperson FRONTISPIECE
The finest workers in stone are not copper or steel tools, but the gentle touches of air and water working at their leisure with a liberal allowance of time. Henry David Thoreau ABSTRACT
The Upper Eocene ^Refugian) Quimper Sandstone and overlying Marrowstone Shale document approximately 300 meters of sediment deposited in a tectonical ly active, shal low marine area during a transgression. The Quimper Sandstone and Marrowstone Shale can be roughly divided into three facies, representing deposition from outer shore face and inner shelf to offshore or outer shelf. Petrographic analysis of the Quimper Sandstone and Marrowstone Shale indicates geography and hydrodynamic conditions were responsible for a slight petrologic trend in composition such as more feldspar and lithic grains in the lower energy facies. The sandstones are lithic and feldspathic arenites and wackes with abundant feldspars and volcanic lithic fragments. The petrology requires source areas with granitic rocks, andesite, basalt, and chert exposed. Possible source areas include the Crescent Formation, the Coast Plutonic Complex, the San Juan Islands, Vancouver Island, and the North Cascades. Deposition of the Quimper Sandstone and Marrowstone Shale marks the culmination of movement on the Discovery Bay Fault Zone. These sediments are found overlying the fault zone but not apparently offset by it. Bedding attitudes are consistent across the fault zone. The Discovery Bay Fault Zone has been suggested to be a tectonic suture between the Crescent Terrane and local Tertiary North America. The arrival and subsequent docking of the Crescent Terrane is coincident with a plate reorganization along with a decrease in convergence rates between the Farallon and North American plates. Cessation of movement on the Discovery Bay Fault, along with simple thermal subsidence of the Crescent basalts, deepened the basin, as shown by the sediments grading from
i hummocky cross-stratified sands of the inner shelf to silty shales of the outer shelf.
ii ACKNOWLEDGMENTS
I would like to thank my thesis committee members: Dr. Christopher A. Suczek who gave hours of guidance and for continuous encouragement especially during the final days of this project; Dr. David C. Engebretson for many stimulating discussions, particularly on tectonics and for introducing me to the problem; and Dr. Randall S. Babcock for petrographic consultation. I would also like to thank Patty Combs and Vicki Critchlow for their patience in answering many questions regarding graduate student life. Thanks to George Mustoe for consultation on photography and thin section production. Special thanks to Dr. Joanne Bourgeois and Elana Leithold for discussions on sedimentology. Dr. Mark Brandon for discussions about coeval sedimentary rocks on Vancouver Island, and Dr. Robert Gray, Mr. Karl Halbach, Mr. Philip Olson, and Ms Terri Plake of Santa Barbara City College for introducing me to the great science of geology. I would also like to thank Cmdr. J.A. Hamilton of the United States Navy and all personnel at NUWES, Indian Island Detachment, for allowing me access to the base. Thanks also go to the numerous residents of Marrowstone Island and the Quimper Peninsula who allowed me access to the rocks on their property. Many thanks to the members of the 'Olympic Team': Kurt Anderson for introducing me to the Olympic Peninsula field experience at its wettest, Jennie DeChant for field assistance, Ron Moyer for discussions on tectonics, Joel Purdy and Tim Roberts for many Olympic discussions and for putting up with me as a house-mate. Special thanks to Kurt Anderson, Keith Pine, and Moira Smith whose commitment to recreation in the form of aerobics, skiing, sail boarding. Ff-
and mountaineering allowed me to experience the specialness of the Pacific Northwest which not only stimulated the body but also the mind, allowing this project to be completed. Most of al 1 I would like to thank my parents. Bill and Selma Rauch, for their continual love and support, and who taught me at an early age the value of education. This project was partial ly funded by the American Association of Petroleum Geologists, Grants-in-Aid program, and a grant from the Geology Department at Western Washington University.
iv TABLE OF CONTENTS
Abstract i Aknowledgements iii Table of Contents v List of Figures vii List of Tables and Plates x Introduction 1 Regional Geology 1 Local Geology 7 Previous Work Depositional Environment 14 Introduction 14 Depositional Features 14 Hummocky Cross-Stratified Facies 14 Laminated Facies 22 Silty Shale Facies 22 Interpretation 28 Discussion 33 Petrology and Petrography 36 Introduction 36 Descriptive Petrography 39 Post-Depositional Changes 47 Provenance 51 Tectonic Provenance 51 Possible Source Areas 53 Coast Plutonic Complex 55 San Juan Islands 55
V Vancouver Island 56 North Cascades 57 Olympic Peninsula 58 Discussion 59 Deposition and Tectonics 61 Deposition 61 Discussion of Tectonics 66 Summary and Conclusions 71 References Cited 73 Appendix 1: Description and Discussion of Grain Categories 79 Appendix 2: Modal Analysis of Samples from the Hummocky Cross- Stratified Facies 90 Appendix 3: Modal Analysis of Samples from the Laminated Facies 93 Appendix 4: Modal Analysis of Samples from the Silty Shale Facies 99 Appendix 5; Average Modal Compositions 100
vi LIST OF FIGURES
Figure 1. Generalized location map showing the distribution of the Olympic Core Terrane and the Crescent Terrane. 2 Figure 2. Generalized cross-section of the Olympic Peninsula from west to east. 4 Figure 3. Map showing major faults. 6 Figure 4. Geologic Map of the Quimper Peninsula area showing the location of the Quimper Sandstone and Marrowstone Shale. 8 Figure 5. Composite stratigraphic column of the Quimper Peninsula area. 10 Figure 6. Stratigraphic column of Marrowstone Island. 16 Figure 7. Stratigraphic column of Indian Island. 18 Figure 8. Dynamic zones of the beach to outer shelf. 19 Figure 9. Hummocky cross-strata. 21 Figure 10. Concretionary pebble lens. 21 Figure 11. Laminated facies outcrop. 23 Figure 12. Shell fragments outlining laminations. 24 Figure 13. Silty carbonaceous layers with concretions. 24 Figure 14. Ophiomorpha burrows. 25 Figure 15. Outcrop of Marrowstone Shale. 26 Figure 16. Concretion with bored wood fragment. 27 Figure 17. Sandstone dike in Marrowstone Shale. 29 Figure 18. Hummocky cross-stratified sequences 32 Figure 19. Relative changes in sea level through time. 35 Figure 20. Sandstone classification diagram. 40 Figure 21. Q-F-L diagram. 42 Figure 22. Qm-F-Lt diagram. 43 Figure 23. Qp-Lv-Ls diagram. 44
vii Figure 24a. Lathwork and microlitic volcanic lithic fragment, plane light. 46 Figure 24b. Lathwork and microlitic volcanic lithic fragment, polarized light. 46 Figure 25a. Crystal vitric tuff, plane light. 48 Figure 25b. Crystal vitric tuff, polarized light. 48 Figure 26. Concretions in Quimper Sandstone. 50 Figure 27. Q-F-L plot showing tectonic provenance. 52 Figure 28. Qm-F-Lt plot showing tectonic provenance. 52 Figure 29. Qp-Lv-Ls plot showing tectonic provenance. 52 Figure 30. Map showing location of possible source areas. 54 Figure 31. Map showing possible sediment sources and transport directions of Late Eocene rocks. 68 Figure 32. Relative velocity vectors for Farallon motion. 69 Figure 33a. Quartz and feldspar grains, plane light. 80 Figure 33b. Quartz and feldspar grains, polarized light. 80 Figure 34a. Plagioclase and volcanic lithic grain, plane light. 81 Figure 34b. Plagioclase and volcanic lithic grain, polarized light. 81 Figure 35a. Zoned plagioclase, plane light. 82 Figure 35b. Zoned plagioclase, polarized light. 82 Figure 36a. Altered plagioclase, plane light. 83 Figure 36b. Altered plagioclase, polarized light. 83 Figure 37a. Pumpellyite, plane light. 85 Figure 37b. Pumpellyite, polarized light. 85 Figure 38a. Pyroxene, plane light. 86 Figure 38b. Pyroxene, polarized light. 86 Figure 39a. Chert, plane light. 88 Figure 39b. Chert, polarized light. 88 Figure 40a. Sedimentary lithic fragment, plane light. 89
viii Figure 40b. Sedimentary lithic fragment, polarized light. 89 LIST OF TABLES AND PLATES
Table 1. Stratigraphic nomenclature applied to formations of the Quimper Peninsula area. 12 Table 2. Grain parameters used in plotting point count data. 38 Table 3. Outcrop location abbreviation definitions. 41 Table 4. Summary of events. 65
Plate 1. Sample location map of Indian Island, Marrowstone Island, and east Quimper Peninsula. 101 Plate 2. Sample location map of west Quimper Peninsula and east Miller Peninsula. 102
X INTRODUCTION
The Upper Eocene Quimper Sandstone and Marrowstone Shale are part of a sequence of Tertiary marine sedimentary rocks that forms an east-west- trending band across the northern edge of the Olympic Peninsula in northwest Washington (Figure 1). The Quimper and Marrowstone formations represent approximately 300 meters of sediment deposited in a tectonically active shallow marine area during transgression. The depositional history of the Quimper Sandstone and Marrowstone Shale reflects the Late Eocene tectonic development of the Olympic Peninsula as well as local changes in the depositional basin. The purpose of this thesis is to describe the sedimentology of the Quimper Sandstone and Marrowstone Shale and to relate this to the regional tectonic development of the Olympic Peninsula.
REGIONAL GEOLOGY
The geology of the Olympic Peninsula in northwestern Washington has been divided into two major geologic domains: the core rocks and the peripheral rocks (Tabor and Cady, 1978) (Fig. 1). Silberling and others (1984) redefined these two domains the Olympic Core Terrane and the Crescent Terrane, respectively, and defined a third, minor terrane as the Ozette Terrane. The Olympic Core Terrane consists predominantly of complexly deformed packets of Eocene to Miocene sedimentary rocks and interbedded volcanics; they have been thrust under the Crescent basalts, which are the basal member of the Crescent Terrane, and metamorphosed from zeolite to lower greenschist facies. The core rocks have been subdivided into two major domains: the eastern core and the western core. Rocks of the eastern core are more recrystallized and penetratively
1 Figure 1. Location map showing the Crescent Terrane, the Olympic Core Terrane, and the area of study. Crescent Formation in ruled pattern. Area of study in stippled pattern.
2 sheared than rocks of the western core. Metamorphic events recorded by the core rocks are a regional recrystallization and penetrative deformation at 29 Ma and a local recrystallization at 17 Ma ^Tabor, 1972). The arcuate, fault-bounded structural packets top eastward and young westward and have been interpreted to be an accretionary prism emplaced during subduction of oceanic lithosphere ^Tabor and Cady, 1978; Cady, 1975)(,Figure 2). The Crescent Terrane consists of the Crescent Formation and overlying marine sedimentary units. The Crescent Formation consists of a horseshoe-shaped belt of Early to Middle Eocene oceanic tholeiitic basalt and interbedded marine sedimentary rocks that have been interpreted as an accreted seamount province (Tabor and Cady, 1978). Overlying and interfingering with the Crescent Formation is a sequence of Eocene to Miocene marine sedimentary units, which general ly top away from the core. The peripheral rocks are only mildly deformed by folding and faulting, apparently because the rigid horseshoe-shaped basalts of the Crescent Formation acted as a barrier protecting the rest of the peripheral rocks from the intense deformation to which the core rocks were subjected during accretion ^Tabor and Cady, 1978). Correlative to the Crescent basalts are the Metchosin Volcanics on southern Vancouver Island (Cady, 1975). These basalts are separated from the rest of Vancouver Island by the Leech River fault. On the northeast Olympic Peninsula, this shallowly north-dipping thrust fault becomes an east-dipping thrust fault system known as the Discovery Bay Fault system (Macleod and others, 1977; Fairchild, 1979; Fairchild and Cowan, 1982) ^Fig. 3). The Discovery Bay fault has been proposed to represent the tectonic suture between the Crescent Terrane and local Tertiary North America ^Fairchild and Armentrout, 1984).
3 Figure 2. Generalized cross-section west-east through the Olympic Mountains (from Tabor and Cady, 1978).
4 Figure 3 Map showing some major faults on the Olympic Peninsula, Vancouver Island, and the Washington mainland (modified from Fairchild, 1979).
i
5 km
6 Movement along the Leech River and San Juan faults post-dates the 40 Ma metamorphism of the Leech River Complex and pre-dates the 32 Ma deposition of the Sooke Formation ^Fairchild, 1979). Movement along the Discovery Bay Fault is said to pre-date the 37 Ma deposition of the Quimper Sandstone, which may overlie the fault (Fairchild and Armentrout, 1984; Armentrout, 1984). Thus, if the Crescent and Metchosin basalts are of the same origin and have remained fixed relative to one another, and the Discovery Bay Fault system is a tectonic suture, the accretion of the Crescent Terrane occurred between 40 and 37 Ma, narrowing the 40 and 32 Ma time interval assigned to the accretion of the Metchosin basalts on southern Vancouver Island ^Fairchild and Armentrout, 1984).
LOCAL GEOLOGY
On the Quimper Peninsula, in the northeastern part of the Olympic Peninsula, the Crescent Formation is overlain by a sequence of Eocene marine sedimentary rocks ^Figures 4 and 5). Directly overlying the Crescent Formation is an unnamed Eocene sedimentary unit ^the sandstones of Scow Bay) which may either have a conformable depositional contact (Allison, 1959; Armentrout and Berta, 1977) or be coeval with the Crescent Formation ^Worsley and Crecelius, 1972; Gower, 1980). Unconformably above the unnamed unit is the Eocene Lyre Formation, which is unconformablyoverl ain by the Upper Eocene Quimper Sandstone and Marrowstone Shale ^Armentrout and Berta, 1977). The Quimper Sandstone is underlain by the unnamed Eocene sandstones of Scow Bay on Marrowstone and Indian Islands, by the Crescent Formation on the eastern Quimper Peninsula, and by the Townsend Shale member of the Lyre Formation on the western Quimper Peninsula. On the eastern side of
7 Eocene Quat | iTel 1
t Qg « u
| 1 1 Glacial Marrowstone Lyre Quimper Crescent Unnamed of
Scow Formation
Figure deposits
Sandstone Bay Eocene Formation
Shale 4.
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surrounding 8
map
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1977). (modified
dikes Peninsula
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Figure 5. Composite stratigraphic column of the Quimper Peninsula area (modified from Allison, 1959).
9 EOCENE 3 5 *3 2 c « (0 <2 o Q. Q. <*- oc « (0 >> 0) CT (0 c 3 ‘ .2 z c 3 (0 n 3 Q. W C « « « O a 0) k « C 3 a « 2
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STRATIORAPHIC 10 Marrowstone Fine thickness and concretionary oidal to 9 Uncotiforatty. urtconforaebly on ■ore Some concretions weathers Feldspsthic-'lithic section. to Contact Townsend Unconforaxty. the Cosigluaeiate The ■aster Nowhere be Thickness quarts. of ConqlOMrate, stone Contact silt ranqe known sandstone Thickness weathered concretions. Siltscone, l«ciel Massive at conglomerate. hard, near dark this sandstone.
buff« Scow Unconformity. the fine
Crescent Contact These ■us ash-white. Siltstunes gray,
of and the tions, to and fthythmical seen has glass asygdaloidal Basalt, which poor fomity? in siltfetones. necanorphics, Basalt light lithic
COLUMN approximately ^ifltper
contact senJstone carbonaceous abundant
to in
occurs gray. the
black dark color, seen Modified du*« from
West
gray-green
esse exposed siltstone of the
abundant Bay
Beteile). grained,
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in weathers sorting satui places. relationships Hexi«u« tan.
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is fragments. is
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rest Scow relationships sandatone ■amber shore in between commonly 450 a More Dark weather uester matrix. ly Contains owriaict lack a towaid and swtseivc Lyre rest to The tlte Fresh thin The ^is^ier concretionary Numerous color, contain area arc thickness to sotse Thickness limunici.- basal the Well uncunfoiwaMy or Bay snd interbedded to sediment feet of thickness liqht nedlua up beds. Fxssilf;. to cherts, tan siitstone, to The maturial 850 Qray silty silty ot shales light. of Townsend Herrowurone lisKinitxc sandstone, of on was not vesicular, cobble fonsatiun. Msrrowstone basaltic Harrowstone boulder to reddish formation at stratification. is the from ooncintionary rock tlto bedded. deeply and on Pilloidal Indian to to light Maynard exposure, bed %reather feet. of is the Pebble bedded. the are between by many >]ray to d" fragment not in ShO fissile, qraineu, ami Itrown irregular limeston*-. M.ixiniuin columnar, upper the the iuK>iiici< 20 top qcadrit Crescent are dark between admixe is ( contact. ii< nc-t si;te, about present brown on irregular to feet. catftonececuii Allison, weatluTeil. htuwn 2000 fel tc lit}M <>i a shaipstonn green-black diamuT.er. l.yc-? typos sandstone massive, black are - 6aiirt on shales port rarely lomerate an.Jie tri» olive-sray, in t: dense, i butt. variety Particles uncuntormity? nMr the island, shale with i-xpi^sed concnotions li 640 .^raywacke wtati-.vrs ot ftosi the t.> feet the side are , r^eeply i , >'oncre- unknown. -jray often milestone ion formation. Maynard itones <.-w bcdn. torpiattun 1. upner- (Oiisist Alxn-e Maxi- to Uncon- shale smti- light scato is feet u>ay upper and with Matrix a un* map and on grf-on ot of medtum often and Only . the 1959 the the Miller Peninsula, the Quimper Sandstone is found between exposures of glacial drift. The Quimper Sandstone grades into the Marrowstone Shale on Indian and Marrowstone Islands, while the upper Quimper Sandstone on the western Quimper Peninsula is covered by glacial drift, as is the Marrowstone Shale on Indian and Marrowstone Islands. A small outcrop of Marrowstone Shale is exposed on the east side of the Miller Peninsula between exposures of glacial drift. Deformation is minimal with faults trending general ly north-south and bedding attitudes generally striking northwest-southeast and dipping to the northeast. PREVIOUS WORK Arnold U906) made the first reconnaissance study of Tertiary units on the north slope of the Olympic Peninsula. The first mention of sediments on the Quimper Peninsula was by Weaver ^1916), who stated that sandstones and shales of Oligocene age rest upon the northern flanks of the Discovery Bay anticline. The sandstones and shales Arnold ^1906) and Weaver U916) described were first named the Clallam Formation iTable 1). Weaver U937) described an Oligocene formation, which he named the Lincoln Formation, consisting of a basal conglomerate overlain by fossi1iferous, massive, nodular, brown, sandstone that crops out along the east shore of Port Discovery Bay, and included the first geologic map of the Quimper Peninsula. The Quimper Sandstone was named by Durham (1942), who stated that two new formations of Early Oligocene age were the Townsend Shale and the unconformably overlying Quimper Sandstone. These two units are underlain by the Lyre conglomerate. The formations were dated as Oligocene by 11 TABLE 1: Stratigraphic nomenclature applied to formations of the Quimper Peninsula area ^modified from Armentrout and Berta, 1977). Arnold Weaver Weaver Durham Allison 1959 Armentrout & 1906 1916 1937 1944 Thoms 1959 Berta 1977 Marrow- Marrowstone Marrow- stone Shale stone Shale Shale Quimper Quimper Quimper Sandstone Sandstone Sandstone Townsend Cong. Mem. L Townsend L Clallam Clallam Lincoln Shale _ Y Shale Y Formation Formation Formation Townsend Sh. R R Lyre _. C SS-Cong E Formation Maynard SS. Fm. Member Fm. Unnamed Scow Bay Eocene Upper Formation Unit tOCcMC Rocks c Upper R Crescent Member E Formation S Crescent Crescent Tejon _ _ c Formation Formation Lava Metchosin E Volcanics Metchosin N Member T Fm. 12 means of mollusks ^Durham, 1944). The Marrowstone Shale was named by Durham U944), who described a fossi1iferous sandy shale overlying the Quimper Sandstone on the east side of Kilisut Harbor on Marrowstone Island. Allison U959) studied the megafossils and Thoms (1959) studied the microfossils of the Quimper Sandstone and Marrowstone Shale and assigned them to the Refugian stage of the Oligocene series, which was the same as the assignment by Kleinpell (1938). Armentrout and Berta (1977), after reviewing Thoms' samples in conjunction with further sampling, also assigned the Quimper Sandstone and Marrowstone Shale to the Refugian stage, which now is included in the Upper Eocene. Allison (1959) and Thoms (1959) made the first detailed map of the Quimper Peninsula. Gower (1980) mapped the bedrock geology to identify major bedrock faults using aeromagnetic and gravity anomalies. Armentrout and Berta (1977) inferred that the lower part of the Quimper Sandstone was deposited at upper sublittoral to sublittoral depths and that it grades upward into the finer-grained sediments of the Marrowstone Shale, which were deposited at sublittoral to upper bathyal depths. 13 DEPOSITIONAL ENVIRONMENT In general, the Quimper Sandstone and overlying Marrowstone Shale represent a shallow marine transgressive sequence. Outcrops are limited to coastal cliffs and wave-cut piatforms, which are general ly poorly exposed; they are usual ly covered by vegetation or Recent 1 andsl ides. The rocks are poorly indurated except for the abundant concretions. DEPOSITIONAL FEATURES Based on lithology and sedimentary structures, the two formations can be roughly divided into three facies (Figures 6 & 7). The hummocky cross-stratified facies consists of amalgamated hummocky cross-stratified sets, planar cross-beds, laminations, and shell and pebble lenses that decrease in number up-section. The massive and laminated facies consists of structureless and finely laminated fine-grained sandstone with scattered carbonaceous silt interlayers and localized burrows. The silty shale facies consists of silty shale layers with interbeds of fine grained sandstone with localized burrows, layers of carbonaceous material, and cross-cutting sandstone dikes. All three facies contain abundant calcareous concretions. These three facies are interpreted as representing a shallow marine transgressive sequence from outer shoreface and inner shelf to offshore or outer shelf sedimentary environments ^Figure 8). HUMMOCKY CROSS-STRATIFIED FACIES The basal contact of the Quimper Sandstone is nowhere exposed; however it can be approximated within 20 meters. Where Quimper Sandstone 14 Figure 6. Columnar section of the Quimper Sandstone and Marrowstone Shale on west Marrowstone Island. (see Figure 4 for location). 15 Q u i m p e rS a n d s t o n e 0 covered covered Silty Laminated Hummocky 16 Shale Facies Facies Cross-Stratified Facies Figure 7. Columnar section of the Quimper Sandstone and Marrowstone Shale on west Indian Island. (see Figure 4 for location). Q u i m p eS r a n d s t o n e Marrowstone Shale E 1 2 3 covered covered Hummocky Laminated Silty 18 Shale Facies C r o s s - S t r a t i f i e d Facies Facies OSCILLATORY WAVES WAVES OF TRANSLATION 19 Figure 8. Cross-section of the dynamic zones from beach to outer shelf (modified from Bourgeois, 1980). can be positively distinguished from underlying medium-grained sandstone with shale interbeds and angular discordance, it consists of lenses containing pebbles up to 3 centimeters in diameter within a predominantly medium- to fine-grained sandstone. Fragments of gastropod and pelecypod shells are also present in lenses. The lenses of pebbles and shells occasionally fill scoured surfaces in medium- to fine-grained sandstone. The hummocky cross-stratified sets are characterized by erosional bases (.eroded into hummocks and swales) commonly lined with pebbles and shell debris, laminations parallel to these erosional surfaces, and a decrease in gradient of the laminae upward (Figure 9). The pebble and shel1 lenses decrease upward in frequency. Individual hummocks within the sequence vary, but they average approximately 25 centimeters thick with laminae draped over the scoured surface grading into planar cross-beds or parallel and wavy laminations or both. Cross-strata are rare; parallel laminae are more common in the hummocky cross-stratified sequence. The 1 aminations range from wel 1 defined to indistinct, depending on the exposure. Some indistinct laminae may have been grouped into structureless layers. Some of the structureless samples show bioturbation on freshly cut surfaces. The laminae are generally less than 0.5 centimeters in thickness and are defined by alternations of darker and lighter colored material, which are alternations of heavy minerals and organic material with lighter grains. Scattered layers of carbonaceous silt occur between the fine-grained laminations. These layers are generally less than 1.0 centimeter thick. Concretions are abundant throughout this facies with many enclosing the shell and pebble lenses ^Figure 10). 20 Figure 9. Hummocky cross-strata in the Tower part of the Quimper Sandstone, west Indian Island. Figure 10. Concretionary pebble lens in the lower part of the Quimper Sandstone, west Indian Island. 21 LAMINATED FACIES Above the hummocky cross-stratified facies is a series of parallel and wavy laminations with large sections of structureless, fine-grained sandstone and scattered silty carbonaceous layers that are very poorly indurated ^Figure 11). Pebbles are noticeably absent; however, broken shells, much smaller than those in the previous facies, are present but rare, usually outlining laminations ^Figure 12). The laminae are general ly less than 0.5 centimeters thick and are defined by alternating light and dark material; the light material is composed of light grains, and the dark material is organic matter and heavy minerals. Distinction of laminae is often difficult due to poor exposure. I have included these poorly defined laminae with the massive, structureless sandstone, which also shows intense bioturbation in some fresh samples. The friable silty carbonaceous layers generally range from 0.5 to 3 centimeters in thickness. They are usually stained with limonite, contain abundant organic material, and contain many small concretions up to 4 centimeters in size ^Figure 13). Higher up in this facies are localized coal seams up to 15 centimeters thick. Burrows (Ophiomorpha ?) are also present near the top of this facies (Figure 14). SILTY SHALE FACIES The basal portion of this facies occurs at the contact between the Quimper Sandstone and Marrowstone Shale. Allison (1959) and Thoms (1959) defined the gradational contact between these formations as the highest massive sandstone unit that lacks fissility. This facies is characterized by thin layers of silty to sandy shale with sparse interbeds of fine- to medium-grained sandstone (Figure 15). 22 Figure 11. Massive Quimper Sandstone with silty interlayers, west Indian Island. 23 Figure 12. Shell fragments outlining obscure laminations, west Quimper Peninsula. Figure 13. Silty carbonaceous layers with concretions, west Marrowstone Island. 24 Figure 14. Ophiomorpha burrows, east Quimper Peninsula. 25 Figure 15. Outcrop of Marrowstone Shale, west Marrowstone Island. 26 The silty shale layers vary in thickness but average approximately one centimeter thick. The scattered sandstone interbeds also vary in thickness but are generally less than one meter thick. A variety of fossils and burrows occurs throughout the facies ^Figure 16), with the burrows being better preserved in the lower part of the facies. Carbonaceous material is abundant throughout this facies. Cross-cutting sandstone dikes ranging from 3 to 15 centimeters in thickness are present in the lower part of the facies (Figure 17). Concretions are common and are very well indurated compared to the friable host rock, which tends to weather spheroidal ly. The top of this unit is covered by glacial till or water. INTERPRETATION Based on the sequence of sedimentary structures and the grain size, the Quimper Sandstone and Marrowstone Shale can be interpreted as a shal low marine transgressive sequence ranging from inner shelf at the base to outer shelf at the top (Figure 8). The lower Quimper Sandstone is characterized by the hummocky cross-stratified facies. Harms and others (1975) first introduced the term hummocky bedding for a sedimentary structure characterized by sets having low angle, erosional lower surfaces; parallel laminae overlying these surfaces; systematically thicker laminae laterally within a set whereby dip decreases upward; and dip directions that are scattered (Bourgeois, 1980). The formation of hummocky beds has been attributed to the oscillatory or multidirectional flow generated by strong wave action such as that caused by storms (Harms and others, 1975; Dott and Bourgeois, 1982; Duke, 1985). A characteristic sequence of hummocky beds and related structures has been 27 Figure 16. Extensively bored wood fragment within a concretion, west Marrowstone Island. 28 29 likened to the Bouma Sequence by Dott and Bourgeois il982)^Figure 18). The hummocky beds are followed by flat laminations, which are followed by cross-laminations, in turn followed by mud layers ^Swift and others, 1983). Formation of hummocks has been linked to the braided trajectories of wave orbitals produced by storm waves. The wave orbitals presumably scour the bed surface in a rotary fashion producing hummocks and swales. As the flow wanes with the storm, it can no longer maintain the hummocky configuration. Turbulence is thus less intense, al lowing the suspended sediment entrained under higher flow conditions to settle out and mantle the newly carved hummocks and swales with a thin blanket of sediment ^Swift and others, 1983). The idealized hummocky stratification sequence is not preserved in the Quimper Sandstone. Erosion may have eliminated the ripples and mud of the idealized sequence, leaving amalgamated hummocky cross-sets (Figure 18). Occurences of amalgamated sequences of hummocky cross-strata have been interpreted as representing deposition in a shallow (shallower than that of the idealized sequence), high energy (frequent storm events) environment, close to the source, below fairweather wave base, and above storm wave base (Hamblin and Walker, 1979; Dott and Bourgeois, 1982; Walker and others, 1983; Duke, 1985). The upper Quimper Sandstone is characterized by the laminated facies. Deposition of the laminations may have taken place under conditions of waning energy with rapid deposition of sediment from suspension. These laminations may be related to the laminations associated with the Dott and Bougeois (1982) hummocky cross-stratified sequence. Deposition may have taken place in deeper water than did the lower Quimper, below storm wave base where the hydrodynamic conditions were insufficient to sculpt the beds into a hummocky and swaley 30 Figure 18. Idealized hummocky cross-stratified sequences with conmon variations, amalgamated sequences, and a con tinuum showing causal factors (from Dott and Bourgeois, 1982). IDEALIZED HUMMOCKY SEQUENCE UNBURROWED BURROWED M MUDSTONE Mb X CROSS LAMINAE X b F FLAT LAMINAE F b HUMMOCKY ZONE H b <*LA6 ±SOLES) COMMON VARIATIONS M X H XZDNE X THICK MISSING F MISSING AMALGAMATED SEQUENCES lag TRUNCATED M-CUTOUT BIOTUR8ATED TYPES CONTORTIONS TYPE TYPE A POSSIBLE CONTINUUM AND CAUSAL FACTORS AMALGAMATED NORMAL FXMb MICRO-HUMMOCKY TUR8I0ITES AND H TYPES HFXMb TYPES LENSES GRADED LAMINITES MORE SAND LESS SAND SHALLOWER DEEPER LARGER WAVES ■* WEAKER EFFECTS MORE FREQUENT LESS FREQUENT MORE PROXIMAL MORE DISTAL 32 topography ^Reineck and Singh, 1973; Kreisa, 1981). The paucity of burrows and presence of some vertical Ophiomorpha burrows supports rapid sedimentation. The vertical Ophiomorpha burrows may represent escape structures. The silty organic layers may represent periods of fair weather allowing deposition of the fine storm-suspended sediment. The localized layers of coal may also have been deposited during tranquil periods. Rapid sedimentation is suggested by the presence of plant fragments within the coal layers, because such organic material is susceptible to oxidation and decay under normal or slow sedimentation rates and thus would not be preserved. The Marrowstone Shale is entirely composed of the silty shale facies. Deposition of the si Ity shale may have occured in deeper and thus quieter water where the hydrodynamic conditions allowed the silty shale to settle. The intercalations of sandstone may have been brought about by periods of higher flow during storms. High rates of sedimentation are again inferred because of the lack of bioturbation and the presence of sandstone dikes. DISCUSSION The Quimper Sandstone and Marrowstone Shale represent a shallow marine transgressive sequence. The internal structures of these rocks resulted from the combined effects of transport, deposition, reworking of sediments, and diagenesis in a wave-dominated environment. Regional and local basin subsidence as wel 1 as eustatic sea level changes may have combined to produce the deepening-upward sequence. The presence of the amalgamated hummocky cross-stratification suggests a nearby source with abundant sediment output, possibly a delta. 33 Bourgeois U980) and Hunter and Clifton U982) used ripple heights and wavelengths as well as grain sizes on the tops of hummocky sequences to calculate paleobathymetry. Ripples are absent in the Quimper Sandstone, and therefore this method for estimating water depth cannot be used; however the presence of hummocky cross-strata suggests open-ocean storm- wave activity. Calculations of wave heights for the present Oregon shelf indicate depths of up to 50 meters ^Bourgeois, 1980), which would be reasonable for the formation of the hummocky cross-strata. Harms U979) estimates hummocky cross-strata may form at depths of 5 to 30 meters, and Hunter and Clifton (,1982) estimate depths as shallow as 2 meters. The transgressive sequence shown for the Quimper Sandstone and Marrowstone Shale by the sedimentary structures and decreasing grain sizes is supported by paleoecological data of Armentrout and Berta U977). Megafossils from the basal Quimper Sandstone indicate upper sublittoral to sublittoral warm-temperate water on the inner shelf (Durham, 1942, 1944). The upper Quimper was deposited at sublittoral to upper bathyal depths under warm-temperate conditions. Foraminiferal assemblages from the Marrowstone Shale indicate deposition at sublittoral to upper bathyal depths under deeper, colder water conditions with restricted connections to open ocean currents suggested by the presence of carinate cassidulinid foraminifers (Armentrout and Berta, 1977). Vail and others (1977) show a global rise in sea level during the deposition of the Quimper Sandstone and Marrowstone Shale (Figure 19). However, it is difficult to say whether global sea level rise or regional or local basin subsidence due to loading or tectonic activity was responsible for the transgressive sequence that is preserved. 34 Global Cycles of Sea Level Changes Figure 19. Global cycles of sea level changes showing a rise in sea level during deposition of the Quimper Sandstone and Marrowstone Shale (shown in blue) (from Vail and others, 1977). 35 PETROLOGY AND PETROGRAPHY Introduction Samples were collected from the three facies described earlier in the different geographical locations. One hundred thin sections were examined. Of these, thirty samples were chosen for modal analysis. Each thin section was half-stained with sodium cobaltinitrite and amaranth for the identification of potassium feldspar and plagioclase feldspar, respectively. Point counts were done using a 0.2 millimeter spacing. This allowed the counts to cover a maximum amount of area without counting any but the largest grains more than once. A 300-grain point count was conducted on the stained half of each thin section to determine the overall composition of the rocks. A separate 200-grain point count was conducted on the unstained half allowing a better resolution of lithic constituents. The results are presented in Appendices 2,3, and 4. The Gazzi-Dickinson method of point counting was used in this study. This method eliminates the effects of grain size without affecting the mineralogy Ungersoll and others, 1984). Most of the samples examined were taken from concretions. The concretions contain more calcite cement than the surrounding host rock with very little matrix and minimal alteration, thus all owing easier identification of the constituents. Comparisons have been made between concretionary and nonconcretionary samples. (Concretionary samples denoted by "C" after sample number in the appendices). Differences were negligible. The fol lowing categories were counted for each sample: Monocrystalline quartz. Includes individual grains and fine-sand- sized or larger crystals or grains within rock fragments. 36 P^: Plagioclase feldspar. Includes individual grains and fine-sand-sized or larger crystals or grains within rock fragments. K: Potassium feldspar. Includes individual grains and fine-sand-sized or larger crystals or grains within rock fragments. y All lithic fragments. Fine-sand-sized or larger grains or crystals within lithic fragments were counted as separate grains. Pump: Pumpellyite. Includes individual grains and fine-sand-sized or larger crystals or grains within rock fragments. Cem: Calcite, laumontite, and pyrite cement. Matrix was counted in this category where noted. Heav: All heavy and mafic minerals. Misc: Miscellaneous grains. Includes grains that cannot be identified or do not fit in any of the other catagories. The lithic categories include: Lvl: Lathwork volcanic lithic grains. Lvm: Microlitic volcanic lithic grains. Lvo; Other volcanic lithic grains. Includes felsic, cryptocrystalline, vitric, and other volcanic lithic grains that do not fit in the above volcanic lithic catagories. Qp + Chert: Polycrystalline quartz and chert. Lsm: Sedimentary lithic grains. Includes all sedimentary and meta sedimentary lithic grains except chert. Lmisc: Miscellaneous lithic grains. Includes lithic grains that cannot be identified or do not fit in any of the other catagories. A more detailed description of these individual catagories is given in Appendix 1. The grain parameters used in plotting the point count data are explained in Table 2. 37 TABLE 2 : Grain Parameters ^modified from Ingersoll and Suczek, 1979). Q = Qm + Qp where Q = total quartzose grains Qm = monocrystal 1inequartz grains Qp = polycrystalline quartz grains F = P + K where F = total feldspar grains P = plagioclase feldspar grains K = potassium feldspar grains Lt = L + Qp where Lt = total lithic grains L = unstable lithic grains Lv = Lvl + Lvm + Lvo where Lvl = lathwork volcanic lithic grains Lvm - microlitic volcanic lithic grains Lvo = other volcanic lithic grains L = Lsm + Lv + Lmisc where Lmisc = miscellaneous lithic grains Lsm = sedimentary and metasedimentary lithic grains 38 Descriptive Petrography The Quimper Sandstone and the sandstones associated with the Marrowstone Shale are lithic and feldspathic arenites and wackes (classification of Dott, 1964)^Fig. 20). Since the point-count data plot in a cluster, they will be described collectively rather than by facies. The average modal analysis is Q-F-L:52-22-26; Qm-F-Lt:40-22-38; Qp-Lv- Ls:12-65-23; P/F:0.75. (See Figures 21,22, & 23 & Table 3 for ternary plots & Appendix 5 for average modal analysis .) The sandstones are generally well sorted and are angular to subrounded. Sizes of individual samples range from medium to fine sand ^approximately 1.75 ft to 3.75 J?) based on a visual estimation. Grain relationships include floating grains, and tangential, long, and concavo-convex grain contacts with the first two being the most common. The framework grains are usually held in calcite cement with varying amounts of matrix; however rare silica, laumontite, and pyrite cements are present. Some of the clean calcite cement exhibits a poikilitic texture with sand grains surrounded by a single calcite crystal. Protomatrix, orthomatrix, and pseudomatrix (classification of Dickinson, 1970) are all present in varying amounts, occuring more commonly in non-concretionary samples; however matrix is also found in concretionary samples. Monocrystalline quartz is present in undulose and nonundulose varieties. Vacuoles and inclusions are abundant, suggesting a plutonic source. Rare euhedral quartz crystals are volcanic. Metamorphic quartz is present in trace amounts. Both plagioclase and potassium feldspars are present. Sodic and calcic varieties of plagioclase are present in varying amounts. Many of the sodic plagioclase crystals, exhibiting albite and Carlsbad twins, are 39 40 TABLE 3. Key to abbreviations used on Ternary diagrams. Geographic Location: WII = West Indian Island WMI = West Marrowstone Island EQP = East Quimper Peninsula WQP = West Quimper Peninsula EMP = East Miller Peninsula Facies: HUM = Hummocky Cross-Stratified Facies LAM = Laminated Facies SHA = Silty Shale Facies 41 D W5K5K + + + OXX<3 + 0 X DIAGRAM J CM i + fi Ll OT 1 0 42 U m HHHIZZ0OOZ HHHHHHCULQ.CLijwijinjijj D I I + I + II +©XX I I 1 I 43 .< .' /'1 ! i i I -p j Figure 22. Qm--F-[_t DIAGRAM 2z *H«5K + + + ©XX< x-'" ^,y'~ 2 < d 0 < H □ 00 0 ^ w ^ J •s,. _0) i u. > I oa ✓ j 44 within volcanic lithic fragments. Some of these are also zoned. Many of the plagioclase grains have undergone sericitization, while others are unaltered. The potassium feldspar is untwinned orthoclase and is generally unaltered. The lithic grains are dominated by lathwork and microlitic volcanic lithic fragments ^Figure 24). These volcanic lithics usually consist of plagioclase crystals within an aphanitic matrix. These grains range from clear and unaltered to heavily altered. Constituents of the sedimentary and metasedimentary lithics catagory vary from coarse sandstone fragments to siltstone fragments. Chert was counted separately; however, if the chert contained a significant amount of impurities it was counted under the sedimentary and meta-sedimentary lithic catagory. Chalcedonic quartz is also present in trace amounts and was counted as polycrystalline quartz. Pumpellyite makes up a significant portion of the framework grains. Like the other grains, pumpellyite comes in altered and unaltered varieties. The pumpellyite is detrital rather than authigenic, since some occurs as amygdaloidal fillings in the volcanic rock fragments and is often associated with chlorite. Prehnite, which is usually associated with pumpellyite, is absent. This may indicate a unique source; however the prehnite may have been lost during transport. Other minerals that are present in small amounts include muscovite, biotite, chlorite, glauconite, pyroxene, and zircon. Pebbles, which were deposited as lag deposits, are of a variety of lithologies including shale, sandstone, chert, basalt, intermediate volcanics, and plutonic rock fragments. The intermediate volcanics are mostly dacite with some andesite. The plutonic rock fragments are composed of granite and granodiorite. Fragments of gastropods and 45 Figure 24a. Lathwork and micro!itic volcanic lithic fragment, plane light, field of view: 0.85 x 0.58 mm. Figure 24b. Lathwork and microlitic volcanic lithic fragment, polarized light, field of view: 0.85 x 0.58 mm. 46 pelecypods are also found in these lag deposits. Disseminated carbonaceous material occurs throughout the upper part of the Quimper Sandstone and Marrowstone Shale. A 15-centimeter-thick bed of tuff is exposed on west Marrowstone Island. This crystal vitric tuff is of a dacitic composition (Figure 25). The quartz and albite-twinned plagioclase are fresh and unaltered. The glass shards are well preserved and unaltered. Stretched out pumice fragments are also present. These constituents are set in a carbonate cement composed of fibrous, radiating crystals, which is probably aragonite. Post-Depositional Changes Diagenetic changes that altered the sediments of the Quimper Sandstone and Marrowstone Shale include the precipitation of cement, alteration of detrital framework grains, and the formation of orthomatrix and pseudomatrix. The cement is predominantly cal cite; however, trace amounts of laumontite, silica, and pyrite cement are also present. The calcite varies from murky, caused by mixture with very fine-grained materials, to a very clear poikilitic mosaic of calcite crystals. The calcite etches and replaces some framework grains, especially plagioclase and volcanic lithic fragments. Some of this alteration to calcite is so extensive that determination of the original composition of the grains isextremely difficult. The rare laumontite cement may have formed from the .alteration of calcic plagioclase (Blatt, 1982). The silica cement is polycrystal 1 ine and occurs in smal 1 amounts. Some of this cement may have been mistaken for crushed chert fragments. The formation of pyrite 47 Figure 25a. Crystal vitric tuff, plane light, field of view: 2.1 x 1.5 mm. mm. 48 is usually associated with reducing conditions and organic matter iPettijohn and others, 1972). Some pyrite is present in concretion-1 ike balls up to 2 centimeters in diameter, much of which has altered to limonite. The concretions throughout the Quimper Sandstone and Marrowstone Shale are calcite-cemented. They vary in size from a few centimeters to several meters in length and are usual ly parallei to subparallei to bedding ^Figure 26). This orientation occurs because the bedding plane is the surface of greatest permeability, and highest permeability allows pore fluids to gather at those sites (Blatt, 1982). Framework grains generally float in the calcite cements although there are some tangential grain contacts. Laminations and pebbley and fossi1iferous lenses continue through the concretions undeflected, indicating the concretions must have formed after compaction of the sediments ^Blatt, 1982). Much of the matrix in these rocks formed after depostion. The original protomatrix is difficult to distinguish and has been recrystallized to form a murky calcite orthomatrix. Some of the orthomatrix is very well preserved, exhibiting fine-grained crystalline forms. Some grains have been crushed and deformed between more resistant grains forming pseudomatrix. Epimatrix does not seem to be present; however, distinction between epimatrix and pseudomatrix is difficult. Burial diagenesis and metamorphism represent a continuum of pressure and temperature variables, and thus the cut-off between the two is not well defined. Since the Quimper Sandstone and Marrowstone Shale exhibit no preferred orientation of grains or other texture associated with metamorphism, and since they lack metamorphic mineral suites, the post- depostional changes affecting these sediments seems to be those of burial diagenesis rather than metamorphism. 49 50 PROVENANCE Determination of provenance for the Quimper Sandstone and Marrowstone Shale is based on the results of the petrographic analysis, since reliable paleocurrent indicators were not observed. Detritus contained in the Quimper Sandstone and Marrowstone Shale indicates four major types of source rocks. These include granitic rocks, intermediate volcanic rocks, basalts altered to pumpellyite, and chert. TECTONIC PROVENANCE Provenance determinations are based on triads of percentages, derived from the modal analyses, plotted on ternary diagrams. Dickinson and Suczek U979) divided ternary diagrams into areas of differing tectonic provenance. This differentiation was based on a comparison of modal analyses of sandstones from known tectonic settings, both recent and ancient. General interpretations can be made for sandstones of an unknown origin when their compositions are plotted on these ternary diagrams ^Figures 27,28, & 29). Data from the modal analyses were plotted on Figures 21, 22, and 23. Some very slight petrologic trends based on facies are present, such as relatively fewer feldspar grains in the Hummocky Facies, more feldspar in the Shale Facies, and variable amounts of feldspar in the Laminated Facies along with relatively more feldspars on west Marrowstone Island and less feldspar but more volcanic lithic fragments on the west Quimper Peninsula. However, these trends can be considered as variations in response to the different hydrodynamic conditions and local geography and not to changes in the source area. The data plotted on the ternary diagrams indicate a recycled orogen 51 Q Figure 27. Triangular QFL plot ahowlng fraoe- work modes for selected sandstone suites derived from different types of provenance; Q Is total quartzose grains. Including monocrystaillne Qm and polycrystalllne Qp varieties; F Is total feldspar grains (all are monocrystalllne); L Is total unstable llthlc fragstents (all are poly- cryatalllne). ^ (2m Figure 28. Triangular QmFLt plot showing frame work modes for selected sandstone suites derived from different types of provenance: Qm Is mono- crystalline quartz grains; F Is total feldspar grains (all are monocrystalllne); Lt Is total polycrystalllne llthlc fragments. Including stable quai^tzoae Qp aa well aa unstable L varieties. Qp Figure 29. Triangular QpLvLs plot showing propor tions of polycrystalllne llthlc fragments for selec ted sandstone suites derived from different types of provenance: Qp la polycrystalllne quartzose grains. Mlnly chert; Lv is total volcanic-metavolcanlc rock fragments; Ls Is unstable sedlmentary-metaaedlmeatary rock fragments. ' modified from Dickinson end Suczek (1979). provenance on the Q-F-L diagram and an arc orogen on the Qp-Lv-Ls diagram. The Qm-F-Lt diagram however, indicates no distinct tectonic provenance, but a subduction zone is suggested. These suggested tectonic provenances are consistent with the type of framework grains present; however, interpretations of this type for an area consisting of a conglomeration of exotic terranes should be approached with caution, as the many sediment sources associated with these terranes may be misleading iC.A. Suczek, verbal communication, 1985). POSSIBLE SOURCE AREAS Assessing provenance by looking for present-day rocks similar to those that provided sediment to the Quimper Sandstone and Marrowstone Shale has proven to be successful. The specific rocks producing the sediment have been eroded; however remnants of these sources may sti 11 exist. Only likely sources will be discussed. ^See Figure 30 for location of possible sources.) Areas that may have contributed sediment to the Quimper Sandstone and Marrowstone Shale include the Coast Plutonic Complex, the San Juan Islands, Vancouver Island ^north of the San Juan Fault), the North Cascades, and the Olympic Peninsula. Except for the Olympic Peninsula, the geographic positions of Vancouver Island (.north of the San Juan Fault), the San Juan Islands, the Coast Plutonic Complex, and the North Cascades have remained constant with respect to one another since the late Cretaceous, constrained by the deposition of the Nanaimo Group ^Pacht, 1984). Misch U977a), however, suggests the North Cascades have been offset along the Straight Creek Fault during the late Cretaceous to early Tertiary. Movement of the Olympic Peninsula is constrained by deposition of the Sooke Formation across the San Juan and 53 Figure 30. Location map showing potential source areas (modified from Tennyson and Cole, 1978). 54 Leech River Faults on Vancouver Island (Fairchild, 1979) and by deposition of the Quimper Sandstone across the Discovery Bay Fault (Fairchild and Armentrout, 1984; Armentrout, 1984). Coast Plutonic Complex The Coast Plutonic Complex, of the western Canadian Cordillera, consists of Cretaceous to lower Tertiary plutonic and metamorphic rocks that are largely diorite and granodiorite, some intermediate to silicic volcanics, and high grade metasediments (Roddick, 1965; Monger and others, 1982). Metamorphic rock fragments in the Quimper occur only in trace amounts, while intermediate volcanic rock fragments occur in the pebble-sized portion. Plutonic rock fragments in the sand-sized portion of the Quimper Sandstone and Marrowstone Shale are present as aggregates of quartz and feldspar, making any specific plutonic rock classification difficult. Pebble-sized clasts, however, indicate the presence of granite and granodiorite. Pacht (1984) suggests the Coast Plutonic Complex as a possible source for the Nanaimo Group. Both the Nanaimo Group and the Quimper Sandstone have average P/F ratios of 0.75. The Coast Plutonic Complex may be a possible source the granitic grains found in the Quimper Sandstone and Marrowstone Shale. San Juan Islands The various terranes comprising the San Juan Islands also may have contributed plutonic detritus; however, most of the plutonic rocks of the San Juan Islands are ophiolitic: mostly gabbros (Brandon and others, 1983). Sources for intermediate volcanics in the San Juans are those of sedimentary formations containing volcanic clasts and thus are not likely 55 sources for the Quimper Sandstone and Marrowstone Shale, because most of the volcanic rock fragments in the latter units are fresh. The Orcas Chert and Deadman Bay Volcanics both consist of pillowed volcanics, limestone, chert, and mudstone (Brandon and others, 1983). The Orcas Chert is thrust over the Deadman Bay Volcanics; however, these two formations may have originally been stratigraphical ly continuous (Brandon and others, 1983). These formations are likely candidates to have contributed the chert and basalt fragments, with the limestone and mudstone having been lost during transport. The Lopez Complex contains basalts with aragonite, pumpellyite, and chlorite and also some ribbon cherts. These rocks may have contributed chert and basalt, with aragonite having been lost during transport. Most of the formations which make up the San Juan Islands contain chert, basalt, intermediate volcanics and associated plutonics in varying amounts and thus may have contributed sediment to the Quimper Sandstone and Marrowstone Shale; however, many other rock types are also present in the San Juans and were not observed in the Quimper Sandstone or Marrowstone Shale. Therefore, if the San Juan Islands did contribute, it was in minor amounts. Vancouver Isl and Vancouver Island is also a likely candidate for possible sediment sources. The Jurassic Island Intrusions, occuring throughout southern Vancouver Island, consist of granodiorite, quartz diorite, granite, and quartz monzonite (Muller, 1977; Brandon and others, 1983). These rocks may be a potential source for plutonic detritus. The Westcoast Complex may have contributed some plutonic material also, but it includes 56 metamorphic rocks, which are not found in the Quimper Sandstone and Marrowstone Shale. The Pacific Rim Complex may have supplied chert and basalt. The Early Tertiary Catface Intrusives could have been a source for silicic plutonics. Possible volcanic source rocks on Vancouver Island include rocks of the Jurassic Bonanza Group, which are basaltic to rhyolitic lavas, tuffs, and breccias ^Muller, 1977; Brandon and others, 1983). The Myra volcanics, which are part of the Upper Paleozoic Sicker Group, are composed of intermediate to silicic tuffs and breccias along with some argillite. The Bonanza Group is a more likely source than the Myra volcanics because it contains flows whereas the latter does not. The Pacific Rim Complex, which overlies the volcanics of the Bonanza Group, may have contributed chert. Many of the rocks on Vancouver Island have been metamorphosed to various degrees. The Quimper Sandstone and Marrowstone Shale have very little metamorphic detritus, which suggests that Vancouver Island was a minor contributor of sediments to the Quimper Sandstone and Marrowstone Shale. North Cascades On the eastern side of the depositional basin lie the North Cascades. Deep-seated plutons associated with Tertiary volcanics in the Cascades were probably not exposed during the Late Eocene and therefore could not have contributed plutonic detritus to the Quimper Sandstone and Marrowstone Shale. Older plutonic complexes, such as the Mesozoic Mount Stuart batholith, which is the largest of the older plutons in the Cascades, may be a potential source. Granodiorite is the primary 57 lithology of the Mount Stuart batholith and was exposed during the Tertiary (Tabor and others, 1984). However, the long transport distance would produce a more mature sediment than what is found in the Quimper Sandstone and Marrowstone Shale and thus would not be a likely source. Rock types that now dominate the North Cascades include metamorphic rocks of various grades and therefore is not a likely source since there is very little metamorphic detritus in the Quimper Sandstone and Marrowstone Shale; however the metamorphic grains may have been lost during transport. The Wells Creek Volcanics, the Chilliwack Group, and the Nooksack Group may all have contributed volcanic material, with the latter two contributing some chert, and the Cultus Formation also contributing chert (Misch, 1977b). It is possible, however, that sediments from the North Cascades may have been caught up in the Chuckanut-Huntington river system and therefore may not have reached the depositional site of the Quimper Sandstone and Marrowstone Shale. Overall, the North Cascades are not a likely source. Olympic Peninsula Locally, the Crescent Formation, which partially underlies the Quimper Sandstone, may have contributed basalt fragments. Petrographical ly, the basalt contains albite- and Carlsbad-twinned plagioclase laths, pyroxene, and radial pumpellyite crystals with associated chlorite, all of which are present in the Quimper Sandstone and Marrowstone Shale. The Crescent Formation is a prime candidate for the source of the basalt fragments, because the delicate nature of the radial pumpellyite crystals would not likely survive a long transport distance. 58 DISCUSSION With the variety of lithologic units in the areas presently adjacent to the Quimper Sandstone and Marrowstone Shale, it is very difficult to pin-point one specific area as a source. Structural complexities associated with this lithologic variety also make it difficult to assign a source area in this patchwork of allochthonous terranes. Petrologic studies suggest several possible sources for the Quimper Sandstone and Marrowstone Shale, which include the Coast Plutonic Complex, the San Juan Islands, Vancouver Island, the North Cascades, and locally sourced by the Crescent Formation. The Coast Plutonic Complex may have supplied Plutonic, volcanic, and chert fragments. Chert, volcanic, and fine grained sedimentary fragments may have come from the San Juan Islands. Vancouver Island and the North Cascades may have contributed plutonic, volcanic, and chert fragments as well as the minor sedimentary and metamorphic rock fragments present in the Quimper Sandstone and Marrowstone Shale. The pumpellyite-bearing basalt may have been contributed by the Crescent Formation on the Olympic Peninsula. Varying amounts of sediment input from al 1 of these areas are possible. It is also possible that, in this tectonically active and complex area, source terranes contributing sediment to this depositional basin have since been transported northward towards southeast Alaska in the same manner as in Cowan's U982) Baranof Is 1 and model which suggests 1,100 ki 1 ometers of displacement of Leech River Complex-equivalent rocks from southern Vancouver Island to southeast Alaska. A comparison with the underlying sandstones of Scow Bay initially shows more lithic fragments than the Quimper Sandstone, which could be explained by the change in energy of the depositional environments. On 59 closer examination, however, the dominant lithic grain-type in the sandstones of Scow Bay is sedimentary whereas the Quimper Sandstone lithicsare volcanic. Moreover, the Quimper Sandstone contains granite, granodiorite, and pumpellyite. The sandstones of Scow Bay contain piagiogranite and are thought to be sourced by the San Juan Islands (Melim, 1984). This change in lithic composition indicates a change in the source to the depositional basin. In summary , with the San Juan Islands and the north Cascades being less likely sources, as discussed previously, sediments derived from Vancouver Island, the Coast Plutonic Complex, and the Olympic Peninsula are more 1 ikely to have sourced the Quimper Sandstone and Marrowstone Shale. / 60 DEPOSITION AND TECTONICS In developing a model for the tectonic setting during the deposition of the Late Eocene Quimper Sandstone and Marrowstone Shale, a discussion of sedimentological and structural relationships of adjacent, relevent rock units is necessary. DEPOSITION Correlative and adjacent rock units provide some important constraints concerning the paleogeography of the area during the Eocene. These rock units include the time-correlative Makah Formation on the northwestern Olympic Peninsula and parts of the Carmanah Group of Vancouver Island, formerly referred to as Divisions A, B, and C of Jeletzky's U973) Vancouver Island sections ^Armentrout and Berta, 1977). The Makah Formation, which makes up the middle member of the Twin River Group, is a thick sequence of marine sandstone, siltstone, turbidite sandstone, and conglomerate ^Snavely and others, 1980). A thinly bedded, water-laid tuff, refered to as the Carpenters Creek Tuff iSnavely and others, 1980), may be correlative with a tuff layer found near the Quimper-Marrowstone contact on west Marrowstone Island. Paleocurrent indicators suggest that this predominantly lithic arkose was derived from dioritic, granitic, and volcanic terranes of western Vancouver Island and deposited as depositional lobes on an outer fan system at lower to middle bathyal depths ^Snavely and others, 1980). An unconformity occurs within the lower part of the Makah Formation in some areas, while in other areas it marks the contact between the Makah Formation and the underlying Hoko River Formation. Snavely and others U980) suggested this to be a local unconformity. This 61 unconformity seemingly occurs at the Narizian-Refugian boundary, which Armentrout U973) suggested is a regional unconformity in western Washington marked by changes in sedimentary facies in addition to changes in foraminiferal and molluscan assemblages isee Armentrout, 1973 for further discussion). This unconformity is apparent at the contact between the Quimper Sandstone and the sandstones of Scow Bay and will be discussed later in this chapter. On western Vancouver Island, a sequence of Late Eocene sedimentary rocks is also coeval with the Quimper Sandstone and Marrowstone Shale. Armentrout and Berta U977) stated that the Quimper Sandstone and Marrowstone Shale are correlative with parts of the Carmanah Group and Divisions A, B, and C of Jeletzky's U973) Vancouver Island section. This is misleading, because these are not different formations but different names for the same units. Jeletzky's U954, 1973) Division A was renamed the Escalante Formation by Cameron U971, 1972). The Escalante Formation is the basal member of the Carmanah Group ^Cameron, 1971, 1972). Jeletzky's U954, 1973) Divisions B and C were renamed the Hesquiat Formation by Cameron (1971, 1972). Divisions B and C are coeval and were initially separated by Jeletzky (1954) because of their highly contrasting lithologies and geographic separation. The Hesquiat Formation is the middle member of the Carmanah Group. It has a gradational contact with the underlying Escalante Formation and an unconformable contact with the overlying Oligocene Sooke Formation, which is the uppermost member of the Carmanah Group (Muller and others, 1981). The Escalante Formation is composed of a calcareous sandstone with minor shelly conglomerates and argillaceous sandstone containing disseminated carbonaceous material and concretions (Jeletzky, 1975; 62 Cameron, 1980). The upper part of the Escalante Formation grades into the overlying Hesquiat Formation through calcareous sandstone to finer grained, argillaceous sandstone, siltstone, and shale interbeds ^Jeletzky, 1975; Cameron, 1980). Foraminiferal and molluscan faunal assemblages indicate differing paleobathymetric interpretations. The following is based on foraminifera, in keeping with other interpretations for adjacent rock units. Few foraminifers were found in the Escalante Formation; however, a neritic to upper bathyal depth with a rapid deepening is required in view of the rich bathyal foraminiferal assemblages found in the transitional beds to the overlying Hesquiat Formation (Cameron, 1980). The Hesquiat Formation is composed of a complex of interbedded sandy shale, graded cyclic sandstone-silty shale-shale interbeds, and a pebbly mudstone with lenses of boulder and pebble conglomerates (Jeletzky, 1975; Cameron, 1980). Micro- and megafauna along with the sediments and sedimentary structures making up the Hesquiat Formation indicate a slope deposit at bathyal depths within a submarine fan complex (Cameron, 1980). Muller and others (1981) suggested volcanic and plutonic rocks from the Coast Intrusions and the Vancouver Group as possible sources. Deposition of the Quimper Sandstone and overlying Marrowstone Shale marks the culmination of movement on the Discovery Bay Fault Zone as these sediments are found overlying the fault zone but not offset by it, with the same bedding attitude of a northwest strike and a northeast dip on both sides of the fault. Armentrout (1984) and Fairchild and Armentrout (1984) suggested the juxtaposition of terranes by movement on the Discovery Say Fault Zone. On the east side of the fault zone, unconformably below the Quimper Sandstone, are the unnamed Eocene 63 sandstones of Scow Bay; on the west side is the Lyre Formation. Both of these formations were deposited as submarine fan complexes at lower sublittoral to upper bathyal depths. A possible model is as follows: As the Crescent Terrane was rafted in and underthrust along the Discovery Bay Fault, a shallowing in the depth of the basin resulted from the arrival or processes associated with the arrival of this buoyant fragment. Quimper Sandstone sediments began to be deposited. Subsidence of the basin throughout deposition of the Quimper Sandstone and Marrowstone Shale may have occurred when movement and stresses, on the Discovery Bay Fault were transferred to reverse faults of the western Cascades and the Devil's Mountain Fault ^Fairchild and Armentrout, 1984). Simple thermal subsidence, as described by Sclater U972), may also account for the apparent subsidence of the depositional basin. At the time of deposition of the Quimper Sandstone, the Crescent basalts were approximately 7 million years old. After 4 million years of deposition (approximated since the top of the Marrowstone Shale is not exposed), the Crescent basalts then being 11 million years old, the Crescent basalts would have subsided approximately 270 meters. The additional material needed can be accounted for by a global rise in sea level (Vail and others, 1977), or by sediment loading. ( see Table 4 for summary of events.) Equivalent rock units discussed earlier (e.g.: Makah, Escalante, and Hesquiat Formations) also show an increased depth in their respective depositional basins relative to underlying formations, but do not exhibit the petrologic differences from underlying rocks that the Quimper Sandstone does. The unconformity at the Nerizian-Refugian boundary (Armentrout, 1973) may document the arrival of the Crescent Terrane. Possible source areas discussed by various workers on the coeval rock 64 TABLE 4 : Sunmary of Events. TIME STATE OF PLATES EVENTS AND CONDITIONS Before deposition of - major decrease in convergence - lower sublittoral to upper the Quimper Sandstone between FaralIon-North America bathyal basin depth and Marrowstone Shale coincident with change in abso lute motion of Pacific relative - regional unconformity at to hot spots (43 Ma) Narizian-Refugian boundary - Kula-Farallon reorganized - deposition and subsequent uplift of Lyre Formation - Demise of Kula-Pacific spreading ridge at 43 Ma, - deposition and subsequent uplift of sandstones of Scow Bay - initiation of Cascade vol- canism (43 Ma) y)]M3 During deposition of - metamorphism of Leech River the Quimper Sandstone Complex (38-41 Ma) and Marrowstone Shale - deposition of the Makah Formation - deposition of the Escalante and Hesquiat Formations - cessation of movement on the Discovery Bay Fault - movement on San Juan and Leech River Faults - emplacement of Metchosin basalts and Leech River Complex - change in basin depth through time from sublittoral during Quimper deposition to lower sublittoral to upper bathyal during Marrowstone deposition 37 Ma After deposition of - continued decreases in convergence - uplift of the Quimper Sandstone the Quimper Sandstone between FaralIon-North America and Marrowstone Shale and Marrowstone Shale coincident with reduction of west ward motion of North America with respect to hot spots and reduction in Pacific-Farallon spreading rate (37 Ma) 65 units suggest that Vancouver Island and the Coast Plutonic Complex were topographic highs supplying sediment to the Tofino and Juan de Fuca basins. These sources along with others discussed previously most likely supplied sediment to the localized basin where the Quimper Sandstone and Marrowstone Shale were deposited ^Figure 31). Petrological ly, rocks underlying the Quimper Sandstone consist of arkosic sandstone making up the unnamed Eocene Sandstones of Scow Bay, to which Armentrout (1984) assigned a continental affinity, and tholeiitic basalts and basaltic sandstone of the Crescent and Lyre Formations, respectively, to which Armentrout (1984) assigned an oceanic affinity. These rocks were juxtaposed along the Discovery Bay Fault prior to deposition of the Quimper Sandstone. The lithology of the Quimper Sandstone suggests input from terrains of both continental and oceanic affinity, however, with sediment input in addition to that of local sources near the Quimper Peninsula area which Armentrout (1984) suggested. DISCUSSION OF TECTONICS Relative plate motions and plate interactions may have influenced the depositional history of the Quimper Sandstone and Marrowstone Shale. Prior to the deposition of the Quimper Sandstone, at approximately 43 Ma, the Farallon (Juan de Fuca) - Pacific ridge system is estimated to have been very near the edge of Tertiary North America (Engebretson, 1982; Engebretsonand others,1985). A reorganization of the Kula - Farallon system is coincident with a change in absolute motion of the Pacific plate relative to hot spots, along with a major decrease in convergence rates between the Farallon and North American plates (Figure 32 ) and the 66 Figure 31. Map showing possible transport directions (modified from Fairchild, 1979). 67 km 68 CO •M C O <_> lO 4-> in fO #o u OJ 0 u *TD OJ c 1 E H3 in Xiu/ui>| demise of the Kula - Pacific spreading system, also occurring at about 43 Ma ^Engebretson, 1982; Engebretson and others, 1984; Wells and others, 1984). In addition to and possibly a consequence of this change in plate interactions at 43 Ma, is the initiation of Cascade volcanism (Wells and others, 1984). Accretion of the Crescent basalts, which may have formed on a microplate between the Kula or Farallon and North American plates in a transform-related marginal basin (Brandon and Massey, 1985), corresponds to the 43 Ma change in absolute motion of the Pacific plate. The process of this accretion may have produced the conditions necessary for deposition of the Quimper Sandstone and Marrowstone Shale. Syn- and Post-depositional tectonic events include a major decrease in convergence between the Farallon - North American plates, which is coincident with a reduction of westward motion of Tertiary North America with respect to hot spots and a reduction in the Pacific - Faral Ion spreading rate at approximately 37 Ma iWells and others, 1984). These tectonic conditions may have influence the depositional history of the Quimper Sandstone and Marrowstone Shale. SUMMARY AND CONCLUSIONS The Upper Eocene (Refugian) Quimper Sandstone and overlying Marrowstone Shale consists of approximately 300 meters of sediment deposited in a tectonically active shallow marine area during transgression. As a whole, the Quimper Sandstone and Marrowstone Shale fine and deepen upward. The Quimper Sandstone and Marrowstone Shale can be roughly divided into three facies, representing deposition from outer shoreface and inner shelf to offshore or outer shelf. The lower Quimper Sandstone is composed of amalgamated sequences of hummocky cross stratification, representing deposition in a shallow, high energy environment, close to the source, below fairweather wave base and above storm wave base. The upper Quimper Sandstone is composed of thin laminations deposited below storm wave base where the hydrodynamic conditions were insufficient to sculpt the beds into a hummocky and swaley configuration. The Marrowstone Shale is composed of a silty-sandy shale deposited in deeper, quieter waters of the deepening basin. Petrographic analysis of the Quimper Sandstone and Marrowstone Shale indicates geographic and hydrodynamic conditions are responsible for the slight petrologic trends in composition. The sandstones are lithic and feldspathic arenites and wackes, with volcanic rock fragments, quartz and plagioclase feldspars dominating the framework grains; chert, potassium feldspar, and sedimentary lithic fragments are subordinate. Calcite is the dominant cement, often replacing framework grains. The compositional difference between concretionary and nonconcretionary samples is negligible, as many of the partially replaced grains can still be identified; however matrix is sometimes obscuring. Petrology of the Quimper Sandstone and Marrowstone Shale requires 71 sources composed of granitic rocks, intermediate volcanic rocks, basalts, and chert. Several possible sources are suggested by the petrographic analysis. These include the San Juan Islands, the North Cascades, and the more preferred Coast Plutonic Complex, Vancouver Island and the Olympic Peninsula. Relative plate motions and plate interactions influenced the depositional history of the Quimper Sandstone and Marrowstone Shale. Prior to the deposition of the Quimper Sandstone, at approximately 43 Ma, a reorganization of the Kula-Faral Ion plate system occurred coincident with a change in absolute motion of the Pacific plate, decrease in convergence between the Faral Ion-North American plates, and demise of the Kula-Pacific spreading system. Accretion of the Crescent basalts corresponds to this 43 Ma reorganization (Wells and others, 1984). The accretion may have taken place along the Discovery Bay Fault Zone, which therefore may represent the suture zone between the Crescent Terrane and local Tertiary North America. Deposition of the Quimper Sandstone and overlying Marrowstone Shale marks the culmination of movement on the Discovery Bay Fault Zone, as these sediments are found overlying the fault zone but not offset by it, with a continuous bedding attitude across the fault. The arrival and subsequent docking of the Crescent Terrane resulted in a shallowing of the depositional basin prior to deposition of the Quimper Sandstone. A decrease in convergence rates between the FaralIon and North American plates, which reduced the streses on the Discovery Bay Fault, along with simple thermal subsidence of the Crescent basalts, gradually deepened the basin as shown by the sediments grading from hummocky-bedded sands of the inner shelf to silty shales of the outer shelf. 72 REFERENCES CITED Allison, R.C., 1959, The geology and Eocene megafaunal paleontology of the Quimper Peninsula area, Washington: unpublished M.S. thesis. University of Washington, 121 p. Armentrout, O.M., 1973, Stratigraphic relationships of the Narizian - Refugian boundary in Washington; Geological Society of America Abstracts with Programs, v. 5, n. 1, p. 4. 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University of Washington, 102 p. Vail, P.R., Mitchum, R.M., Jr., and Thompson, S., Ill, 1977, Seismic stratigraphy and global changes of sea level, part 4: Global cycles of relative changes of sea level, in Payton, C.E., ed.. Seismic Stratigraphy - applications to hydrocarbon exploration, American Association of Petroleum Geologist Memoir 26, p. 83-97. Walker, R.G., Duke, W.L., and Leckie, D.A., 1983, Hummocky stratification: Significance of its variable bedding sequences : Discussion and Reply: Geological Society of America Bulletin, v. 94, p. 1245-1251. Weaver, C.E., 1916, Tertiary formation of western Washington: Washington Geologic Survey Builetin, v. 13, 327 p. Weaver, C.E., 1937, Tertiary stratigraphy of western Washington and northwestern Oregon: University of Washington Publications, Geology, V. 4, 266 p. Wells, R.E., Engebretson, D.C., Snavely, P.D., Jr., and Coe R.S., 1984, Cenozoic plate motions and the volcano-tectonic evolution of western Oregon and Washington: Tectonic, v. 3, n. 2, p. 275-294. Worsley, T.R. and Crecelius, E., 1972, Paleogene calcareous nannofossils 77 from the Olympic Peninsula, Washington: Geological Association of America Bulletin, v. 83, p. 2859-2862. 78 APPENDIX 1: Description and discussion of grain categories. Qm: Monocrystalline Quartz. Monocrystalline quartz is present as undulose and nonundulose grains, with the former being more common. Quartz crystals are present in some of the volcanic lithic fragments and some embayed quartz grains were observed, suggesting a volcanic source. The presence of quartz, plagioclase feldspar, and potassium feldspar as aggregates and as individual grains suggests a plutonic source iFigure 33). Mineral inclusions such as rutile and tourmaline and vacuoles are present in some quartz grains. Plagioclase Feldspar. Plagioclase composition was determined using the Michel-Levy statistical method and the A-Normal method. The plagioclase is present as fresh or weathered individual grains or crystals contained in lithic fragments (.Figure 34). Volcanic lithic fragments contain plagioclase in the albite-oligoclase composition range, and Plutonic rock fragments contain ol igocl ase-1 abradorite composition range. Some bytownite is also present. Both twinned (albite and Carlsbad twins) and untwinned varieties of plagioclase are present. Oscillatory zoned plagioclase occurs in some of the volcanic lithic fragments as wel 1 as in individual grains (Figure 35), commonly with a bytownite and andesine composition. Weathered plagioclase have been altered to sericite (Figure 36). K: Potassium Feldspar. Potassium feldspar is well defined from the preferential staining, appearing dark yellow. Most grains are fresh and of the orthoclase variety. Most of the potassium feldspar grains are individual, however occasionally they occur with quartz or plagioclase in plutonic rock fragments (Figure 33). 79 Figure 33a. Quartz, feldspar, and plutonic rock fragment, plane light, field of view: 0.85 x 0.58 mm. Figure 33b. Quartz, feldspar, and plutonic rock fragment, polarized light, field of view: 0.85 x 0.58 mm. 80 Figure 34a. Plagioclase, chert, and volcanic lithic, plane light, field of view: 0.85 x 0.58 mm. Figure 34b. Plagioclase, chert, and volcanic lithic, polarized light, field of view: 0.85 x 0.58 mm. 81 Figure 35a. Zoned plagioclase, plane light, field of view: 0.85 x 0.58 mm. Figure 35b. Zoned plagioclase, polarized light, field of view: 0.85 x 0.58 mm. 82 Figure 36a. Sericitized plagioclase, plane light, field of view: 0.85 x 0.58 mm. Figure 36b. Sericitized plagioclase, polarized light, field of view: 0.85 X 0.58 mm. 83 Pump: Pumpellyite. Pumpellyite occurs as rounded detrital grains or within volcanic rock fragments. Many of the individual grains exhibit a fibrous, radial crystal habit. While the pumpellyite occuring in the volcanic lithic fragments occasionally has this fibrous, radial characteristic, it is more often in concentric layers as amygdaloidal fillings or replacing glass (Figure 37). Cem: Cement. Calcite cement is the dominant cement and is present in both concretionary and nonconcretionary samples, however it is more common in the former. Calcite is seen replacing some detrital grains. Trace amounts of silica, laumontite, pyrite, and hematite cement are also present. Heav: Heavy and Mafic minerals. These grains most 1 ikely came from volcanic and plutonic sources. The most common minerals in this category include biotite, muscovite, pyroxene (Figure 38), zircon, glauconite, pyrite, and chlorite. Mi sc: Miscellaneous Grains. This category includes grains that could not be identified or that did not fit in any of the other categories. L: Lithic Fragments. All multigranular and polycrystalline clasts containg subgrains of silt-size or smaller are included in this category. Description of lithic clast types follows. Lvl: Lathwork Volcanic Lithics. Lathwork volcanic fragments include basalt fragments containing abundant, randomly oriented plagioclase feldspars of albite-oligoclase composition, and pyroxenes (Figure 24). Fresh and weathered grains are present with the latter often being recognized only by a "lath-ghost." 84 Figure 37a. Pumpeliyite, plane light, field of view; 0.85 x 0.58 mm. Figure 37b. Pumpeliyite, polarized light, field of view: 0.85 x 0.58 mm. 85 Figure 38a. Pyroxene, piagioclase.and quartz, plane light, field of view: 0.85 x 0.58 mm. Figure 38b. Pyroxene, plagioclase, and quartz, polarized light, field of view: 0.85 x 0.58 mm. 86 Lvm: Micro!itic Volcanic Lithics. Micro!itic volcanic fragments include dacite and andesite with minor basalt fragments (Figure 24). Quartz and plagioclase feldspar phenocrysts occur in an aphanitic groundmass. Microlitic grains are generally fresher and less weathered than the lathwork volcanic fragments. Lvo; Other Volcanic Lithics. This category includes volcanic fragments that occur in amounts too small to warrant a separate category, such as the trace amounts of felsic volcanic fragments and altered volcanic glass. Qp + Chert; Polycrystalline Quartz and Chert. All polycrystal 1 ine quartz is included in this category. Most grains in this category are chert (Figure 39); however, chalcedonic quartz and metamorphic quartz aggregates appearing in trace amounts are also included in this category. Fine- and coarse-grained chert is present with varying amounts of impurities, usual ly micas, and appearing somewhat murky. If more than 15% impurities occur in the fragment, it was counted under the sedimentary and metasedimentary lithic category. Lsm; Sedimentary and Metasedimentary Lithics. Sedimentary lithic fragments ranged from coarse-grained sandstone down to shaley siltstone (Figure 40). Metasedimentary lithic fragments occur in trace amounts, usually phyllite or schist with platey minerals and stretched out quartz ^ ' f ■■■ .i : - • in a preferred orientation. 87 Figure 39a. Chert, plane light, field of view: 0.85 X 0.58 mm. Figure 39b. Chert, polarized light, field of view: 0.85 x 0.58 mm. 88 Figure 40a. Sedimentary lithic fragment, plane light, field of view: 0.85 X 0.58 mm. Figure 40b. Sedimentary lithic fragment, polarized light, field of view: 0.85 X 0.58 mm. 89 APPENDIX 2: Modal analysis of samples from the Hummocky Facies Total Count WMI -9-C WMI -10 WII -3-C ^300 Points) # % # % # % Qm 69 23 111 37 76 25.3 P 24 8 53 17.7 19 6.3 K 6 2 7 2.3 15 5 L 45 15 47 15.7 42 14 Pump. 10 3.3 6 2 12 4 Cem. 119 39.7 55 18.3 121 40.3 Heav. 19 6.3 9 3 1 0.4 Misc. 8 2.7 12 4 14 4.7 Lithic Count ^200 Points) Lvl 71 35.5 95 47.5 58 29 Lvm 40 20 52 26 38 19 Lvo 2 1 3 1.5 8 4 Qp + Chert 10 5 18 9 51 25.5 Lsm 71 35.5 32 16 40 20 Lmisc 6 3 0 0 5 2.5 Triads of percentages used for ternary diagrams Q-F-L Q 51.3 54.7 62.6 F 19.5 25.4 16.7 L 29.2 19.9 20.7 Qm-F-Lt Qm 44.8 47.0 37.5 F 19.5 25.4 16.7 Lt 35.7 27.6 45.8 Qp-Lv-Ls Qp 5.1 9.0 26.2 Lv 58.3 75.0 53.3 Ls 36.6 16.0 20.5 P/F Ratio 0.80 0.88 0.56 90 APPENDIX 2: Modal analysis of samples from the Hummocky Facies icont.) 1 1 1 O Total Count WII- 1 WII-•4-Ca WQP-6-C ^300 Points) # # % # % Qm 83 27.7 75 25 78 26 P 12 4 7 2.3 16 5.3 K 14 4.7 22 7.3 6 2 L 34 11.3 53 17.7 50 16.7 Pump. 14 4.7 7 2.3 24 8 Cem. 137 45.7 131 43.7 119 39.7 Heav. 0 0 3 1 4 1.3 Misc. 6 2 2 0.7 3 1 Lithic Count ^200 Points) Lvl 66 33 58 29 102 51 Lvm 30 15 33 16.5 59 29.5 Lvo 5 2.5 9 4.5 10 5 Qp + Chert 31 15.5 29 14.5 16 8 Lsm 60 30 70 35 13 6.5 Lmisc 8 4 1 0.5 0 0 Triads of percentages used for ternary diagrams Q-F-L Q 65.5 55.9 56.6 F 15.0 15.6 13.3 L 19.5 28.5 30.1 Qm-F-Lt Qm 47.7 40.3 47.0 F 15.0 15.6 13.2 Lt 37.3 44.1 39.8 Qp-Lv-Ls Qp 16.2 14.6 8.0 Lv 52.6 50.2 85.5 Ls 31.2 35.2 6.5 P/F Ratio 0.46 0.24 0.73 91 APPENDIX 2: Modal analysis .of samples from the Hummocky Facies ^cont.) Total Count WQP-8 WQP-9 WQP-■10 ^300 Points) # % # % # % Qm 55 18.3 66 22 70 23.3 P 19 6.3 21 7 16 5.3 K 8 2.7 9 3 2 0.7 L 52 17.3 38 12.7 59 19.7 Pump. 35 11.7 43 14.3 14 4.7 Cem. 109 36.3 109 36.3 109 36.3 Heav. 15 5 6 2 20 6.7 Misc. 7 2.3 8 2.7 10 3.3 Lithic Count ^200 Points) Lvl 120 60 71 35.5 87 43.5 Lvm 47 23.5 55 27.5 57 28.5 Lvo 1 0.5 3 1.5 6 3 Qp + Chert 11 5.5 18 9 16 8 Lsm 20 10 51 25.5 31 15.5 Lmisc 1 0.5 2 1 3 1.5 Triads of percentages used for ternary diagrams Q-F-L Q 45.5 55.3 52.8 F 18.6 19.7 11.0 L 35.9 25.0 36.2 Qm-F-Lt Qm 37.9 43.4 42.9 F 18.6 19.7 11.0 Lt 43.5 36.9 46.1 Qp-Lv-Ls Qp 5.5 9.1 8*1 Lv 84.4 65.2 76.1 Ls 10.1 25.7 15.8 P/F Ratio 0.70 0.70 0.89 92 APPENDIX 3: Modal analysis of samples from the Laminated Facies Total Count WMI -2-C WMI -3-C WMI -5 ^300 Points) # % # % # % Qm 47 15.7 57 19 87 29 P 31 10.3 40 13.3 48 16 K 10 3.3 8 2.7 5 1.7 L 88 29.3 62 20.7 66 22 Pump. 10 3.3 0 0 13 4.3 Cem. 103 34.3 123 41 70 23.3 Heav. 10 3.3 4 1.3 4 1.3 Mi sc. 1 0.3 6 2 7 2.4 Lithic Count (200 Points) Lvl 67 33.5 88 44 71 35.5' Lvm 39 19.5 42 21 49 25.5 Lvo 8 4 7 3.5 2 1 Qp + Chert 30 15 23 11.5 26 13 Lsm 50 25 40 20 51 25.5 Lmi sc 6 3 0 0 1 0.5 Triads of percentages used for ternary diagrams Q-F-L Q 37.4 42.1 48.7 F 19.9 25.3 22.8 L 42.7 32.6 28.5 Qm-F-Lt Qm 22.8 30.0 37.5 F 19.9 25.3 22.8 Lt 57.3 44.7 39.7 Qp-Lv-Ls Qp 15.4 11.5 13.1 Lv 58.8 68.5 61.3 Ls 25.8 20.0 25.6 P/F Ratio 0.76 0.83 0.91 93 APPENDIX 3: Modal analysis of samples from the Laminated Facies (cont.) Total Count WMI -7-C WII -5-C WII -7-C ^300 Points) # % # % # % Qm 58 19.3 76 25.3 97 32.3 P 36 12 17 5.7 17 5.7 K 4 1.3 17 5.7 5 1.7 L 50 16.7 47 15.7 40 13.3 Pump. 15 5 10 3.3 11 3.7 Cem. 129 43 122 40.7 122 40.7 Heav. 5 1.7 1 0.3 5 1.7 Misc. 3 1 10 3.3 3 1.0 Lithic Count 1200 Points) Lvl 77 38.5 54 27 51 25.5 Lvm 56 28 33 16.5 20 10 Lvo 2 1 5 2.5 3 1.5 Qp + Chert 9 4.5 26 13 42 21 Lsm 53 26.5 82 41 80 40 Lmisc 3 1.5 0 0 4 2 Triads of percentages used for ternary diagrams Q-F-L Q 42.7 55.7 69.1 F 25.5 18.6 11.0 L 31.8 25.7 19.9 Qm-F-Lt Qm 36.9 41.5 48.2 F 25.5 18.6 11.0 Lt 37.6 39.9 40.8 Qp-Lv-Ls Qp 4.6 13.0 21.4 Lv 68.5 46.0 37.8 Ls 26.9 41.0 40.8 P/F Ratio 0.90 0.50 0.77 94 APPENDIX 3: Modal analysis of samples from the Laminated Facies (cont.) Total Count EQP-l-C EQP-3 EQP-7-C 1300 Points) # % # % # % Qm 58 19.3 83 27.7 65 21.7 P 35 11.7 65 21.7 29 9.7 K 7 2.3 10 3.3 2 0.7 L 49 16.3 60 20 62 20.7 Pump. 13 4.3 5 1.7 12 4 Cem. 123 41 60 20 120 40 Heav. 11 3.7 8 2.6 5 1.6 Misc. 4 1.3 9 3 5 1.6 Lithic Count (200 Points) Lvl 67 33.5 74 37 74 37 Lvm 82 41 55 27.5 63 31.5 Lvo 6 3 8 4 0 0 Qp + Chert 16 8 13 6.5 11 5.5 Lsm 27 13.5 49 24.5 52 26 Lmisc 2 1 1 0.5 1 0.5 Triads of percentages used for ternary diagrams Q-F-L Q 44.9 41.5 45.0 F 25.4 32.5 18.3 L 29.7 26.0 36.7 Qm-F-Lt Qm 35.2 35.9 38.5 F 25.4 32.5 18.3 Lt 39.4 31.6 43.2 Qp-Lv-Ls Qp 8.1 6.5 5.4 Lv 78.3 68.9 68.6 Ls 13.6 24.6 26.0 P/F Ratio 0.83 0.87 0.94 95 APPENDIX 3: Modal analysis of samples from the Laminated Facies (cont.) Total Count EQP-£!-C EQP-11 EQP-20 ^300 Points) # % # % # % Qm 60 20 55 18.3 104 34.7 P 37 12.3 35 11.7 23 7.7 K 13 4.3 13 4.33 7 2.3 L 33 11 35 11.7 53 17.7 Pump. 8 2.7 19 6.3 22 7.3 Cem. 140 46.7 132 44 85 28.3 Heav. 6 2 10 3.3 6 2 Misc. 3 1 1 0.3 0 0 Lithic Count 1200 Points) Lvl 59 29.5 57 28.5 94 47 Lvm 74 37 44 22 42 21 Lvo 0 0 1 0.5 0 0 Qp + Chert 10 5 16 8 17 8.5 Lsm 57 28.5 82 41 46 23 Lmisc 0 0 0 0 1 0.5 Triads of percentages used for ternary diagrams Q-F-L Q 45.7 46.1 59.3 F 32.7 31.2 14.7 L 21.6 22.7 26.0 Qm-F-Lt Qm 39.2 35.7 51.0 F 32.7 31.2 14.7 Lt 28.1 33.1 34.3 Qp-Lv-Ls Qp 5.0 8.0 8.6 Lv 66.5 51.0 68.3 Ls 28.5 41.0 23.1 P/F Ratio 0.74 0.73 0.77 96 APPENDIX 3: Modal analysis of samples from the Laminated Facies (cont.) Total Count WQP-1 -C WQP-2 WQP-4 ^300 Points) # % # % % Qm 78 26 66 22 75 25 p 12 4 10 3.3 16 5.3 K 8 2.7 7 2.3 11 3.7 L 37 12.3 40 13.3 44 14.7 Pump. 27 9 14 4.7 13 4.3 Cem. 122 40.7 131 43.7 122 40.7 Heav. 8 2.7 18 6.0 8 2.7 Misc. 8 2.7 14 4.7 11 3.7 Lithic Count ^200 Points) Lvl 79 39.5 77 38.5 84 42 Lvm 47 23.5 51 25.5 63 31.5 Lvo 3 1.5 2 1 2 1 Qp + Chert 30 15 18 9 17 8.5 Lsm 36 18 50 25 30 15 Lmisc 5 2.5 2 1 4 2 Triads of percentages used for ternary diagrams Q-F-L Q 65.5 59.6 56.4 F 12.1 12.0 16.6 L 22.4 41.4 27.0 Om-F-Lt .. , Qm 47.3 46.8 46.0 F 12.1 12.1 16.6 Lt 40.6 41.1 37.4 Op-Lv-Ls . _ Qp 15.4 9.1 8./ Lv 66.1 65.7 76.0 Ls 18.5 25.2 15.3 P/F Ratio 0.60 0.59 0.59 97 APPENDIX 3: Modal analysis of samples from the Laminated Facies (cont.) Total Count WQP-5 EMP-:L EMP -la (,300 Points) # % # % # % Qm 92 30.7 96 32 101 33.7 P 21 7 63 21 44 14.7 K 6 2 6 2 10 3.3 L 26 8.6 44 14.7 33 11 Pump. 22 7.3 13 4.33 6 2 Cem. 118 39.3 53 17.7 84 28 Heav. 12 4 11 3.7 7 2.3 Mi sc. 3 1 14 1^.1 15 5 Lithic Count (200 Points) Lvl 90 45 72 36 55 27.5 Lvm 45 22.5 57 28.5 62 31 Lvo 3 1.5 4 2 1 0.5 Qp + Chert 21 10.5 36 18 31 15.5 Lsm 41 20.5 29 14.5 48 24 Lmisc 0 0 2 1 3 1.5 Triads of percentages used for ternary diagrams Q-F-L Q 68.1 53.8 60.3 F 16.3 28.2 24.7 L 15.6 18.0 15.0 Qm-F-Lt Qm 55.4 39.2 46.1 F 16.3 28.2 24.7 Lt 28.3 32.6 29.2 Qp-Lv-Ls Qp 10.5 18.2 15.7 Lv 69 67.2 59.9 Ls 20.5 14.6 24.4 P/F Ratio 0.78 0.91 0.81 98 APPENDIX 4: Modal analysis of samples from the Shaley Facies. Total Count WMI -12 WII -15 WII -14 (,300 Points) # % # % # % Qm 46 15.3 51 17 40 13.3 P 93 31 47 15.7 48 16 K 12 4 2 0.7 4 1.3 L 31 10.3 33 11 38 12.7 Pump. 0 0 18 6 10 3.3 Cem. 104 34.7 132 44 146 48.7 Heav. 8 2.7 6 2 8 2.7 Misc. 6 2 11 3.7 6 2 Lithic Count ^200 Points) Lvl 67 33.5 94 47 72 36 Lvm 28 14 63 31.5 52 26 Lvo 13 6.5 2 1 4 2 Qp + Chert 65 32.5 15 7.5 18 9 Lsm 26 13 25 12.5 53 26.5 Lmisc 1 0.5 1 0.5 1 0.5 Triads of percentages used for ternary diagrams Q-F-L Q 44.9 44.6 39.2 F 42.5 33.1 35.1 L 12.6 22.3 25.7 Qm-F-Lt Qm 18.6 34.5 27.0 F 42.5 33.1 35.1 Lt 38.9 32.4 37.9 Qp-Lv-Ls Qp 32.7 7.5 9.1 Lv 54.3 79.9 64.3 Ls 13.0 12.6 26.6 P/F Ratio 0.89 0.96 0.92 99 APPENDIX 5: Average modal compositions for 30 samples plotted on ternary diagrams (Figures 21, 22, & 23). Standard Mean Deviation Variance Q 52 8.55 73.1 F 22 7.99 63.9 L 26 7.39 54.6 Qm 40 8.05 64.7 F 22 7.99 63.9 Lt 38 6.32 40.0 QP 12 6.39 40.9 Lv 65 11.10 122.4 Ls 23 9.06 82.1 P/F 0.75 0.16 0.03 100 101 Quimper Peninsula 102 and the (modified west east Miller Quimper from Allison, Peninsula Peninsula 1959).