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P a c h t , Jo r y A l l e n
SEDIMENTOLOGY AND PETROLOGY OF THE LATE CRETACEOUS NANAIMO GROUP IN THE NANAIMO BASIN, WASHINGTON AND BRITISH COLUMBIA: IMPLICATIONS FOR LATE CRETACEOUS TECTONICS
The Ohio State University Ph.D. 1980
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20C \ ; = = = =0. A N N A330S VI1 asi 06 ''3121 761-4700 SEDIMENTOLOGY AND PETROLOGY OF THE LATE CRETACEOUS NANAIMO GROUP
IN THE NANAIMO BASIN, WASHINGTON AND BRITISH COLUMBIA:
IMPLICATIONS FOR LATE CRETACEOUS TECTONICS
DISSERTATION
Presented in Partial Fulfillment of the Requirements for
the Degree, Doctor of Philosophy in the Graduate
School of the Ohio State University
By
Jory A. Pacht B.S., M.S.
The Ohio State University
1980
Reading Committee Approved by
Dr. Kenneth O. Stanley
Dr. Stig M. Bergstrom
Dr. Charles H. Summerson
Dr. John F. Sutter
Department of Geology & Mineralogy ACKNOWLEDGEMENTS
First and foremost I would like to thank my dissertation advisor Dr. Kenneth 0. Stanley for supervising my research and painstaking ly editing this dissertation. Discussions with Dr. Stanley, con cerning not only this project but the nature and process of scien tific research as well, have improved this dissertation by several orders of magnitude. 1 also give my sincere thanks to the other members of my committee, Drs. John S. Sutter, Stig M. Bergstrom and Charles H. Summerson, who each edited portions of the dissertation when Dr. Stanley was called away on a personal emergency. Dr. Peter D. Ward, from the University of California-Davis, spent ten days in the field with me at the onset of this project and helped to famili arize me with Nanaimo geology.
I am also grateful to Ms. Mary Coldwell, of ARCO Oil Company, for her competent and professional typing of this dissertation.
I would like to acknowledge the residents of the Gulf and San Juan Islands, who continually encouraged me, usually when I was tres passing on their land and knocking off hunks of their valuable ocean front real estate. Ms. Sally Seagraves, owner of North Beach Inn on Orcas Island and Ed and Hillary Hall on North Pender Island, were especially hospitable.
This project was partially funded by grants of Sigma Xi, American Association of Petroleum Geologists, ARCO Oil Company, and the Friends of Orton Hall Fund of the Ohio State University.
Last, but not least, I would like to thank my parents for their continued love and support. VITA
Ohio State University 9/76- Columbus, Ohio Ph.D.
University of Wyoming 8/74-7/76 Laramie, Wyoming M.S.
Ohio University 9/69-3/73 Athens, Ohio B.S.
PUBLICATIONS
1976, Depositional Environments and Diagenesis of the Nugget Sandstone, western Wyoming and northeastern Utah: Unpub. M.S. Thesis, University of Wyoming, 99 p. - Dr. J.R. Steidtmann, advisor.
1977, Diagenetic History of the Nugget Sandstone, western Wyoming and northeastern Utah: Geol. Soc. America Abstracts with Programs, v. 9, no. 5, p. 639.
1977, Diagenesis of the Nugget Sandstone, western Wyoming and north eastern Utah: iri E. L. Hiesey and D. E. Lawson (eds.), Mountain Thrust-Belt Geology and its Resources, Wyoming Geol. Assoc. Guide book, 29th Ann. Field Conf., p. 207-219.
1979, Depositional Environments of the Late Cretaceous Nanaimo Group, within the Nanaimo Basin, British Columbia and Washington: Geol. Soc. America Abstracts with Programs, v. 11, no. 3, p. 121.
1980, Submarine Fan Facies in the Lower Nanaimo Group, Vancouver Island Region, submitted to Canadian Jour. Earth Sci.; with P. W. Ward and K. O. Stanley.
INVITED PRESENTATIONS
J.978, Cathodoluminescence observations in diagenetic studies of the Nugget Sandstone: Nuclide Corporation Cathodoluminescence Workshop, at Geol. Soc. America National Mtg., Toronto.
FIELDS OF STUDY
Tectonics and Sedimentation. Field and laboratory studies invol ving depositional environments, sediment provenance, sedimentary petrography and digenesis.
iii TABLE OF CONTENTS
Page ACKNOWLEDGEMENTS...... ii
VITA...... iii
LIST OF TABLES...... vi
LIST OF FIGURES...... v
LIST OF APPENDICES...... xiv
INTRODUCTION...... 1
PREVIOUS RESEARCH...... 3
GEOLOGIC SETTING...... 9
STRATIGRAPHY...... 19
SEDIMENT DISPERSAL DATA...... 32
PETROGRAPHY...... 44
Petrographic methods...... 44 Quartz types...... 45 Feldspar types...... 46 Lithic Fragments...... 46 Heavy Minerals...... 48 Interstitial Components...... 49 Diagenesis...... 50 Petrofacies...... 57 Statistics...... 58 High-plagioclase Arkose Petrofacies...... 66 High-plagioclase Arkose #1 Petrofacies...... 67 High-plagioclase Arkose #2 Petrofacies...... 72 Chert-rich Lithic Arenite Petrofacies...... 73 Lithic Arkose Petrofacies...... 78 Dacite-rich Arkose Petrofacies...... 85 Basalt-bearing Lithic Arenite Petrofacies...... 89 Petrologic Evolution of the Nanaimo Basin...... 94
DEPOSITIONAL ENVIRONMENTS AND SETTING...... 106
Nonmarxne Deposits...... 1 07
iv Page Conglomerate Facies...... 107 Interpretation of Sedimentary Features in the Conglomerate Facies...... 110 Sandstone Facies...... 113 Interpretation of Sedimentary Features in the Sandstone Facies...... 124 Coal, Shale and Siltstone Facies...... 125 Marginal-Marine Facies...... -...... 128 Sandstone-Conglomerate Facies...... 128 Interpretation of Sedimentary Features in the Sandstone-Conglomerate Facies...... 149 Siltstone-shale Facies...... 158 Shale Facies...... 161 Facies Relationships in Nonmarine and Marginal-Marine Deposits...... 151 Submarine-fan Deposits...... 156 Clast-Supported Conglomerates and Pebbly Sandstones (Facies A )...... 156 Interpretation of Sedimentary Features in Clast- Supported Conglomerates and Pebbly Sandstones...... 175 Massiye Sandstones (Facies B)...... 179 Interpretation of Sedimentary Features in Massive Sandstones...... 189 Classic Turbidites...... 190 Matrix-Supported Conglomerates and Chaotic Deposits (Facies F)...... 194 Interpretation of Sedimentary Features in Facies F ...... 197 Injection Features...... 200 Submarine-fan Facies Sequences...... 200 Fining-Upward Sequences...... 200 Coarsening-Upward Sequences...... 219 Noncyclic Sequences...... 219 Interpretation of Facies Sequences...... 222 Submarine-fan Facies Geometry...... 226 Stratigraphic Patterns of Submarine-fan Deposits...... 229 Depositional Model of Submarine-fan Deposits in the Nanaimo Basin...... 236 Relationships Between Nonmarine, Marginal-Marine, and Submarine-fan Environments...... 247 Interpretation of Transitional Sequences...... 255
PALEOGEOGRAPH Y ...... 258
TECTONIC IMPLICATIONS...... 270
BIBLIOGRAPHY...... 283
LIST OF ABBREVIATIONS USED IN APPENDICES...... 298
APPENDICES...... 301
v LIST OF TABLES
Table Page
1. Formational nomenclature and biostratigraphic zonation of the Nanaimo Group ...... ®
2. Pre-Late Cretaceous rocks of Vancouver Island ...... 10
3. Major rock-types of the Coastal Plutonic Belt ...... 15
4. Major pre-Late Cretaceous rocks of the North Cascades . . . 16
5. Major pre-Late Cretaceous rock-types of the San Juan Islands ...... 18
vi LIST OF FIGURES
Figure Page
1 Map showing distribution of the Nanaimo Grc p and sur rounding tectonic provinces...... 5
2 Stratigraphic sections in the southern portion of the Nanaimo Basin, aligned east to west...... 21
3 Stratigraphic sections in the Nanaimo Basin aligned from the northwest corner of the basin to the southeast corner...... 23
4 Geography of the Nanaimo Basin...... 25
5 Parting lineation in the Extension Formation at Cusheon Creek, SaltSpring Island...... 34
6 Groove casts in the Cedar District Formation at Bedwell Harbor, North Pender Island...... 36
7 Giant flute casts in the Extension Formation on Barnes Island...... 36
8 Paleocurrent measurements in the Nanaimo Basin...... 38
9 Structural geology of Waldron Island...... 41
10 Microphotograph of calcite cemented sandstone containing euhedral crystals of laumontite...... 52
11 Microphotograph showing alteration of amphibole grains to chlorite and inhomogenous matrix...... 52
12 Microphotograph of thin-section showing replacement of plagioclase by zeolite...... 55
13 Microphotograph of thin-section showing zeolite (laumontite) pore-filling cement...... 55
14 QFL diagram of petrofacies of the Nanaimo Group...... 60
15 Ternary diagram showing relative percentages of volcanic sedimentary and metamorphic rock-fragments in each petro facies...... 62
vii Figure Page
16 Plagioclase/total feldspar ratios for each petrofacies...... 64
17 Photomicrograph of thin-section of high-plagioclase arkose #1 from the Decourcy Formation at Dinner Bay, Mayne Island.. 69
18 Petrofacies distribution in the Nanaimo Basin...... 71
19 Photomicrograph of chert-rich lithic arenite from the Haslam Formation in the Cowichan River area...... 75
20 Photomicrograph of thin-section of a lithic arkose from the Decourcy Formation on Sucia Island...... 80
21 Outcrop of quartz-phyllite conglomerate in the Protection Formation at Fossil Bay, Sucia Island...... 84
22 Outcrop of Darrington Phyllite near Wickersham Washington... 84
23 Outcrop of boulder conglomerate containing gneissic clasts in the Extension Formation on Waldron Island...... 87
24 Photomicrograph of thin-section of dacite-rich arkose from the Cedar District Formation at Southey Point, Saltspring Island...... 91
25 Photomicrograph of thin-section of basalt-bearing lithic arenite from the Extension Formation along the Nanaimo River...... 91
26 QFL diagram comparing Nanaimo rocks deposited during B. elongatum to B. chicoens.is zone time (largely chert- rich lithic a'renites) and those deposited during H. vancouverense to P. suciaensis zone time (largely lithic arkoses) in the San Juan Islands...... 96
27 QFL diagram showing gradation from chert-rich lithic arenites to high-plagioclase arkoses on South Pender Island and at Cusheon Creek on Saltspring Island. Dia gram also illustrates gradation from chert-rich lithic arenites to lithic arkoses to high-plagioclase arkoses on Saturna Island...... 100
28 Ternary diagram illustrating change in rock-fragment composition in samples taken from Protection and Cedar District formations on Saturna Island...... 103
29 Idealized section illustrating sedimentary structures of the conglomerate facies...... 109 viii Figure Page
30 Disorganized fabric in conglomerate from the non marine conglomerate facies in the Extension Formation along the Nanaimo River...... 112
31 Cross-bedded conglomerate from the nonmarine conglom erate facies in the Extension Formation along the Nanaimo River...... 112
32 Idealized stratigraphic section illustrating sedimentary structures of the nonmarine sandstone facies...... 116
33 Cross-bedding in nonmarine sandstone facies. Note back set bedding in ripple cross-lamination at the base of the cross-bed foresets. Outcrop is Extension Formation along the Naniamo River...... 118
34. Mega-ripples along a bedding plane in the nonmarine sandstone facies of the Extension Formation along the Nanaimo River...... 118
35 Horizontal stratification in nonmarine sandstone facies of the Extension Formation along the Nanaimo River...... 120
36 Large-scale planar cross-stratification in the Protection Formation on Newcastle Island...... 123
37 Interbedded coal, very fine-grained sandstone, siltstone and shale in the Pender Formation on Newcastle Island...... 127
38 Stratigraphic section of the Decourcy Formation from Sucia Island showing typical sedimentary structures of the sandstone-conglomerate marginal marine facies...... 130
35 Low-angle inclined stratification in the Decourcy Formation on Sucia Island...... 132
40 Trough cross-stratification in sandstone-conglomerate marginal-marine facies. Outcrop in the Protection Formation on Newcastle Island...... 135
41 Current ripples superimposed on a cross-bed foreset. Sediment-transport direction measured for ripples is perpendicular to direction measured on cross-bed foreset. Outcrop is Protection Formation located 4 to 6 km south of the town of Nanaimo...... 137
42 Reactivation surfacies between cross-bed sets. Out crop is Decourcy Formation on Sucia Island...... 139
43 Herringbone cross-bedding. Outcrop is Decourcy Formation on Sucia Island...... 139 ix Figure Page
4 4 Interbedded conglomerate and sandstone beds. Out crop is Decoury Formation on Sucia Island...... 142
4 5 Accumulation of Ostrea sp. shells in sandstone. Out crop is Extension Formation on Waldron Island...... 142
4 6 Horizontal stratification in very fine-grained sandstone of the Decourcy Formation on Sucia Island..... 144
4 7 Flaser bedding in the Protection Formation on Newcastle Island...... 146
48. Mud-chip intra-formational conglomerate in the Protection Formation on Newcastle Island...... 148
4 9 Idealized high-energy, barred shoreline profile...... 151
50 Comparison between stratigraphic section measured on Sucia Island and that measured by Clifton of the marginal-marine facies in the Miocene Branch Canyon Sandstone...... 153
5 1 Lag-accumulation of bivalve shell fragments in siltstone- shale marginal-marine facies in the Cedar District Formation at Fossil Bay on Sucia Island...... 160
52 Idealized stratification sequence illustrating sedimentary features of facies A submarine-fan conglomerates...... 168
5 3 Disorganized conglomerate from the Decourcy Formation near Dinner Bay on Mayne Island...... 130
54 Inverse grading in the Protection Formation at Ilouut Point, North Pender Island...... 172
5 5 Normal-grading in conglomerate bed in the Extension Formation along the south coast of South Pender Island... 174
56 A(p) a(i) clast orientation in the Extension Formation on the north coast of Barnes Island...... 174
57 Cross-bedding in conglomerate bed in the Extension Formation on the south coast of South Pender Island...... 177
58 Idealized stratigraphic section showing sedimentary features of facies B submarine-fan sandstones in the Nanaimo Basin...... 182
5 9 Massive structureless sandstones in the Decourcy Formation Formation south of Dinner Bay on Mayne Island...... 184 x Figure Page
60 Lutite clasts in facies B sandstones in the Cedar District Formation at Southey Point, Saltspring Island...... • 184
61 Dish structures in sandstones of the Decourcy For mation at Dinner Bay, Mayne Island...... 186
62 Horizontal stratification in facies B sandstones of the Gabriola Formation near Edith Point...... 186
63 Gradation from horizontal to wavy to convolute bedding in sandstones of the Cedar District Formation on Thetis Island...... 188
64 Convolute bedding under.1 ain by shear surfaces (dotted lines) in the Protection Formation at Mouat Point, North Pender Island ...... 188
65 Facies C turbidite exhibiting Taj-,ccie bedding. Outcrop is the Haslam Formation on Barnes Island...... 193
6 6 Facies D turbidites exhibiting Tfc>cde and Tccje bedding. Outcrop is the Cedar District Formation near Mouat Point, North Pender Island...... 1 9 3
67 Starved ripples in Bouma C division in facies E turbidites in the Northumberland Formation near Dinner Bay, Mayne Island...... 196
6 8 Matrix-supported conglomerate with siltstone matrix. Outcrop is in the Cedar District Formation on Saturna Island...... 19.9
69 Slump structure in the Cedar District Formation near Gallagher Bay, Mayne Island...... 202
70 Sandstone dike in the Cedar District Formation north of Boat Harbor on Vancouver Island. Note large concretion in the shale and associated slumping...... 2 0 2
71 Facies A,B fining-upward sequences in the Decourcy Formation near Dinner Bay, Mayne Island...... 205
72 Facies B,C fining-upward sequences in the Cedar District Formation at Ganges Harbor, Saltspring Island...... 205
73 Detailed stratigraphic section of a portion of the Pro tection Formation at Mouat Point, North Pender Island, showing series of facies A,B fining-upward sequences...-207
xi Figure Page
74 Diagram illustrating changes in sandstone percentage, sandstone bed thickness, and Bouma bedding divisions that occur within a typical facies C,D fining-upward sequence...... 209
75 Detailed stratigraphic section of a portion of the Cedar District Formation at Southey Point, Salt spring Island, illustrating facies C,D and some facies B,C,d fining-upward sequences...... 211
76 Detailed stratigraphic section of a portion of the Cedar District Formation near Mouat Point, North Pender Island, showing facies C,D and facies D fining- upward sequences. Some of these sequences grade into noncyclic sequences...... 213
77 Fining-upward sequence in facies C and D turbidites of the Cedar District Formation near Gallagher Bay, Mayne Island...... 215
78 Lenticular beds of facies B sandstones which are replaced laterally by facies E turbidites. Outcrop is located south of Southey Point, Saltspring Island...... 217
79 Detailed stratigraphic section of coarsening- upward sequences composed of facies B,C, and D turbidites. This outcrop is in the Protection Formation along the south coast of South Pender Island. The stratigraphic section is somewhat idealized...... 2 2 1
80 Coarsening-upward sequences in the Protection Formation along the south coast of South Pender Island...... 224
81 Noncyclic sequence of very thin-bedded Tc3 e turbidites in the Northumberland Formation at Dinner Bay, Mayne Island...... 225
82 Stratigraphic sections in the Nanaimo Basin aligned northwest to southeast illustrating relationships between nonmarine, marginal-marine and submarine- fan facies...... -231
83 Stratigraphic sections in the southern Nanaimo Basin aligned west to east illustrating relationships between nonmarine, marginal-marine, and submarine-fan facies...... 233
84 Environmental model typical of submarine-fans which develop in areas unrestricted by basin morphology and by input of sediment from a single source...... 239
xii Figure Page
3 5 Interpretative model of submarine-fan geometry in the Nanaimo Basin...... 241
8 6 Block diagram illustrating development of fining- upward, coarsening-upward, and noncyclic sequences in submarine-fan sequences of the Nanaimo Basin...... '244
87 Outcrop of facies D turbidites in the Cedar District Formation near the Nanaimo River on Vancouver Island...... 250
8 8 Sandstone bed in facies D turbidites shown in figure 87. Sandstone bed is characterized by a pillow structure...... 251
89 Detailed stratigraphic section of the Protection Formation and the lowermost Cedar District Formation on Saturna Island.This section illustrates transition from marginal- marine facies to submarine-fan facies...... 254
90 Block diagram illustrating paleogeography of the Nanaimo Basin...... 262
91 Paleogeographic map of the Nanaimo Basin illustrating approximate position of surounding tectonic provinces and basin morphology...... 264
92 Tectonic map of the west coast of northern Washington and southern British Columbia illustrating major faults and rock types...... 274
xiii LIST OF APPENDICES
Appendix Page
I. Compositional data for all r o c k s ...... 301
II. Detrital compositions of rocks in eachpetrofacies . . . 313
III. Factor loading for rocks in each petrofacies...... 321
IV. Stratigraphic sections ...... 328
xiv INTRODUCTION
The western Cordillera of southern Canada and the northwest region of the United States is an "orogenic collage" that consists of autoch
thonous and al1ochthonous rock assemblages of different ages and paleo-
geographic settings. These rocks were brought together by diverse tec
tonic processes (Davis et al. , 1978). The Nanaimo Basin is bounded by four of these major tectonic provinces: allochthonous rocks of the western North Cascades ("Cascadia," defined by Davis et al. , 1978), the
San Juan Islands (allochthonous terranes discussed by Whetten et al. ,
1978), Vancouver Island ("Wrengellia," defined by Jones et al. , 1977); and the autochthonous Coastal Plutonic Belt. The Nanaimo Group,
deposited in the Nanaimo Basin, is composed of detritus from all four of
these terranes. Examination of depositional environments, paleocurrents
and sandstone and conglomerate petrology in the Nanaimo Basin provides information concerning structural evolution of the basin and tectonic
activity in surrounding terranes.
Outcrops of the Santonian to Maestrichtian (Ward, 1976, 1978)
Nanaimo Group, deposited in the Nanaimo Basin, are located on southeast ern Vancouver Island and the Gulf Islands in British Columbia and the
San Juan Islands of Washington. The Nanaimo Basin is the southern por
tion of the Georgia Basin, which includes outcrops of the Nanaimo Group
to the north (Eisbacher, 1974). This project involved 5 months of field research in the Nanaimo
Basin conducted during the summers of 1977 and 1978. Eleven (11) stratigraphic sections were measured in detail. (Appendix IV).
Sedimentary structures, stratification sequences and paleocurrents were noted at localities throughout the Nanaimo Basin. Thin sections from 19 localities were point-counted. Thin sections from other localities were also examined.
The purpose of this dissertation is to examine geographic and chronologic changes in depositional environments and both sandstone and conglomerate petrofacies. These data are used to determine the paleo- geographic and tectonic history of the Nanaimo Basin and to evaluate regional tectonic setting in terms of this history. PREVIOUS RESEARCH
The Late Cretaceous Nanaimo Group has been the subject of geologic research since the 1850's. Newberry (1857) first established a Creta ceous age for deposits of "coal bearing strata" near the town of
Nanaimo. Richardson (1872), working in coal fields of central and southern Vancouver Island, noted that Cretaceous deposits outcrop in discrete areas, which he termed the Comox, Cowichan, and Nanaimo Basins
(figure 1). Dawson (1887, 1890) worked on correlative rocks in the
Suquash Basin (figure 1), and he proposed that the entire succession be termed the Nanaimo Group. Subsequently, Clapp (1912, 1917) subdivided the Nanaimo Group into formations based on studies near the town of
Nanaimo. Both Clapp (1912) and Usher (1951) applied a different strati graphic terminology for Upper Cretaceous rocks in the Comox and Nanaimo
Basins. In addition, Usher (1951), included the Cowichan Basin as part of the Nanaimo Basin. He defined the Nanaimo Basin as that area that
'occupies the southeast corner of Vancouver Island and extends southeast from Nanoose Bay to the International Boundary and into United States waters for another ten miles to include the islands of Sucia, Patos,
Waldron, Spieden, Matia, Stuart and Johns. It is limited on the east by the Strait of Georgia and on the west by crystalline rocks of the east ern slopes of the Vancouver Island Ranges and by the southeast side of
Cowichan Lake and Cowichan River Valley, which together comprise
3 Figure 1. Map showing distribution of the Nanaimo Group and the surrounding provinces. SUQUASH BASIN
fe\ \(W ■ ^ c c W ^
VANCOUVER BASIr^ Rivor A t m Q VA N C O U V E R * ,* * .' r 5 1' r *vp ■ i V* ?>OCANADA * • ' NANAIMO'**?^ y ~ ' > U.&A. ‘ ” 7 ' - . ^ ' /"‘'T'A'ir '‘‘7 T ( \\ V-V • \ ''oV' -O'"',-'',‘Vo B ^ I N - \ V ,vi1 v\i'» -? v\ ^ \ ' ; Cdwlchan- ^ . > ^ D JP) tv«r Ar»a \ F ^ i W N O R J H *s > \V c L**Jwrengel lian and Middle Mesozoic SAN JUAN I. ’Jrrfj CASCADES Rocks of Vancouver Island
Terranes of the Son Juan Islands
North Cascades
.'■•‘I Coastal Plutonic Belt (j SEATTLE \ I < / > s M&M Nanaimo Group 100km. fessgssa the'Cowichan Lowland'". This definition will be followed in this paper.
For the purpose of description, however, the terras "Cowichan River area" and "Nanaimo River area" will be used. The Cowichan River area
(figure 1) includes outcrops of the Nanaimo Group on Vancouver Island in the Cowichan and Chemainus River drainage systems. The Nanaimo River area is that region drained by the Nanaimo River. This area includes
Nanaimo Group rocks in and around the town of Nanaimo and on Newcastle and Protection Islands (figure 1).
Muller and Jeletzky (1970) produced the first detailed geologic map of the Nanaimo and Comox basins. They also developed a unified strati graphic nomenclature for the Comox and Nanaimo basins and detailed bio- stratigrphic zonation for Nanaimo Group deposits, based on range zones of ammonites and inocerami. Ward (1976, 1978, Table 1) proposed revi sions to formational nomenclature and biochronology of the Nanaimo
Group. 7
Table 1. Biostratigraphy and formational nomenclature of the Nanaimo Group in the Nanaimo Basin (after Ward, 1978). AGE ZONE FORMATION
GABRIOLA: Sandstone, MAESTRICHTIAN Cohglomerate o . 7 ...... • a SPRAY 5 Shale,Classic turbidites
R S U C I E N S I S
GEOFFREY 5 Sandstone, LATE Conglomerate CAMPANIAN NORTHUMBERLAND 5 Shale, Classic turbidites
PACIFICUM - SUCIENSIS DE C O U R C Y 5 Sandstone, BARREN INTERZONE Conglomerate
M. PACIFICUM ------CEDAR DISTRICT5 Shale. Classic turbidites,Sandstone,Siltstone H. V A N C O U V E R E N S E PROTECT lONSandst.,Conglomerate B.’CHICOENSE ...... 1 P E N D E R :Shale,Classic turbs-jSlltst. EARLY EXTENSION 5Conqlomerate,Sandst. CAMPANIAN 1. SCHMIDT! HASLAM 5 Shale,Classic turbidites |jE. haradi Subz. _ M ncouwwnse B. E L O N G A T U M j Zonu,e S ANTON IAN COMOX 5 Sandstone, Conglomerate 1 1. naumanni Subz. 1 GEOLOGIC SETTING
The Nanaimo Basin is bounded by four major tectono-stratigraphic provinces characterized by distinctive rock-types (figure 1). Paleozoic and Early Mesozoic rocks of Vancouver Island form the western and north ern margins of the basin and underlie Nanaimo strata. The Coastal Plu tonic Belt forms the eastern margin of the basin. The Nanaimo Basin is bordered along its southern margin by Paleozoic and Early Mesozoic rocks of the San Juan Islands, which are in thrust fault contact with Nanaimo rocks, and along its southwestern margin by Paleozoic and Mesozoic rocks of the North Cascades. Major rock~types of each of these areas are listed in Tables 2 to 5.
Vancouver Island is part of a tectonic province termed Wrengellia by Jones and others (1977). Wrengellia is a large subcontinental block which is composed of Upper Paleozoic (Sicker Group) and Middle to Late
Triassic rocks (Karmutsen Basalt, Quatsino Limestone, Parson Bay Forma tion and equivalents, Table 2) that extends from southern Alaska to
Vancouver Island. Similar rocks may occur in the Seven Devils Volcanic
Arc in Oregon (Jones et al. , 1977; Muller, 1977a; Davis et al. , 1978).
Wrengellia includes much of the Insular Belt (Sutherland-Brown, 1968,
Muller, 1977) which is the westernmost portion of the Canadian and southeastern Alaskan Cordillera. Rocks of Vancouver Island are shown in
Table 2.
9 Table 2 PRE-NANAM) ROCKS OF VANOQUVER ISLAND
Sequential layered Rocks
Period Group Formation Name Lithology
QUEEN conglanerate, greywacke Middle I)1 CHAKLOTIE slltstone, shale Early LONGARM greywacke, conglanerate, slltstone
unnamed slltstone, argillite, conglanerate Late sedimentary rocks uk-l
Early to unnamed volcanics basaltic to rtyolitlc lava, tuff, breccia, minor argillite, greywacke Middle I BONANZA HARBLEDCWi argillite, greywacke, tuff
Middle to PARSON BAY calcareous slltstone, greywacke, silty-llmestone, minor conglomerate, t-l Late VANCOUVER QUATSItT) limestone KARMUTSEN basaltic lava, pillow lava, breccia, tuff 2 unnamed sedimentar f metasiltstone, diabase, limestone Early to rock-sill unit -■ * Middle
BUHLE LAKE limestcne, chert SICXER unnamed nedin'ent- metagreywacke, argillite, schist, marble $ ary-volcanic rocks basaltic to rhyolltlc metavolcanic flc*«, tuff, agglcnerate
From Muller, 1977b
O
From Muller, FromMuller, 1977b monzonite Lithology metaquartzite, marble gneiss, quartz-feldspar granodiorite, quartzdiorite, granite, quartz granite, quartzdiorite, granodiorite, quartz feldspar gneiss feldspar quartz amphibolite diorite, gneissfquartz hornblende-plagioclase metagranodiorite, metaquartz diorite, metaquartz porphyry metaquartz diorite, metaquartz metagranodiorite, greywacke, argillite, chert, mlcanics, basic chert, argillite, greywacke, limestone hornblende-plagioclase quartz gneiss, diorite, agmatite marble Crystalline Complexes K/AR 163-192 163-182 141-181 U/Pb
Table 2 cont. ISLAND VANCOUVER FRE-NANAM) OF ROCKS Silicic Silicic 264 Basic Basic and Intermediate Rocks Rocks Name c o a s t DIORITE GNEISS DIORITE COMPLEX GNEISS 00LQUITZ >390 ISLAND ISLAND INMJSIONS TYEE INTRUSIONS >390 WARK WARK PACIFIC RIM COMPLEX RIMPACIFIC WEST ages. must Therefore ages. be they highly regarded as tentative.
Jurassic Devonian? NOTE: No was withdata which analytical available to critically K-Ar U-Pb analyze and Period 12
The Upper Paleozoic Sicker Group is composed of basaltic to
rhyolitic volcanics, overlain by detrital rocks which have been
subjected to low grade metamorphism. These metamorphosed clastic
sediments are overlain by limestone and chert. This sequence has been
interpreted as a volcanic'arc assemblage by Dickinson (1976) and Muller
(1977a). Overlying Triassic rocks, in order, include very thick
sequences of basalt (Karmutsen Formation) overlain by carbonate
(Quatsino Limestone) and clastic rocks (Parsons Bay Formation). The
Karmutsen Formation may have developed during a major Middle to Late
Triassic episode of rifting (Dickinson, 1976; Jones et al., 1977;
Muller, 1977).
The Jurassic is characterized by the granodioritic Island Intru
sions and coeval Bonanza Group, which probably represent igneous activ
ity along a Mesozoic volcanic arc. The Wark and Colquitz Gneisses, and
the Tyee Intrusions (Table2) may be related to this Jurassic arc
sequence. U-Pb ages determined from zircons indicate that these
gneisses are approximately 390 m.y. old (Wanless, as quoted by Muller,
1977a). However, the Tyee Intrusions extend southeast onto Saltspring
Island, where they intrude rocks of the Sicker Group, which are
identical in lithology to those on Vancouver Island containing Middle
Pennsylvanian fossils. Muller (1977b) reports that K-Ar ages determined
for the Wark Diorite Gneiss (minerals from which these ages were
determined are not reported) range from 163 to 182 m.y. Muller (1977a)
states that the Wark and Colquitz Gneisses and the Tyee Intrusions may
represent Devonian basement that was migmitized and remobilized, with 13 retention of old zircon ages, and intruded at a later date. Therefore, the Tyee Intrusions may have intruded Upper Paleozoic rocks of the
Sicker Group during the Jurassic at the same time as the Island
Intrusions. This same intrusive event may have reset minerals in the
Wark and Colquitz Gneisses, giving Jurassic K-Ar ages.
On northern Vancouver Island, the Island Intrusions are overlain by post-intrusive unnamed sedimentary rocks deposited during the Late
Jurassic and the Lower Cretaceous Longarm Formation and Queen Charlotte
Group.
Vancouver Island is dominated by two sets of Cretaceous and Ter tiary, high-angle faults that trend to the northwest and northeast.
Muller and Jeletzky (1970) believe that these structures reflect hori zontal tension and vertical crustal movement rather than compression.
They further state that development of these structures was associated with depresssion of the Georgia Basin.
The Coastal Plutonic Complex is a long, narrow terrane dominated by intrusive rocks, which extends along the west coast of Canada from close to the British Columbia-Washington border into Alaska. The southern portion of the Coastal Plutonic Complex can be divided into western and eastern belts, in which plutonism occurred in discrete pulses. In the western belt two distinct pulses are defined by isotopic age determina tions. K-Ar ages on hornblende and biotite in rocks of the western belt range from 158 to 140 m.y. and from 120 to 90 m.y. In the eastern belt, most K-Ar dates on biotite and hornblende range from 65 to 30 m.y.
(oral comm., Armstrong, 1978; Roddick et al., 1977). Extensive areas of 14
metasedimentary and metavolcanic rocks occur as pendants within Coastal
Plutonic Complex (Table 3; Roddick, 1965).
Pre_Cretaceous rocks of the North Cascade Mountains extend from the southern end of the Coastal Plutonic Complex south into central Washing ton. These rocks were studied by Misch (1966) who states that the North
Cascades can be divided into three belts separated by major high-angle strike-slip faults of Late Cretaceous to Early Tertiary age. These include rocks west of the Straight Creek Fault zone, rocks which outcrop between the Straight Creek and Ross Lake Fault zones, and rocks east of the Ross Lake Fault Zone (Figure 1).
Rock units west of the Straight Creek Fault Zone are possible sources of detritus deposited in the Nanaimo Basin. Two major Middle to
Upper Cretaceous overthrusts occur within this belt. Along the Church
Mountain Thrust, an Upper Paleozoic eugeosynclinal assemblage (Chilli wack Group) is thrust over the Middle Mesozoic Nooksack Group, Wells
Creek Volcanics, and Cultus Formation. Along the Shuksan Thrust, the
Shuksan Metamorphic Suite is thrust over the Chilliwack Group. Rocks of the Yellow Aster complex are emplaced in a "root zone" along the thrust margin (Misch, 1966, 1977; Table 4). Rocks of this belt are unconform- ably overlain by Eocene Chuckanut Formation (pers. comm., Johnson,
1979). Rocks in the central belt (betweeen the Straight Creek and Ross
Lake Faults) form the crystalline core of the North Cascades. It is comprised largely of the middle~to high-grade metamorphic rocks of the
Cascade River Schist and Skagit Gneiss, along with associated metaplu- tonic units (Misch, 1977; Table 4). There was probably little input Table 3 MAJOR ROCK TYPES OF THE COASTAL PLUTONIC COMPLEX
Stratigraphlc Name Age Lithology Comments
Plutonic rocks are largely quartz diorite to Plutonic and metamorphic rocks Late granodiorite. outcrop within a very heterogenous Plutonic Jurassic - Rocks are chemically equivalent to tholeiitic matrix in which discrete and Rocks Late andesite. partly discrete plutons of various Cretaceous Range from gabbro to granite. size can be discerned. Rocks more acid than adamellite are rare. Average rock composition biotite-homblende, quartz, diorite. Metamorphic rocks include granitoid gneiss, raigmatite, amphibolite.
Major Non-Plutonic Rocks
Gambier Early Andesite, dacite, tuff. Group to Exposed in Western portion Mid- Conglomerate, andesite, pyroclastic material. of Coastal Plutonic Belt Cretaceous Argillite arkose, quartzite.
Fire Lake L. Jurassic to Granulite andesite limestone, conglomerate Minor importance as a source. Group Mid-Cretaceous argillite.
Bowen Island Early to Andesitic greenstones, minor interbedded Minor importance as a source. Group Middlelriassic sedimentary rocks.
Twin Island Pennsylvanian Granulite, amphibolite, micaeous, quartzite, May include highly metamorphosed Group to Permian phyllite, schist and gneiss rocks of varying ages.
from Roddick 1965 Table 4 PRE-NANAIMO MAJOR ROCK TYPES OF THE WESTERN NORTH CASCADES
Rock Types West of the Straight Creek Fault
Structural Position Age Stratigraphlc Name Lithology
Authochtonous Late Nooksack Group Volcaniclastic greywacke, slltstone, slate, phylllte, conglomerate. rock units Cretaceous below to Wells Creek Andesitic greenstone, keratophyre, dacite, quartz keratophyre Church Mountain Volcanics minor clastic sediments. Thrust Plate Late Jurassic Late Jurassic Slltstone, shale, minor sandstone. to Triassic Cultus Formation
Allochthonous Greywacke, slate, phylllte, rock units between ribbon chert, minor conglomerate the Shuksan Thrust Late interfingers with metabasalt and and the Church Paleozoic Chilliwack Group meta-aridesite Mountain Thrust
Rock units above Late Shuksan Shuksan Metabasalts, greenschist, blueschlst. the Shuksan Thrust Paleozoic Meta Greenschist morphic Darrington Graphitic phylllte, Suite Phylllte abundant quartz veins.
Rocks exposed Devonian Gabbro to trondhjemite along the root to Yellow Aster Complex and metamorphic derivatives. of the Shuksan Precambrian Thrusts
Rock Types Between the Straight Creek Fault and the Ross Lake Fault
Chlorite grade (west) to staurolite-kyanite grade (east) Crystalline Cascade River Schist metamorphisra phylllte schist, greenschist, amphibolite, ortho- core of gaeis8, marble, metaconglomerate quartzite North Cascades Skagit Gneiss staurolite-kyanite (west) to sillimanlte grade (east) meta morphism, orthogneiss, migmitltes, orthogneisses are granodioritic to leuco-trondhjomitic
from Misch 1977 17
into the Nanaimo Basin from rocks east of the Ross Lake Fault Zone.
Whetten and others (1978) have divided Paleozoic and Early Mesozoic rocks of the San Juan Islands into six terranes (Table 5) which were tectonically juxtaposed in post Mid-Cretaceous time. All of these ter ranes, each of which represents an assemblage formed along a convergent margin, are allochthonous and may have traveled large distances (Whetten et al., 1978).
All four structural provinces surrounding the Nanaimo Basin may have been subject to Late Cretaceous tectonic events associated with development of the basin. Local uplift in portions of these provinces, during development of the Nanaimo Basin may have resulted in an in creased supply of detritus to the basin. Episodes of detrital input which are inferred by petrographic data can then be evaluated in terms of the geographic and chronologic development of the Nanaimo Basin. Table 5 FORMATIONS AND TERRANES OF THE SAN JUAN ISLANDS
Stratlgraphic Name______Age______Lithology
Sinclair Terrane Middle to foliated greywacke, argillite, bedded chert, pillow lava. Late Jurassic
Decatur Terrane Late Jurassic to Cretaceous deep-water sandstone, shale, conglomerate.
Lopez Terrane Late Jurassic to melange-like sequence of strongly foliated and highly deformed Mid-Cretaceous greywacke, argillite, pillow lava and ribbon chert.
Constitution Terrane Jurassic to Early Cretaceous volcaniclastic greywacke, tuff, pillow lava.
Eagle Cove Terrane Triassic highly deformed green tuff, black argillite and grey to green chert.
Roche Harbor Terrane Ptecambrian to complexly mixed Paleozoic limestones and plutonic rocks and Paleozoic Jurassic and Mesozoic chert.
Turtleback Intrusive Precambrian to Igneous Complex Paleozoic plutonic rocks associated andesite and volcaniclastic sediments.
Spieden Formation Jurassic to Early Cretaceous andesitic conglomerate and sandstone.
Haro Formation Late Triassic andesitic and dacitic conglomerate and sandstone.
from Whetten et al.,1978
00 STATIGRAPHY
The Nanaimo Group was deposited during the Late Santonian to Maes-
trichtian stages of the Cretaceous Period (Ward, 1978). Ward (1976,
1978) divided the Nanaimo Group into range zones, subzones and zonules based on occurrence of distinctive species of ammonites and inocerami
(Table 1). Ward also revised formational nomenclature that was develop ed by Clapp and modified by Muller and Jeletzky (1970). Stratigraphic nomenclature developed by Ward (1978) is followed in this dissertation.
Stratigraphic relationships between formations of the Nanaimo Group are shown in figures 2 and 3. Geographic location of each of these sec
tions is shown in figure 4. Research was concentrated in the B.
elongatum Zone time through the lower portion of the P_. suciaensis Zone,
time below the N. hornbyense Zonule. Paleontologic information is
sparse for the upper portion of the P_. suciaensis Zone time, and the
Geoffrey, Spray and Gabriola formations cannot be correlated with the
same degree of accuracy as formations in the lower portions of the
Nanaimo Group (oral comm., Ward, 1977).
Formation Descriptions
The Comox Formation is the basal unit of the Nanaimo Group and un-
conformably rests on pre“Cretaceous rocks of the Insular Belt. The
Comox is characterized by conglomerate and medium- to coarse-grained
sandstone with subordinate amounts of shale, siltstone and coal. The
19 2 0
Figure 2. Stratigraphic sections in the southern portion of the Nanaimo Basin, aligned from west to east. Locations given in figure 4. Some sections after Ward (1976,1978). y \\S. Pender I. Shale \\ 16 .y 'B. rex \\ Siltstone m eters ' zonule \\ Classic Turbid ites \\V__ M o u a t Sandstone P o in t // v, 11 y,-' Sucia I. M. pacificum \ \ 10 rirfP'Zt'P. Conglomerate y S a tu r n a I. Barren interzone ______FORMATION BOUNDARY CEDAR DISTRICT . DECOURCY FM...... Zonal Boundary FM.
C u s h e o n X;-.. C r e e k X;-. Barren \ interzone X X- ..■■'voncouverense 13 PROTECTION FM. C o w ic h a n B. ch/coens/s V R iv e r PENDER^ 17 FM. S t u a r t . W a ld ro n I...... ••? m ' O r c a ; I. Barren interzone ..... > CJQ.° EXTENSION -n */ -r7 a C ?.o/o o’] h jjgikiu T schmidti HASLAM FM. ',w0o&l 0.c S a a n ic h Barren ..:r B. elongatum Penninsula'’ \\ Dyo. o. interzone MB V.
14A to M 22
Figure 3. Stratigraphic sections in the Nanaimo Basin aligned from the northwest corner of the basin to the southeast corner. Locations given in figure 4. Some sections after Ward (1976, 1978) . Dinner Bay 8
5 Horton IO ;Saturna i. Bay ■ ■ / Mouat SPRAY FM. Point S u cia I GEOFFREY F Nanaimo River P. suciaensis q.".o y^M.pacificuw NORTHUMBERLAND FM 4 Southey ?" B e d w e lli Hbr.9,i Point B. rex Barren interzone Zonule DECOURCY FM. C usheon „ T h etis I. C r e e k Barren Zone unknown ^ in terzone Zone H. vancouverense unknown H. CEDAR DISTRICT FM. vancouverense
PROTECTION FM B. chicoensis 12 PENDER FM. Orcas I
Barren interzone ...... schmidti EXTENSION FM. Barren interzone
B. elongatum HASLAM FM. ■TV’rt*
crrtg, COMOX FM St.*. H aslam SHALE CZ3 SANDSTONE C reek 2 m e ters 1____| CLASSIC TURBIDITES CONGLOMERATE FORMATION BOUNDARY □ SILTSTONE Zonal Boundary to to H i COAL Figure 4. Geography of the Nanaimo Basin. Shading pattern indicates dominant depositional environment at locality. DEPOSITIONAL ENVIRONMENT
Submarine-fan NEWCASTLE Q Structural Trend
THET CANADA U.S KUPER
AYNE
c^SATURNA PENDER*^-^^, PATOS ^ SUCIA MATIA WALDRON BARNES £ Stuart i V * _ \ ^ ORCAS
6 12 18 km. 26
Comox Formation is recognized in the Nanaimo River area, the Cowichan
River area and on Saltsping, Stuart and Orcas islands. The formation is
well~exposed on the Saanich Peninsula where it is estimated to be 700-
1000 m thick (Ward, 1976).
The Haslam Formation is well developed in several localities in the
Nanaimo Basin. In the Nanaimo River area and on Saltspring Island, near
Cusheon Creek, it consists largely of massive mudstone. However, in the
Cowichan River and Saanich Peninsula (includes Piers and Pym islands)
areas, and on Orcas, Barnes, Stuart, Flattop, and South Pender Islands,
the Haslam consists of rhythmic sequences of sandstone-shale interbeds
exhibiting "classic" turbidite (Walker, 1978) bedding. These units,
however, are commonly intercalated with thick mudstone beds.
Ward (1978) divides the Haslam Formation into two members: the
Haslam Creek Member, dominated by sandy siltstone and mudstones, and the
overlying Cowichan Member, characterized by rhythmic Bouma sequence bed
ding. However, the stratigraphic relationship postulated by Ward for
the Haslam Creek and Cowichan Members cannot be demonstrated at many
localities with Haslam outcrops. Instead, massive mudstone units and
units containing Bouma sequence bedding intertongue. Ward (oral comm.,
1978) agrees that the Haslam Creek and Cowichan Members are very diffi
cult to define.
Ward (1978) estimates that the Haslam is approximately 500 meters
thick in the Cowichan River area. The Haslam is only about 150 meters
thick, however, along the Nanaimo River. On Saltspring Island, the
Haslam Formation is approximately 200 meters in thickness. This forma 27 tion thickens greatly in the southern portion of the Basin. Ward (1978) estimates that the Haslam is 500 meters thick in the Cowichan River area. Ward (1978) also notes that the Haslam Formation is 600 meters thick on Stuart Island and over 400 meters thick in the Saanich Penin sula area (Piers Island).
The Extension Formation is dominantly conglomerate and sandstone.
Rare siltstone, shale and coal beds are also present. Outcrops of this formation are present in the San Juan Islands, the southwestern Gulf
Islands, the Cowichan River area and the Nanaimo River area. The Exten sion Formation is very thick in the southeastern portion of the basin.
On South Pender Island, over 480 meters of Extension conglomerates are present, and on Waldron Island over 300 meters of conglomerates and coarse sandstone are present. The Extension thins to the north and west. On Stuart Island and in the Cowichan River area, the Extension
Formation thins to less than 150 meters. Ward (1976) states that ap proximately 250 meters of Extension conglomerates and sandstone are pre sent at Booth Bay, along the northwestern margin of Saltspring Island.
In the Nanaimo River area, the Extension Formation generally ranges from
100 to 200 meters in thickness (Clapp, 1912a; Ward, 1978; Ward, pers. comm., 1977). Interbedded coal seams and associated siltstones are present at this locality.
The Pender Formation in the Nanaimo River area is composed of reddish-brown siltstone, dark grey mudstone and coal seams. In most of the Gulf Islands and in the Cowichan River area, however, the Pender
Formation ranges from featureless mudstone to sandstone-shale interbeds 28 with "classic" turbidite bedding. On South Pender and Waldron islands the Pender Formation consists of sandy fossiliferous siltstone.
The Protection Formation is composed of sandstone, conglomerate and rare siltstone. It is easily recognized in the Nanaimo River area. In a study of Nanaimo rocks in this area, Clapp (1912) stated that the dis tinctive light gray sandstone was "the best horizon marker in the
Nanaimo Group." In other portions of the Nanaimo Basin, however, Protec tion Formation is not as easily distinguished. In most areas in which this unit was examined, it consists of medium- to coarse-grained sand stone with lesser amounts of interbedded conglomerate. On Saturna and
Sucia islands, outcrops of the Protection Formation are characterized by distinctive quartz-phyllite conglomerates.
The Cedar District Formation is recognized in the Nanaimo River area, throughout the Gulf Islands, and on Sucia Island. At its type lo cality at Dodds Narrows, it consists of 308 meters of monotonous dark grey mudstone (Clapp, 1917). Most outcrops of the Cedar District Forma tion, however, consist of interbedded sandstone-siltstone, sandstone- shale, and siltstone-shale units exhibiting "classic" turbidite bedding.
Beds consisting of series of these units commonly intertongue with thick sandstone and mudstone. At Southey Point, much of the Cedar District
Formation is composed of sandstone. Thick sandstone interbeds are also present on South Pender Island and at Bedwell Harbor on North Pender
Island. The Cedar District is the thickest formation in the Nanaimo
Group. This formation is over 1200 meters thick on South Pender
Island. At most localities in the Gulf Islands, the Cedar District 29
Formation ranges from 200 to 400 meters in thickness. In the Nanaimo
River area, the lower portion of the Cedar District Formation consists
of approximately 200 meters (Ward, 1978) of "classic" turbidites
intertonguing with and overlain by undifferentiated mudstone of the
upper portion of the Cedar District Formation. The lithology of the
Cedar District Formation on Sucia Island contrasts greatly with that of
the Cedar District outcrops in the Gulf Islands. At this locality, the
Cedar District is comprised of sandy, fossiliferous siltstone, similar
to the Pender Formation on Waldron and South Pender islands.
The Decourcy Formation is very similar in lithology to the Protec
tion Formation, consisting of sandstone, with interbedded conglomerate
and rare siltstone, shale and coal. The Decourcy Formation is recog
nized in the Gulf Islands, the Nanaimo River area and on Sucia and Matia
islands of the San Juan Islands. The highest percentages of conglomer
ate in the Decourcy Formation occur in the southeast portion of the
Basin, in outcrops on Mayne, Saturna and Sucia islands. Conglomerate
intervals are common, however, in outcrops of the Decourcy Formation on
Saltspring and Thetis islands and along the east coast of Vancouver
Island in the Nanaimo River area. The Decourcy Formation is approxi
mately 600 meters thick at Dinner Bay on Mayne Island. Approximately
350 meters of the Decourcy Formation is present on Sucia Island. At
Booth Bay, along the northwest coast of Saltspring Island, the Decourcy
Formation is only 150 meters thick (Ward, 1976). However, this forma
tion is much thicker in the Nanaimo River area, where Clapp (1917)
estimated that the Decourcy Formation near Ladysmith Harbor is 30 approximately 425 meters thick.
The Northumberland Formation consists of thick mudstone intercalat ed with sandstone-shale andsiltstone-shale units exhibiting "classic" turbidite bedding. These beds are similar to "classic" turbidite bedding observed in the Haslam and Cedar District formations, except sand:shale ratios are generally much lower and sandstone and siltstone beds are thinner. Outcrops of the Northumberland Formation occur throughout the Gulf Islands. At Horton Bay, on Mayne Island, this formation is 350 meters thick. Stratigraphic sections of the
Northumberland measured by Hansen (1976) on Saltspring Island, Simmons
(1973) on Thetis and Kuper Islands and Clapp (1914) on Gabriola Island indicate that thickness of the Northumberland Formation varies greatly at different locations throughout the Nanaimo Basin.
The Geoffrey, Spray and Gabriola formations were not examined in detail. At Horton Bay, the Geoffrey is composed largely of sandstone and is 90 meters thick. The Spray Formation at this locality is domi nantly composed of mudstone, with some "classic" turbidite bedding.
Near Edith Point on Mayne Island, the Gabriola consists of sandstone with some interbedded conglomerate and is very similar to sandstone units discussed earlier. The stratigraphy of these formations is pre sented in greater detail by Muller and Jeletzky (1970).
Formations of the Nanaimo Group are often difficult to define.
Isolated outcrops on islands make it difficult to trace specific units and to prove that conglomerate, sandstone and shale beds are continuous mappable units rather than discontinuous lenses intercalated with each other. In most cases, formations of the Nanaimo Group cannot be identi fied from island to island on the basis of unique lithologic character istics. Paleontologic data is often necessary to determine strati graphic position of particular lithologic units. Formations are then mapped at particular localities based on this data. Where fossils are not present, the differentation of specific formations in the Nanaimo
Group is very difficult. SEDIMENT DISPERSAL DATA
Over 550 paleocurrent measurements were made from sedimentary structures in sandstones, conglomerates and siltstones of the Nanaimo
Group. Paleocurrent measurements were made on trough and planar medium- to large-scale (Conybeare & Crook, 1968) cross-beds, parting lineation
(figure 5) ripple marks and ripple cross-lamination and on sole marks
(figure 6), including tool, groove and flute casts (Figure 7). These paleocurrent directions are shown in Figure 8.
Most northern outcrops in the Nanaimo Basin are characterized by beds striking to the northwest and deformed by gently plunging folds.
In these areas, paleocurrent indicators were rotated about bedding. In the southeastern portion of the Nanaimo, however, the axial traces of folds in the basin bend around Early Mesozoic and Paleozoic rocks of the
San Juan Island terranes (table 5) which are in thrust-fault contact with Nanaimo rocks (figure 4). This curvature probably resulted either from a second episode of folding in the Nanaimo Basin, caused by northward movement of the San Juan Island assemblages, or as a result of these rocks acting as a buttress during original folding of Nanaimo strata (Vance, 1977).
The structural geology of Waldron Island presented special prob lems. Nanaimo rocks on Waldron Island can be divided into two blocks, exhibiting different structural orientations. These two blocks of
32 33
Figure Parting lineation in the Extension Formation at Cusheon Creek, Saltspring Island. 34 Figure 6. Groove casts in the Cedar District Formation at Bedwell Harbor, North Pender Island.
Figure 7. Giant flute casts in the Extension Formation on the southeast coast of Barnes Island. I Figure 8. Palescurrent measurements in the Nanaimo Basin. Pie-shaped wedges refer to 95% confidence interval determined by T distributions on measurements. VANCOUVER ISLAND
ENVIRONMENT ^ ---- Continental, Marginal M arine
>3g Mixed
Submarine-fan SAN JUAN ^ ISLANDS
12 18 km. 39
Nanaimo strata are separated by a fault which cuts across the central portion of the island (figure 9). Nanaimo rocks at Point Hammond,
Fishery Point and northeastern Mail Bay trend northwest, parallel to folds in Nanaimo rocks in the Gulf Islands. Nanaimo strata on this por tion of Waldron Island are part of a northwest plunging anticline which can be traced to Skipjack Island. The axial traces of folded Nanaimo rocks in the southeastern portion of the island, from Disney Point to the southwestern end of Mail Bay, curve around Orcas Island and trend northeast. In figure 8 the curvature of these axial traces was palin- spastically straightened. Island outcrops and paleocurrent directions in the southeastern portion of the basin have been rotated such that axial traces of folds in these rocks are concordant with those of folds in the remainder of the Nanaimo Basin. This includes the southeastern portion of Waldron Island. The northern portion, however, was left in place. As a result, Waldron Island appears in figure 8 as two separate blocks.
Restored positions of island outcrops in figure 8 are highly spec ulative. Folding and faulting within and between islands were not ac counted for. Additionally, relatively little is known about the magni tude and nature of faulting in the southeastern portion of the Nanaimo
Basin, and delineation of the precise Late Cretaceous positions of these outcrops is not possible with available data.
Structural correction of paleocurrent directions allows true sediment-dispersal directions to be approximated for development of the
Nanaimo Basin in the Late Cretaceous. In the Nanaimo River area, three 40
Figure 9. Structural geology of Waldron Island. 71_ c^> Skipjack
.46 Point Hammond Fishery Point
9 ^ . 40
» Mail Bay 42 discrete paleocurrent orientations are recognized. The Extension,
Protection and Cedar District formations exhibit eastward sediment- dispersal directions in outcrops along the Nanaimo River and near the town of Nanaimo. Western directions and rare southeastern directions were measured in the Extension and Protection formations on Newcastle
Island. Southeastern directions are also recognized in the Decourcy
Formation at Yellow Point (figure 8).
Southeastward directions were also measured in the Decourcy Forma tion on Sucia and Matia islands, the Extension Formation on Skipjack Is land, the Pender and part of the Extension formations on Waldron Island and the Geoffrey? or Gabriola? Formation on Patos Island. Western di rections have been measured in portions of the Extension Formation on
Waldron Island and in the Haslam and Extension formations on Flattop Is land. Sediment-dispersal directions in the Haslam and Extension forma tions on Orcas, Clark and Barnes islands trend southwest, whereas direc tions in the same units on Stuart Island trend northwest.
Hansen (1976) noted that sediment-dispersal directions in the Comox
Formation on Saltspring Island are arranged in a radial pattern sur rounding an uplifted block of Sicker Group volcanics and Tyee Intru- sives.
Paleocurrents in the Cowichan River area, the Saanich Peninsula area and in the Gulf Islands exhibit two discrete orientations.
Directions in the southern portion of the Nanaimo Basin, including the
Cowichan River area, are dominantly west to southwest, whereas directions in the northeastern portion of the basin are northwest. The 43
divergence in paleocurrent directions occurs around the uplifted block of Sicker Group volcanics and sediments, and Tyee Intrusives on
Saltspring Island. PETROGRAPHY
Sandstones and conglomerates in the Nanaimo Basin show strati- graphic and geographic distribution of detrital constituents that can be grouped into distinct populations or petrofacies (Dickinson & Rich,
1972). Distribution of these petrofacies provides important information concerning the depositional and tectonic history of the Nanaimo Basin and upland areas supplying detritus to the basin. Petrofacies in the
Nanaimo Basin can be correlated with specific source areas in these uplands. These petrofacies can then be used in combination witb paleon- tologic data to determine time and geographic extent of sediment supply into the basin from specific source areas.
Petrographic Methods
One hundred fifty two thin sections of medium- to fine-grained sandstones were point counted to determine modal composition of detrital and authigenic minerals (Appendix I). Three hundred points per thin section were counted on a rectangular grid developed with a mechanical stage. Spacing between points was set so that it was larger than the maximum grain size in the thin section and so that maximum area of the thin section could be covered. Thin sections were cut normal to bedding.
In order to insure consistency in the point counting procedure, detrital constituents were classified in terms of nested categories of
44 45 grains and conventions were developed for identification of detrital grains in sandstones of the Nanaimo Basin. These categories are dis cussed below.
Quartz-types; Quartz-types are apportioned into five categories, based on grain properties. All sand-sized, monocrystalline quartz was put into a single category. Most quartz in Nanaimo rocks is equant to sub- equant with abraded grain boundaries and moderate amounts of vacoules and microlites. Some inclusion-free monocrystalline quartz with euhe- dral boundaries and well-developed embayments is present in Nanaimo sam ples. Folk (1968) states that this type of quartz grain is derived from volcanic rocks. However, abrasion along grain boundaries in Nanaimo rocks makes consistent identification of this type of quartz very diffi cult and it was not counted as a separate category. Both undulatory and non-undulatory monocrystalline quartz are common in Nanaimo rocks. How ever, monocrystalline quartz was not separated into these two catego ries. Both undulatory and non-undulatory quartz can be derived from metamorphic, sedimentary and plutonic source rocks (Basu and others,
1975). Since the Nanaimo Basin was surrounded by and received sediment from a diverse suite of metamorphic sedimentary and igneous rocks, the ratio of undulatory to non-undulatory quartz provides little information concerning specific source terranes.
Polycrystalline quartz was separated into four categories. Grains with equant, irregularly bounded crystal units, in which crystal units are very fine-grained sand-size or larger, were counted as simple polycrystalline quartz. Grains with equant, irregularly bounded crystal units smaller than very fine-grained sand, were counted as chert.
Polycrystalline quartz grains with abundant micaceous microlites, well 46
developed polygonal boundaries, or highly undulose stretched crystal units were counted as metamorphic rock fragments. Sandstone fragments were also separated and counted as sedimentary rock fragments.
Feldspar types: Thin-sections were stained with sodium colbaltinitrite
to discriminate potassium feldspar from quartz and plagioclase. Most potassium feldspar present is orthoclase. Microcline is very rare.
Sanidine is rare as well although local concentrations up to four per
cent of the total detrital constituents are observed in some samples.
Plagioclase was separated from potassium feldspar by the lack of sodium cobaltinitrite stain and by generally pervasive zeolite (laumon-
tite) and seracite alteration. Approximately 55 percent of plagioclase in the Nanaimo Basin is untwinned. The calcium:sodium ratio in unalter ed grains is in the andesine range, which is consistent with values ob tained for plagioclase in the Coastal Plutonic Belt (Roddick, 1965;
Roddick and others, 1977), some plutonic rocks of the North Cascades
(Misch, 1966, 1977), and the Jurassic Island Intrusions (Carson, 1973).
However, much of the plagioclase is albitized and original calcium: sodium ratios cannot be determined. Approximately one to two percent of plagioclase in the Nanaimo Group exhibits oscillatory zoning.
Lithic Fragments: Volcanic rock-fragments were separated into basaltic
(figure 25), basaltic to andesitic (figure 24), andesitic, andesitic to dacitic, dacitic, tuffaceous and unknown volcanic categories. These categories are based on textural and mineralogic criteria discussed by
Dickinson (1970) and Williams and others (1954). Basaltic rock- fragments generally exhibit intersertal, intragranular and glomero- porphy-ritic textures whereas andesite rock-fragments commonly exhibit pilotaxitic and trachyitic textures. Dacite rock-fragments are often 47 pilotaxitic and are characterized by a groundmass made up of an anhedral microcrystalline mosaic of quartz and feldspar grains. Tuffaceous rock-fragments exhibit relict pyroclastic textures and occasionally contain devitrified glass shards.
Transitional divisions between major rock-types allow assignment of a particular grain to an approximate category when a precise identi fication cannot be made due to alteration and/or lack of diagnostic fea tures. In some cases, fragments were identified as volcanic but alter ation prevented any further discrimination. These fragments were counted as unknown volcanic rock-fragments.
Most metamorphic rock-fragments are phyllite (figure 22) or schist.
Individual metamorphic rock-types were counted during modal analysis so they could be correlated with specific source areas; however, they were summed and compiled as a single variable. In many cases, fragment size was too small to conclusively identify the metamorphic rock-type. Addi tionally, it is difficult to set up reproducible criteria for discrimi nation of schistose and phyllitic fragments in the Nanaimo Group.
Gneissose fragments are rare in the Nanaimo Group. Gneissic rocks are present in the Coastal Plutonic Complex, the North Cascades and on
Vancouver Island, and these rocks probably contributed detritus into the
Nanaimo Basin. Much of this detritus, however, was probably broken into individual mineral grains by erosional processes. Other grains from gneissic source rocks may have been counted as plutonic rock-fragments.
Plutonic rock-fragments in the Nanaimo Basin range from quartz diorite to granodiorite. In contrast to Dickinson (1970), plutonic rock-fragments were assigned to a separate category. Dickinson (1970) assigns plutonic rock-fragments to mineral categories based on the 48 particular mineral grain of the fragment that is situated under the cross-hairs. This practice could result in loss of data concerning provenance in rocks of the Nanaimo Basin.
Sedimentary rock-fragments were counted as a single variable be cause 97 percent of these rock-fragments in Nanaimo rocks are composed of clay- to silt-sized material. Extensive recrystallization makes car bonate fragments extremely difficult to identify except in rare in stances in which they contain bioclastic material. Additionally, sand stone source rocks probably contributed sediment into the Nanaimo Basin largely as individual mineral grains rather than rock-fragments.
Separation of argillaceous rock-fragments and highly altered volcanic rock-fragments was very difficult in some cases. These rock-fragments were considered to be volcanic if euhedral or nearly euhedral feldspar laths were present and sedimentary if these laths were absent. Some fragments were so highly altered that they could not be classed in a particular category of lithic fragments. These were categorized as un known rock-fragments.
Heavy Minerals: Heavy minerals in the Nanaimo Group, in order of de creasing abundance, are: biotite, muscovite, epidote, opaque minerals
(hematite, magnetite, illmenite), amphibole, sphene, garnet, zircon and apatite. Sphene, garnet, zircon and apatite are present only in trace amounts, and the first four heavy minerals listed are the only ones present in Nanaimo rocks in significant percentages (Appendix I). Some of the opaque minerals are probably secondary and do not represent original detrital input. It is difficult in many cases to distinguish between some detrital and authigenic opaque minerals in Nanaimo rocks. 49
Chlorite occurs as detrital grains, an alteration product of detri tal minerals and rock fragments, and as cementprecipitated in pore space. Clearly identifiable detrital chlorite is uncommon in Nanaimo rocks, however, and most chlorite is of secondary origin.
In some cases, identification of particular heavy minerals was not possible due to severe alteration. These minerals were assigned to the unknown mineral category.
Interstitial Components: Interstitial components of Nanaimo sandstones include calcite, phyllosilicate, chlorite, zeolite, inhomogenous matrix and rare silica and potassium feldspar cements. Many detrital grains of these rocks show extensive replacement by these constituents. However, since the objective of this study is to determine original detrital com positions rather than examine diagnetic history, identifiable altered grains were classified as detrital constituents. Although many grains exhibited extensive alteration, replacement minerals of altered grains were counted only when original grain boundaries and textures were com pletely destroyed.
Inhomogenous matrix and authigenic chlorite are the two most common interstitial constituents in Nanaimo sandstones. The inhomogenous matrix consists of a mixture of authigenic chlorite, iron oxide minerals, and both authigenic and detrital clayey lutum. A gradation exists between this inhomogenous matrix and pure authigenic chlorite, which is generally trans parent and exhibits a lack of minute detritus and/or murky impurities.
Therefore, only chlorite that was free or nearly free of impurities was counted as chlorite. The remainder was counted as inhomogenous matrix. It was not possible to consistently separate protomatrix, orthomatrix and epimatrix components discussed by Dickinson (1970). 50
Diagenesis
The detrital constituents of sandstones can be greatly modified by diagenetic alteration. Therefore, it is important to determine the ex tent and nature of diagensis so that an accurate determination can be made of the original detrital modes of sediment deposited into the
Nanaimo Basin. Two stages of diagenesis in sandstones of the Nanaimo
Basin can be recognized based on textural features and alteration pro ducts.
Some sandstones of the Nanaimo Basin exhibit extensive cementation by calcite. In these sandstones, little evidence of compaction is ob served. Long, concavo-convex and sutured contacts are rare in contrast to sandstones not extensively cemented by calcite. Tangential contacts predominate and large intragranular areas are present. Calcite cement occurs in sandstones of widely varying grain_size and composition.
Additionally, large local variations in the percentage of calcite cement occur at some locations. Calcite concentration decreases from seventeen percent to zero percent in the Decourcy Formation on Sucia Island, within a sixteen meter interval.
Replacement of amphibole and biotite by chlorite is common in sandstones of the Nanaimo Group (figure 11). Chlorite pseudomorphs after pyroxene may also be indicated by chlorite grains exhibiting a euhedral blocky outline. In addition, some unstable lithic fragments, especially basic volcanic rock-fragments, exhibit extensive alteration to chlorite and inhomogenous matrix. The percentage of chlorite and inhomogenous matrix is roughly proportional to the percentage of heavy minerals and unstable lithic fragments. Secondary hematite and rare leucoxene are recognized in Nanaimo sandstones and are generally Figure 10. Microphotograph of calcite-cemented sandstone containing euhedral crystals of laumontite.
Figure 11. Microphotograph showing alteration of ampnibole grains (A) to chlorite (ch) and inhomogenous matrix (epi). Secondary opaque minerals in upper right-hand corner (op). 52 53 associated with authigenic chlorite and inhomogenous matrix. These opaque minerals commonly replace biotite, amphibole and unstable
ferromagnesian minerals in lithic fragments.
Phyllosilicate pore-filling cements other than chlorite and phyllo- silicate rims surrounding detrital grains are also recognized in Nanaimo sandstones. Phyllosilicate cements are separated from inhomogenous matrix by the absence of impurities and, in some cases, by well develop ed crystallinity. Along some clay rims, a radial arrangement of crystal platelets is observed. Clay rims, phyllosilicate cement and clay miner als present in the inhomogenous matrix probably developed by chemical alteration of both ferromagnesian minerals and plagioclase. Many pla gioclase grains exhibit some replacement by illite. This illite is associated with surrounding clay rims and probably developed during the diagenetic history of the sandstone.
Authigenic zeolite is present in sandstones of the Nanaimo Group and is most common in sandstones with a high percentage of plagioclase and relatively small percentage of lithic fragments (Appendix I). Most zeolite in Nanaimo sandstones is laumontite, although Stewart and Page
(1972) have recognized heulandite in these sandstones as well.
Zeolite occurs as replacement of plagioclase (figure 12), pore-filling cement (figure 13) and as euhedral crystals (figure 10). The percentage of pore-filling zeolite cement in Nanaimo sandstones is less than three percent. Most zeolite occurs as an alteration product within plagioclase grains. Plagioclase in most Nanaimo sandstones is albitized and contains extensive intergrowths of authigenic laumontite (figure
12). Albitization of plagioclase results in release of calcium which is 54
Figure 12. Microphotograph of thin-sections showing replacement of plagioclase by zeolite.
Figure 13. Microphotograph of thin-section showing zeolite (laumontite) pore-filling cement. 55 56 consumed in the formation of both laumontite and heulandite (Stewart and
Page, 1972).
Rare silica cement and potassium feldspar cement are also present in Nanaimo sandstones. Development of long, concavo-convex and sutured contacts in samples in which these cements are present suggests that they may have been formed by pressure solution.
Textural features suggest that chlorite, inhomogenous matrix, phyl losilicate cement, authigenic zeolites, authigenic potassium feldspar and silica cement may have formed at greater burial depths than most of the calcite cement in Nanaimo sandstones. Long, concavo-convex, and sutured grain contacts are far less common in sandstones extensively cemented by calcite. Some grains in sandstones not cemented by calcite show micro-fractures and micro-faults (figure 12) that probably resulted from brittle deformation of grains during compaction. In addition, pyroxene and basic volcanic rock-fragments may have been significantly reduced by diagenetic alteration. Although amphibole and pyroxene are common in many source terranes surrounding the Nanaimo Basin, amphibole is relatively rare in Nanaimo sandstones and pyroxene is absent. Most amphibole in Nanaimo rocks shows extensive alteration to chlorite, inhomogenous matrix and iron oxides. Additionally, blocky euhedral pseudomorphs suggest replacement of pyroxene by chlorite. Basaltic rock-fragments in many Nanaimo sandstones are highly altered. Many of the unknown volcanic rock-fragments are probably basaltic. The percentage of basic volcanic rock-fragments in Nanaimo sandstones is roughly proportional to the percentages of unknown volcanic rock-fragments and inhomogenous matrix. 57
Petrofacies
Nanaimo sandstones are divided into five petrofacies based on detrital modes and the ratios of grain types present in medium- to coarsegrained sandstones. Each petrofacies contains a unique assemblage of rock-fragments and minerals which can be related to specific source terranes. Although 24 detrital components were counted in Nanaimo sandstones (Appendix I), petrofacies are defined by 12 parameters based on the 24 components. These parameters are (1) monocrystalline quartz and simple polycrystalline quartz (crystal units larger than very fine-grained sand), (2) chert (polycrystalline quartz with crystal units smaller than very fine-grained sand), (3) plagioclase, (4) potassium feldspar, (5) basic volcanic rock-fragments, (6) intermediate and acidic volcanic rock-fragments, (7) plutonic rock-fragments, (8) metamorphic rock-fragments (excluding metavolcanics), (9) sedimentary rock-fragments, (10) heavy minerals, (11) ratio of epidote/(epidote + biotite), and (12) ratio of plagioclase/total feldspar (P/F ratio)
(Appendix II).
The relative percentages of quartz, feldspar and lithic-fragments of samples of each petrofacies can be delineated on a QFL diagram. The quartz pole in this diagram represents the percentage of monocrystalline quartz plus simple polycrystalline quartz. The feldspar pole represents the sum of plagioclase and potassium feldspar grains. The lithic pole represents the sum of chert, volcanic rock-fragments, metamorphic rock-fragments, and sedimentary rock-fragments. Plutonic rock-fragments are not included in construction of these diagrams. In rocks of the
Nanaimo Group, high percentages of quartz and feldspar commonly indicate a plutonic source, whereas high percentages of rock-fragments and chert 58
suggest derivation from metamorphic, sedimentary and volcanic terranes.
Including plutonic rock-fragments at the lithic pole would tend to
obfuscate this relationship and superimpose compositionally distinct
petrofacies on QFL plots. Inclusion of plutonic rock-fragments at
either the quartz or feldspar pole would make it impossible to derive
information based on the relative percentages of quartz and feldspar in
each sample.
Sums of percentages for each grain type were recalculated to 100
percent and plotted on a QFL diagram for samples in each petrofacies
(figure 14). The name given to each petrofacies is based on the
presence of particular diagnostic minerals and total sandstone
composition. These petrofacies are as follows: (1) high-plagioclase
arkose //I and high-plagioclase arkose #2, (2) chert-rich lithic arenite,
(3) lithic arkose, (4) dacite-rich arkose, and (5) basalt-bearing lithic
arenite. Compositional plots have also been constructed which aid in
discrimination of petrofacies. In figure 15, mean values for the ratio
between volcanic, metamorphic and sedimentary (including chert)
rock-fragments have been plotted for each petrofacies. Mean values for
these ratios exhibit large variances in some petrofacies because of the
relatively small percentage of total rock-fragments present in each
sample. This variation is shown by error bars for each petrofacies which represent 95 percent confidence limits of these values. The
ratio of plagioclase/total feldspar is also plotted for each petrofacies
(figure 16). In these plots, error bars illustrating standard deviation
are shown for each petrofacies.
Statistics
Q-mode factor analysis was performed on the detrital compositions Figure 14. QFL diagram of petrofacies of the Nanaimo Group □ = high-plagioclase arkose #1 © = high-plagioclase arkose #2 # = chert-rich lithic arenite o= lithic arkose ★ = dacite-rich arkose ■ = basalt-bearing lithic arenite 6 0
Q 61
Figure 15. Relative percentages of volcanic, sedimentary and metamorphic rock-fragments in each petrofacies. Mean values are shown. Error bars represent 95% confidence levels determined by T distributions for each component of each petrofacies. Symbols for each petrofacies are the same as in figure 14. • • OCT" Mil Ml hr-ih ihc Aranlta Lithic Chart-rich VRF Bal-arn Lithic Aranlta Baaalt-baarlng H Daclta-rlch Arkoit Arkoit Daclta-rlch ihc Arkott Lithic MRF 62 63
Figure 16. Plagxocidt,a/toKal. ieldspar ratios for each petrofacies. Diagonally-lined areas represent standard deviations for each mean value. P/F RATIO
^716678313 HIGH-PLAGIOCLASE ARKOSE 1
HIGH-PLAGIOCLASE ARKOSE 2
CHERT-RICH LITHIC ARENITE
LITHIC ARKOSE
d a c it e - rich ARKOSE
BASALT-BEARING LITHIC ARENITE
.20 .40 .60 .80 1.00 65
of sandstones of the Nanaimo Basin to test the validity of the petro
facies and to evaluate the extent of mixing of sediment which makes up
Nanaimo sandstones from several different source areas. Three para meters were excluded from the analysis: the P/F ratio, the heavy mineral parameter, and the epidote/(epidote + biotite) ratio. These
parameters are important in discriminating between sub-populations
within the total sample suite but tend to confuse relationships between
petrofacies. In many cases, variations in the total heavy mineral
percentage and the epidote/(epidote + biotite) ratio probably resulted
from hydraulic processes and have little bearing on provenance. In
addition, the P/F parameter is already expressed by the inclusion of the
plagioclase and potassium feldspar parameters.
In Q-mode factor analysis, samples are assumed to represent mix
tures of "idealized” end-member compositions. A matrix is constructed
in which interrelationships between samples are examined in terms of
their variables. Factors which represent the "idealized" end-member
compositions are then extracted from this matrix. These factors are
vectors which are weighted proportionally to the amount of variance they
account for within the total sample suite. Elements of this vector which correspond to each sample are called factor loadings. Factors can
be interpreted by comparing values of the factor loadings with the com
position of each sample. Samples which exhibit high factor loadings for
a particular factor have compositions which closely resemble the
"idealized" end-member composition predicted by that factor. Q-mode
factor analysis is discussed in detail by Davis (1973) and Joreskog and
others (1976). 66
Six factors were extracted from petrographic data in the Nanaimo
Basin. Factors were then rotated by the Kaiser Varimax Method (Davis,
1973) to aid in interpretation. These six factors account for 97 per
cent of the variance in petrographic data from the Nanaimo Basin. The
first four factors, which account for 88 percent of the total variance,
predict idealized end-member compositions, which can be correlated with
source terranes surrounding the Nanaimo Basin. Mean factor loadings for
each petrofacies are listed in table 7. Factor loadings for all samples
in the Nanaimo Basin are listed in Appendix III. As successive factors
are extracted, they account for progressively less and less of the total
variance of the sample population. Therefore, the similarity between a
particular sample and the end-member composition predicted by a factor
is represented by a progressively smaller and smaller factor loading as
successive factors are developed.
The first factor extracted accounts for 44.9 percent of the variance
in samples of the Nanaimo Basin. This factor predicts an idealized end-
member composition or source area that is high in quartz, plagioclase and
potassium feldspar. The second factor, which accounts for 16.6 percent of
sample variance predicts an end-member composition dominated by chert. The
third factor is controlled largely by the presence or absence of inter
mediate to acidic volcanic rock-fragments and accounts for 25.9 percent of
the variance. The fourth factor, which accounts for 11 percent of the
total variance, is dependent largely on the percentage of basic volcanic
rock-fragments (Appendix III).
High-Plagioclase Arkose Petrofacies
Rocks of this petrofacies have been divided into two subpetrofacies 67 based on paleocurrent data: the high-plagioclase #1 petrofacies and the high-plagioclase #2 petrofacies. Paleocurrents in the Nanaimo Basin suggest that high-plagioclase arkoses were derived from two distinct source terranes— the Coastal Plutonic Belt and the Jurassic Island
Intrusions on Vancouver Island.
High-Plagioclase Arkose #1 Subpetrofacies: Rocks of this subpetrofacies are characterized by abundant quartz (mean 38%) and plagioclase (mean
31%) and a P/F ratio of approximately 0.75 (figure 16). This is one of the lowest P/F ratios present in petrofacies of the Nanaimo sandstones.
This subpetrofacies also contains small amounts of epidote as compared to biotite. The epidote/(epidote + biotite) ratio is 0.17, which is very low compared to mean values of other Nanaimo petrofacies. Heavy minerals average 9.2 percent and these rocks also contain a relatively low percentage of lithic fragments (mean 11%). Most of these lithic fragments are argillites, andesites, and dacites (figure 15).
The high-plagioclase arkose //I subpetrof acies occurs on Mayne
Island in the Cedar District to Geoffrey formations on Saturna Island, in the Cedar District to Decourcy formations, on North Pender Island in the Extension to Geoffrey formations, on South Pender Island in the
Pender to Cedar District formations, and on Saltspring Island in the
Pender to Decourcy formations (figure 18). In addition, sandstone compositional data reported by Carter (1977) suggest that this subpetrofacies is also present in the Geoffrey and Gabriola formations on Galiano Island.
The oldest occurrences of this sub-petrof acies are rocks of I_. schmidti Zone time at Cusheon Creek on Saltspring Island and in rocks of the I. schmidti-B. chicoensis Barren Interzone on North Pender Island. Figure 17. Photomicrograph of thin-section of high-plagioclase arkose #1 from the Decourcy Formation at Dinner Bay, Mayne Island.
70
Figure 18. Petrofa.:ies distribution in the Nanaimo Basin. Mean values for each petrofacies are shown in QFL diagrams at each locality. □ H1GH-PLAG10CLASE ARKOSE 1 ©HIGH-PLAGIOCLASE ARKOSE 2 e CHERT-RICH LITHIC ARENITE O MIXED LITHIC ARENITE/ARKOSE 1 * DACITE-RICH ARKOSE BASALT-RICH LITHIC ARENITE
o
CANADA U.S.A.
1 8 km . 72
On South Pender Island, this sub-petrofacies first occurs in JS. chicoensis Zone time rocks and on Saturna Island in rocks of B. rex
Zonule time. The high-plagioclase arkose #1 sub-petrofacies dominates rocks of the southern Gulf Island in the upper faunal zones. It extends into P. suciaensis Zone time at all localities on Mayne, Saltspring,
Saturna, North Pender, and South Pender islands.
Very high factor loadings for factor //I in 0-mode analysis occur in the high-plagioclase arkose #1 sub-petrofacies (mean value .80547) whereas factor loadings for other factors are relatively low (Table 7).
This suggests that the rocks of the high-plagioclase arkose //I sub-petrofacies closely resemble the high quartz, plagioclase and potassium feldspar compositional end-member predicted by this factor.
Depositional geometry of this sub-petrofacies, petrology, and paleocurrent measurements to the west and northwest suggest that the high-plagioclase #1 petrofacies was derived from rocks of the Coastal
Plutonic Belt. The Coastal Plutonic Belt is dominantly composed of quartz diorites and granodiorites. The P/F ratio of the high-plagio clase arkose //I is very similar to P/F ratios in rocks of the Coastal
Plutonic Belt (Roddick, 1965). Lithic components may have been derived from mixing of detritus from other source areas or from other rocks such as the Gambier Group in the Coastal Plutonic Complex.
High-Plagioclase Arkose #2 Sub-Petrofacies: The high-plagioclase arkose
#2 sub-petrofacies is compositionally very similar to the high-plagio clase arkose #1 (Appendix II) in mean percentages of quartz, plagio clase, and potassium feldspar. This sub-petrofacies exhibits a slightly smaller mean percentage of lithic fragments (7.6% versus 11% for the high-plagioclase arkose #1). The most common heavy mineral in this sub- 73 petrofacies is biotite and the epidote/(epidote + biotite) ratio is
lower than those of other petrofacies.
The high-plagioclase arkose #2 subpetrofacies is recognized in
rocks of the Extension to Decourcy formations in the Nanaimo River area
(Figure 18). It ranges from the I_. schmidti~B. chicoensis Zone time
interval through the H_. vancouverense-P. suciaensis Barren Interzone.
The high-plagioclase arkose #2 subpetrofacies shows factor loadings for factor one (mean value .85643) that are similar to those reported for the high-plagioclase arkose #1 (Appendix III). These values are within one standard deviation of one another. Slightly higher factor loadings for factor one probably reflect smaller quantities of lithic components. Factor loadings for factors 2-6 are very low because of the small amounts of lithic fragments and chert. These low factor loadings indicate that the observed composition of these samples is very close to the end-member composition predicted by factor 1.
The Nanaimo River area is bordered by the Nanaimo River Batholith and the Ladysmith Pluton (Carson, 1973). These Middle Jurassic horn blende and biotite granodiorite plutons probably supplied much of the detritus to sandstones of the high-plagioclase arkose #2 subpetro- facies. P/F ratios measured by Carson (1973) for rocks of the Nanaimo
River Batholith are very similar to those in the high-plagioclase arkose
It 2 subpetrof acies.
Chert-Rich Lithic Arenite Petrofacies
Rocks of the chert-rich lithic arenite petrofacies contrast greatly with rocks of both high-plagioclase arkose petrofacies (figures 14, 15, and 16). This petrofacies is dominated by a high percentage of chert Figure 19. Photomicrograph of chert-rich lithic arenite from the Haslam Formation in the Cowichan River area. 75 76
(mean; 25 percent). Some samples contain up to 58 percent chert (figure
19). Lithic fragments are far more common in this petrofacies than in the high-plagioclase arkose (Appendix II). Chert-rich lithic arenites contain an average of 7.3 percent sedimentary rock-fragraents, 6 percent intermediate and acidic volcanic rock-fragments, 2 percent basaltic volcanic rock-fragments, and 3.4 phyllite to schist rock-fragments. The mean percentage of quartz is 27 percent and plagioclase averages 18 percent. The average percentage of potassium feldspar is only 2 percent, and the mean P/F ratio is 0.90 (figure 16). The mean value for the epidote/(epidote + biotite) ratio is 40.7 (Appendix II), although a high standard deviation exists for this value.
Chert-rich lithic arenites are present on Clark and Saltspring islands in the Extension Formation, on Barnes and Orcas islands in the
Extension and Haslam formations, on South Pender Island in the Haslam to
Pender formations and on Saturna Island in the Protection Formation.
This petrofacies is also recognized in the Cowichan River area in the
Haslam to Extension formations (Figure 18).
This petrofacies is present only in the southern portion of the
Nanaimo Basin. The northernmost occurrence of chert-rich lithic arenites is at Cusheon Creek along the southeastern margin of Saltspring
Island. Most outcrops of the petrofacies occur in _B. elongatum or I_. schmidti Zone strata. The petrofacies extends into the B. chicoensis
Zone time on Waldron and South Pender islands. The youngest occurrence of this petrofacies outcrops in M. pacificum Zone strata on Saturna
Island.Chert-rich lithic arenites have high Q-mode factor loadings for factor #2 (mean value 0.65141) which is dominated by chert percentage and moderate factor loadings on factor 3 and factor 4, indicating some 77 detrital input from dacitic and basaltic sources. Low factor loadings for factor 1 suggest that there was relatively little input of detritus from plutonic sources (Appendix III).
Two subpopulations within this petrofacies are defined by the chert percentage, the epidote/Cepidote + biotite) ratio, and paleo- current measurements. Rocks of this petrofacies from Orcas, Clark and
Barnes islands exhibit a mean epidote/Cepidote + biotite) ratio of 65.3 and average 17 percent chert, whereas rocks from localities west and northwest of Orcas Island exhibit a mean value for the epidote/Cepidote
+ biotite) ratio of 34.6 and average 28 percent chert. Rocks on Barnes,
Clark and Orcas islands also contain a higher percentage of andesite, basalt, dacite, phyllite and argillaceous rock-fragments. These sub populations may represent rocks characterized by deposition from two separate source areas: the San Juan Islands and the North Cascades.
Paleocurrent measurements to the west suggest that the most likely source for chert detritus in chert-rich lithic arenites deposited to the west of Orcas Island are Paleozoic and Early Mesozoic rocks of the San
Juan Islands (Table 5).
Deposits of bedded chert are present in the Lopez terrane on Lopez,
Blakely, Cypress, Guemes and Fidalgo islands and in the Sinclair terrane
on Sinclair and Lummi islands. The major sources, however, were prob ably the Eagle Cove and Roche Harbor terranes which outcrop on western
Orcas Island and western and northwestern San Juan Island. These
terranes contain abundant chert (Whetten and Cowan, 1977; Whetten et al., 1978). Chert deposits in these terranes have been collectively
called the Orcas Formation by Vance (1975, 1977). Sedimentary and volcanic rock-fragments in chert-rich lithic arenites deposited west of 78
Orcas Island may have been derived from the San Juan Island terranes as
well, since argillaceous and volcanic rocks are dominant rock-types on
most San Juan Island terranes.
Paleocurrents on Orcas, Clark and Barnes islands suggest sediment
transport to the south and southwest, towards positions that these ter
ranes of the San Juan Islands probably occupied during the Late Creta
ceous (Johnson, oral comm., 1978; figure 8). If terranes of the San
Juan Islands acted as a major source for detritus on these islands,north
and northeast paleocurrents should be observed. Chert-rich lithic
arenites on Clark, Barnes and Orcas islands probably represent deposi
tion from source areas largely in the North Cascades. The Shuksan
Greenschist, the Chilliwack Group, the Nooksack Group, the Wells Creek
Volcanics and the Cultus Formation all contain rocks that are similar in
character to lithic fragments present in chert-rich lithic arenites on
Orcas, Clark and Barnes islands. Some or all of these rocks of the
North Cascades could have contributed detritus into the Nanaimo Basin.
The high P/F ratio observed in chert-rich lithic arenites throughout the
basin may also indicate some derivation of detritus from plutonic rocks
of the western North Cascades, which contain relatively small amounts of
potassium feldspar (Misch, 1977).
Lithic Arkose Petrofacies
Rocks of the lithic arkose petrofacies (figure 20) occupy a compo
sitional range on the QFL diagram between the chert-rich lithic arenites and high-plagioclase arkoses. Mean values for quartz content (34.2 per
cent) and plagioclase content (24.3 percent) are higher than mean
percentages of these grains in the chert-rich lithic arenites and lower Figure 20. Photomicrograph of thin-section of a lithic arkose from the Decourcy Formation on Sucia Island. 80 81
than those of the high-plagioclase arkoses. Potassium feldspar averages
5.4 percent and the P/F ratio is 0.81. Average chert percentage (6.3
percent) is much lower than values observed for chert-rich lithic
arenites. The mean percentages of intermediate to acidic volcanic and
metamorphic rock-fragments are higher than those recorded for chert-rich
lithic arenites, although they are within one standard deviation of one
another. Lithic fragments are far more abundant in the petrofacies than
in the high-plagioclase arkose. Mean epidote/(epidote + biotite) ratio,
although subject to a very high standard deviation, is higher than that
recorded for the chert-rich lithic arenite petrofacies and significantly
higher than the mean value recorded for rocks of the high-plagioclase
arkoses.
The lithic arkose petrofacies is present in rocks on Sucia Island
in the Protection, Cedar District and Decourcy formations on Matia
Island in the Decourcy Formation, on Patos Island in the Geoffrey? or
Gabriola? Formation and on Saturna Island in the Protection and Cedar
District formations (figure 18). This petrofacies is present in 11.
vancouverense Zone to _H. vancouverense-P. suciaenses Barren Interzone
rocks on Sucia Island and in B. rex Zonule rocks on Saturna Island. It
is present in 11. vancouverense-P. suciaensis Barren Interzone rocks on
Matia Island and in JP. suciaensis Zone rocks on Patos Island.
Factor loadings in the lithic arkose petrofacies indicate deposi
tion of sediment from several sources. Moderate factor loadings are
noted for all four major factors. These factor loadings suggest that
this petrofacies represents a mixture of several end-member composi
tions, which indicates deposition of sediment from several sources.
Factor 3, which is controlled largely by the percentage of intermediate 82 to acidic volcanics, is surprisingly high relative to factor 2 which reflects chert percentage. Mean percentages of plagioclase, quartz, and potassium feldspar that are between those of the high-plagioclase arkose petrofacies and those recorded for the chert-rich lithic arenites suggest some derivation of plutonic detritus from the Coastal Plutonic
Belt. Some chert and volcanic rock-fragments may have been derived from source rocks in terranes of the San Juan Islands. Chert clasts from the
Decourcy Formation on Sucia Island contain Triassic radiolaria, which are identical to radiolaria recovered from Triassic cherts of the Eagle
Cove and Roche Harbor terranes (Jones, as quoted by Johnson, 1978).
Additionally, some clasts from conglomerates of the Decourcy Formation on Sucia Island are lithologically indistinguishable from rocks of the
Constitution Terrane. Andesitic and tuffaceous rock-fragments are identical in texture to some volcanic rocks of the Constitution Terrane on Orcas Island.
Compositional data from rocks of the lithic arkose petrofacies also indicate that some detritus may have been derived from source rocks in the North Cascades. The Protection Formation on Saturna and Sucia islands is partially composed of quartz-phyllite conglomerate.
Graphitic phyllite clasts resemble the Paleozoic Darrington Phyllite of the North Cascades. This formation is characterized by abundant quartz veins, which probably supplied the diagnostic white quartz clasts in the conglomerate (figure 21, 22).
Lithic arkoses on Saturna Island contain a high percentage of quartz (mean 56 percent) which was probably derived from quartz veins of the Darrington Phyllite. These rocks also contain a high percentage of 83
Figure 21. Outcrop of quartz-phyllite conglomerate in the Protection Formation on Sucia Island.
Figure 22.. Outcrop of the Darrington Phyllite near Wickersham Washington. This unit may have served as a source rock for the conglomerate shown in figure 20. graphitic phyllite and schist fragments. Sedimentary and volcanic rock-fragments in this petrofacies may have been derived from source rocks in the North Cascades, in addition to the San Juan Island ter- ranes. The Nooksack Group, the Wells Creek Volcanics, the Cultus Forma tion, the Shuksan Metamorphic Suite and the Chilliwack Group all contain rock-types that are also present in the lithic arkose petrofacies. It is difficult to determine relative percentage of detritus from the San
Juan Island terranes and the rocks of the North Cascades; however, derivation of lithic fragments from both sources is probable. The re duction in mean percentage of potassium feldspar and the increase in the
P/F ratio relative to the high-plagioclase arkose may be due to deposition of plutonic material from the western North Cascades. Rocks of the Yellow Aster Complex (table 4) are leucotronjhemitic to gabbroic
(Misch, 1977) and contain much less potassium feldspar than quartz diorites and granodiorites of the Coastal Plutonic Complex (Roddick,
1965). A zone within the massive boulder conglomerate on Waldron Island
(Extension Formation) contains clasts of orthogneiss which are similar
In composition and texture to those present in the Yellow Aster complex of the North Cascades (figure 23). Deposition of this material and of detritus from the Darrington Phyllite may be related to Late Cretaceous tectonism near the Shuksan Thrust, along which uplift of the Darrington
Phyllite occurred (Misch, 1977).
Dacite-rich Arkose Petrofacies
Dacite-rich arkose petrofacies (figure 24) contain mean percentages of quartz (33.8 percent) and plagioclase (29.8 percent) which are within one standard deviation of quartz and feldspar values for rocks of the Figure 23. Outcrop of boulder conglomerate containing gneissic clasts in the Extension Formation on Waldron Island near Mail Bay. 87 88 high-plagiclase arkose petrofacies. Heavy minerals average only 6.3 percent and the epidote/(epidote + biotite) ratio is very low (8.0).
The mean P/F ratio is only slightly higher than mean values of the high plagioclase arkoses (figure 16). Rocks of this petrofacies, however, average 8.8 percent intermediate to acidic volcanic rock-fragments.
The dacite-rich petrofacies is recognized in rocks in the south eastern portion of the Nanaimo River area on Vancouver Island (figure 1) in the Decourcy Formation and at Southey Point on Saltspring Island and on Thetis Island in the Cedar District and Decourcy formations (figure
18). Additionally, samples of the Geoffrey Formation from Thetis Island counted by Simmmons (1973) occupy a similar position on QFL diagrams as rocks of the dacite-rich arkose petrofacies. No fossils were found at these locations and time boundaries of this petrofacies cannot be precisely delineated. However, nearby, roughly coeval sections suggest that the dacite-rich arkose petrofacies was deposited at these locations from H. vancouverense through early P. suciaensis Zone time.
The dacite-rich arkose petrofacies exhibits high, mean Q-mode factor loadings for factor three, which suggest an end-member composi tion controlled by intermediate to acidic volcanic rock fragments, and factor one, controlled by percentage of quartz and feldspar. Moderate factor loadings on factor four suggest some influence from an end-member dominated by basic volcanics. High factor loadings on factor one prob ably correlated with influx of plutonic debris from the Coastal Plutonic
Belt and/or the Jurassic Island Intrusions on Vancouver Island. High factor loadings on factor three can be correlated with dacites and ande- sites of the Late Paleozoic Sicker Group which outcrop on Vancouver
Island as well. Dacitic rock-fragments in the dacite-rich arkose are 89
texturally and lithologically indistinguishable from dacites in the
Sicker Group. Dacites and andesites may have also been derived from the
Bonanza Group.Moderate factor loadings for factor four may correlate
with deposition of detritus from the Karmutsen Basalt.
Southeast sediment-dispersal directions at Yellow Point suggest
progradation of material from rocks of Wrengellia directly into the
Nanaimo Basin (figure 8). However, northwest sediment-dispersal direc
tions are recorded at Southey Point and on Thetis Island (figure 8).
This suggests that material derived from rocks on the Insular Belt was
deposited into the central portions of the basin, where it was trans
ported longitudinally northwestward along a regional slope controlled by
basin paleogeography. At Southey Point and on Thetis Island, the
percentage of volcanic rock-fragments drops relative to rocks of this
petrofacies on Vancouver Island (Appendix II). As material was
transported northwestward, it was probably mixed with plutonic debris
derived from the Coast Plutonic Complex.
Basalt-Bearing Lithic Arenite
The basalt-bearing lithic arenite petrofacies comprises one of the most distinctive petrofacies in the Nanaimo Basin, although only four
samples were counted. The mean percentage of quartz is 29.3 percent and
the mean percentage of plagioclase is relatively low (18.5 percent).
The P/F ratio is the highest present in Nanaimo petrofacies (mean 0.95,
figure 16). Chert content is also very high (mean 27.3 percent). This petrofacies contains small percentages of metamorphic and intermediate
rock-fragments and relatively high percentages of basaltic
rock-fragments (mean 6.8 percent) and sedimentary rock-fragments (mean
10.5 percent). Heavy mineral content averages only 3.0 percent. 90
Figure 24. Photomicrograph of thin-section of dacite-rich arkose from the Cedar District Formation at Southey Point, Saltspring Island.
Figure 25. Photomicrograph of thin-section of basalt-bearing lithic arenite from the Extension Formation along the Nanaimo River. 91 Basalt-bearing lithic arenites have been collected in the Extension
Formation, within 1_. schmidti-B. chicoensls barren interzone time, along
the Nanaimo River and in downtown Nanaimo (figure 18). The sample of
this petrofacies which was collected from the city of Nanaimo indicates
greater influence from chert-rich sources than samples collected along
the Nanaimo River. Chert content averages 14 percent for samples
collected along the Nanaimo River, whereas the sample collected from an
outcrop in downtown Nanaimo contains 68 percent chert. This particular
sample is compositionally similar to rocks of both the chert-rich lithic
arenite and basalt-bearing lithic arenite petrofacies. It was assigned
to the basalt-bearing lithic arenite petrofacies, however, on the basis
of paleocurrent as well as petrographic data. Eastward paleocurrents measured near the sample location indicate derivation of sediment from
nearby sources along the western margin of the basin (Figure 8) as
opposed to rocks of the chert-rich lithic arenite for which paleocurrent measurements suggest derivation from sources in the San Juan Islands and
North Cascades.
The basalt-bearing lithic arenites exhibit high factor loadings for
factor two (controlled by chert content) and factor four (controlled by
basalt-fragment content). The mean value for factor four in this petro
facies is surprisingly low (0.24128). However, the mean value for the
three samples collected along the Nanaimo River is much higher (0.74694).
Since the sample collected at outcrops in the city of Nanaimo contains a
very high percentage of chert, the variance of this petrofacies, expressed
by the magnitude of the factor loadings, is dominated by factor two.
Factor four is overshadowed and the mean factor loading is relatively low. Basaltic and clastic sedimentary rock-fragments in this petrofacies were probably derived from the Karmutsen Basalt and underlying Triassic meta-siltstones, respectively. Units of the basalt-bearing lithic arenites rest directly on the Karmutsen Basalt, and paleocurrent directions to the east indicate derivation from Wrengellian rocks.
Chert may have been derived from several sources, including bedded cherts and chert nodules in limestones of the Buttle Lake Formation, in the Sicker Group (Muller, 1977b), and in limestones underlying and overlying the Karmutsen Basalt (Carlisle, 1963; Carlisle and Suzuki,
1965). Additionally, some chert-like grains may have been derived from altered glass rims that characterize some pillows in the Karmutsen
Basalt. 94
Petrologic Evolution of the Nanaimo Basin
Paleocurrent and petrographic data from the Nanaimo Basin can be correlated with stratigraphic patterns and used to reconstruct the infilling of the basin during the Late Cretaceous. Geographic and chronologic distributions of petrofacies in the Nanaimo Group, together with paleocurrent data and distribution of rock-types within the Nanaimo
Basin, allows the extent and timing of deposition from source areas surrounding the Nanaimo Basin to be ascertained. Derivation of large amounts of sand and gravel from a specific source area surrounding the
Nanaimo Basin can be related to tectonism within that source terrane.
Compositional data from the Comox Formation suggest derivation from several small, very local source terranes. On Saltspring Island, the
Comox Formation partially surrounds an uplifted block of Sicker Group
Volcanics and Tyee Intrusions. Radial paleocurrents directions measured by Hansen (1976) in the Comox Formation at this locality indicate the coarse-grained sediment was shed from this block in all directions.
The Comox Formation at this locality contains a high percentage of dacitic rock-fragments, which suggest derivation from rocks of this up lifted block. In contrast, samples of the Comox Formation at Saanich
Peninsula are characterized by a high percentage of potassium feldspar, plagioclase and monocrystalline quartz, which were probably derived from the nearby Middle Jurassic Island Intrusions and/or the Wark and
Colquitz gneisses.
Compositional data from the Haslam and Extension formations suggest that during B. elongatum to I_. schmidti Zone time, the southern portions of the basin, including the Cowichan River area, received a large amount of sediment from chert-rich terranes in the San Juan Islands. 95
Paleocurrent measurements suggest westward progradation of chert-rich
detritus from the San Juan Terranes into the Cowichan River area.
Sediment derived from the North Cascades was also deposited during this
time interval. Gneissic cobbles in conglomerates of the Extension
Formation on Waldron Island are lithologically identical to rocks of the
Yellow Aster Complex. Southern and southwestern paleocurrents in the
Extension and Haslam formations on Orcas, Clark and Barnes islands and modal analyses made on sandstones from these formations also suggest
that coarse-grained sediment derived from source areas in the North
Cascades was deposited during this time interval ( figure 26).
In the northern Nanaimo Basin, easterly directed paleocurrents and
compositional data indicate that conglomerates and sandstones of the
Extension Formation were derived from Paleozoic and Early Mesozoic ter
ranes of the Insular Belt. The Extension Formation in the Nanaimo River area is composed of detritus from the Karmutsen Basalt, the Sicker
Group, the Jurassic Island Intrusions, and possibly the Bonanza Group.
Rocks of the Extension Formation at Mouat Point, on North Pender Island are high-plagioclase arkoses. These rocks suggest possible derivation
from the Coastal Plutonic Belt.
Conglomerates and coarse-grained sandstones of the Extension Forma
tion contrast greatly with finer—grained clastic sediments of the under
lying Haslam Formation and overlying Pender Formation throughout the
Nanaimo Basin. Paleocurrent and petrographic data indicate that detri
tus of the Extension Formation was derived from all four major struc
tural provinces surrounding the Nanaimo Basin; the Coastal Plutonic
Belt, the North Cascades and Late Paleozoic and Early Mesozoic rocks of
the San Juan Island terranes and the Insular Belt. This influx of 96
Figure 26. QFL diagram comparing Nanaimo rocks deposited during B. elongatum to B. chicoensis time (dominantly chert- rich lithic arenites) and those deposited during H. vancouverense to P. suciaensis time in the San Juan Islands and the Cowichan River area. 97
Q
• B. elongatum - B. chicoensis Zone O H. vancouverense - Psuciaensis Zone
\ 98 coarse-grained clastic sediment during J3. elongatum to Ji. chicoensis
Zone time may be related to uplift in areas surrounding the Nanaimo
Basin. The relationship between thick deposits of conglomerate and
regional uplift has been documented by many authors (i.e., Speiker,
1949). Rocks deposited during B. chiconensis range zone time include
the Pender Formation, and locally rocks of the overlying Protection
Formation and underlying Extension Formation. Rocks of the J3. chicoensis Zone time on Waldron Island and at Cusheon Creek are chert-rich lithic arenites. These rocks record continued supply of sediment from terranes of the San Juan Islands. During this time
interval, a large amount of plutonic material was also deposited into
the basin from the Coastal Plutonic Belt. On South Pender Island and at
Cusheon Creek on Saltspring Island, a major change in sediment composition, from chert-rich lithic arenites to high-plagioclase arkoses, occurs within the Pender Formation (figure 27). At Mouat Point on North Pender Island, the high-plagioclase arkose #1 petrofacies is present in rocks of the Extension and Pender formations. These units indicate that the detrital modes of sandstones in the Nanaimo Basin were substantially altered by addition of detritus derived from the Coast
Plutonic Belt, beginning in B_. chicoensis or late I_. schmidti Zone
time. In the Nanaimo River area, sediments deposited during j3.
chicoensis Zone time record increasing dominance of the Island
Intrusions as major source terranes. The overlying Protection Formation
in the Nanaimo River area is characterized by plutonic debris from this
source.
Hopliplacenterus vancouverense and M. pacificum fauna are present
only in the Cedar District Formation. However, parts of the overlying 99
Figure 27. QFL diagram showing gradation from chert-rich lithic arenites(closed symbols) to high-plagioclase arkoses (open symbols) on South Pender Island and at Cusheon Creek on Saltspring Island. Diagram also illus trates gradation from chert-rich lithic arenite to lithic arkose (starred symbol) to high plagioclase arkose on Saturna Island. 100
■*)■□ Saturna • O Cusheon Creek ▲ A South Pender 101
Decourcy and underlying Protection formation were probably deposited during this time interval as well. Most sandstones deposited during this time interval in the southern and central Nanaimo Basin are high-plagioclase arkoses. Rocks on Saltspring, North Pender, South
Pender and Mayne islands all record input of plutonic detritus from the
Coastal Plutonic Belt during _H. vancouverense to M. pacificum Zone time. Sandstones deposited during this time interval in outcrops located on Sucia and Matia islands are lithic arkoses (figure 28) which record input of sediment from the San Juan Island terranes, North
Cascades and Coastal Plutonic Belt. The Protection Formation on Sucia
Island, deposited during _H. vancouverense Zone time, consists of quartz-phyllite conglomerate. This conglomerate, described earlier, is composed of detritus from the Darrington Phyllite.
Sandstones which outcrop on Saturna Island underwent complex petro logic changes during the interval of time indicated by the _B. rex Zo nule of the pacificum Zone. The basal three meters of the strati- graphic section measured on Saturna Island consists of quartz-phyllite conglomerate. Rocks in the overlying four meters of section are chert- rich lithic arenites. Sandstones in the next 83 meters of section are lithic arkoses with very high percentages of metamorphic rock-fragments
(figure 28). These strata are followed by a 48 meter covered interval.
Rocks above this interval are high-plagioclase arkoses (figure 27). No change in paleocurrent directions were noted throughout this interval, which suggests that transport of sediment from different sources was controlled by paleogeometry of the basin rather than the geographic location of the source area relative to the locality which outcrops on
Saturna Island. i02
Figure 28. Ternary diagram illustrating change in rock-fragment composition in samples taken from the Protection and Cedar District formations on Saturna Island. Samples used in this diagram include St-3, St-6, and St-7. See Appendices I and II for detailed compositional data. 103
VRF
SRF MRF
I 104
Rocks of the Cedar District and Decourcy formations on Thetis
Island, at Southey Point, on Saltspring Island, and the Decourcy
Formation at Yellow Point, on Vancouver Island, are dacite-rich arkoses. Dacitic detritus from the Sicker Group and Bonanza Group and plutonic debris from the Island Intrusions were deposited into the
Nanaimo Basin.Outcrops of this petrofacies on Thetis Island and at
Southey Point, on Saltspring Island, may record mixing of this material with sediment derived from rocks of the Coastal Plutonic Belt. Rocks at these localities show a substantial increase in plutonic material and a corresponding decrease in dacitic and andesitic rock-fragments compared to outcrops on Vancouver Island.
Deposition of part of the Decourcy Formation and the Northumber land, Geoffrey and Spray formations occurred during the _P. suciaensis
Zone time interval. The Gabriola may also have been deposited during this interval; although, pollen in the Gabriola suggest that it may be
Paleocene in age (oral comm., Ward, 1977). P. suciaensis Zone rocks are dominated by material derived from the Coastal Plutonic Belt. Rocks on
Saltspring, North Pender, Mayne, Saturna, and Galiano (Carter, 1971, examined rocks on Galiano) islands deposited in this range zone are classified as high-plagioclase arkoses (figure 18). Minor deposition of sediment from the San Juan Islands and/or the North Cascades is suggested by lithic arkoses in outcrops on Patos Island (figure 26).
Although no sediments from this interval of time were examined in the northern portion of the basin, QFL diagrams of the Geoffrey and Gabriola formations on Gabriola Island made by Packard (1972) indicate that these rocks are arkoses, probably derived from both the Coastal Plutonic Belt and the Island Intrusions. 105
Relative importance of various source areas of Nanaimo rock changes greatly throughout basin development. During initial development much of the material was derived from local island highs comprised of
Wrengellian rocks as observed in examination of the Comox Formation.
Regional tectonism resulted in major input of sediment from the San Juan
Island terranes, the North Cascades, and rock of Wrengellia during deposition of The Extension and a portion of the Haslam. The earliest evidence of sediment input from the Coastal Plutonic Belt occurs in the
Extension Formation. As development of the Nanaimo Basin continues input from other sources decreases. Detritus from the Coastal Plutonic
Belt dominates compositions of rocks deposited during middle to late stages of Nanaimo Basin development. DEPOSITIONAL SETTINGS AND ENVIRONMENTS
Sedimentary structures, stratification sequences and lithofacies of
the Nanaimo Group in the Nanaimo Basin indicate three general deposi-
tional settings: nonmarine, marginal-marine, and submarine-fan. Mar
ginal-marine and nonmarine deposits are composed of conglomerate, sand
stone, siltstone, shale and coal. Sandstone beds in these deposits are
characterized by medium- to large-scale cross-bedding (classification
after Conybeare and Crook, 1968), ripple marks, cross-lamination, and horizontal stratification. Conglomerate beds are internally feature
less, or exhibit cross-stratification and/or horizontal stratification.
Coal, siltstone and shale beds are intercalated in sandstone and con
glomerate beds.
Submarine-fan deposits are characterized by conglomerate, sand
stone, siltstone and shale beds. Many of the sandstone beds are struc
tureless. Others show diffuse horizontal bedding, dish and other water
escape structures, and/or features indicative of soft-sediment deforma
tion. Some sandstones exhibit normal-grading. Conglomerates exhibit
disorganized, inversely-graded and normally-graded fabrics. Medium- to
large-scale (Conybeare and Crook, 1968) cross-bedding is rare in sand
stones and conglomerates of this facies. Interfingering, interbedded
sandstone-siltstone, sandstone-shale, and siltstone-shale units show
"classic" turbidite bedding.
Complex intercalation of the non-marine, marginal marine, and
submarine-fan deposits occurs in the Nanaimo River area. These deposits
have been combined into a "mixed-facies" on figure 4. 106 107
Nonmarine Deposits
Detailed examination of primary sedimentary structures and their vertical and lateral relationships, lithology and geometry implies that rocks of the Nanaimo Group at some localities were deposited in a non marine environment. Nonmarine deposits are recognized in the Nanaimo
River area, on Waldron Island, and possibly on South Pender Island.
These rocks are, in turn, divided into three lithofacies based on domi nant rock-type: conglomerate facies, sandstone facies, and coal, shale and siltstone facies.
Conglomerate Facies: The conglomerate facies includes rocks that con tain over 50 percent conglomerate and in most occurrences of this facies, these deposits contain over 75 percent conglomerate (figure 29).
The remainder of the facies consists largely of sandstone but also in cludes rare coal seams, generally less than 20 cm thick, and sparse interbeds of siltstone and shale. This facies is recognized in rocks of the Extension Formation in the Nanaimo River area and along the south eastern portion of Waldron Island where coals are absent. Some of the thick conglomerate beds in the Extension Formation on South Pender
Island may also be nonmarine.
Most clasts in nonmarine conglomerates in the Nanaimo River area range from 1 to 5 cm in diameter, although the largest clast observed was approximately 30 cm in diameter. Clasts in conglomerates on Waldron
Island are much larger and range from 5 to 20 cm in diameter. The largest clasts at this locality are over 80 cm in diameter. Conglom erate clasts range from angular to rounded.
The majority of conglomerates in this facies exhibit a disorganized fabric (figure 30) although, fair a(t) b(i) and a(p) a(i) fabric devel- 108
Figure 29. Idealized section illustrating sedimentary structures of the conglomerate facies. Cros--bedded sandstone interbed. Interbeds range from 10 cm. to 4 meters in thickness. Sets range from 8 to 40 cm. in height. Small lens of pebbly sandstone
Lenticular interbed of cross-bedded conglomerate planar and trough cross-bedding are observed in these interbeds. Some planar cross-beds range up to 2 meters in set height.
Very small sandstone lens, exhibiting horizontal bedding.
Thick disorganized conglomerate, clasts average 1 to 20 cm. in diameter.
Interbed of cross-bedded sandstone. Bed thins laterally and is marked only by an erosion surface in some portions of the outcrop.
Interbed of cross-bedded conglomerate which fines-upward to horizontally-bedded pebbly sandstone. Erosion surface separating two massive beds of disorganized conglomerate. Some conglomerate units show a(t) b(i) and a(p)a(i) clast orientation. 110 opment (Walker, 1975) is recognized at some localities. Many conglomer
ate beds rest on scour surfaces.
Interbeds of cross-bedded and horizontally-bedded sandstone, pebbly
sandstone, and conglomerate are present in the conglomerate facies (fig
ures 29, and 31). These interbeds range from 10 cm to 4 meters in
thickness and commonly exhibit sharp contacts with the underlying and
overlying conglomerate. Many interbeds thin rapidly along strike. In
some cases, fining-upward units of boulder conglomerate grade into peb
bly sandstone and sandstone. Interbeds of conglomerate, pebbly sand
stone and sandstone are commonly cross-bedded. Both planar and trough
cross-bedding is present. Most cross-bed sets range from 8 to 40 cm in height, although some planar cross-bed sets up to two meters in height are present. Some interbeds consist of a single cross-bed set. Hori
zontally-stratified sandstone, pebbly sandstone and conglomerate are also present in the interbeds of the conglomerate facies. Horizontally-
stratified units are commonly interbedded with cross-bedded units.
Interpretation of Sedimentary Features in the Conglomerate Facies:
Lithologic patterns and sedimentary structures in the conglomerate
facies resemble those in the proximal portions of modern alluvial fans and braided streams discussed by Miall (1977, 1978) and Rust (1978).
In modern gravelly, braided streams, disorganized gravel beds are generally deposited during "surges." Surges occur during major floods, in which very large amounts of coarse-grained material is moved by a process transitional between debris-flow and normal bedload movement
(Scott and Gravlee, 1968). A flood surge along the Rubicon River resulted in deposition of over 2 meters of disorganized gravel in berm terraces along either side of the thalweg and in large boulder bars Ill
Figure 30. Disorganized fabric in conglomerate from the nonmarine conglomerate facies in the Extension Formation along the Nanaimo River west of the railroad trestle.
Figure 31. Cross-bedded conglomerate from the nonmarine conglomerate facies in the Extension Formation along the Nanaimo River just east of the railroad trestle.
113
(Scott and Gravlee, 1968). Miall (1977) has noted that, in modern braided streams, disorganized and horizontally-bedded gravels are depos ited during development of longitudinal bars, whereas cross-bedded grav els are deposited during migration of transverse and lingloid bars.
Similar structures in the conglomerate facies of the Nanaimo Group may have developed in bar and/or berm terraces during major floods.
McGowen and Groat (1971) state that cross-bedded sands and pebbly sands will accumulate in alluvial-fan deposits in channels flanking gravel-bars (1) during waning states of floods that laid down gravel- bars, (2) when lesser floods were not competent to transport gravel, and
(3) when the locus of maximum discharge shifted. Sandstone interbeds in the conglomerate facies of the Nanaimo Group exhibit structures that are very similar to those reported in nonmarine conglomerates of the Van
Horn Sandstone studied by McGowen and Groat (1971) and probably developed by similar processes.
Fining-upward sequences present in the conglomerate facies resemble stratification sequences in the Scott-type vertical profile discussed by
Miall (1977) and Boothroyd and Ashley (1975). Miall (1977) suggests that this sequence is characteristic of gravelly, braided rivers. The
Scott-type vertical profile, like vertical profiles in the nonmarine conglomerate facies in the Nanaimo Group, is dominated by disorganized conglomerates deposited by longitudinal bar migration. Gravel-sand cycles present in this sequence develop during waning floods (Boothroyd and Ashley, 1975).
Sandstone Facies: The sandstone facies is defined as an assemblage of nonmarine rocks that contain less than 50 percent conglomerate. Most deposits of this facies contain less than 20 percent conglomerate. m
Siltstones comprise less than 5 percent of this facies. Most rocks in this
facies are very fine- to medium-grained sandstones. Shale and thin coal beds
are present, although relatively rare. The sandstone facies is characterized by
fining-upward sequences of cross-bedded, cross-laminated and horizontally-bedded
sandstone (figure 32). Rocks of the nonmarine sandstone facies are recognized
in the Extension and Decourcy formations in the Nanaimo River area.
Medium-scale cross-bedding is the most abundant sedimentary structure in
sandstones, pebbly sandstones and conglomerates of this facies (figure 33). Both
trough and planar cross-beds are observed. Sets range in height from 5 cm to 1.5 meters. Megaripple marks are observed on bedding surfaces in the Extension
Formation along the Nanaimo River. These megaripples are approximately 12 cm in height and have a wavelength of 50 to 70 cm (figure 34).
Horizontal-stratification is common in siltstone, sandstone, pebbly sand stone, and conglomerates of the sandstone facies (figure 35). Scattered current-ripple cross-lamination is present in some horizontally stratified beds.
Current ripple cross-lamination and type "A" (Jopling and Walker, 1968) ripple-drift cross-lamination are present in the sandstone facies. Undulatory to straight-crested ripple-marks are observed along bedding planes. Sets of current ripple and ripple-drift cross-lamination range from 2 to 6 cm in height. Ripple marks exhibit heights of .75 to 2 cm and wavelengths of 3 to 10 cm. Current ripple cross-lamination is present at the base of some medium-scale cross-bed sets (figure 33). This ripple cross-lamination sometimes exhibits back-set bedding, relative to overlying cross-bed foresets.
Small conglomerate and pebbly sandstone interbeds in the sandstone facies, in sharp contact with underlying and overlying sandstone, and from 30 cm to 2 meters in thickness. These interbeds are of variable shape and some exhibit a well-defined lenticular shape. Conglomerates and pebbly sandstones are commonly 115
Figure 32. Idealized stratigraphic section illustrating sed imentary structures the nonmarine sandstone facies. HORIZONTALLY-LAMINATED SILTSTONE
HORIZONTALLY-BEDDED SANDSTONE very fine- to fine-grained, fines upward to siltstone
CROSS-BEDDED SANDSTONE fine- to medium-grained 9-35 cm. sets, set size decreases upward
CONGLOMERATE INTERBED
CROSS-BEDDED SANDSTONE pebbly, coarse- to medium-grained 40-100 cm. sets CROSS-BEDDED CONGLOMERATE 30-90 cm. sets DISORGANIZED CONGLOMERATE 116 Figure 33. Cross-bedding in nonmarine sandstone facies. Note back set bedding in ripple cross-lamination at the base of the cross-bed foresets. Outcrop is Extension Formation along the Nanaimo River east of the railroad trestle.
Figure 34. Mega-ripples along a bedding plane in the nonmarine sandstone facies of the Extension Formation along the Nanaimo River east of the railroad trestle. 118
3f
I
'£&?* ■■i'. •■^5fc < * ' V *&**• ±;:*tiW & . 119 Figure 35. Horizontal stratification in nonmarine sandstone facies of the Extension Formation along the Nanaimo River east of the railroad trestle. 1?1 cross-bedded or horizontally-stratified, with pebbles aligned in the bedding planes. However, lenses ofdisorganized conglomerate are also present. Clasts in these conglomerates range from 10 cm in diameter to coarse-grained sand. Most clasts range from 1 to 3 cm in diameter. Large- and very large-scale (Conybeare and Crook, 1968) planar cross bedded units (figure 36) are present in the easternmost outcrops of the Protection (or Extension?) Formation on Newcastle Island and in the Decourcy Formation near Duke Point (Rinne, 1973). Sets of these cross bedded units range up to 11 meters in height and inclinations of the large- and very large-scale foresets vary from 12 to 26 degrees. Beds composed of large-scale foresets are commonly composed of very coarse- to medium- grained sandstone. Horizontally-stratified and medium-scale cross-strati fied beds truncate the upper boundary of beds containing the large-scale f oresets. Fining-upward sequences in the sandstone facies are made up of three divisions (figure 32). The basal portion of the sequence commonly consists of disorganized conglomerate, cross-bedded conglomerate and/or cross-bedded pebbly sandstone. Cross-bed sets near the base of the sequence average between 30 cm and 1 meter in height. The middle portion of the sequence is dominated by planar and trough cross-bedded sandstone. Cross-bed sets average 8 to 25 cm in height. Both cross-bed set height and grain-size decrease upward in this portion. Grain-size generally decreases from coarse- to medium-grained sandstone to fine-and/or very fine-grained sandstone. The upper portion of the fining-upward sequence is characterized by current ripple and rarely ripple-drift cross-lamination and/or horizontal stratification. Grain-size in this upper portion generally ranges from very fine-grained sandstone to siltstone. Most Figure 36. Large scale planar cross-stratification in the Protection Formation on ' the north end of Newcastle Island. 124 fining-upward sequences are incomplete and the thickness of these sequences is highly variable, ranging from 1 to over 12 meters. Interpretation of Sedimentary Structures and Lithologic Patterns in the Sandstone Facies: Sedimentary structures and stratification sequences in nonmarine sandstone facies in the Extension Formation along the Nanaimo River resemble those observed in modern braided-stream environments by Williams and Rust (1969), Reineck and Singh (1973), Miall (1977, 1978) and Rust (1978). Miall (1977) argues that planar cross-bedding develops in modern, sandy braided streams by migration of transverse bars, lingloid bars and/or sand waves, whereas trough cross-stratification develops by migration of subaqueous megaripples such as those present in the Exten sion Formation along the Nanaimo River. Theoretical studies by Southard (1971) and field studies by Harms and others (1975) indicate that hori- 2ontal-stratification in gravels and coarse- to medium-grained sand develops by migration of longitudinal bars or within an upper-plane bed flow-regime. Theoretical studies also indicate that horizontal-strati- fication in medium-grained sand to silt beds develops in a lower plane bed flow-regime (Southard, 1971) or by migration of small-scale ripples in very shallow water (Smith, 1971). These processes may have been re sponsible for development of similar sedimentary structures observed in the nonmarine sandstone facies of the Nanaimo Basin. Stratification sequences in the sandstone facies resemble the Platte-type vertical profile described by Miall (1977). In the Platte- type vertical profile, as in deposits in the nonmarine sandstone facies of the Nanaimo Basin, fining-upward sequences are dominated by cross bedded sand. These sequences in the Platte River result from migration 125 of lingloid bars in a very shallow braided system, with little topographic relief (Miall, 1977). The nonmarine sandstone facies in the Nanaimo River area probably developed in a similar kind of braided system. Coal, Shale and Siltstone Facies: The coal, shale and siltstone facies (figure 37 ) is characterized by areally extensive coal seams intercalated in very fine-grained sandstone, siltstone and shale. Coal comprises approximately 20 to 30 percent of the facies. Conglomerate beds are present, although they are relatively rare. This facies is recognized in the Pender (includes Douglas and Newcastle Seams of Clapp, 1912) and Exten sion (includes Wellington Seam of Clapp, 1912) formations in the Nanaimo River area. Sandstone and siltstone beds in this facies generally exhibit horizon tal bedding. Some small-scale current ripple cross-lamination is also present. Shale beds are dark gray, carbonaceous and very fissil. Coal seams are composed of high-volatile bituminous coal (Muller and Atchison, 1971). Thickness of coal seams is highly variable. At most localities, the Wellington Seam ranges from 1.2 to 2.1 meters in thickness, the Douglas Seam averages 1.5 meters in thickness and the Newcastle Seam ranges from 1 to 1.2 meters in thickness (Muller and Atchison, 1971). Coal and associated fine-grained clastic rocks were probably deposited in quiet-water. In modern braided streams, silts, clay and organic sediment are deposited as the site of maximum deposition shifts; and channels are progressively abandoned. Progressive migration of quiet-water regions within a braided system through time may have produced laterally extensive, although not necessarily time synchronous, coal seams associated with interbeds of fine-grained clastic rocks. 126 Figure 37. Interbedded coal very fine-grained sandstone, silt stone and shale in the Pender Formation on the north end of Newcastle Island: 127 128 Marginal-Marine Deposits Sedimentary features of detrital rocks of the Nanaimo Group at some localities suggest that they were deposited in a marginal-marine envi ronment. These deposits are recognized on Sucia, Matia, Patos, Tumbo, South Pender, Waldron, Skipjack, and Saltspring islands and in the Nanaimo River area. Marginal-marine deposits are divided into three facies based on dominant rock-type: (1) sandstone-conglomerate facies, (2) siltstone-shale facies, and (3) hemipelagic shale facies. Sandstone-Conglomerate Facies: The sandstone-conglomerate facies (figure 38; is comprised of approximately 80 percent sandstone and 20 percent conglomerate although large regional variations are noted in these percentages. In some outcrops, conglomerate is sparse; others contain over 70 percent conglomerate. The sandstone-conglomerate facies is present in the Decourcy Formation on Sucia and Matia islands, in the Geoffrey or Gabriola Formation on Patos Island, in the Gabriola Formation on Tumbo Island, in the Extension Formation on Waldron and Skipjack islands and in the Comox Formation on Saltspring Island. The sandstone-conglomerate, marginal-marine facies is also recognized in the Protection Formation in the Nanaimo River area. Some sandstones, pebbly sandstones and conglomerates in this facies are characterized by abundant low-angle inclined-stratification (figure 39;. Inclination of these beds ranges from 0 to 10°. Scattered wave and current ripple cross-laminations are superimposed on low-angle inclined beds. Wave and current ripple-marks are also present, although rare, on bedding planes of low-angle inclined beds. Ripple-marks range in height from .75 to 2 cm and wavelength ranges from 3 to 8 cm. Figure 38. Stratigraphic section of the Decourcy Formation from Sucia T.sland showing typical sedimentary structures of the sandstone-conglomerate marginal- marine facies. Section measured along the north side of Echo Bay. SUCIA ISLAND-DECOURCY FORMATION 2 5 Low-angle inclined lamination, angle of inclination 0 to 15 degrees Sandstone is fine to coarse-grained. 2 0 Cross-bedded conglomerate, pebbly sandstone and sandstone, some lenses of disorganized conglomerate Some horizontally bedded sandstone units. Sandstone is medium to coarse-grained. Erosion Surface Very fine- to fine-grained horizontally to ripple-bedded sandstone, some siltstone. Small lenses of cross-bedded medium to coarse-grained sandstone and cross-bedded to disorganized conglomerate are present. meters 130 Figure 39. Low-angle inclined-stratification in the Decourcy Formation on.Sucia Island. Photograph taken along the north side of Echo Bay. 133 Medium-scale cross-bedding, present in sandstones, pebbly sand stones and conglomerates, is the most common sedimentary structure in this facies (figure40 ). In cross-bedded pebbly sandstones and conglom erates, pebbles are aligned along bedding planes. Both trough and pla nar cross-bedding are present. Sets vary in height from 5 cm to over 1.5 meters. In some cases, superimposed ripple-marks are present on bedding planes of cross-bed foresets. Current directions measured on these ripple-marks are perpendicular to directions measured on trough axes of the cross-bed foresets (figure 41). Cross-bed sets are often bounded by large, undulatory reactivation surfaces (figure 42 ). Undulations on reactivation surfaces are assymetric and exhibit a steeply-inclined "stoss" side and a gently-inclined "lee" side. Sediment-transport directions suggested by orientation of these undulations are commonly 180° opposed to directions suggested by orientation of the cross-bed foresets. Rare herringbone cross-bedding is present on Sucia and Waldron islands. In figure 43, current directions measured on the upper foresets record sediment transport to the east, whereas inclination of the lower set indicates sediment transport to the west. Disorganized conglomerate interbeds are present in this facies (figure 44). Most clasts in these beds range from 3 to 15 cm in diameter with the largest clasts approximately 20 cm in diameter. In contrast, clast-sizes in low-angle inclined and cross-bedded conglom erates commonly range from 2 to 5 cm in diameter. Disorganized conglom erate interbeds range in thickness from 2 cm to over 4 m. Thin conglom erate interbeds are often a gravel pavement "one pebble” thick. Most 134 Figure 40. Trough cross-stratification in sandstone-conglomerate marginal-marine facies. Outcrop in the Protection Formation on the southwest coast of Newcastle Island. 135 136 Figure 41. Current ripples superimposed on a cross-bed foreset. Sediment-transport direction measured for ripples (R) is perpendicular to direction measured on cross-bed foreset (F). Outcrop is Protection Formation located 4 to 6 km south of the town of Nanaimo. 138 Figure 42. Reactivation surfaces between cross-bed sets. Outcrop is Decourcy Formation on Sucia Island along the north side of Echo Bay. Figure 43. Herringbone cross-bedding. Outcrop is Decourcy Formation on Sucia Island along the north side of Echo Bay. 140 disorganized conglomerate beds rest on a well-developed scour surface. These sandstones and conglomerates occasionally contain accumulations of Ostrea sp. shells, along with other shallow-water bivalves, and shell debris (figure 45). Cross-bedded sandstone, pebbly sandstones and conglomerate beds, as well as disorganized conglomerate beds, commonly exhibit a lenticular outline. Disorganized and cross-bedded conglomerates sometimes fill channels cut into cross-bedded and horizontally bedded sandstone. Laterally-fining sequences in which disorganized conglomerate is replaced by cross-bedded conglomerate, which is in turn replaced by cross-bedded sandstone, occur along strike. Sharp depositional contacts are commonly present between bedding units. Beds of horizontally-laminated, very fine-grained sandstone and siltstone are also present in the sandstone-conglomerate facies (figure 46). Some units of horizontally-laminated siltstone have been affected by soft-sediment deformation and are wavy to convoluted. Small, lentic ular interbeds of planar or trough cross-stratified sandstone are some times present in horizontally-bedded units. These beds range from 8 to 30 cm in thickness and approximately 1 to 5 m in length. Cross-bed sets within these lenses range from 7 to 15 cm in height. Small lenses of conglomerate are also present within the horizontally-bedded units. Flaser-bedding (figure 47 ) and intraformational mud-chip conglomerates (figure 48 ) are associated with horizontal bedding. Both single and bifurcated (Reineck and Wunderlich, 1968) flasers are present in flaser-bedded units. Intraformational mud-chip conglomerates are comprised of pieces of siltstone, shale and "woody" organic material emplaced in a matrix of fine-grained sandstone. 141 Figure 44. Interbedded conglomerate and sandstone beds. Outcrop is Decourcy Formation on Sucia Island along the north side of Echo Bay. Figure 45. Accumulation of Ostrea sp. shells in sandstone. Outcrop is Extension Formation on Waldron Island at Fishery Point. 143 Figure 46. Horizontal-stratification in very fine-grained sand stone of the Decourcy Formation on Sucia Island near Fossil Bay. Figure 47. Flaser bedding in the Protection Formation on the west coast of Newcastle Island. 147 ' Figure 48. Mud-chip intra-formational conglomerate in the Protection Formation on the west coast of Newcastle Island. 149 Sedimentary structures in the sandstone-conglomerate facies are arranged in fair to poorly developed stratification sequences (figure 38). The stratification sequences are initiated with horizontally-bed ded, very fine-grained sandstone to siltstone often containing mud-chip intraformational conglomerates and flaser bedding. The next group of sedimentary structures within this stratification sequence is separated from the underlying group by a prominent erosion surface. This group of structures consists of interbeds of cross-bedded sandstone, pebbly sand stone, and conglomerate, along with interbeds of disorganized conglomer ate. This group of structures constitutes the thickest portion of the stratification sequence. Sandstones, pebbly sandstones, and conglomer ates which contain low~angle inclined-stratification overlie, and are often intercalated with, cross-bedded units of the middle portion of the stratification sequence. Interpretation of Sedimentary Structures and Depositional Patterns in the Sandstone-Conglomerate Facies; Sedimentary features of the sand stone-conglomerate facies suggest that it was deposited in a barred, high-energy, longshore-dominated, beach complex (figure 49) subject to tidal fluctuations. Stratification sequences in this facies are very similar to stratification sequences observed by Clifton (as quoted by Harms et al. , 1975) in high energy shoreline deposits in the Miocene Branch Canyon Sandstone (figure 50). According to Clifton, sedimentary structures in this sequence correspond to the particular portion of a high-energy beach in which they were developed. These structures are identical to those present in the sandstone-conglomerate facies of the Nanaimo Group. Figure 49. Idealized high-energy, barred, shoreline profile, (after Komar, 1974) . FORESHORE UPPER SHOREFACE LOWER lOFF- SHOREFACE . SHORE SEA CLIFFS MHWL MLWL BERM K? • LONGSHORE LONGSHORE BAR TROUGH 152 Figure 50. Comparison between stratigraphic section measured on Sucia Island and that measured by Clifton (as quoted by Harms et al., 1975) of the marginal-marine facies in the Miocene branch Canyon Sandstone. meters FORESHORE 3 & & 0 0 " Q UPPER SHOREFACE LOWER SHOREFACE OFFSHORE 25-E BRANCH CANYON BEACH FACIES SANDSTONE SUCIA ISLAND 154 Low-angle inclined stratification in the sandstone-conglomerate facies is similar to inclined-stratification which develops along the foreshore in modern beach environments discussed by Harms and others (1975), Clifton (1969), and Hunter and others (1979). Low-angle in~ clined-lamination is formed in modern beaches by wave-swash. As a wave moves up along the foreshore, it deposits coarse-grained material from suspension as a thin layer on top of the berm slope. When the wave returns as backflow, a portion of the water percolates through the berm face. Thus, the backflow has less energy, and finer-grained material is deposited on top of the coarse layer (Clifton, 1969). The angle of in clination of this stratification is controlled by the slope of the berm face. A similar process could have formed low-angle inclined stratifi cation observed in the sandstone-conglomerate facies. A large part of the sandstone-conglomerate facies is composed of interbeds of disorganized conglomerate and cross-bedded sandstone, peb bly sandstone and conglomerate. Paleocurrents measured from structures in the sandstone-conglomerate facies on Sucia, Matia, and Patos islands, and on a portion of Waldron Island, indicate southeastward transport parallel to the basin-margin. This contrasts with measurements made in nearby nonmarine and submarine-fan sequences which suggest transport dominantly to the northwest. Westward paleocurrents measured in sand stone-conglomerate marginal-marine facies on Newcastle Island indicate transport parallel to the northern margin of the basin whereas southeastward directions measured in non-marine strata on Newcastle Island, suggest transport to the east towards the central portion of the basin. Sediraent-dispersal parallel to the coastline suggests transport by littoral drift in longshore troughs. Studies by Hunter and others (1979) and Komar (1974) indicate that the upper shoreface of a high-en~ ergy shoreline may contain one or more longshore bars, and associated longshore troughs (figure 49), oriented parallel or nearly parallel to the coastline. Lenticular geometry of interbedded, disorganized con glomerate and cross-bedded sandstone, pebbly sandstone and conglomerate beds in the sandstone-conglomerate marginal-marine facies, along with paleocurrent measurements parallel to basin margins, suggest that these beds were deposited in upper-shoreface longshore troughs. According to Hunter and others (1979), high longshore current velocities are devel oped within these troughs as flow becomes channelized. They report that sand waves (producing planar cross-bedding), megaripples (producing medium-scale trough cross-bedding), and disorganized gravel-lag deposits are developed in modern longshore troughs off the coast of southern Oregon. These bedforms trend parallel to the shoreline. They further state that surfaces developed at the base of longshore trough sequences are formed by erosion of the longshore bar, which has a poor preserva tion potential. The resulting vertical sequence developed by this process is identical to the assemblage of cross-bedded strata and dis organized conglomerate which forms the middle portion of sequences observed in the sandstone-conglomerate marginal-marine facies (figure 38) of the Nanaimo Group. Sequences which grade laterally from dis organized conglomerate to crossbedded sandstone in the sandstone- conglomerate marginal-marine facies, may be indicative of channelized flow. Flow velocities would have been highest near the thalweg, resulting in deposition of disorganized conglomerate. As flow 156 velocities decreased laterally away from the thalweg, finer-grained sediment was deposited. Tidal modification of upper shoreface deposits is suggested by cur rent ripple-marks superimposed at 90° on cross-bed foresets, herringbone cross-bedding and asymmetric reactivation surfaces. Ripple-marks super imposed on cross-bed foresets which exhibit a paleocurrent orientation perpendicular to that of the foreset, form in modern environments during a receding tide. Sand-wave and dune crests become emergent and open- channel flow develops between crests (Klein, 1970). Herringbone cross bedding, although rare, provides good evidence of periodic reversals in current direction in Nanaimo shoreline deposits. Asymmetric reactiva tion surfaces, which commonly bound sets of cross-bedded strata in the sandstone-conglomerate facies, may have been formed by reversals in flow direction initiated by tidal fluctuation. In modern tidal-dominated environments, bedforms are subject to a constructional event (migration during the dominant tidal phase), and a destructional event (erosion during a subordinate phase). During the destructional phase, the bedform is rounded and a low-angle undulatory reactivation surface is formed on top of it. Cross-bedding then develops on top of this surface during the next constructional phase (Klein, 1970). Many of the reactivation surfaces observed in the sandstone- conglomerate facies are fairly large and extend over the entire bedform. Processes which produce reactivation surfaces in theoretical studies, such as small-scale features migrating on top of a major bedform (McCabe and Jones, 1977) or random interaction of ripple cosets (Allen, 1973) will not produce surfaces of this size. Silt-drapes, which are indica tive of reactivation surfaces developed in a fluvial environment by 157 low-flow wave rounding (Collinson, 1970), are not present. In addition, reactivation surfaces in the Nanaimo are characterized by assymmetric undulations which suggest a reversal in flow direction. The presence of these features are consistent with a tidal origin for reactivation surfaces in sandstone-conglomerate marginal-marine facies. Tabular beds of horizontal-stratification, commonly overlain by erosional surfaces of the upper shoreface, resemble deposits of lower shoreface and offshore regions of modern beach complexes discussed by Harms and others (1975). Horizontal bedding in very fine-grained sandstones and siltstones of the sandstone-conglomerate facies is similar to lamination developed in flume experiments by Southard (1971) in a lower plane-bed flow regime. Interbeds of cross-stratified sandstone and gravel“lag accumulations in horizontally-laminated sandstones are similar to interbeds observed in the lower shoreface of a modern shoreline by Hunter and others (1979) which develop as a result of increased wave-energy during major storms. Mud-chip intraformational conglomerates probably developed during major storms as well. Semi-consolidated siltstone and shale units, deposited in the offshore zone during quiet periods, were probably broken up and emplaced in a sand matrix by increased wave-energy. Flaser-bedding in lower shoreface strata probably developed as a result of tidal fluctuation or storm-wave modification. According to Reineck and Wunderlich (1968), flaser bedding is formed by a two-stage process. During a period of current activity, sand is deposited by bedload processes, forming current ripple cross-lamination. Mud and silt are kept in suspension by current activity. When current velocity drops (such a drop may occur during a stillstand), ripple migration 158 ceases and mud and silt are deposited from suspension. When current velocity increases during a storm or by tidal movement following a stillstand, mud and silt are eroded from ripple-crests. Sand movement by ripple migration reoccurs, preserving mud flasers in the protected ripple troughs (Reineck and Wunderlich, 1968; Reineck and Singh, 1973). Siltstone-Shale Facies: The siltstone-shale facies is present on Sucia Island in the Cedar District Formation and on Waldron and South Pender islands in the Pender Formation. It is composed almost completely of siltstone on South Pender and Waldron islands whereas on Sucia Island, the sequence contains approximately 25 percent shale. Rare sandstone and conglomerate beds are also present in outcrops of this facies. Sedimentary structures and stratification sequences in the silt stone-shale facies are very similar to those in the sandstone-conglom erate facies. Low-angle inclined-stratification, trough and planar crossbedding, lenticular conglomerate interbeds, wave~ripples and wave- ripple cross-lamination are observed in siltstones in this facies. Horizontally-laminated shale is observed in the Cedar District Formation on Sucia Island. In contrast to the sandstone-conglomerate facies, fos- siliferous material is much more abundant in the siltstone-shale facies. Bivalve and ammonite shells occur sporadically throughout the sequence and are concentrated in lag-accumulations (figure 51). Interbeds of cross-bedded and massive conglomerates range from 4 cm to 8 m in thick ness. Most clasts are 2 to 7 cm in diameter. Some conglomerate inter beds contain mollusk, shell-fragments and/or intraformational clasts of mudstone and siltstone, as well as extraformational clasts. Figure 51. Lag-accumulation of bivalve shell fragments in siltstone-shale marginal-marine facies in the Cedar District Formation in Fossil Bay on Sucia Island.. 161 Strong similarity between sedimentary structures of the siltstone- shale facies and the sandstone-conglomerate facies indicates that they were probably deposited by similar processes. Siltstone-shale marginal-marine deposits probably represent beach development at much lower wave~energy than in the sandstone conglomerate facies. Greater abundance of fossiliferous material can be attributed to greater preservation potential in low-energy shoreline environments. Shale Facies: The shale facies is present in the Haslam Formation in the Nanaimo River area. This facies is composed of dark-gray to black mud stone. Mudstone ranges from fissil to blocky. Unweathered deposits are generally massive and structureless. Ammonite and Inoceramus sp.fossils indicate a marine origin. Intercalation with nonmarine conglomerate facies of the Extension Formation suggest that these shales were deposited in relatively shallow water, in contrast to mudstone in submarine-fan facies in the central portions of the basin. Facies Relationships in Non-Marine and Marginal-Marine Deposits Geographic and chronologic changes in depositional environment along the margins of the Nanaimo Basin can be determined by examination of vertical and lateral relationships between the marginal-marine sandstone- conglomerate, siltstone-shale, and shale facies and the non-marine conglom erate, sandstone and siltstone shale and coal facies in outcrops of the Nanaimo River area and the San Juan Islands. These rocks allow delineation of transgressions and regressions at specific localities in the Nanaimo Basin as well as energy and type of depositional process. Stratigraphic relationships between nonmarine and marginal-marine facies in the Nanaimo River area indicate abrupt regression following 162 deposition of the Haslam Formation and illustrate changes in deposition al environment as sediment was transported eastward from source areas in the western portion of this area towards the central portion of the basin. In outcrops along the Nanaimo River, an erosional contact exists between marine shales of the Haslam Formation and nonmarine conglomer ates and sandstones of the overlying Extension Formation. A sequence consisting of coal, siltstone, and silty sandstone is interbedded with conglomerates and sandstones near the base of the Extension Formation. Outcrops of the Extension Formation in the western portion of the Nanaimo River area are composed largely of conglomerate and grade later ally to the east into rocks of the sandstone facies. A sharp deposi tional contact exists between the Extension Formation and overlying coal, shale, siltstone and silty sandstone beds of the Pender Formation. These rocks, in turn, exhibit a sharp depositional contact with margin al-marine sandstone-conglomerate facies of the Protection Formation, near the east coast of Vancouver Island. Paleocurrent measurements in this section trend east in nonmarine deposits and east and southeast in marginal-marine deposits (figure 18)* Deposition of coarse-grained, nonmarine rocks of the Extension Formation over hemipelagic shales of the Haslam Formation suggests regression in the Nanaimo River area, perhaps due to tectonic uplift. Rocks near the contact between these two formations illustrate details of this regression. The lowermost Extension Formation was probably deposited in an environment characterized by a fairly low gradient, 163 resulting in deposition of coal and fine-grained clastic sediments. These- rocks are overlain by sandstones and conglomerates, which indicates that stream gradient and sediment supply may have increased during deposition of the Extension Formation at this locality. Rocks of the Extension Formation also record a decreasing stream grad ient from west to east. Conglomerate facies in the western portion of the Nanaimo River area were probably deposited in braided channels at high velocities along a relatively steep gradient. Detritus in this facies was probably deposited near source areas in uplifted regions along the peri phery of the Nanaimo Basin. The character of this formation changes greatly in the eastern portion of the Nanaimo River area, however. Strati fication sequences in the sandstone facies closely resemble sequences dis cussed by Miall (1977) in the Platte River in which sand was deposited in a regime characterized by a relatively low gradient. Coal, siltstone, shale and silty sandstones of the Pender Formation may indicate a further decrease in gradient near the boundary between non marine and marginal-marine rocks. Sandstone facies of the Extension Forma tion were deposited in major channels whereas, siltstone, shales, silty sandstone and coal beds may represent associated overbank flood deposits. In the Extension and Protection formations on Newcastle Island, rare nonmarine sequences consisting of sandstone and conglomerate are inter bedded with sandstone and conglomerate deposited in a marginal-marine environment. Nonmarine stratification sequences at this locality are characterized by large-scale planar cross-bedding (figure 36) which is overlain by fining-upward beds of cross-bedded and horizontally bedded rocks. The Pender Formation on Newcastle Island consists of an assemblage of silty sandstone, siltstone, shale and coal. 164 Large-scale planar cross-bedding in nonmarine facies on Newcastle Island may be analogous to Gilbert-type foreset bedding, which develops when streams with a coarse-grained sediment load deposit material into a body of water significantly deeper than the depth of the stream channel (Friedman and Saunders, 1978). Large-scale foreset beds on Newcastle Island may represent development of small high-destructive deltas. Fin ing-upward sequences, which overlie these foresets, may record develop ment of braided distributary channels along a nearly horizontal erosion- al surface which is observed on top of the foresets. Three paleocurrent measurements made in nonmarine strata on Newcastle Island indicate transport of sediment to the southeast whereas, measurements made in marginal-marine strata suggest sediment transport to the west. These paleocurrents probably record interaction between constructive fluvial processes and destructive marginal-marine processes involved in development of the delta. Sediment was prograded southeast by fluvial processes onto the delta, where much of it was resedimented by marginal-marine processes, including longshore drift, wave action, and tidal action. Coal, siltstone, shale and silty sandstone of the Pender Formation may have developed in interdistributary areas of the delta, or more likely by overbank flooding in quiet water regions near channel mouths. Stratigraphic sections in Nanaimo rocks along the southeastern portion of the basin also illustrate interrelationships between facies of the marginal-marine and nonmarine environments. On Sucia Island, marginal-marine siltstone-shale facies of the Cedar District Formation are overlain by marginal-marine sandstone-conglomerate facies of the Decourcy Formation. Vance (1975) suggested that a major fault is pre 165 sent between rocks of the Cedar District Formation and the overlying sand stones. However, Ward (oral comm., 1977; 1979) found H. vancouverense Zone fossils in shales which overlie the fault proposed by Vance (1975) and depositionally underlie sandstones of the Decourcy Formation. Covered areas within the Decourcy Formation on Sucia Island may be interbeds of siltstone-shale marginal-marine facies. Stratigraphic relationships of the sandstone-conglomerate and siltstone-shale marginal-marine facies on Sucia Island suggest that the shoreline at this locality was subject to change in depositional setting from a high-energy regime, which resulted in deposi tion of the sandstone-conglomerate marginal-marine rocks, to a lower energy regime, resulting in deposition of siltstone-shale facies. Local struc tural changes in basin geometry could have greatly altered beach slope and/or the geomorphic configuration of the beach itself. Either of these changes may have resulted in large fluctuations in wave energy at par ticular localities. Interbedding of nonmarine and marginal-marine facies is observed in the Extension and Pender formations on Waldron Island. Along the south side of Cowlitz Bay, the lower Extension Formation is characterized by marginal-marine sandstones and conglomerates. These are overlain, along an erosional surface by a thick unit consisting largely of nonmarine (some of these beds may have been deposited in subaqueous conditions) conglomerates which make up the upper Extension Formation at this local ity. This unit is in turn depositionally overlain by marginal-marine siltstones of the Pender Formation. This depositional sequence suggests that initial regression, indicated by deposition of nonmarine conglomerates, was followed by transgression and deposition of the Pender Formation along a relatively low energy shoreline. 166 Submarine-Fan Deposits Rocks of the Nanaimo Group in central portions of the Nanaimo Basin are interpreted as submarine-fan deposits. Submarine-fan strata are recognized in portions of the Nanaimo River area (mixed facies) throughout the Gulf Islands (with the exception of parts of Saltspring and Saturna islands, and Tumbo Island), in the Cowichan River area, and on the Saanich Peninsula and associated islands. Submarine-fan deposits are also present on Clark, Barnes, Orcas, Stuart, Johns, Cactus, and Flattop islands of the San Juan Islands (figure 4). Submarine-fan strata of the Nanaimo Basin can be divided into facies discussed by Walker and Mutti (1973), Mutti and Ricci Lucchi (1975), and Walker (1978). These facies are: (1) clast-supported conglomerates and pebbly sandstones (facies A), (2) massive sandstones (facies B), (3) "classic turbidites" (facies C, D, and E) and (4) matrix-supported conglomerates and chaotic deposits (facies F). These facies occur in three types of associations: (1) fining-upward sequences, (2) coarsening-upward sequences, and (3) noncyclic sequences. Clast-Supported Conglomerates and Pebbly Sandstones (Facies A) Clast-supported conglomerates are very abundant in submarine-fan sequences of the Nanaimo Basin. Most clasts in these conglomerates range from 1 to 20 cm in size. Clasts are commonly subangular to round ed. Conglomerate bed-thickness ranges from less than 1 cm to over 480 m (Extension Formation on South Pender Island). Four conglomerate fabrics have been observed in facies A deposits in the Nanaimo Basin. These are (1) disorganized, (2) inversely-graded, (3) normally-graded, and (4) horizontally and cross stratified. Common features of facies A conglom erates are shown in figure 52. Figure 52. Idealized stratification sequence illustrating sedimentary features of facies A submarine-fan conglomerates. NORMAL GRADING INTO PEBBLY SANDSTONE BIMODAL GRAIN—SIZE DISTRIBUTION (CLAST-MATRIX) NORMALLY GRADED SEQUENCES INVERSE GRADING, GOOD TO POOR A(I)AiP) ORIENTATION DISORGANIZED CONGLOMERATE 168 169 Many facies A conglomerates of the Nanaimo Basin have a disorganized fabric (figure 53). Grading, stratification and clast lineation have not been observed in disorganized conglomerates. Disorganized conglomerates commonly exhibit a channel-shape and fill scours cut into finer grained rocks. Inversely-graded conglomerates are uncommon in much of the Nanaimo Basin; although, they are locally abundant on Stuart Island and at several other localities (figure 54). These beds exhibit a gradual upward increase in conglomerate clast-size. Most inversely-graded conglomerates occur in 0.5 to 3.0 m thick beds. Johnson (1978) reported a transition from disor ganized to inversely-graded conglomerates in the Extension Formation on Johns, Cactus, and Flattop islands. Some conglomerate beds exhibit inverse gradation from medium-grained sands with clasts averaging 2 to 5 cm in size. Normally-graded conglomerates are very abundant in the Nanaimo Basin. Excellent examples are present at Mouat Point on North Pender Island. Many inversely-graded and disorganized conglomerates are overlain by normally-graded beds. Normally-graded beds range from 0.5 to 7 m in thick ness and often have erosive, basal-contacts (figure 55). Near the base of many of these units, a biomodal clast-distribution is present. Normally- graded conglomerates in the Nanaimo Basin exhibit both coarse-tail and dis tribution grading (as defined by Middleton, 1967). In some cases, grading continues into coarse- and medium-grained sandstone. Good to poor a(i) a(p) clast orientation (Walker, 1975) is present in some normally and inversely-graded conglomerates (figure 56). Clasts are oriented parallel to the curent direction and imbricated upstream. Large-scale planar cross-bedding and horizontal-bedding have been observed in facies A conglomerates. Cross-beds are planar and sets Figure 53.Disorganized conglomerate from the Decourcy Formation on Mciyne Island near Dinner Bay. Figure 54. Inverse-grading in the Portection Formation at Mouat Point, North Pender Island. •"/'t Figure 55. Normal-grading in conglomerate bed in the Extension Formation along the south coast of South Pender Island. Figure 55. A(i) a(i) clast orientation in the Extension Formation on the north coast of Barnes Island. 175 range from 0.5 to 2.5 m in height (figure 57). Horizontal stratifica tion has also been observed at several localities. However, both cross stratified and horizontally-stratified conglomerates are rare in sub marine-fan deposits of the Nanaimo Basin. Horizontally-stratified and cross-stratified conglomerates are generally confined to interbeds less than 3 m thick which die out rapidly along strike. Pebbly sandstones represent a gradation between clast-supported conglomerates of facies A and massive sandstones of facies B in sub marine-fan deposits of the Nanaimo Basin. Pebbly sandstones range from conglomeratic sandstone in which pebbles are in contact with one an other, to units in which pebbles, enclosed in a sand matrix, are sepa rated from one another by 1 to 10 cm. Both ungraded and normally-graded pebbly sandstones are common in submarine-fan sequences of the Nanaimo Basin. Interpretation of Sedimentary Features in Clast-Supported Conglomerates and Pebbly Sandstones: Clast-supported conglomerates and pebbly sand stones in the Nanaimo Basin resemble resedimented conglomerates studied by Davies and Walker (1974), Walker (1975, 1977, 1978), Middleton and Hampton (1973), and Harms and others (1975), which were deposited by a composite process in which material was maintained in suspension by fluid turbulence and dispersive pressure between grains. According to Walker (1975), whether a conglomerate has a disorganized, inversely- graded, or normally-graded fabric, depends on how clasts moved during transport and how they were deposited. In disorganized flows, turbu lence and dispersive pressure may be too high for vertical and lateral size segregation to develop. Deposition occurs rapidly as velocity slows and the material "freezes" (Middleton and Hampton, 1973). Disor- 176 Figure 57. Cross-bedding in conglomerate bed in the Extension Formation on the south coast of South Pender Island. 178 ganized conglomerates result from deposition of material being trans ported at relatively high velocities (Walker, 1975, 1977, 1978; Harms et al., 1975). Well-developed basal scour-surfaces and lenticular outlines of disorganized conglomerate beds in the submarine-fan deposits suggest that velocities necessary for development of a disorganized fabric occur in well developed channels. Inversely-graded conglomerates resemble those discussed by Walker (1975) which represent a decrease in flow velocity from that required for development of a disorganized fabric. The development of inverse- grading in resedimented conglomerates is not well understood. Bagnold (1954) theorized that inverse-grading was produced by dispersive pres sure created by grain collisions. Larger grains are pushed toward the top of the flow, where shear strain is least, and smaller grains move towards the bottom. This process, however, requires an inclination greater than 18°, which was probably not present in the Nanaimo Basin. Middleton (1970) believed that inverse-grading results from a "kinetic sieve mechanism," whereby smaller grains fall into spaces between larger grains, displacing the larger grains upward. Inversely-graded conglomerate beds in the Nanaimo Basin must have been very rapidly deposited. According to Davies and Walker (1974), rapid "freezing" is necessary in order to preserve coarsening-upward fabrics. Research by Walker (1975) on resedimented conglomerates similar to those in the Nanaimo Basin suggests that normally-graded conglomerates represent deposition at a lower flow velocity than that necessary to produce inversely-graded conglomerates. Davies and Walker (1974) state that normal-grading develops as coarse clasts are deposited from a con centrated layer at the base of a flow. Maximum current velocity 179 develops near the base of a flow and decreases rapidly upward (Middleton and Hampton, 1973). During sediment movement, coarser grains are concentrated in higher velocity portions of the flow near the base and lighter, smaller grains are entrained near the top. Normal-grading in conglomerates of the Nanaimo Basin may also represent diminishing flow strength within a depositing current. Harms and others (1975) suggest as flow velocity decreases, competence of the flow decreases and smaller and smaller grains are progressively deposited. According to Middleton (1967), coarse-tail grading, observed in some facies A conglomerates of the Nanaimo Basin, develops in flows of higher concentration than that necessary to produce distribution-grading. Bimodal clast-distributions present at the base of some normally-graded beds in the Nanaimo Basin probably result from contamination in which clasts from a previously deposited flow are entrained by the next flow. Davies and Walker (1974) state that a(p) a(i) clast-fabrics,, which are common in submarine-fan conglomerates of the Nanaimo Basin, develop as a result of multiple clast collisions during sediment transport. An a(i) p(i) fabric is the most stable fabric that can develop in a sediment-gravity flow (Rees, 1968). Cross-stratification and horizontal-stratification observed in conglomerates of the Nanaimo Basin are similar to stratification patterns in deep-water conglomerates studied by Winn and Dott (1977, 1978, 1979).They state that gravel in low-density turbidity flows was probably transported by saltation and bedload rolling and sliding. Deposition occurred layer-by-layer, resulting in development of horizontal- and cross-stratification. Massive Sandstones (Facies B) Massive sandstone beds are very common in submarine-fan deposits of 180 the Nanaimo Basin. Individual sandstone beds range from 1 cm to 75 m in thickness. In contrast to sandstones of non-marine and marginal-marine deposits, cross-bedding is relatively rare. Many facies B sands are featureless and ungraded (figure 59). An idealized section showing sedimentary structures in facies B sandstones of the Nanaimo Basin is presented in figure 58. Facies B sands are commonly pebbly or conglom eratic at their base and fine upwards. Lutite clasts 3 to 20 cm in size are sometimes present within featureless portions of the facies B sands (figure 60). Lutite clasts sometimes exhibit an a(p) a(i) orientation similar to that observed in facies A conglomerates. Dish structures are also present in many facies B sandstone beds in the Nanaimo Basin (figure 61). These range from isolated, slightly con cave-upward dishes to dense interconnected systems forming anastomosing- lamination. Pillar structures are occassionally observed at the inter sections between dishes as well Diffuse horizontal-lamination is often present near the top of many of the facies B sands (figure 62). Horizontal-lamination ranges from flat, to wavy, to highly convoluted. Two types of convolute-lamination are present. The first type exhibits gradation from wavy to sharply convoluted (figure 63). Convolutions are symmetrical and pillar struc tures may be present at their crests. The second type of convolute- bedding exhibits horizontal-lamination, separated from highly convolute- lamination by one or more shehr surfaces (figure 64). Facies B sands of the Nanaimo Basin often fine upward. Some grade into wavy to convolute, very fine-grained sandstone or siltstone. Com monly interbeds of "classic" turbidites are observed between units of massive sandstone. 181 Figure 58. Idealized stratigraphic section showing sedimentary features of facies B submarine-fan sandstones in the Nanaimo Basin. INTERBEDDED SILTSTONE AND SANDSTONE SILTSTONE, WAVY TO CONVOLUTE BEDDING WAVY TO CONVOLUTE BEDDING FINING UPWARD SEQUENCE ANASTOMOSING DISH STRUCTURE AND/OR SEPARATED DISHES DIFFUSE HORIZONTAL LAMINATION OUTSIZE LUTITE CLASTS MASSIVE, FEATURELESS, MED. GRAINED SANDSTONE POOR GRADING? PEBBLYAT BASE, MAY BE CONGLOMERATIC 182 Figure 59. Massive structureless sandstones in the Decourcy Formation south of Dinner Bay on Mayne Island. Figure 60. Lutite clasts in facies B sandstones in the Cedar District Formation at Southey Point, Saltspring Island. 184 Figure 61. Dish structures in sandstones of the Decourcy Formation at Dinner Bay, Mayne Island. Figure 62. Horizontal stratification in facies B sandstones of the Gabriola Formation near Edith Point. 187 Figure 63. Gradation from horizontal to wavy to convolute bedding in sandstones of the Cedar District Formation on the south coast of Thetis Island. Figure 64. Convolute bedding underlain by shear surfaces (dotted lines) in the Protection Formation at Mouat Point, North Pender Island. 189 Interpretation of Sedimentary Features in Massive Facies B Sandstones According to Link (1975), facies B sandstone beds, such as those present in the Nanaimo Basin, were deposited largely by high-density turbidity currents with subordinate influence by grain-flow and fluid- ized sediment-flow processes. Thick accumulations of sand in submarine- fan sequences may represent several flows welded together. The presence of large lutite clasts in these flows suggests that they were partly erosive in nature and entrained large chunks of semiconsolidated mud. Orientation of these lutite clasts suggests that deposition of facies B sands occurred by processes similar to those postulated for deposition of facies A conglomerates. Dish and pillar structures in facies B sands of the Nanaimo Basin probably developed by rapid dewatering during compaction of quickly- deposited sand. Theoretical studies by Lowe and LoPiccolo (1974) indi cate that dishes are formed when argillaceous laminations or small con centrations of clay and silt act as semipermeable barriers to upward- moving, sediment-water slurries. This results in horizontal-flow along laminations, which filters out fine-grained material from the water and concentrates it in pore-spaces within the laminations. The resulting clay- and organic-enriched dishes are then deformed upward by water movement along their edges. Pillar structures develop by upward move ment of water at intersections between dishes. Horizontal-stratification probably forms near the top of facies B sandstone beds in the Nanaimo Basin during waning flow, resulting in development of an upper-plane bed flow-regime. Horizontal-lamination may form by reworking of previously deposited sediment or by continued deposition at a lower flow velocity (Walker, 1978). Convolution of this 190 lamination could have resulted from two processes. Symmetrical convolu tions, in which a gradation from wavy to convolute bedding is observed, were probably developed by rapid-dewatering during deposition. Water is expelled upward and turbulence within the sand-water mixture deforms horizontal-lamination. The second type of convolute bedding is charac terized by development along a shear surface. Deformation of horizon tal-lamination above that surface probably resulted by gravity sliding of semiconsolidated sediment. "Classic'' Turbidites "Classic" turbidites (Walker, 1978) are interbedded units of sandstone-shale, sandstone-siltstone, or siltstone-shale that can be described in terms of the Bouma sequence (Bouma, 1962). They have been discussed in detail by several authors (Bouma, 1962; Middleton and Hampton, 1973; Walker and Mutti, 1973; Link, 1975, Walker, 1976, 1978; Nilsen, 1977; and others). The first three divisions of the Bouma sequence occur in the coarse-grained layer. At the base of the unit, Bouma division A consists of structureless or graded sandstone. Bouma division B is characterized by horizontal-lamination and division C is characterized by ripple cross-lamination. In Bouma's original description, division D represents horizontally-laminated shale, whereas division E represents massive, unbedded shale. However, in the Nanaimo Group, as in many weathered or tectonized units (Walker, 1978), facies D and E cannot be discriminated. Therefore, for the purposes of this paper, Bouma divisions D and E are combined and represent unbedded shale units which occur between sandstone or siltstone units in "classic" turbidites of the Nanaimo Group. 191 "Classic" turbidites have been divided into facies by Walker and Mutti (1973). Facies C "classic" turbidites are characterized by com plete Bouma sequences and high sandrshale ratios. Facies C "classic" turbidites occur in many localities in the Nanaimo Basin and generally have sandstone beds ranging from 40 cm to 2 m in thickness. Bouma A divisions are very well developed and usually comprise the largest portion of the sandstone bed. The D-E division is generally poorly-developed and averages 2 to 10 cm thick. Facies C turbidites are pictured in figure 65. Sandrshale ratios range from 20:1 to 2:1. Facies D turbidites begin with division B or C and coarser-grained portions are generally siltstone or medium- to very fine-grained sand stone. Facies D beds are the most common type of "classic" turbidite observed in the Nanaimo Basin (figure 66). Sandstone beds range in thickness from 80 cm to less than 1 cm. Sand: shale ratios of facies D "classic" turbidites are highly variable, but most range from 2:1 to 1 :20. Walker and Mutti (1973) originally developed these divisions to discriminate beteen thick-bedded and thin-bedded turbidites. However,in many cases, relatively thick-bedded "classic" T^cde turbidites are present in the Nanaimo Basin. Additionally, a well-developed gradation is present between Ta_e and T^cc}e "classic" turbidites in submarine-fan sequences. However, T c(je turbidites in the Nanaimo Basin are usually characterized by sandstone or siltstone units 1 to 8 cm in thickness and sand:shale ratios less than 1:4. A more abrupt break is noted between Tbcde units and T C(je units than between Ta_e units and T^cde units in the Nanaimo Basin, in terms of sandstone bed thickness and sand:shale ratio. Facies E "classic" turbidites are also present in the Nanaimo Figure 65. Facies C turbidite exhibiting Tabcde bedding. Outcrop is the Haslam Formation on the couth end of Barnes Island. Figure 66. Facies D turbidites exhibiting T and T C(ie bedding. Outcrop is the Cedar District Formation near Mouat Point, North Pender Island. 194 Basin. They exhibit Tc(je and rare Tbccje bedding. Facies E turbidites are characterized by distinctive, starved ripple-laminae developed in sand and silt interbeds (figure 67) (Mutti, 1977; Mutti and Ricci Licchi, 1975, Nilsen and Dibblee, 1979). Ripples generally have a wave length of one to three inches and an amplitude of one-half to three fourths of an inch. Sand:shale ratios of these beds are high (near 1:1) yet sandstone beds are generally thin (1 to 6 cm thick). Facies E tur bidites in the Nanaimo Basin contrast greatly with TC(je facies D tur bidites in which sand:shale ratios are much lower. Bouma C divisions in facies E "classic" turbidites range from siltstone to very fine-grained sandstone and are often convoluted. Facies E "classic" turbidites are similar to facies D; however, the beds are more irregular. Facies E "classic" turbidites are interpreted as channel-margin turbidites (Walker and Mutti, 1973). A complete gradation exists between facies D and facies E "classic" turbidites. The mechanics of deposition of classic turbidites are discussed in detail by Middleton and Hampton (1973) and Walker (1978). The succes sion of structures within a Bouma sequence records deposition of sedi ment at progressively lower velocities in a waning flow. Sandstone bed thickness and sand:shale ratios are controlled by the velocity and size of the flow. The lowermost Bouma division of a particular flow records its maximum velocity at the point of observation. Matrix-Supported Conglomerates and Chaotic Deposits (Facies F) In contrast to the clast-supported conglomerates discussed pre viously, matrix-supported conglomerates in the Nanaimo are characterized by scattered clasts within a silt and clay matrix. Clasts are generally Figure 67. Starved ripples in Bouma C division in Facies E turbidites in the Northumberland Formation near Dinner Bay, Mayne Island. 197 very poorly sorted and no lineation or sedimentary structures are noted (figure 68). Clasts range from less than one cm to over 10 cm in size. In a matrix-supported conglomerate on Saturna Island, abundant mollusk shell fragments are intermixed with conglomerate clasts. Most clasts are separated from one another by approximately 3 to 20 cm. There are regions within these conglomerates in which clasts are densely concen trated and others in which the clasts are relatively far apart from one another. There is no continuity along strike and no grading has been observed. Disturbed bedding is also very common in all submarine-fan deposits of the Nanaimo Basin, ranging from small convoluted beds to large scale slumps (figure 69) and slump folds. Within some slumps, snowball-like structures are created by rotation and contortion of semicompetent blocks. Interpretation of Sedimentary Features in Facies F: Matrix-supported conglomerates in the Nanaimo Basin are interpreted as debris-flows. Debris-flows contrast with flows that deposit clast-supported conglom erates in that material is largely supported by strength and buoyancy of the clay matrix rather than turbulence, upward escape of fluid or dis persive pressure (Middleton and Hampton, 1973). Debris-flows are generally very proximal deposits, triggered by instability along a slope. Some turbidity flows may evolve from debris flows (Hampton, 1972). Slumps and slump-folding may have been generated by instability along slopes as well within the Nanaimo Basin. Slumping occurs when higher density sandstone or conglomerate founders within highly fluidized, underlying shale and moves downslope under the influence of gravity (Potter and Pettijohn, 1976). 198 Figure 68. Matrix-supported conglomerate with siltstone matrix. Outcrop is the Cedar District Formation on south coast of Saturna Island. 200 Injection Features: Sandstone dikes and sills are present in thick mudstones of facies D thin-bedded turbidites of the Nanaimo Basin. They are commonly associated with nearby slump features (figure 70). Dikes range from 30 cm to 1 m in thickness and are often composed of fine- to medium-grained sand. Isolated pebbles have been observed in some dikes. Sills are usually thin, ranging from 3 to 10 cm. They die out rapidly along strike. Many extend only 30 cm to 2 m from the parent dike. The association between sandstone dikes and submarine slumping has been observed also by Fairbridge (1946) and Dzulynski and Radomski (1956). Sandstone dikes and sills develop as a result of high pore- pressures in either underlying or overlying sands (Harms, 1965). These increased pressures lead to decreased flow resistance in the sands and they are injected into cracks in surrounding sediments of low permeabil ity. Slumping may create tension in subjacent strata which facilitates development of injection features (Fairbridge, 1946). Additionally, earthquakes may have been important, both in producing the fractures and in triggering slides and slumping (Dzulynski and Radomski, 1956). Submarine-Fan Facies Sequences Examination of stratification sequences comprised of submarine-fan facies A through F can provide valuable information concerning subma rine-fan geometry (Mutti, 1977; Nilsen, 1977; Ingersoll, 1978b). Three sequences are recognized in submarine-fan facies of the Nanaimo Basin: (1) fining-upward sequences, (2) coarsening-upward sequences, and (3) noncyclic sequences. Fining-Upward Sequences: Two types of fining-upward sequences have been observed in submarine-fan deposits of the Nanaimo Basin. The first type commonly consists of repetitive sequences in which facies A conglom- 201 Figure 69. Slump structure in the Cedar District Formation near Gallagher Bay, Mayne Island. Figure 70. Sandstone dike in the Cedar District Formation north of Boat Harbor on Vancouver Island. Note large concretion in the shale and associated slumping. 203 erates and pebbly sandstones fine upward into facies B massive sands (figures 71, 72 and 73). In some cases, fining-upward continues into facies C and rarely D "classic" turbidites. These units are denoted as facies A, B, C fining-upward sequences in this paper. Conglomerates are characterized by an erosional basal contact and a depositional contact with sandstones above. Sequences range in thickness from 1 to 20 m. Individual structures within facies A and B deposits suggest deposition of material at progressively lower flow velocities. In some conglomeratic sequences, disorganized massive conglomerates are overlain by inversely-graded conglomerates, which in turn may be overlain by nor mally-graded conglomerates and, finally, sandstone. Contacts between these units range from sharp to gradational. Laterally-fining sequences are also present in submarine-fan depos its. Gradation from disorganized conglomerate to normally-graded con glomerate to massive sandstone is observed along strike at several lo calities. In other laterally-fining sequences, sharp depositional con tact exists between beds of disorganized conglomerate, normally-graded conglomerate and facies B sandstone. The second type of fining-upward sequence present in submarine-fan deposits of the Nanaimo Basin commonly consists entirely of "classic" turbidites. In some cases, these sequences are initiated by a massive sandstone bed which fines upwards into facies C "classic" turbidites. Fining-upward generally continues into facies D "classic" turbidites and, in some cases, completely to mudstone. These sequences are termed facies C, D fining-upward sequences in this paper. Fining-upward sequences in "classic" turbidites are characterized by several major changes (figure 74). The sand:shale ratio and average 204 Figure 71. Facies A,B fining-upward sequences in the Decourcy Formation near Dinner Bay, Mayne Island. Figure 72. Facies B,C fining-upward sequences in the Cedar District Formation at Ganges Harbor, Saltspring Island. 2 0 6 Figure 73. Detailed stratigraphic section of a portion of the of the Protection Formation at Mouat Point, North Pender Island, showing series of Facies A,B fining- upward sequences. MOUAT POINT, NORTH PENDER ISLAND 207 FINING-UPWARD SEQUENCES IN PROTECTION FORMATION meters abrupt dcposAtional contact between siltstone and s a n d sto n e pebbly sandstone fines-upward into Tery fine grained sandstone abrupt depositsonal contact between pebbly sandstone and sandstone sandstone generally featureless, some horizontal lamination, some dishes pebbly sandstone fines upward to medium-grained and finally fine-erained sandstone siltstone, horizontal to convolute bedding medium grained sandstone, featureless rsv^- -y 10_ ■ * \ pebbly sandstone ■ a — W w j disorganized conglomerate erosional scour at base of conglomerate 0__g 208 Figure 74. Diagram illustrating changes in sandstone percentage, sandstone bed thickness, and Bouma bedding divisions that occur within a typical facies C,D fining-upward sequence. 100 100 .7 5 m eters Sandstone % %ol Ta.e and Tb.# Sandstone bed 209 b a d s thickness Figure 75. Detailed stratigraphic section of a portion of the Cedar District Formation at Southey Point, Saltspring Island, illustrating facies C,D and facies B,C,D fining-upward sequences. SOUTHET POINT, SALTSPRING ISLAND 211 FINING-UPWARD SEQUENCES IN CEDAR DISTRICT FORMATION Tabode bidding fines to Tbode Facies E turbidites eonmon DETAILED SECTION meters 3. lutit® clasts In sandstone beds - 7 & & - 4 0 massive featureless sandstone, some dishes Tabode bedding fines to Tod* bedding 10. dish structures in sandstones lu tite clasts, horizontal bedding and dishes in sandstone beds 212 Figure 76. Detailed stratigraphic section of a portion of the Cedar District Formation near Mouat Point, North Pender Island, showing facies C,D and facies D fining- upward sequences. Some of these sequences grade into noncyclic sequences. 213 MOUAT POINT, NORTH PENDER ISLAND FINING-UPWARD SEQUENCES IN CEDAR DISTRICT FORMATION meters dark grey Mudstone, cut by occassional lenses of siltstone, less than 1 cm. thick, some siltstone lenses exhibit Bouaa division C b e d d in g ?cde bedding ™bcde bedding DETAILED SECTION dark grey mudstone transition between non-cyclic and fining upward sequence 214 Figure 77. Fining-upward sequence in facies C and D turbidites of the Cedar District Formation near Gallagher Bay, Mayne Island. 215 216 sandstone bed thickness decrease. Often this decrease is accompanied by a decrease of grain size within sandstone beds as well. In the upper most portions of the fining-upward sequences in the Nanaimo Basin, sand stone is replaced by siltstone. There is a rather abrupt gradation be tween beds initiated with Bouma division A or B and those with beds initiated with Bouma division C. Many of these fining-upward sequences are composite sequences, and smaller "subsequences" are present within the major sequence (see * on figure 74). Examples of C, D fining-upward sequences are shown in figures 75, 76 and 77. Figures 75 and 76 exhibit facies B sands fining-upward into thin-bedded turbidites whereas figure 77 simply illustrates fining-upward within a "classic" turbidite se quence. A third type of fining-upward sequence is present. This se quence is transitional between facies A, B, C fining-upward sequences and facies C, D fining-upward sequences. This transitional sequence is termed facies B, E, D fining-upward sequence in this paper. Facies B sandstone beds in B, E, D fining-upward sequences gener ally have a well-developed lenticular outline (figure 78). Lenses of sandstone and conglomerate may truncate "classic" turbidites developed alongside them, indicating that these deposits are at least partly ero- sional in nature. Facies E turbidites are often present just above and alongside facies B sandstone lenses. Lateral gradations of these sequences are well-defined in outcrops in the Nanaimo Basin. Thick facies B sandstone beds are often lenticular and thin greatly along strike. They are replaced laterally by facies E and then facies D turbidites. At some localities, lateral-fining continues and facies D turbidites are replaced by mudstone. 217 Figure 78. Lenticular beds of facies B sandstones which are replaced laterally by facies E turbidites. Outcrop is located south of Southey Point, Saltspring Island. 219 Coarsening-Upward Sequences: Coarsening-upward sequences are rare in submarine-fan deposits of the Nanaimo Basin. However, they are well- developed in the Haslam Formation, along the Cowichan River, and in the Protection Formation on South Pender Island. A poorly developed coars ening-upward sequence is present in the Protection Formation on North Pender Island. In coarsening-upward sequences developed in the Protection Sand stone on South Pender Island (figures 79 and 80), facies C turbidites coarsen upward into sandstone beds up to 20 m thick. Thick sandstone beds are cut by several erosional surfaces. These units may represent multiple flows in which finer-grained siltstone and shale was either not deposited or eroded by the following flow. Most sandstone beds range from 1 to 7 m in thickness. Bedding is more regular along strike than in fining-upward sequences; however, variations in bed thickness are still noted. Sequences range in thickness from 10 to 40 m. In coarsening-upward sequences developed in the Protection Sand stone at Mouat Point and in the Haslam Formation in the Cowichan River area, "classic" turbidites are much better developed. Sequences consist almost entirely of facies D turbidites. Most of these sequences are 1 to 4 m thick. Some are initiated by 0.5 to 1 m of mudstone and coarsen-upward to turbidites characterized by T^_e bedding and 10 to 40 cm thick sandstone layers. Units tend to be relatively uniform along strike, in comparison with fining-upward sequences of facies D turbidites. Noncyclic Sequences and Undifferentiated Mudstone; Noncyclic deposits in submarine-fan facies of the Nanaimo Basin are comprised of thin-bed- 220 Figure 79. Detailed stratigraphic section of coarsening-upward sequences composed of facies B,C, and D turbidites. This outcrop is in the Protection Formation along the south coast of South Pender Island. The stratigraphic section is somewhat idealized. SOUTH PENDER ISLAND COARSENIN6-UPWARD SEQUENCES IN PROTECTION SANDSTONE massive, structureless medium-prained sahdstone 3one horisontal beddine near top of sandstone Tabde bedding medium-grained sandstone some sandstone beds structureless, others show diffuse horisontal-lamination massive, featureless sandstone siltstone units 15-30 cm. thick some poorly developed ripple cross-lamination and convoluted bedding near top of sandstone beds 222 ded (sandstone and siltstone beds range from 1 to 10 cm in thickness), Tccje facies D turbidites (figure 81) and/or thick accumulations of mud stone. Sand:shale ratios in thin-bedded, noncyclic turbidites are gen erally very low, ranging from 1:4 to 0 percent sand. Bouma C division beds are commonly composed of siltstone. Units consisting of these thin beds are sometimes interrupted at intervals of 20 to 100 m by isolated 0.5 to 2 m thick sandstone beds displaying Bouma A to C divisions. In other areas, thin-bedded Tccje turbidites are interspersed in small "bun dles" between large thicknesses of undifferentiated mudstone. At some localities, fining-upward sequences grade into thin-bedded noncyclic sequences and it is difficult to distinguish between these two bedding- types. Interpretation of Facies Sequences Development of fining-upward, coarsening-upward and noncyclic sub marine-fan facies sequences suggests that deposition of these facies may have been controlled by the same kind of hydraulic conditions that pro duce similar sequences in fluvial environments. Bedding geometry of fining-upward sequences in submarine-fan facies in the Nanaimo Basin resembles bedding geometry of sequences formed by channel abandonment and migration in modern river systems. Sandstones and conglomerates of the submarine-fan fining-upward sequences are highly lenticular and many beds exhibit a well-defined channel-shape. Most fining-upward sequences are initiated by a basal scour surface which may have developed by erosion of surrounding sediment to form a channel. Fining-upward sequences are deposited in these channels. As the locus of deposition migrates, velocity of flows within the channel is reduced and finer- grained material is deposited. Many channel-shaped sandstone beds in Figure 80. Coarsening-upward sequences in the Protection Formation along the southeast coast of South Pender Island. 224 JE 2 Figure 81. Noncyclic sequence of very thin-bedded Tcde turbidites in the Northumberland Formation at Dinner Bay, Mayne Island. 226 the submarine-fan deposits of the Nanaimo Basin grade vertically and later ally into facies E "classic" turbidites. These turbidites are probably formed along channel levees (Walker and Mutti, 1973). Levee deposits develop in modern fluvial environments during floods, when channels are overtopped and water moves onto the floodplain. The immediate reduction of velocity as water moves from a confined to an unconfined state results in deposition of coarse-grained material along the channel margin. Although sand is dropped out of suspension along channel levees, it still may be moved by bedload processes. Reineck and Singh (1973) note abundant ripples developed in natural levees along modern streams. Similar processes may have been responsible for development of starved ripple-lamination along natural levees of undersea fan-channels. As turbidity flows in undersea channels overtopped boundaries, flow velocity would be reduced and any sand in suspension near the top of the flow would be immediately deposited. Most of the sand in these flows was probably derived from the head of the flow. Middleton and Hampton (1973) state that sand is carried in •x. suspension at a greater distance from the channel bottom in the head of flow than in other portions. The body of the flow probably contributed relatively little sand; however, current velocities in this portion were sufficient to keep silt and clay in suspension and move sand by bedload ripple-migration. This resulted in development of starved ripples. Silt and clay were probably deposited on top of the ripples by the tail of the flow in which Middleton and Hampton (1973) note a quick drop-off in flow velocity. Levee deposition in modern fluvial environments results in development of small ridges paralleling the stream. Development of similar ridges along undersea channels could account for the high percentage of convoluted Bouma G division beds in facies E turbidites of the Nanaimo .227 Basin. Convolution would develop by gravity-sliding as sands are deposited on inclined surfaces along the ridge. Coarsening-upward sequences may represent deposition in non-channelized sandy lobes. Coarsening-upward sequences in submarine-fan deposits of the Nanaimo Basin are similar to those formed by migration of deltaic lobes or crevasse-splays in modern environments. Nilsen (1977) states that coarsening-upward sequences in submarine-fan deposits are formed by development of sandy lobes in unconfined areas of a fan. Coarsening-upward sequences are preserved by abrupt abandonment of channels feeding these lobes, or as lobes are constructed to a high enough topographic elevation that sedimentation is impeded and alternate routes of flow are selected. Bedding units in coarsening-upward cycles exhibit far more uniform bed thicknesses along strike than fining-upward sequences. This suggests that lateral movement was relatively unimpeded. Noncyclic sequences and undifferentiated mudstone may have been deposited by sheet overflow of turbidity currents over large areas in much the same way that flood-plain deposits are developed in modern environments. Turbidity currents can travel for hundreds of kilometers in unconfined flows, especially when composed largely of fine-grained material (Nilsen, 1977; Middleton and Hampton, 1973). Noncyclicity of bedding may result from intermixing of turbidites from different channel systems, different sources, or different fan systems. The dominance of mudstone in noncyclic sequences suggests that there may have been sub stantial input of hemipelagic material as well (Nilsen, 1977). Submarine-Fan Facies Geometry Recent advances in the study of modern and ancient submarine-fan 228 and channel deposits have led to development of various models for these deposits (Mutti and Ricci Licchi, 1975; Walker and Mutti, 1973; Mutti, 1977; Normark, 1970, 1974, 1978; Ricci Lucchi, 1975; Haner, 1971, Walker, 1978, and others). According to Ingersoll (1978b), selection of a model best suited for examination of a particular fan-environment de pends on the manner in which the fan is being examined. Land-based ge ologists will utilize different criteria in a study of lithified sedi ment than a marine geologist studying modern fans with deep-tow geophys ical equipment. Selection of a model also depends on sediment type (coarse- or fine-grained), nature of the basin, and tectonic setting. According to Walker (1976), an effective model must (1) act as a norm for purposes of comparison, (2 ) act as a framework and guide for future observations, (3) act as a basis for hydrodynamic interpretation for the environment or system that it represents, and (4) act as a predictor in new geological situations. All submarine-fan models, however, have been developed from depos its in which sediment has been transported outward from a single source in a fan-like pattern (figure 84). These models relate facies sequences to geographic areas within a submarine-fan. Paleocurrent and petro- graphic data in the Nanaimo Basin, however, indicate that input of mate rial took place at many points along slopes surrounding the basin. This material was then transported axially along the length of the basin as a result of original basin paleotopography. Therefore, it is difficult to interpret proximal-distal relationships of fan deposits based on facies associations. Walker and Mutti (1973), Mutti and Ricci Lucchi (1975) and Mutti, (1977) have observed that in submarine-fans characterized by a single 229 source, specific facies sequences occur in particular areas of a fan. Fining-upward sequences indicate deposition in the inner and middle fan; coarsening-upward sequences indicate deposition in the middle and lower fan; and noncyclic sequences indicate deposition in the surrounding basin plain. However, in the Nanaimo Basin, fining-upward sequences of rocks derived from a nearby source may be overlain by a non-cyclic se quence derived from a much more distal source. These rocks may be over- lain in turn by a fining-upward sequence of material derived from a third source. This makes interpretations of fan geometry far more dif ficult. Stratigraphic Patterns of Submarine-Fan Deposits: In order to detect patterns in submarine-fan development in the Nanaimo Basin, it is neces sary to precisely delineate facies sequences within time and space. Re lationships between facies sequences within biostratigraphic range zones developed by Ward (1978) are shown in figures 82 and 83. Locations of these stratigraphic sections are shown in figure 4. Fining-upward se quences have been divided into two divisions: those dominantly composed of facies A, B, and C deposits and those composed dominantly of facies C and D deposits. Submarine-fan deposits of the Nanaimo Basin are dominated by fining-upward sequences. Coarsening-upward sequences are relatively rare and, on South Pender Island and at Mouat Point, coarsening-upward sequences are associated with nearby Facies A, B, C fining-upward sequences containing thick disorganized conglomerate beds with gravel to boulder-sized clasts. Noncyclic sequences are present throughout the basin occurring very close in space and time to facies A, B, C and facies C. D fining-upward deposits. A gradation between facies C,D 230 Figure 82. Stratigraphic sections in the Nanaimo Basin aligned northwest to southeast illustrating relationships between nonmarine, marginal-marine and submarine-fan facies. Locations are shown in figure 4. * A\S. Pender I. CHI CONTINENTAL 3 0 0 // "V\ 16 \\ r ~ l MARGINAL MARINE 200 B. rex meters ,y ' zonule i ^ i HEMIPELAGIC SHALE LlO O / // LO W\ Submarine-fan Sequences ( 7 / / .. ______M o u at . . y \\ v P o in t V: 11 FACIES A.B.C, FINING-UPWARD X" Sucia I. ^ 10 1. 1 FACIES C,D,E, FINING-UPWARD M. pacificum ^Saturna Barren interzone 9 COARSENING-UPWARD CEDAR DISTRICT DECOURCY FM. FM. ^ 3 NON-CYCLIC, MUDSTONE Ni- x Cusheon Creek Barren ^ 'oyaroji S:-.. interzone \ H. 'vancouverense 13 ■ PROTECTION FM. Cowichan . X B. cbicoensis River p e n d e r '' 15 17 Waldron I. * v f m . S tu a rt I. 12 B _ _ . X l Orcas I. Barren interzofle...... EXTENSION I. schmidti .s' A > HASLAM FM. > S a a n ic h \\ . «£ . B. elongatum Penninsula' .sS 146' —y _ / vliiuLui8-' \\ 6 //• Iry // \\ 14 * Figure 83. Stratigraphic sections in the southern Nanaimo Basin aligned west to east illustrating relationships be tween nonmarine, marginal-marine, and submarine-fan facies. Locations are shown in figure 4. Submarine-fan Sequences . \\ S. Pender I. H I FACIES A,B.C. FINING-UPWARD 16 FACIES C.D.E, FINING-UPWARD y 'B- rex V: meters . y zonule .. COARSENING-UPWARD * %. s ? NON-CYCLIC, MUDSTONE \X\ 7 // . \ \ , V ------CONTINENTAL Mouat Point MARGINAL MARINE \\ 10 M. pacificum Barren Interzone iHWH YSaturna J HEMIPELAGIC SHALE rJrSrli: • •fr.TCrrp] CEDAR DISTRICT *X*X*X .DECOMRCY FM. FM. X*x»x*« riK*K*n Cusheon jHWH* Creek K*X*X*X 's.... ,? X iH xX*, Barren ■s.-.. BJKOTS7! i-v-i S;-. interzone •S.-. V. tK* ■*»■»!«>»>«■ I » * OXiXsX raaan^— • — .• . y ’vancouyerense \\ \K~X~X~. y * s s \ T \ y + 13 . iXiX*X* PROTECTION FM. Cowichan >■' B. chicoensis 17 * ------River PENDER N 15 Waldron I. ...-? a B a;' Stuart I. 12 FM Orcas I. 'JAi'tUUVAU C*X*XxH iX*X*Xi Barren ...... XWHO X*X iX*! 8 ® \iX*Xi.* LMJ*1U EXTENSION itVtVtn XOOX ,V.V/.W*v • I •• V-. i-X’OHi l»*.**•r-r-r- »*• •' 8 SS !-v:*x*Si " r schmidti HASLAM FM. -iX^X*.*' Saanich n» *•» »♦» atY\ ..-y B. elongatum ..-r Penninsula-' \\ ► V l/'i’- l i . y flil *-* — — J \\ \\ \ iV.Vfet' to w 0^ 234 fining-upward sequences and noncyclic sequences is well developed in deposits at Cusheon Creek, South Pender Island, the Cowichan River and Horton Bay. In J3. elongatum and I. schmidti Zone time, submarine-fan facies are well developed in the Cowichan River area and in southern and southeastern portions of the Nanaimo Basin. Facies A, B, C fining-upward sequences are very well developed on Clark, Barnes, Orcas, Stuart and South Pender islands. Thick non-marine conglomerate beds on Waldron Island probably record sedimentation into deeper portions of the basin during this time interval. Rocks deposited within these range zones fine towards the southern and southwestern portions of the basin. At Cusheon Creek, Saanich Peninsula and within the Cowichan River area, stratification sequences are dominated by mudstone and noncyclic "classic" turbidites. However facies A, B, C, and facies C, D fining-upward sequences can be observed in the Cowichan River area in the Extension and Haslam formations, respectively. Coarsening-upward sequences, noncyclic sequences, and undifferentiated mudstone are also observed in the Haslam Formation in the Cowichan River area. In the B. chicoensis through M. pacificum Zones time, sedimentation patterns become more complicated. Facies C, D fining-upward sequences occur in the Pender Formation on Stuart Island and at Cusheon Creek. Facies C, D fining-upward deposits grade into mudstone at Cusheon Creek.In the Cowichan river area to the west, the Pender Formation is composed dominantly of mudstone. In the B. chicoensis-M. pacificum barren interzone, thick deposits of facies A, B, C fining-upward sequences were deposited at Mouat Point. A fault-bounded, poorly developed coarsening-upward sequence composed of 235 facies D turbidites is present within the Protection Formation at this locality. On nearby South Pender Island, the Protection is comprised of thick-bedded coarsening-upward sequences, made up of facies B and C de posits. Deposition of the Cedar District Formation occurred from II. vancouverense Zone through 13. rex Zonule time. Large variations in facies associations are present within this formation. On South Pender Island, _H. vancouverense Zone deposits consist largely of well developed facies C, D fining-upward sequences, with some interspersed noncyclic sequences. Noncyclic "classic" turbidites and undifferentiated mudstone were also deposited at this time in the Nanaimo River area. No fossils have been found in sections of the Cedar District Forma tion on Southey Point and Thetis Island, and they cannot be precisely placed within a time-framework. However, they can be tentatively corre lated with rocks deposited during H. vancouverense through B. rex Zone time based on fossils recovered from underlying and overlying rocks, as well as those recovered from nearby coeval outcrops. Southey Point outcrops are characterized by facies B, C fining-upward sequences. Facies B, E, D fining-upward sequences are especially well-developed. The Cedar District on Thetis Island is dominantly facies C, D fining-upward sequences. Rocks deposited during_M. pacificum Zone time in the Cedar District Formation on South Pender Island and at Bedwell Harbor and Mouat Point on North Pender Island consist dominantly of facies C, D fining-upward sequences. Facies A, B, C and facies C, D fining-upward sequences arepresent on South Pender Island within the Cedar District. During JB. rex Zonule time facies F conglomerates, 236 facies A, B, C and facies C, D fining-upward sequences, and noncyclic sequences were deposited on Saturna Island. Facies C, D fining-upward sequences are interspersed with noncyclic sequences on South Pender Island. On Saltspring Island, at Vesuvius Bay (not shown in sections) well developed facies C, D fining-upward sequences are present. The M. pacificum-P. suciaensis barren interzone is characterized by deposition of thick, dominantly facies A, B, C fining-upward sequences of the Decourcy Formation on Mayne, North Pender, and Saltspring is lands. Along the east coast of Vancouver Island in the Nanaimo River area, the Decourcy Formation exhibits a transition from nonmarine to submarine-fan deposits. The Decourcy Formation on Saturna Island con sists of facies A, B, C submarine-fan deposits which were probably subject to partial reworking by marginal-marine processes. Fossil control is poor within the I>. suciaensis Zone time and stratigraphic sections within this zone were not examined in detail with the exception of outcrops at Horton Bay and Dinner Bay on Mayne Island and at False Narrows on Gabriola Island. At Horton Bay and Dinner Bay, thin-bedded facies C, D fining-upward sequences are interspersed with noncyclic turbidites and thick accumulations of mudstone. These are overlain by facies A, B, C fining-upward sequences in the Geoffrey Sandstone, which in turn are overlain by noncyclic turbidites and mudstone deposits in the Spray Formation. Submarine-fan facies in the Gabriola Formation were not studied in detail; however, cursory examination of deposits on Mayne Island indicate that it is comprised dominantly of facies A, B, C, fining-upward sequences at this locality. Depositional Model of Submarine-Fan Deposits of the Nanaimo Basin In most depositional models developed for submarine-fans, the inner 237 fan (upper fan) and mid-fan are characterized by channelized flow and deposition of fining-upward sequences. As material is prograded onto the outer fan (lower fan), deposits emerge from the mid-fan channels and spread laterally, depositing individual beds as sandy lobes that accumu late in coarsening-upward sequences. Beyond the fan-margin, on the basin plain, turbidites from different channel systems, different sources and perhaps different fan-systems combine with hemipelagic sedi ments, resulting in development of noncyclic sequences (Nilsen, 1977) (figure 84). Depositional patterns in the Nanaimo Group of the Nanaimo Basin suggest that this process did not occur. Coarsening-upward sequences and noncyclic turbidites are present in what would be considered proximal "inner fan" environments. Additionally, paleocurrents and petrographic data suggest multiple sources and transport of detritus along the longitudinal axis of the basin. Submarine-fan facies probably developed in the Nanaimo Basin in a series of coalescing fans. Material was prograded from different sources into the central portions of the Nanaimo Basin (figure 85). This material was then transported longitudinally northwestward in the central and northern portions of the Nanaimo Basin and westward, towards the Cowichan River area in the southern portion of the basin. Transport of sediment probably occurred in a large number of channels. As new flows carried material into the basin, some of this material was probably transported in channels cut by earlier flows, possibly from different sources, whereas other portions of the flow may have cut and filled new channels. Facies A and B rocks were probably deposited in major channels cut by flows into the Nanaimo Figure 84. Environmental model typical of submarine fans which develop in areas unrestricted by basin morphology and by input of sediment from a single source. Sh= shelf, I.F.=inner fan, M.F.=middle fan, O.F. =outer fan, B.P.=basin plain. (After Nilsen, 1977). 239 Figure 85. Interpretive model of submarine-fan geometry in the Nanaimo Basin. SHELF Meandering Channels BASIN Sandy Lobes Crevasse Splays 2 42 Basin, whereas facies C and D rocks were deposited in smaller channels. Many of these channels were flanked by well-developed levees characterized by facies E turbidites. Although material was transported from the sides of the basin, major channel development occurred parallel to the longitudinal axis of the basin. As these channels migrated and were abandoned at various times, fining-upward sequences developed. In figure 86 development of fining-upward sequences by two channels carrying material from different sources is illustrated. Coarsening-upward sequences on North and South Pender islands out crop in association with facies A, B, C fining-upward sequences. These coarsening-upward sequences may have been deposited alongside major channels as crevasse-splays (figure 8 6 ). Coleman and Gagliano (1964) state the crevasse-splays in the Balize Delta area of the Mississippi River record geologically short (100 years average) episodes of deposi tion within a restricted basin flanking the Mississippi River. These crevasse-splays develop in topographically higher areas of the basin. A similar origin is proposed for Nanaimo coarsening-upward submarine-fan sequences. Along the Brahmaputra River, coarsening-upward sequences developed by crevasse-splays are stacked on top of each other by splay migration (Coleman, 1969). Analyses of channels in the Nanaimo Basin suggest that many of them were flanked by well-developed levees. Cre vasse-splays probably developed when these levees were breached at poor ly developed points. Current velocities developed in channels would have rapidly dropped as unconfined flow occurred within an interchannel area and coarse-grained sediment, rapidly deposited from suspension, would have formed splays. Paleocurrent data from coarsening-upward se quences indicate that the crevasse-splay deposits were prograded longi- 243 Figure 86. Block diagram illustrating development of fining- upward, coarsening-upward, and noncyclic sequences in submarine-fan facies of the Nanaimo Basin. Diagram illustrates the effect of input of sediment from different sources at different times on facies associations. F.U. = fining-upward, C.U. = coarsening- upward, N.C. = noncyclic. Source A Source B \ . \ Cr«vas**-Sploy *y** Interchannel Area \ 245 tudinally along the basin in the same manner as channelized deposits. Material in crevasse-splay deposits was spread laterally away from major channels by overbank flows, then prograded longitudinally along the basin down a regional slope by gravitational processes (figure 8 6 ). Crevasse-splays have also been noted in submarine-fan facies in the Ouachita Mountains by Moiola and Nilsen (as quoted by Stanley and Bertrand, 1979). Coarsening-upward sequences present in the Cowichan River area may represent true "outer fan" deposition. Chert-rich sands in the Cowichan River area imply that these submarine-fan deposits developed predomi nantly from source areas in the San Juan Islands. Coarsening-upward se quences in the Cowichan River area are generally present at localities characterized by noncyclic sequences and facies C, D fining-upward se quences, in contrast to coarsening-upward sequences on North and South Pender islands. Coarsening-upward sequences in the Cowichan River area may have been deposited at the termini of channels that developed by transportation of material from source rocks in the San Juan Islands. Noncyclic sequences occur in and nearby areas in which facies C, D and A, B, C fining-upward sequences are deposited. On Saturna Island, noncyclic sequences occur just above facies F deposits, which are gener ally present only in very proximal portions of a submarine-fan. Addi tionally, a well-developed gradation exists in several areas between facies C, D fining-upward sequences and noncyclic sequences. Nelson and Nilsen (1974) state that "ponding" of thin-bedded facies D turbidites is very common in restricted basins. In the Nanaimo Basin, this "ponding" probably occurs in large interchannel areas. In most submarine-fans, interchannel areas are characterized by fining-upward sequences. 246 Material is prograded in inner and mid-fan areas within well-developed channels and overbank deposition results in accumulation of interchannel deposits. These flows generally spread radially from an inner-fan channel to mid-fan channels which cover most of the fan area (figure 84). Since mid-fan channels are all being fed at the same time by the same flow, overbank deposition in the interchannel area probably would consist largely of facies C, D fining-upward sequences and mudstone developed by migration of those mid-fan channels. However, only a por tion of the channels present in the Nanaimo Basin were occupied by specific gravity flows. The fraction of the channels occupied depended on the size of the flow and the location of the source area. Another flow, within a different time-interval and from a different source, may have reoccupied some of the channels used by the earlier flow. However, some sediment transport probably took place in channels not used by the earlier flow and in channels cut by the new flow as well. As a result, the nature of sedimentation in a particular interchannel area depended on its proximity to not one, but several networks of channels occupied by different flows at different times. A particular flow may have deposited a thick facies C "classic" turbidite in an interchannel area at a particular locality. A later flow from a different source, occupying channels farther away from this particular interchannel local ity, may have resulted in deposition of a thin-bedded facies D turbidite at this same locality.A third flow may have deposited turbidite of a different thickness. This process results in generation of noncyclic sequences near areas of the basin that are characterized by deposition of thick facies A, B, C, fining-upward sequences. Fining-upward sequences in interchannel areas, developed by overbank deposition 247 from a particular series of channels, grade laterally into noncyclic deposits as they interact with overbank deposits from another series of channels (figure 8 6 ). True "basin plain" deposition of noncyclic sequences may have oc curred in the western portion of the Cowichan River area. Since most sediment in this area came from the source areas well to the east, non cyclic sequences may have developed by the same processes ascribed to submarine-fans in which sediment is transported radially outward from a single source. Relationships Between Non-Marine, Marginal-Marine, and Submarine-Fan Environments The Cedar District and Decourcy formations in the Nanaimo River area, the Protection and Cedar District formations on Saturna Island, and the Extension Formation on Waldron and South Pender islands contain sedimentary features which suggest they were deposited in a transitional zone between non-marine or marginal-marine and submarine-fan environ ments. Along the Nanaimo River and nearby roadcuts, lenticular beds of cross-bedded sandstone and coal are interbedded with facies D noncyclic turbidites and mudstone (figure 87). Some poorly developed facies D fining-upward sequences are also present. Paleocurrent directions measured in these beds indicate transport to the east and are similar to directions measured in nearby nonmarine strata. Cross-bedded lenses are generally 0.5 to 1.5 meters thick and exhibit sharp contacts with underlying and overlying strata. These lenses thin rapidly along strike. Both trough and planar cross-bedding 248 are observed. Set heights range from 10 to 20 cm. Inclinations of 15 to 25 degrees are observed. Horizontal bedding and low angle (average 5 to 10° dip; hummocky?) trough cross-stratification are also observed within these sandstone beds. Low angle (hummocky?) cross-stratified sets range from 10 to 35 cm in height. Cross-stratified interbeds are uncommon, however, and most sandstone interbeds exhibit sedimentary structures typical of facies B submarine-fan sandstones. Pillow structures (figure 88 ) with a southeastward vergence are present in these beds as well. Sandstone interbeds are commonly characterized by abundant coaly materi al. Small coal seams 15 to 60 cm thick and 1 to 5 m in length are also present. Most "classic" turbidites in these units are facies D or E and exhibit T c(je and more rarely Tbcde anc* ^abcde bedding. Sand: shale ratios range from 1:1 to 1:4. The Decourcy Formation in the Nanaimo River area exhibits major changes in sedimentary structures along the west coast of Vancouver Island. Near Harmac, the Decourcy Formation is extensively cross-bedded and exhibits features typical of the non-marine sandstone facies. However at Yellow Point and Boat Harbor, cross-stratification is relatively rare and most sandstones are characterized by submarine-fan facies B sedimentary structures. A well defined stratification sequence in the Protection and Cedar District formations on Saturna Island suggests transition from marginal- marine to submarine-fan processes (figure 89). Trough cross-bedded sandstone units, with sets ranging in height from 9 to 20 cm are over- lain along an erosional contact by a lag-accumulation of shallow-water mollusk fragments. This unit is succeeded along a sharp depositional contact by a sandstone bed which contains lutite clasts at its base and Figure 87. Outcrop of facies D turbidites in the Cedar District Formation near the Nanaimo River on Vancouver Island. Note sandstone lens (circled). Photograph taken along roadcut 3 km from the river mouth. 251 :S?t Figure 8 8 . Sandstone bed in facies D turbidites shown in figure 87 which is characterized by a pillow structure. 252 exhibits horizontal to wavy bedding in its upper portion. This bed is in turn succeeded along a depositional contact by facies C, D fining- upward "classic" turbidites, which are then overlain by a matrix-sup ported conglomerate containing fragments of shallow-water bivalves. A sharp depositional contact separates the matrix-supported conglomerate from overlying facies D fining-upward sequences of "classic" turbidites. Some of these turbidites contain bivalve shell-fragments in their Bouma "B" divisions. The Extension Formation on South Pender Island is composed almost completely of facies A conglomerate. Most conglomerates exhibit a disorganized fabric however, units showing inverse- and normal-grading, and more rarely cross-stratification, are present. Sandstone interbeds in this formation commonly exhibit facies B sedimentary structures. Some interbeds, however, show well-developed cross-stratification, which grades upward into horizontal lamination. The Extension Formation at this locality is underlain by facies C and D turbidites of the Haslam Formation and overlain by siltstone-shale marginal-marine facies of the Pender Formation. Outcrops of the upper portion of the Extension Formation on Waldron Island consist dominantly of disorganized conglomerate. Some normal grading is also observed. Cross-stratified and horizontally-stratified units, however, are more common, and both a(p) a(i) and a(t) b(i) clast orientations are recognized at some localites. Thick conglomerate beds of the upper portion of the Extension Formation are underlain by sand stone-conglomerate marginal-marine facies in the lower portion of the Extension Formation and overlain by siltstone-shale marginal-marine facies of the Pender Formation. Paleocurrents in the marginal-marine 253 Figure 89. Detailed stratigraphic section of the Protection Formation and lowermost Cedar District Formation on Saturna Island. This section illustrates tran sition from marginal-marine facies to submarine-fan facies. The section >. s measured along the south coast of Saturna lelanU- 254 4 0 Fades C and faeiee D "classic.turbidites with sand store layers to 50 em* thick fineupward into Facies E and D turbidites with siltstone units 1 to 5 «*• thick. Fining-upward to non-cyclic sequences exhibiting dominantly T^e bedding and sandstone layers less than 10 cm. thick. Some thicker Tbede classic turbidites contain lnoceramus sp. s h e l l s i n t h e Bouma B d iv i s i o n * Matrix suoported conglomerate, no clast lineation or orientation* “Clasts include pebbles, gravel and cobbles, as w ell as abundant shallow-water bivalve fragments. Matrix is composed o'f* siltstone* Tabede’Tbcde. aT^ Tcde ^classic* turbidites. Medium-grained sandstone, horizontal to wavy bedding. Intraformational lutite clasts within featureless sandstone matrix. Lag-accumulation of shallow-water bivalves Trough cross-bedded sandstone, sets range in height from 4 to 12 cm. Interbedded quartz-ohyH ite conglomerate and horizontally stratified to low-angle planar cross-stratified s a n d s to n e . Q uartz-phyllite conglomerate meters 255 facies indicate progradation of material to the southeast. This is the same direction measured for marginal-marine facies on Patos, Sucia and Matia islands. A single paleocurrent direction measured within the mas sive conglomerate, however, has a northwest orientation. Interpretation of Transitional Sequences Facies B, C, and D submarine-fan deposits in the Cedar District Formation along the Nanaimo River indicate that sedimentation was controlled largely by sediment-gravity flow processes. Eastward paleocurrents, however, indicate that these flows were probably associated with nearby nonmarine deposition to the west. Abundant small coal seams may have resulted from downslope transport of organic material (i.e., accumulation of kelp; oral comm., Dott, 1978) along with clastic sediment. Rocks of the Cedar District Formation in this region resemble strata described by Hamblin and Walker (1979) in a transitional zone between turbidites of the Fernie Formation and nonmarine and marginal-marine rocks of the Kootenay Formation in the southern Canadian Rocky Moun tains. They state that cross-stratified sandstone lenses within sub marine-fan facies may be generated by lowering of wave-base during major storms, resulting in modification of sediment by nearshore processes. Sedimentary features of the Decourcy Formation along the east coast of Vancouver Island suggest shallowing of the Nanaimo Basin to the north. Cross-stratified units near Harmac of the Decourcy Formation are similar to nonmarine sandstone facies of the Extension Formation along the Nanaimo River. These sandstone facies may represent progradation of detritus into the Nanaimo Basin by fluvial and/or deltaic processes. However at Boat Harbor and Yellow Point, facies B sandstones are 256 abundant, whereas cross-stratified units are relatively uncommon. This suggests that sand was prograded into the basin in these areas largely by sediment-gravity flows. This sand may have been reworked by storm-wave processes, resulting in development of occasional cross-bedded units observed at Yellow Point and at Boat Harbor. The Cedar District near Boat Harbor was probably deposited in much deeper waters, however. Foraminifera sampled from the underlying Cedar District Formation near this locality indicate water depths of between 800 to 1000 m (Sliter, 1973). The Protection and Cedar District formations on Saturna Island record transgression during B^. rex Zone time. Cross-bedded sandstones, interbedded with lenticular units of conglomerate and lag-accumulations of shallow-water bivalves, suggest deposition within a marginal-marine environment. Sedimentary structures and depositional geometry of these rocks are similar to those of marginal-marine facies observed elsewhere in the Nanaimo Basin. Directly above this sequence is a sandstone which contains submarine-fan facies B structures. This sandstone is overlain by facies C and D "classic" turbidites interbedded with a matrix-sup- ported conglomerate. This conglomerate is interpreted as a debris flow which transported shallow-water clastic sediment and bivalve shells into deeper portions of the Nanaimo Basin. These units indicate a change in the dominant method of transportation from traction processes to sediment-gravity flow. Environmental interpretation of conglomerates of the Extension Formation on Waldron and South Pender islands is difficult. Sedimentary structures in these conglomerates reflect processes rather than envi ronments or water depth. According to Winn and Dott (1977), similar structures are observed in "deep-water" and fluvial conglomerates and differentiation between these two types is difficult. Environmental interpretation of the Extension Formation on Waldron Island as a non marine deposit is based largely on sedimentary structures within sand stone interbeds, abundance of cross-stratification, horizontal-stratifi- cation within conglomerate beds, and interbedding with underlying and overlying marginal-marine facies. Submarine-fan environments are inter preted for the Extension Formation on South Pender Island based largely on facies B structures in sandstone lenses and the abundance of normal ly- and inversely-graded beds. Cross-bedding, however, is abundant in the upper portions of this formation and the Extension Formation is overlain by marginal-marine facies of the Pender Formation. Additional ly, a channel-shaped sandstone bed in the upper portion of the Extension Formation on South Pender Island exhibits cross-stratified pebbly sand stone, grading upward to cross-stratified medium-grained sandstone. This sequence is similar to those observed in sandstone lenses in out crops of the nonmarine conglomerate facies along the Nanaimo River. I believe that, although the conglomerate on Waldron Island is largely nonmarine and much conglomerate on South Pender Island was probably deposited in deep-water, that a transition between submarine- fan and nonmarine conglomerate may exist at both localities. Part of the Extension Formation on South Pender Island, particularly the upper portion, may be nonmarine. Likewise, portions of the Extension conglom erates exposed along the southeast coast of Waldron Island may have been deposited in subaqueous conditions. PALEOGEOGRAPHY Stratigraphic patterns, depositional features, sandstone composi tion and sediment-dispersal directions can be used to reconstruct paleo- geography of the Nanaimo Basin during the Late Cretaceous. The Nanaimo Basin was partially bounded by and received sediment from source areas along its western, eastern, southeastern and southern margins throughout its evolution. The Coastal Plutonic Belt formed the eastern margin of the Nanaimo Basin. Plutonic debris dominates sandstone compositions in rocks of the Gulf Islands, particularly from H. vancouverense through P. suciaensis Zone time. P/F ratios for these rocks match P/F ratios observed in quartzdiorites and granodiorites of the Coastal Plutonic Belt. Sandstones which outcrop on Orcas, Clark and Barnes islands, however, contain abundant epidote and both volcanic and sedimentary rock-fragments. Southeastern paleocurrent measurements indicate that this detritus was probably derived from eugeosynclinal terranes of the North Cascades. Additionally, clasts of quartz-phyllite conglomerate which outcrops in the Protection Formation on Sucia and Saturna islands are identical to rock-types in the Darrington Phyllite, which outcrops in the western portion of the North Cascades. Sandstones and conglom erates deposited in the southern Nanaimo Basin are characterized by abundant chert, and both paleocurrent and compositional data suggest that they were derived from chert-rich terranes in the San Juan Islands. 259 Rocks in the Nanaimo River area are characterized by eastern paleocurrent measurements and compositional data which indicate derivation from nearby sources in the Insular Belt. Basalt-bearing lithic arenites and high-plagioclase arkoses can be correlated to sources in the Karmutsen Basalt and Island Intrusions, respectively. Deposition of dacitic debris from rocks of the Sicker and Bonanza Groups is also indicated by the presence of dacite-rich arkoses on Thetis and northern Saltspring islands and at Yellow Point on Vancouver Island. The presence of uplands along the basin margins is also indicated by stratification sequences and depositional features. In the Nanaimo River area, facies changes from west to east indicate gradual deepening of the basin and transition from non-marine to submarine-fan facies. Similar transitions from shallow to deep-water facies are observed in the Extension Formation on Waldron and South Pender islands and in the Protection and Cedar District formations on Saturna Island. Rocks in the central portion of the basin are dominantly composed of submarine- fan facies, with the exception of isolated occurrences of marginal- marine facies in the Comox Formation on Saltspring Island. Sediment was supplied by erosion of these highlands and transported into the basin by braided streams, which probably terminated as small, high-destructive deltas. Marginal-marine deposits along both the south eastern (Sucia, Matia, Patos, Waldron and Tumbo islands) and northwest ern (Nanaimo River area including Newcastle and Protection islands) sug gest sediment transport largely by littoral drift, with subordinate mod ification of structures by wave and tidal processes along narrow shelves. Paleocurrent measurements indicate that detritus was transpor ted southeast along southeastern and western margins of the basin and 260 west along a partial northern margin of the basin by longshore drift. This material was then resedimented into deeper portions of the basin where it was transported west and northwest by gravity-flow processes along a regional paleoslope (figure 90 & 91). Paleocurrent measurements suggest that the Cowichan River area was separated from the northeastern portion of the Nanaimo Basin by an up lifted horst composed of Paleozoic igneous and sedimentary rocks, which trends from Vancouver Island, immediately north of the Cowichan River area, southeast onto Saltspring Island (figure 1). This block was sub- aerially exposed and contributed sediment into the basin throughout early B. elongatum Zone time. Sediment was not deposited in significant quantities from this mid-basin high during later development of the Nanaimo Basin; however, it affected distribution of sediment throughout the evolution of the basin. Paleocurrents to the south of this block suggest progradation of sediment into the Cowichan River area and are generally oriented southwest to west. Paleocurrents northeast of this block are oriented northwest. These paleocurrent orientations exhibit a "V"-shaped pattern, suggesting contemporaneous sediment transport into both southern and northeastern portions of the basin. These data also suggest that this uplifted region to the north and another submarine high to the south of the Cowichan River area affected distribution of sediment in the southern Nanaimo Basin during B. elongatum to I_. schmidti Zone time. Paleocurrents in this area exhibit very little dispersion (figure 8 ), indicating that sediment transport was rigidly controlled by submarine topography. Paleocurrents, compositional data, and sedimentary patterns in rocks of the Comox Formation suggest derivation from local source areas Figure 90. Block diagram illustrating paleogeography of the Nanaimo Basin. Paleozoic and Early Mesozoic Rocks of Vancouver Island Coastal Plutonic Belt N> O' ro Figure 91. Interpretative paleogeographic map of the Nanaimo Basin illustrating approximate position of surrounding tectonic provinces and basin morphology. Positions of San Juan Islands and southern Gulf Islands are corrected for tectonic deformation as in figure 18. P on°°°X°. 8 > o-8b0“o ® o0, POnOPo0°o^°0oQ“o00P°0°0°d ?°j£?a<>o5>°o0 °I°°oi$&skks >5o'\0/°\p0g0oo 0V o « V ° o ° ° ° ° S„°Sc°?°°S. 2 o0*o#?°oP( O 0 0 o 0 0 0 0 o 0° © 0 t' v . 0 © oo o ° ° o 0 ° o ° o O ° 0 O ° 0 ° O ° o ° ° o © ° o « w < $°p°o°°<>: s m0o> V m o ° ©oJ©o0©o0Oo0©o0o©0oo0ooc©o0©o0©o0« 'OV00©0Oo00®00®00©C>0®00©0Oo0©o0Oo00©f’ °oo“2"oP o00 o00 Oo0 Oo0 ©o0©o0 ©o0 ©o0 «o°0 o0©o<>od^ 3oO °o © °o« °© O°o ° °o ° °o ° °o °°o 0°o © °0 o°o °* « a ° © ©°^ ©-o © o° ©„ © ©° o ©o© ©°© o&p«^o©0 o ° £ o ° O c © ? °e© o O°©©0 ©o o ©p©o° o ®o© o° O ©oo©° o - -.© ^ o©OfPo o°©0°Op© 0 0 0 -©^o©0o©o©°©o c 0 AS 7& & JS$$*giS$fo& k°o\°?0J^ P ^ ? o ° ^ j 3 ■ PLUTONIC C O M PL E X *® ^ O.O-n* V «• CnfwOflTiV X nO-O0/!* °oo°°o°? ©o« 0 ©Oq ©O so\so^st°o^o°°s£sisS°. a ©o °2o°Hg°:S°° ?-°0o0«°^o, °ikosSp:ifsP?skh oolo°oo° s i ? > o * ? b o°o°0°,0 »-°0°°°°- " \ . NORTH CASCADES - o' o o 0 0©o° oO O 0n° O {^ORO0 „ *©0 ©©*©O© 0°o°©© ©°«° Intrusions and/or Wark Diorite Gneiss) which are exposed nearby. Shortly after deposition of the Comox Formation, the uplifted block on Saltspring Island and on Vancouver Island probably subsided below wave-base. Marginal-marine and non-marine facies are not present in younger formations on Saltspring Island, in contrast to outcrops of the Comox Formation, and petrographic examination of these rocks suggests that they were derived from source rocks in the San Juan Islands and the Coastal Plutonic Belt. Additionally, petrographic data from Nanaimo rocks in the Cowichan River area indicate that they were derived largely from rocks of the San Juan Islands. There is no evidence of input of detrital sediment from sources to the north of the Cowichan River area. During much of j5. elongatum Zone time and into I_. schmidti Zone time, this area was covered by hemipelagic shales of the Haslam Formation. A subaqueous plateau may have existed north of the Cowichan River area during this time. The southern boundary of this plateau may have confined sediment in the Cowichan River area; and, since it was subaqueous or nearly subaqueous, contributed little or no coarse elastics into the basin. Hemipelagic shales of the Haslam Formation probably developed on top of this plateau. Quiet-water hemipelagic shales of the Haslam Formation in the Nanaimo River area were overlain by nonmarine conglomerates and coarse- to medium-grained sandstones of the Extension Formation. Paleocurrent 266 and compositional data indicate that these coarse elastics were derived from nearby sources on Vancouver Island. Abrupt regression may have occurred during the _I. schmidti-B. chicoensis Zone time interval in this area, resulting in subaerial exposure and then burial of this subaqueous plateau in the Nanaimo River area by non-marine sediments. Deposition of coarse elastics of the Extension Formation occurred throughout the upper B. elongatum to J3. chicoensis Zone time interval. At some localities, rocks of the Extension Formation represent proximal equivalents of "classic" turbidites and thick mudstones of the Haslam Formation which were deposited contemporaneously. At other localities, Extension rocks cut and fill channels in Haslam deposits formed during an earlier time interval. Petrographic data suggest that coarse-grained rocks of the Extension Formation were derived from Paleozoic and Early Mesozoic terranes of the San Juan Islands, the North Cascades, the Insular Belt, and the Coastal Plutonic Belt. Stratigraphic patterns of the Haslam and Extension formations indicate that this influx of coarsegrained material probably resulted from regional uplift along the basin margins. Sediments deposited during JB. chicoensis through early P. suciaensis Zone time indicate that a period of quiescence followed this tectonism. On Waldron and South Pender islands, the Pender Formation is characterized by siltstone-shale marginal-marine facies, and, in the Gulf Islands, it is comprised of fining-upward facied D turbidites and/or undifferentiated shale. Deposition of the Pender Formation, however, was at least partly coeval with deposition of the underlying Extension Formation and the overlying sandstone and subordinate conglomerates of the Protection Formation. In some areas of the Nanaimo 267 Basin, the Pender Formation may represent lower energy facies submarine-fan deposits in which sand and gravel deposition are represented by rocks of the underlying Extension or overlying Protection formations. Rocks on Saturna Island suggest that gradual transgression occurred from B. chicoensis to B. rex Zone time as marginal-marine facies of the lower Protection Formation were replaced by submarine-fan deposits of the uppermost Protection and Cedar District formations. There are no major changes in basin geometry, however, during this time interval. The dominant source of sediment over much of the basin during this time was the Coastal Plutonic Belt, with subordinate input from rocks of the North Cascades, the Insular Belt, and the San Juan Islands. Close examination of Nanaimo strata suggests that the basin was not bounded continuously along its southern or western margins, but instead it was partially bounded by a series of large island highs. Some of these island highs were subaerially exposed for only a short period during initial development of the Nanaimo Basin, whereas others supplied sediment into the basin throughout the deposition of Nanaimo rocks. During initial development, detritus was supplied into the basin from local uplifts of Wrengellian rocks to the north and south of the Cowichan River area. These regions subsided below wave-base shortly after deposition of the Comox Formation. However, they continued to control sedimentation in the Nanaimo Basin throughout its development. The Nanaimo River area, along with much of Wrengellian strata of northern and central Vancouver Island, was probably subaerially exposed for much of the development of the Nanaimo Basin. Muller and Jeletzky (1970) report that the Comox Basin outcrops on Vancouver Island are dominated by non-marine and marginal-marine sedimentation and coal seams are well-developed in this area, as in the Nanaimo River area. Paleocurrent measurements in this region indicate progradation of sediment eastward from sources in Wrengellian strata towards deeper portions of the basin. Paleocurrent measurements on Newcastle Island suggest that the Nanaimo Basin was partially bounded to the north along the Nanoose Ridge, a pre-Cretaceous high which separates the Nanaimo and the Comox basins (Usher, 1951). Sediment dispersal directions measured in marginal-marine strata on this island indicate transport to the west (figure 8 ) in contrast to directions measured in non-marine strata which suggest southeastern progradation of sediment. These paleocurrent measurements indicate that sediment derived from sources to the northwest was reworked by longshore currents and prograded parallel to the coastline. These two basins, however, were probably at least partially connected to one another. Northwest paleocurrents in submarine-fan strata of the Cedar District Formation on Thetis Island, which is in close proximity to the Nanoose Ridge, suggest that the regional slope which controlled sediment transport in the Nanaimo Basin was not affected by shallowing to the north in portions of the basin east of Newcastle and Protection islands. Northwest paleocurrents are also observed in possibly coeval strata of the Cedar District Formation on Denman and Hornby Islands in the Comox Basin (figure 1). These strata consist largely of shale and contrast with well-developed facies B, C and D turbidites on Thetis Island. They may represent distal equivalents of the coarser-grained rocks to the south. The San Juan Island Terranes may have formed a series of island highs or a single high that partially bounded the basin to the south. Subaerial exposure of the San Juan Island Terranes during the early development of the Nanaimo Basin is indicated by major sediment contri butions during deposition of the Haslam, Extension and Pender formations in the southern portion of the Nanaimo Basin. Some input of sediment from these terranes is also noted in rocks of the Protection Formation, and minor deposition from the San Juan Island Terranes probably occurred throughout development of the Nanaimo Basin. TECTONIC IMPLICATIONS The Late Cretaceous tectonic history of the northwest Pacific re gion of the United States and the southern Cordillera of Canada is com plex and still poorly understood. Interpretations of plate motion dur ing this time interval is complicated by the presence of a "quiet zone" in geomagnetic lineations of the Pacific Ocean. Determination of the tectonic setting of the Nanaimo Basin is important in reconstructing the geologic history of this area and determining the nature of plate inter action between the North American, Kula and Farallon Plates during the Late Cretaceous. The Georgia Basin, which includes the Nanaimo and Comox basins, has been described as a fore-arc basin by Dickinson (1976) and Muller (1977a). However, Davis and others (1978) present the hypothesis that subduction may have ceased during the Late Cretaceous and that a trans form boundary may have existed between the "Kula?" and "North American" plates. Two hypotheses concerning development of the Nanaimo Basin are presented in this paper: (1) that the Nanaimo Basin is a "pull-apart" basin or down-faulted graben developed along a Late Cretaceous transform margin, or (2) that the Nanaimo Basin is an "intra-massif" fore-arc basin (defined by Dickinson and Seely, 1979). The Cretaceous and Tertiary structure on Vancouver Island, discuss ed in the geologic setting, consists largely of tilted fault blocks (Muller and Jeletzky, 1970) forming horsts and grabens (figure 1). 270 271 Faults are steeply dipping and well-defined anticlines, and synclines are rare. Muller and Jeletsky (1970) state that the structural nature of Vancouver Island reflects horizontal tension and vertical crustal movement as opposed to compression. Geologic mapping by Muller (1977b) and Sutherland-Brown (1966) suggests that some faults on Vancouver Island have a right-lateral component of movement as well. A horst, developed between deposits of the Cowichan River area and the northeastern Nanaimo Basin, affected sediment dispersal directions in the basin throughout its evolution. The Cowichan River area is a graben bounded by normal faults. This graben probably existed during the Late Cretaceous, as paleocurrents in this area parallel the trend of these normal faults with very little dispersion. The horst and graben structure of the Nanaimo Basin is very similar to the structural style of pull-apart basins along the San Andreas (Crowell, 1974a, 1974b) and proto-San Andreas (Nilsen and Clarke, 1975; Nilsen, 1978) faults. The Nanaimo Basin was bounded by uplands along its eastern margin and partially bounded by uplands along its western, southern and north ern margins. Late Cretaceous downwarping or downfaulting of the Nanaimo Basin (Sutherland-Brown, 1966) is associated with uplift of portions of Vancouver Island (Muller and Jeletzky, 1970). Fault patterns similar to those on Vancouver Island occur elsewhere in the Insular Belt. According to Sutherland-Brown (1966), major faults in the Queen Charlotte Islands, active since the Early Cretaceous, com bine normal "east-block-down" displacement with right-lateral trans current motion. Sutherland-Brown (1968) states that 26 to 93 km of right-lateral transcurrent movement occurred along the Rennell-Louscone Fault Zone and additionally, that substantial transcurrent movement 272 also occurred along the Sandspit Fault (figure 92). He further states that these faults influenced deposition of the Early Cretaceous Longarm Formation and the Early to Late Cretaceous Queen Charlotte Group, which may be in part, correlative with the Nanaimo Group. The Longarm Formation in the Queen Charlotte Islands was deposited in a "narrow graben-like trough” (pull-apart basin?) developed within the Renell-Louscone Fault Zone. Deposits of the Queen Charlotte Group are bounded by the Rennel-Louscone Fault Zone to the west and the Sandspit Fault to the east. Sutherland-Brown (1968) notes that uplifted blocks within the Rennell-Louscone Fault Zone supplied sediment to this group. Right-lateral transcurrent faulting is also very well-documented for the Upper Cretaceous in the Intermontane Belt of Canada and the North Cascades. Much of the transcurrent faulting was initiated during the Jurassic to the Late Cretaceous and continued into the Early Terti ary (Davis et al., 1978). Gabrielse and others (1977) and Gabrielse and Dodds (1977) suggest that 450 to 500 km of right-lateral displacement is necessary to explain offset of geologic terranes in north-central British Columbia. This estimate agrees with work by Tempelmann-Kluit and others (1976) who report 450 km of right-lateral displacement in the Tintina Fault Zone (figure 92) during the Late Cretaceous to Eocene. This displacement postdates the Mid-Cretaceous pulse of plutonic emplacement (Gabrielse and Dodds, 1977; Tempelmann-Kluit and others, 1976). In southern and central British Columbia, substantial right-lateral displacement has been recognized along the Fraser-Yalakom Fault Zone (figure 92) (Tipper, 1969). Movement along this fault zone probably began during the Jurassic to Late Cretaceous. Tipper (1969) 273 Figure 92. Tectonic map of the west coast of northern Washington and southern BritishColumbia illustrating major faults and rock-types. ??k Queen Charlotte Is C i ~i\i~ O TwV'A Sandspit Fault C oastal Rennell Vy t X I Louscone '■ V'lV'lv Plutonic Belt Fault-Zone Pacific Ocean Vancou/er I Nanaimo Group Queen Charlotte Group Wrengellian Rocks North Cascades f'Vi\ Plutonic Rocks Terranes of the San Juan Islands includes some of the Nanaimo Gr 275 estimates that 80 to 192 km of right-lateral displacement occurred along the Yalakom Fault Zone. The Fraser Fault Zone extends southward into the Straight Creek Fault Zone of the North Cascades (figure 92). Estimates of right-lat eral movement within the Straight Creek Fault Zone range from 190 km (Misch, 1977) to 160 km (Anderson, 1977), to 120 km (Okulitch et al., 1977). The time of this displacement is not well established. Okulitch and others (1977) state that movement ceased before intrusion of the Spuzzum Pluton across it (84 m.y. ago), whereas Mattison (1972) suggests that major movement along this fault occurred during the Early Tertiary. Davis and others (1978) state that Early Cretaceous episodes of movement along the Sraight Creek Fault may be related to northward emplacement of "Cascadia" along the ancestral Ross Lake Fault Zone. Right-lateral transcurrent faulting in the Canadian Cordillera coincides with right-lateral faulting along the west coast of California during the Late Cretaceous. Nilsen and Clarke (1975) note that 220 to 420 km of right-lateral strike-slip motion occurred along the "proto-San Andreas Fault." Nelsen and Clarke (1975) and Nilsen (1978) note that pull-apart basins are well-developed along this fault. The orientation of the "proto-San Andreas Fault" (as drawn by Nilsen, 1978) parallels the orientation of major faults on Vancouver Island. Rocks of Late Jurassic to Early Cretaceous age on Vancouver Island suggest that convergence between the North American Plate and the Kula? Plateau was occurring at this time. The Pacific Rim Complex, a Jurassic to Early Cretaceous assemblage of greywacke, argillite, chert, and greenstone, outcrops along portions of the west coast of Vancouver Island. This assemblage exhibits a chaotic, melange-like structure and 276 probably was developed along an ancient trench (Muller, 1977). Deposits of the Longarm Formation and Queen Charlotte Group on Vancouver Island may represent a coeval fore-arc sequence (Dickinson 1976; Muller, 1977). Convergence along the west coast of Washington during this time interval may be indicated by Late Jurassic to Early Cretaceous fore-arc deposits of the Decatur Terrane and coeval trench deposits of the Lopez Terrane in the San Juan Islands (Whetten et al., 1978). In contrast, there are no rocks which indicate development of a trench in this area during the Late Cretaceous. Additionally, Nanaimo rocks do not contain contemporaneous volcanic rock-fragments typical of many fore-arc basins (Dickinson, 1971, 1974a, 1974b; Dickinson and Suczek, 1978). Dickinson (1971) states that a key indicator of a fore-arc basin is deposition of sedimentary strata of a volcanic-plutonic provenance concurrently with magmatism in an associated arc. However, there is no evidence of any concurrent volcanism in the southwestern Coastal Plutonic Belt during deposition of the Nanaimo Group. This contrasts with Early to Mid-Cretaceous time during which volcanics of the Gambier Group were erupted. A lull in plutonic emplacement also occurred during deposition of the Nanaimo Group following a major plutonic pulse between 80 and 110 m.y. ago. This magmatic hiatus persisted into the Paleocene, during which another plutonic pulse was initiated (Roddick et al., 1977; Armstrong and others, 1977; Armstrong, oral comm., 1978). This "magmatic gap” coincides with a Campanian to Paleocene hiatus in magmatic development in California discussed by Nilsen (1978) during development of the "proto-San Andreas" Fault. 277 Uplifts and depressions are commonly formed within transcurrent fault zones as a result of braiding and anastomosing of individual faults within a broad fault zone. Crowell (1974a) states that the San Andreas Transform is defined by a fault zone that is over 200 km wide in some places. The geometry of faulting on Vancouver Island (figure 1) is similar to that along the San Andreas Transform. Pull-apart basins, developed in the San Andreas Transform, are commonly grabens and half- grabens and may occur as elongate depressed blocks within the anastomos ing fault zone or aligned at high-angles to major faults (Crowell, 1974a, 1974b). This type of orientation is also observed in grabens on Vancouver Island (Muller, 1977b). Deposition in the Nanaimo Basin was at least partially controlled by normal faulting. These data suggest that development of the Nanaimo Basin may have been controlled by extensional and transcurrent motion, as opposed to convergent motion generally associated with fore-arc development. A magmatic gap, the lack of trench deposits, fault geometry on Vancouver and Queen Charlotte islands, and large-scale, right-lateral transcurrent motion may indicate that subduction actually ceased during the Late Cretaceous and a transform boundary existed between the North American Plate and the Kula? Plate during this time period. If this "proto-Queen Charlotte Fault" was located along the west coast of Vancouver Island (along a plate boundary drawn by Davis and others, 1978), renewed subduction during the Paleocene would have erased any trace of it. This subduction is suggested by Paleocene igneous activity in the Coastal Plutonic Belt. Northeastward migration of the Kula-Farallon-Pacific Plate triple junction during the Late Mesozoic and Early Cenozic has been demonstrat 278 ed by Byrne (1979) and Hilde and others (1976). This movement may have resulted in an increased component of right-lateral movement of the Kula? Plate relative to the North American Plate during the Late Cretaceous. The Nanaimo Basin may also have developed as an intra-massif fore arc basin along a convergent margin. This type of basin develops within the portion of the plate-margin characterized by rocks of the arc-massif or pre-arc basement. Fore-arc strata are deposited unconformably on these rocks within a basin commonly bounded by normal faults. These normal faults may be related to surficial extensions above rising plu- tons or magmatic withdrawal beneath the arc terrane (Dickinson and Seely, 1979). These authors also state that, in regions characterized by oblique subduction, intra-massif fore-arc basins may be bounded by faults which show a strike-slip component. Nanaimo rocks rest unconformably on rocks of Wrengellia which com prise the pre-arc basement and the Island Intrusions and Bonanza Group. These rocks probably represent pre-Cretaceous arc development. During the Early to Mid-Cretaceous, this arc migrated east to form the Coastal Plutonic Belt. Thus the Nanaimo Group rests on and between rocks of the arc-massif. None of the evidence presented conclusively proves that subduction actually ceased during the Late Cretaceous along the southern Canadian Cordillera. Large-scale right-lateral transcurrent motion and the fault patterns observed on Vancouver and Queen Charlotte islands may have de veloped as a result of oblique subduction. More data are necessary before one or the other of these hypotheses can be completely substantiated. They are presented to define ques tions, rather than to supply answers. This study, however, suggests that the development of the Nanaimo Basin may record major changes in tectonic framework during the Late Cretaceous. Documentation and under standing of these changes should contribute greatly to our understanding of the geologic history of the Canadian Cordillera. This period repre sents a time of readjustment along the western coast of Canada following the arrival of the Wrengellian Terrane. Additionally, major changes in the nature of motion of the Kula, Farallon and Pacific plates may have occurred during this time (Atwater, 1970; Hilde et al., 1976; Byrne, 1979). Detailed studies of sedimentary basins, such as the Nanaimo Basin, are an important portion of the data necessary to delineate plate interaction along the western coast of Canada, especially during the Paleozoic and Mesozoic eras, in which paleomagnetic evidence of oceanic plate motion is absent or poorly defined. CONCLUSIONS 1) Sandstones and conglomerates in the Nanaimo Basin have been assign ed to five petrofacies which can be delineated chronologically and geo graphically. These include: (1) High plagioclase arkose: This petrofacies has been divided on the basis of paleocurrent data into two subpetrofacies. The first is characterized by Coastal Plutonic Belt source and the second is characterized by input of detritus from the Middle Jurassic Island Intrusions. (2) Chert-rich lithic arenite: Detritus in this petro facies was derived largely from Paleozoic and Early Mesozoic terranes of the San Juan Islands with subor dinate input from rocks of the North Cascades. (3) Lithic arkose: Rocks of this petrofacies are composed of material from rocks of the Coastal Plutonic Belt, the North Cascades and the terranes of the San Juan Islands. (4) Dacite-rich arkose: Rocks of this petrofacies are made up of detritus from the Coastal Plutonic Belt and the Middle Jurassic Island Intrusions, the Sicker Group, and the Bonanza Group of Vancouver Island. (5) Basalt-bearing lithic arenite: This petrofacies is composed of detritus from Early Mesozoic and Paleozoic . rocks of Vancouver Island. Major input from the Karmutsen Basalt is noted. Sedimentary structures, stratification sequences and facies patterns in rocks of the Nanimo Group, deposited in the Nanaimo Basin suggest that they were deposited in nonmarine, marginal marine and submarine-fan environments. Sandstones and some conglomerates deposited in nonmarine environments of the Nanaimo Basin are characterized by medium- to large-scale cross-bedding, ripple marks and ripple 280 281 cross-lamination, and horizontal bedding. Subordinate siltstone, shale and coal beds are also present and strata define fining-upward se quences. Sandstones and conglomerates deposited in marginal marine environments exhibit similar structures and rock types; however, they are also characterized by lag accumulations of shelly material oscilla tory ripple marks and cross-lamination, herringbone cross-bedding, and flaser bedding. Stratification sequences are similar to those observed along modern barred high energy beaches. Sandstones deposited in sub marine-fan environments of the Nanaimo Groups are commonly structureless or show wavy- to horizontal-bedding, dish structures and features indic ative of soft-sediment deformation. Some sandstones exhibit normal- grading. Most conglomerates are disorganized, normally graded, or in versely graded. Interbedded sandstone-siltstone, sandstone-shale and siltstone-shale units, which exhibit Bouma sequence bedding, interfinger with these conglomerates and sandstones. 3) Nonmarine and marginal marine rocks of the Nanaimo Group outcrop along the northwestern and southeastern margins of the Nanaimo Basin Paleocurrent measurements made in nonmarine strata in the northwestern portion of the basin suggest transport to the east, perpendicular to the basin axis. Paleocurrent measurements made in marginal-marine rocks however, indicate transport to the south and southeast, parallel to the basin margins. This suggests sediment movement by longshore drift. Most of the Nanaimo Basin is characterized by submarine-fan deposits. Paleocurrents in these rocks indicate that detritus was transported longitudinally along basin axes. Sediment transport directions in sub marine-fan strata in the southern portion of the Nanaimo Basin, inclu ding the rocks which outcrop in the Cowichan River drainage area, are 282 dominantly west and southwest whereas directions in the northeastern portion of the basin are largely northwest. Additionally, rocks interpreted as shallow water strata surround a block of Wrengellian strata. Paleocurrents in these shallow water rocks are arranged in a radial pattern. These data suggest that an uplifted region divided the Nanaimo Basin into two "sub-basins" during its development. 4) The Nanaimo Basin is a restricted basin (term from Nelson and Nilson, 1974) in which detritus from several source areas was transported longitudinally along basin axes by coalescing submarine-fans. 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Chile: Sedimentology, v. 26, p. 203-228. 298 LIST OF ABBREVIATIONS USED IN APPENDICES Sample Location Names B — Barnes Island BB - Booth Bay - Saltspring Island C - Cusheon Creek - Saltspring Island Cl - Clark Island COW - Cowichan River area - Vancouver Island D - Dinner Bay - Mayne Island GH - Ganges Harbor - Saltspring Island H - Horton Bay - Mayne Island HI - Roadcut 1-3 miles south of town of Nanaimo M - Mouat Point- North Pender Island MA - Matia Island NAN - Outcrop in downtown Nanaimo NE - Newcastle Island NH - Roadcut 1-3 miles south of town of Nanaimo NR - Nanaimo River cut - Vancouver Island 0 - Orcas Island P - Bedwell Harber - North Pender Island PA - Patos Island S - Southey Point - Saltspring Island SK - Skipjack Island 299 Sample Location Names (con't.) SP - South Pender Island ST - Saturna Island SU - Sucia Island WA - Waldron Island U - Sucia Island Y - Yellow Point - Vancouver Island Mineral and Lithic Type Abbreviations SAM = sample QTZ = quartz PQTZ = polycrystalline quartz-crystal units larger than very fine-grained sandstone CHT = chert-crystal units smaller than very fine-grained sandstone PLAG = plagioclase KSPAR = Appendix I - orthoclase + microcline Appendix II - orthoclase + microcline + sanidine SAN sanidine EPID = epidote AMPH = amphibole BIOT = biotite MU muscovite OP = opaque minerals SPH = sphene BAS = basalt Mineral and Lithic Type Abbreviations (con' ABAS = basaltic andesite AND = andesite ANDD = andesitic dacite DAC = dacite + rhyolite TUF = pyroclastic fragments UNV = unknown volcanic rock-fragments PRF = plutonic rock-fragment MRF = metamorphic rock-fragment SRF = sedimentary rock fragment UMIN = unknown mineral URF = unknown rock-fragment CALC = calcite cement CHL = chlorite PHSL = phyllosilicate cement MAT = alteration matrix ZEO = zeolite cement SIL d= silica cement 301 APPENDIX I SAM QT2 PQTZ CHT PUGKSPAR SAN EPID AM PH BIOT MU OPSPHBAS ABAS AND ANDD OACTUF UNV PRF MRF SRF UMIN URF CALC CHL PHYL MATZEOSIL PA1 24. 2. 4. 30. 7. 0. 2. 2. 2. 0. 1. 0. 1. 0. 2. 0. 2. 0. 0. 1. 1. 2. 0. 0. 0. 2. 0. 5. 9. 0. PA3 23. 4. 5. 26. 7. 0. 3. 0. 4. 0. 0. 0. 3. 0. 5. 0. 4. 0. 0. 2. 1. 3. 0. 0. 0. 2. 0. 4. 1. 0. PA4 20. 4. 11. 12. 2. 0. 3. 2. 1. 0. 1. 0. 1. 1. 2. 0. 4. 0. 0. 2. 2. 6. 2. 0. 25. 0. 0. 0. 1. 0. MAI 27. 10. 7. 26. 4. 0. 1. 0. 2. 0. 0. 0. 2. 1. 0. 0. 4. 0. 0. 0. 5. 6. 0. 0. 0. 0. 1. 1. 0. 0. MA4 26. 5. 4. 26. 5. 0. 2. 0. 4. 0. 0. 1. 0. 0. 1. 0. 2. 0. 0. 3. 9. 3. 0. 0. 0. 3. 1. 4. 1. 0. U3 9. 1. 2. 12. 0. 0. 8. 6. 1. 0. 2. 0. 3. 0. 0. 0. 1. 0. 0. 1. 3. 5. 1. 1. 42. 3. 0. 1. 0. 0. 04 15. 3. 3. 29. 7. 0. 5. 12. 1. 0. 2. 0. 2. 0. 2. 0. 0. 0. 0. 2. 4. 1. 0. 0. 0. 0. 0. 6. 5. 0. SU8 24. 2. 7. 29. 8. 0. 1. 1. 4. 0. 0. 0. 1. 2. 2. 2. 4. 0. 0. 0. 0. 6. 0. 0. 6. 0. 1. 2 . 0. 0. sun 28. 2. 4. 21. 4. 0. 0. 0. 1. 0. 0. 0. 3. 2. 1. 1. 4. 0. 0. 1. 1. 6. 0. 0. 15. 0. 0. 2. 1. 0. SU14 30. 4. 5. 27. 5. 0. 0. 1. 0. 0. 1. 0. 1. 2. 0. 0. 4. 0. 0. 3. 2. 2. 0. 0. 5. 0. 0. 5. 0. 0. SU19 34. 5. 3. 21. 5. 0. 1. 0. 1. 0. 0. 0. 1. 2. 0. 0. 2. 1. 0. 2. 2. 1. 0. 0. 15. 0. 0. 1. 2. 0. SU22 22. 3. 5. 19. 6. 1. 2. 2. 1. 0. 0. 0. 3. 1. 1. 1. 3. 0. 1. 1. 3. 3. 0. 0. 23. 0. 0. 0. 0. 0. SU25. 25. 4. 5. 16. 5. 0. 1. 1. 0. 0. 0. 0. 1. 1. 2. 0. 7. 1. 0. 2. 3. 2. 0. 0. 20. 0. 0. 0. 2. 0. 302 SU27 16. 2. 4. 20. 3. 2. 1. 0. 0. 0. 0. 0. 0. 5. 3. 0. 3. 0. 2. 3. 6. 3. 1. 1. 20. 0. 0. 1. 5. 0. SU34 22. 1. 7. 23. 7. 0. 1. 0. 1. 0. 0. 0. 0. 1. 1. 2. 3. 0. 1. 2. 7. 3. 0. 0. 16. 0. 0. 0. 2. 0. SU39 23. 4. 13. 18. 4. 0. 0. 0. 1. 0. 0. 0. 0. 2. 1. 1. 3. 0. 1. 1. 6. 2. 0. 0. 17. 1. 0. 1. 2. 0. SU41 26. 3. 7. 20. 7. 0. 1. 0. 5. 0. 0. 0. 1. 3. 2. 0. 4. 0. 0. 2. 5. 8. 1. 0. 0. 1. 3. 3. 0. 0. S I M 24. 3. 6. 13. 5. 0. 2. 2. 0. 0. 0. 0. 0. 1. 3. 1. 7. 2. 1. 2. 3. 4. 0. 0. 21. 0. 0. 0. 1. 0. SU45 25. 3. 4. 18. 5. 0. 1. 2. 1. 0. 0. 0. 0. 1. 1. 2. 5. 1. 2. 3. 2. 2. 0. 0. 16. 0. 0. 0. 5. 0. SU48 30. 4. 3. 15. 4. 0. 6. 4. 1. 0. 1. 0. 0. 0. 1. 1. 2. 1. 1. 2. 3. 1. 0. 0. 18. 1. 0. 0. 1. 0. SU52 13. 3. 3. 11. 1. 0. 14. 3. 0. 0. 4. 0. 0. 0. 1. 1. 3. 0. 3. 0. 1. 3. 4. 1. 1. 14. 7. 6. 0. 0. SU57 14. 2. 4. 18. 0. 0. 9. 3. 1. 0. 1. 0. 0. 1. 0. 1. 0. 0. 0. 0. 3. 6. 0. 0. 19. 7. 5. 6. 0. 0. ST7 28. 3. 1. 8. 1. 0. 0. 0. 1. 0. 2. 0. 0. 0. 1. 0. 0. 0. 0. 0. 12. 0. 1. 0. 35. 3. 2. 0. 0. 0. ST6 39. 7. 2. 13. 2. 0. 0. 0. 3. 2. 0. 0. 0. 0. 0. 0. 0. 0. 0. 1. 4. 6. 0. 0. 15. 0. 3. 2. 2. 0. SP23 14. 0. 1. 20. 0. 0. 13. 4. 0. 0. 3. 0. 1. 1. 0. 0. 0. 0. 3. 0. 1. 3. 0. 1. 1. 10. 4. 15. 3. 0. SP27 32. 4. 1. 19. 10. 0. 0. 0. 5. 4. 1. 1. 1. 1. 1. 0. 1. 0. 0. 2. 5. 0. 0. 0. 0. 5. 1. 3. 5. 0. SP30 34. 5. 1. 24. 9. 0. 0. 0. 2. 0. 1. 1. 0. 1. 2- 0. 1. 0. 0. 4. 2. 1. 0. 0. 0. 4. 1. 5. 2. 0. 303 SP41 29. 4. 3. 26. 11. 0. 0. 0. 2. 4. 0. 0. 0. 0. 0. 0. 0. 0. 0. 1. 1. 1. 0. 0. 3. 1. 5. 3. 6. 0. SP44 36. 2. 2. 23. 5. 0. 1. 0. 3. 0. 0. 0. 0. 1. 0. 0. 0. 0. 2. 1. 1. 2. 0. 0. 0. 8. 2. 6. 4. 0. SP49 30. 3. 1. 16. 2. 0. 2. 0. 6. 0. 5. 0. 0. 1. 0. 0. 2. 0. 2. 1. 1. 3. 0. 0. 0. 13. 5. 6. 0. 0. SP52 27. 2. 5. 24. 8. 0. 0. 0. 4. 1. 0. 0. 0. 1. 0. 0. 1. 0. 1. 1. 2. 4. 0. 0. 0. 2. 4. 12. 2. 0. SP55 29. 8. 18. 17. 5. 0. 0. 0. 2. 0. 0. 0. 1. 2. 1. 0. 1. 0. 0. 2. 2. 9. 0. 0. 0. 0. 1. 1. 0. 0. SP64 30. 4. 3. 24. 8. 0. 0. 0. 5. 0. 0. 0. 0. 1. 0. 1. 0. 1. 3. 1. 2. 0. 0. 0. 2. 6. 2. 0. SP67 29. 4. 4. 19. 7. 0. 0. 0. 3. 0. 0. 0. 1. 1. 0. 1. 2. 2. 1. 3. 2. 0. 0. 1. 5. 5. 2. 0. SP75 34. 3. 3. 28. 9. 0. 0. 0. 5. 1. 0. 0. 0. 1. 0. 1. 0. 0. 3. 4. 1. 0. 0. 0. 1. 0. 3. 0. C15 33. 5. 1. 35. 5. 0. 2. 0. 3. 0. 3. 0. 0. 0. 0. 0. 0. 0. 0. 1. 1. 1. 0. 0. 2. 4. 0. 4. 0. 0. Cl 7 8. 0. 0. 5. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 48. 0. 24. 12. C19 36 1. 1. 31. 14. 0. 2. 0. 3. 2. 0. 0. 0. 0. 0. 0. 0. 0. 1. 0. 1. 0. 0. 0. 0. 1. 1. 0. 6. 0. Ml 9 37. 4. 1. 31. 10. 0. 1. 0. 5. 0. 0. 0. 0. 0. 0. 0. 1. 0. 0. 1. 0. 1. 0. 0. 0. 1. 2. 1. 1. 0. M23 25. 0. 2. 41. 7. 3. 1. 0. 6. 2. 1. 0. 2. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 3. 0. 3. 4. 0. M33 24. 2. 5. 24. 13. 2. 1. 1. 6. 1. 0. 1. 0. 0. 2. 0. 2. 0. 0. 1. 1. 1. 0. 0. 0. 3. 0. 5. 4. 0. 304 ge meg m - r4ri eg r-4 r-4 r-i r-4 m g e m eg eg mcgcgegmegmegcgegi- e g o m o eg© o o o o o o o o o o © © o o o o o o o o o O o f O O eg© o o O o m m O eg O o O O *HO O O O O i— O O e gmo (eg O O o o o o o O O O O O O O O M C O O O O O O O O O mn r menn n O O O n e O o n © © © O i-4 © o o O N o o O O O © O © go mo mo e to ego o mo n n o m o o g e in o d © m 4 *o o o mo mo o m o m o © o' o <* o © v o © vo o o v o -4 *© cno ego v g 'e r- r O' eg m m m o vo eg o g e o n c p* © ?-4 r-4 -4 ^ o go r eg O o N o m o egm 1-1 o r 4 »4 jm mm v g - r4r4 o eg vo m s r r-4r-4 r-4 vo eg m m aj m »-4 o r-4 CO ?— 4 vo r o OO r- N P - 4 . -4 r- - o o © o © o o © o m -4 4 o r -r- 4 4r-r- O 4 4i— © 4 ri— - OO 4 4 © 3 ocg o g -»i h on h n r- »—i m o on eg g c o * i - f g e m g c m g c - o r O O O O r-io 1 *» eg r o*-» o o o o o o o o o o o » * r on X P- - r- r-4 oooooooooo o o o mcMmoomocM o cm o OOOOOO tHOOO cMOOO CM O O O *H o r-o O O O O O O CM o N O CM O rH O *-MO H O O O O f-t O H O O O CM O O Off' O *—I *H CM O H CM rH CO CM CT> O CM OrH CM < J\ O rH mm Om H N rHO O *4 r-f sO ! 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T12 32. 1. 3. 22. 5. 0. 0. 0. 1. 0. 1. 0. 0. 2. 2. 2 3. 1. 0. 0. 0. 4. 0. 0. 2. 2. 6. 7. 0. 0. 307 308 O 00 o o CM O © CM CM CM © CM O CM O ©OCMr-OmCMCMO CM 'O Mj* f-4 O O O S0 CM OO OO OO OO OO OO OO 1-40 1-40 OO OO f-4 O f-4 o oo O O i—4 o O CM o CM OO OO OO OO OO OO OO OO OO «-4 o O f-l CO CM r- CM O' 1-4 r-» r-4 O' CM CD O r-4 r-4 O i-lr-4 r-4 CO O f-4 CM CM O CO CM CO o f-4 O CM 1 -4 0 O m}- © tO O CM © f-4 O CM O O f-4 O N O CM O O oo -4 m oo m m c m m m m i-j O' <—i f-4 c m c m mcM i-4 m c m c m c m f-4 0*0 OO OO OO OO OO OO o m O CM O O O O O GO o o o o m CM »-4 O O f-4 O O O O O O r-4 O O O r-4 O O O CM O O f-4 O O O 1-4 o O O CM o O O CM O r-4 o O O Or-4 O O O 1-4 <}■ f-4 oo oo oo oo O 'm i-4 c m coo «o- mm m v d n n ci m c m m c m v o h ^ m m m cM i- h O'* f-4 CO CM CO CM m *-4 i-4 O O v O O 0 0 r 4 O' r-4 O' O lA r-4 O' r-4 CM ^ i—I CMCMr-4CMCMCMCMCMf-4i-imr-4CMCM m o i—4 cm vo cm m cm cm m r-4 r-» cm mcM m cm f-4 m m o cm h r-4 m o 1 -4 0 cMf-4mt-4mcMmmr-4CMmmcMCMm o voo f-( o O' o cm o r-.© mo r-4© r» o cm o o o soo r-» o on o cMOCMvor*»mmcMOOcMCM'©Mt -Mmr>.c0f-«i-4CMCMCMCMmmmMfm cMmocMMfcommr*«m Hcnc/)C/)CAC/)C/)CAC/3COCOC/3CAc/3 S47 21. 1. 5. 26. 0. 0. 0. 0. 1. 1. 0. 3. 0. 0. 0. 6. 0. 0. 1. 3. 2. 0. 0. 3. 0. 11. 1. 0. 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NR6 25. 9. 15. 18. 1. 0. 0. 0. 2. 0. 0. 0. 6. 0. 0. 1. 2. 0. 0. 1. 1. 11. 0. 0. 0. 1. 1. 6. 0. 0. j r o OO i—4 O O sj o O rO 14 O O O O O O O 00 CMO' O CT» r-4 O O 0*1COO OO O H O CM 1-4i-4 O UOO 1-4 O O O O CO O CO 1-4 O O O O V O O O O 1-40 OO OO OO OO mo mo OO OO OO OO 1-40 O VOO O C C O MC C r4 O O O O O O O O r-4 O O O CM O CMCn O O O O O O CMCO CM O O O — C o O' M VO CM ' O CO o CO i—4 O O O C CMCMt-Ii-4i-4CMi-4CMCM 11 C OO OO O M -r» O O r-tr*» O O O O O O CM O O O O O CO O 1-1 O O O O O Mfo O O O O CM r-4 O r«4 C i4O Or-4 O i—4 O CO O § i—4 g P— 25. O 1-40 1-10 1-10 1-40 O 1-4 f 3 CM >3* Mf O O O T - C O OO J - C r4 Mr 0H T*r4 MC H M OC O'i-4 CO CM CM H CMCM T-* r-4 00 H Mfr m r-4 CM o r*- mo CO or*. in (O o CM CM O O O CO 1-40 O O O O O O i—4 O r—I O 1-40 1-40 r—I O i—4 O O O O O O O 1-40 CO O O O CM D \ CM 1-4 r4 fC rIM - r4 OO OOO C M - - MO C — C CM O O CM O CM 1—1 CMO O 0 MV C MO CO CM CM CM\0 VOCM O O cn CM £ f4 T - O C O OO O O CM O 1-4 O O C O m O H H i-4O CM CM © CM < o ON i-4 M M M CM CM CM CM 1 O O O mo mo O O O '■O co < M r-4 CM o X X X X X X X r»- - 4 4 O r Ci- - M 4 4 r O - - 4 mo o o r-4 \OCT' CM m CO CO CM H cm co m o o m co -0 1-40 O O O O 1-40 cm — iM H i-M i—4 - O O r-4 O O O O *-« ko r* oo O CM O r-4 m o on O 311 — - -r© OCM O - CM* * M C i-H O M C O -fr i—4 © r-4 O O O t MC C C C C C C CM CM m CO CM O CM O O CM CM H rH O CM CMCO CO H CM CM CM O O APPENDIX II 314 HIGH-PLAGIOCLASE ARKOSE #1 QTZ CHT PLAG KSPAR BAS AND PRFMRF SRF HVY E/E+B P/F SP75 41.0 3.0 31.0 10.0 0.0 2.0 3.0 4.0 1.0 7.0 0.0 0.756 SP67 41.0 5.0 24.0 8.0 2.0 7.0 2.0 3.0 3.0 5.0 0.0 0.750 SP64 40.0 4.0 28.0 10.0 0.5 3.5 4.0 1.0 3.0 6.0 0.0 0.737 SP52 37.0 6.0 30.0 10.0 1.5 1.5 1.0 2.0 5.0 6.0 0.0 0.750 SP49 45.0 1.0 21.0 3.0 2.5 3.5 1.0 2.0 4.0 17.0 27.0 0.875 SP44 48.0 3.0 28.0 6.0 2.0 1.0 2.0 1.0 3.0 6.0 32.8 0.824 SP41 40.0 4.0 31.0 13.0 0.0 0.0 1.0 2.0 2.0 6.0 0.0 0.705 SP30 44.0 2.0 27.0 10.0 2.0 3.0 5.0 2.0 1.0 5.0 0.0 0.730 SP27 41.0 1.0 22.0 12.0 2.0 2.0 3.0 5.0 0.0 11.0 0.0 0.647 SP23 21.0 2.0 31.0 1.0 4.5 4.5 0.0 2.0 5.0 31.0 99.5 0.969 C19 40.0 1.0 34.0 15.0 0.5 0.5 0.0 1.0 0.0 7.0 39.2 0.694 C15 43.0 1.0 39.0 6.0 0.0 0.0 1.0 1.0 1.0 8.0 39.2 0.867 ST23 36.0 1.0 36.0 11.0 0.5 2.5 0.0 1.0 0.0 11.0 9.9 0.766 ST21 42.0 0.0 31.0 8.0 0.0 0.0 0.0 0.0 0.0 18.0 6.2 0.795 ST21 47.0 0.0 30.0 9.0 0.0 2.0 0.0 1.0 2.0 10.0 14.1 0.769 ST16 36.0 0.0 38.0 10.0 0.0 0.0 2.0 1.0 1.0 10.0 0.0 0.792 ST15 40.0 1.0 30.0 13.0 0.0 1.0 1.0 0.0 1.0 13.0 0.0 0.698 ST13 43.0 1.0 28.0 13.0 0.5 1.5 2.0 0.0 0.0 11.0 0.0 0.683 ST11 43.0 1.0 31.0 9.0 0.5 1.5 1.0 1.0 2.0 9.0 11.0 0.775 P28 58.0 1.0 28.0 3.0 0.5 1.5 0.0 0.0 1.0 6.0 0.0 0.903 P25 24.0 1.0 31.0 17.0 3.0 4.0 1.0 4.0 1.0 11.0 33.0 0.646 P5 29.0 8.0 30.0 18.0 1.0 0.0 2.0 3.0 2.0 5.0 0.0 0.625 P9 27.0 2.0 40.0 13.0 0.0 2.0 5.0 1.0 1.0 9.0 0.0 0.755 P7 42.0 1.0 39.0 7.0 0.5 1.5 1.0 1.0 1.0 6.0 19.6 0.848 PI 31.0 5.0 26.0 16.0 3.0 2.0 1.0 3.0 4.0 6.0 0.0 0.619 M2 3 28.0 2.0 45.0 11.0 2.0 0.0 0.0 0.0 0.0 10.0 14.1 0.804 M33 29.0 6.0 27.0 17.0 0.0 4.0 2.0 1.0 2.0 12.0 22.0 0.614 M47 31.0 2.0 36.0 15.0 0.0 2.0 2.0 3.0 2.0 7.0 32.8 0.706 M97 39.0 7.0 27.0 10.0 1.5 5.5 3.0 3.0 2.0 2-0 0.0 0.730 M95 35.0 3.0 24.0 16.0 2.0 2.0 3.0 5.0 2.0 7.0 16.4 0.600 M90 22.0 9.0 29.0 8.0 3.0 10.0 4.0 2.0 5.0 7.0 24.4 0.784 M77 40.0 2.0 33.0 10.0 0.0 0.0 1.0 1.0 0.0 13.0 8.3 0.767 M58 32.0 5.0 32.0 15.0 1.0 0.0 1.0 4.0 1.0 7.0 78.4 0.681 M56 28.0 4.0 28.0 15.0 2.0 2.0 2.0 4.0 2.0 12.0 28.0 0.651 H48 42.0 3.0 24.0 13.0 2.0 4.0 2.0 1.0 2.0 8.0 0.0 0.649 H42 40.0 3.0 26.0 16.0 1.0 0.0 1.0 1.0 1.0 7.0 32.3 0.619 H36 39.0 2.0 21.0 11.0 3.5 4.5 4.0 2.0 3.0 12.0 22.0 0.656 H31 33.0 1.0 33.0 14.0 2.0 3.0 2.0 0.0 0.0 11.0 11.0 0.702 HI 8 34.0 2.0 31.0 19.0 2.0 0.0 0.0 0.0 1.0 7.0 32.3 0.620 H3 39.0 3.0 31.0 11.0 3.0 3.0 2.0 2.0 2.0 5.0 0.0 0.738 D60 29.0 5.0 38.0 13.0 2.0 1.0 3.0 2.0 2.0 6.0 47.6 0.745 D16 37.0 4.0 35.0 13.0 0.0 1.0 1.0 1.0 .0 .0 0.0 0.729 315 HIGH-PLAGIOCLASE ARKOSE #1 (Cont'd.) QTZ CHT PLAG KSPAR BAS AND PRF MRF SRF HVY E/E+B P/F D37 29.0 2.0 42.0 2.0 0.0 6.0 7.0 1.0 1.0 8.0 14.1 0.955 D23 35.0 1.0 31.0 6.0 9.0 2.0 3.0 2.0 3.0 8.0 24.4 0.838 D1 31.0 2.0 34.0 18.0 1.0 4.0 1.0 1.0 1.0 7.0 0.0 0.654 SP55 38.0 18.0 18.0 5.0 3.0 2.0 2.0 2.0 9.0 2.0 0.0 0.783 M83 47.0 0.0 37.0 7.0 0.0 1.0 1.0 0.0 1.0 5.0 48.8 0.841 M82 44.0 1.0 33.0 7.0 3.0 2.0 1.0 0.0 1.0 7.0 32.8 0.825 M79 37.0 2.0 42.0 7.0 0.0 0.0 1.0 0.0 0.0 11.0 11.0 0.857 Ml 9 43.0 1.0 33.0 11.0 0.0 1.0 1.0 0.0 1.0 6.0 16.4 0.750 BB2 46.0 0.0 34.0 10.0 0.0 3.0 1.0 0.0 1.0 5.0 19.6 0.773 BB1 46.0 2.0 31.0 8.0 0.0 0.0 0.0 1.0 1.0 10.0 24.7 0.795 SB1 43.0 0.0 33.0 9.0 0.0 0.0 0.0 1.0 0.0 12.0 0.0 0.786 C17 56.0 0.0 32.0 2.0 0.0 0.0 0.0 0.0 0.0 8.0 39.2 0.941 MEAN 38.0 2.7 31.2 10.6 1.3 2.1 1.7 1.5 1.7 8.6 17.3 0.751 VAR 58.5 8.9 31.0 19.3 2.6 4.1 2.2 1.8 2.8 19.9 422.2 0.008 STDV 7.6 3.0 5.6 4.4 1.6 2.0 1.5 1.4 1.7 4.5 20.5 0.090 316 HIGH-PLAGIOCLASE ARKOSE #2 QTZ CHT PLAG KSPAR BAS AND PRF MRF SRF HVY .E/E+B P/F BH1 41.0 2.0 38.0 9.0 0.5 1.5 1.0 0.0 2.0 5.0 0.0 0.809 N7 27.0 1.0 28.0 13.0 0.0 3.0 4.0 3.0 0.0 21.0 13.2 0.683 N5 28.0 0.0 41.0 10;0 0.0 5.0 6.0 1.0 2.0 7.0 14.1 0.804 N4 29.0 2.0 42.0 9.0 1.0 0.0 1.0 2.0 1.0 15.0 9.9 0.824 NH1 44.0 2.0 30.0 9.0 0.0 1.0 1.0 1.0 1.0 11.0 0.0 0.769 HI2 52.0 0.0 31.0 8.0 0.0 0.0 1.0 1.0 1.0 6.0 0.0 0.795 HI1 47.0 2.0 29.0 7.0 0.0 1.0 3.0 1.0 2.0 8.0 0.0 0.806 NH5 46.0 10.0 24.0 6.0 0.5 1.5 0.0 1.0 3.0 8.0 19.6 0.800 NR10 46.0 4.0 19.0 7.0 0.5 0.5 0.0 1.0 2.0 10.0 7.6 0.731 NR1 49.0 1.0 21.0 11.0 0.0 0.0 0.0 0.0 3.0 15.0 0.0 0.656 NE1 44.0 2.0 33.0 13.0 0.0 0.0 0.0 0.0 0.0 8.0 0.0 0.717 NE7 48.0 7.0 25.0 9.0 0.0 0.0 1.0 1.0 0.0 9.0 0.0 0.735 NE9 50.0 1.0 29.0 10.0 0.0 0.0 1.0 1.0 0.0 8.0 0.0 0.744 MEAN 42.4 2.6 30.0 9.3 0.2 1.0 1.5 1.0 1.3 10.1 5.0 0.759 VAR 75.3 8.3 50.7 4.6 0. 1 2.2 3.3 0.7 1.2 19.9 49.6 0.003 STDV 8.7 2.9 7. 1 2.1 0.3 1.5 1.8 0.8 1.1 4.4 7.0 0.053 317 CHERT-RICH LITHIC ARENITE QTZ CHTPLAGKSPAR BAS ANDPRF MRF SRF HVY E/E+B P/F 02 26.0 23.0 6.0 1.0 2.5 10.5 0.0 2.0 16.0 16.0 90.9 0.857 B3 27.0 22.0 15.0 0.0 3.0 11.0 1.0 4.0 8.0 7.0 82.0 1.000 CL6 36.0 7.0 29.0 5.0 2.0 3.0 2.0 5.0 3.0 8.0 47.2 0.853 CL 7 24.0 17.0 19.0 1.0 3.5 9.5 6.0 7.0 4.0 11.0 56. 3 0.950 B1 30.0 13.0 20.0 3.0 4.0 10.0 2.0 4.0 8.0 7.0 64.5 0.870 CL8 25.0 19.0 26.0 1.0 8.0 2.0 3.0 4.0 5.0 6.0 48.8 0.963 WA15 27.0 24.0 14.0 4.0 3.0 14.0 1.0 5.0 4.0 5.0 0.0 0.778 WA13 31.0 45.0 12.0 1.0 0.0 3.0 1.0 1.0 2.0 3.0 95.2 0.923 WA10 22.0 12.0 29.0 1.0 0.0 0.0 0.0 2.0 5.0 26.0 76.9 0.967 WA12 36.0 29.0 16.0 1.0 1.0 3.0 1.0 2.0 5.0 6.0 24.4 0.941 WA5 29.0 39.0 12.0 5.0 2.5 1.5 1.0 3.0 3.0 4.0 90.9 0.706 WA2 43.0 0.0 27.0 10.0 0.5 2.5 0.0 6.0 4.0 6.0 0.0 0.730 WA14 33.0 39.0 13.0 4.0 0.0 3.0 0.0 2.0 2.0 3.0 47.6 0.765 SP11 10.0 34.0 8.0 0.0 7.0 7.0 0.0 6.0 23.0 3.0 95.2 1.000 SP5 32.0 15.0 24.0 6.0 1.0 6.0 2.0 6.0 3.0 4.0 47.6 0.800 SP2 27.0 21.0 24.0 0.0 1.5 6.5 1.0 6.0 8.0 5.0 0.0 1.000 C0W2 33.0 28.0 12.0 0.0 5.0 5.0 0.0 7.0 8.0 2.0 0.0 1.000 C0W1 29.0 23.0 21.0 0.0 5.0 5.0 0.0 5.0 9.0 3.0 0.0 1.000 C0W3 25.0 33.0 18.0 0.0 3.0 9.0 0.0 6.0 5.0 0.0 0.0 1.000 C9 28.0 20.0 25.0 0.0 1.5 6.5 2.0 1.0 7.0 7.0 0.0 1.000 C7 22.0 40.0 11.0 0.0 0.5 10.5 1.0 3.0 10.0 2.0 47.6 1.000 C3 25.0 25.0 21.0 2.0 0.5 8.5 1.0 3.0 4.0 8.0 0.0 0.913 ST3 22.0 40.0 5.0 0.0 4.0 4.0 1.0 1.0 18.0 4.0 97.6 1.000 SP20 26.0 22.0 19.0 0.0 0.0 3.0 1.0 2.0 8.0 15.0 69.3 1.000 C0W4 36.0 29.0 13.0 0.0 2.5 2.5 0.0 2.0 13.0 1.0 0.0 1.000 SK2 25.0 58.0 13.0 0.0 0.0 0.0 0.0 0.0 1.0 2.0 0.0 1.000 Cl 22.0 32.0 18.0 0.0 2.0 7.0 0.0 2.0 15.0 2.0 0.0 1.000 Cl 3 26.0 26.0 20.0 0.0 3.0 5.0 0.0 1.0 8.0 10.0 22.0 1.000 SP7 2.0 12.0 20.0 0.0 1.0 1.0 1.0 2.0 3.0 47.0 98.6 1.000 WD4 24.0 16.0 21.0 6.0 0.0 14.0 1.0 2.0 8.0 11.0 16.4 0.778 MEAN 27.1 25.4 17.7 1.7 2.3 5.8 1.0 3.4 7.3 7.8 40.7 0.926 VAR 44.2 149.7 42.1 6.4 4.4 15.4 1.6 4.2 26.8 83.31445.9 0.009 STDV 6.6 12.2 6.5 2.5 2.1 3.9 1.2 2.0 5.2 9.1 38.0 0.097 318 MIXED LITHIC ARENITE/ARKOSE #1 QTZ CHT PLAG KSPAR BAS AND PRF MRF SRF HVY E/E+B P/F PA1 30.0 5.0 35.0 9.0 1.0 5.0 2.0 2.0 3.0 7.0 48.8 0.795 PA3 29.0 5.0 28.0 8.0 3.0 10.0 3.0 1.0 4.0 8.0 37.0 0.778 PA4 33.0 15.0 16.0 3.0 2.0 9.0 2.0 3.0 8.0 9.0 82.0 0.842 SU52 24.0 5.0 17.0 1.0 2.5 9; 5 1.0 2.0 5.0 34.0 99.5 0.944 SU45 36.0 5.0 24.0 6.0 2.5 11.5 4.0 3.0 3.0 6.0 64.5 0.800 SU44 35.0 8.0 16.0 6.0 2.0 16.0 3.0 3.0 5.0 4.0 95.2 0.727 SU41 31.0 8.0 21.0 7.0 4.0 8.0 2.0 5.0 8.0 6.0 16.4 0.750 SU39 34.0 16.0 23.0 5.0 2.5 7.5 1.0 7.0 3.0 2.0 0.0 0.821 SU34 29.0 8.0 28.0 8.0 2.5 6.5 2.0 9.0 4.0 4.0 48.8 0.778 SU27 26.0 5.0 27.0 6.0 7.5 10.5 4.0 8.0 4.0 2.0 95.2 0.818 SU22 32.0 7.0 25.0 9.0 4.5 5.5 1.0 4.0 3.0 5.0 64.5 0.735 ST7 53.0 2.0 14.0 2. C 0.5 1.5 0.0 21.0 1.0 7.0 32.3 0.875 ST6 59.0 2.0 16.0 3.0 0.0 0.0 1.0 6.0 7.0 5.0 0.0 0.842 U4 20.0 3.0 33.0 8.0 3.0 2.0 3.0 4.0 1.0 24.0 74.1 0.805 U3 19.0 4.0 23.0 1.0 5.0 1.0 1.0 5.0 9.0 30.0 87.0 0.958 SU57 26.0 6.0 28.0 0.0 3.5 3.5 0.0 4.0 9.0 22.0 92.7 1.000 SU48 43.0 4.0 18.0 5.0 0.5 6.5 2.0 3.0 1.0 15.0 87.9 0.783 SU25 37.0 6.0 21.0 7.0 3.0 13.0 2.0 4.0 3.0 2.0 90.9 0.750 SU19 48.0 4.0 26.0 6.0 1.0 5.0 3.0 2.0 2.0 2.0 47.6 0.813 SU14 37.0 6.0 31.0 6.0 3.0 4.0 4.0 2.0 3.0 2.0 0.0 0.838 sun 37.0 5.0 26.0 5.0 6.0 8.0 2.0 1.0 8.0 1.0 0.0 0.839 SU8 29.0 8.0 32.0 8.0 3.0' 8.0 0.0 0.0 6.0 6.0 19.6 0.800 MAI 38.0 8.0 27.0 4.0 3.0 4.0 0.0 5.0 7.0 3.0 32.3 0.871 MA4 35.0 5.0 29.0 6.0 0.0 3.0 3.0 9.0 3.0 7.0 32.8 0.829 MEAN 34.2 6.3 24.3 5.4 2.7 6 .6 1.9 4.7 4.6 8.9 52.0 0.825 VAR 89.8 11.3 35.2 6.7 3.3 15.9 1.6 18.0 6. 6 85.31214.1 0.005 STDV 9.5 3.4 5.9 2.6 1.8 4.0 1.3 4.2 2.6 9.2 34.8 0.068 319 DACITE-RICH ARKOSE QTZ CHT PLAG KSPAR BAS AND PRE MRF SRF HVY E/E+B P/F S47 29.0 7.0 34.0 1.0 4.0 7.0 1.0 4.0 2.0 14.0 9.9 0.971 S43 38.0 4.0 23.0 13.0 6.0 5.0 1.0 2.0 1.0 7.0 16.4 0.639 S37 36.0 2.0 27.0 6.0 4.5 13.5 1.0 1.0 3.0 3.0 0.0 0.818 S33 35.0 1.0 37.0 6.0 2.0 8.0 3.0 1.0 1.0 5.0 0.0 0.860 S28 31.0 4.0 26.0 11.0 8.0 0.0 2.0 0.0 3.0 12.0 0.0 0.703 S24 28.0 5.0 29.0 8.0 2.0 11.0 3.0 2.0 3.0 11.0 28.2 0.784 S20 42.0 5.0 30.0 7.0 1.5 5.5 2.0 0.0 2.0 3.0 0.0 0.811 S15 40.0 6.0 30.0 6.0 0.5 5.5 3.0 0.0 5.0 3.0 0.0 0.833 S12 42.0 2.0 25.0 7.0 1.5 10.5 2.0 0.0 4.0 5.0 0.0 0.781 S8 26.0 5.0 27.0 11.0 5.0 8.0 6.0 1.0 5.0 7.0 0.0 0.711 S7 40.0 7.0 21.0 9.0 1.5 7.5 2.0 3.0 0.0 8.0 0.0 0.700 S5 20.0 1.0 32.0 15.0 7.0 9.0 2.0 2.0 2.0 9.0 24.4 0.681 S35 44.0 5.0 22.0 10.0 2.0 6.0 0.0 1.0 6.0 3.0 32.3 0.688 S22 36.0 7.0 31.0 8.0 2.0 7.0 3.0 1.0 4.0 2.0 0.0 0.795 T12 40.0 4.0 27.0 6.0 2.0 10.0 0.0 0.0 5.0 4.0 0.0 0.818 T1 40.0 5.0 38.0 5.0 2.0 4.0 1.0 0.0 0.0 4.0 0.0 0.884 T13 31.0 3.0 33.0 10.0 2.0 5.0 0.0 1.0 3.0 11.0 0.0 0.767 T' 36.0 5.0 33.0 7.0 4.0 5.0 2.0 2.0 4.0 2.0 0.0 0.825 T7 40.0 3.0 28.0 9.0 4.0 3.0 3.0 2.0 2.0 4.0 0.0 0.757 T9 40.0 6.0 28.0 8.0 4.5 2.5 1.0 1.0 3.0 6.0 0.0 0.778 Yll 24.0 3.0 36.0 8.0 3.0 14.0 3.0 2.0 2.0 5.0 0.0 0.818 Y7 24.0 2.0 33.0 9.0 3.0 14.0 1.0 2.0 1.0 13.0 0.0 0.786 Y4 17.0 1.0 36.0 10.0 5.0 18.0 2.0 2.0 0.0 9.0 14.1 0.783 Y1 37.0 8.0 30.0 10.0 2.0 5.0 1.0 1.0 1.0 4.0 0.0 0.750 Y3 31.0 7.0 23.0 4.0 1.0 14.0 1.0 1.0 11.0 6.0 96.8 0.852 Y6 35.0 0.0 33.0 2.0 2.0 20.0 1.0 2.0 2.0 3.0 0.0 0.943 Y8 31.0 0.0 32.0 4.0 1.5 18.5 1.0 1.0 1.0 6.0 16.4 0.889 MEAN 33.8 4.0 29.8 7.8 3.1 8.8 1.8 1.3 2.8 6.3 8.8 0.793 VAR 51.1 5.4 21.7 9.8 3.6 26.4 1.6 1.0 5.4 12.2 404.8 0.006 STDV 7.1 2.3 4.7 3.1 1.9 5.1 1.3 1.0 2.3 3.5 20.1 0.078 320 BASALT-BEARING LITHIC ARENITE QTZ CHT PLAG KSPAR BAS AND PRF MRF SRF HVY E/E+B P/F NR3 36.0 14.0 22.0 1.0 8.0 1.0 0.0 1.0 14.0 1.0 0.0 0.957 NR6 36.0 17.0 20.0 1.0 7,0 3.0 1.0 1.0 12.0 2.0 0.0 0.952 NR7 29.0 10.0 28.0 3.0 8.0 2.0 0.0 1.0 12.0 6.0 16.4 0.903 NAN 16.0 68.0 4.0 0.0 4.0 1.0 0.0 0.0 4.0 3.0 0.0 1.000 MEAN 29.3 27.3 18.5 1.3 6.8 1.8 0.3 0.8 10.5 3.0 4.1 0.953 VAR 88.9 746.3 105.0 1.6 3.6 0.9 0.3 0.3 19.7 4.7 67.2 0.002 STDV 9.4 27.3 10.2 1.3 1.9 1.0 0.5 0.5 4.4 2.2 8.2 0.040 321 APPENDIX III 322 HIGH-PLAGIOCLASE ARKOSE #1 FAC 1 FAC 2 FAC 3 FAC 4 FAC 5 FAC 6 SP75 0.82974 0.23699 0.28551 0.13373 0.03516 -0.38421 SP67 0.69398 0.35862 0.48940 0.26305 0.00088 -0.25489 SP64 0.75518 0.25325 0.33720 0.15362 -0.01798 -0.45975 SP52 0.82829 0.33118 0.27547 0.30988 -0.00878 -0.14814 SP49 0.64996 0.43100 0.34769 0.37707 0.22410 -0.15243 ST -4 0.77198 0.35143 0.23897 0.32100 0.15895 -0.26929 SP4. 0.92519 0.22646 0.20207 0.15330 -0.04723 -0.14119 SP30 0.70299 0.21779 0.30641 0.23833 -0.03543 -0.53157 SP27 0.78649 0.21213 0.28021 0.25141 -0.13366 -0.36671 SP23 0.43661 0.32349 0.42399 0.66342 0.23475 -0.05723 C19 0.94187 0.14733 0.22023 0.18199 -0 . 07 4 00 -0.02216 C15 0.86066 0.24538 0.20788 0.19774 0.27727 -0.18106 ST23 0.90183 0.17268 0.31137 0.20143 0.04930 -0.03891 ST21 0.92360 0.22194 0.19382 0.16247 0.17306 -0.03851 ST21 0.89574 0.27900 0.27436 0.15007 0.13593 -0.01972 ST16 0.88699 0.15743 0.22461 0.18889 0.09518 -0.27895 ST15 0.93190 0.17888 0.24241 0.13704 -0.04578 -0.12768 ST13 0.90105 0.17782 0.25824 0.14891 -0.06762 -0.23355 ST11 0.88387 0.26364 0.27003 0.20330 0.10458 -0.14977 P28 0.78296 0.37270 0.21675 0.16918 0.35811 -0.03118 P25 0.78245 0.09479 0.36727 0.35419 -0.28695 -0.12287 P5 0.85993 0.15391 0.20244 0.20345 -0.28840 -0.22938 P9 0.75718 0.07923 0.28912 0.14974 -0.06065 -0.52698 P7 0.85397 0.23934 0.27282 0.22735 0.22415 -0.17212 PI 0.79659 0.21521 0.28482 0.37018 -0.28524 -0.11163 M2 3 0.85103 0.11166 0.22513 0.36262 0.05355 -0.06313 M33 0.84305 0.15077 0.34754 0.09383 -0.27688 -0.21500 M47 0.87439 0.13665 0.29570 0.16004 -0.11386 -0.24475 M97 0.73824 0.30044 0.41821 0.21604 -0.05676 -0.36889 M95 0.79046 0.18127 0.28013 0.25390 -0.26592 -0.32973 M90 0.47997 0.27790 0.58712 0.33482 -0.10258 -0.46177 M77 0.92519 0.20249 0.20481 0.15922 0.08108 -0.16440 M58 0.89474 0.17128 0.21029 0.23152 -0.16158 -0.15157 M56 0.81223 0.16603 0.29666 0.29575 -0.24532 -0.25191 H48 0.81338 0.24722 0.35583 0.25211 -0.14678 -0.21919 H42 0.91699 0.17633 0.19381 0.19264 -0.19478 -0.11169 H36 0.65091 0.24621 0.37185 0.35532 -0.15814 -0.43311 H31 -0.-84428 0.11991 0.33451 0.28341 -0.13405 -0.23610 HI 8 0.89626 0.10447 0.19950 0.27342 -0.25885 0,00115 H3 0.78631 0.24478 0.33463 0.37816 -0.05527 -0.24919 D60 0.79941 0.15856 0.26587 0.32056 -0.09800 -0.36207 D16 0.91423 0.20100 0.24812 0.16310 -0.03044 -0.14146 D37 0.48417 0.15040 0.38338 0.13063 0.23480 -0.70873 D23 0.45129 0.22707 0.26577 0.73969 -0.01862 -0.31273 D1 0.86858 0.10502 0.35062 0.19373 -0.22297 -0.10617 SP55 0.54445 0.60761 0.24339 0.40864 -0.01802 -0.27274 M83 0.87350 0.24709 0.24218 0.17431 0.24166 -0.15809 323 HIGH-PLAGIOCLASE ARKOSE #1 (cont'd.) FAC 1 FAC 2 FAC 3 FAC 4 FAC 5 FAC 6 M82 0.78779 0.26774 0.28977 0.40527 0.13942 -0.15167 M79 0.86862 0.18745 0.21287 0.20094 0.23625 -0.18617 M19 0.92091 0.20859 0.24388 0.15191 0.05841 -0.13942 BB2 0.89098 0.22709 0.31880 0.14200 0.10934 -0.13375 BB1 0.90932 0.28104 0.18783 0.16103 0.17554 -0.03930 SB1 0.92823 0.21503 0.19798 0.16597 0.14888 -0.04311 C17 0.79591 0.32918 0.16083 0.15213 0.42798 -0.05223 MEAN 0.80547 0.22578 0.28315 0.24562 0.00126 -0.21031 VAR 0.01620 0.00846 0.00648 0.01505 0.03181 0.02265 STDV 0.12727 0.09198 0.08048 0.12267 0.17835 0.15048 HIGH-PLAGIOCLASE ARKOSE #2 FAC 1 FAC 2 FAC 3 FAC 4 FAC 5 FAC 6 BH1 0.87513 0.23549 0.27300 0.22287 0.13969 -0.15409 N7 0.77735 0.09252 0.33070 0.10613 -0.15377 -0.48505 N5 0.65719 0.10117 0.38146 0.14230 0.02571 -0.60117 N4 0.85002 0.15845 0.23158 0.30256 0.11503 -0.19169 NH1 0.90335 0.26109 0.23939 0.14637 0.10939 -0.15428 H12 0.89369 0.27586 0.19080 0.15047 0.18690 -0.14675 Hll 0.81024 0.28702 0.23599 0.13864 0.15667 -0.38155 NH5 0.82038 0.46044 0.22590 0.17233 0.15725 -0.02742 NR10 0.86030 0.38525 0.18345 0.16159 0.10689 -0.00882 NR1 0.91083 0.29762 0.16978 0.11989 0.00339 0.01363 NE1 0.95170 0.18765 0.19200 0.14203 0.00441 -0.02316 NE7 0.90232 0.32146 0.16764 0.10444 0.06972 -0.15347 NE9 0.92105 0.24638 0.18782 0.12942 0.09326 -0.14130 MEAN 0.85643 0.25465 0.23150 0.15685 0.07804 -0.18885 VAR 0.00598 0.01094 0.00412 0.00285 0.00825 0.03579 STDV 0.07730 0.10459 0.06422 0.05339 0.09086 0.18919 325 CHERT-RICH LITHIC ARENITE FAC 1 FAC 2 FAC 3 FAC 4 FAC 5 FAC 6 02 0.07888 0.74644 0.51622 0.27792 -0.04015 0.05540 B3 0.18892 0.67597 0.61075 0.32481 0.06533 -0.14972 CL6 0.69038 0.38491 0.34114 0.34565 0.13675 -0.32761 CL 7 0.19495 0.39590 0.48417 0.29572 0.00010 -0.68636 B1 0.33592 0.52250 0.58941 0.44080 0.01377 -0.25692 CL 8 0.26187 0.42283 0.22711 0.72899 0.01241 -0.38503 WA15 0.27042 0.57903 0.69920 0.22956 -0.11110 -0.13448 WA13 0.39107 0.84312 0.14176 -0.06020 0.01092 -0.22127 WA10 0.65147 0.48067 0.17200 0.25021 0.35964 -0.10052 WA12 0.48866 0.78309 0.23289 0.15944 0.13525 -0.20704 WA5 0.47215 0.75804 0.12625 0.25346 -0.20519 -0.20821 WA2 0.84362 0.31677 0.30466 0.20454 0.04515 -0.02784 WA14 0.54750 0.78855 0.17602 -0.03504 -0.05791 -0.05860 SP11 -0.11819 0.67779 0.28643 0.58432 -0.14824 0.01472 SP5 0.63529 0.46830 0.45324 0.18772 0.10404 -0.33030 SP2 0.37043 0.66921 0.45005 0.28759 0.20605 -0.21150 C0W2 0.21047 0.74834 0.29379 0.51053 0.02153 -0.04456 C0W1 0.27398 0.67068 0.33921 0.58221 0.10177 -0.05023 C0W3 0.22668 0.73858 0.48699 0.30964 0.05122 -0.06860 C9 0.40322 0.60894 0.45881 0.27226 0.21751 -0.33043 C7 0.11236 0.83442 0.50007 0.03029 -0.01822 -0.14959 C3 0.43454 0.64342 0.55379 0.09513 0.09391 -0.20842 ST3 0.00539 0.83594 0.18782 0.40257 -0.11870 -0.09574 SP20 0.44104 0.74492 0.28237 0.14243 0.23623 -0.22453 C0W4 0.30120 0.83964 0.18310 0.35175 0.10666 -0.00923 SK2 0.30596 0.85073 -0.06492 -0.06507 -0.00872 -0.10105 Cl 0.17830 0.79757 0.38636 0.30634 0.06480 -0.01035 C13 0.32362 0.73631 0.35725 0.43043 0.13091 -0.04029 SP7 0.48041 0.50645 0.25096 0.37593 0.26955 -0.35579 WD4 0.41686 0.48129 0.74120 0.04511 -0.04203 -0.10713 MEAN 0.34725 0.67141 0.35896 0.27550 0.05144 -0.16771 VAR 0.04323 0.02519 0.03428 0.03661 0.01603 0.02379 STDV 0.20792 0.15871 0.18514 0.19134 0.12660 0.15424 MIXED LITHIC ARENITE/ARKOSE #1 FAC 1 FAC 2 FAC 3 FAC 4 FAC 5 FAC 6 PA1 0.76532 0.25084 0.43186 0.24813 0.03118 -0.28307 PA3 0.55569 0.27838 0.60511 0.33972 -0.05705 -0.34998 PA4 0.39617 0.59779 0.56635 0.26027 0.03434 -0.27094 SU52 0.33309 0.45817 0.69800 0.37232 0.14661 -0.16477 SU45 0.48952 0.31658 0.62052 0.24570 0.00542 -0.44778 SU44 0.37314 0.38818 0.75242 0.14774 -0.06091 -0.30082 SU41 0.47955 0.43593 0.52704 0.46141 -0.09235 -0.24483 SU39 0.55255 0.51375 0.49799 0.30928 0.02286 -0.18755 SU34 0.60385 0.35473 0.47515 0.34617 -0.04488 -0.29822 SU27 0.31453 0.27251 0.53018 0.58605 -0.09138 -0.40855 SU22 0.63167 0.33104 0.43303 0.50607 -0.11488 -0.14581 ST7 0.47795 0.41412 0.16031 0.11815 0.20953 -0.09397 ST6 0.66849 0.51290 0.14107 0.13520 0.26706 -0.13521 U4 0.66232 0.15326 0.32339 0.44518 -0.03449 -0.45068 U3 0.32699 0.41916 0.24870 0.75343 0.12510 -0.19668 SU57 0.41630 0.49274 0.35879 0.58685 0.28015 -0.05479 SU48 0.67999 0.38588 0.47254 0.09471 0.11853 -0.28975 SU23 0.49861 0.36260 0.68386 0.27399 -0.04832 -0.22332 SU19 0.71518 0.34908 0.38722 0.17809 0.13489 -0.37300 SU14 0.61276 0.30300 0.36371 0.37341 0.06754 -0.49097 s u n 0.44209 0.39394 0.48924 0.58752 0.01856 -0.20963 SU8 0.63378 0.35136 0.53335 0.40723 -0.00082 -0.00591 MAI 0.60560 0.50004 0.36446 0.45478 0.15807 -0.04157 MA4 0.68447 0.33117 0.32722 0.15455 0.12267 -0.44197 MEAN 0.53869 0.38196 0.45798 0.34941 0.05008 -0.25457 VAR 0.01784 0.00999 0.02503 0.03055 0.01273 0.01904 STDV 0.13355 0.09993 0.15821 0.17479 0.11281 0.13799 327 DACITE-RICH ARKOSE FAC 1 FAC 2 FAC 3 FAC 4 FAC 5 FAC 6 S47 0.47854 0.35923 0.49375 0.50498 0.24509 -0.20195 S43 0.65900 0.23426 0.37122 0.52378 -0.22671 -0.10044 S37 0.48001 0.30543 0.68853 0.41121 0.02721 -0.09940 S33 0.65361 0.22030 0.52322 0.28603 0.14217 -0.37209 S28 0.56195 0.20077 0.19725 0 70520 -0.19700 -0.21083 S24 0.56877 0.26166 0.64302 0.24786 -0.03647 -0.35941 S20 0.75016 0.32086 0.42693 0.24364 0.10563 -0.26204 S15 0.69361 0.35652 0.42306 0.17729 0.13499 -0.37367 S12 0.63277 0.33505 0.60950 0.19831 0.06190 -0.21530 S8 0.46233 0.19448 0.45905 0.41638 -0.19845 -0.55652 S7 0.71577 0.32388 0.49959 0.16901 -0.06470 -0.26185 S5 0.54124 0.10643 0.50283 0.56218 -0.28501 -0.18644 S35 0.74336 0.39879 0.42861 0.27916 -0.04824 0.02562 S22 0.66822 0.31912 0.48350 0.28225 0.01648 -0.36214 T12 0.62836 0.38816 0.59739 0.27550 0.11182 0.01198 T1 0.75491 0.28240 0.36430 0.32058 0.23127 -0.17641 T13 0.79121 0.24569 0.42940 0.33785. -0.00677 -0.02135 T4 0.64941 0.31935 0.41445 0.48116 0.04874 -0.26215 T7 0.69412 0.26434 0.32788 0.44125 -0.03697 -0.35973 T9 0.70217 0.33556 0.30196 0.51821 -0.00326 -0.14063 Yll 0.50441 0.19236 0.70099 0.30490 -0.01551 -0.32650 Y7 0.54814 0.18588 0.72742 0.30833 -0.04763 -0.11976 Y4 0.41444 0.11337 0.76425 0.37810 -0.11648 -0.19099 Y1 0.79838 0.29447 0.40699 0.28148 -0.03417 -0.14659 Y3 0.39339 0.46833 0.72705 0.18235 0.09197 -0.08299 Y6 0.37341 0.27650 0.82747 0.18020 0.20889 -0.10278 Y8 0.43246 0.23411 0.82781 0.14971 0.15220 -0.10574 MEAN 0.60349 0.27916 0.52472 0.33951 0.00967 -0.20593 VAR 0.01622 0.00710 0.02787 0.01994 0.01896 0.01863 STDV 0.12737 0.08426 0.16693 0.14119 0.13770 0.13651 328 APPENDIX IV 329 BEDWELL HARBOR Section along the south coast of North Pender Island inside Bedwell Harbor. Section begins in bay near gravel road leading to beach and ends near the bridge between North Pender and South Pender Islands. Footage Description CEDAR DISTRICT FORMATION 0-208 (P~l> P-2, P-3) Fining upward sequences of classic turbidites exhibiting TjjcDE» ^BDE» Tc d e anc^ rare Ta b c d E bedding, some noncyclic sequences as well. 208-223 Shale. 223-239 Covered. 239-307 (P~4, P-5) Fining upward and noncyclic sequences of Tcde, Tbcde, Tbde and rare TabcDE turbidites, ss/sh 1:1 approximately. 307-335 (P-7, P-8 ) Sandstone; with some interbedded siltstone and shale, rough fining - upward sequences, sandstone shows featureless and horizontal bedding, some convolute bedding. 335-349 Fining upward sequence of classic turbidites. 349-354 (P-9) Sandstone, massive, featureless. 354-376 (P—10) Conglomerate, disorganized, very poorly sorted, ave. clast = 2", largest clast = 7". 376-388 (P-ll) Siltstone, highly sheared, massive, featureless. ' • ■ - 388-398 (P-12) Conglomerate, disorganized, clasts range from 4-18" in size. 398-410 Interbedded sandstone and shale, irregular erosive contact between sandstone and conglomerate. 410-429 (P-13) Sandstone, massive to horizontally bedded, connected dish structures. 429-539 (P-14, P-15) Fining upward sequences of Tc d e an^ tBCDE classic turbidites. 539-600 ' Covered. 600-648 Shale. Footage Description 648-789 (P-16, P-17, P-18) Fining-upward sequences of thin bedded Tb CDE and T cq e Classic turbidites. 789-888 (P-19, P-20) Sandstone, massive, featureless, some horizontal lamina tion, highly sheared near top of interval. 888-925 Covered. 925-1029 (P-21, P-22) Sandstone, massive, feature less, grades to horizontally-bedded upward, small conglomerate lenses, lutite clasts, clasts show a(i) a(p) lineation. 1029-1106 (P-23, P-24) Noncyclic and fining upward sequences of classic turbidites, largely shale near top of interval, TgcDE and T cde bedding. 1106-1154 Covered. 1154-1236 (P-25, P-26) Sandstone, fines upward to sandstone with thin shale and siltstone interbeds, massive, featureless at base, horizontal lamination well-defined near top of interval. 1236-1356 (P-27, P-28, P-29) Fining-upward sequence of t BCDE» tCDE and rare tABCDE classic turbidites. 1356-1415 (P-30, P-31) Shale, some siltstone inter beds, fines upward to undifferentiated shale. 1415-1434 (P-32) Fining-upward and noncyclic sequences of thin-bedded Tq^e and TgQgE classic tur bidites. 1434-1480 Shale. 1480-1506 Covered. 1506-1535 Shale, some interspersed siltstone interbeds, poor exposure. 1535-1585 (P-33) Shale. CUSHEON CREEK SECTION This section was measured along the northeast coast of Saltspring island. Section begins near mouth of Cusheon Creek and ends at large public beach. Footage Description EXTENSION FORMATION 0-7 (C-l) Interbedded conglomerate and sandstone, Approx. 60% conglomerate, lenticular beds, sandstone featureless, conglomerate disorganized. 7-111 (C-2, C-3, C-4, C-5, C-6 ) Conglomerate, individual lenticular beds noted in interval, some interbedded sandstones, disorganized and normally graded, rare inverse grading Ave. clast 2" largest clast 8 ", sandstone interbeds featureless to horizontally bedded. 111-118 (C-7) Sandstone, low angle cross-bedding to horizontal bedding. Cross~beds planar, sets 5-8" sandstone very pebbly. 118-129 (C-8 ) Conglomerate, disorganized, ave. clast 1.5" largest clast 8 ",, 129-148 (C-9) Sandst one with interbedded lenticular units of conglomerate, sandstone featureless, conglomerate disorganized. 148-181 (C— 10, C— 11) Sandstone, rare lutite clasts, featureless, some interbedded ‘horizontally laminated siltstone. 184-199 (C-12) Fining upward sequence of interbedded sandstone and siltstone, some lutite clasts in sandstone, units show T^q £ and bedding. 199-230 (C-13, C“ 14) Sandstone, grades upward into siltstone Numerous lutite clasts, featureless at base, horizontal lamination to undulatory lamination near top of interval. 230-353 Covered, strike change. . . . PENDER FORMATION 353-420 (C— 15) Fining-upward sequences of Tggpg and T^pg classic turbidites, rare T^gcDE units. 332 420-424 (C-16) Sandstone, thick horizontally laminated unit in turbidite sequence ripple bedding near top TgcDE unit* 424-800 (C-17, C-18, C-19) Fining-upward sequences of classic turbidites, entire interval fines upward, Tcde turbidites become more predominate near top of interval and shale % increases. 800-884 Shale with some interspersed Tcde classic turbidites. Section continues to fine upward. Some noncyclic sequences within this interval, ave. thickness of siltstone or sandstone bed - 1/2 ", rare sandstone beds 6- 10 ". 884-889 Fining upward sequences of Tg^pg and T^gg classic turbidites. 889-916 Very thin-bedded (ave. siltstone bed 1/2") Tqde turbidites. 916-919 Covered. 919-1030 Shale, some interspersed thin bedded (ave. thickness of siltstone beds = 1/2 ") Tqde classic turbidites. JP/1 DINNER BAY This section was measured along the west coast of Mayne Island. Measuring began on small point located along the southwest coast of Mayne Island, just south of Dinner Point. Section ends in southeastern portion of Dinner Bay. Footage Description DECOURCY FORMATION 0-29 (D-l) Fining-upward sequences of channelized interbedded conglomerate and sandstone, sandstone, massive, featureless, conglomerate, fines upward to gritstone some disorganized, some normally-graded. 29-58 Covered. 58-127 (D-2, D-3, D-4, D-5, D-6 ) Fining upward sequences of interbedded conglomerate, gritstone, and sandstone, 70% conglomerate, disorganized to normally-graded, ave. clasts 1-3", sandstone is featureless, massive. 127-182 (D-7) Sandstone with scattered conglomerate lenses conglomerate beds show basal erosive contact with sandstones, some faint horizontal lamination. 182-263 (D-8 , D-9, D-10) Interbedded fining-upward sequences of conglomerate, sandstone, and pebbly sandstone; most sandstone is featureless, some horizontal bedding, conglomerate is disorganized, and normally graded, beds very lenticular, large changes along strike. 263-273 (D-ll) Pebbly sandstone, grades into sandstone, featureless, some dish structures. 273-345 Interbedded sandstone and conglomerate beds, very lenticular, large changes along strike, 40% conglomerate fining-upward sequences, sandstone, featureless, to horizontal to convuluted bedding, some dish structures, conglomerate, disorganized to normally graded. 345-453 (D-12, D-13, D-14, D-15) Sandstone, massive, featureless, horizontal bedding, some convoluted bedding some dish structures, some' erosional surfaces present between individual units, some sandstone beds separated by siltstones exhibiting horizontal to convolute bedding, some individual unit fine upwards into siltstone. 334 453-457 Covered. 457-525 (D-16, D-17) Sandstone, fining-upward units grade from featureless at base to horizontally bedded and platy at top, some dish structures, highly sheared. 524-553 Shale, some TcDE and TBCDE interbeds, some facies E classic turbidites, abundant soft sediment deformation. 553-560 Intraclastic mixture of shale, siltstone, and some conglomerate clasts, lenticular beds, sandstone matrix. 560-565 Shale, silty. 565-573 (D—18) Sandstone,horizontal bedding. 573-579 Shale, v/silty. 579-627 (D-19, D-20) Sandstone,featureless, massive, some dish structures, some horizontal bedding. 627-631 Siltstone, highly sheared. 631-634 (D-21) Sandstone with scattered pebbles, lenticular bed, massive, featureless. 634-677 (D-22) Conglomerate, disorganized, ave. clast 2", largest clast 15". 677-685 Sandstone, pebbly at base, massive, featureless. 685-716 Conglomerate, some coarsening-upward and fining-upward sequences, lenticular bed. 716-753 (D-23) Sandstone and pebbly sandstone, interbedded, highly sheared, some horizontal lamination, most massive, featureless. 753-765 Covered. 765-831 (D-24) Interbedded sandstone and conglomerate lenses, large changes along strike, sandstone shows featureless to horizontal bedding, conglomerate is disorganized. 831-873 (D-25, D-26, D-27, D-28) Fining-upward sandstone beds, some beds grade upward to siltstone, most beds featureless at base, platy and horizontally bedded at top. 873-991 Covered. 991-1035 (D-29, D-30, D-31) Interbedded sandstone and conglomerate beds, very lenticular, large changes along strike, conglomerate disorganized, sandstone featureless to horizontally bedded, dishes. 1035-1040 Covered. 1040-1103 (D-32, D-33) Sandstone, fining-upward beds, featureless at base, horizontally-bedded and platy at top, some separated by ripple cross-laminated to horizontally- bedded siltstones, dishes. 1103-1144 Covered. 1144-1162 (D-34) Sandstone massive, featureless. 1162-1185 Covered. 1185-1187 Sandstone featureless, massive. 1187-1201 Covered. 1201-1206 (D-35) Sandstone, massive, featureless. 1206-1312 Covered. 1312-1399 (D-36, D-37, D-38, D-39, D-40) Sandstone, fining upward beds, featureless at base, platy and horizontal bedding at top, dish structures, rare ripple cross-lamination, and shale interbeds. 1399-1406 Shale, platy, v/silty, poorly defined ripples. 1406-1414 Covered. 1414-1518 (D-41, D-42) Sandstone, largely massive, featureless, some dish structures, some units fine upwards to platy, horizontally bedded sandstone. 1518-1564 Covered. 1564-1590 (D-43, D-44) Sandstone, beds 4 to 8 feet thick alternating with shale beds 1 inch to 1 foot thick, fining-upward sequences of TabDE Tad£ and TABCDE turbidites. 1590-1676 (D-45, D-46, D-47) Sandstone beds, featureless at base and horizontally laminated and platy near top of individual beds, some cross-bedding, sets 8-12", planar cross-bedded unit lenses out along strike, rare siltstone interbeds 1 inch to 2 feet thick. 1676-1679 Shale, v/silty. 1679-1689 (D-48) Shale, v/silty. 336 1689-1873 (D-49, D-50, D-51, D-52) Sandstone beds, some grade upward into siltstone, sandstone is massive, featureless to horizontally-bedded, some dish structures, siltstone is horizontally bedded, ripple cross-laminated, and/or convoluted. 1873-1876 Shale, v/silty. 1876-1881 Sandstone, massive, featureless. 1881-1929 (D-53, D-54) Interbedded sandstone and siltstone or shale, fining-upward sequence, sandstone generally featureless to horizontally bedded, with dish structures, siltstone horizontal to convolute bedding. 1929-1952 Sandstone, grades to siltstone, featureless at base, then horizontally bedded at top, dishes. 1952-1963 Shale with interbedded siltstone, 30% siltstone. 1963-1987 Sandstone, platy, he: jedding, v/silty, dishes. 1987-2000 Covered. 2000-2032 (D-56) Sandst:- ..osive to platy, featureless to wavy bedded, dishes. 2032-2046 Covered. 2041-2118 (D-58, D-59, D-60, D-61) Sandstone, featureless to platy and horizontally bedded, some interbedded siltstone horizontal to convolute bedding, fining-upward sequences. NORTHUMBERLAND FORMATION 2118-2215 (D-62, D-63) Fining-upward and noncyclic sequences of T b CDE anc^ ^CDE thin-bedded classic turbidites, some facies E turbidites. JP/1 HORTON BAY This section was measured along the southeast coast of Mayne Island. The section begins at the Government Dock in Horton Bay. Footage Description DECOURCY FORMATION 0-8 (H-l) Sandstone, featureless to v/faint horizontal bedding. 8-15 Shale. 15-59 (H-2, H-3) Fining-upward sequence of interbedded thick sandstones and siltstone or shale, sandstone shows featureless to horizontal bedding, siltstone shows horizontal to convolute bedding. 59-63 Alternating siltstone and shale, very poor exposure. 63-127 (H-4, H-5, H-6 ) Fining-upward sequences of interbedded siltstone and shale, rare sandstone beds at some bases of the sequences, 70% shale. NORTHUMBERLAND FORMATION 127-191 (H-7, H-8 , H-9) Shale, rare interspersed noncyclic siltstone layers. 191-205 Covered. 205-213 (H-10) Shale, interspersed Tq DE turbidites in noncyclic sequences. 213-363 Covered. 363-391 (H-ll, H-12) Fining-upward sequences of Tq q E classic turbidites. 391-506 (H-13, H-14) Fining upward to noncyclic sequences of thin-bedded TqDE and rare Tg^^g classic turbidites, sandstone beds ave. 1 " thick. 506-532 (H-16, H-17) Noncyclic sequences of TqqE thin-bedded "classic" turbidites, ave. sandstone bed is 1.5" thick, 20% sandstone. 532-565 Covered. 565-593 (H-18, H-19) Noncyclic sequences of thin-bedded Tc DE classic turbidites, 10% sandstone, sandstone beds average 3/4" thickness. 593-601 Covered. 602-632 (H-20) Noncyclic sequences of classic TCDE turbidites, 15% sandstone. 632-686 (H-21) Shale with thin interbedded TcDE classic turbidites. 686-703 Covered. 703-733 (H-22) Shale with interspersed siltstone interbeds, some show Tqqe bedding. 733-791 (H-23, H-24) Coarsening-upward sequence of T^gg and rare Tgggg classic turbidites. 791-818 Shale. 818-822 (H-25) Sandstone, massive, featureless. 822-878 Covered. 878-1085 (H-25, H-26, H-27) Shale with interspersed Tggg and rare TgcDE turbidites, < 5% sandstone. 1085-1201 (H-28, H-29) Shale, some thin siltstone laminations. GEOFFREY FORMATION 1201-1255 (H-30) Alternating thick sandstone beds and silty shale beds, sandstone beds are l'-8 ' thick. 1255-1303 (H-31, H-32) Sandstone massive, most featureless, some horizontal bedding, some thin lensitic interbedded shales separate sandstone units, fining upward sequences. 1303-1306 (H-33) Pebbly sandstone, featureless. 1306-1322 Sandstone, scattered pebbly lenses, most featureless, some horizontal bedding. 1322-1363 (H-34, H-35, H-36, H-37) Sandstone units 5-15 feet thick separated by 3" to 1 foot siltstone beds, some sandstones pebbly at base, then grade from featureless to horizontally bedded, interbedded siltstone layers are highly convoluted. 1363-1364 (H-38) Conglomerate, disorganized, lenticular. 1364-1394 (H-39, H-40, H-41) Sandstone with interbedded siltstone and pebbly sandstone interbeds, fining-upward sequences, sandstone is featureless to horizontally bedded. 1394-1408 Covered. 1408-1496 (H-42) Sandstone, massive, featureless, some dishes, some horizontal bedding. SPRAY FORMATION 1496-1582 (H-43, H-44, H-45) Interbedded siltstone and shale in fining-upward and noncyclic sequences of T^gg and Ta DE classic turbidites, ave. siltstone bed is 3/4" thick, rare TgcDE turbidites. 1582-1659 (H-46, H-47, H-48) Interbedded siltstone and shale in noncyclic sequerc.c- ’ ^^de classic turbidites ave. •■/4" thick.Rare TgcDE turbidites < I sandstone. Section ends at last major sandstone bed (72 feet) in the Spray Formation. MOUAT POINT SECTION Section measured along southern portion of the west coast of North Pender Island. Section begins along point southeast of Thieves Bay and continues along Mouat Point. Footage Description EXTENSION FORMATION 0-47 (M-l, M-2, M-3, M~4, M-5) Interbedded lenticular beds of sandstone, conglomerate, and pebbly sandstone. Most sandstone massive and featureless conglomerates are largely disorganized, some fining upward sequences from conglomerate to pebbly sandstone to sandstone. 47-64 (M-6) Shale v/silty, fines upward. 64-66 (M-7) Interbedded sandstone and conglomerate, smaller lenses, some sandstone shows sinusodal rippling. 66-83 Shale, blky. 83-91 (M-8) Conglomeratic sandstone, laminations of conglomerate in sandstone, fining upward. PENDER FORMATION 91-105 Shale. 105-139 (M-9, M-10) Fining upward classic turbidites, and Tqpjt bedding. 139-208 Shale, poor exposure. Some scattered siltstone layers, convolute to rippled. 208-214 Covered. 214-238 Shale. 238-527 Covered. 527-554 Shale. 554-557 (M-ll) Sandstone, featureless massive. 557-574 Shale, thinbeds of convoluted sandstone and siltstone interspersed. PROTECTION FORMATION 574-713 (M-12, M-13, M-14) Sandstone, units of sandstone in this interval suggest several course grained flows, most sandstone massive, featureless, some dish structures and horizontal lamination, rare convolute lamination and flame structures are also present, mg-vcg. 713-866 (M-15, M-16, M-17, M-18, M-19, M-20) Sandstone, fining upward sequences of sandstone initiated by pebble layers at base, most beds featureless, some show orizontal bedding, dish structures and outsize lutite clasts. Some units show convolute bedding near top. 866-867 Shale, silty, lensitic. 867-957 (M-21, M-22, M-23, M-24) Sandstone, featureless horizontally bedded, or convolute, very rare cross-bedding well developed flume structures, some erosion surfaces noted between flows. 956-980 (M-25) Conglomerate, some disorganized, some normal grading, possible poor inverse grading, poor to fair a(i) a(p) clast orientation, large variation in clast size, ave 1-2" in some areas and 5"-7" in others, largest clast 16". 980-992 (M-26, M-27) Pebbly sandstone which fines upward to featureless sandstone, possible dish structures, rare lutite clasts. 992-1034 (M-28, M-29, M-30, M-31) Interbedded lenticular units of sandstone and conglomerate, large changes in bed geometry along strike, well-developed erosional contacts between sandstone and overlying conglomerate, conglomerate, disorganized to normally-graded, sandstone, large lutite clasts show a(i) a(p) orientation, fining upward sequence-conglomerate to pebbly sandstone to sandstone. 1034-1074 (M“32) Pebbly sandstone grades upward into massive featureless sandstone. 1074-1086 Covered. 1080-1110 (M-33) Sandstone, featureless, massive, rare cross-bedding to horizontal lamination. 1110-1168 (M-34, M-35, M-36, M-37) Sandstone, some pebbly layers, most massive, featureless, some faint horizontal lamination, highly sheared in some areas. 1168-1252 (M-38) Poorly developed coarsening-upward? sequences of Tb CDE. tCDE and raremTABCDE classic turbidites, sandstone beds are 6" thick. 1252-1288 (M-39, M-40) Sandstone massive, featureless to horizontal bedding. 1288-1398 (M-41, M-42, M-43, M-44, M-45) Sandstone, layers of pebbly sandstone fine upward into sandstone, some horizontal bedding, most is featureless massive. 1398-1406 Conglomerate, inversely graded, ave. clast 1", largest clast 4". 1406-1456 (M-46, M-47, M-48) Pebbly sandstone and sandstone, units of pebbly sandstone fine upward into sandstone, sandstone is massive and featureless. 1456-1460 (M-49) Conglomerate, disorganized, ave. clast 3/4", largest clast 1.5". 1460-1471 Sandstone, massive, featureless. 1471-1489 (M-50) Conglomerate, disorganized, lenticular bed. 1489-1498 (M-51) Pebbly sandstone, featureless. 1498-1539 Conglomerate, disorganized, ave. clast 1/2", largest clast 1.5”. 1539-1577 (M-52, M-53) Sandstone alternating with lenticular beds of conglomerate and pebbly sandstone, fining-upward sequences, most conglomerate disorganized, some normal grading, sandstone is featureless, some small wood fragments, lutite clasts. 1577-1636 (M-54, M-55) Sandstone, some pebbly intervals, massive, featureless. 1636-1697 (M-56, M-57) Pebbly sandstone, some layers pebble free, most sandstone massive, featureless, some normal grading of pebbles, very large (2 feet) lutite clast, pebbly units fine upward into pebble-free units. 1697-1748 (M-58, M-59, M-60, M-61) Sandstone, vcg laminations in mg sandstone, near the base of the unit sandstone is horizontally laminated, without vcg laminations near top some pebbly layers. 1748-1788 (M-62) Sandstone, featureless, massive. 1788-1790 (M-63) Siltstone, ripple-cross-laminated. 1790-1835 (M-64, M-65, M~66) Sandstone, some featureless, some horizontally laminated, rare ripple cross-bedding, grades into siltstone near top of interval. 1835-1851 (M-67) Interbedded sandstone and siltstone, sandstone shows TA and IAg bedding, siltstone generally featureless or horizontally laminated. 1865-1918 (M-68) Conglomerate, distinct channel cut across each other, ave. clast range 3-8", largest 20”, some disorganized, some normal grading. 1918-1924 (M-69) Pebbly sandstone, featureless, lenticular bed. 1924-1961 (M-70) Conglomerate good a(i) a(p) clast lineation, some normal grading, some disorganized, ave. clast 3/4" - 2". 1961-2088 (M-71, M-72, M-73, M-74) Sandstone with interbedded lenticular units of conglomerates, sandstone is massive and featureless to horizontally laminated, some inverse grading noted in conglomerate, most conglomerate disorganized. 2088-2173 (M-75) Sandstone, some featureless, some horizontal bedding. 2173-2199 (M-76) Interbedded sandstone and siltstone, sandstone shows Ta and bedding. 2199-2233 (M-77, M-78) Sandstone, some featureless, some horizontal bedding, some undulatory bedding. 2233-2294 Covered. 2294-2357 (M-79, M-80, M-81) Sandstone, some small-scale cross bedding-rare, sets 2-3", most horizontal bedding to featureless. CEDAR DISTRICT FORMATION 2357-2417 Covered. 2417-2425 Poorly exposed TcDE ? classic turbidites. 2425-2559 Covered. 2559-2571 (M-82) Sandstone, beds 2-4 feet thick, horizontal bedding. 2571-2631 (M-84) Fining-upward sequence of Tjjqdj? and Tq D£ classic turbidites. 344 2631-2637 Shale. 2637-2658 (M-85) Fining upward sequence of Tggg and subordinate T jjcde turbidites, 35% sandstone. 2658-2662 Shale. 2662-2688 Fining upward sequence of TgEgE and Tggg classic turbidites. 2688-2707 Shale with scattered TCDE classic turbidites. 2707-2791 (M-86) Fining-upward sequences of TqqE and subordinate TgcDE classic turbidites. 2791-2845 Shale, some siltstone interbeds, < 1/2” thick. 2845-3087 Covered. 3087-3121 Shale, thin interspersed siltstone layers, some show Bouma "C" bedding. 3121-3195 Noncyclic to fining-upward sequences of T^gg classic turbidites, 90% shale, beds thicken near top of interval. DECOURCY FORMATION 3915-3233 (M-88, M-89, M-90) Conglomerate most disorganized, rare normal grading, well developed channel contacts for individual conglomerate beds in interval, highly sheared, lenticular interbeds of pebbly sandstone and sandstone, these increase in number near top of interval. 3233-3238 Pebbly sandstone, featureless. 3238-3245 (M-91) Interbedded conglomerate and pebbly sandstone, beds are lenticular, disorganized normally grading and inverse grading present. 3245-3255 (M-92) Sandstone, featureless, massive, some lenses of pebbly sandstone. 3255-3279 Conglomerate, disorganized, ave. clast 3", largest clast 10", rare, very poorly developed grading. 3279-3283 Shale, highly sheared. 3283-3325 (M-93) Interbedded conglomerate and sandstone - conglomerates disorganized, often contain rip~up clasts, erosional contacts between conglomerate and underlying sandstone beds, some pebbly sandstone lenses as well, sandstone featureless to horizontally bedded. 3325-3353 (M-94, M-95) Conglomerate, interspersed sandstone lense beds lenticular, sandstone lenses up to 5 1 thick and 50 in length. 3353-3387 Sandstone, very highly sheared, brecciated near top of interval, featureless, thickness doubtful due to shearing - in fault zone, center of syncline. 346 SATURNA ISLAND SECTION Section measured along the south coast. Began approximately 2 miles west of Taylor Point at small unnamed bay. Footage Description PROTECTION FORMATION 0-9 (ST-1, ST-2) Quartz-phyllite conglomerate, disorganized, other clasts include Is, greenstone, gneiss, chert. 9-45 (ST-3) Sandstone, some interbedded conglomerate at base, some low angle cross-bedding, Inoceramus shells in conglomerate lamination, some sandstone is horizontal to wavy bedding, some small-scale and trough cross-stratification, sequence is X-bdg, to bivalve-rich cgl., to lutite clast cgl., to horizontal and wavy bedded sandstone. CEDAR DISTRICT FORMATION 45-51 TBCDE and ^ABCDE turbidites, fining upward sequence. 51-81 (ST-4) Large matrix-supported conglomerate with siltstone matrix, highly disorganized. 89-117 TgcDE and Tq q E turbidites, some bivalve shell fragments in *B ’ layers. 117-207 (ST-5) Fining upward T^ECDE* TBCDE and TCDE turbidites. Sandstone layers 8-18" thick in TgCDE and Ta b c DE units. Fining upward continues in to shale in some sequences. 207-238 Dominantly shale, less than 5% siltstone. 238-243 (ST-6 ) Lensitic siltstones and sandstones with abundant Inoceramus and other bivalve remains. 238-321 (ST-7) Classic TBCDE and TCDE turbidites in fining upward sequences. 321-477 Covered. 477-526 (ST-8 ) Classic turbidites, sandstone interbedded with shale, sedimentary structures poorly exposed. 347 526-714 (ST-9, ST-10) Sandstone, some shale interbedded at base, medium grained to coarse grained, massive and largely featureless, some horizontal lamination, some poorly developed fining upward sequences. 714-730 Cove red. 730-737 (ST-11) Sandstone, medium-grained, massive, featureless. 737-751 Covered. 751-769 (ST-12) Sandstone, medium grained, massive featureless. 769-786 (ST-13) Thick-bedded facies B sands with interbedded siltstones and shales, sandstone exhibit featureless to horizontal, to wavy, to convolute bedding upwards. 786-859 (ST-14, ST-15) Sandstone, some interbedded conglomerate, horizontal to wavy bedding, small siltstone lenses, fining-upward sequences. 859-932 (ST-16) Thick bedded facies B sands with some classic turbidites in fining-upward sequences, sandstones show featureless, to horizontal bedding, to wavy and convolute bedding upwards, sandstone units are separated by siltstone and shale beds. 932-968 (ST-17) Sandstone, fining upward units, featureless and horizontal bedding. 968-1241 Covered. 1241-1290 (ST-18) Classic turbidites TgcpgTare and T ^ g beds in fining upward sequences, Inoceramus, shells and rare Diplocriterion burrows in sandstone layers. 1290-1316 Covered. 1316-1329 Shale with scattered siltstone interbeds, very poor exposure. 1329-1331 (ST-19) Sandstone beds showing horizontal then convolute bedding. 1331-1365 Fining upward sequences of Tgpg and rare Tgpg classic turbidites. 1365-1384 (ST-20) Sandstone, massive, featureless, rare scattered pebbles, and lutite clasts. 1384-1432 Shale, some siltstone interbeds, poor exposure. 1432-1444 (ST-21) Sandstone lenticular channeled unit, grades laterally into classic turbidites, featureless, to horizontal bedding upwards. 1444-1470 (ST-22) Classic turbidites, fining-upward sequences charondrites, rare Diplocriterion, TABCDE_rare» tBCDE and tCDE beddin8« DECOURCY FORMATION 1470-1493 Massive, featureless sandstone beds which grade upward into horizontally laminated units. SOUTHEY POINT Section measured along the northwest coast of Saltspring Island; section begins along west side of the tip of Southey Point. Footage Description CEDAR DISTRICT FORMATION 0-3 (S-l) Sandstone, poorly exposed, largely covered by talus. 3-47 (S~2, S-3) Interbedded units of sandstone 2-20 feet thick, separated by siltstone layers 1-3 feet thick, sandstones show TA featureless, horizontal, and convoluted bedding, some sandstone beds show T^gQ bedding, siltstone units are horizontally-bedded, ripple bedded, and/or convoluted. 47-66 Fining-upward sequence of thick-bedded TgQgE and T c d e turbidites. 66-71 (S-4) Sandstone, very silty, lenticular beds, lutite clasts, horizontal bedding. 71-73 Covered. 73-120 (S-5, S-6 , S-7 ) TadE, TABCDE, TAfiE fining-upward classic turbidites comprised of interbedded siltstone or shale and sandstone, sandstone beds 6 " - 36" thick, siltstone or shale beds 3" - 20”. 120-145 (S-8 , S-9) Sandstone, fines~upward to siltstone, lutite clasts, possible dish structures, wavy to convolute bedding at top of interval. 145-182 (S—10) Sandstone, some small interbeds of siltstone and shale, scour surface at base of some sandstone beds in interval, dish structures, featureless to horizontal bedding. 182-183 Covered. 183-184 Sandstone, shows Tg£ bedding. 184-187 Covered. 187-225 (S—11, S-12) Sandstone, sandstone beds in interval fine upwards into siltstone, possible dish structures, featureless, to horizontal to wavy and convolute bedding. 3 50 225-228 Shale, some scattered T c q E classic turbidites. 228-242 (S—13) Sandstone interbedded with small lenses of shale and siltstone, sandstone is massive, featureless, dish structures, some horizontal and wavy bedding, siltstone shows ripple bedding, large changes in units along strike. 242-275 Covered. 275-333 (S-14, S-15, S-16, S-17) Fining upward sequences of interbedded sandstone and siltstone or shale exhibiting tAB> TABDE» TABCDE and TBCDE Adding, most sandstone layers 1-4' thick and are featureless, shale and siltstone units 6 "-20" thick, dish structures in sandstones, some facies E bedding in siltstone. 333-366 Fining upward sequence comprised of Tg£DE and classic turbidites. 366-376 (S—18) Classic turbidites exhibiting TAE and TAgE bedding, sandstone beds l'-2 ' thick, shale beds 1 '-2 ' thick. 376-385 Shale with small siltstone beds interspersed, 80% shale. 385-412 Fining upward sequences of sandstone and siltstone or shale exhibiting Tgcog and T q EE bedding. 412-426 (S-19) Sandstone beds 8'-10' thick, separated by small siltstone lenses, sandstone, massive, featureless, siltstone shows horizontal to wavy bedding. 426-440 Covered. 440-524 (S-20, S-21) Repetitively interbedded sandstone and siltstone, sandstone generally shows TA or TAg bedding, siltstones show Tgg or T q bedding, some dish structures, abundant lutite clasts, fining-upward sequences. 524-560 (S-22) Sandstone beds 2'-5' thick alternating with siltstone beds 6 ”- 8 " thick, sandstone featureless to horizontally laminated. 560-588 (S—23) Sandstone interbedded with siltstone or shale in fining-upward sequences, sandstone is massive and featureless to horizontally laminated, siltstone is ripple cross-laminated, 50% sandstone. 588-600 Covered. 600-623 Shale with thin siltstone interbeds in fining-upward sequences comprised of Tc d e an(^ rare -^b CDE anc^ Ta b CDE classic turbidites. 623-651 (S-24) Fining-upward sequence of TgCDE» ^CDE anc* some T^bcDE classic turbidites, outsize lutite clasts common. 651-660 (S-25) Shale. 660-685 (S-25, S-26, S-27) Sandstone alternating with siltstone or shale in fining-upward sequences, sandstone shows featureless to horizontal bedding, some convolute bedding near top of some sandstone beds. 687-789 (S-28, S-29, S-30, s-31, S-32, S-33, S-34) Sandstone beds, some fining upward into siltstone, some dish structures, most sandstone is massive, featureless, some is horizontally laminated. 789-802 Covered. 802-843 (S-35) Fining-upward sequences of TgcDE an<^ TCDE classic turbidites, some T^gcDE* 843-857 Covered. 857-892 Fining-upward sequences of T q d e anc* ^gCDE d ass:*-c turbidites. 892-916 (S-36) Sandstone beds 4'-6 ' thick separated by 1 1—2 * siltstone beds, sandstone massive, featureless. 916-928 Classic turbidites, fining-upward sequence, TgcDE an^ Tcde bedding. 928-940 (S—37) Sandstone beds 4'-6 ' thick separated by shale and siltstone units 6 "-12" thick, sandstone massive to horizontally laminated. 940-1102 (S-38, S-39, S-40, S-42, S-43, S-44, S-45, S-46) Massive sandstone beds, some thin siltstone lamination, sandstone featureless, horizontally laminated or wavy bedded, dish structures. 1102-1112 Covered. 1112-1128 Sandstone, massive, featureless, some horizontal laminations, some dish structures. 1128-1131 Classic turbidites, TgQDE» TCDE anc* ^DE bedding. 1131-1157 (S-47, S-48) Sandstone beds 1.5'-8’ thick separated by 3"-8" siltstone beds, fining upward sequence. 352 SOUTH PENDER ISLAND Section measured along the south coast of Pender Island beginning at southwest portion of Island on Tilly Point. Footage Description COMOX FORMATION 0-34 (SP-1) Sandstone, massive, featureless, some beds cut by horizontally- or ripple-bedded siltstone. 34-38 (SP-2) Horizontally bedded siltstone, overlain by ripple cross-laminated siltstone, overlain by shale. This unit overlain by sandstone which is very rich in lutite clasts - this lutite clast layer is lensitic. 38-55 Sandstone beds, lutite clasts, beds featureless, separated by small beds of siltstone. 55-64 Covered. HASLAM FORMATION 64-73 (SP-3) Poorly developed fining upward TgCDE and T c d e classic turbidites. 73-110 Covered. 110-128 Shale, rare sandstone beds. 128-135 Covered. 135-188 Shale, blocky, featureless. EXTENSION FORMATION 188-349 (SP-4) Conglomerate, disorganized, some v/poor a(i) a(p) lineation, ave. clast 2 ", largest clast 11”, some sandstone lenses at 314-319. 349-367 Covered. 367-465 (Sp-5) Conglomerate, some a(i) a(p) lineation, and very poorly developed horizontal bedding, most disorganized, ave. clast 3", largest clast 9". 353 465-488 Conglomerate, cross-bedded, overlain by horizontally bedded conglomerate, sets 3'-5', planar, conglomerate grades from disorganized to cross-bedded. 488-490 (SP-6 ) Sandstone, scattered pebbles, some cross-bedding, some ripple cross-lamination, unit is very lenticular. 490-513 Conglomerate, largely disorganized, some horizontal lamination, ave. clast 1.5". 513-518 (SP-7) Interbedded sandstone and shale in lenticular outcrop, sandstone is highly convoluted. These units may be classic turbidites, 8"-24" thick. 518-794 (SP-8, SP-9) Conglomerate, disorganized, and normally-graded beds, ave. clast 2 ", largest 18", some inverse grading. 794-797 (SP-10) Sandstone lens, poorly developed ripple-bedding. 794-847 Conglomerate, normal and rare inverse grading, some sandstone layers. 847-859 Sandstone, v/poor exposure, featureless. 859-881 Conglomerate, as above. 884-937 (SP-11) Conglomerate, clasts vary greatly in size, most disorganized, some normal grading, rare sandstone lenses, channel contacts delineate some individual beds. 937-941 (SP-13) Sandstone, lenticular bed, scattered pebbles, featureless. 941-1015 (SP-14) Conglomerate, disorganized, ave. clasts 2"-5", largest clast 14". 1015-1020 Interbedded sandstone and conglomerate lenses, sandstone is featureless. 1020-1231 (SP-15, SP-16) Conglomerate, some normal grading rare inverse grading, most disorganized some sandstone and siltstone interbeds, ave. clast 3", largest clast 11". 1231-1250 Conglomerate, cross bedded, planar, sets 8-10 feet, clasts < 1". 1250-1262 (SP17) Sandstone, cross-bedded to horizontally bedded to convolute, fines-upward to shale, lenticular bed. 1262-1402 Conglomerate, disorganized, bimodal clast distribution in some areas, large variation in clast size. 1402-1469 Covered. 1469-1515 Conglomerate, largely disorganized, some distinct channel-cuts, ave. clast 4"-6", largest 10". 1515-1521 Siltstone, poor exposure, no visible bedding. 1521-1523 (SP-18) Alternating beds of sandstone and conglomerate, sandstone shows some horizontal lamination. 1523-1555 Conglomerate - matrix supported (debris flow?), fewer clasts upward. 1555-1603 Covered. 1639-1707 (SP-19, SP-20) Conglomerate, largely disorganized, several channel-shaped sandstone interbeds, sandstones are featureless. 1707-1840 (SP-21, SP-22) Interbedded sandstone and conglomerate units, 80% conglomerate, sandstones show horizontal to ripple bedding, conglomerates are disorganized or normally graded. PENDER FORMATION 1840-1845 (SP-23) Sandstone, contains shell hash, horizontal laminated, shells are largely bivalves, v/silty. 1845-1949 (SP-24) Siltstone to shale; some lenses of horizontally bedded sandstone, some lenses of shell hash, possible low angle cross-lamination, some horizontal bedding. 1949-2048 Covered. 2048-2066 Siltstone and shale, poor exposure, no bedding features. 2066-2070 Covered. 2070-2015 Shale, rare siltstone interbeds. PROTECTION FORMATION 2105-2202 (SP-25) Sandstone, featureless, highly sheared, facies B. 2202-2527 (SP-26, SP-27, SP-28) Coarsening upward and subordinate fining upward sequences of interbedded facies B sands and T c d e turbidites, sandstone beds range from 1 * —301 in thickness, some sandstone beds may be composite units, some contain lutite clasts, some show featureless to horizontal lamination to convolute lamination, intervals of T c d e turbidites, 6"-3' in thickness. 355 2527-2652 (SP-28, SP-29) Sandstone beds separated by classic turbidites T c d e , turbidites are better developed than in lower units of the Protection, some sandstone beds show cross-bedding, most are featureless or horizontally bedded or both. 2652-2746 (SP-30) Fining upward sequences of thick-bedded Tggpg, ^ABCDE anc* TABE turbidites, sandstone beds 1-3 feet thick. 2746-2758 (SP-31) Sandstone, largely covered by talus, poor exposure, featureless, massive. 2758-2829 (SP-32) Fining upward sequences of thin-bedded TgcpE> T c d e anc* tBDE "classic" turbidites, sandstone beds 1-5" thick, beds lens out rapidly along strike. 2829-2837 (SP-33) Sandstone, channel-shaped unit, featureless to horizontal bedding to convolute bedding upward, possible dish structures. 2837-2880 Fining-upward sequences of TgcDE anc^ ^CDE classic turbidites, some noncyclic sequences. 2880-2886 Covered. 2886-2899 Shale, some interspersed thin Bouma C layers, poor exposure. 2899-2922 Thin bedded, fining-upward to noncyclic TgcDE an(^ T c d e classic turbidites. 2922-2943 Shale, dk gray, blocky. 2943-2966 Tc d e an^ t b CDE classic turbidites, fining-upward. 2966-2979 (SP-34) Sandstone, Facies B sands, transition from featureless to horizontal to ripple bedding upward, tABC units. 2979-2988 Shale. 2988-3036 Covered. 3036-3069 Fining-upward sequences grading into noncyclic sequences of T c d e with subordinate Tgcg classic turbidites, some possible poorly developed coarsening upward sequences. 3069-3156 Covered. 3156-3182 TgcoE anc* TCDE classic turbidites, fining upward sequences. 3182-3309 Covered. 3309-3344 (SP-35) Channel sandstone bed which is replaced by shal and thin-bedded turbidites along strike. 3344-3594 Classic T c q E turbidites interspersed in undifferientated shale beds, < 10% siltstone, 90% shale 3594-3788 (SP-37, SP-38) Fining upward and noncyclic sequences consisting of T q q E and subordinate T b d E classic turbidites, rare TABCDE classic turbidites, gradual increase in sandstone bed thickness and sandstone percentage over entire interval. 3788-3804 (SP-39) Thicker bedded TBCDE classic turbidites than in lower interval, fining upward. 3804-3892 Covered. 3892-3922 (SP-40) Fining upward bundles (2T—5 * thick) of TEpE turbidites separated by equal thicknesses of shale, scattered lenticular sandstone beds. 3922-3959 Covered. 3959-3973 Sandstone, lenses out within 100 feet along strike, massive, featureless. 3973-3991 Thick-bedded T b CDE turbidites, sandstone beds 1-3 feet. 3991-3997 (SP-41) Large lenticular sandstone bed with dish structures, convoluted near top of unit, some faint horizontal bedding. 3997-4133 (SP-42) Fining-upward and very rare coarsening-upward sequences of TBEd e » ^CDE anc* rare ^ABCDE classi-c turbidites. 4133-4176 Shale, < 10% thin siltstone units. 4176-4205 (SP-43) Interbedded sandstone and conglomerate, conglomerate shows poorly developed normal grading. 4205-4259 (SP-44) Sandstone, massive, featureless. 4259-4274 (S]-47) Pebbly sandstone overturned by conglomerate, conglomerate is normally graded. 4274-4372 (SP-48) Interbedded sandstone and conglomerate in rough fining upward sequences, conglomerate disorganized or poorly normally-graded, sandstone, featureless to horizontally bedded, good a(i) a(p) lineation in some conglomerate units, interbedded lutite clast conglomerate. 4372-4386 Large rollover fold in classic turbidites. 4386-4515 (SP-49, SP-50) Sandstone and pebbly sandstone interbedded, pebbles show disorganized, normally-graded and inverse graded sequences, beds arranged in fining-upward sequences, beds are lenticular many wedge out within 20 feet. 4515-4702 (SP-51, SP-52, SP-53) Sandstone units 3-10 feet thick separated by siltstone or shale beds 8 "-12" thick, scattered pebbles in sandstone, sandstones arranged in fining-upward sequences. 4702-4728 (SP-53) Massive sandstone bed, pebbly at base, fines upward, generally featureless. 4728-4749 4'-8 ' thick sandstone layers separated by siltstone and shale lenses, fines upward. 4749-4757 (SP-54) Vfg sandstone, v/silty, grades to shale, highly convoluted. 4757-4789 (SP-55) Sandstone, massive, featureless to horizontal bedding, composite unit represents several flows, local lenses of pebbles and eg sand. 4789-4801 Ia b c d e anc* ^BCDE classic turbidites, ave. sandstone unit 10"-28" thick. 4801-4810 Shale. 4810-4929 (SP-56, SP-57) Large sandstone units separated by Tqqjj turbidites or siltstone, sandstone units 5-20 ft. thick. Siltstone and Tgpg turbidite units are 1-6 ft. thick. 4929-4972 Fining-upward sequences of Tg^pg and T^g^pg classic turbidites, sandstone beds 3"-18" thick. 4972-4996 (SP-58) Fining upward sequences of TABCDE anc* ^BCDE with subordinate TcDE turbidites, sandstone beds 3^-2" thick. 4996-5029 Shale, some thin siltstone "Bouma C" layers. 5029-5087 Fining-upward sequence of TQpg and Tgcpg classic turbidites. 358 5087-5112 Shale. 5112-5223 (SP-59) Fining upward sequences of TggDg and T q D£ classic turbidites, interbedded matrix-supported conglomerate-siltstone matrix. 5223-5267 Shale. 5267-5376 (SP-61) Interbedded thick shales (10-30 feet) and siltstones (3-5 feet), siltstones show Tgg bedding, some thin T^Dg classic turbidites in shale, noncyclic sequences. 5376-5387 Covered. 5387-5396 Sandstone - featureless, horizontal and convolute bedding. 5396-5419 Covered. 5419-5449 Sandstone, horizontal to convolute bedding. 5449-5458 Covered. 5458-5492 Thick sandstone units (2-4 feet) separated by thick shales (5-8 feet), some sandstone beds show Tgc anc* TABC bedding, most sandstone is ungraded and featureless. 5492-5525 (SP-62) Sandstone, featureless to horizontally bedded. 5525-5543 Ta b CDE coarsening upward classic turbidites, ss/sh approx. 50%. 5543-5569 (SP-63) Thick sandstone units (5-20 feet thick) separated by shale layers (6-18" thick), fine upwards, sandstone is featureless, some faint horizontal bedding. 5569-5616 Fining upward T^gggg, Ta DE anc^ ^ABDE turbidites, bedding features hard to see. 5616-5638 (SP-64) Sandstone, featureless, massive, some convoluted bedding near top of unit. 5638-5669 Classic turbidites thicker (12"-30") Tgggg sandstone beds separated by bundles of Facies E thin-bedded (ss bed l"-3") T c d e classic turbidites. 5669-5678 (SP-65) Sandstone, massive, featureless. 5678-5720 Shale, grades upward into Tgggg classic turbidites. 5735-5799 (SP-60, SP-67) Large sandstone units (30 ft. thick) separated by shale with thin TBCDE and TcDE turbidites. Sandstones show featureless to horizontal bedding. 5799-5855 Fining-upward sequences of TgcDg and classic turbidites. 5855-5864 Sandstone, featureless except near top of unit where horizontal to wavy bedding is noted. 5864-6280 (SP-68, SP-69, SP-70) Turbidites become increasingly thin bedded up section, several smaller fining-upward sequences, TABCDE and TCDE turbidites at base of interval, dominantly TE£)E turbidites and shale near top. 6280-6332 (SP-71, SP-72) Massive featureless sandstone units (3-10' thick) separated by thin shale units (1"-10"), some sands show TAB bedding. 6332-6376 (SP-73) Sandstone, dish structres, most featureless, some horizontal lamination, some scattered pebbles. 6376-6509 (SP-74, SP-75) Interbedded fining-upward sandstone and shale, thick TABCDE and TgCDE "classic" turbidites. 360 SUCIA ISLAND-A Section measured from northwestern tip of island to far western portion of Echo Bay. Footage Description DECOURCY FORMATION 0-8 (SU-3) Sandstone, cross-bedding alternating with featureless sandstone, sets planar- tabular, 4-6" in height. 8-10 (SU4) Conglomerate, erosive basal contact, cross-bedding along boundaries of channel cut conglomerate disorganized conglomerate in center, ave. pebble size 2.5". 10-13 Pebbly sandstone, grades upward from conglom erate, large very low angle cross-bedding, pebble conc. in lamination. 13-18 (SU-5) Sandstone, large scale cross-bedding, sets 4' in height, trough to planar, 25° dip, overlain by smaller sets 1-1.5 feet thick. 18-29 Cross-bedded sandstone alternates with horizontal bedded sandstone, cross-beds planar and trough, small lenticular conglomerate units, scattered pebbles. 29-36 Conglomerate disorganized, grades upward to cross-bedded and horizontally laminated. Conglomerate, finally to pebbly sandstone. 36-48 Cross-bedded sandstone, sets 6"-4', scour truncation surfaces, scattered conglomerate lenses, large changes along strike. 48-82 (SU-7) Sandstone, very low angle cross-bedding and horizontal lamination, sets 1-3 ft., low angle units, some interbeds of cross-bedding, trough, with dip angle 10-21°. 82-105 Sandstone, trough cross-bedding, sets 8"-2" most trough and tabular planar, overlain by horizontal bedding, some reactivation surfaces. 105-111 (SU-8 ) Sandstone, low angle trough cross-bedding, sets 8"-1.5'. Footage Description 111-142 (SU-9, SU-10) Sandstone alternating cross-bedding and horizontally laminated units, sets 6”-3l, some cross-beds overlying current and combined flow-ripples, some cross-beds separated by reactivation surfaces, some small conglomerate lenses. 142-187 (SU-11, SU-12) Sandstone, cross-bedded sets 6"-3’, large variation in dip angles, both trough and planar cross-bedding noted, some very low angle(<8 °) cross-beds that are planar tabular. 187-189 (SU-13) Conglomerate, lensitic bed, disorganized. 189-217 (SU-14, SU-15) Alternating cross-bedded and hori zontally bedded sandstone, some local conglomerate lenses, some very low angle cross-bedding. 217-224 (SU-16) Siltstone, dark grey, rough horizontal bedding, to well developed oscillatory and com bined flow ripple bedding, poor exposure. 224-228 (SU-17) Sandstone, very poor exposure, covered with marine life, no bedding structures visible. 228-522 Covered. 522-546 (SU-18) Sandstone, cross-bedded, 10-15° dip, sets 10"-20", planar to trough. 546-551 Cross-bedded conglomeratic sandstone, sets 16", trough-tabular, grade upward to smaller and smaller sets, some horizontally laminated sandstone at top of interval. 551-570 (SU-19) Sandstone, horizontally laminated to cross-laminated, large changes along strike. 570-574 Conglomerate, cross-bedded ,grades upward to cross-laminated sandstone, finally to low angle planar cross-bedded, and horizontally laminated sandstone. 574-575 Conglomerate f disorganized to horizontally laminated. 579-639 (SU-20, SU-21, SU-22) Cross-bedded sandstone, rare herringbone cross-bedding, some inter bedded horizontally laminated sandstone, and small conglomerate lenses, some conglomerate lenses show well developed cross-bedding, sets range from 4"-1.5', trough and planar. Footage Description 639-662 (SU-23) Sandstone, small scale trough cross-bedding, sets 3"-8", some congom- eratic sandstone units, sets become more continuous and less lensitic toward top of interval. 662-677 (SU-24) Sandstone, cross-bedded, sets are trough, 8"-24" in height; highly channel ized, some superimposed smaller scale cross-laminae on beds containing larger- scale cross-laminae. 677-700 Sandstone, cross-bedding, planar, low to moderate dip angle, sets 8-20” , some interbedded lenticular conglomerates. 700-705 Conglomerate, disorganized, ave. clast 1.5", largest 5", some interbeds of cross-laminated sandstone, unit is lensitic. 705-719 (SU-25) Siltstone, ripple cross-lamination to small-scale cross-bedding, sets 2- 6", combined flow or current ripple bedding. 719-751 (SU-26, SU-27) Interbedded conglomerate and sandstone, some cross-bedded conglomeratic sandstone, congomerate units are lensitic and are cross-laminated to disorganized, sandstone units are cross-laminated, sets 6-18", trough and planar. 751-783 (SU-28) Sandstone, vfg, horizontally bedded with thin conglomerate trains, some small lenses of cross-laminated sandstone, trough, sets 5-15". 783-784 (SU-29) Disorganized conglomerate, ave. clast 2", largest clast 7". 784-812 (SU-30, SU-31) Sandstone, alternating cross laminated and horizontally-bedded, cross-bed sets 3-5", trough, some scour-fill. 812-831 (SU-32) Conglomerate, disorganized to horizon tally bedded, ave. clast 3", largest clast 11". 831-845 Interbedded sandstone and conglomerate disorganized to horizontally bedded, sand stone cross-bedded, planar, sets 6- 10". Footage Description 845-866 Cross-bedded sandstone, some super imposed ripples, cross-beds, trough, sets 6-10", ripples WL-2-3", Amp. 1/2-5/8”. 866-873 (SU-33) Interbedded conglomerate and sand stone, conglomerate, disorganized, sand stone, cross-laminated, sets 6 "-8", planar. 873-890 (SU-34) Sandstone, horizontal to low angle cross-bedding, sets 1 T— 2..5* feet. 890-898 (SU-35, SU-36) Conglomerate, scattered sand stone lenses, disorganized, ave. clast 3/4"-1.5” largest 3". 898-919 (SU-37) Sandstone, cross-bedded, some herring bone cross-bedding, sets 1 '—2.5*, trough and planar, some low angle cross-bed units are interbedded. 919-928 (SU-38) Conglomerate, disorganized, ave. clast 3", largest clast 8”, small lenses of conglom eratic sandstone. 928-1001 (SU-39, SU-40, SU-41, SU-42) Sandstone,cross bedded, channelized, sets 8”-2 ', trough and planar, some lenticular conglomerate beds, rare beds of ripple-cross-laminated sandstone, ripple are combined flow, large displacement along strike during measurement of this interval. 1001-1014 (SU-43) Conglomeratic sandstone, grades upward to cross-bedded sandstone, sets 1-2 feet, planar and trough, tabular, some reactivation surfaces. 1014-1015 Conglomerate, disorganized, grades upward into cross-laminated conglomeratic sandstone, lenticular, lenses out within 100 feet. 1015-1040 (SU-44) Cross-laminated sandstone, trough, sets l'-S’^some wood fragments in sandstone. 1040-1051 (SU-45) Conglomeratic sandstone, cross-bedded, sets trough, 8"-2.5'. 1051-1075 (SU-46) Sandstone, horizontally laminated. 1075-1093 (SU-47) Sandstone, cross-bedded, scattered conglomerate lenses. Footage Description 1093-1101 Conglomerate, disorganized, ave. clast 1.5", largest clast 5". 1101-1133 (SU-48) Sandstone, cross-laminated, some horizontal lamination. 1133-1139 Conglomerate, irregular erosive basal contact, disorganized, ave. clast 2". SUCIA ISLAND - B Section measured from southeastern tip of Sucia Island to covered region in center of Fossil Bay. Footage Description PROTECTION FORMATION 0-21 (SU-44) Conglomerate, quartz-phyllite, some normal grading, some cross-bedding, sets 2'-4', trough and planar. 21-24 Large boulder conglomerate, up to 18” diameter clasts at top of quartz phyllite unit. 24-41 Covered. CEDAR DISTRICT FORMATION 41-57 (SU-50) Siltstone, featureless to horizontally bedded, rare oscillatory ripple bedding, abundant shelly debris. 57-57.5 Conglomerate lens, siltstone matrix, shell hash. 57.5-78 Silty sandstone, vfg, massive, featureless, Ophiomorpha ?, some ripple cross-lamination, shell-hash. 78-79 (SU-51) Shale lens, limestone concretion in center, shale is silty, shows ripple cross-lamination. 80-111 (SU-51, SU-52) Siltstone to very fine grained sandstone, some horizontal lamination, very foss. , most featureless. 111-114 Shale, sm silt, v/foss. 114-129 Siltstone, featureless, massive, some faint horizontal bedding. 129-133 (SU-53) Vfg sandstone, v/silty, well developed horizontal bedding, grades into featureless massive siltstone, foss. 133-207 (SU-54, SU-55) Siltstone to very fine grained sandstone, featureless, some isolated conglomerate or shell-rich lenses, very foss. 207-212 (SU-56) Siltstone to vfg sandstone, some cross-bedded sets 3", trough, some fg sandstone lenses. 212-276 (SU-57) Vfg sandstone to siltstone, some horizontal bedding, most featureless, some 2-3" thick pebble and shell hash conglomerates, v/foss. 276-277 (SU-58) Graded sequences, mg-cg, sandstone, fines upward to siltstone, v/foss., scattered pebbles in eg sandstone. 277-320 (SU-59) Vfg sandstone to siltstone, featureless, some horizontal bedding, v/foss. 320-320.5 Vfg sandstone to siltstone, oscillatory ripple bedding, WL 2-3", amp 1/4-1/2". 320.5-323 (SU-60) Vfg sandstone, horizontal bedding to faint cross-bedding, shell~hash, conglomerate lenses 1-4" thick and 6-24" in length fill scours. 323-336 (SU-61) Siltstone, horizontal bedding, some small-scale ripple cross-lamination, v/foss. 336-344 Siltstone, low angle planar cross-lamination, sets 8- 1 2". 344-382 Sandstone largely featureless, some faint horizontal bedding and cross-bedding, sets 4-8", trough. 382-387 (SU-62) Vfg sandstone-siltstone, horizontal lamination, some faint oscillatory ripple cross-lamination, some shell-hash, lensitic conglomerates. 387-405 Siltstone becomes increasingly shaly, few bedding features, rare horizontal lamination. 405-610 Shale-siltstone, no bedding features, platy. 610-773 Shale, no bedding features. THETIS ISLAND Section measured east of narrows between Thetis and Kuper Islands, along the south coast of Thetis island. Footage Description CEDAR DISTRICT FORMATION 0-81 (T-l, T-2, T-3, T-A) Fining upward sequences of Tggpg and subordinate T^gggg and Tgpg classic turbidites, scattered facies B sandstone units up to A ft. thick. 81-132 Fining-upward sequences of Tgggg and Tgpg classic turbidites, increase in amount of shale from base of section. 132-188 (T-5) Alternation between series of 3 1—5 ' sandstone bed (facies B) and 3 ”- 8 " shaly intervals which contain Tcde classic turbidites, some sandstone units contain lutite clasts near base of unit. 182-231 Fining upward sequences of Tggg and T q DE classic turbidites. 231-252 Covered. 252-255 Sandstone bed, convoluted, some lutite clasts. 255-26A Covered. 26A-282 (T-6 ) TgCDE turbidites, < 10% shale, fining-upward. 282-298 Largely covered, some TgcDE ant* ^CDE» classic turbidites. 298-301 Sandstone, well developed wavy to horizontal lamination grades from featureless near the base of the unit. 301-325 Fining-upward sequences of Tggpg and T q q £ "classic" turbidites, A0% shale. 325-351 (T-7) Fining upward sequence of thick 1'-51 facies B sandstone beds separated by bundles of Tggg classic turbidites. 351-365 (T-8 ) Fining-upward sequences of TgQg and subordinate TfiCDE classic turbidites. 365-373 Shale, v/silty, convoluted. 368 373-402 Thick 5'-8 ' beds of facies B sandstones separated by thin siltstone units, sandstone shows featureless to wavy and horizontal bedding. 402-404 Shale. 404-411 (T-9) Sandstone, featureless to horizontal bedding. 411-418 Fining upward TBCde and TcDE classic turbidites. 418-431 Shale. 431-470 (T-10) Sandstone beds 3* —7* thick separated by 2"-6" siltstone or shale layers, sandstone featureless to horizontal bedding. 470-488 Covered - some shale. 488-516 (T—11) Sandstone units 2-5' thick separated by large covered areas, sandstones show featureless to horizontal bedding. 516-531 Covered. 531-534 (T-12) Sandstone featureless, abundant lutite clasts.