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Guide to Geology of Central and Southern Vancouver Island: Nanaimo to Victoria
T.S. Hamilton, Steven Earle and David Nelles
Based on: VIU GEOL Guide, EOS 316 Guide (U. Vic.)
& GEOS 100 240 & 260 Guides (Camosun)
Part I : Background on the Geology and Tectonics of Vancouver Island (p. 3 - 10)
Part II: Daily Field Trip Stops (p. 11 – 35)
Day 1: Tuesday June 16; Victoria to Nanaimo
Depart University of Victoria 8:00 AM
Arrive Port Place Mall Nanaimo 9:30 & meet Dr. Steve Earle
Stops between Nanaimo and Nanoose (Steve Earle)
Overnight at Vancouver Island University Dorms
Day 2: Gabriola to Port Renfrew
Depart Vancouver Island University Dorms 7:00 AM
Take Ferry from Nanaimo to Gabriola at 8:05AM
Stops around Gabriola Island (Steve Earle)
Depart Gabriola on 3:05 Ferry
Drive to Pt. Renfrew / & Stops (David Nelles)
Overnight at Big Fish Lodge
Day 3: Port Renfrew to Victoria
Depart Big Fish Lodge 8:00 AM for Botanical Beach (Tark Hamilton & David Nelles)
Stops along West Coast Road
Return to University of Victoria ~ 5:30PM
Day 4: Sidney to Victoria
Depart University of Victoria 8:00 AM
Drive to Deep Cove for ~8:45
Stops between Sidney and Victoria (Tark Hamilton)
Return to University of Victoria
Farewell Barbeque
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Part I: Background Information on the Geology and Tectonics of Vancouver Island
1.0 Introduction
Vancouver Island is situated on the North American plate, below which the Juan de Fuca plate subducts at a rate of <
5 centimetres per year (Fig. 1). The trench is located approximately 200 kilometres offshore, and seismicity related
to the oblique convergence is recorded throughout southern Vancouver Island and the southern British Columbia
Mainland. An extensive geological record of convergent margin processes is exposed in outcrops along roads,
hilltops and shorelines on Vancouver Island. The bedrock geology of the region was first studied by Clapp 1919 who
proposed a stratigraphy and recognized most of the units you are about to visit. This was followed by the work of J.
Muller, C. Yorath, M. Brandon and N. Massey (Brandon, 1989; Brandon et al., 1986; Massey, 1986; Muller, 1983).
Much of the background information for field stops in this guidebook has been gleaned from their work. Some new
interpretations based on more recent work are also given. Interpretations of the present-day crustal structure have
been augmented by geophysical surveys of the first Lithoprobe transect in 1984 (Yorath et al., 1999) and more recent
investigations based on seismic tomography. Since this major mapping effort, BCGS has been actively mapping at
1:50,000 on Vancouver Island (Massey et al. 2005). The Geological Survey of Canada, led by Vaughn Barrie and Kim
Conway at GSC Pacific (PGC) has conducted high resolution multibeam bathymetric and geophysical surveys to
demonstrate the extent of the Gulf Islands Fold and Thrust belt and Tertiary through Modern bounding normal faults
like the Gulf Islands Fault Zone (red below). See Natural Resources Canada website.
Folds in Nanaimo Group: Gulf Islands and Georgia Strait
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Figure 1a – Block diagram showing plate configuration and structure. Also highlighted are significant historical
earthquake locations. (Diagram courtesy of Geological Survey of Canada Pacific website).
Figure 1b –From Fig. 1, Hamilton et al. (2015) showing accurate placement of plate boundaries & deformation, bathymetry and topography
2.0 Geological Background
The Cordillera is a youthful orogen divisible into five morphogeological belts from east to west (Fig. 2): Foreland
(Rockies), Omineca, Intermontane, Coast and Insular (Monger, 1997). Most of the Cordillera in British Columbia west
of the Omineca belt is interpreted as a collage of allochthonous arcs or crustal elements referred to as ‘terranes’
(Coney et al., 1980) that originally formed outboard and then accreted to the continental margin in the Mesozoic
(Monger, 1993).
Many of the terranes are far-travelled, as evidenced by paleontological and/or paleomagnetic data. The magnitude,
timing and sense of motions and the resultant paleogeography of the terranes over the last 150 Ma are vigorously
debated. One view is that the allochthonous terranes were accreted nearly orthogonal to the continental margin by
the late Jurassic (Monger, 1997). Paleolatitudes from paleomagnetic measurements, however, require between
1000 and 3000 kilometres of margin parallel displacement prior to the Eocene, constituting what is referred to as the
‘Baja B.C.’ hypothesis (Irving and Wynne, 1990). Another view is that much of the Cordillera was part of a long ribbon
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continent that during the late Cretaceous has been translated more than 3000 kilometres and bent, possibly in a
series of beams, to form oroclines in much of Yukon and Alaska (Johnston, 2001).
______________________________________________________________________________________________
Figure 2 – The five morphogeological belts of the Cordillera. After (Monger, 1997).
The geological history of southern Vancouver Island is linked to that of the Queen Charlotte Islands (Haida Gwaii) and
southeastern Alaska, all of which are underlain by the Wrangellia Terrane, a part of the Insular Belt. Wrangellia was
one of the originally recognized terranes, and consists of a Devonian arc (Sicker Group), overlain by Permian
limestone (Buttle Lake Group), Triassic oceanic plateau and carbonate reefs (Vancouver Group), and a Jurassic arc
(Bonanza Group), overlapped by a late Cretaceous sedimentary assemblage (Nanaimo Group) (Fig. 3, 4). The Pacific
Rim terrane, a Jura-Cretaceous subduction complex, is interpreted to be thrust beneath Wrangellia (Fig. 5), but
recent observations suggest it may overthrust Wrangellia in the Victoria region. The Crescent terrane is an Eocene
ophiolite or ocean island and is the Cordillera’s youngest terrane, thrust beneath the Pacific Rim terrane between
~55 Ma and 45 Ma. It underlies southern Vancouver Island and outcrops from the Leech River Fault southwards to
the Klamath Mountains in southern Oregon and from the foot of the Cascade Mountains west to the Pacific coast.
Eocene to Miocene marine clastics and molasse of the Carmanah Group (Hesquiat and Escalante Formations to the
NW and Sooke Formation along the Juan de Fuca Strait) overlie the latter two terranes on the western edge of
Vancouver Island as an angular unconformity. Most of the Sooke Formation is about 38 Ma or Oligocene. Quaternary
glacial and alluvial deposits rest with a lesser angular unconformity atop the Sooke Formation.
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The Sicker Group on southern Vancouver Island is mostly immature marine lithic sediments with some sills and rare
augite porphyries. The Myra formation includes felsic arc volcanic, tuffs and domes which locally formed VMS
deposits such as the Myra Falls mine in Northern Strathcona Park (Northcote, 2015). The Katmutsen Formation is
wholly marine mafic pillows and pillow breccias up to 4.5 - 6.2 km thick and interpreted by Barker et al. (1989) to
have arc components. Its extent, thickness and T-Morb chemistry are probably a better fit to LIPs and intraoceanic
plateau. However they do have older arc substrates which does not fit the oceanic plateau model.
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Figure 3 – Sequence of geologic events that formed Wrangellia on southern Vancouver Island (Yorath & Nasmith, 1995).
As shown on the top cross section there is structural deformation, folding and several kilometers of uplift and erosion
marking the accretion of the Insular Superterrane (Wrangellia plus Alexander) prior to 90 Ma. At the time of accretion,
there was an Upper Cretaceous precursor to Vancouver Island including steep bouldery rivers, coal swamps and marine
coastlines. While the Nanaimo as depicted seems to be a simple thermal relaxation basin, the short steep facies from
mountain streams to deep marine turbidite fans show that this is more complex. Also the multiple fining upwards
successions from conglomerates through shales and disconformities show tectonic control and local sediment sources from
Vancouver Island, the Canadian Coast Mountains and the Western Cascades. Older marine members of the Nanaimo
Group are fossiliferous with ammonites, inoceramus, turtles, mosasaurs and elasmosaurs. Terrestrial flora in the coal
bearing facies include tropical gymnosperms and ancestral angiosperms.
The Pacific Rim Terrane, including the West Coast Crystalline Complex and Wark and Colquitz Gneiss outcrops around
downtown Victoria is fault bounded. It has up to garnet amphibolites facies, kyanite staurolite schists and greenschists. On
Saltspring Island and nearby areas there are 386 Ma U-Pb ages for Tyee Granites that intrude the Gneisses. These old high
grade rocks exhibit polyphase folding, considerable structural relief and they are thrust atop the Paleogene Metchosin
Igneous Complex along the Leech River Fault (Fossil Farallon North America Subduction Zone) and overthrust by or
otherwise faulted against Wrangellia with more than 10 km of vertical throw (San Juan Fault, Fulford Burgoyne Fault).
Components of Vancouver Island bedrock include some older volcanic formations: Nitnat and Duck Lake which may be preDevonian (Massey et al., 2005). Internal to the West Coast Complex, the higher grade Wark gneisses are thrust atop the
lower grade Leech River Schist along the Survey Mountain fault exposed in the Goldstream valley. There is no doubt from
Lithoprobe Phase I that this is a tectonic underthrust stack that dips to the north under Vancouver Island and is out of order
in time (oldest gneisses in the middle and youngest Metchosin on the bottom). In this re-assembled stack of crust, it is
possible that the Westcoast Complex is a separate imbricated terrane. Alternatively Canil and others favour that this is the
roots to the middle Jurassic arc. Nonetheless, this metamorphic resetting it is not likely the age of the protolith.
8
E
W
0
Neoge ne
34
Pa leoge ne
( T o f i n o
C a r m a n a h
B a s i n )
G r o u p
C FT B
M I C
65
Nanaimo
Group
Cretace ous
Leech
River
Schist
144
Pa ndora
P eak
Unit
P acific Rim
Melange
ba salt
Jura ssic
?
?
Uclut h
Vo lcanics
Tria ssic
?
Port Renfrew
248
B onanza
Group
Vanco uver
Group
accetion to autochthon
ba salt
206
Pe rmian
L eech River
Tofino
290
San Juan
Sur vey Mtn.
Trial Island
West Coast
Carboniferous
B uttle Lake
Group
354
U. Devonian
Sicker Group
?
370
400
C R E S C E N T
P AC I F I C
R I M
W RA N G E L LI A
Figure 4 – Structure and stratigraphic relationships of units referred to in this field trip.
After (Johnston and Acton, 2003).
Figure 5 – Cross-section of terranes represented in southern Vancouver Island. After (Yorath and Nasmith, 1995).
2.1 Metchosin Igneous Complex, Crescent Terrane
Metchosin Igneous Complex (MIC), part of the Crescent (Siletzia) Terrane, the Cordillera’s youngest accreted terrane
(Fig. 5). This complex is the northernmost part of the Coast Range Volcanic Province that extends southward to
Oregon (Fig. 6). Basaltic lavas in the MIC are tholeiitic and trace element characteristics are transitional E- to NMORB. These rocks correlate with those in the upper parts of the 16 kilometre-thick Dosewallips River section of the
Crescent Terrane on the Olympic Peninsula viewed to the south (Babcock et al., 1992).
The Crescent Terrane is interpreted as a partial ophiolite (Massey, 1986), exposing an upper section of massive basalt
flows, underlain by pillow basalt, sheeted dikes and gabbros (Fig. 7). Sheeted dikes occur only in isolated outcrops
(e.g., Stop 3) and a mantle section is not exposed. Gabbro (Dunite, Norite, Anorthosite) and tonalite to trondjheimite
sills have U-Pb zircon ages of 50 to 56 Ma, similar to Ar-Ar ages of the mafic volcanic rocks. The terrane is interpreted
as an emergent ocean island formed in a marginal basin setting, and underthrust beneath the Pacific Rim Terrane
shortly after it formed (Fig. 5). From the original 56 Ma age of the protolith and deformation ending ~45 Ma, the
ridge system likely lay a similar distance offshore to the Gorda Ridge today.
The volcanic sequence can be subdivided into a lower submarine unit and an upper subaerial unit (Muller, 1977,
1983). The lower unit comprises about 1500 m of pillowed and massive flows with intercalated tuffs, breccia, and
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volcaniclastics. It passes up through well-bedded shallow-water, aquagene tuffs and flow breccias into pillows and
massive flows with occasional intra-flow chert and limestone. The upper unit contains about 1,000 m of
amygdaloidal sheet flows, although tuffs and breccia are found at the top of the exposed sequence, immediately
adjacent to the Leech River fault. The unit is intruded by diabase dikes at its base.
The sheeted dike complex is nearly 100% dikes, with minor screens of gabbro or volcanic rock. Chilled selvedges are
well developed, though commonly not obvious on the outcrop. They are most apparent where lithologic contrast
exists between dikes. The orientation of dikes is generally consistent within individual outcrops but varies regionally.
Dike contacts are mainly vertical throughout the area, with the exception of some late, shallow-dipping, crosscutting
dikes.
49°
Metchosin
Crescent
Black Hills
47°
Grays River
Tillamook
45°
Siletz River
123°
125°
Roseburg
43°
Figure 6 – Map showing regions of Eocene mafic volcanics along the Pacific Northwest whih comprise the Coast Range volcanic province. After
(Duncan, 1982).
Figure 7 – Generalized columnar section of the MIC
A detailed study of the metamorphic history of the volcanics in the complex (Timpa et al., 2005) shows it to increase
in grade westward (Fig. 8). This is possibly due to post emplacement tilting during uplift and erosion. The grade of
metamorphism (up to amphibolite) over this size of section is unlike that observed on current seafloor and
interpreted to have resulted from accretion and post-emplacement metamorphism rather than in situ seafloor
hydrothermal metamorphism (Timpa et al., 2005).
Figure 8 – Temperature contours based on chlorite thermometry applied to mafic metavolcanics in the MIC.
Note higher temperatures (or deeper burial) to the west. After (Timpa et al., 2005).
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2.2 Leech River Complex, Pacific Rim Terrane
The Leech River Complex is part of the Pacific Rim Terrane which was thrust under the Wrangellia Terrane in the
early Tertiary (~55 Ma) along the San Juan fault system (Fig. 5). The Leech River Complex is a sequence of pelites,
sandstones, and volcanic rocks, with minor radiolarian chert and lithic conglomerate. The pelites include slates,
phyllites, and chlorite to staurolite-andalusite-garnet-biotite schists. LRC rocks locally host a suite of tonalitetrondhjemite-granodiorite intrusions of probable Eocene age (Walker Creek Intrusions), a mesocratic, fine-grained
granodiorite of Cretaceous age (Jordan River granitoid) and a mafic intrusive preserved as chlorite-actinolite-garnet
schist bodies (Tripp Creek metabasite, Fig. 9). One such intrusion outcrops in the creek at this stop and shows
foliation parallel to the host-rock schistosity.
The highest grade rocks, located in the Jordan River area, record pressures of 0.15 to 0.35 GPa and temperature
between 500 and 600°C. The protolith for the pelitic rocks was predominately mudstone with discontinuous, thin
sandstone layers. Volcanic rocks occur as discontinuous bodies that range from 0.3 to 0.5 km in length and 2 m to
tens of meters thick. The volcanics have MORB trace element chemistry and are metamorphosed to greenschist and
amphibolite facies assemblages. Two phases of deformation are recognized in the Leech River Complex. Regional,
low pressure metamorphism began during the first stage of deformation and extended into the waning stages of the
second.
The provenance and age of the Leech River complex is poorly constrained. Based on the similarity of the sediment
facies and their Sr-isotopic content to other clastic sedimentary sequences in SW British Columbia and NW
Washington, it has been suggested that the complex is Jurassic-Cretaceous in age (208-66 Ma). Although it is
probable that the sedimentary-volcanic complex accumulated along a convergent margin, it is not possible to
determine a more specific environment. Ar-Ar ages of biotite and muscovite indicate that the latest metamorphism
occurred at 39-45 Ma (Groome et al., 2003).
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2.3 Bonanza Arc, Wrangellia Terrane (from Larocque and Canil, 2010)
The Jurassic Bonanza arc is divided into the West Coast Crystalline Complex, the Island Plutonic Suite, and the
Bonanza Group volcanic rocks (Fig. 10). The West Coast Complex has been interpreted as the deepest preserved
levels of the Jurassic arc (DeBari et al., 1999a; Larocque and Canil, 2010; Canil et al., 2010). The complex contains
mostly fine grained to pegmatitic quartz diorite, diorite and gabbro with varying amounts of hornblende, biotite,
orthopyroxene and clinopyroxene. Strain is heterogeneous and the rock can grade from gneissic to massive at the
outcrop scale, especially in the Victoria area, where this unit has historically been divided into the ‘Wark Diorite’ and
‘Colquitz Gneiss’(Muller, 1983). Foliated diorite can be crosscut by intrusions of more homogeneous phaneritic
granodiorite and monzonite with enclaves of mafic schlieren. The West Coast Complex also contains rare
discontinuous bodies of cumulate-textured peridotite and pyroxenite (Larocque and Canil, 2010; Marshall et al.,
2007).
The Island Plutonic Suite occurs as a series of roughly northwest-aligned unfoliated plutons ranging in composition
from quartz diorite to alkali feldspar granite. The contact between the Island Plutonic Suite and the West Coast
Complex is not defined. The intrusive rocks of both suites in places contain decameter-thick septa of marble and
related diopside-garnet-magnetite skarn.
The Bonanza volcanic rocks form the uppermost component of the Bonanza arc and vary from pillowed and massive
flows of aphanitic basalt, through plagioclase-, pyroxene-, and/or hornblende-phyric andesite, to dacite. Pyroclastic
deposits are well exposed, with aphanitic felsic and mafic ash flows and fall deposits. On northern Vancouver Island,
the volcanics show an older subaqueous phase leading to a subaerial phase presumably marking when the Bonanza
arc became emergent (Nixon and Orr, 2007).
The Bonanza arc was active for ~ 40 Ma between 202 and 168 Ma, based on U-Pb zircon age dating (Nixon and Orr,
2007). Ages of Bonanza volcanic rocks overlap those of the plutonic rocks in both the West Coast Complex and Island
Plutonic Suite, supporting the idea that all three of these units are contemporaneous and co-magmatic (Canil et al.,
2013). There is a weak trend of younger ages in plutonic rocks toward the east on Vancouver Island (Canil et al.,
2013). Younger Jurassic Intrusions exist but so do older substrates. To be true to map relations, the lower WCC
should be labeled IPS and both should sit in tectonic contact against WCC.
Figure 10 – Simplified stratigraphic section for southern Vancouver Island. WCC = West Coast Crystalline Complex; IPS = Island Plutonic Suite.
(Larocque and Canil, 2006).
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Part II: Brief Descriptions of Field Stops
Day 1 (depart Victoria at 8:00 AM arrive Nanaimo at 9:30, proceed to Nanoose)
1) Fairwinds Rec. Centre: Island Intrusive granodiorite (to 10:30)
2) Blueback Drive: Nanoose Complex pillow basalts and limestone (to 11:00)
3) Cottam Pt.: Nanoose chert and Comox Fm. unconformity (to 12:00)
4) Stephenson Point: Karmutsen Fm. and and Comox Fm. unconformity plus lunch (12:30 to 2:30)
5) Malaspina Cut: Karmutsen Fm. and and Comox Fm. unconformity (to 3:15)
6) VIU: giant Palm Frond (Protection Fm) (to 3:45)
7) Cranberry Arms: dicot fossil site (Protection Fm) (to 4:45)
8) Cavan Street : coal and sandstone (Protection Fm) to 5:45
Paleozoic and Mesozoic rocks of the Nanaimo area Central Vancouver Island
Steven Earle, Vancouver Island University
The objective is to examine some of the older rocks (Devonian to Jurassic) of the Wrangellia Terrane and the
overlying sedimentary rocks of the late Cretaceous Nanaimo Group. The recognition of the Wrangellia
Terrane is based on this fundamental tectono-stratigraphic package. While we will look at typical
stratigraphy, this piece of crust has numerous economic mineral deposits. Coals of the basal Nanaimo Group
were the main driver for European settlement and economic development and continue to be mined at
Quinsam (Cathyl-Bickford, 2001; Kenyon et al., 1991). Coal bed Methane is also a significant economic
resource in the Comox Basin (Cathyl-Bickford et al, 1991). VMS (volcanogenic massive sulphide deposits in
the Myra Formation of the Sicker Group are mined for Zn-Cu-Ag-Au (Ruks and Mortensen, 2007).
Historically the contacts between Jurassic Island Intrusions and limestone have been exploited for Cu-Fe
skarn and Cu-porphyry deposits as well as Paleogene intrusions such as on Mt. Washington. The Cu source
for all of these is the Triassic Karmutsen Formation (Barker et al, 1989; Greene et al, 2009) with > 200ppm
Cu. Limestone for cement and aggregates from glacial outwash are also widely exploited
Wrangellia
The Wrangellia Terrane is made up of Devonian to Jurassic rocks that formed as part of a Panthalassic
Ocean island, originally south of the equator, and was accreted to the western edge of North America at
between 100 and 90 Ma. The oldest rocks are part of the Devonian Sicker Group, which includes pillow
basalts, volcaniclastic rocks, and minor limestone and chert. The most abundant rock type on Vancouver
Island is the Triassic-age Karmutsen Formation, an ocean island basalt (plateau) sequence that is several
thousand m thick. Barker et al. (1989) favours a back arc setting while Greene et al. (2009) point out LIPOceanic Plateau similarities. One of the problems is the difficulty in the field of distinguishing older basalts
of the Karmutsen from younger mafic basaltic andesites (SiO2 > 54%) of the Bonanza. This is overlain by
several hundred m of Quatsino Formation limestone. All of these rocks were intruded during Middle
Jurassic by the Island arc-related granodioritic Island Intrusions and overlain by coeval Bonanza volcanics.
Just as Vancouver Island has basalts of 5 different ages to distinguish, map and interpret correctly, there are
intermediate plutons of 4 different ages: Devonian (Tyee = roots of Sicker arc), Jurassic Island Intrusions (=
Bonanza arc), Oligocene (Catface, Mt.Washington) and Miocene (Brooks Peninsula = Alert Bay, Masset
equivalent) to tell apart. This type of geological setting is nothing if not job security for generations to come!
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On Vancouver Island, the late Cretaceous Nanaimo Group clastic sedimentary sequence has an angular
unconformity at its base atop the Wrangellian rocks. There are both terrestrial and marine successions with
tectonic controls on the sedimentation and structural deformation as described in more detail below.
On the first part of Day 1 we’ll be looking at bedrock outcrops in the Nanoose area north of Nanaimo. The
rocks of this region have been described as the Nanoose Complex by Yorath et al. (1999). They are similar
in many ways to the Sicker Group rocks of central Vancouver Island (Greene et al 2009, Massey et al, 2005,
but have some distinctive features.
Geology of the Nanoose Peninsula and locations of stops 1 to 3.
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Vertical schematic of the Geology of the Nanaimo (from Geoscape Nanaimo) (Upper Left)
Older rocks of the Wrangellia Terrane form the foundation of Vancouver Island. They are overlain (along
the eastern edge) by the Nanaimo Group sedimentary rocks. More recent silt, sand, gravel and till, mostly of
glacial origin, form widespread cover. We will see only stop locations 1, 2 and 3.
Day 1 Stop 1 Granodiorite at the Fairwinds Recreation Centre (Jurassic ~ 180 Ma) (Upper Right)
Long before Wrangellia reached the edge of North America it was primarily made up of the volcanic rocks,
including the sea-floor pillow basalts that we’ll see at the next 3 stops, and was mostly or entirely below sea
level. At around 180 Ma Pan-Thallassic oceanic crust was subducted beneath Wrangellia. This led to the
production of magma and to formation of Jurassic sub-aerial volcanic rocks (Bonanza Group) that are not
preserved in this part of Vancouver Island. The magma chambers that fed the Jurassic volcanoes cooled to
become granitic bodies like those exposed in the Fairwinds area. There are dykes of more mafic material
that cut through the granodiorite.
The plate interactions and magmatic activity during the Jurassic contributed to the uplift of Wrangellia, and
by the end of this period much more of it was exposed above sea level. Several dark dykes, also made of
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igneous rocks, cross-cut these granitic rocks. The age of these dykes isn’t known, but they are obviously
younger than the granite. The dykes are finer-grained than the granite, and have a higher proportion of dark
minerals (probably mostly hornblende). There is more of this granitic rock exposed between here and the
next stop.
Day 1 Stop 2 Sea-floor volcanic rock and limestone at Blueback Drive in Nanoose (Devonian ) (Lower
Left)
On the beach at Blueback Drive we can see some good examples of pillowed basalts. The pillows are easily
visible as they have slightly finer textures around their edges than in the middle. Some of the rock is
strongly porphyritic, with phenocrysts up to 2 mm of feldspar and pyroxene.
The pillow basalts are cut by mafic dykes with well-developed child margins.
Although not exposed in outcrop on this beach, there are some large fragments of limestone, interbedded
with chert, which have tumbled down from the steep slope on the other side of the road.
Day 1 Stop 3 Nanaimo Group unconformity on Sicker Group at Cottam Point (Cretaceous, ~ 90 Ma)
(Lower Right)
The sedimentary rocks here, which were deposited along an ancient shoreline, are part of the oldest of the 11
formations of the Nanaimo Group—the Comox Formation—and they rest directly on chert of the Nanoose
Complex. Although not observed here, limestone is included as large clasts in the lowermost Comox
Formation.
The lowest Nanaimo Group layer is conglomerate, ranging from one to several metres in thickness, and it is
mostly comprised of pebble- to boulder-sized clasts of various rock types (including chert). It is likely that
the sediments that make up this rock were deposited in a debris-flow environment, near to the base of a steep
slope, and not far from the shoreline.
The conglomerate is overlain by brown sandstone, which fines up-section. There are some marine fossils at
this location which we may have time to go see.
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The rocks of the Nanaimo Group were deformed and thrust up onto Vancouver Island during the Eocene, as
a result of collisions along the west and southwestern parts of Vancouver Island. Two separate phases of
convergence occurred at ~55 and ~42 Ma.
The Nanaimo Group is important for coal deposits in the Nanaimo area and at various locations to the north,
as far as Campbell River. Coal was mined around Nanaimo for approximately 100 years from 1850 to 1950.
There is still one operating coal mine near to Campbell River and there are ongoing efforts to develop new
mines south of Campbell River.
The Nanaimo Group also forms an important aquifer for many parts of Vancouver Island and for all of the
Gulf Islands. The least cemented sandstones and coals with abundant cleats tend to be the most productive.
Day 1 Stop 4 Karmutsen Formation volcanic rock (Triassic, ~ 210 Ma) and Comox Fm. sediments at
Stephenson Point (Cretaceous, ~ 90 Ma) (omit this stop)
At Stephenson Point we can see some unique lithologies within the Comox Formation, of the Nanaimo
Group, and also see some of the pillow basalts of the underlying Triassic Karmutsen Formation.
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The Triassic Karmutsen Rock here is quite similar to the much older (Devonian) Nanoose Complex basalt at
Blueback Dr., although it is not as dark (more strongly altered). There are some excellent pillows exposed in
some of the large boulders on the shore, and in outcrops.
The lowest Comox Fm. layer is conglomerate, ranging from one to several metres in thickness, and it is
mostly comprised of pebble- to cobble-sized clasts of Karmutsen basalt. These are well rounded, and, in
places, quite well sorted. The conglomerate is overlain by a bed of cream-coloured limestone that is up to a
few metres thick, and is almost entirely composed of 1 to 3 mm sized fragments of coralline algae. This
material likely accumulated in a beach or shallow marine shelf environment. The limestone is succeeded by
dark green calcareous sandstone that is rich in marine fossils. Look for examples of oysters, trigonia
bivalves, inoceramas clams and crinoids. Thalassanoides trace fossils are common at the interface between
the coraline-aglae limestone and the green calcareous sandstone.
Day 1 Stop 5 Karmutsen Formation volcanic rock (Triassic, ~ 210 Ma) and Comox Formation
sediments at the Malaspina Cut (Cretaceous, ~ 90 Ma)
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Although this is the same geological setting as stop 4, there are some unique features at this site, and it is a
good place to discuss some of the research that has been done here into the Baja BC hypothesis. Magnetic
orientation data from this site, which span the end of the Cretaceous Long Normal (Magnetic chron 34), have
been used to suggest that these rocks were deposited about 20˚ S of their current location close to southern
California from flatter inclinations than Vancouver Island has today (Enkin et al., 2001). The Nanaimo
Group is all Upper Cretaceous with the oldest section being Middle Turonian from mollusk fossils on Sidney
Island (Haggart et al.; 2005). Here the basal Nanaimo is Coniacian and the boundary with the Santonian
occurs in this outcrop from the paleomagnetic information. Inoceramus occurs in the lowest sandstones. See
how well you can do at distinguishing the underlying Karmutsen breccias from the basal Nanaimo
Conglomerates. Could you find this contact if you were drilling or chip/core logging? Could you train a
student how to do this?
Day 1 Stop 6 Giant palm frond at Vancouver Island University (no photo)
We will stop to view a large (~2 m diameter) palm frond (Phoenicities imperialis) from the Protection
Formation of the Nanaimo Gp., on display outside the Earth Science Department at Vancouver Island
University. What was the controlling factor for palms growing here: tectonic translation or a warmer
climate?
Day 1 Stop 7 Cranberry Arms fossil site (Protection Fm., ca 70 Ma)
The Cranberry Arms fossil location is situated within a backwater/oxbow mudstone within the fluvial
Protection Fm. sandstone. The assemblage is wide-ranging (ferns, gymnosperms, palms) but is dominated
by dicots. A collection of leaves from approximately 35 different types of dicots has been used for a leaf
morphology analysis of paleoclimate. The apparent Cretaceous mean annual temperature (MAT) is between
15 and 20˚ C. The current MAT for Vancouver Island is 12˚ C, while that for southern California is close to
18˚ C. Considering that late Cretaceous global temperatures were as much as 6˚ C warmer than today’s
climate, a Cretaceous MAT of 15 to 20˚ C is not consistent with a position as far south as southern California
(Pearson and Hebda, 2006).
Day 1 Stop 8 Cavan Street parkade (Protection Fm., ca 70 Ma)
Fluvial sediments of the Protection Fm. are exposed in a parking lot in downtown Nanaimo. These include a
coarse sandstone (1), a thin (~50 cm) coal seam (2) and an overlying finer sandstone (3).
There is evidence of an angular unconformity between the lower sandstone and the coal. This is important
because it is evidence of tectonic activity within the period of Nanaimo Group deposition. Other evidence is
the repetitive upward fining cycles of conglomerate through shales at times which do not correlate with
major eustatic changes, in fact most of the Cretaceous had pretty warm sea water but global land area
gradually increased through Upper Cretaceous (falling sea level from 1st order supercycle post 80 Ma).
Other more indirect evidence is the short steep nature of some of the facies transitions needing considerable
relief in and adjacent to the basin and active thrusts (England and Calon, 1991; Monger and Journay, 1994).
Further up Island near Trent River and Mount Washington there are clastic dykes of sandstone < 1 m wide
cutting shales over 10’s of metres of section. Generally this is an indicator of liquefaction during seismic
shaking. The main Comox Formation Dunsmuir level coal near Quansam Mine include tonsteins and a coal
that was probably a tsunami deposit in a barrier lagoon (Cathyl-Bickford, 2001; Kenyon et al. 1991).
Whether you like the little unconformity here or the academic discussion, it probably wasn’t entirely a
quiescent 25 Ma period!
The upper six formations of the Nanaimo Group are marine continental slope and shelf deposits (submarine
fan - SMF). On Gabriola Island we can see good examples of various SMF facies, including the outer fan
Spray and Northumberland Formations, and the channel or inner fan Geoffrey and Gabriola Formations. The
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coarse conglomerates could be either proximal fan turbidites or lags. The Gabriola Fm. is the uppermost unit
of the Nanaimo Gp. It is essentially devoid of macrofossils. Some microfossils have been recovered but
their ages are ambiguous. While it is thought to be uppermost Cretaceous (Maastrichtian) there is little
evidence to prove that the upper part is not Paleocene (Danian) in age.
For more on Cretaceous passive margin sea level history from coastal New Jersey, see Miller et al., (2003)
below. Normally Highstand System Tract (HST) periods are maximum flooding surfaces with widespread
shale facies. This supplies load to underlying sediments and can destabilize steep continental slopes. The
sediment delivery picks up during the subsequent Falling System Tract (FST) the basin margin recedes and
sediments are worked down basin so this in deep sea facies marks the beginning of a new cycle of
conglomerates in canyons and proximal deep sea fans. In contrast lag conglomerates are produced in stable
shelf environments during Lowstand Systems Tracts (LST) as there is reworking but little renewal of
sediment supply. These conglomerates tend to be better rounded and have storm shelf sedimentary structures
like hummocky cross stratification.
To have the 11 formations of the Nanaimo Group correspond to second order Global Eustatic cycles would
require that every one of the FST bumps (big or small) control a cycle of sedimentation and that the timing
not agree well with the fossil ties for local strata in the Nanaimo Basin. Look at the rocks and play with the
graph and argue amongst yourselves as to whether eustasy or tectonics wins the day.
End Day 1. Go to Vancouver Island University Dorms for ~6 PM. Be sure to pack up at night for a hasty
departure at 7 AM as we will not be back.
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Day 2 Leave VUI dorm parking lot at 7:00 AM sharp to line up for the Gabriola ferry from
downtown Nanaimo at 8:05 AM. We will hurriedly go to the Mall to find take-away breakfast and
pick up lunch from Thrifty Foods and marshall at the vans in the Ferry Terminal by 7:35.)
1) Descanso Bay: Spray Formation and Spray-Gabriola contact at (9:00 to 9:30)
2) Brickyard hill: Geoffrey Fm. (to 10:00)
3) Gabriola cemetery: Northumberland Fm. (to 10:30)
4) Lock Bay: Spray and Spray-Geoffrey contact plus walk to Gabriola contact, plus lunch (10:45 to 12:30)
5) Malaspina Galleries: Gabriola Fm. & Gabriola groundwater until 2:30 (3:05 ferry). Thank Steve!
6) Drive across Vancouver Island to Port Renfrew with Stops 7a , 7b & Gordon River Bridge.
7) Check into Big Fish Lodge ~6:30PM and rally for dinner at the pub for 7:30 PM.
Location Map of Field Stops on Gabriola Island
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Day 2 Stop 1 Spray and Gabriola Formations at Descanso Bay
Spray Formation turbidites (Outer fan, Tcde), with some sandy layers and with clastic dykes, are exposed in
a road cut. Examine their contacts and discuss their origin. The Spray Formation is overlain by channel deposited (Submarine Fan (SF) facies B) sandstone. The sandstone in this area has been quarried for pulpindustry millstones.
Day 2 Stop 2 Geoffrey Formation conglomerate on Brickyard Hill
The Geoffrey Fm. comprises the impressive cliffs that you might have seen on the southern side of Gabriola
during your approach on the ferry. It is a mixture of conglomerate and sandstone (SF facies A). At this
location both ortho- and para-conglomerates are present. The cobbles are of diverse lithologies, although
they are dominated by basalt and granodiorite. Pink quartzite clasts are also present in the Geoffrey Fm.,
and the only possible source of these in western North America is the Canadian part of the Rockies. This
places further constraints on how far south the Nanaimo basin might have been during deposition. The road
is very narrow at this site. Please exercise caution.
Day 2 Stop 3 Northumberland formation mudstone at the Gabriola cemetery
The Northumberland Formation is exposed in cliffs and a wave-cut platform on the southeastern edge of
Gabriola Island. It is consistently fine-grained (more so than the Spray Fm.), and contains large, but poor
quality Inoceramus clams and numerous fodichnia trace fossils of horizontal grazing behaviour from in-situ
deposit feeders probably indicate shelf depths.
Day 2 Stop 4 Geoffrey, Spray and Gabriola Formations at Lock Bay
Northumberland Fm. mudstone was quarried at the base of Brickyard Hill and used to make bricks on site.
The bricks were fired using Nanaimo coal and shipped to Nanaimo using the same barges that had been used
to transport the coal.
At Lock Bay we can see the uppermost part of the Geoffrey Fm., here a sandstone with minor lenses of
gravelly conglomerate. This is overlain by Spray Fm. middle fan turbidites showing complete Bouma
Sequences (Tabcde). We will walk along the shore through the entire ~300 m thickness of the formation and
into the lower part of the Gabriola Formation. Tafoni and honeycomb weathering are common along this
part of the shore. Examine these unusual forms and try to reason how they are formed in this changeable
foreshore environment.
Be sure to thank Steve Earle for putting together this great 2 day field trip to Central Vancouver
Island, especially since he had to put up with Tark’s editing and interpretations!
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Partial References For Days 1 & 2 especially Nanaimo Area and Nanaimo Group Rocks:
Information on the geology of the Nanaimo area is available at the Geoscape Nanaimo website:
http://web.viu.ca/geoscape/
The geology of the Nanoose area is described in: Yorath, C; Sutherland Brown, A; Massey, N, 1999,
LITHOPROBE, southern Vancouver Island, British Columbia. Geological Survey of Canada, Bulletin 498,
145 p.
Aspects of Nanaimo Group rocks are described in:
Barker, F., Sutherland-Brown A., Budahn, J.R. and Plafker, G. 1989. Back-arc with frontal-arc component
origin of Triassic Karmutsen basalt, British Columbia, Canada, Chemical Geology, Volume 75, Issue:1-2,
81-102, DOI:10.1016/0009-2541(89)90022-3,
Cathyl-Bickford, C.G. (2001): Lithostratigraphy of the Comox and Trent River formations in the Comox
coalfield, Vancouver Island (92F/7, 10, 11, 14); B.C. Ministry of Energy, Mines and Petroleum Resources,
Paper 2001-1, pages 363–370.
Cathyl-Bickford, C.G. (1991): Coal geology and coalbed methane potential of the Comox and Nanaimo
coalfields, Vancouver Island, British Columbia; in Coalbed Methane of Western North America, Rocky
Mountain Association of Geologists, pages 155–162.
Earle, S. and Krogh, E., 2006, Elevated fluoride and boron levels in groundwater from the Nanaimo group,
Vancouver Island, Canada. Sea to Sky Geotechnique 2006: Proceedings of 59th Canadian Geotechnical
Conference and 7th Joint CGS/IAH Groundwater Specialty Conference, 1584–1591
England, T.D.J., and Calon, T.J. (1991): The Cowichan fold and thrust system, Vancouver Island,
Southwestern British Columbia; Geological Society of America Bulletin, Volume 103, pages 336–362.
Enkin, R, Baker, J, and Mustard P, 2001, Paleomagnetism of the Upper Cretaceous Nanaimo Group,
southwestern Canadian Cordillera, Can. J. Earth Sci., V. 38: p. 1403–1422
Greene, A.R., Scoates, J.S., Weis, D., Nixon, G.T. and Kieffer, B. 2009. Melting History and Magmatic
Evolution of Basalts and Picrites from the Accreted Wrangellia Oceanic Plateau, Vancouver Island, Canada,
Journal of Petrology 10.1093/petrology/egp008
Haggart, J. W., Ward, P.D., and Orr, Wm. 2005. Turonian (Upper Cretaceous) lithostratigraphy and
biochronology, southern Gulf Islands, British Columbia, and northern San Juan Islands, Washington State,
Canadian Journal of Earth Sciences, 42(11): 2001-2020, 10.1139/e05-066
Katnick, D and Mustard, P, 2003, Geology of Denman and Hornby islands, British Columbia: implications
for Nanaimo Basin evolution and formal definition of the Geoffrey and Spray formations, Upper Cretaceous
Nanaimo Group, Canadian Journal of Earth Sciences, 2003, 40(3): 375-393
Kenyon, C., Cathyl-Bickford, C.G., and Hoffman, G. (1991): Quinsam and Chute Creek coal deposits (NTS
92F/13, 14); British Columbia Ministry of Energy, Mines and Petroleum Resources, Paper 1991-3
Massey NWD, MacIntyre DG, Desjardins PJ, Cooney RT. Digital Geology Map of British Columbia: Tile
NM10 Southwest B.C. British Columbia Ministry of Energy and Mines Geofile 2005b;2005-3.
Miller, K.G., Sugarman, P.J., Browning, J.V., Kominz, M.A., Olsson, R.K., Feigenson, M.D. and
Hernández, J.C. 2003. Upper Cretaceous sequences and sea-level history, New Jersey Coastal Plain, Geol.
Soc. Am. Bull., v. 116 no. 3-4 p. 368-393. doi: 10.1130/B25279.1
23
Monger JWH, Journeay JM. Basement geology and tectonic evolution of the Vancouver region. In: Monger
JWH, editor. Geology and Geological Hazards of the Vancouver Region, Southwestern British Columbia.
Geological Survey of Canada Bulletin. Vol. 481. 1994. p. 3-25.
Muller, J.E. and Jeletzky, J.A. 1970. Geology of the Upper Cretaceous Nanaimo Group, Vancouver Island
and Gulf Islands, British Columbia, Canada, Geological Survey of Canada Paper, 69-25, 77p.
Mustard, P, 1994, The Upper Cretaceous Nanaimo Group, Georgia Basin: In Geology and Geological
Hazards of the Vancouver Region, SW British Columbia, J. Monger (ed), Geol. Surv. of Canada, Bulletin
481, p. 27-95.
Pearson, J., and Hebda, R.J. 2006. Paleoclimate of the Late Cretaceous Cranberry Arms flora of Vancouver
Island: evidence for latitudinal displacement. In Paleogeography of the North American Cordillera: evidence
for and against large-scale displacements. Edited by J. Haggart, R.J. Enkin, and J.W.H. Monger. Geological
Association of Canada Special Paper 46. pp. 133–145.
Ruks, T. and Mortensen, J.K. 2007. Geological Setting of Volcanogenic Massive Sulphide Occurrences in
the. Middle Paleozoic Sicker Group of the Southeastern Cowichan Lake Uplift. (NTS 092B/13), Southern
Vancouver Island. In: Geological Fieldwork 2006, p.381-394. GBC Contribution 035.
Some of the fossils of Vancouver Island are summarized on the following poster: Johnstone, S, 2013.
Fossils of Vancouver Island at: http://www2.viu.ca/earthscience/fossilsofvancouverisland.pdf
Day 2: Continued Gabriola to Port Renfrew & Day 3 Stops (David Nelles and Tark Hamilton)
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Acknowledgments –The observations summarized in Days 2-3 of this guidebook on southern Vancouver Island are
based on contributions by Gary Pearson and Perry Heatherington of Port Renfrew, Nick Massey of the BCGS, Wes
Groome of the University of Maine and students and faculty at UVic, including Jeff Larocque, Sean Timpa, Jeff Kyba,
Dante Canil, Stephen Johnston, Laurence Coogan and Kathy Gillis as well as Dr. Alan Gell (Camosun, retired) and
previous field guides: VIU GEOL Guide, EOS 316 Guide (U. Vic.) & GEOS 100 240 & 260 Guides (Camosun). Photos for
Sooke Fomation by Dr. Daniel Donnecke (Camosun).
Stops 7A, B
Gordon River Mainline approximately 4:45PM
Brief Stop Descriptions: (Stops 7 – 10 are in various units in the Wrangellia Terrane)
Stop 10 – Lens Road (UTM 416557, 5397461) (Skip this stop)
The Island Plutonic Suite represents the upper plutonic levels of the Bonanza Arc and intrudes the Vancouver Group
at depths of 2 to 10 km (Canil et al., 2010). These rocks are phaneritic and show clear cross cutting contacts typical of
epizonal (upper crustal) plutons. From regional gravity and magnetic maps in the national geophysical data base,
these map extents are minimal and most groups of plutons seem to broaden and coalesce at depth to larger
continuous stocks. This is significant for crustal level heat engines, mineralization and exploration strategies.
Stop 9A, B – Hillcrest Mainline Switchback (UTM 410891, 5395736; 411115, 5395936) (Skip this stop)
The volcanic section of the Bonanza Arc consists of a small section of heterogeneous tuffs (consolidated volcanic
ash), agglomerates (coarse accumulations of large blocks of volcanic material) and breccias (broken fragments of
minerals or rocks in an aphanitic matrix). Two outcrops show evidence for brecciation and, local overprinting by
hydrothermal metamorphism.
Stop 8 – Harris Creek Mainline (UTM 410540, 5394592) (Skip this stop)
Vancouver Group rocks, include limestone belonging to the Triassic Quatsino Formation and the volcanic rocks
assigned to the Triassic Karmutsen Formation.
Stop 7A, B – Gordon River Mainline (UTM 393812, 5385275; 394311, 5385972)
The Jurassic part of the West Coast Crystalline Complex (WCCC), interpreted as the deeper (> 10 km) mid-crustal
plutonic roots of the Bonanza Arc. Iintrusive igneous rocks associated with the Bonanza Arc, metamorphism that
occurred as a consequence of the intrusions, are both present as is some of the older (Paleozoic) country rock on
which the Bonanza Arc is built.
Proceed to Big Fish Lodge for the night. We should have time to clean up for dinner at the
pub. This is a private residence as well as a guest house. Please treat it and Bonnie the
owner respectfully (or you may not like your breakfast and lunch tomorrow!) Rumour has it
that several ill behaved geochemists in the last Goldschmidt conference had to be cut up
and used to chum for halibut! Pack up at night as we will leave right after breakfast at about
8:30 AM to take advantage of the low tides.
Day 3: Port Renfrew to Victoria (David Nelles and Tark Hamilton)
8:30 AM - Depart Big Fish Lodge and proceed to East beach access trail head for Botanical
Beach, Stop 11.
10:30 Stop 6, Minute Creek
11:00 Loss Creek Bailey Bridge, Stop 12
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11:25 Jordan River Delta (Drive by or outhouses available)
11:45 Stop 13, Sooke Formation near Shirley
12:00 Stop 14,Trondjheimites, Henlyn Road
12:25 Stop 15, Alyard Farm –East Sooke Park (1.5 – 2 hours)
3:00 Stop 1, Tower Point Park, Witty’s Lagoon (30 minutes)
Return to University of Victoria (~5-5:30pm)
I. Background for Geology and Stratigraphy of Day 3
The Sooke Formation (Late Eocene to Oligocene)
Along the West Coast of North America, and a short distance eastwards onto the continent are a series of small
Tertiary Basins. There are two dominant ages: Middle to Late Eocene like the volcanic rocks of the Metchosin Igneous
Complex, and Oligocene to Early Miocene. Along the edge of Vancouver Island sediments of this latter episode are
called the Tertiary Carmanah Group comprising the Hesquiat Formation north of Port Renfrew and the Sooke
Formation to the south and East. There are also vast thicknesses of equivalent aged strata in the Olympic Mountains
of Washington and west of the Cascades in western Oregon. You may have already seen the Sooke Formation in East
Sooke Park and at Muir Creek. It occurs sporadically along the coast of the Juan de Fuca Strait and forms many of the
intertidal exposures of sandstones and conglomerates from East Sooke Park all the way to Botanical Beach. We will
see coastal and shallow marine facies. These coarse clastic rocks are porous, permeable and partially cemented by
calcite and iron oxy-hydroxides and appears as buff to grey beds up to several meters in thickness. The Sooke
Formation rests upon either the Metchosin Igneous Complex (MIC) or the Leech River Complex (LRC) with an angular
unconformity. As such it is an overlap or successor basin that postdates the accretion of the seafloor rocks of the
Farallon plate (the Siletzia Terrane) from southern Vancouver Island to Mendocino Califormia.
Marine fossils of gastropods, pelecypods, oysters are common as is coalified and teredo bored wood. The oldest
known ancestor to all of the toothed whales and dolphins (Chonecetus sookensis) was found in correlated coastal
exposures, as originally reported by Russell (1968). In a more recent article, (Barnes et al, 1994) described this as the
most primitive North American aetiocetid. A more derived, Late Oligocene species, Chonecetus goedertorum Barnes
and Furusawa, new species, from the Late Oligocene Pysht Formation, Olympic Peninsula, Washington, has the
primitive placental mammalian tooth count of 11/11. While baleen whales were quite diverse at this time, the
Oligocene still shrouds the mysterious origin of the toothed whales.
The largest expanse of these rocks underlies the length of the Juan de Fuca Strait as a East-West trending
synclinorium holding up to 1.4 kilometre thickness of sedimentary section, as imaged by seismic reflection profiles.
An offshore exploration program by Shell in the 1960’s determined these formations to be too thin and thermally
undermature to have generated commercial conventional hydrocarbons. On Southern Vancouver Island, the Sooke
Formation occurs generally in small basins which are now tectonically and erosionally isolated. The largest basin is
around Muir Creek and is drained by Tugwell, Muir, and Kirby Creeks. At these sites the contact with the underlying
MIC is not exposed. The best exposures occur along the coast and up the short coastal streams. Elsewhere the rocks
are covered with glacial and deglacial deposits of both late Wisconsinan and undatably old, Pre-Wisconsinan age.
The sandstone contains angular to subrounded grains composed mainly of quartz, plagioclase feldspar and magnetite
and lithic clasts of MIC south of the Leech River fault. Conglomerates are considerably more variable in their
composition. North of the Leech River Fault large clasts are mainly of Leech River metamorphic origin but are of more
diverse provenance than to the south of the fault, including many lithologies of the Wrangellian terrane to the north
of the San Juan Fault. Accessory minerals are biotite, muscovite, hornblende and limonite around Muir Creek. The
26
cement is mainly calcite. Teredo bored driftwood logs occur at the Muir Creek fossil site. The Kirby Creek exposed
section is about 160 m thick and the Muir Creek section about 130 m. Clapp reports that a bore hole at the mouth of
Muir Creek was still in Sooke Formation 450 m below present sea level so this panel of crust has Neogene folding and
faulting.
The formation was deposited in a marine environment of a steep shoreline of resistant crystalline rocks. The Tertiary
coastline comprised promontories of MIC, which supplied large clasts to form the conglomerate. Between the
promontories were coves and bays in some of which accumulated sands. The coastline was probably similar to that
of today. Driftwood buried by the sands has been converted to lignite. Offshore facies are also recognized by
sedimentary structures and fossil content. In the Olympic Mountains, equivalent age strata range from shallow
neritic sands and conglomerates to bathyal turbidite and mélange facies. There they contain clasts derived from the
north on Vancouver Island and from the East in the ancestral Cascades. This makes for a very complex tectonosedimentary environment at this time. Facies were short and steep as they are today on this active convergent
margin.
Catface Intrusions (Oligocene)
Aphanitic felsic sills, dykes and plugs outcrop on southern Vancouver Island, cutting both the Metchosin Igneous
Complex near Sooke and to the north as well as in isolated locations further west cutting the Leech River Complex
and further to the north through Wrangellia. The tectonic understanding of post convergent felsic magmas across a
former fore arc is extension and the creation of a new mantle wedge. The thickened crust acts as a heat sink driving
fractional crystallization. Here the igneous rocks are tronjheimites (plagiogranites) and resemble rhyolites and dacites
in the Metchosin and Sooke or plagiogranites in the Leech River Schist. They are extremely low in potassium so there
is no K-feldspar, and of very low colour index, so there is only albite, quartz and cathodoluminescent paragonite (Namica) in some of the plutonic sills northwest of Walker Creek and the Leech River Fault. These types of rocks typically
cut up through cold fore-arc regions and seem to be derived by the differentiation of basalt. Coeval rocks also cut a
swath across central Vancouver Island from Tofino to Mt. Washington where they host Cu-Au in skarns and
epithermal veins. Epithermal quartz, epidote and pyrite are common in veins cutting these this sills and stocks.
Metchosin Igneous Complex (Eocene)
On Southern Vancouver Island up to a about 2 kilometers of oceanic crust including pillow basalts, pillow breccias,
overlying sheet flows and underlying sheeted dykes and coeval gabbro intrusions. According to Massey, this
represents an ophiolite sequence (cross section of the oceanic crust). It is one of the fragments left of the Farallon
Plate, former eastern half of the Pacific basin. It is preserved here because it was subducted until about 45 Ma, then
uplifted and eroded on the back of the younger Cascadia subduction zone. It is also exposed to the south of the Juan
de Fuca Strait in the Olympic Mountains where it is called the Crescent formation by Tabor, in the Coast Range
Basalts of Washington and western Oregon and in SE Alaska where it forms part of the Yakutat block. Here it is
represented by transitional transitional tholeiites and metaluminous 2 pyroxene gabbros with minor hornblende
gabbros and anorthosite. Canil has studied the low grade metamorphism of the MIC and from Fe-Mg Chlorite
geothermometry shows that it was buried to about 4-5 kilometers and about 360°C. Presumably this represents the
amount of burial and exhumation with more uplift and metamorphism to the west near Loss Creek than to the East
near Metchosin and Triangle Mountain. Since the age of the volcanics is about 56 Ma as exposed here in the
subduction zone, and that subduction ceased at about 45 Ma, the subducted basalts were 11 million years old as
they were being subducted. This is not too different from the current position of the Gorda Ridge west of Southern
Oregon, except that the ridge was offshore to the SE and subduction here at the bend in the North American margin
was down to the North.
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The Leech River Complex (Jurassic & Cretaceous)
The Leech River Complex is part of the Pacific Rim Terrane and is mapped as being bounded in the north by the San
Juan - Survey Mountain fault and in the south by the Leech River fault. It consists of metamorphosed pelitic rocks,
sandstone and minor volcanics, chert and conglomerate of probably late Jurassic to Cretaceous age. Metamorphic
grades range from sub-greenschist to amphibolite facies and vary markedly between domains. Fairchild and Cowan
argue that the complex underwent two similar deformational events during which regional shortening induced
macroscopic linear structures, parasitic folds and axial plane cleavage. Regional, progressive low-pressure
greenschist to amphibolite facies metamorphism began during the first deformational event and extended into the
waning stages of the second. The P-T range is inferred as having been 1.5 - 3.5 kbar (150 - 350 MPa) and 500° to 600°
C. K-Ar age determinations from biotite and hornblende indicate metamorphism at about 41-39 Ma. Fairchild and
Cowan suggest that the Leech River rocks were emplaced against Vancouver Island by left lateral slip on the San Juan
fault after 41-39 Ma. Geophysical surveys on the extension of the San Juan Fault south of Saltspring Island contain 8
m tall drag folds and linear troughs in folded glaciomarine diamicts so the deformation may persist to modern time.
Look at the tens of km of offset across the San Juan Fault on the Vancouver Island Geological Map and draw your
own conclusions.
Yorath argues that the muds and immature lithic sands of the Leech River Complex accumulated near the toe of a
Late Jurassic through Early Cretaceous convergent continental margin, essentially the fore-arc accretionary wedge.
According to Yorath the rocks were transported northward and thrust beneath Wrangellia along the San Juan and
Survey Mountain fault systems around 55 to 45 Ma. While this fits reasonably well with the geology as interpreted on
southern Vancouver Island, Ned Brown and Jim Monger see different relations for equivalent age lithologies in the
San Juan Islands. There they see this panel of rocks as being thrust over the top of Wrangellia. There is a controversy
here to say the least! As with many convergent margin and marginal basin settings, the lithologies are all
oceanic and there is no older underlying crust. The stratigraphy here either all formed in the ocean basin, or
on the margin of the ocean basin and was subducted underneath and added to the edge of the continental
margin.
Short Descriptions of Day 3 Stops
We will go direct to Botanical Beach for the morning low tide, then make roadside and logging road stops on the
return journey to see several facies of Sooke Formation and Leech River Schist and the Metchosin Igneous Complex.
Day 3 Stop 11 Botanical Beach: Turn off West Coast Road onto Cerantes Road toward Juan de Fuca
Provincial Park and Botanical Beach. The road in part follows another overflow glacio-lacustrine outwash channel
route. Park on the far side of the parking loop near the second information kiosk. This is a Provincial park and marine
reserve so no hammers or sampling please. The trail to the beach is rough and somewhat steep for about 15 minutes.
We will climb slippery coastal beach exposures with about 5 m of relief on a wave cut terrace. Wear sturdy footwear.
Bring a drink and prepare for 1.5-2 hours away from the vans. Be aware at the head of surge channels as rogue waves
can pluck you off the rocks. There are ample reasons to call this “The Graveyard Coast”. Take care in walking not to
damage the biota among the tide pools and low intertidal zone.
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Stop 11 – Examine the angular unconformity atop the Leech River Schist at the beach. The LRS is low grade
regional greenschists and phyllites. It is steeply dipping and has many tens of metres of relief on its erosional surface
from above the parking lot to beach level. The LRS dips steeply and has complex plunging folds and faults. The grain
size in these metamorphic rocks here is pretty fine so it is a moot point whether the LRS is crystalline or just a tilted
Mesozoic pile of sediments. At this unconformity there is > somewhere between 120 and 50 Ma of time missing. The
basal member of the overlying Sooke formation is a conglomerate with predominant angular clasts of LRS. The Sooke
dips gently to the south. It makes the north limb of the Juan de Fuca synclinorium.
Just to the east of the trail and near the upper limit of the beach are a series of Catface Sills. These emplaced after
the MIC was emplaced as they are seen to cut both suites. Take the time to walk out a few metres of this outcrop and
find the basal conglomerate of the Sooke Formation perched atop the eroded sills. This means the angular
unconformity, at least in this small region is also a non-conformity.
Sooke Stratigraphy fines upsection (transgression) to sandstones and siltstones. A metre or so up section from the
basal conglometate the silts have cruziana burrows from shelf depth in-faunal feeding behavior. The best examples
are intermittently exposed in the stream bed before the cliffs and at the SW corner of the cliffs to the west across the
tidal platform. Beds of pelecypods also occur a short distance up from the base of section. Sandstones here are
markedly concretionary and variably cemented by calcite with bedded cannonball concretions and irregular vertical
chimneys marking former permeability channels and water escape structures formed during compaction and loading.
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The tide pools were formed in the intertidal zone by a combination of bio-erosion (mollusc grazing, urchin galleries),
chemical weathering and mechanical abrasion by boulders in surf conditions. Notice the raised lips surrounding many
of the tide pools. During summer, the long exposure times causes evaporation and concentration. This period hits the
Ksp for Calcite and indurates the walls of the tide pool. While the tidal platform is mechanically abraded by rocks and
logs in pounding surf, the lips of the tide pools are harder and remain raised as the regional surface erodes.
To the west of the intertidal platform is a shallow inlet floored by abundant erratic boulders, mostly from the Coast
Mountains north of Vancouver. All of the piles of erratic below ~470 metres above sea level are ice berg dropstones
from isostatic depression in excess of sea level drop in Late Wisconsinan. As Percy Bysse Shelly said, “Look on my
works ye mighty and despair!” Your are looking at the grave of an iceberg that grounded against this peninsula when
it was a ridge on the seabed ~17 Ka.
Further to the west the black rocks are Northerly dipping Bouma CDE turbidites of the Leech River. The bold resistant
beds are better cemented lenses of sandstone probably from mid-fan submarine channels in Late Mesozoic. Since
this entire melange is structurally emplaced beneath the SW side of Wrangellia it is difficult to determine what its
original sedimentary provenance was other than to note it spawned immature lithic sands and shales.
Return to the vans via the faster escape trail above the beach we just traversed. Head east not west or you will wind
up in Port Renfrew tonight and we’ll be long gone!
Stop 6: Minute Creek Leech River Schist: West Fork of Minute Creek (UTM 401970, 5374793) (no photo)
This stop examines more metamorphic rocks belonging to the Leech River Complex. As the layers in this rock vary in
composition, so do the appearance of the metamorphic index minerals. Stop opposite the smaller western tributary
to Minute Creek by the road cut. Road cuts have bands with small garnets. A short distance up the creek ~150 m is
staurolite porphyroblastic schist. Avoid the main creek it is too rugged without climbing gear.
Stop 12: Loss Creek Bridge, Hanging Wall of Leech River Fault. This is a narrow winding road with a
short shoulder and a wet ditch. Pay attention to traffic. Extremely sheared and refolded phyllite with shallow subhorizontal plunges to the SE in the plane of the fault. Here the Leech River Fault is now steeply dipping. This may be a
function of differential uplift on this former subduction zone or some Late Tertiary reactivation as a more steeply
inclined fault. Notice the rapid lateral changes in the metamorphic grade and amount of deformation in the Leech
River Schist between the last 3 stops.
Stop 13: Road Cut near Shirley. Pay attention to traffic along West Coast Road. Dark Cliff Faces on the North
side of the road contain poorly bedded, grain supported cobble conglomerate of the Sooke Formation. Walk the
length of this outcrop and notice the large vertical steps and coherent blocks of basalt. Try and figure out if these are
flows or dykes of the underlying Metchosin Igneous Complex. Also try and figure out if this a dyke intruding the
Sooke formation or vertical cliff-like relief on the underlying Metchosin. The clasts vary from angular to sub-rounded
and most are basalt. The cement and veins are mostly white calcite. There are large oyster shells embedded between
the cobbles. Why is this so different from the Sooke formation we saw at Stop 1? Discuss the depositional facies,
energy and nature of the shoreline when this part of the Sooke Formation was deposited. How has it come to be so
far above sea level now?
Viewpoint and Toilet Stop if Needed at Jordan River Delta
The Delta here is a wave dominated coastal lag deposit. Most of the boulders were deposited at deglaciation by
extreme runoff from Vancouver Island to the north. This is a favorite stop for surfers and birders. Boulders include
local facies of Vancouver Island bedrocks (gabbro, basalt: MIC, schist: WCC) as well as granodiorite from the Coast
Mountains.) The offshore shelf has a heavy mineral lag including gold and garnets derived from the Leech River
nearby as sampled and mapped by Cal Kilby for her M.Sc. thesis at U. Vic.
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Stop 14 Turn Left up Grant Road then Left on Henlyn to see Trondjheimites (no photo)
If you come to John Muir School on the left you just missed the Grant Road Turn off. About 500 m up Henlyn are
white fine grained cross cutting dykes and sills of trondjheimite (plagioclase rich dacite). Look at the contacts with the
subaerial flows of the Metchosin Basalts. Here the contact metamorphism is pretty inconspicuous and limited to a
few hydrothermal vein minerals (quartz, epidote, chlorite, pyrite). The flows in the upper levels of the Metchosin
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stratigraphy were apparently subaerial. This makes it an unsusual piece of ocean crust at least and perhaps an
accreted seamount chain as hypothesized by Duncan (1982).
Stop 15 East Sooke Park, Alyard Farm Entrance off Beecher Bay Road (See map and photo of
petroglyphs). This is intended as the lunch stop. This part of the Metchosin Igneous Complex likely represents the
lower 2/3 of the ocean crust with sheeted dykes and gabbro plutons.
15a: Sheeted Dykes: After Lunch near the vans and parking lot, head SE to the coast and turn left along the cliff path
to Crekye Point. The outcrop from the beach below the picnic area to Crekye Point is nearly continuous sheeted
dykes in sub vertical orientation. By the steep look off, to the southeast across the mouth of Becher Bay, climb down
to the beach and examine the sheeted dykes. They are mostly aphanitic and frequently have quenched selvedges at
their margins. They seem to have driven local hydrothermal systems as veining with milky quartz and pistachio green
epidote is common. Bluish black to dark brown staining is a modern surface oxidation effect where manganese
oxidizes as local groundwater seeps contact air. If you traverse the broken rugged outcrop along the beach there are
patches of cemented conglomerates of the overlying Sooke Formation preserved in hollows and between the dykes
and overlying deglacial, dropstone laden muds. There aren’t too many localites where you can see 2 unconformities
in a meter of section (nonconformity below and angular unconformity above)! The large black dyke with water on
both sides is eroded through and has a hole that one can climb through for anyone who ever wished to enter a dyke.
15b: Sooke Formation: Head back past the picnic area. If tide levels permit, take the beach route otherwise use the
path at the top to walk to the next point then meed at the foot of the short cliff in Sooke Formation Boulder
Conglomerates. If you take the beach path, you can see the Sooke Fomation sandstone behaving as an aquifer as it
does wherever it occurs here on Southern Vancouver Island. The lithic sand grains make for pretty Fe rich water and
oxidice the sand to a rusty brown. The boulder conglomerate around the point has paleomagnetic sampling core
holes. The boulders here pass the conglomerate test as all being randomly oriented with primary TRM’s (Thermal
Remnant Magnetization). The matrix all shows clockwise rotation and far sided poles as much of the Tertiary rocks in
the Corrdillera are prone to do. Look back at the map of Vancouver Island Geology and examine the left lateral sense
of throw on the San Juan Fault to see if you can reason why this should be so.
15c: Gabbros and the Trail to the Petroglyphs. (Petroglyph photo by Ocean Flynn) In the gabbros, dark plagioclase is
essential with compositions from bytownite to labradorite most common. Some facies are layered and enriched in
plagioclase to about 90% approaching anorthosites, but unlike the classical types these are small accumulations less
than a metre across, and sometimes as thin as a few centimeters suggesting crystal accumulation during flow. The
leucocratic gabbros contain accessory pink garnet indicating either a metaluminous character to these plutonic
residues or deep emplacement or both. Two pyroxenes are typically present. The black one is augite, while the
bronze weathering one with blocky outlines is hypersthene. Olivine is rare but occurs as a dominant phase in some
narrow dykelets between Aldridge Point and Pike Point in Iron Mine Bay. Segregations of hornblende also occur in
the gabbros but they are not widespread enough to be essential like the 2 pyroxenes. Magnetite is a common
accessory. Textures are highly variable from coarse to fine grained dykes, intrusions with layering, filter pressed
leucocratic differentiates, and sheared and multiply intruded agmatites. This extreme variability, especially in having
fine grained dyke rocks cutting earlier coarse grained ones attests to a long igneous history permitting heating and
cooling to have occurred more than a few times. Segregations and veins of pyrite and disseminations of chalcopyrite
occur sporadically throughout the park. During WWII, pyrite was mined at Iron Mine Bay. This is not a normal choice
for an iron ore due to the sulphur issues in processing or later as a dominant cause of acid rock drainage. Most of the
orange colours seen on roadside outcrops in the Metchosin Complex are due to weathering of pyrite. Secondary
mineralization here includes some Rhodonite along with more prevalent quartz and epidote. See if you can find this
along the trail to the petroglyphs! In the low intertidal zone below the petroglyphs is a thin olivine rich dyke from
flowage differentiation. The Petroglyphs here of a sea lion (?) and perhaps a whale Their outlines were pounded into
the cliff face of coarse grained gabbro. This is a hard rock and not an easy one to work. The T’Sooke first nation
people resided in the Becher bay area as a winter encampment and utilized coastal resources here prior to contact
with the Spanish or English. It might be possible to do cosmic ray exposure dating here, but probably the required
sampling of the petroglyph itself would be frowned upon! As the modern sea level and this coast line was established
by ~6000 years ago, they are likely of that age or younger. Stop and examine the petroglyphs then return sticking to
the coast by the high meadow trails back to the parking lot.
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Stop 3: Sheeted Dykes – Seed Tree Road (omit)
Stop 1: Tower Point Park: (See Map and Photo)
This is a portion of the submarine facies of the MIC. Pillows, pillow breccias, patches of marine sediment with
gastropods and thin cross cutting dykes are all present between the western shoreline and the southern point and
look off. Note the thinly bedded nature of the pillow and breccias units. Note pillow shape and primary oxidized flow
tops for way up. Recall that you have seen the gabbros and sheeted dykes corresponding to the core of a seamount
or lower ocean crust, these shallower marine facies which may be much shallower than a typical mid ocean ridge
setting at 2-4 km bsl and thick subaerial sheet flows by the trondjheimites. Was this normal ocean crust or a
seamount chain that hung up like asperities in the Farallon subduction zone beneath North America? Now the Juan
de Fuca and Gorda Plates are all but devoid of seamounts, while several chains are spawned off the Pacific side of
that spreading ridge. If 56-45 Ma things had a similar geometry, how could seamounts come to be subducted. There
are more puzzles here than the rocks are willing to give up!
Return to University of Victoria for ~ 5:30 PM, End of Day 3
Day 4: Sidney to Victoria: Highlights of Local Geology (Tark Hamilton)
Depart University of Victoria 8:00 AM
1) Drive to Deep Cove for ~8:45 at Warrior Point : Nanaimo Group
2)10:15 Stop at Armstrong Point: Mafic Volcanics, Saanich Granodiorite, Nanaimo Group
11:20 Bathroom stop by Tanners Bookstore at Public Washrooms in Sidney
3) Island View Beach: Cowichan Head and Quadra Sand Quaternary Sediments, Peat, Slumps
4) 1:00 Cordova Bay Beach at foot of Fenn Road: Wrangellian Volcanics & Limestones
5) 2:15 Summit of Mount Doug Park Look Off &West Coast Crystalline Complex Gneisses
6) 2:45 Cattle Point Gniesses & Glaciated Landforms
7) 3:30 Harling Point Ribbon Cherts, Siltstones and Erratics
8) 4:30 Finlayson Point: Wark Gneiss, Tyee Granite, Diamicton and Midden
5:30 Return to University of Victoria
Farewell Barbeque
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Stop 1: Warrior Point – Deep Cove
Warrior Point to Coal Point (Access via Wain Road to Madrona and park by beach access at end of Norris Road (full
access for entire shoreline exposure between Pat Bay and Deep Cove requires –0.3 m tide).
1a. Warrior Point off the Towner Bay Country Club has basal conglomeratic Comox Formation sandstones both
vertical and overturned along with a thrust slice of Saanich Granodiorite caught up in the basal thrust that deformed
the whole Nanaimo Sedimentary section until about 45 Ma when Pacific Plate motions changed. Examine the pebbles
and try and tell from the lithologies whether the source was Vancouver Island to the North and West or elsewhere?
Vancouver Island has Sicker (lithic sandstones, mafic sills and cherts), Permian Buttle Lake Limestone, Triassic
Karmutsen Greenstones, Jurassic Granodiorite, skarns, and West Coast Complex Gneisses and Schists.
1b. Cross the muddy beach to the north for the next group of outcrops. Thinly bedded alternating channelled
conglomeratic to crossbedded sandstones and siltstones and black shales are folded and overturned along most of
this beach exposure. Note dominant strike direction. What kinds of fossils are present, are they all marine or are
there any terrestrial fossils? Can you find any sedimentary structures? How does the bedding control the coastline
here? What kind of environment would deposit this kind of succession?
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Note the weathering on the massive sandstone members here. What controls the honeycomb weathering? Cement,
acid rain, what kind of weathering? Examine the alternating beds of sandstone and black siltstones. Try and figure
out the way up in this outcrop (top to North or to South?). Is this a Bouma ABC Proximal submarine fan or part of a
delta complex. How can you use the sedimentary structures to tell these alternatives apart? Exit up the large
staircase to the bus.
Stop 2: Armstrong Point – Roberts Bay
Armstrong Point (Park near Big Rock Beach sign near Iroquois Park between Roberts Bay and All Bay in the north part
of Sidney. Access is off Resthaven Dr. and Allbay road at the closest approach to between Roberts Bay. There is a
narrow staircase along the western fence line down to the beach.
2a. At foot of beach access note dark fragmental and partially porphyritic mafic volcanic rocks mapped as PermoTriassic “San Juan Volcanics”. These are most probably correlated to the Upper Triassic Karmutsen Formation. Note
the orientation and thickness of the beds. Mueller mapped the trace of the Malahat Fault passing through here. Do
you see any evidence for this in these local outcrops?
2b. Cutting the mafic lavas are some thin and nearly vertically oriented felsic dykes of Middle Jurassic (circa 168 Ma)
Saanich Granodiorite. When did the tilting and folding of the older mafic volcanics happen relative to the timing for
the emplacement of the granodiorite? Was the intrusion environment up in the brittle upper crust (epizonal) or more
plastic in the middle crust (mesozonal)? What evidence is there for this in the boundaries and inclusion relationships
of the dykes?
2c. Proceed NE along the beach to the tombolo, a spit fixed at both ends that connects the main part of the land to
the rocky outcrops that make up Armstrong Point. Examine the outcrops of conglomeratic sandstone that makes up
the Saanich Sandstone member of the Comox Formation of the Nanaimo Group. This is the lowest member of the
Nanaimo Group, an Upper Cretaceous sedimentary forearc basin. Note the bed forms, shapes and orientations of
bedding here. Look for bed forms, imbrications, cross beddings and fossils to tell way up in this package. What kind of
contact is it with the older volcanics? Is this a fault or an unconformity and which kind is it? What are the cobble
lithologies in the basal conglomerates are they local underlying bedrock types or more variable? Compare and
contrast this channelized section of Nanaimo Group sediments with Stop 1. Do they have the same sedimentary
origin or not? What is most different about the bedding here? How does the basal contact differ?
Morning Pit Stop in Public Washrooms in Sidney behind Tanner’s Books
Stop 3: Island View Beach – Unconsolidated Sediments
Island View Beach (Access off Hwy 17 – Pat Bay Hwy, East on Island View Beach Road to water. The cliffs at Island
View beach comprise the Quadra Sand (Wisconsinan Pro-glacial Outwash) atop undatably old Cowichan Head
Formation. Meet at the boat ramp to get the overview of glacial and coastal processes including slumping, erosion
and rising sea levels and their effects on local landforms. Tidal conditions permitting we will walk south to the cliffs
and see buried peat and rooted cedars beneath the modern intertidal zone. Examine the 2 main Quaternary
formations here and discuss cliff erosion and the consequences to beach nurture and real estate! Pleistocen fossils
incuding cold water clams and mammoth teeth are occasionally found here. Return to the bus before the tide comes
in.
3a. The oldest stratigraphy here exposed at the base of the cliffs south of the boat ramp is Pleistocene Cowichan
Head Formation of glaciomarine diamicton named for the stratigraphy at this type locality. This is a dark grey
dominantly fine grained compacted dense clayey sediment with dispersed bands of dropstones. It is pre Wisconsinan
and has been compacted by overlying ice of the latest glaciation. It is also called “Capilano Sediments” by correlation
to similar deposits in North Van. Sediments like this underlie much of Haro Strait, Georgia Strait, Juan de Fuca Strait,
and adjacent Fjords.
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3b. Above this forming the local cliffs is dominantly coarse silty, sandy and gravelly sediments of the Quadra Sand
Formation, named by John Clague for the prominent cliff forming relatively clean quartzose sands of Quadra Island
and most other islands along Georgia Strait, Haro Strait, Eastern Juan de Fuca Strait and Puget Sound. This unit was
deposited as a proglacial, glaciofluvial outwash deposit in advance of the advancing Wisconsinan ice sheet. The ice
proceeded to carve, sculpt and remove much of the former (circa 17 Ka) extent of its own forward deposits, only
leaving high standing and marginal remnants along islands and shorelines. The unit is diachronous with the oldest
beds in the north and the youngest at Commencement Bay in Tacoma. There, the islands all have a constant upland
elevation called the Boothian Plateau. This Quadra Sand unit contains some viable aggregate and locally has been
quarried.
3c. Drowned or subsided mid-Holocene peat deposits are intermittently exposed in the beach face north of the boat
ramp. This unit contains stumps of conifers and terrestrial organic peats dated at a few thousand years. This is a
conundrum as most of post glacial sea level rise was complete by 6 Ka. Alternate explanations are local sedimentary
subsidence due to loading or tectonic subsidence along a local fault to have lowered this former forest to sea level.
How much subsidence would it take to take the closest trees and drop them don to this intertidal zone level?
3d. Modern beach sediments are notably coarse cobbles to the south of the boat ramp with gravels and sands on the
beach and spit to the North. In the 1950’s this was all a sandy beach. In attempt to stop wave cut erosion of the cliff,
junked cars and later rip-rap blocks and most recently log cribwork has been used along the cliff base to slow erosion
and slumping. This turned off the sedimentary source for the modern beach. The longshore northerly current and
summer southeasterly storms have continued to move all the fine-grained material to the north and towards Sidney
Channel. Recent slumps in the last 2 years have just delivered a fresh load of sand to the beach south of the boat
ramp.
3e. Try and draw a cross section here that shows the correct relative superposition and contact relationships
between the aforementioned units in A through D.
3f. Examine the cliffs and compare this to the slopes being developed for housing along Island View Terrace. What
is the risk of erosion and slumping here? How might this slope be best stabilized? What use are retaining walls? What
value is there in intercepting and diverting water.
Stop 4: Wrangellian Bedrock Volcanics and Limestones by Fenn Road Cordova Bay Road
Drive to the foot of Fenn then go down to the beach. Try and go as far north as you can where there are still outcrops
of rock to examine. These are mapped by Muller (1971) as unnamed Permian or Triassic volcanics correlated to those
on San Juan Island. Most of Vancouver Island is underlain by the Triassic Karmutsen pillow basalts. Bonanza volcanic
are mostly at the far north end of the Island. A single fusilinid identification on limestone by the volcanic on San Juan
Island caused them to be interpreted as Permian. This is not seen elsewhere on Vancouver Island.
4a. Climb to the beach and examine the various lithologies and try and convince yourself these rocks belong to some
particular part of Wrangellian stratigraphy. Pay attention to textures, dykes, cross cutting relations. Flows and
pyroclastics on the high beach and note their orientation parallel to the beach and dipping out to sea. Pass further
along and note the intrusive rocks here? Were they emplaced shallow or deep? Are all of the rocks basalts?
4b. Examine the rocks in the parts of the big bedrock knob to the north. What are the cross cutting green & white
veins?
4c. Climb over the knob and pass down across some inclined amygdaloidal basalts. See if you can find the lava tube
Rocks are slippery here when wet) and evidence for original flow orientation.
4d. Across the beach is a pile of mafic pillows. Note their way up and dip direction. There are bulbous, rounded
shapes within the darker rocks. These are pillow basalts, which show that the extrusion process was submarine. The
outer rims of the pillows were formed by rapid cooling in water, producing a glassy or very fine-grained texture. The
glass has since devitrified. Amongst the pillows are breccias of angular bits of pillow which broke because of pressure
of lava or collapse downslope and fine grained hyaloclastites (subaqueous pyroclastics of altered glass and fragments
of volcanic rock). Within individual pillows are amygdules, former gas bubbles now containing the secondary
36
hydrothermal minerals: green epidote, and whitish zeolites. The outcrops are also criss-crossed by veins of calcite
and of epidote. On the north edge of the pillows is a porphyritic andesit dyke and just at the far north end of this
beach is a granodiorite stock. How are these related to the pillows?
4e. Try and go northwards a couple hundred metres and look for some lighter coloured buff to gray rocks with
different surface textures to the volcanics. Do they react to acid? If they are sedimentary, are they chemical or clastic
or both (clastic limestones = rudites). If chemical, what is the composition? If clastic, what is the texture? How do
they weather? Can you find bedding, fossils or sedimentary structures? If so, what do they indicate? Is there any
evidence as to whether this pile of limestone might be Buttle Lake (Mt. Mark Formation) or Quatsino? How do the
limestones relate to the basalts? What are the relationships among the rocks? e.g. which is the oldest, which are
younger, and how can you tell? There is a fun little rock puzzle here. If there are igneous and sedimentary rocks, were
they formed at the same time? Or were the sedimentary there first and the igneous intruded into the sediments
later or extruded on top of the sediments later? Were the sediments soft or already solidified to rocks at the time of
volcanism. Did the sedimentary accumulate on top of the older igneous materials? What does it mean if some of
each do the cutting, overlapping and including? Examine the contacts between the 2 main rock here and look for
signs of mineralization. Keep in mind when magmas hit limestones this is the recipe for skarn mineralization.
4b again. Retrace your way back to the bus, re-examine and think again about the green and white rocks by the first
knob. If metamorphism occurred, did it affect all the rocks or just some? What was more important: high pressure
strain, fluids or heat? What was the type and degree of metamorphism, if any? Note the intense hydrothermal
effects on some of the basalt dykes and breccias. Do you think this is like the roots of a submarine hotspring system,
like those that underlie black smokers today?
Look also for larger features which cut across the outcrop. These are dark basaltic dikes, up to 1m wide, which are
best observed where they intrude lighter- coloured limestone.
Look for textural variations within the dikes and interpret their origin. Make your way back to the intrusive basalts
and dacites below the Fenn access. And compare them to the basalt and limestone section then return to the vehicle.
Stop 5: Mount Doug. Park Summit Lookoff
Drive to the top of Mount Douglas and take the short path to the look off on the summit. Note the felsic gneisses
(Colquitz Gneiss of Muller, 1971) and cross cutting granitic pegmatites. Look from the summit and discuss landscape
evolution and the evidence for long term tectonic uplift and incision since Tertiary. Weather permitting we should
see Saltspring Island, the Cascades, the Island Ranges and the Olympics as well as diverse seascapes. Return to the
Bus and Drive to Uplands Park at Cattle Point.
Stop 6: Cattle Point Gneisses (WCC, Wark and Colquitz)
Examine the gneiss outcrops in the high intertidal zone between the 2 boat ramps. Note composition, structures,
orientation and metamorphic grade.
6a. There seems to be multiple phases of ductile and brittle deformation.
6b. The highest grade minerals are hornblende and garnet. Here they are well preserved, while much of the greater
Victoria area has suffered retrograde metamorphism to chlorite. This is a tectonic slice emplaced beneath Wrangellia
or perhaps the upturned roots of Wrangellia. Some of the protolith is Devonian or older. Some of the metamorphism
is Jurassic or younger.
6c. Note the differnential weathering between the high and low intertidal zones here and how mechanical gives way
to chemical weathering.
6d. Climb the bedrock boss to the south and note the drumlinization and wet based glacial flumes incised into the
gneiss.
Stop 7: Harling Point – Chinese Cemetary (Ribbon Cherts, Siltstones, Tectonics and
Glaciation)
37
Examine the ribbon cherts at the far end of the cemetery. Note the soft sediment deformation. Discuss the deep
water cold depositional facies for these rocks. Traverse to the beach and note the melange and siltstone blocks. Was
this a Jurassic accretionary wedge against Wrangellia? Note the large Ice Rafted Debris- Erratics and discuss “The Seal
King Legend” versus floating ice shelf interpretations. Traverse the edge of the cemetery to the intensely veined
siltstone. Note the proximity to the Leech River –Devils Mountain Fault System just beyond Trial Island. Note the
sulphide weathering and discuss the gold and arsenopyrite in these rocks.
Stop 8: Finlayson Point – Below Beacon Hill (Wark Gneiss, Tyee Granite, Deglacial
Diamicton, Slumps and Midden)
Park opposite Beacon Hill and traverse to the stairs down to Finlayson Point.
8a. Note the Slump into Horseshoe Bay, the tilted steps and the lag deposit of boulders and driftwood on the high
beach. Note the variety of boulder lithologies and find a few surprises including rounded concrete. There is a
longshore drift here to the East with falling grain size towards the Clover Point loop.
8b. Traverse west to the contact between the older dark Wark Gneiss and the Devonian catazonal Tyee Granite. Note
the surface with wet based fluting and glacial striations. The nonconformity here puts Late Wisconisnan (14.4 14C
against 386 Ma granite. Time permitting note the various intrusive phases in the granite across Finlayson Point.
8c. Note the slumped sod and colluvium with traces of reworked midden thought to be older than 1000 BP. Look for
Clam shells and note the location of the wool dog maxilla and the quartered antler wedge from last winters
Geoscience classes at Camosun College.
Return to U. Vic. and go to the farewell Barbeque.
References for Days 2, 3 and 4
Babcock, R.S., Burmester, R.F., Engebretson, D.C., Warnock, A., and Clark, K.P., 1992, A rifted margin origin for the Crescent basalts and related
rocks in the northern Coast Range volcanic province, Washington and British Columbia: J. Geophys. Res., v. 97, p. 6799-6821.
Brandon, M.T., 1989, Deformational styles in a sequence of olistostromal melanges, Pacific Rim Complex, western Vancouver Island, Canada:
Geol. Soc. Am. Bull., v. 101, p. 1520-1542.
Brandon, M.T., Orchard, M.J., Parrish, R.R., Sutherland Brown, A., and Yorath, C.J., 1986, Fossil ages and isotopic dates from the Paleozoic
Sicker Group and associated intrusive rocks, Vancouver island, British Columbia: Geol. Surv. Can. Current Res., v. 86-1A, p. 683-696.
Canil, D., Styan, J., Larocque, J., Bonnet, E., Kyba, J., 2010: Thickness and composition of the Bonanza arc crustal section, Vancouver Island,
Canada. Geological Society of America Bulletin, 122, 1094-1105,
Canil, D., Johnston, S.T., Larocque, J.P. Friedman, R., Heaman, L, 2013: Age, construction and exhumation of intermediate mid-crust of the
Jurassic Bonanza arc, Vancouver Island, Canada. Lithosphere, 5, 92-97
Carson, D.J.T., 1973, The plutonic rocks of Vancouver Island, British Columbia: Their petrography, chemistry, age and emplacement: Geol. Surv.
Can., v. Paper 72-44, p. 70 pp.
Coney, P.J., Jones, D.L., and Monger, J.W.H., 1980, Cordilleran suspect terranes: Nature, v. 288, p. 329-333.
DeBari, S., Anderson, R.G., and Mortensen, J.K., 1999, Correlation among lower to upper crustal components in an island arc: the Jurassic
Bonanza arc, Vancouver Island, Canada: Can. J. Earth Sci., v. 36, p. 1371-1413.
Duncan, R.A., 1982, A captured island chain in the Coast Range of Oregon and Washington: J. Geophys. Res., v. 87, p. 10827-10837.
Fairchild, L.H., and Cowan, D.S., 1982, Structure, petrology and tectonic history of the Leech River complex northwest of Victoria, Vancouver
Island: Can. J. Earth Sci., v. 19, p. 1817-1835.
Groome, W.G., Thorkelson, D.J., Friedman, R.M., Mortensen, J.K., Massey, N.W.D., Marshall, D.D., and Layer, P.W., 2003, Magmatic and
tectonic history of the Leech River Complex, Vancouver Island, British columbia: evidence for ridge-trench intersection and accretion of
the Crescent Terrane: Geol. Soc. Amer. Spec. Pap., v. 371, p. 327-353.
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