LEGEND 66 67 68 69 370000E 71 72 73 74 75 76 77 78 79 380000E 81 82 83 84 85 86 Summary of Stratigraphy and Provenance Data QUATERNARY 97 97 B.C. Geological Survey Branch Hornby and Denman Islands

Q QUATERNARY DEPOSITS: Sand and gravel. 0

2 2100 N=390 GEOSCIENCE MAP 2001-3 N O TS US RE 9 sites SO S P LATE Henry MME

96 Bay SW Vertical exaggeration = 2:1 NE 96 2000 GEOLOGY OF GABRIOLA FORMATION: Thick-bedded, uKga uKga channelized, clast-supported, pebble-cobble 9 A A’ Geoffrey Fm DENMAN AND HORNBY ISLANDS, conglomerate containing predominantly mafic Q Summary of 4 stations exposed covered ASL Formation Total = 400 clasts N=44 and felsic extrusive clasts; interbedded with Gabriola 200 slump block 200 3 sites

medium-grained, poorly to moderately sorted, 95

95 7 uKga light olive grey, massive sandstone (feldspathic 0 uKg 0 1800 litharenite) with 5% detrital mica; minor mudstone Metres uKdc uKs uKcd uKn -biogenic structures NTS 92F/7E; 92F/10 20 -200 -200 SPRAY FORMATION: Massive, olive grey 10 20 N=56 uKs uKs mudstone (65%) intercalated with thin- to locally -biogenic structures

94 thick-bedded, light olive grey, massive, parallel 94 1600 3 sites By D.C. Katnick and P.S. Mustard 4 exposed covered 0

and current ripple laminated sandstone 100

Fm

(feldspathic litharenite to lithic arkose arenite, Spray 35%) containing 5-7% detrical mica. 80 Scale 1:50 000 -biogenic structures Strait 1120 3 4 60

93 GEOFFREY FORMATION: Thick-bedded, 93 uKg uKg 1400 channelized, clast-supported pebble-cobble N=335 Kilometres

2

0 conglomerate containing predominantly mafic 80 7 sites exposed covered and felsic extrusives and mafic intrusive clasts; Note: map originally produced as figure BP-1 to accompany

20 0

in a matrix of medium-grained, light olive grey 9 4 Q unpublished M.Sc. thesis of D.C. Katnick, 2001, Simon Fraser University. 20

92 sandstone. Conglomerate is interbedded with 80 92 Chickadee medium- to coarse-grained, light olive grey, 6 20 1200 Summary of 7 stations

Fm 60 o

massive, parallel and current ripple laminated, Lake Total = 700 clasts N=25 74 80 f NOTES thick-bedded sandstone (feldspathic litharenite); Geoffrey 1 site Denman minor mudstone. Point Denman and Hornby islands represent the best exposed northern occurrence of the upper two-thirds

Georgia of the Nanaimo Group, a Turonian to (~ 90 to 65 Ma) or younger sedimentary package

2

0

91

91 10

NORTHUMBERLAND FORMATION: 0 deposited within a single sedimentary basin during the Period. The succession on uKn uKn Massive, dark grey mudstone containing Collishaw 1000 -biogenic structures Point L N=21

itt these islands is both well-preserved and minimally deformed, although in general the basin was abundant calcium carbonate concretions. 60 covered le 1 site

exposed 80 81 Mudstone is locally interlaminated and 80 85 Shields buried, lithified, uplifted and deformed during the last 60 Ma. Exposures are nearly continuous along 7 F 14 6 6 Point interbedded with siltstone and fine-grained, DENMAN6 4 0 70 4 Fm the islands coasts, but inland are restricted to road cuts, cliffs and rare small outcrops. 0 11 parallel and current ripple laminated sandstone. George 9 10 Common clastic dikes and slump folded layers. 8 7 Effects of Pleistocene glaciation are most evident as scattered glacial erratics, thin till cover and 5490000N

5490000N 800

100 uKdc uKg 10 uKcd F 85 rare exposures of glacially eroded bedrock. These probably generally reflect the last (Fraser)

8 Northumberland Cr

DE COURCY FORMATION: Massive, light- eek uKn 6 40 glaciation (about 25,000 to 10,000 ybp). Thick deposits of pro-glacial sands and gravels of the Quadra uKdc uKdc Tralee

olive grey, medium- to coarse-grained, poorly 80 7 10 20 uKn Point sorted, thick-bedded sandstone (feldspathic 75 Sand covers the north-east part of Denman Island and are also exposed in several gravel pits. covered Manning 83 A’

exposed 15 Q Point 11

89

litharenite) containing 45-50% rock fragments 89 0

74 2

0 80 6 2 0 2 10 including 15% chert. Sandstone is interbedded F 11 uKga 600 N=251 8 5 Stratigraphy with thick-bedded, channelized, clast-supported 3 5 Summary of 5 stations 5 sites

Total = 500 clasts Ferry 84 0

Fm 6

0

pebble-cobble conglomerate containing a high Phipps 4 More than two kilometres of sedimentary strata are preserved, consisting of conformable and

8 10 20 0 Terminal 0 4

6

Point F 0

proportion of mafic and felsic extrusive clasts. 0 uKga

6 laterally intertonguing successions, with sandstone-conglomerate dominated units separated by

0 etres

DeCourcy 0

0

1 2 120

1 Whaling

0

m 0 10 4

8 1 Station mudstone and fine-grained sandstone assemblages. These represent the upper six formations of the 88 Lambert 88

CEDAR DISTRICT FORMATION: Massive, 66 100 76 Bay

B 0 Cape

6 uKs F 1 400 Nanaimo Group. From lowest these are: the upper Cedar District Formation, the De Courcy,

uKcd uKcd dark grey mudstone containing abundant HORNBY 10 70 Gurney

80 0 8 8

calcium carbonate concretions. Mudstone is a 6 ISLAND 90 F 1 7 Northumberland, Geoffrey and Spray formations, and the lower part of the Gabriola Formation.

exposed covered 0 200 2

locally interlaminated and interbedded with y 17 71 2 The age of the lower three formations is well constrained by common macrofossils and 71 20 siltstone and fine-grained, thin-bedded parallel- Beulah

82 70 uKg 84 40 11

Creek 7 -biogenic structures N=14 microfossils. These indicate a range spanning form about the mid to the late Campanian /

and current-ripple-laminated sandstone. n 8 0 87

87

2 6

0 6 1

6

uKn 0

6

67 0 1 site early Maastrichtian stages of the Cretaceous Period (about 80 to 70 Ma). However, no have

Common clastic dikes and slump folded layers 12 4 uKga

2 13

0 200

e 6

2 uKs Spray 100

F F 0 Point Fm been recovered from the upper three formations. These have generally been considered to also be 8 0 0 Flora uKdc 2 6 10 8 1 7 s 0 10 Islet

0 13 Late Cretaceous (thus about 70 to 65 Ma) based on the apparent conformable depositional contact

SYMBOLS 8

1 Graham 0 12 5 ISLAND8 0

2 uKs 4

7 10 Cedar District 1 Tribune 75 60 9 with the underlying unit, apparent continuity of deposition, and on rare evidence from correlative Stratigraphic contact - defined Primary fracture Lake 7 St. John

86 86 Shingle 20 1 Bay Point 68 6 Spit 9 formations of the southern . However, the only constraint on the upper age is that in other Ferry 9 Paleocurrent Rose Legend

Stratigraphic contact - approximate Secondary fracture 75 72 40 0 0 4 Terminal 1 77 60% scale places the Nanaimo Group is unconformably overlain by late Paleocene sedimentary units.

5 4 circular 50 Primary vertical fracture 80 (square root

Sound slumped 40

Stratigraphic contact - inferred 0 Whalebone 6 standard 30 60 block of equal area) Point Fo uKs 6 74 Dunlop 20

Secondary vertical fracture 10 Geoffrey Fm 7 rd 5 deviation

220 4 Point 10 Structure

0 pebble cobble

8 0

100

4

Outcrop extent 6 85

Fault, normal 45 4 boulder

covered 69 8 20 The succession exposed on Denman and Hornby islands occurs as a structural homocline with 0

69 Creek mudstone 5485000N sandstone

71 0 3 N=50

Bedding, tops known 8 Fault, unknown sense 8 uKg vector o

0 beds dipping gently to the northeast (average 8 ). There is no evidence of major structural features

83 8 9 9

200

1 mean 100

Lineation, slickenline 9 Channel 0 75 Ford 6

0 #of

1 0 0

Macrofossils (not exactly located) 0 such as significant faults and folds. This interpretation contrasts with previous maps, which show

4 Downes F 40 4 10

1 75 4 1 Clast Lithologies Cove 120 11 10% frequency interval Metcalf 7 11 Point Sedimentary measurements 9 85 Mafic Extrusive major faults with significant (100's of m) of dip-slip displacement. On Denman Island, minor faults with

General stratigraphy of the 8 Ferry Structures

84 0 10Terminal 84 Bay planar parallel

2 6 F Mafic Intrusive Rock Types

o + 9 a few metres of displacement coincide with the laterally intertonguing depositional contact of the Cedar + + 40

51 o + + 70 10 uKn

+ + + Upper Cretaceous Nanaimo Group 0 82 5 lamination + + 4 81 asymmetric 40 79 uKdc Felsic Extrusive massive v v + District and De Courcey formations, mimicking significant fault offset, but actually a depositional 125 + 8 v + + ripples v v + + top not exposed 7 uKcd 11 72 8 Felsic Intrusive synsedimentary mudstone v v + + FORMATION 76 8 + v v v v + 8 folding feature with later very minor faulting. On Hornby Island extensive sedimentary slump blocks, breccias v 9 Chert v v + + >65 Ma? 36 mudstone with v + + 20 75 67 v v v v v + + Gabriola imbricated thin sandstone and slump-folded intervals occur in several places, and appear to have been misinterpreted as post- v v + + + 80 Norman Sedimentary breccia v Point pebbles v v v v + blocks interbeds

Vancouver v v + + + 83 Metamorphic + + Spray 83 + 40 depositional fault effects by some earlier workers. However, there are minor faults and at least two well

v + o 50o v + + 50 71 20

v v v v v +

Island + Maastrichtian? 0 Vein Quartz

2 20 sandstone +++ + + 74 6 rip-up parting developed fracture sets. These minor features are generally sub-vertical and the main sets trend to the v v v v v v Geoffrey Norris

Strait + + 55 60 + + + Rocks Quartzite clasts lineation v v v v + 4 v + + + 55 clast-supported northeast and northwest. The few well-exposed minor faults are normal faults with <10m offset. v v + + Northumberland 45 Limestone v v A uKdc clastic carbonate 0 50 100 v v v + + + conglomerate v v + + Metasedimentary dikes v v v + De Courcy Repulse concretions km v v v + 16 of Georgia+ + Upper Point Eagle v Hornby - Denman Islands

v v + Depositional Environments 0 v v v 6 Rock v v + + Cedar District 82 82 Sedimentary Basins v V ~ v a + ~ 72 v v n The Nanaimo Group on these islands is interpreted as deposited in relatively deep water with c o u ++ ~ ~ ~ 12 Base Map Information Paleogene v v v v v e ~ Protection v r ~ ~ B.C 1:20 000 scale 10 Boyle v v ~ ~ ~ Chuckanut & v v v 49o ~ ~ Point Base map has been reproduced from digital TRIM I (Terrain Resource Inventory sediment gravity flows as the main transport mechanism. Multiple coalescing submarine fans are ~ Campanian v v ~ Pender TRIM map index Huntingdon Fms ~ ~ ~ v v ~ Management) 1:20 000 topographic database produced by the British Columbia v v ~ ~ v ~ ~ ~ ~ ~ Chrome considered the main depositional setting. These fans were sand-rich with elements of gravel-rich Late Cretaceous v v ~ ~ Lower Extension v v ~ ~ ~ ~ ~ ~ Island Ministry of Environment, Lands and Parks. North American Datum (NAD83). ~ ~ ~ ~ ~ ~ ~ Study v ~ ~ ~ ~ ~ ~ ~ ~ ~ Nanaimo v ~ ~ ~ ~ ~ 83 92F.066 92F.067 92F.068 systems and fed by submarine canyon point sources cross-cutting a narrow, adjacent shelf. ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 81 Universal Transverse Mercator Projection (Zone 10). ~ ~ ~ ~ ~ ~ ~ 81 ~ ~ ~ ~ ~ ~ Haslam Group Area ~ ~ ~ ~ 73 74 75 76 77 78 79 380000E 81 82 83 84 85 86 ~ ~ ~ ~ ~ ~ ~ Elevations in metres above sea level. Paleocurrents, paleoslope indicators, conglomerate clast types, and lateral facies variations all ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ Santonian U.S.A. ~ ~ ~ ~ ~ 86.6 Regional Basements ~ ~ ~ ~ Coniacian Comox

o ~ ~ ~ ~ ~ 92F.056 92F.057 92F.058 o suggest that the submarine fans came from eastern or north-eastern sources and were deposited into ~ ~ ~ ~ 88.5 Approximate mean declination in 1993 for centre of map is 22 05', + + ~ ~ ~ ~ ~ ~ Turonian Coast Belt ~ ~ ~ ~ ~ ~ 90.4 () 125 ~ ~ ~ ~ ~ ~ decreasing 9.6' annually. 48o a basin open to the west. The Coast Belt to the east and the Cascades to the southeast were probably v v Wrangellia Conglomerate Sandstone ~ 92F.04692F.047 92F.048 the predominant source areas, although some rare clast types are not common to either of these ~ Cascades Location Map Mudstone Coal proposed sources.