3416

1010

90

1729

2225 13

15 3240

48

24

6818

3016 8

3620

1016 16

18

18

14

817

1212

18

70

38

3020

15

2322

20

35

19

12

3248

9056

40

28

4020

9075

80

56

90

1814

18 13 4860

60

86 60

90

80

76

6038

40

24 36

32

25

26

708586

30

90

3516

87

6060

6864

82

86

8686

88

25

76

20 4234

3028

48

60

6670

4032

2856

3626

65

56

45

16

18

88

36

2835

5440

4032

3745

3826

24 35

27

12

10

23

1310

20

10

10

20

19

48

52

38

44

1540

331525

3580

40

66

32

39

58

1925

NEIL

BOOT

LAD

ROBB LAKE

3010 2030

15

35

30

30

40

15

10

3014

25

202634

1635 204318

18 10

22

10

15

1526

35

15

18

2536

30

33

37

20 22

21

40

20

2429

22

30

30

30

35

24

30

3122

4244

44

20

15

2848

35

361400

1400

1600

1600

1800

2000

2200

1600

1600

1400

1800

1600

1400

1600

A

C

B

E

F

D

G

H

I

J

A B

C D

3

Geological Survey BranchGeoscience Map 2000-9

GEOLOGY OF MOUNT MCCUSKER-ROBB LAKE AREA,

NORTHEASTERN BRITISH COLUMBIA

NTS 94G/4Wby Andrew Legun, JoAnne Nelson and Mike Cecile

SCALE 1:50 000

4 5

MIDDLE TO EARLY? SILURIAN

Sb

Sn

Osk

Ob

MIDDLE ORDOVICIAN

LATE ORDOVICIAN

EARLY SILURIAN

EARLY ORDOVICIAN

Ok

WOKKPASH MEMBERDiscontinuous. Cross-bedded dolomitic sandstone and quartzite. It is a discrete unit in the footwall of the Gautschi thrust (about 20 m. thick). Absent in ridge stratigraphy drained by Embree, Bartle and Sidenius Creeks. Towards Colledge Creek it is exposed as 50 mtres of quartzite in an anticlinal arch. Further east about 60 metres noted at Mt. Bertha by Taylor (1970).

MUNCHO-MCCONNELL FORMATIONMedium to thick bedded cream dololutites and cryptalgal laminites with scattered (aeolian?) quartz grains.

QUARTZITE MARKER UNITTwenty to fifty metres of crossbedded and horizontally laminated quartz arenites interbedded with pale dolostones and sandy dolostone. Irregular upper contact of some dolostones suggest interstratal diastems. Single beds of quartzite are up to 10 metres thick, normally 2 to 5 metres thick.

BEAVERFOOT FORMATIONIn the northeast a platformal facies of laminated to cross-bedded quartz arenite, orange arenaceous dolostone overlies reddish and brown dolomitic siltstones. Uppermost beds evidence periods of exposure and include dololutite with mudcracks, a discontinuous dolomite breccia with hematite nodules, granule quartzite. To south and west there is a sharp (shelf to basin) lithological transition to dolomitic shales, quartz turbidites, banded cherty and dolomitic siltstones, pyritic shale, black shale.

BASAL SILURIAN UNITPlaty calcareous shale, minor nodular dolomitic limestone, laminated dolomitic siltstone. Upper beds include small bioherms and bioclastic lenses interbedded with and transitional to massive shelf dolostones of overlying Nonda facies.

NONDA FORMATIONGrey to dark grey, medium bedded dolostone, cherty and silicified dolostone. Occasional biostromal and bioclastic beds with crinoids, brachiopods, stromatoporoids.

STONE FORMATIONPale unfossiliferous dolostone, alternating pale grey and white dolostone, minor granular crystalline dolostone.

SKOKI FORMATIONMedium to thick beds of dark grey to tan dolostone with oncolites, pisolites, planispiral gastropods and solitary corals (Bighornia). Beds with grazing trails and bioturbation structures are common. Upper beds are cherty in some areas (eg. north side of Sidenius Creek). Massive beds with few oncolites and fossils typify exposures on the north side of Sikanni Chief River.

KECHIKA GROUPThin bedded, putty colored, calcareous and dolomitic slate and shale. Minor interbeds of thin limestone. Uppermost beds are thicker and more dolomitic. Normally a strong cleavage obscures bedding characteristics.

BESA RIVER FORMATIONEastern facies varying from light brown to dark grey weathering shale, minor calcareous shale.

Geological boundary (defined, approximate, inferred) ...........................

Thrust fault; teeth in upper plate (defined, approximate, inferred) .........

Normal fault; downthrown side indicated (defined, approximate) ...........

Fault, uncertain or unknown type (defined, approximate) ......................

Bedding (inclined,overturned,vertical) ...................................................

Cleavage .............................................................................................

Axial trace of overturned antiform, synform (arrow indicates plunge) ....

Axial trace of upright antiform, synform (arrow indicates plunge) ...........

Fossil sample locality (macrofossil, conodant) ......................................

Minfile occurrence; developed prospect, prospect, showing....................

Cross-section line ................................................................................

Topographic contour (100 metre interval) .............................................

Geochemical analysis site ....................................................................

Area of Outcrop ....................................................................................

Robb Lake breccia, other breccias (coarser, more rounded fragments) ..

10 Kilometres2

F

A B

C

LATE SILURIAN AND EARLY DEVONIAN

Barnes, C. R. and Pyle L.J. (1999): Lower Paleozoic stratigraphy and conodont biostratigraphy, platform to basin transect, in the Trutch, Halfway River and Ware map areas (94G,B,F), northeastern British Columbia; Geological Survey of Canada, Central Forelands Natmap Project 1999, Fall workshop Program and Abstracts, edited by Larry S. Lane.

Cecile, M.P. (2000): Geology of Mt. McCusker area-east half, northeastern British Columbia; Geological Survey of Canada, publication pending.

Cecile, M.P. and Norford, B.S. (1979): Basin to platform transition, lower Paleozoic strata of Ware and Trutch areas, northeastern British Columbia; Geological Survey of Canada, Paper 79-1A, p. 219-226.

Jones, H. and Dujardin, R. (1973): Geological and geochemical report on the RB/DEV/JUNE group, Mt. Bertha; B.C. Ministry of Energy and Mines, Mineral Assessment report 4090, 8p.

Legun, A. (2000): Geology of the Mount McCusker-Robb Lake area, northeastern British Columbia; B.C. Ministry of Energy and Mines, Geological Fieldwork 1999, Paper 2000-1, pages 147-156.

MacQueen , R.W. and Thompson, R.J. (1978): Carbonate-hosted lead-zinc occurrences in northeastern British Columbia with emphasis on the Robb Lake deposit; Canadian Journal of Earth Sciences, volume 15, p. 1737-1762.

Mann, F.T. (1981): Stratigraphic aspects of the Silurian-Devonian sequence hosting zinc and lead mineralisation near Robb Lake, northeastern British Columbia; unpublished Ph.D. thesis, University of Toronto, 252p.

McHale, K.B. and Pearson, B.D. (1974): Geological and geochemical report McCusker claim groups I,II and III, Liard/Omineca Mining Division; B.C. Ministry of Energy and Mines, Mineral Assessment report 4865, 64p.

Morrow, D.W. (1978): The Dunedin Formation: a transgressive shelf carbonate sequence; Geological Survey of Canada, Paper 76-12, 35 p.

Needoba, J. (1973): Geological and geochemical report on the Inbe group; B.C. Ministry of Energy and Mines, Mineral Assessment report 44622, 10p.

Nelson, J.L., Paradis, S., Zantvoort, W. (1999): The Robb Lake carbonate-hosted lead-zinc deposit, northeastern British Columbia: A Cordilleran MVT Deposit; B.C. Ministry of Energy and Mines, Geological Fieldwork 1998, Paper 1999-1, p.89-101.

Norford, B.S. (1991): Ordovician and Silurian stratigraphy, paleogeography and depositional history in the Peace River Arch area, Alberta and British Columbia; Bulletin of Canadian Petroleum Geology, Volume 38A, p. 45-54.

Norford, B.S., Gabrielse, H. and Taylor, G.C. (1966): Stratigraphy of Silurian carbonate rocks of the Rocky Mountains, northern British Columbia; Bulletin of Canadian Petroleum Geology, Volume 14, p. 504-519.

Pearson, B. and McHale B. (1974): Geological and geochemical report J.R. claims group A and B, B.C. Ministry of Energy and Mines, Mineral Assessment report 4886, 11p.

Riddell, C.H. (1972): Surface geology, McCusker Area, northeastern British Columbia; B.C. Ministry of Energy and Mines, Petroleum Assessment report 1761, 51 p.

Salat, H. (1973): Geological and geochemical survey Tri claims; B.C. Ministry of Energy and Mines, Mineral Assessment report 4692, 15p.

Taylor, A.H. (1977): Carbonate stratigraphy and petrology: Robb Lake zinc-lead property, northeastern British Columbia; unpublished M.Sc thesis, Carleton University.

Taylor, G.C. (1979): Trutch (94G) and Ware east half (94F, E1/2) map-areas, northeastern British Columbia; Geological Survey of Canada, Open File Report 606.

Taylor, G.C. and Mackenzie, W.S. (1970): Devonian stratigraphy of northeastern British Columbia; Geological Survey of Canada, Bulletin 186, 62p.

Tebbut, G.E. (1970): Surface geology, Trimble area; B.C. Ministry of Energy and Mines, Petroleum Assessment report 1551.

Thompson, R.I. (1989): Stratigraphy, tectonic evolution and structural analysis of the Halfway River map area (94B), northern Rocky Mountains, British Columbia; Geological Survey of Canada, Memoir 425,119 p.

Williams, M.G. (1975): Geological and geochemical report, LAD, LASS and EL DORADO mineral claims, Liard/Omineca Mining Division; B.C. Ministry of Energy and Mines, Mineral Assessment report 5725, 20p.

Williams, M.G. (1974a) Diamond drilling report on the Lad and Lass claim groups, Mt. McCusker area, Mineral Assessment report 5328.

Williams, M.G. (1974b) Geological, prospecting and diamond drilling report on the Bertha claim groups, Sikanni Chief River, Robb Lake area, B.C. Ministry of Energy and Mines, Mineral Assessment report 5469, 52p.

440000E

460000E

445000E

455000E

6320000N

6345000N 6345000N

DUNEDIN FORMATIONGrey crystalline dolostone, dark grey argillaceous stromaporoid and amphiporoid-rich limestone (patch reefs?), argillaceous crinoidal limestone, minor dark calcareous shale. (Ddu): Sections at Mt. Bertha probably include younger shelf limestones.

94/BC A

N

F

O P

94/G H

4 3 12

5 6 8

12

7

1011 9

13 14 15 16

Peace Reach

Williston Lake

Finlay River

Takla Lake

97

122°124°126°

57°

56°

LOCATION MAP

MAP AREA

BRITISHCOLUMBIA

Dbr

Dw

Dd, Ddu

Ds

Dm

Sq

Dd-DBr

68

32

32

28

6066

707453

4026

30

15

5

32

22

40

5020

60 25

25 45

40

65

80

45

4

20

60

25

50

80

45

30

18

7845

12

1210

10

45 2536

40

5015

30 32

1840

25

30

3050

30

20

3320

40

30

50

5

75

75

1530

4840

20

40

60

48

49

37

13

26

18

2020

15

30

12

35

16

4225

5520

50 30 25

85

70

20

80

80

35

10

5

25

8

4649

26

30

15

10

10

30

3630

22

29

16

26

20

3529

40

10

801018

5

20

2519

26

15

25

4433

17

30

40

15

34

60

12

1035

15

6025

20

1025

34

24

68 70

STONE AND DUNEDIN FORMATIONS UNDIVIDEDDiscontinuous dark grey fossiliferous and calcareous dolostone overlying lighter grey, more massive unfossiliferous dolostone.Dsd

LATE ORDOVICIAN TO EARLY SILURIAN ROAD RIVER GROUPBrown shale, graded quartz ss., dark calcareous shale, laminated dolomitic siltstone. Equivalent to Sb + Ob (undivided).

SILURIAN BRECCIA UNITMatrix supported beds consisting of fragments of tabular dolostone, nodular chert, fossil debris. The beds are in sharp contact (above and below) with sequences of thinly interbedded cherty dolostones and brown dolomitic siltstones.

Sbx

71

q u a r t zi t e

ma

r ke

r

?

DUNEDIN AND BESA RIVER FORMATION (WESTERN FACIES)Black argillite and shale grading to and infolded with dark shaly limestone, lenses of crinoidal limestone.

094B 005 456710 6309600 ROBB LAKE, WEBB, WEST WEBB Developed Prospect ZN PB094B 012 457130 6314800 RON Showing ZN PB FE094G 004 456003 6340785 RB, DEV, JUNE, MOUNT BERTHA, MT. BERTHA Showing PB ZN BA094G 005 448999 6328063 NEIL, JR Showing ZN PB CU094G 007 447608 6345708 TRI, COLLEDGE CREEK Showing PB ZN CU BA094G 008 455705 6344191 LYNDA Showing PB BA094G 009 448900 6348225 Showing

449598 BOOT, HEEL6345312 Showing094G 014 444551

ZN PBLAD, LASS ZN PBProspect

094G 015 ZN PB6331650

RON

NORDLING CREEK CU PB ZN BA094G 013

6327718454432 TOLL, BERTHA Showing

TOLL

NORDLING CREEK

McCusker thrustGautschi thrust

McCusker thrust

24002200200018001600

I J

McCu s k e r - S i d e n i u s t h r u s t

240022002000180016001400

220020001800160014001200

24002200200018001600

2400220020001800160014001200

G H

E F

2400

1400

TRI

RB

LYNDA

MINFILE

SYMBOLS

EARLY AND MIDDLE DEVONIAN

LEGEND

REFERENCES

OSrr

Ministry of Energy and MinesMinerals DivisionGeological Survey Branch

(Abandoned)

F

CC

CC

Ok

Ok

Ok

Ok

Sn

Sn

SnSn

Sn

SnDm

Dm

DmDm

DmOb

Ob

Ob

Osk

Osk

Osk

Osk Dm

Dm Dbr

DbrDm

Sb

Sb ObDm Dbr Ds

Dm

Dd

DbrSn

Sq

Sq

Ok

Sb

Dbr

DsSq

Sq

Sb SbObOb

DbrDs

DdDs

Sn

Sb

DmDs

Sq

Ok

McCuskerthrust

Gautschithrust

Gautschithrust

Bartlethrust

Bartlethrust

ESL (metres)

OSrr

ESL

ESL

ESL

ESL

DOLOMITIC QUARTZ SANDSTONE UNITMassive beds of dolomite cemented medium and fine grained quartz sandstone. Probable stratigraphic equivalent to unit Ds.

Dqs

McCusker-Gautschithrust

Dd

Dm,Dw

Dm,Dw

Dm,Dw

Dm,Dw