The Jurassic Succession at Lisadele Lake (Tulsequah Map Area, British Columbia, Canada) and Its Bearing on the Tectonic Evolution of the Stikine Terrane

Home , Arieticeras, Dorsetensia, Lissoceras, Skirroceras

Volumina Jurassica, 2011, IX: 43–60

The Jurassic succession at Lisadele Lake (Tulsequah map area, British Columbia, Canada) and its bearing on the tectonic evolution of the Stikine terrane

Farshad SHIRMOHAMMAD1, Paul L. SMITH1, Robert G. ANDERSON2, Vicki J. McNICOLL3

Key words: ammonites, chronology, Stikinia, terranes, Lower and Middle Jurassic, British Columbia.

Abstract. Jurassic rocks in the central Tulsequah map area include conglomerates and interbedded fossiliferous finer clastics of the Takwa- honi Formation (Laberge Group) which unconformably overlie Triassic rocks. Ammonite collections document the Pliensbachian, Toarcian and Bajocian stages. We refine the age and provenance of episodes of coarse clastic input and confirm the progressive change of dominant clast lithology from reworked sedimentary rocks above the Triassic-Jurassic unconformity to volcanic, plutonic and then metamorphic clasts in the Upper Toarcian. The uppermost coarse clastic unit is a Bajocian chert-pebble conglomerate which, along with the immediately underlying black mudstone, we include in the Bowser Lake Group. Together with regional correlations, this confirms that the age of the basal part of the Bowser Lake Group is diachronous, younging southwards into Stikinia. Sandstone petrofacies trends and changes in conglomerate clast composition indicate arc uplift and dissection followed by Middle Jurassic orogen recycling. The isotopic ages of detrital zircons and granite clasts compared with the biochronologically constrained ages of the enclosing strata suggests that processes of intrusion, arc uplift, unroofing, and clastic deposition during the Early Jurassic occurred over intervals of significantly less than five million years.

Introduction Souther, 1971; Tipper, Richards, 1976). In northwestern Brit- ish Columbia, the Whitehorse Trough is mainly bounded by The Stikine terrane (or Stikinia) is the largest volcanic the King Salmon and Nahlin faults, the latter juxtaposing arc terrane in the Canadian Cordillera. Basinal elements of Stikinia and Cache Creek terrane. The Nisling terrane (sensu Stikinia include the Lower to Middle Jurassic Whitehorse Wheeler, McFeely, 1991), which is made up of metamor- Trough (fore-arc basin; Wheeler, 1961; Souther, 1971, 1991; phosed sedimentary and volcanic rocks, lies on the northwest Bultman, 1979) and the successor Bowser Basin, which con- flank of Stikinia. The geometry of these terranes, their pre- tain the geological record of the interaction of Stikinia and amalgamation history and the timing of their accretion re- adjacent terranes (Fig. 1). The Whitehorse Trough located main the subject of debate (Gabrielse, Yorath, 1991; Ricketts along the northeast flank of Stikinia is separated from the et al., 1992; Currie, Parrish, 1993; Mihalynuk et al., 1994, Hazelton Trough to the south by the Triassic-Jurassic vol- 1995, 1999, 2004; English, Johnston, 2005). cano-plutonic rocks along the Stikine Arch (Wheeler, 1961;

1 Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia; e-mail: [email protected], [email protected] 2 Geological Survey of Canada, Vancouver, British Columbia; e-mail: [email protected] 3 Geological Survey of Canada, Ottawa, Ontario; e-mail: [email protected] 44 Farshad Shirmohammad et al.

U.S.A. Yukon Atlin Northwest Yellowknife 60° Territories Whitehorse Yukon

Atlin CC Tulsequah Lisadele Lake River study area Dease Lake NS (104K)

Nahlin Fault 55° B.C.

Stewart Alberta

Smithers Prince Rupert Prince George Edmonton A British Columbia Alberta King Salmon Fault 50° Pacific Ocean Calgary

NS Vancouver 0 250 500 Victoria kilometres United States of America 130° 125° 120° 115° Tulsequah area A (for location of Lisadele Lake, see inset) QN B Cry Lake area S T I K I N E A R C H Dease C Spatsizi area Lake

Terranes ST (Stikinia) QN (Quesnellia) ST CC (Cache Creek) B

NS (Nisling)

Jurassic Sedimentary Basins Bowser Basin Whitehorse Trough C (Takwahoni facies) 100 km Whitehorse Trough (Inklin facies)

Fig. 1. Map showing the location of the study area, principal regional tectonic elements, and localities mentioned in the text

The Laberge Group and overlying strata in the White- coarser-grained and more reflective of shallow water en- horse Trough are interpreted as an overlap assemblage that vironments (the Takwahoni Formation) southwest across contains a partial record of amalgamation of the Stikine and the King Salmon Fault where the outlier at Lisadele Lake in Cache Creek terranes. The Laberge Group comprises dis- northwestern British Columbia is located (Fig. 1). tal, fine-grained clastic rocks (the Inklin Formation) in the The later-stage evolution of Stikinia includes a complex, area between the Nahlin and King Salmon faults. It becomes episodic Mesozoic magmatic history which partly predates, The Jurassic succession at Lisadele Lake (Tulsequah map area, British Columbia, Canada)... 45 but is mostly synchronous with, the sequence of rocks in the Late Triassic and Early Jurassic magmatic arcs (Stuhini the study area at Lisadele Lake (e.g., Armstrong, 1988; Mon- and Hazelton groups and associated granitoid suites) to the ger et al., 1991; Woodsworth et al., 1991; Anderson, 1993; west and southwest along the Stikine Arch (Souther, 1971; Breitsprecher et al., 2007). Important magmatic episodes of Tempelman Kluit, 1979; Dickie, Hein, 1995; Hart et al., volcanism and plutonism potentially relevant to the Lisadele 1995; Johannson et al., 1997). It is believed that the White- Lake sequence occurred at about 222, 202, 195, 191, 186, horse Trough was a fore arc basin on the north-eastern flank of 182 and 175 Ma (Johannson, McNicoll, 1997; Johannson Stikinia that evolved as a result of convergence of the Stikine et al., 1997; Breitsprecher et al., 2007). Regionally overly- and Quesnel arc terranes during Early Jurassic destruction ing the Laberge Group is the Bowser Lake Group which re- of the intervening Cache Creek oceanic terrane. The White- cords an influx of clastic material derived from obduction of horse Trough was tectonically shortened during the Middle the Cache Creek oceanic terrane. Jurassic collisional event that involved the west-directed em- At Lisadele Lake, Mihalynuk et al. (2004) documented placement of the Cache Creek terrane over the Whitehorse a succession of Lower to Middle Jurassic conglomerates Trough and Stikinia (Ricketts et al., 1992). This is interpret- whose dominant clast composition changed systematically ed as marking the closure of the Cache Creek ocean and the up-section. Our study of the strata at Lisadele Lake con- accretion of Stikine terrane to the composite western edge of tributes the following: (1) it establishes more precise ages the North American plate (Monger et al., 1991; Ricketts et for the coarse clastic units within the Takwahoni Forma- al., 1992; Mihalynuk et al., 1999). Paleoflow-direction stud- tion; (2) it explores concordant changes in conglomerate ies indicate that the clastic sedimentary rocks were derived clast lithology and sandstone petrofacies that help shed light mainly from a source to the west and southwest of the basin on the tectonic evolution of the area; (3) it makes a com- during the Early Jurassic (Johannson et al., 1997; Wight et parison of the depositional age of sedimentary rocks with the al., 2004). A marked change in both paleoflow and prove- age of enclosed detrital components in order to infer the rate nance happened in Early Bajocian time when chert granules of arc unroofing; and (4) it contributes to our understand- were delivered into the basin by west-directed currents. Sed- ing of the regional transition from deposition of the Laberge imentological observations suggest a prograding fan-delta Group to deposition of the Bowser Lake Group which re- setting with distal equivalents (Bultman, 1979; Dickie, 1989; cords the linking of the Cache Creek and Stikine terranes. Dickie, Hein, 1995). The Jurassic succession exposed in the Lisadele Lake area consists of a nearly 3 km thickness of clastic sedimen- Geological Setting tary rocks that rest with angular unconformity on limestone of the Upper Triassic Sinwa Formation of the Stuhini Group The Whitehorse Trough is an elongate, arc-marginal ma- (Fig. 2). The homoclinal sequence dips approximately 55º rine sedimentary basin. It is dominated by submarine-fan southwest, and forms the northeast limb of a large syncline deposition with volcanic and plutonic detritus derived from (Shirmohammad et al., 2007). Figure 3 summarises the

Fig. 2. Panoramic view of the Lower and Middle Jurassic succession in the Lisadele Lake area For scale, the Lake is approximately 400 × 700 m). View is to the southeast. Geologic ages and the approximate positions of conglomerate units I through V are indicated 46 Farshad Shirmohammad et al.

Thickness Cgl.

Stage Zone Lithology (m) Samples beds C.U Clast lithology Unit Oblatum E10 2900 13 V Kirschneri 18

ss14 BLG

? Bajocian

2400 ss13 17 16 15 ss12

14 ss11 ss10 ?Aalenian ? E9 ss9 13 1800 ss8 S3 C4 11-12 IV Hillebrandti 1600 C3

Laberge Group-Takwahoni Formation Laberge Group-Takwahoni Toarcian 12 ss7 10 ?Crassicosta 11 C2 10 1000 C1 7-9 Planulata 9 S2 8 III 7 ss6 Kanense 6 500 6 5 ss5 Carlottense E 5-8 4 4-5 3 ss4 2.1 Kunae S1 2

Pliensbachian E 2-4 ?Freboldi E 1 ss3 2-3 II ?Sinemurian ss2 0 1 I 1 Sedimentary Norian Volcanic

Porphyry Group

Plutonic Stuhini Clast type Clast 100 m ss1

80 64 Metamorphic ?

100

200

2000 Conglomerates maximum clast size (mm)

ss 1-14 Sandstone samples for petrography Silt and sandstone Chert pebble conglomerate S 1-3 Sandstone samples for detrital zircon studies Limestone breccia C 1-4 Conglomerate clast samples Mudstone 1-18 in situ fossil localities Limestone E 1-10 ex situ fossil localities Sandstone Conglomerate

Fig. 3. Stratigraphic section measured east and north of Lisadele Lake showing the lithostratigraphy, biochronology and sample localities Breaks in the section (which were omitted for drafting purposes) represent intervals of conformable, homogenous, unfossiliferous strata. Ammonite zones and the faunas used to recognize them are documented in Figs 4 and 5. Conglomerate beds 1–14 and sandstone petrography localities ss1–14 provided the data on which Fig. 6 is based. Geochronologic data came from localities marked S and C. The pie diagrams show the proportions of conglomerate clast lithologies at the stratigraphic levels indicated. BLG – Bowser Lake Group; C.U. – Conglomerate Units; cgl. – conglomerate The Jurassic succession at Lisadele Lake (Tulsequah map area, British Columbia, Canada)... 47 stratigraphy at Lisadele Lake and indicates the fossil locali- Formation is poorly constrained. It is possible that this inter- ties and sample sites that form the basis of this study. The val could be as old as Sinemurian based on analogy with the lower part of the section is dominated by coarse-grained succession in the Atlin Lake area where echioceratids (Late clastic rocks, primarily conglomerates of the Laberge Group Sinemurian) have been collected at this stratigraphic level (Takwahoni Formation), which will be discussed in more de- (Johannson et al., 1997). tail below. The conglomerate units are commonly separated by ammonite-bearing siltstones and sandstones which provide biochronologic age constraints. The sequence becomes progressively finer grained up-section where mudstone and NORTH AMERICAN BASAL DATE STAGE AMMONITE CHRONS siltstone predominate. It is capped by a unit of chert-pebble ERROR± conglomerate correlated with the lower Bowser Lake Group. +3.8 166.0 –5.6 The 100 m thickness of strata beneath the chert-pebble con- Epizigzagiceras glomerate that we also assign to the Bowser Lake Group L differs from the underlying upper Laberge Group rocks in Rotundum that it contains finer grained, thinly bedded, dark mudstones rather than brownish siltstones and sandstones. However, the Oblatum contact with the Laberge Group is not exposed and so we do not know their exact stratigraphic relationship. We include Kirschneri

BAJOCIAN them in the Bowser Lake Group because, like the overlying E chert-pebble conglomerates, they are lithostratigraphically Crassicostatus correlative with the Ashman Formation exposed in many areas of the Bowser Basin to the south (Tipper, Richards, Widebayense +1.2 1976; Thomson et al., 1986). However, as we discuss later, 174.0 –7.9 the Ashman Formation and its equivalents exposed in the Howelli +1.4 Bowser Basin have recently been included in a suite of in- 177.6 –1.1 formal ‘Lithofacies Assemblages’ (Evenchick, Thorkelson, Scissum 2005; Evenchick et al., 2010) but we see no purpose in ex-

tending this informal terminology to this northern outlier. AALENIAN Westermanni +1.0 178.0 –1.5 Yakounensis +0.7 Biochronologic Framework L 180.1 –3.0 Hillebrandti A Jurassic biochronologic time scale based on ammonites and calibrated with a geochronologic scale based on Crassicosta +1.2 U-Pb and 40Ar-39Ar dating of rocks in western North Amer- M 181.4 –1.2 Planulata

ica (Pálfy et al., 2000a, b) is critical to this study (Fig. 4). TOARCIAN The pertinent Lower and Middle Jurassic ammonite zones and their calibrated age in millions of years are given in Fig- E Kanense +1.7 ure 4 (Hall, Westermann, 1980; Smith et al., 1988; Poulton, 183.6 –1.1 Tipper, 1991; Jakobs et al., 1994). New, in situ ammonite Carlottense L +0.5 collections from the Takwahoni Formation in the Lisadele 184.1 –0.6 Kunae Lake area were added to previous collections available in +0.5 the Geological Survey of Canada repository. Ammonoids 185.7 –0.6 Freboldi range from Early Pliensbachian to Bajocian age. The taxa +1.8 identified and their stratigraphic ranges are summarised in 186.7 –1.6 Figure 5, which serves as a basis for recognizing the zones E Whiteavesi as plotted on Figure 3. PLIENSBACHIAN Representative diagnostic taxa are illustrated in Plate 1. Imlayi Specimens of Omojuvavites (Pl. 1: 1) and Ectolcites from lo- +1.9 191.5 –4.7 cality 1 approximately 7 m below the unconformable contact between the Sinwa and the Takwahoni formations, indicate Fig. 4. North American Early and Middle Jurassic ammonite a Norian age. The age of the basal 150 m of the Takwahoni biochronological units. Modified after Pálfy et al. (2000a) 48 Farshad Shirmohammad et al.

TAXA LOCALITIES 1 E1 E2 E3 E4 2 2.1 3 4 E5 E6 E7 E8 5 6 7 8 9 10 11 12 13 E9 14 15 16 17 18 E10 Omojuvavites sp. Ectolcites .sp Metaderoceras sp . Fuciniceras sp. Arieticeras sp. Fanninoceras ( F. ) sp. Fuciniceras cf . intumescens Protogrammoceras ( Pr. ) spp. Amaltheus stokesi Amaltheus margaritatus Arieticeras cf.algovianum Leptaleoceras accuratum Fanninoceras F.( ) kunae Fanninoceras Charlotticeras( )maudense cf. Arieticeras micrasteriascf. Reynesoceras .cf italicum Fontanelliceras .sp Protogrammoceras ( Pr. ) cf. paltum Fieldingiceras fieldingii Lioceratoides (Pacificeras) angionus Lioceratoides ( Pacificeras ) sp. Tiltoniceras antiquum Lioceratoides Pacificeras( ) propinquum Fieldingiceras sp. Dactylioceras .sp Dactylioceras cf.kanense Fontanelliceras exfontanellense gr Harpoceras .spp Cleviceras .sp Taffertia cf. taffertensis Leukadiella amuratica Peronoceras sp . Hildaites murleyi? Hildaites .sp Dactylioceras cf.commune Leukadiella sp. Pseudolioceras cf.lythense Phylloceras .sp Phymatoceras hillebrandti Podagrosites sp . Podagrosites latescens Phymatoceras sp. Planammatoceras sp. Lissoceras ? sp. Sonninia .spp In place collections Sonninia cf . adicra Stephanoceras .spp Dorsetensia .spp Approximately located Stephanoceras Skirroceras( ) cf . kirschneri or excollections situ Normannites .sp Chondroceras spp.

Fig. 5. Faunal distribution chart showing ammonite taxa collected from the Lisadele Lake area The stratigraphic positions of these localities are shown in Figure 3

A single specimen of the Early Pliensbachian ammonite Specimens characteristic of the uppermost Pliensbachian Metaderoceras sp. from locality E1 is the oldest Jurassic Carlottense Zone (localities E5–8 and 2.1–4 in Figs 3, 5) ammonite collected from the Lisadele Lake area (reported include Lioceratoides (Pacificeras) propinquum (Pl. 1: 6), in Mihalynuk et al., 1999). However, the oldest relatively Protogrammoceras spp., Fontanelliceras sp., Arieticeras abundant ammonites are from the Kunae Zone of the Up- sp., Fieldingiceras sp., and Amaltheus margaritatus. per Pliensbachian (localities 2 and E2–4 in Figures 3 and The Kanense Zone at the base of the Toarcian is marked 5). The most important indicative taxa include Fanninocer at locality 5 by the appearance of Dactylioceras cf. kanense as (Fanninoceras) kunae (Pl. 1: 2), F. (Charlotticeras) cf. (Pl. 1: 8) and Taffertia cf. taffertensis (Pl. 1: 9) occurring maudense, Amaltheus stokesi (Pl. 1: 14), and A. margaritatus with holdovers from the Late Pliensbachian such as Liocera (Pl. 1: 15 (ex situ)) as well as the hildoceratids Arieticeras cf. toides (Pacificeras) propinquum and Fontanelliceras ex gr. micrasterias (Pl. 1: 4), A. cf. algovianum (Pl. 1: 3), Fucini fontanellense (Pl. 1: 7). About 15 meters above the Kanense ceras cf. intumescens (Pl. 1: 5), Leptaleoceras accuratum Zone localities, the appearance of Leukadiella amuratica and the dactylioceratid Reynesoceras italicum (Pl. 1: 10). (Pl. 1: 11) marks the base of the Middle Toarcian Planulata The Jurassic succession at Lisadele Lake (Tulsequah map area, British Columbia, Canada)... 49

Zone (localities 6–11) which also yields Dactylioceras cf. more detailed lithological information to supplement field commune as well representatives of the genera Harpocer observations. The five conglomerate units are characterized as, Peronoceras and Cleviceras. This is the most northerly in stratigraphically ascending order by a predominance of occurrence of the Tethyan genus Leukadiella which was sedimentary, volcanic, plutonic, metamorphic, and chert previously only known from Haida Gwaii (formerly the clasts as previously determined by Mihalynuk et al. (1999). Queen Charlotte Islands) of the Wrangell terrane, and from the Spatsizi and Hazelton areas of the Stikine terrane (Jakobs Conglomerate unit I makes up the lowermost five me- et al., 1994; Jakobs, 1995, 1997). Specimens characteristic tres of the Takwahoni Formation. It consists of poorly sorted, of the Upper Toarcian Hillebrandti Zone collected from lo- matrix-supported limestone-pebble to cobble breccia and calities 12 and 13 include Phymatoceras hillebrandti (Pl. conglomerate with clasts ranging in size from 5 to more than 1: 12) and Podagrosites sp. (Pl. 1: 13). 200 mm. The white to light grey, poorly sorted, sub-angu- Shell pavements of the bivalve Bositra sp. are wide- lar to angular clasts occur in a reddish-brown weathering spread south of Lisadele Lake in Middle to Upper Toarcian sandstone and siltstone matrix. The clasts are likely in situ strata. They are also present in Whitehorse Trough strata in fragments derived from erosion of the Triassic basement. Yukon and the Atlin Lake area of northern British Columbia Conglomerate I unconformably overlies the latest Norian (Aberhan, 1998; Clapham et al., 2002). Elsewhere, Bositra Sinwa Formation but, except for a possible correlation with forms shell pavements in rocks as old as Middle Toarcian the Sinemurian succession exposed in the Atlin Lake area (Damborenea, 1987). A coarse-grained fossiliferous sand- (Johannson et al., 1997), its age is poorly constrained. stone about 50 meters below locality 13 yields abundant bi- valves including Weyla sp. Conglomerate unit II conformably overlies conglomer- Unequivocal Aalenian index fossils have not been col- ate unit I and varies in thickness between 100–160 metres. lected from the study area. A single locality (E9) has yielded It consists of channel deposits of pebble- to cobble-sized two small fragments of possible Planammatoceras that may clasts (10–80 mm in diameter) that are moderately to well- be of Aalenian age as recorded by Poulton and Tipper (1991). sorted and sub-rounded to rounded. Clasts have fine-grained We also found three ex situ fragments of probable Planam igneous textures and range from leucocratic to mesocratic matoceras in the area between fossil localities 13 and 14 but (light to moderate) color index. The occasional dark grey and the specimens are not complete enough to be compared with green weathering clasts are feldspar-, hornblende- and augite known species. porphyries which resemble dominant lithologies within Up- The Lower Bajocian is marked by the occurrence of per Triassic Stuhini Group (e.g., Monger et al., 1991; An- a poorly preserved fragment at locality 14 referred to ?Lisso derson, 1993; Mihalynuk et al., 1999). These are part of the ceras sp. and the occurrence at fossil localities 15–16 of Late Triassic (Carnian–Norian) arc construction phase and specimens of Sonninia cf. adicra, and Dorsetensia spp. High were the first to be eroded following removal of thecap- in the section at locality 18, the presence of numerous stepha- ping Norian limestone. Biochronological age control has noceratids including Stephanoceras (Skirroceras) cf. kirsch been difficult to obtain but Mihalynuk et al. (1999) reported neri, indicate the Kirschneri Zone. The presence of Chon a Lower Pliensbachian Metaderoceras from immediately droceras (possibly including C. allani) in the uppermost part above the unit. of the section indicates the Oblatum Zone, the highest Zone of the Lower Bajocian. Conglomerate unit III is the thickest in the sequence (approximately 1200 m thick) and is dominated by pebble to boulder-sized plutonic clasts that are most commonly Clastic Units and Petrofacies 5–400 mm but may reach as much as 2 metres in diameter. The conglomerates are poorly sorted and the large clasts Conglomerate show high sphericity. Normal and locally reversed grading are evident. Common clast lithologies include leucogranite, The Jurassic sequence at Lisadele Lake consists of about diorite, monzonite and quartz monzonite. Intermediate to 3000 m of conglomerate, sandstone, siltstone, and mudstone felsic volcanic rocks are minor components and carbonate which includes five distinct conglomerate units (Figs 2, 3). sedimentary clasts, possibly derived from the Sinwa Forma- For each conglomerate unit, abundance of clast type and tion, are rare. Thin-bedded sandstone layers contain locally maximum clast size were determined in order to constrain abundant, fragmented plant fossils, suggesting shallow wa- provenance and energy regime. An average of 50 clasts was ter deposition and sedimentation rates that locally exceeded counted at conglomerate sample sites and their lithology and subsidence rates. size range was recorded. Thin-sections of 41 clasts provided 50 Farshad Shirmohammad et al.

The age of unit III is constrained by 12 Upper However, the plot for sedimentary clasts is bimodal with one Pliensbachian to Middle Toarcian ammonite collections dis- peak in the ?Sinemurian and the other in the Early Bajocian. tributed more or less evenly from 250 to 1350 metres above At the base of the section, just above the unconformity, lime- the base of the section (Fig. 3). The lowest locality is a few stone clasts derived from the underlying Sinwa Formation metres below the base of the unit III. The 5 localities of predominate. Volcanic and porphyritic clasts become fre- fossiliferous finer clastics interbedded with the lower part of quent in the lower part of the section but by the Toarcian, conglomerate unit III yield Upper Pliensbachian ammonites plutonic clasts dominate. There is a further provenance shift typical of the Kunae Zone. during the Toarcian reflecting a new source of clastics derived from a metamorphic source and/or unroofing the arc Conglomerate beds comprising unit IV have an ag- roots due to further arc exhumation. The uppermost con- gregate thickness of about 200 metres and contain abundant glomerate indicates a return to a sedimentary source of clasts metamorphic rock clasts. Conglomerate beds within unit IV but dominated by chert. The change in relative clast com- are less dominant than in unit III but locally reach thickness- positional proportions for 13 conglomerate beds is shown es of about 30 metres. They contain white or light to dark in an SPV (sedimentary-plutonic-volcanic) ternary diagram grey pebble- to cobble-sized (10–100 mm) clasts in a dark (Fig. 6A; sample locations indicated on Fig. 3). It indicates to locally orange or brown-orange matrix. Of secondary a change in provenance sources from flank uplift to transi- abundance are plutonic clasts. The clasts are poorly sorted tional arc by the Late Pliensbachian, to dissected arc sources but well-rounded with local current-generated imbrications by the Late Toarcian. suggesting northeast-directed paleocurrents. The upper parts of unit IV display well-sorted pebble to cobble conglomer- Sandstone Petrofacies ates (mainly 10–15 mm, maximum size up to 70 mm) interbedded with brown to light grey coarse-grained sandstone. Quartz-rich mica schist and foliated gneiss are the most Petrographic analysis of sandstones was conducted to common clast lithologies. Biotite is common in the clasts complement the data on conglomerate clasts. Samples were but attempts to provide age constraints using Ar-Ar analyses collected from all levels within the stratigraphic sequence, proved unsuccessful. Two ammonite localities bracket con- as indicated in Figure 3. The Gazzi-Dickinson method of glomerate unit IV, one approximately 200 meters below the point counting was employed and between 200–250 points base of the unit and the other from a directly overlying bed counted within each thin section in order to generate statisti- of sandstone. Both localities yield Late Toarcian species of cally acceptable modes (Van Der Plas, Tobi, 1965; Ingersoll the genera Phymatoceras and Podagrosites. et al., 1984). The sandstones are both texturally and compositionally immature. The textural immaturity is shown by Conglomerate unit V caps the upper ~1000 metres of the moderate to poor sorting, angular to sub-rounded grains, the Jurassic succession which is dominated by siltstone and and the common presence of finer matrix. The sandstones mudstone. Unit V makes up the uppermost 5–10 metres of are compositionally dominated by feldspar and quartz, with the section and consists of angular to sub-angular and well- variable amounts of lithic fragments. As shown in Figure sorted, chert granule to pebble conglomerate. Variegated 6B, the relative proportions of lithic fragments, feldspar, and clasts include black, dark green, white, red, and light to quartz in the rocks define three distinct suites when plotted medium yellow varieties of chert. Mihalynuk et al. (1999) on a ternary tectonic discrimination diagram (Dickinson et report that some clasts within this unit contain radiolarians, al., 1983), designated sandstone petrofacies A through C. ranging in age from Early Permian through Early Jurassic. Upper Triassic and Lower Jurassic (Sinemurian/ Ammonites from the extensive siltstone-mudstone interval Pliensbachian) lithic arkoses and arkoses of Petrofacies A indicate an Early Bajocian age (localities 15–18; Fig. 3). contain a low proportion of quartz grains typical of those Stephanoceratids from about 20 metres below conglomerate derived from a transitional arc. Upper Pliensbachian and unit V (locality 18) indicate a Kirschneri Zone age and Mi- Toarcian sandstones of Petrofacies B show a progressive in- halynuk et al. (1999) reported Oblatum Zone age ammonites crease in the percentage of quartz grains, a trend indicating from within the chert pebble conglomerate (locality E10; a change in provenance from a transitional arc to a dissect- Fig. 3) which together indicate an Early Bajocian age for ed arc. Upper Toarcian and Lower Bajocian sandstones of the chert pebble conglomerate unit V. Petrofacies C contain mainly feldspar and quartz fragments The pie charts in Figure 3, showing the relative abun- but relatively more abundant lithic fragments compared to dance of conglomerate clast lithologies, demonstrate that Petrofacies B; they indicate a recycled orogen source. The the abundance of each clast type is broadly unimodal and Lower Bajocian sandstone sample number 14 (Figs 3, 6B) the dominant lithology changes progressively up section. shows the highest percentage of lithic fragments. The Jurassic succession at Lisadele Lake (Tulsequah map area, British Columbia, Canada)... 51

A Conglomerates B Sandstones S Sedimentary clasts Q Quartz

13 Flank 1 Recycled Uplift Orogen

13 12 C Transitional 11 10 Arc 8 6 9 3 B 7 5 4 14

Dissected Dissected Arc Arc Transitional arc 12 2 A 6 1 Undissected 11 10 2 8 9 4 Arc 7 5 3 Basement Uplift P V F L Plutonic clasts Volcanic clasts Feldspar Lithic

Samples Age Conglomerate Sample # s Age Petrofacies units 1 Late Triassic 1 Early Jurassic (Sinemurian?) Unit I A 2 2–3 Early Jurassic (Sinem./Pliens.?) Unit II Sinemurian/Pliensbachian? 4–5 Late Pliensbachian (Carlottense Z.) 3 Early Pliensbachian 4 – 5 Late Pliensbachian 6 Early Toarcian (Kanense Z.) B 7–9 Middle Toarcian (Planulata Z.) Unit III 6 – 7 Middle Toarcian 8 Late Toarcian 10 Middle / Late Toarcian 11–12 Late Toarcian (Hillebrandti Z.) 9 - 10 Late Toarcian/Aalenian? C 13 Early Bajocian (Oblatum Z.) Unit V 11 - 14 Early Bajocian

Fig. 6. A. Ternary diagram of Takwahoni Formation conglomerates. Poles represent clast modes for plutonic (P), volcanic (V), and combined sedimentary (S) clasts. Ternary diagram after Dickie and Hein (1995). The lower panel shows age constraints and lithologic units. B. QFL ternary diagram showing plots of Takwahoni Formation sandstone petrofacies. Poles show quartz (Q), feldspar (F) and lithic fragment (L) occurrence with respect to tectonic setting. Ternary diagram after Dickinson et al. (1983). The lower panel shows age constraints and sampled petrofacies

Igsotopic A e of Detrital Components U-Pb geochronological studies of the Lower Jurassic strata were completed at the Geological Survey of Canada Isotopic age determination of the clastic components of Geochronology Laboratory in Ottawa. The data, discussed sedimentary rocks is a well-established tool for evaluating herein, include U-Pb SHRIMP (Sensitive High Resolution the relationship between tectonic activity, sediment prove- Ion Microprobe) analyses of detrital zircons in sandstone nance, and rates of sediment deposition. Age distributions of samples and U-Pb ID-TIMS (isotope dilution thermal ioni- detrital zircons can act as a fingerprint for provenance areas zation mass spectrometry) dating of two plutonic clasts and help to constrain the rate of tectonic uplift. collected from conglomerate beds (Fig. 3). U-Pb ID-TIMS 52 Farshad Shirmohammad et al. analytical methods utilized in this study are outlined in Par- concordance and equivalence = 1.7) and is interpreted to be rish et al. (1987) and treatment of analytical errors follows the crystallization age of the granitic clast. Roddick (1987). SHRIMP analyses were conducted using U-Pb SHRIMP analyses of detrital zircons from three analytical and data reduction procedures described by Stern sandstone samples were obtained. Sandstone sample S1 (1997) and Stern and Amelin (2003). was collected from within Conglomerate Unit III (Fig. 3). Clastic zircon populations with a wide age range indicate Ammonites from several meters below the sandstone sam- recycling from a clastic source or derivation from a variety ple (fossil locality 2) indicate the Kunae Zone of the Upper of unimodal sources. A narrow range of ages points to lit- Pliensbachian. The superjacent fossil localities (2.1 and 3) tle or no clastic recycling and relatively few unimodal zir- are about 100 meters above the sample and indicate the con sources. Zircons extracted from granitoid conglomerate Carlottense Zone of the Upper Pliensbachian (Fig. 3) sug- clasts should reflect the age of the source pluton. Comparison gesting a possible range of Kunae to Carlottense zone for of well-calibrated biochronologic units (giving the age of en- the S1 sample although Kunae Zone is most likely. A total closing beds) with the crystallization age of contained clastic of 31 detrital zircons was analyzed from this sample. These components constrains the timing and speed of unroofing. data are interpreted to all comprise one age population and, Small age differences imply a tectonically dynamic environ- therefore, most likely are derived from one source. The age ment and little delay between erosion and rock deposition. of this detrital population is 189.6 ±1.0 Ma (MSWD = 0.9). Two samples of granitic conglomerate clasts were dated by Sandstone sample S2 was also collected from within Con- U-Pb ID-TIMS methods. Clast sample C1 was collected from glomerate Unit III (Fig. 3). The age of the sample is con- Conglomerate Unit III (Fig. 3). Middle Toarcian (Planulata strained by Middle Toarcian (Planulata Zone) index fossils Zone) index fossils about 50 meters stratigraphically below stratigraphically below (localities 6–9) and above (localities (fossil localities 6–9) and about 30 meters above (fossil lo- 10, 11). The majority of the detrital zircons analyzed from calities 10, 11) the C1 sample provide age constraints on the this rock comprise one statistical population with an age of deposition of the conglomerate. A concordia age calculated 184.4 ±1.2 Ma (MSWD = 1.6, n = 35). There are a few older is 186.6 ± 0.5 Ma (mean square of the weighted deviations detrital grains with ages of ca. 192 Ma and ca. 197 Ma. Sand- (MSWD) of concordance and equivalence = 1.2), which stone sample S3 was collected from Conglomerate Unit IV is interpreted as the crystallization age of the granite body (Fig. 3). Upper Toarcian (Hillebrandti Zone) index fossils from which the clast was derived. Clast sample C2 was also about 400 meters stratigraphically below (at fossil locality obtained from Conglomerate Unit III but about 100 meters 12) and about 100 meters above (fossil locality 13) sample stratigraphically above sample C1and from a bed a few me- S3 provide the age constraint (Fig. 3). One detrital zircon ters above the last occurrence of Middle Toarcian ammonites yielded an age of 1420 ±36 Ma but the dominant youngest (fossil locality 11) and about 250 meters below the first oc- detrital population in the sample has an age of 184.4 ±1.0 Ma currence of Upper Toarcian ammonites (fossil locality 12). (MSWD = 1.0, n = 38). This statistical age population has the A concordia age is calculated to be 221 ±1 Ma (MSWD of same age as that obtained from sample S2, likely reflecting

Kunae Planulata Hillebrandti Jurassic time scale Samples Samples Samples Zone Zone Zone +6 +0.7 179 –6 180.1 +6 180 +1.2 –3.0 180 –6 Toarcian 181.4 –1.2 +0.5 +1.2 184.1 –0.6 181.4 –1.2 +1.7 S2: 184.4 S3: 184.4 185 183.6 –1.1 +0.5 +4 Pliensbachian 185.7 –0.6 187–4 C1: 186.6

190 S1: 189.6

Fig. 7. Geochronological and biochronological results plotted on the Jurassic time scale for sandstone zircon samples S1 to S3 and conglomerate clast sample C1 Samples S1, S2 and C1 originate from conglomerate unit III and sample S3 originates from conglomerate unit IV (Fig. 3). The Kunae Zone is Late Pliensbachian, the Planulata Zone is Middle Toarcian and the Hillebrandti Zone is Late Toarcian. Estimates and errors for the age of the upper and lower zone boundaries are indicated. Bold lines in the ‘Samples’ column show the age and error of the detrital zircon population and the dotted lines show the age and error of the youngest detrital zircons. There is little difference between clast and zircon ages and the age of the enclosing sediments, suggesting rapid unroofing. The Jurassic time scale is from Pálfy et al. (2000a) The Jurassic succession at Lisadele Lake (Tulsequah map area, British Columbia, Canada)... 53 the same source. Five other detrital zircons from sandstone well with important magmatic episodes in the Stikine terrane S3 have ages of ca. 192, 194, 205, 215 and 220 Ma. at 221 Ma and 186 Ma (e.g., Breitsprecher et al., 2007). In summary, large zircon populations from the igneous In summary, flank uplift and erosion in the volcano-plu- rocks of the conglomerate clasts and the detrital zircon pop- tonic centres predominate in the oldest part of the Jurassic ulations in the sandstone samples point to source magmas succession (?Sinemurian –Early Pliensbachian) followed by of the following approximate ages: 185, 187, 200 and 221 arc dissection for much of the Pliensbachian and Toarcian. Ma. Anomalous single crystals in the populations indicate The Late Toarcian and Middle Jurassic are dominated by sources of 192, 194, 197, 205, 215 and 220 Ma. Conglom- flank uplift, with sandstones of this interval plotting in the erate clast C2 (221 Ma) was derived from a Late Triassic recycled orogen field of the QFL ternary diagram (Fig. 6B). (Carnian) source, perhaps genetically related to the subjacent Small differences between the age of detrital components Stuhini volcanic rocks. Three detrital zircons in the Toarcian (zircons and conglomerate clast) and the age of the enclos- sandstone sample S3 also yielded an age of 220 Ma, approxi- ing strata suggest rapid Pliensbachian-Toarcian uplift of the mately the same Late Triassic age as conglomerate clast C2. source area and/or shallow emplacement of plutons. There is only a single detrital zircon in the sample S3 that Accelerated uplift producing arc dissection was possibly yielded an age of 1420 Ma, which suggests a cratonic source, achieved in part by intra-arc strike-slip faulting as suggested or perhaps recycled detritus originally from a cratonic source. by Johannson et al. (1997) for Inklin strata in the Atlin Lake The enclosing sedimentary strata for samples S1, S2 area, about 100 kilometres to the north of Lisadele Lake and S3 as well as the granitic conglomerate clast C1 are of (Fig. 1). In contrast to the Lisadele Lake area, the youngest Pliensbachian or Toarcian age. In Figure 7, the data are plot- Early Jurassic conglomerates in the Atlin Lake area are Sine- ted against the calibrated ages of the zones (chrons) from murian and although Pliensbachian rocks are common, no which the samples were collected (Kunae (Pliensbachian); Toarcian rocks are present (Johannson et al., 1997). Toarcian Planulata and Hillebrandti (Toarcian)). The age of the detrital conglomerates are present further north, however, in the Yu- zircon population from each of the sandstone samples is plot- kon and in northern BC in the Tagish-Atlin area (Hart et al., ted, as well as the age and error of the youngest single detrital 1995; Mihalynuk et al., 1999). The high abundance of meta- zircon in the sample. The age of the youngest detrital zircon morphic clasts in Toarcian conglomerates of the Takwahoni in the samples and the average age of the chron in which the Formation is unique to the Lisadele Lake area. They make up sample is contained is approximately 2 million years or less, 50% of the clasts whereas they rarely exceed 1–2% in con- although the error on each analysis is large. The average age glomerates of similar age in the Yukon (Hart et al., 1995). of the entire zircon population differs from average age of The Middle Jurassic obduction of the Cache Creek Ter- the chron by significantly less than 5 million years. rane, preceded by a narrowing and restricting of the Cache Creek ocean, caused the deposition of black muds quickly followed by the erosion and influx of chert-rich materials Discussion and conclusions into the Whitehorse Trough and across Stikinia. This important part of the sequence in the Lisadele Lake area (con- Clast and sandstone petrofacies data are in good agree- glomerate unit V and the underlying black mudstone) is here ment. Carbonate clasts in the basal Takwahoni Formation placed in the Bowser Lake Group and correlated lithostrati- were produced by the development of an erosional uncon- graphically with the Ashman Formation as recognized by formity during the Early Jurassic (?Sinemurian) which cut Tipper and Richards (1976) and Thomson et al. (1986). The into the subjacent Triassic limestones and volcanics. An un- Early Bajocian age of both conglomerate V and the under- conformity between Upper Triassic and Sinemurian arc- lying mudstone unit is demonstrated by several ammonite related strata is widespread in Stikinia (e.g., Souther, 1971; horizons (Fig. 3). Anderson, 1993). Further north, in the northern Whitehorse Trough in Yu- Arc building and erosion that occurred into the kon, Early Bajocian chert-pebble conglomerates are found in Pliensbachian provided the volcanic (e.g., Nordenskiold the Fish Lake Syncline southwest of the city of Whitehorse Dacite; Johannson, McNicoll, 1997) and porphyry clasts that (Wheeler, 1961; Tempelman Kluit, 1984; Clapham et al., predominate at this level. Some of the porphyritic rock types 2002). These Bajocian beds are equivalent to the Ashman are similar to typical volcanic rocks of the Upper Triassic Formation. They were tentatively correlated with the basal Stuhini Group in the Stikine terrane. The large volume of Tantalus Formation by Clapham et al. (2002) but it is clear granitic clasts in Toarcian strata implies extensive exposure from the work of Lowey and Hills (1988) that the Tantalus of plutons within the source area. The known or inferred Formation, where it occurs in west-central Yukon, is Early ages for clasts and probable igneous detrital zircons correlate Cretaceous. Further south in the Cry Lake map area (Figs 1 54 Farshad Shirmohammad et al.

60o

Nahlin Fault CC Teslin Fault

Lisadele Lake N TULSEQUAH Area Lower Bajocian

CRY LAKE Area ST Lower Bajocian CPC SPATSIZI Area Bathonian

Diagonal Mountain CPC Coast Plutonic Complex BB McCONNEL CREEK Area QN Early Oxfordian BB Bowser Basin

CC Cache Creek Howson Range SMITHERS Area ST Stikinia Between Middle Callovian Pinchi and earliest Oxfordian CC QN Quesnellia Fault ST 0 50 100 o kilometers 54

Fig. 8. Simplified geological map showing the Cache Creek and Quesnel terranes as well as the principal areas of Jurassic outcrop on Stikinia Black dots show location and age of the transition from Lower Jurassic volcanic and volcaniclastic rocks to the coarse clastic, chert-rich, rocks of the Bowser Lake Group (after Smith et al., 2010; Evenchick et al., 2010) and 8), the Ashman Formation is Early Bajocian, the same the Bowser Lake Group becomes more difficult to the south age as the beds in the Lisadele Lake area and the Yukon for two reasons. Firstly, volcanism there (and to the north in (Tipper, 1978; Gabrielse, 1998). It should be noted that the the Cry Lake Area) caused ash beds to be interbedded with Middle Bajocian age reported by Tipper (1978) in the Cry mudrocks, an association that is more characteristic of the Lake area is equivalent to Early Bajocian in modern termi- underlying Hazelton Group. Secondly, the chert-pebble con- nology. This is because the Aalenian stage, which was for- glomerates are less frequent. Because of these difficulties, mally recognized in 1980, is now equivalent to the former Evenchick et al. (2010) and Evenchik and Thorkelson (2005) Lower Bajocian. The Ashman Formation is of Bathonian age advocated abandonment of the name Ashman Formation and in the Spatsizi area on the south flank of the Stikine Arch the adoption of a complex suite of informal lithologic as- where the basal contact shows a slight angular discordance semblage names to describe the basal Bowser Lake Group. (Tipper, Richards, 1976; Thomson et al., 1986; Evenchick, Nonetheless they clearly confirm a regional diachronism, Thorkelsen, 2005). We recently noted the young ages of with basal Bowser Lake beds younging to the south. At Di- the basal Bowser Lake Group in these northerly localities agonal Mountain in the McConnel Creek map area, the ba- and speculated that the contact was diachronous southwards sal Bowser Lake Group is of Early Oxfordian age whereas across the Bowser Basin (Smith et al., 2010). This was con- even further south in the Howson Range of the Smithers map firmed by Evenchick et al. (2010) who published a detailed area it is of Middle Callovian to earliest Oxfordian in age study of the entire Bowser Basin south of the Stikine Arch (Evenchick et al., 2010) (Fig. 8). (located in Figs 1 and 8). Recognition of the basal beds of The Jurassic succession at Lisadele Lake (Tulsequah map area, British Columbia, Canada)... 55

In summary, the Jurassic sequence at Lisadele Lake re- and Geological Services Division, Yukon Region, Indian and cords the rapid unroofing of a volcanic arc on the flank of Northern Affairs Canada: 73–85. the Stikine terrane. Initiation of Bowser Lake Group sedi- CURRIE L.D, PARRISH R.R., 1993 — Jurassic accretion of Nisl- mentation marks the closing of the Cache Creek Ocean and ing terrane along the western margin of Stikinia, Coast Moun- initiation of a pulse of rapid subsidence in the Bowser Basin, tains, northwestern British Columbia. Geology, 21: 235–238. probably resulting from sediment loading (Gagnon et al., DAMBORENEA S.E., 1987 — Early Jurassic Bivalvia of Argen- 2009). The obducting Cache Creek terrane provided a source tina, Part 2: Superfamilies Pteriacea, Buchiacea and part of Pec- tinacea. Palaeontographica (A), 199: 113–216. of chert and other sedimentary clasts that were deposited first in the north during the Early Bajocian spreading as far south DICKIE J.R., 1989 — Sedimentary response to arc-continent trans pressive tectonics, Laberge conglomerates (Jurassic) White- as the Smithers map area some 10 million years later. horse Trough, Yukon Territory. Unpublished M.Sc. thesis, Dal- housie University, Halifax, Nova Scotia. Acknowledgments. This research was partly funded un- DICKIE J.R., HEIN F.J., 1995 — Conglomeratic fan deltas and der the Geological Survey of Canada’s Northern Resources submarine fans of the Jurassic Laberge Group, Whitehorse Program Project Y15, Cordilleran Minerals and Energy. Trough, Yukon Territory, Canada: fore-arc sedimentation and This is GSC Contribution number 20080497. Research also unroofing of a volcanic island arc complex. Sedimentary Geo supported in part by NSERC grant 8493 to Paul Smith who logy, 98: 263–292. gratefully acknowledges the advice of the late H.W. Tipper DICKINSON W.R., BEARD L.S., BRAKENRIDGE G.R., ER- during field work in the Lisadele Lake area in 1981. We thank JAVEC J.L., FERGUSON R.C., INMAN K.F., KNEPP R.A., Jozsef Pálfy, Mitch Mihalynuk and Grant Lowey for their LINDBERG F.A., RYBERG P.T., 1983 — Provenance of North helpful comments on the project. We appreciate insightful American Phanerozoic sandstones in relation to tectonic set- and thoughtful reviews of the manuscript provided by Jim ting. Geological Society of America Bulletin, 94: 222–235. Haggart and Terry Poulton. 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TEMPELMAN KLUIT D.J., 1979 — Transported cataclasite, ophi- WHEELER J.O., 1961 — Whitehorse map-area, Yukon Territory. olite and granodiorite in Yukon: evidence of arc–continent col- Geological Survey of Canada Memoir, 312. lision. Geological Survey of Canada, Paper 79-14. WHEELER J. O., McFEELY P., 1991 — Tectonic assemblage map TEMPELMAN KLUIT D.J., 1984 — Laberge and Carmacks map of the Canadian Cordillera and adjacent parts of the United areas. Geological Survey of Canada, Open File 1101, two States of America. Geological Survey of Canada map 1712A. 1:250,000 scale maps and legends. WIGHT K.L., ENGLISH J.M., JOHNSTON S.T., 2004 — Struc- THOMSON R.C., SMITH P.L., TIPPER H.W., 1986 — Lower to tural relationship between the Laberge Group and Sinwa For- Middle Jurassic (Pliensbachian to Bajocian) stratigraphy of the mation on Copper Island, southern Atlin Lake, northwest Brit- northern Spatsizi area, north-central British Columbia. Cana ish Columbia. In: Summary of Activities 2004, BC Ministry of dian Journal of Earth Sciences, 23: 1963–1973. Energy and Mines, 137–156. TIPPER H.W., RICHARDS T.A., 1976 — Jurassic stratigraphy and WOODSWORTH G.J., ANDERSON R.G., ARMSTRONG R.L., history of north central British Columbia. Geological Survey of 1991 — Plutonic Regimes. In: the Geology of North America, Canada, Bulletin, 270. Geology of Canada, no. 4 (Eds H. Gabrielse, C.J. Yorath), Geo- TIPPER H.W., 1978 — Jurassic biostratigraphy, Cry Lake map- logical Survey of Canada, (also Geological Society of Ameri- area, British Columbia. In: Current Research, Part A. Geologi ca), G-2: 491–531. cal Survey of Canada, Paper 78-1A: 25–27. VAN DER PLAS L., TOBI A.C., 1965 — A chart for judging the reliability of point counting results. American Journal of Sci ences, 263: 87–90. Plate 1

Fig. 1. Omojuvavites sp. Loc. 1 (GSC Loc. C-210277; type 42749); Sinwa Formation; Norian (Triassic) Fig. 2. Fanninoceras (Fanninoceras) kunae McLearn. Loc. 2 (GSC Loc. C-210278; type 42750); Kunae Zone (Pliensbachian) Fig. 3. Arieticeras cf. algovianum (Oppel). Loc. 2 (GSC Loc. C-210278; type 42751); Kunae Zone (Pliensbachian) Fig. 4. Arieticeras cf. micrasterias (Meneghini). Loc. 2 (GSC Loc. C-210278; type 42752); Kunae Zone (Pliensbachian) Fig. 5. Fuciniceras cf. intumescens (Fucini). Loc. 2 (GSC Loc. C-210278; type 42753); Kunae Zone (Pliensbachian) Fig. 6. Lioceratoides (Pacificeras) propinquum (Whiteaves). Loc. E6 (GSC Loc. C-210279; type 42754); Carlottense Zone (Pliensbachian) Fig. 7. Fontanelliceras ex gr. fontanellense (Gemmellaro). Loc. 6 (GSC Loc. C-210280; type 42755); Kanense Zone (Toarcian) Fig. 8. Dactylioceras cf. kanense (McLearn). Loc. 5 (GSC Loc. C-208235; type 42756); Kanense Zone (Toarcian) Fig. 9. Taffertia cf. taffertensis Guex. Loc. 5 (GSC Loc. C-208235; type 42757); Kanense Zone (Toarcian) Fig. 10. Reynesoceras italicum (Fucini). Loc. 2 (GSC Loc. C-210278; type 42758); Kunae Zone (Pliensbachian) Fig. 11. Leukadiella amuratica Renz. Loc. 6 (GSC Loc. C-210280; type 42759); Planulata Zone (Middle Toarcian) Fig. 12. Phymatoceras hillebrandti Jakobs et al. Loc. 13 (GSC Loc. C-86529; type 42760); Hillebrandti Zone (Toarcian) Fig. 13. Podagrosites sp. Loc. 12 (GSC Loc. C-86529; type 42761); Hillebrandti Zone (Toarcian) Fig. 14. Amaltheus stokesi (J. Sowerby). Loc. E4 (GSC Loc. C-86511; type 42762); Kunae Zone (Pliensbachian) Fig. 15. Amaltheus margaritatus (de Montfort). Loc. E4/E5 ex situ (GSC Loc. C-86511; type 42763); Takwahoni Formation; Kunae/Carlottense Zones (Pliensbachian) Fig. 16. Sonninia cf. adicra (Waagen). Loc. 16 (GSC Loc. C-210285; type 42764); Bajocian

Scale bar is 2 centimetres. The specimens are deposited in the type collections of the Geological Survey of Canada (GSC) Volumina Jurassica, IX PLATE 1

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Farshad SHIRMOHAMMAD et al. — The Jurassic succession at Lisadele Lake (Tulsequah map area, British Columbia, Canada)...