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Preliminary remarks on the Hettangian ammonite succession in Queen Charlotte Islands, British Columbia
PRELIMINARY REMARKS ON THE HETrANGIAN AMMONITE sUCCESSION IN QUEEN CHARLOTTE ISLANDS, BRITISH COLUMBIA HOWARD W. T I P P E R & JEAN G U E X TIPPER H.W. & GUEX J. 1994. Preliminary Remarks on the Hettangian Ammonite Succession in Queen Charlotte Islands, British Columbia. [Remarques prdliminaires sur la succession des ammonites hettangiennes dans les iles de la Reine-Charlotte, Colombie-Britannique]. GEOBIOS, M.S. 17 : 477-483. ABSTRACT An essentially continuous Hettangian sequence has been found in Queen Charlotte Islands, British Columbia. The faunas present are generally abundant, and diverse but poorly to moderately well preserved. Preliminary study of the ammonoids indicates the presence of genera beginning with a poor Psiloceras fauna at the base and an abundant Badouxia fauna on the Hettangian-Sinemurian boundary. The sequence contains most genera found in the Hettangian faunas of Nevada as well as a few not found there. This section enhances our knowledge of the ranges of Hettangian genera and species in North America. KEY WORDS : HETTANGIAN-SINEMURIANBOUNDARY,AMMONITES, BRITISHCOLUMBIA,BIOCHRONOLOGY. RI~SUME Une s6quence s6dimentaire hettangienne essentiellement continue a 6td ddcouverte rdcemment dans les ~les de la Reine-Charlotte (Colombie Britannique). Les faunes d'ammonites y sont g6ndralement abondantes et diversifides mais leur pr6servation n'est que mod6r6ment bonne. Une 6tude pr61iminaire de ces faunes a permis de reconnaitre quelques empreintes de Psiloceras ~ la base de la s6rie et une tr~s riche faune ~ Badouxia au voisinage de la limite Hettangien-Sin6murien. Cette s6quence a livr6 la plupart des genres hettangiens connus dans le Nevada ainsi que certains autres qui y sont absents. Elle complete et am61iore sustantiellement notre connaissance de la distribution biochronologique des genres et des esp~ces hettangiennes en Am6rique du Nord. MOTS-CLI~S : LIMITE HETTANGIEN-SINEMURIEN,AMMONITES,COLOMBIEBRITANNIQUE, BIOCHRONOLOGIE.
INTRODUCTION A recently discovered section of Lower Jurassic s t r a t a in the n o r t hw es t part of Queen Charlotte Islands at Kennecott Point (Fig. 1) has yielded a succession of ammonite faunas t h a t indicates all or nearly all H e t t a n g i a n time is represented. Less complete sequences also are known from Kunga Island. The ammonites are moderately to severely secondarily compressed and only in concretions and r a r e limestone bands and lenses are undeformed th r ee dimensional forms preserved. The fauna as a whole is diverse with a b u n d a n t specimens in the middle and uppe r parts of the section but extremely sparse in the lower beds. The H e t t a n g i a n beds t h a t have yielded this fauna are exposed in isolated outcrops. Upper Triassic sediments and volcanics underlie the section and
Lower Sinemurian sediments overlie it conformably. The rocks have been cut by m a n y left-lateral strike-slip faults, by numerous small normal faults and by a few low-angle reverse faults (Fig. 2). Despite this faulting a restored section (Fig. 3) can be readily established using distinctive lithological markers and distinctive faunas and preservational characters. In this paper the ranges of the i m p o r t a n t genera are illustrated in a range chart (Fig. 4) and a second range chart (Fig. 5) for the New York Canyon fauna in Nevada is included for comparative purposes. The range charts do not include the highest H e t t a n g i a n forms, the f a u n a of th e lower part of the Canadensis Zone, now considered to be part of the Hettangian. The Canadensis Zone was established by Frebold (1967) but its stratigraphic position has been controversial
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(Bloos 1983 ; Taylor 1986). It was studied recently by Jozsef Palfy (1991) and his finding will be mentioned briefly for completeness.
LITHOLOGY At Kennecott Point the Hettangian fauna is preserved within the Upper Norian to Lower Pliensbachian Sandilands Formation (Tipper et al.. 1991 ; Desrocher & Orchard 1991), a sequence of interbedded dark grey to blue-grey siltstone, coarse to fine grey sandstone, dark grey to black shale with minor greenish tuff, light grey to buff limy beds (Fig. 3). The sequence is finely bedded or laminated fine-grained beds varying to coarsely bedded (to a metre or more) coarse sandstone. The origin of the sequence is thought to be distal turbidites in whole or in part ; the coarse sands dominate in the lower part and the upper part is mainly shale and siltstone. Except for one minor unconformity n e a r the base of th~ Hettangian beds, the whole sequence at Kennecott Point is conformable and continuums across the NorianH e t t a n g i a n boundary and across the Hettangian-
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Sinemurian boundary are possible ; neither the sediments nor faunas suggest any significant interruption. The thickness of the Sandilands Formation is probably quite variable. The H e t t a n g i a n section at Kennecott Point is a minimum of 85 m thick ; the Upper Norian to Lower Sinemurian section exposed at Kennecott Point is at least 250 m thick. No complete, unfaulted section of the Sandilands Formation can be measured anywhere in Queen Charlotte Island but the whole formation is possibly several hundred metres thick.
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Figure 3 - H e t t a n g i a n stratigraphic section a t Kennecott Point s h o w i n g positions of a m m o n i t e collections (K1-K24).
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By comparison the Sunrise Formation of Nevada, which contains the best known Hettangian section in Norh America is described as "interbedded shales and limestones, with only slight variation in proportion of each throughout the section" (Muller & Ferguson 1939). The Hettangian beds specifically are described as "argillaceous and cherty limestone interbedded with shale. Limestone is dominant near the top whereas shale
forms greater proportion of the thickness near the base" (Muller & Ferguson 1939, p. 1611). The Hettangian beds in Nevada are less than 30 m thick (Guex 1980, p. 128), about one-third the thickness of the Hettangian beds at Kennecott Point. In each area the Triassic and Jurassic beds appear to be conformable and of a similar lithology
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(Muller & Ferguson 1939, p. 1610) but the environment of deposition of the Triassic-Jurassic succession in the two areas is different as volcanics seem to be closely associated with the Kennecott Point section in Queen Charlotte Islands but not in Nevada. The measured section of Guex (1980, p. 120) shows the distribution o f ammonites through the section ; most of the critical faunas are included in the range chart. Similary the section at Kennecott Point (Fig. 3) lists and labels the levels at which critical ammonites have been found and all of these are recorded in the range chart ; the intervals between the listed fauna in most instances have yielded ammonites t h a t are poorly preserved or are indeterminate. In both range charts all the important definitive forms have been included and considered ; further collecting may alter ranges slightly but not profoundly.
BIOCHRONOLOGY : COMPARISON OF FAUNAS OF KENNECOTT POINT AND NEW YORK CANYON No formal zonation of the studied stratigraphic interval will be proposed in the present paper. This will be the subject of another study in collaboration with David Taylor and Paul Smith (see Smith et al. 1988).
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Biochronologic comparison between the lower part of the sequences observed at Kennecott Point and in New york Canyon is easy but the upper parts of these sequences are more difficult to correlate. At Kennecott Point shale is the most important lithology in the upper beds and faunas are strongly compressed and identification is difficult or impossible. In the middle and lower parts of the section there are a few thin limestone beds and limy concretionary beds where preservation is good and specimens are three dimensional.
C H O R I S T O C E R A S BEDS. The last Triassic bed at Kennecott Point (bed K1) yields a very tiny Choristoceras aft. crickmayi (12 cm in diameter). The same forms were described from bed Z2 in the New York Canion (Guex 1982). Unfortunately the occurrence at Kennecott Point is in a faulted relation.
P S I L O C E R A S BEDS. The Psiloceras beds at Kennecott Point (K2-K3) are poorly fossiliferous but very richly so in Nevada (beds Z5 to Z14 : see Guex 1980). We note t h a t the rare Psiloceras collected in the Queen Charlotte Islands is related to P. primocostatum, a species occurring above the a b u n d a n t smooth Psiloceras of the P. pacificum group from New York Canyon (Tipper et al. this volume).
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E U P H Y L L I T E S BEDS. Ammonites belonging to the genus Euphyllites are restricted to the stratigraphic interval framed by the last Psiloceras below and the first Franziceras above. This group is therefore considered as a good "index" for t h a t interval and we believe t h a t it is safe to correlate the Euphyllites beds from Kennecott Point (K5 to K7) with beds Z34 to Z40 in the New York Canyon. Discamphiceras spp. and Fergusonites striatus are common in this stratigraphic interval. F R A N Z I C E R A S BEDS. The lower Franziceras beds at Kennecott Point (K8 to K l l ) yield an a b u n d a n t Saxoceras fauna. We believe t h a t these levels can be correlated with beds Z43 to Z64 in the New York Canyon. Schlotheimia spp. are abundant but poorly preserved in this interval. The upper Franziceras beds at Kennecott Point (K14 to K17), which contain the last known Pleuroacanthites, are tentatively correlated whith new York Canyon's beds Z69 to Z73. Species of Caloceras are well represented in beds K9 and K10.
PSEUDAETOMOCERAS BEDS.
DOE TZ KIR CH N E R I
The faunal sequence and ammonite assemblages observed in the upper part of the Queen Charlotte Islands section are quite different from t h a t observed in New York Canyon, Nevada. We believe that Pseudaetomoceras doetzkirchneri provides a good index to characterize the levels immediately subjacent to the Canadensis Zone. Although poorly preserved and secondarily compressed, specimens of the listed genera (Fig. 4) are generally abundant, particulary Eolytoceras, Ectocentrites and Badouxia. C A N A D E N S I S ZONE. As previously mentioned, the Canadensis Zone faunas were studied at Kennecott Point by the authors but not they have been studied by Jozsef Palfy (1991) as part of his study of the Sinemurian faunas. The Canadensis Zone is considered to straddle the Hettangian-Sinemurian boundary and in this he concurs with Riccardi et al. (1989) and Taylor (1990).Palfy (1991, p. 41) chose to place the boundary at Kennecott Point immediately below the incoming of Metophioceras aft. rotarium, Metophioceras spp., and Badouxia columbiae .
482 T h e H e t t a n g i a n l o w e r p a r t of t h e C a n a d e n s i s Zone is c h a r a c t e r i z e d by Badouxia canadensis. T h e p r e d o m i n a n c e of this t a x o n in t h e lower p a r t of t h e C a n a d e n s i s Zone w a s first n o t e d b y T i p p e r in T a s e k o L a k e s a r e a (in F r e b o l d 1967, p.7). Gen e r a in b e d s s u b j a c e n t to t h e C a n a d e n s i s Zone at K e n n e c o t t P o i n t t h a t c o n t i n u e into t h i s zone include, according to Palfy, Angulaticeras, Eolytoceras, Badouxia, possibly Ectocentrites, a n d Sunrisites b u t only t h e first t h r e e m e n t i o n e d , Angulaticeras, Eolytoceras, and Badouxia e x t e n d into t h e u p p e r C a n a d e n s i s Zone, h e n c e into t h e earliest S i n e m u r i a n . Typical C a n a d e n s i s Zone f a u n a first occurs in bed K 2 4 at K e n n e c o t t Point, b u t B. canadensis is u n k n o w n in N e w Y o r k Canyon. David T a y l o r (1990) h a s found the C a n a d e n s i s Zone t a x a in t h e S h o s h o n e M o u n t a i n s a n d in t h e G a r field a r e a ( N e v a d a ) . A t t h e m o m e n t , m o r e precise c o r r e l a t i o n is n o t possible.
TAXONOMIC NOTES Angulaticeras QUENSTEDT - Bloos (1988) p r o p o s e d t h a t all U p p e r H e t t a n g i a n - L o w e r S i n e m u r i a n S c h l o t h e i m i i d a e f o r m a l l y a s s i g n e d to t h e g e n e r a Sulciferites SPATH a n d Charmasseiceras SPATH s h o u l d be a s s i g n e d to Angulaticeras. T h a t proposal is a c c e p t e d in t h e p r e s e n t p a p e r . Franziceras BUCKMAN T h e generic n a m e Franziceras is u s e d h e r e in t h e s e n s e of G u e x (1989). Franziceras includes f o r m s p r e v i o u s l y ass i g n e d to Gonioptychoceras LANGE a n d Alsatitoides GUEX. Franziceras sp. 1 collected f r o m b e d s K9 a n d K17 at K e n n e c o t t a r e v e r y t h i c k a n d r o b u s t f o r m s w i t h a strong, a l m o s t c r e n u l a t e d keel. Franziceras sp. 2 occurring in bed K10 a t K e n n e cott is h i g h l y c o m p r e s s e d , w i t h a n a l m o s t acute w h o r l section. Franziceras spp. f r o m N e v a d a are described in G u e x (1989). Caloceras HYATT. T w o species of h i g h l y s e r p e n t i cone Caloceras w e r e collected f r o m beds K9 a n d K 1 0 - K l l a t K e n n e c o t t Point. Caloceras sp. 1 h a s a v o l u t i o n w h i c h is identical to C. aft. multicostaturn b u t its r i b b i n g is less dense.
SUMMARY
A l t h o u g h s o m e g e n e r a are not p r e s e n t at b o t h N e w York C a n y o n , N e v a d a a n d K e n n e c o t t Point, B. C., t h e r e is sufficient i n f o r m a t i o n to m a k e r e a sonable correlations b e t w e e n t h e t w o s e q u e n c e s , T h e s e two s e q u e n c e s s u p p l e m e n t e d b y o t h e r m u c h less c o m p l e t e s e q u e n c e s will f o r m t h e b a s i s for a N o r t h A m e r i c a n a m m o n i t e z o n a t i o n for the H e t t a n g i a n stage. A c k n o w l e d g m e n t s - The authors wish to thank David Taylor for his valuable comments on the Upper Hettangian ammonites from Kennecott Point.
REFERENCES BLOOS G. 1983 - The Zone of Schlotheimia marmorea (Lower Lias) - Hettangian or Sinemurian?. Newsletter on Stratigraphy, 12 : 123-131. BLOOS G. 1988 - Ammonites marmoreus OPPEL (Schlotheimiidae) im unteren Lias (Angulata-Zone) von Wtirttemberg (Stidwestdeutschland). Sttuttg. Beitr. Naturk., B-141 : 1-47. DESROCHER A. • ORCHARD M.J. 1991 - Stratigraphic revisions and carbonate sedimentology of the Kunga Group (Upper Triassic-Lower Jurassic), Queen Charlotte Islands, British Columbia. In WOODSWORTH G.J. (ed) : Evolution and hydrocarbon potential of the Queen Charlotte Basin, British Columbia. Geol. Surv. Canada, P a p . 90-10 : 164-172. FREBOLD H. 1967 - Hettangian ammonite faunas of the Taseko Lakes area, British Columbia. Geol. Surv. Canada, 158. GUEX J. 1980 - Remarques pr61iminaires sur la distribution stra'tigraphique des ammonites hettangiennes du New York Canyon (Gabbs Valley Range, Nevada). Bull. Ggol. Univ. Lausanne, 250 : 127-140; GUEX J. 1982 - Relations entre le genre Psiloceras et les Phylloceratida au voisinage de la limite TriasJurassique. Bull. Gdol. Univ. Lausanne, 260 : 47-51. GUEX J. 1989 - Note sur le genre Franziceras Buckman (Ammonoidea, Cephalopoda). Bull. Gdol. Univ. Lausanne, 305 : 347-354. MULLER S.W. & FERGUSON H.G. 1939 - Mesozoic stratigraphy of the Hawthorne and Tonapah quadrangles, Nevada. Bull. Geol. Soc. Am., v. 50. PALFY J. 1991 ~ Uppermost Hettangian to Lowermost Pliensbachian (Lower Jurassic) biostratigraphy :and ammonoid fauna of the Queen Charlotte Islands, British Columbia. University of British Columbia M.Sc. thesis. RICCARDI A.C., DAMBORENEA S.E., MANCENIDO M.O. & BALLENT S.C. 1989 - Hettangiano y Sinemuriano marinos en Argentina. In V. Congresso Geologico Chileno. Departamento Geologico y Geofisico, Universidad Chile, 2 : C359-C373. SMITH P.L., TIPPER H.W., TAYLOR D.R. & GUEX J. 1988 An ammonite zonation for the Lower Jurassic of Canada and the United States : the Pliensbachian. Calz. J. Earth Sc., 25 : 1503-1523. -
T h e H e t t a n g i a n f a u n a s at K e n n e c o t t P o i n t r e p r e s e n t a l m o s t a c o m p l e t e succession.
483 TAYLOR D. 1986 - The H e t t a n g i a n - S i n e m u r i a n boundary ( E a r l y J u r a s s i c ) : Reply to Bloos 1983. Newsletter on Stratigraphy, 16 : 57-67. TAYLOR D.G. 1990 - Two species of Paraloceras from the C a n a d e n s e Zone ( H e t t a n g i a n - S i n e m u r i a n stages) in N e v a d a (USA). Bull. Gdol. Univ., Lausanne, 309 : 211-219. TIPPER H.W., SMITH P.L., CAMERON B.E.B., CARTER E.S., JAKOBS G.K. & JOHNS M.J. 1991 - Biostratig r a p h y of the Lower J u r a s s i c formations of t h e Queen C h a r l o t t e Islands, B r i t i s h Columbia. In WOODSWORTH G.J. (ed) : Evolution and hydrocarbon
potential of the Queen C h a r l o t t e Basin, British Co. lumbia. Geol. Surv. Canada, P a p . 90-10 : 203-205. H.W. T I P P E R Cordilleran Division Geological Survey of Canada 100 West Pender Street Vancouver , B.C. V6B 1R8, Canada
J. GUEX Institut de G~ologie Geological Survey of Canada Contribution n ° 26691 BFSH-2 CH-1015, Lausanne
INTRODUCTION A recently discovered section of Lower Jurassic s t r a t a in the n o r t hw es t part of Queen Charlotte Islands at Kennecott Point (Fig. 1) has yielded a succession of ammonite faunas t h a t indicates all or nearly all H e t t a n g i a n time is represented. Less complete sequences also are known from Kunga Island. The ammonites are moderately to severely secondarily compressed and only in concretions and r a r e limestone bands and lenses are undeformed th r ee dimensional forms preserved. The fauna as a whole is diverse with a b u n d a n t specimens in the middle and uppe r parts of the section but extremely sparse in the lower beds. The H e t t a n g i a n beds t h a t have yielded this fauna are exposed in isolated outcrops. Upper Triassic sediments and volcanics underlie the section and
Lower Sinemurian sediments overlie it conformably. The rocks have been cut by m a n y left-lateral strike-slip faults, by numerous small normal faults and by a few low-angle reverse faults (Fig. 2). Despite this faulting a restored section (Fig. 3) can be readily established using distinctive lithological markers and distinctive faunas and preservational characters. In this paper the ranges of the i m p o r t a n t genera are illustrated in a range chart (Fig. 4) and a second range chart (Fig. 5) for the New York Canyon fauna in Nevada is included for comparative purposes. The range charts do not include the highest H e t t a n g i a n forms, the f a u n a of th e lower part of the Canadensis Zone, now considered to be part of the Hettangian. The Canadensis Zone was established by Frebold (1967) but its stratigraphic position has been controversial
478
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(Bloos 1983 ; Taylor 1986). It was studied recently by Jozsef Palfy (1991) and his finding will be mentioned briefly for completeness.
LITHOLOGY At Kennecott Point the Hettangian fauna is preserved within the Upper Norian to Lower Pliensbachian Sandilands Formation (Tipper et al.. 1991 ; Desrocher & Orchard 1991), a sequence of interbedded dark grey to blue-grey siltstone, coarse to fine grey sandstone, dark grey to black shale with minor greenish tuff, light grey to buff limy beds (Fig. 3). The sequence is finely bedded or laminated fine-grained beds varying to coarsely bedded (to a metre or more) coarse sandstone. The origin of the sequence is thought to be distal turbidites in whole or in part ; the coarse sands dominate in the lower part and the upper part is mainly shale and siltstone. Except for one minor unconformity n e a r the base of th~ Hettangian beds, the whole sequence at Kennecott Point is conformable and continuums across the NorianH e t t a n g i a n boundary and across the Hettangian-
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Sinemurian boundary are possible ; neither the sediments nor faunas suggest any significant interruption. The thickness of the Sandilands Formation is probably quite variable. The H e t t a n g i a n section at Kennecott Point is a minimum of 85 m thick ; the Upper Norian to Lower Sinemurian section exposed at Kennecott Point is at least 250 m thick. No complete, unfaulted section of the Sandilands Formation can be measured anywhere in Queen Charlotte Island but the whole formation is possibly several hundred metres thick.
479 Metres
Figure 3 - H e t t a n g i a n stratigraphic section a t Kennecott Point s h o w i n g positions of a m m o n i t e collections (K1-K24).
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forms greater proportion of the thickness near the base" (Muller & Ferguson 1939, p. 1611). The Hettangian beds in Nevada are less than 30 m thick (Guex 1980, p. 128), about one-third the thickness of the Hettangian beds at Kennecott Point. In each area the Triassic and Jurassic beds appear to be conformable and of a similar lithology
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(Muller & Ferguson 1939, p. 1610) but the environment of deposition of the Triassic-Jurassic succession in the two areas is different as volcanics seem to be closely associated with the Kennecott Point section in Queen Charlotte Islands but not in Nevada. The measured section of Guex (1980, p. 120) shows the distribution o f ammonites through the section ; most of the critical faunas are included in the range chart. Similary the section at Kennecott Point (Fig. 3) lists and labels the levels at which critical ammonites have been found and all of these are recorded in the range chart ; the intervals between the listed fauna in most instances have yielded ammonites t h a t are poorly preserved or are indeterminate. In both range charts all the important definitive forms have been included and considered ; further collecting may alter ranges slightly but not profoundly.
BIOCHRONOLOGY : COMPARISON OF FAUNAS OF KENNECOTT POINT AND NEW YORK CANYON No formal zonation of the studied stratigraphic interval will be proposed in the present paper. This will be the subject of another study in collaboration with David Taylor and Paul Smith (see Smith et al. 1988).
doetzktrchnerl
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Biochronologic comparison between the lower part of the sequences observed at Kennecott Point and in New york Canyon is easy but the upper parts of these sequences are more difficult to correlate. At Kennecott Point shale is the most important lithology in the upper beds and faunas are strongly compressed and identification is difficult or impossible. In the middle and lower parts of the section there are a few thin limestone beds and limy concretionary beds where preservation is good and specimens are three dimensional.
C H O R I S T O C E R A S BEDS. The last Triassic bed at Kennecott Point (bed K1) yields a very tiny Choristoceras aft. crickmayi (12 cm in diameter). The same forms were described from bed Z2 in the New York Canion (Guex 1982). Unfortunately the occurrence at Kennecott Point is in a faulted relation.
P S I L O C E R A S BEDS. The Psiloceras beds at Kennecott Point (K2-K3) are poorly fossiliferous but very richly so in Nevada (beds Z5 to Z14 : see Guex 1980). We note t h a t the rare Psiloceras collected in the Queen Charlotte Islands is related to P. primocostatum, a species occurring above the a b u n d a n t smooth Psiloceras of the P. pacificum group from New York Canyon (Tipper et al. this volume).
481 Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z 2 5 13 14 15 17 24 34 35 40 43 47 64 69 73 90 98 100110111 112 l
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E U P H Y L L I T E S BEDS. Ammonites belonging to the genus Euphyllites are restricted to the stratigraphic interval framed by the last Psiloceras below and the first Franziceras above. This group is therefore considered as a good "index" for t h a t interval and we believe t h a t it is safe to correlate the Euphyllites beds from Kennecott Point (K5 to K7) with beds Z34 to Z40 in the New York Canyon. Discamphiceras spp. and Fergusonites striatus are common in this stratigraphic interval. F R A N Z I C E R A S BEDS. The lower Franziceras beds at Kennecott Point (K8 to K l l ) yield an a b u n d a n t Saxoceras fauna. We believe t h a t these levels can be correlated with beds Z43 to Z64 in the New York Canyon. Schlotheimia spp. are abundant but poorly preserved in this interval. The upper Franziceras beds at Kennecott Point (K14 to K17), which contain the last known Pleuroacanthites, are tentatively correlated whith new York Canyon's beds Z69 to Z73. Species of Caloceras are well represented in beds K9 and K10.
PSEUDAETOMOCERAS BEDS.
DOE TZ KIR CH N E R I
The faunal sequence and ammonite assemblages observed in the upper part of the Queen Charlotte Islands section are quite different from t h a t observed in New York Canyon, Nevada. We believe that Pseudaetomoceras doetzkirchneri provides a good index to characterize the levels immediately subjacent to the Canadensis Zone. Although poorly preserved and secondarily compressed, specimens of the listed genera (Fig. 4) are generally abundant, particulary Eolytoceras, Ectocentrites and Badouxia. C A N A D E N S I S ZONE. As previously mentioned, the Canadensis Zone faunas were studied at Kennecott Point by the authors but not they have been studied by Jozsef Palfy (1991) as part of his study of the Sinemurian faunas. The Canadensis Zone is considered to straddle the Hettangian-Sinemurian boundary and in this he concurs with Riccardi et al. (1989) and Taylor (1990).Palfy (1991, p. 41) chose to place the boundary at Kennecott Point immediately below the incoming of Metophioceras aft. rotarium, Metophioceras spp., and Badouxia columbiae .
482 T h e H e t t a n g i a n l o w e r p a r t of t h e C a n a d e n s i s Zone is c h a r a c t e r i z e d by Badouxia canadensis. T h e p r e d o m i n a n c e of this t a x o n in t h e lower p a r t of t h e C a n a d e n s i s Zone w a s first n o t e d b y T i p p e r in T a s e k o L a k e s a r e a (in F r e b o l d 1967, p.7). Gen e r a in b e d s s u b j a c e n t to t h e C a n a d e n s i s Zone at K e n n e c o t t P o i n t t h a t c o n t i n u e into t h i s zone include, according to Palfy, Angulaticeras, Eolytoceras, Badouxia, possibly Ectocentrites, a n d Sunrisites b u t only t h e first t h r e e m e n t i o n e d , Angulaticeras, Eolytoceras, and Badouxia e x t e n d into t h e u p p e r C a n a d e n s i s Zone, h e n c e into t h e earliest S i n e m u r i a n . Typical C a n a d e n s i s Zone f a u n a first occurs in bed K 2 4 at K e n n e c o t t Point, b u t B. canadensis is u n k n o w n in N e w Y o r k Canyon. David T a y l o r (1990) h a s found the C a n a d e n s i s Zone t a x a in t h e S h o s h o n e M o u n t a i n s a n d in t h e G a r field a r e a ( N e v a d a ) . A t t h e m o m e n t , m o r e precise c o r r e l a t i o n is n o t possible.
TAXONOMIC NOTES Angulaticeras QUENSTEDT - Bloos (1988) p r o p o s e d t h a t all U p p e r H e t t a n g i a n - L o w e r S i n e m u r i a n S c h l o t h e i m i i d a e f o r m a l l y a s s i g n e d to t h e g e n e r a Sulciferites SPATH a n d Charmasseiceras SPATH s h o u l d be a s s i g n e d to Angulaticeras. T h a t proposal is a c c e p t e d in t h e p r e s e n t p a p e r . Franziceras BUCKMAN T h e generic n a m e Franziceras is u s e d h e r e in t h e s e n s e of G u e x (1989). Franziceras includes f o r m s p r e v i o u s l y ass i g n e d to Gonioptychoceras LANGE a n d Alsatitoides GUEX. Franziceras sp. 1 collected f r o m b e d s K9 a n d K17 at K e n n e c o t t a r e v e r y t h i c k a n d r o b u s t f o r m s w i t h a strong, a l m o s t c r e n u l a t e d keel. Franziceras sp. 2 occurring in bed K10 a t K e n n e cott is h i g h l y c o m p r e s s e d , w i t h a n a l m o s t acute w h o r l section. Franziceras spp. f r o m N e v a d a are described in G u e x (1989). Caloceras HYATT. T w o species of h i g h l y s e r p e n t i cone Caloceras w e r e collected f r o m beds K9 a n d K 1 0 - K l l a t K e n n e c o t t Point. Caloceras sp. 1 h a s a v o l u t i o n w h i c h is identical to C. aft. multicostaturn b u t its r i b b i n g is less dense.
SUMMARY
A l t h o u g h s o m e g e n e r a are not p r e s e n t at b o t h N e w York C a n y o n , N e v a d a a n d K e n n e c o t t Point, B. C., t h e r e is sufficient i n f o r m a t i o n to m a k e r e a sonable correlations b e t w e e n t h e t w o s e q u e n c e s , T h e s e two s e q u e n c e s s u p p l e m e n t e d b y o t h e r m u c h less c o m p l e t e s e q u e n c e s will f o r m t h e b a s i s for a N o r t h A m e r i c a n a m m o n i t e z o n a t i o n for the H e t t a n g i a n stage. A c k n o w l e d g m e n t s - The authors wish to thank David Taylor for his valuable comments on the Upper Hettangian ammonites from Kennecott Point.
REFERENCES BLOOS G. 1983 - The Zone of Schlotheimia marmorea (Lower Lias) - Hettangian or Sinemurian?. Newsletter on Stratigraphy, 12 : 123-131. BLOOS G. 1988 - Ammonites marmoreus OPPEL (Schlotheimiidae) im unteren Lias (Angulata-Zone) von Wtirttemberg (Stidwestdeutschland). Sttuttg. Beitr. Naturk., B-141 : 1-47. DESROCHER A. • ORCHARD M.J. 1991 - Stratigraphic revisions and carbonate sedimentology of the Kunga Group (Upper Triassic-Lower Jurassic), Queen Charlotte Islands, British Columbia. In WOODSWORTH G.J. (ed) : Evolution and hydrocarbon potential of the Queen Charlotte Basin, British Columbia. Geol. Surv. Canada, P a p . 90-10 : 164-172. FREBOLD H. 1967 - Hettangian ammonite faunas of the Taseko Lakes area, British Columbia. Geol. Surv. Canada, 158. GUEX J. 1980 - Remarques pr61iminaires sur la distribution stra'tigraphique des ammonites hettangiennes du New York Canyon (Gabbs Valley Range, Nevada). Bull. Ggol. Univ. Lausanne, 250 : 127-140; GUEX J. 1982 - Relations entre le genre Psiloceras et les Phylloceratida au voisinage de la limite TriasJurassique. Bull. Gdol. Univ. Lausanne, 260 : 47-51. GUEX J. 1989 - Note sur le genre Franziceras Buckman (Ammonoidea, Cephalopoda). Bull. Gdol. Univ. Lausanne, 305 : 347-354. MULLER S.W. & FERGUSON H.G. 1939 - Mesozoic stratigraphy of the Hawthorne and Tonapah quadrangles, Nevada. Bull. Geol. Soc. Am., v. 50. PALFY J. 1991 ~ Uppermost Hettangian to Lowermost Pliensbachian (Lower Jurassic) biostratigraphy :and ammonoid fauna of the Queen Charlotte Islands, British Columbia. University of British Columbia M.Sc. thesis. RICCARDI A.C., DAMBORENEA S.E., MANCENIDO M.O. & BALLENT S.C. 1989 - Hettangiano y Sinemuriano marinos en Argentina. In V. Congresso Geologico Chileno. Departamento Geologico y Geofisico, Universidad Chile, 2 : C359-C373. SMITH P.L., TIPPER H.W., TAYLOR D.R. & GUEX J. 1988 An ammonite zonation for the Lower Jurassic of Canada and the United States : the Pliensbachian. Calz. J. Earth Sc., 25 : 1503-1523. -
T h e H e t t a n g i a n f a u n a s at K e n n e c o t t P o i n t r e p r e s e n t a l m o s t a c o m p l e t e succession.
483 TAYLOR D. 1986 - The H e t t a n g i a n - S i n e m u r i a n boundary ( E a r l y J u r a s s i c ) : Reply to Bloos 1983. Newsletter on Stratigraphy, 16 : 57-67. TAYLOR D.G. 1990 - Two species of Paraloceras from the C a n a d e n s e Zone ( H e t t a n g i a n - S i n e m u r i a n stages) in N e v a d a (USA). Bull. Gdol. Univ., Lausanne, 309 : 211-219. TIPPER H.W., SMITH P.L., CAMERON B.E.B., CARTER E.S., JAKOBS G.K. & JOHNS M.J. 1991 - Biostratig r a p h y of the Lower J u r a s s i c formations of t h e Queen C h a r l o t t e Islands, B r i t i s h Columbia. In WOODSWORTH G.J. (ed) : Evolution and hydrocarbon
potential of the Queen C h a r l o t t e Basin, British Co. lumbia. Geol. Surv. Canada, P a p . 90-10 : 203-205. H.W. T I P P E R Cordilleran Division Geological Survey of Canada 100 West Pender Street Vancouver , B.C. V6B 1R8, Canada
J. GUEX Institut de G~ologie Geological Survey of Canada Contribution n ° 26691 BFSH-2 CH-1015, Lausanne