Sedimentology, stratigraphy, and clast biostratigraphy ...

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Sedimentology, stratigraphy, and clast biostratigraphy of Cretaceous and Tertiary strata, northeastern Ellesmere Island, Nunavut C.C. Lee1, O. Lehnert2, and G.S. Nowlan3 Lee, C.C., Lehnert, O., and Nowlan, G.S., 2008. Sedimentology, stratigraphy, and clast biostratigraphy of Cretaceous and Tertiary strata, northeastern Ellesmere Island, Nunavut; in Geology of Northeast Ellesmere Island Adjacent to Kane Basin and Kennedy Channel, Nunavut, (ed.) U. Mayr; Geological Survey of Canada, Bulletin 592, p. 115–167.

Abstract: The Eureka Sound Group clastic deposits on northeastern Ellesmere Island make up over 3 km of strata of Late Paleocene–Early Eocene age and were deposited in braidplain to alluvial fan and alluvial plain environments. The new Pavy Formation is the oldest unit, and consists of coarse-grained, volcanic-rich, channel-deposit sandstone displaying abundant, decimetre-scale trough-crossbedding. Boulder polymictic orthoconglomerate typifies the alluvial fan deposits of the Cape Lawrence Formation and grades into the fine-grained calcarenite of the Cape Back Formation, deposited in a floodplain environment. The mineralogy reflects the changing nature of the tectonic regime resulting from the movements between Canada and Greenland during the Late Paleocene. Clasts in the conglomerate yield faunas ranging in age from latest Cambrian to Early Devonian. Identified faunas and conodont colour alteration indices are highly variable and do not indicate a simple unroofing history.

Résumé : Dans le nord-est de l’île d’Ellesmere, les dépôts clastiques du Groupe d’Eureka Sound forment une accumulation de plus de 3 km de strates datant du Paléocène tardif à l’Éocène précoce. Ces sédiments se sont déposés dans des milieux s’étendant de la plaine à cours d’eau anastomosés au cône alluvial et à la plaine alluviale. La nouvelle Formation de Pavy est la plus vieille unité. Elle se compose de grès grossiers riches en débris volcaniques, qui se sont déposés dans des chenaux et présentent fréquemment une stratification oblique en auge d’échelle décimétrique. Les dépôts de cône alluvial de la Formation de Cape Lawrence sont caractérisés par un orthoconglomérat polygénique à blocs qui se fond dans la calcarénite à grain fin de la Formation de Cape Back, laquelle s’est déposée dans un milieu de plaine d’inondation. La minéralogie des roches du nord-est de l’île d’Ellesmere reflète le caractère changeant du régime tectonique de ce secteur, qui découle des mouvements survenus entre le Canada et le Groenland pendant le Paléocène tardif. Les clastes dans le conglomérat recèlent des faunes datant de la toute fin du Cambrien au Dévonien précoce. Les faunes identifiées et les indices d’altération de la couleur des conodontes sont très variés et ne témoignent pas d’une seule histoire de simple dénudation tectonique.

1

Husky Oil Limited, 707-8th Ave. S.W., Calgary, Alberta T2P 3G7, Canada Geological Institute, University of Erlangen, Schlossgarten 5, D-91054 Erlangen, Germany 3 Geological Survey of Canada (Calgary), 3303-33rd Street N.W., Calgary, Alberta T2L 2A7, Canada 2

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INTRODUCTION Maastrichtian through Eocene strata of the Canadian Arctic Islands are collectively known as the Eureka Sound Group (Table 1). This group encompasses nine formations of lithologically variable terrigenous siliciclastic deposits (Miall, 1986). Tertiary strata are preserved in seven outliers along the coast of northeastern Ellesmere Island (Fig. 1). These strata represent five formations of the Eureka Sound Group and are unique to the area. Based on fieldwork during the 1998–2000 field seasons, the stratigraphy of these strata has been revised by defining a new formation, the Pavy Formation, to replace what has been previously described as the Mokka Fiord Formation. The northernmost Tertiary outlier is at Watercourse Valley, situated northeast of Fort Conger (Fig. 1). The strata lie in a depression on the Paleozoic unconformity surface and are exposed in two adjacent streambeds. Exposures in the northernmost valley consist of a coarse breccia at the base, grading into fine-grained sandstone and siltstone, whereas rocks in the southern valley consist of coal at the base, which is overlain by fine-grained sandstone and siltstone of the Pavy Formation. The Pavy River and “Triangle” outliers occur near the Pavy and Daly rivers, respectively, on the northern tip of the Judge Daly Promontory (GSC map 2105A, CD-ROM). Strata in these two outliers are predominantly volcanicrich litharenite belonging to the Pavy Formation. The

“Triangle” outlier is bounded on three sides by normal faults and rests unconformably on the Danish River Formation on the fourth side. The Pavy River outlier is bounded by normal faults to the north, east, and west, and rests unconformably on the Eids and Thumb Mountain formations to the south. The most complete succession of the Eureka Sound Group occurs in the Cape Back outlier (GSC maps 2105A, 2102A, CD-ROM). Here, the Pavy, Cape Back, and Cape Lawrence formations are exposed and exhibit complex relationships. The strata here are bounded to the west by a thrust fault and to the east by a normal fault against Paleozoic carbonate. The Pavy Formation dominates the northern part of the outlier where it is bounded to the east and west by the above mentioned faults and sits unconformably beneath the Cape Back Formation to the south. In the southern part of the outlier, the Cape Lawrence Formation interfingers with the Cape Back Formation and is in structural contact with the underlying Pavy Formation. Basal conglomerate belonging to the Pavy Formation unconformably overlies the Thumb Mountain and Eids formations in this area as well. The Cape Lawrence Formation is the only Tertiary formation present at both the Cape Lawrence and Franklin Pierce Bay outliers (GSC maps 2102A, 2101A, CD-ROM). The Cape Lawrence outlier is situated north of Rawlings Bay and is bounded to the west by the northeast-trending Rawlings Bay thrust fault. The Franklin Pierce Bay outlier is situated south of Dobbin Bay and is bounded to the north by the east–west-striking Cape Hawks thrust fault. The basal

Table 1. Correlation of Cretaceous and Tertiary outliers on Judge Daly Promontory as well as type sections for the Eureka Sound Group

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contact at Franklin Pierce Bay is unconformable with various Cretaceous (Kanguk, Christopher, and Isachsen) and Paleozoic (Allen Bay) formations. At Bache Peninsula, separate formations used farther north in the study area were not distinguished and the combined Eureka Sound Formation rests unconformably on Eleanor River Formation (GSC map 2101A, CD-ROM). Several small, poorly exposed occurrences of Cretaceous units are present in the Franklin Pierce Bay and Allman Bay regions. These formations are at the base of several thrust sheets where the Paleogene Cape Lawrence Formation forms the footwall. Owing to the poor exposure, the formations were identified mostly on the basis of biostratigraphic data. Three Cretaceous formations – the Isachsen, Christopher, and Kanguk are present – but no detailed examinations were made during the fieldwork for this project. The descriptions and ages presented here are paraphrased mainly from de Freitas and Sweet (1998) and are supplemented by additional observations made in 1998. In this study, hundreds of clasts from the Pavy River, Cape Back, and Cape Lawrence formations were dissolved for conodont retrieval in order to determine the provenance of the clasts. The ability to determine the formation of origin for clasts is based on the earlier work on conodont faunas from the Cambrian, Ordovician, Silurian, and Devonian strata of the Arctic Islands. Key publications for interpreting the age and provenance of clasts include: Harrison (1995, Appendix 4), Mayr et al. (1994, Appendix 3), Nowlan (1985), Thorsteinsson and Mayr (1987), Thorsteinsson and Uyeno (1980), Trettin (1994; Appendix 3B by Nowlan et al.), Trettin (1998; Appendix 5B by Uyeno et al.) and Uyeno (1990). In addition, the thermal maturity of the clasts has been determined by examination of the conodont colour alteration indices (CAI) of the faunas. This technique is described by Epstein et al. (1977) and Rejebian et al. (1987) and its applications have been reviewed by Nowlan and Barnes (1986). Stratigraphic sections discussed in this study are described by Lee (2008). Relevant geological maps (CD-ROM) are by Harrison et al. (2007), Mayr et al. (2007), de Freitas et al. (2007) and Mayr and de Freitas (2007).

PREVIOUS WORK

Figure 1. a. Distribution of Cenozoic outcrops across the Arctic Islands (modified from Miall, 1991). b. Judge Daly promontory illustrating the distribution of Cenozoic outliers in the study area.

Two parallel lithostratigraphic schemes for the Eureka Sound Group (Table 1) were proposed simultaneously by Ricketts (1986) and Miall (1986). Contrasting nomenclature resulted from differing interpretations of the development of Cenozoic sedimentation. In the study area, Ricketts (1986) interpreted strata of the Iceberg Bay and Buchanan Lake formations to be regionally widespread occurrences, whereas Miall (1986) assigned the same strata to the Mokka Fiord, Cape Back, and Cape Lawrence formations, and suggested that deposition occurred in discrete basins.

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Cape Lawrence conglomerate at Franklin Pierce Bay was assigned a Cretaceous age by de Freitas et al. (1997). The presence of Lower Cretaceous palynomorphs in the supposedly Tertiary conglomerate had been known for some time (de Freitas et al., 1997), but until the structural relationships were discovered in 1998 (de Freitas and Sweet, 1998), the Cretaceous age presented a puzzle. De Freitas and Sweet (1998) then reassigned the conglomerate to a Paleocene age after finding rare micro- and macrofossils. Ricketts (1994) interpreted the conglomerate on Judge Daly Promontory to be equivalent to the Buchanan Lake Formation, which is Eocene in age. The presence of Paleocene flora found in conglomerate units was not addressed by Ricketts. The rocks of the newly proposed Pavy Formation were previously included in the Mokka Fiord Formation Miall (1986), a 1310 m thick siliciclastic unit present in most of the Eureka Sound basins.

CRETACEOUS FORMATIONS

Formation consists of white and brown weathering, poorly consolidated, fine-grained sandstone with ironstone concretions and coal. In some exposures coal forms about 50 per cent of the visible rock.

Age The palynological assemblage indicates a probable Albian age for the formation (de Freitas and Sweet, 1998).

Origin There is very little information on the Isachsen Formation in the report area, but this unit is typically divided into three members throughout the Sverdrup Basin and is interpreted to have origins varying from deltaic, to fluvial channel, to offshore-shelf depositional environments (Embry, 1991). The strata at the head of Allman Bay were likely deposited in a deltaic environment.

Isachsen Formation Definition

Christopher Formation

The Isachsen Formation was formally named and described by Heywood in 1957. In the type area on northwest Ellef Ringnes Island the unit is about 900 m thick and consists of fine- to medium-grained, buff, rusty, or grey weathering sandstone with thin coal beds in the lower part and large concretions in the upper part.

Definition

Distribution, thickness, and contact relations The Isachsen Formation structurally underlies the Allen Bay klippen east of the head of Franklin Pierce Bay (GSC map 2101A, CD-ROM). The next occurrence is farther toward the head of Allman Bay, where the formation stratigraphically underlies the Cape Lawrence Formation. Another small occurrence is in a structural window halfway between the head of Allman Bay and the mouth of Dobbin Bay. Thickness of the formation varies as it is preserved only in structural wedges. At the location west of the head of Allman Bay (field station 98-MSA-1) thickness is estimated at 60 m. The lower contact is faulted; in the area west of the head of Allman Bay the upper contact is unconformable with the overlying Cape Lawrence Formation.

Rock types In most areas the formation is poorly exposed and forms poorly drained, very muddy surfaces and unstable slopes. Vegetation on the Isachsen Formation is plentiful, in contrast to the lower Paleozoic carbonate surfaces. The Isachsen

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The Christopher Formation overlies the Isachsen Formation and was defined by Heywood (1957) for a series of black, laminated, fissile shale and silty shale. The type area is on northwestern Ellef Ringnes Island, where the formation is about 470 m thick.

Distribution, thickness, and contact relations The formation is present only in a small thrust slice just north of the head of Franklin Pierce Bay (GSC map 2101A, CD-ROM). The unit has been tectonically emplaced over Cape Lawrence Formation and in turn is overthrust by Silurian carbonate. Thickness is not known, but probably does not exceed a few tens of metres. No exposures were seen. The area where the formation is present is outlined by dark mud on the slope surface in contrast to the underlying lighter Cape Lawrence Formation, and only the presence of Middle Albian or younger palynomorphs (GSC loc. no. C-246355) distinguishes this occurrence from other Cretaceous units in the area. The Christopher Formation rests conformably over the Isachsen Formation.

Origin The Christopher Formation is interpreted to have been deposited in an offshore-marine to marine-shelf environment (Embry, 1991).

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Kanguk Formation

Age and correlation

Definition

Palynoflora present at Bache Peninsula (Sweet, 2008) include Sigmopollis sp., Sphagnum spp., Hamulatisporites sp. cf. H. amplus, Lycopodiumsporites sp., Azolla sp., Bohemisporites sp., ?Cryptogramma sp. A (rugulate), ?Cryptogramma sp. B (verrucate), Cyathidites/ Deltoidospora, Gleicheniidites sp., Hazaria sheoparii, Inaperturopollenites sp., Laevigatosporites spp., Leptolepidites sp., Matonisporites sp., Osmundacidites/ Baculatisporites, Radialisporis radiatus, Reticulosporis spp., bisaccate pollen, Podocarpidites sp., Rossipollis reticulatus, Sciadopityspollenites serratus, Alnipollenites verus, Betulaceae pollen, Caryapollenites sp., Cercidophyllidites sp., Ericipites sp., Liliacidites sp., Juglans sp., Liquidambar sp., Momipites wyomingensis, Paraalnipollenites alterniporus, Myricipites speciosus, Saxonipollis, Sparganium sp., Subtriporopollenites sp., Tetrapollis quadratus Manum 1962, Tetrapollis sp. (cf. Trudopollis resistens) in Manum, tricolpate pollen, tricolporate pollen, Trudopollis barentsii Manum 1962, Trudopollis resistens Manum 1962, Trudopollis rotundus Manum 1962, and Picea sp. The presence of Caryapollenites, Juglans, and Ericipites suggests a Late Paleocene age for the Bache Peninsula strata. However correlation with the Spitsbergen stratigraphy and the presence of Sciadopityspollenites serratus, Ericipites spp., Myricipites specious, Subtriporopollenites, Tetrapollis spp., and Trudopollis spp. pushes the age of these strata to the earliest Late Paleocene. Therefore it is currently suggested that the strata on Bache Peninsula could possibly represent the oldest Tertiary strata in the area.

The highest of the Cretaceous formations in the area, the Kanguk Formation, was first described by Souther (1963) from the west side of Axel Heiberg Island. There the formation consists primarily of silty shale interbedded with bentonite beds with lesser and variable amounts of sandstone. The formation is about 250 m thick.

Distribution, thickness, and contact relations The only known occurrence of the Kanguk Formation is at the base of the Cape Lawrence Formation klippe west of the head of Allman Bay (GSC map 2101A, CD-ROM). The exposure is poor and consists of vegetation-covered, dark mudrock. Thickness and stratigraphic relationships are unknown. Assignment of these rocks to the Kanguk Formation is based mainly on the presence of abundant dinoflagellates and microspores that indicate a marine depositional environment (de Freitas and Sweet, 1998).

Origin Offshore to shallow-marine shelf and prodelta deposits typify the depositional environment for the Kanguk Formation (Embry, 1991). Deposition of the Kanguk Formation strata was characterized by a restricted, stressful environment (Nunez-Betelu, 1994). These strata were starved, acidic, had a volcanic source (bentonite beds), and were bituminous at the base.

Pavy Formation Definition

TERTIARY FORMATIONS Eureka Sound Formation Discussion The formation was described by Christie (1967) and Kalkreuth et al. (1993) on Bache Peninsula as a 300 m thick succession of light brown or yellowish white weathering quartz carbonate sandstone and green-grey and grey-brown shaly sandstone with abundant shaly coal lenses and seams. These strata are preserved in a graben and unconformably overlie the Paleozoic Eleanor River Formation. Pollen and spore assemblages at Bache Peninsula indicate an age of earliest Late Paleocene (Sweet, 2008; 07-ARS-2001). During the course of the project the rocks were visited only briefly and no detailed stratigraphic analysis was made. Strata of the Eureka Sound Formation were deposited in a broad valley in fluvial-lacustrine environments and were probably subjected to a temperate climate with moderate precipitation as well (Kalkreuth et al., 1993).

A new formation, the Pavy Formation, is here defined to describe the oldest, mappable Cenozoic strata on Judge Daly Promontory. These rocks were previously included in the Mokka Fiord Formation and in the Cape Back Formation present in the Pavy River outlier (Miall, 1986). The Mokka Fiord Formation varies greatly in age from the Maastrichtian to the Early Eocene, is lithologically heterogeneous, and rests unconformably on either Paleozoic or Mesozoic strata across the Arctic Islands. The description of the type section, at Mokka Fiord on Axel Heiberg Island, can be found in Miall (1986). The formation is characterized by Miall as “thick units of crossbedded sandstone, pebbly sandstone, conglomerate, and thin coal that occur in most of the Eureka Sound basins”, which is unlike the rocks here assigned to the Pavy Formation. The upper contact of the Mokka Fiord Formation is either gradational with the Boulder Hills Formation or is the present-day erosional surface. Correlatable formations are the Margaret, Mount Lawson, Mount Moore, Vesle Fiord, and Mount Bell formations. Based on the heterogeneity of

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the characteristics of the Mokka Fiord Formation across the Arctic Islands, it is highly questionable whether the volcanic-rich strata prevalent on Judge Daly Promontory, in the Cape Back, “Triangle”, Pavy River, and Watercourse Valley outliers, should also be assigned to this formation. Therefore it is proposed that the term Pavy Formation be used in place of Mokka Fiord Formation on Judge Daly Promontory. These strata represent a unique mineralogical assemblage. Unlike the Mokka Fiord Formation, they are rich with volcanic lithic fragments. The type section (Stratigraphic Section 1, field station 00-CCL-3, Fig. 1, in Lee, 2008), 738.1 m thick (Fig. 2, 3 4a), is situated at the northern end of the Cape Back outlier. The formation is predominantly a trough-crossbedded, volcanic-rich, lithic sandstone, pebbly sandstone, and mudrock containing abundant well-rounded, coarse sand sized grains of relatively fresh igneous lithic fragments and plant debris, locally interfingering with or overlying mono-to-polymictic breccia and conglomerate units as well as fine-grained calcarenite. The type section of the Mokka Fiord Formation was described as thickly crossbedded sandstone, pebbly sandstone, conglomerate, and thin coal (Miall, 1986).

Distribution, thickness, and contact relations The Pavy Formation is the most widespread of the Cenozoic units on northeast Ellesmere Island. This formation outcrops in the Pavy River, the “Triangle”, the Cape Back, and the Watercourse Valley outliers (Fig. 4b). Strata belonging to the Pavy Formation are distinguished from the air by a characteristic dark brown, rubbly weathered appearance. This formation varies in thickness from 738.1 m at Cape Back (Fig. 4a) to approximately >1000 m at Pavy River (Miall, 1982) to 42.4 m at Watercourse Valley. Strata in the “Triangle” outlier are fault bounded against the Ordovician Ninnis Glacier and Bulleys Lump formations to the west, and Thumb Mountain, ?Bay Fiord, and Eleanor River formations to the east (GSC map 2105A, CD-ROM). To the south, the strata unconformably overlie the Danish River sandstone. In the Pavy River outlier, these strata are fault bounded against the Cambrian and Ordovician Hazen C and D, Cass Fjord, and Cape Clay formations to the west and east. Where the contact is not faulted, these strata unconformably overlie the Eids and Thumb Mountain formations to the south and the Eids Formation to the north. At Cape Back, the base of the Pavy Formation is exposed only in the southern part of the outlier; this contact is unconformable with the Eids Formation.

Rock types and internal stratigraphy Six depositional facies are distinguished in the Pavy Formation. The most commonly occurring lithofacies is a brownish green weathering, trough-crossbedded, coarse-

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Figure 2. Stratigraphic litholog for the type section of the Pavy Formation, Cape Back outlier. Refer to text and Table 2 for description of lithofacies, and Lee (2008, stratigraphic section 1) for detailed description of measured section. See Figure 3 for legend.

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outlier (Fig. 4f). This unit varies from resistant to friable and recessive. This facies is the dominant lithology in the Pavy Formation and is present in the Cape Back, “Triangle”, Pavy River, and Watercourse Valley outliers.

Lithofacies PaMf: dark green-grey silty mudstone Intermittent centimetre-scale beds of dark green-grey weathering and fresh siltstone are present in this dominantly mudrock unit. The bedding varies from centimetre scale to fissile with local iron-sulphide-rich beds, centimetre-scale fragments of petrified wood, abundant carbonaceous fragments, and rare gastropods and bivalves. This facies is present in the Cape Back, “Triangle”, and Pavy River outliers.

Lithofacies PaSr: fine upper to medium lower current-rippled sandstone

Figure 3. Legend for stratigraphic sections.

grained lithic sandstone. Interbedded with this facies are mudrock, siltstone, and pebble conglomerate, and rare coal seams. The most abundant lithofacies are the crossbedded lithic sandstone (PaSc) and the dark green-grey silty mudstone (PaMf), which dominate most of the measured sections. Only rare interbeds of the other four lithofacies occur. (See Fig. 2 for stratigraphic log of the type section, Fig. 3 for legend, and Table 2 for summary of facies. Note that not all the lithofacies are present in the type section.)

Lithofacies PaSc: fine upper to very coarse upper crossbedded lithic sandstone It is predominantly a homogenous lithic sandstone with a distinctive medium brown-grey weathered and fresh colour and rubbly appearance (Fig. 4c). Grain size ranges from 32 µm (fU) to 4 mm (vcU) and is composed primarily of rounded, abundant igneous fragments, quartz, chert, feldspar, and mica grains. Decimetre- to metre-thick, trough (Fig. 4d) and planar cross-stratification, and graded beds occur throughout. Bedding is planar, wavy, graded and varies from millimetre to decimetre scale. Sedimentary structures include centimetre-scale crossbeds, flame structures, convolute bedding, parallel laminae, and load casts. Centimetre-scale basalt clasts with desert varnish surfaces occur in lenses throughout the unit. Centimetre- to decimetre-scale wood fragments, plant debris, and calcareous concretions are also present. A variety of well-rounded cobble-sized igneous and siliciclastic clasts are seen only at the southern end of the Cape Back

This unit is green-grey weathering and medium to light grey-brown when fresh, and ranges in grain size from 32 µm to 125 µm. Bedding is planar and wavy, centimetre to decimetre in scale, and is cyclical, varying from millimetrescale fissile beds to centimetre-scale more resistant beds. Centimetre-scale asymmetrical current ripples and climbing ripples, decimetre-scale crossbeds, coaly stringers, and abundant plant fragments are also present. This facies is present only in the Cape Back outlier.

Lithofacies PaSStC: Interbedded siltstone, finegrained sandstone and coal This unit comprises a brown weathering, thin- to medium-bedded, interbedded siltstone and very fine-grained sandstone, and coal. Thickness of the coal varies from a few centimetres at Pavy River up to 6 m at Watercourse Valley. This facies is present in the Pavy River and Watercourse Valley outliers only (Fig. 4b).

Lithofacies PaScb: current-rippled very fine upper to fine upper carbonate clast sandstone This unit is a yellow-grey weathering, medium grey fresh, calcareous, current-rippled, parallel-laminated, micaceous sandstone with abundant plant and wood fragments, and non-diagnostic gastropods. The grain size ranges from 8 µm to 63 µm and grains are well sorted and well rounded; the bed thickness varies from 3 to 50 cm. Lenses of clastsupported extraformational carbonate clast conglomerate with subrounded to well-rounded dark grey wackestone clasts (median clast size of 2 cm) also occur. This facies is present only in the Cape Back outlier.

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Figure 4. Pavy Formation. a. Aerial view toward the northwest of the type section, northern end of the Cape Back outlier GSC Photo No. 2007-349). b. Interbedded fine-grained sandstone, siltstone, mudstone, and coal, capped by trough-crossbedded sandstone of lithofacies PaSc characteristic of the Watercourse Valley outlier. Height of outcrop is approximately 30 m (GSC Photo No. 2007-309). c. Metre-scale coarsening upward cycle (coarsening to the left), from mudrock to coarse-grained, trough-crossbedded sandstone of the Pavy formation, southern end of the Pavy River outlier GSC Photo No. 2007-256). d. Decimetre-scale trough crossbedding, type section at the Cape Back outlier. Width of trough is less than 1 m (GSC Photo No. 2007-343). e. Monomictic basal conglomerate, southwestern margin of the Pavy River outlier. Clasts are subangular to angular, decimetre scale, and composed dominantly of micrite. Hammer is 33 cm long (GSC Photo No. 2007-347). f. Well-rounded, varnished basalt clasts (indicated by arrows) of lithofacies PaCp, Cape Back outlier. Hammer is 33 cm long (GSC Photo No. 2007-262).

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Lithofacies PaCb: Mono- to polymictic para- to orthoconglomerate and breccia Overall this unit has a weathered and fresh grey-brown colour. The clasts are well rounded to angular, poorly to moderately sorted, vary from high to low sphericity, contain point-to-point and concavo-convex boundary contacts (Fig. 4e), and have a maximum clast size of 3 m (light greybrown lime mudstone), and a median clast size of 4 cm. The larger boulders are angular to subrounded and are composed Table 2. Summary of facies analysis for the Pavy Formation

Facies

Description

Interpreted depositional environment

Key features Medium brown-grey, Fine upper to abundant sand grains to very coarse cobble igneous clasts, Channel upper varnished clasts, PaSc* deposits of a crossbedded decimetre- to metre-thick, braided river lithic trough and planar crosssandstone stratification, graded beds, abundant plant debris Fissile, with occasional iron-sulphide-rich beds. dark green Backswamp Petrified wood and PaMf grey silty ponds or abundant carbonaceous mudstone shallow lake fragments. Rare gastropods and bivalves Green-grey weathering, fine upper to medium to light greymedium brown fresh. Current PaSr lower current- ripples and climbing Marginal lake rippled ripples, crossbeds, coaly sandstone stringers, abundant plant fragments Brown weathering, thin-to Interbedded medium-bedded siltstone siltstone, fineand very fine-grained Floodplain PaSStC grained sandstone with lenses of deposits sandstone paraconglomerate and and coal coal seams current Yellow-grey weathering, rippled very medium grey fresh, fine upper to calcareous, current PaScb fine upper rippled, parallel laminated; Marginal lake carbonate Abundant plant and wood clast fragments, and sandstone gastropods Clasts are well rounded to angular and poorly sorted. Maximum clast size is 3 Mono- to m. Composition mainly a polymictic variety of carbonate clasts para- to (dm–m scale); smaller PaCb Debris flows orthoconglo- clasts are angular to merate and rounded, mainly basalt, breccia sandstone, quartzite, chert, siltstone, and micrite. Maximum size 5 cm. *Facies are annotated by the abbreviation of three aspects: the formation name (capital letter), the dominant lithology (capital letter), and a prominent characteristic of the facies (small letter). For example, PaSt, Pa refers to the Pavy Formation, S refers to sandstone, and t refers to trough crossbedding.

mainly of carbonates (wackestone, burrow mottled wackestone, micrite, dolostone. The smaller clasts are angular to rounded, concentrated in lensoid beds, and are composed of mainly basalt, brown weathering sandstone, quartzite, chert, siltstone, and micrite. The smaller clasts range in size from 0.2 to 5 cm. No imbrication or sedimentary structures were observed. The matrix is a grey-green weathering and fresh, very fine lower to medium-grained calcareous sandstone. At Cape Back, polymictic pebble orthoconglomerate occurs and is composed of primarily subangular to rounded carbonate clasts. Composition of the basal conglomerate at Pavy River is dominated by the Hazen Formation (Divisions C and D) clasts to the northwest whereas Cass Fjord and Cape Clay formations are represented to the southeast. At the “Triangle” outlier the clasts are predominately composed of Cape Clay Formation lithologies. In the Cape Back outlier, a variety of Paleozoic carbonate clasts make up the conglomerate at the southern end (see Trettin, 1994 for full description of the Paleozoic strata).

Mineralogy Non-quartzose lithic fragments The most abundant mineralogy of the Pavy Formation is the igneous lithic fragment component, composing up to 47 per cent of the total mineralogy (Fig. 5c). It occurs in lithofacies PaSc, PaSr, and PaSStC. Volcanic varieties include basalt, trachyte (Fig. 5a), vesicular basalts, trachytic ?andesite (Fig. 5d), trachytic basalt amphibolite, and rhyolite. Chalcedony and microcrystalline chert represent up to 9 per cent of the total minerals. Other components include unaltered clinopyroxene (Fig. 5b), aegirine/augite, clinoamphibole, muscovite, olivine, and minor amounts of nepheline, carbonate, and granite lithic fragments. These minerals make up approximately 20 per cent of the total. Calcite cement and varying proportions of clay material occur as rims around grains and infill pore spaces. In lithofacies PaScb and PaCb the dominant lithic fragments are subrounded to rounded carbonate grains making up 73 per cent of the total. Rare plant debris and shelly fragments are also present in this lithofacies.

Quartz Quartz varieties present in lithofacies PaSc include monocrystalline, monocrystalline undulatory, and polycrystalline (two or more grains) varieties. Grains are subrounded to well rounded, commonly with embayed corroded edges, and concavo-convex grain boundaries. Quartz overgrowths and inclusions are rare. Monocrystalline undulatory quartz grains dominate in the outliers comprising up to 20 per cent of the total minerals at the Cape Back outlier. Lesser amounts of the polycrystalline and monocrystalline varieties are also

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present, making up 5.3 per cent of the total mineralogy. Quartz is also present in lithofacies PaSr, PaSStC and in trace amounts in lithofacies PaCb and PaScb.

Feldspar Feldspar grains occur as seriticized, angular to subangular grains and make up 4 per cent of the total minerals in lithofacies PaSc. Feldspar varieties include plagioclase, oligioclase, and microcline. Feldspar also occurs in lithofacies PaSStC in trace amounts. Composition of the Pavy Formation sandstone varies from quartzarenite to litharenite when plotted on Folk et al.’s (1970) ternary diagram for sandstone classification (Fig. 6).

A geographical trend in the maturity of the sandstone is observed increasing from south (Cape Back outlier) toward the north (Watercourse Valley outlier) in the Pavy Formation. Samples from the Cape Back and “Triangle” outliers plot entirely in the litharenite region, whereas compositions from the Pavy River outlier vary from litharenite to sublitharenite. Samples from Watercourse Valley outlier, the northernmost locality, plot in the litharenite, sublitharenite, and quartzarenite regions. The lithic component of these sandstones is made up entirely of volcanic fragments. Dominant clay mineralogy of the Pavy Formation, in lithofacies PaSc, consists of smectite, chlorite, illite/mica, corrensite, and mixed-layer chlorite and smectite. In the “Triangle” outlier, X-ray diffraction patterns demonstrate that the smectite is near pure, 100 per cent expandable form.

Figure 5. Photomicrographs of the lithic fragments of the Pavy Formation volcanic-rich sandstone from the Cape Back, Triangle, and Pavy River outliers. a. Well-rounded trachyte fragments, rimmed with smectite and encased in calcite cement. Sample 99-122A, Pavy River outlier; magnification 10x, XPL. b. Rounded pyroxene grain with slightly corroded edges encased in calcite cement. Sample 99-106, Triangle outlier; magnification 10x, XPL. c. Well-rounded volcanic fragments in subangular plagioclase. These grains are rimmed with smectite (indicated by arrows) and encased in a calcite cement. Sample 00-47, Cape Back outlier; magnification 4x, XPL. d. Basaltic trachy andesite with phenocrysts of the basal sections of augite exhibiting also glomeroporphyritic textures. Sample #60; magnification 4x, XPL.

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The following is a summary from Sweet (2008). Pollen typical of the Pavy Formation include Sphagnum spp., Sigmopolis sp., Zilvisporis sp., Hamulatisporites sp. cf. H. amuplus, Lycopodiumsporites sp., Caryapollenites sp., Ericipites sp., Ulmipollenites undulosus, Cupaniidites sp., ?Cryptogramma sp. A (rugulate), ?Cryptogramma sp. B (verrucate), Cyathidites/Deltoidospora, Gleicheniidites sp., Hazaria sheoparii, Insulapollenites rugulatus, Tilia sp., Laevigatosporites spp., Leptolepidites sp., Matonisporites sp., Osmundacidites/Baculatisporites, Radialisporis radiatus, Reticulosporis spp., Inaperturopollenites insignis, Sciadopityspollenites serratus, Aceraceae pollen, Alnipollenites verus, Tetrapollis quadratus, T/C/T pollen and Equisetum spores, bisaccate pollen, Betulaceae pollen, Momipites wyomingensis, Paraalnipollenites alterniporus, and tricolpate pollen, from the Cape Back outlier.

Figure 6. Ternary composition plots illustrating quartz (monocrystalline quartz, monocrystalline undulatory quartz, polycrystalline quartz varieties, and chert), lithic fragments, and feldspar, based on Folk et al.’s (1970) plots, for the Pavy and Cape Back formations.

Palynoflora present at Watercourse Valley include; Sphagnum spp., Lycopodiumsporites sp., ?Cryptogramma sp. A (rugulate), Cyathidites/Deltoidospora, Laevigatosporites spp., Matonisporites sp., Osmundacidites/Baculatisporites, bisaccate pollen, Sciadopityspollenites serratus, Alnipollenites verus, Betulaceae pollen, Caryapollenites

Mixed layer chlorite-smectite (C/S