Sverdrup Basin

Chapter 14

Sverdrup Basin Ashton Embry*,a, Benoit Beauchamp† *Geological Survey of Canada, Calgary, AB, Canada, †Department of Geoscience, University of Calgary, Calgary, AB, Canada

Chapter Outline Introduction Geological Setting Depositional and Tectonic History Phase 1: From Mountains to Depressions (Early Carboniferous) Phase 2: End of Rifting, Basin Enlargement, Repeated Quiescence, and Fault Reactivation (Late Carboniferous-Early Permian) Phase 3: Passive Subsidence and Biosiliceous Factory (Middle to Late Permian) Phase 4: Filling the Deep Basin (Triassic)

559 561 564 564

567 570 572

Phase 5: Shallow Seas (Latest Triassic-Earliest Cretaceous) Phase 6: Rejuvenation (Early Cretaceous) Phase 7: Quiescence (Late Cretaceous) Phase 8: Fragmentation and Uplift (Paleocene-Eocene) Tectonic Episodes Economic Geology Petroleum Coal Summary References

575 579 581 583 584 585 585 587 587 587

INTRODUCTION The Sverdrup Basin, a major Carboniferous to Paleogene depocenter in the Canadian Arctic Islands, was recognized during Operation Franklin, when the geology of the Arctic Islands was first systematically studied by the Geological Survey of Canada (Fortier et al., 1963). The basin occupies much of the Queen Elizabeth Islands and stretches for about 1300 km between northern Ellesmere Island on the northeast and Prince Patrick Island on the southwest. It is up to 350 km across (Fig. 1; “SVB” in Chapter 1, Fig. 13). About half of the 300,000 km2 area of the basin is land, with the remainder being inter-island channels. The basin fill consists of Carboniferous to Eocene strata that are estimated to be up to 13–15 km thick (Balkwill, 1978). The eastern portion of the basin was uplifted and deformed in the late Paleogene and is now a mountainous area. To the west, deformation was much less intense and the topography is subdued (Fig. 2). The folding and thrusting of the eastern portion have deformed the original shape of the basin and palinspastic restorations have not been attempted. Officers of the Geological Survey have described the outcropping strata in a series of publications and the pre1988 results are summarized in the Arctic Islands DNAG volume (Trettin, 1991). Publications such as Harrison (1995), Beauchamp (1995), and Beauchamp et al. (2001, 2009, 2013, in press) provide recent information on the Late Paleozoic succession, building from the pioneering work of Thorsteinsson (1974), Mayr (1992), and Davies and Nassichuk (1991a). Embry (1991a, 2011) summarizes the stratigraphy and depositional history of the Mesozoic succession. Ricketts (1994) and Ricketts and Stephenson (1994) are the most comprehensive summaries of Tertiary stratigraphy and paleogeographic evolution. Oil exploration in the basin began in 1968 and between 1969 and 1986 120 wells were drilled into Sverdrup Basin strata. Tens of thousands of kilometers of seismic lines were shot in the basin although most of these lines have not been studied in detail. The exploratory activity resulted in 18 discoveries with natural gas being the primary hydrocarbon found.

a

Ashton Embry is currently at the Embry Corp, Calgary, AB, Canada.

The Sedimentary Basins of the United States and Canada. https://doi.org/10.1016/B978-0-444-63895-3.00014-0 © 2019 Elsevier B.V. All rights reserved.

559

560  The Sedimentary Basins of the United States and Canada

FIG. 1  Outline of Sverdrup Basin with basin axis. The black dots represent the 120 wells drilled in the basin. The main sediment source areas lay to the south and east as indicated by arrows. A low-lying land area to the north (Crockerland) was a relatively minor source area except during the Late Triassic, when it was the dominant source area for the basin. TH, Tanquary High.

FIG. 2  Deformation zones of the basin with intensity of deformation decreasing westward.

The availability of a large amount of surface and subsurface data has allowed a reasonably good understanding of the regional depositional and tectonic history of the basin. As described in later sections, the development of the basin has been subdivided into eight phases, each of which is characterized by a unique combination of tectonic, depositional, and climatic factors. Each of these phases is stratigraphically represented by a first-order sequence.

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GEOLOGICAL SETTING The Phanerozoic geology of the Canadian Arctic Islands is summarized by Trettin (1989). From Cambrian through Early Devonian a passive margin basin, the Franklinian Basin, occupied the area. It was dominated by thick shelf carbonates and argillaceous basin deposits. The Ellesmerian Orogen, driven by the collision of a continental terrane with northern Laurentia, progressively deformed the Franklinian Basin from Late Silurian to the end of the Devonian (Colpron and Nelson, 2011). By Middle Devonian, the Franklinian Basin was transformed into a foreland basin and a siliciclastic wedge up to 10 km thick was deposited in front of the southwesterly advancing orogen (Embry 1988, 1991b). The Sverdrup Basin originated in the Early Carboniferous and it developed as a rift basin on the Siluro-Devonian Ellesmerian Orogenic Belt (Balkwill, 1978). The Ellesmerian Orogenic Belt of the Arctic Islands was part of an extensive Silurian-Devonian orogenic system that extended thousands of kilometers along the eastern and northern margins of Laurentia, from the Acadian Orogen of the Appalachians in the south, through the Caledonides of northern Europe and Greenland, to the southwestern end of the Ellesmerian belt in the northern Yukon (see Chapter 1). Notably, Carboniferous rift basins subsequently developed along much of this composite Siluro-Devonian orogenic zone (Ziegler, 1988). Such a regional shift from compression to extension suggests that a global plate tectonic reorganization occurred in Early Carboniferous and the occurrence of such a large-scale tectonic reorganization over much of North America has been noted in other chapters of this book. The Sverdrup Basin is the largest of these extensional “successor” basins that formed along the Caledonian/Ellesmerian orogenic belt during this major global restructuring. The basin probably owes much of its origin to the gravitational collapse of the Ellesmerian Orogen, which lost its compressional support in earliest Carboniferous time. The roll-back of a hypothetical subduction zone to the north could explain the end of compressional tectonics, the collapse of the orogenic belt, and the subsequent establishment of extensional tectonics in a back-arc setting (Beauchamp et al., in press). Alternately, or in addition to, far field stress changes associated with the Alleghanian-Variscan-Hercynian collision of Gondwana with Laurentia to the south may have led to a deviatoric stress reversal along its northern margin. The development of the basin can be conveniently described in terms of eight phases, with each phase having a distinct combination of tectonic, depositional, and climatic influences (Fig.  3). The strata of each phase comprise a first-order sequence and these sequences are bound by major, angular unconformities and correlative surfaces, indicating that a significant and short-lived tectonic episode, characterized by widespread uplift followed by collapse and a major transgression, initiated and terminated each phase. Lesser-magnitude tectonic episodes, marked by unconformities on the basin margins, occur within these phases and notable changes in depositional regimen often occur across such discontinuities. These unconformities bound second-order sequences. The first- and second-order sequences of the basin are illustrated and discussed in the next section. The lithostratigraphy of the basin is summarized in a regional, NE/SW, stratigraphic crosssection for the Sverdrup Basin (Fig. 4). Most of the first-order sequence boundaries correlate, plus or minus a stage, with the widespread unconformities that Sloss (1988) used to subdivide the Phanerozoic succession of the cratonic North America into six sequences with 16 component subsequences (see Chapter 2). The subsequences of Sloss that approximate the eight phases discussed in this chapter are: Phase 1—Kaskaskia II Phase 2—Absaroka I Phase 3—Absaroka II Phase 4—lower portion Absaroka III Phase 5—upper portion Absaroka III and Zuni I Phase 6—Zuni II Phase 7—Zuni III Phase 8—Tejas 1 The main sediment source areas for the basin were the adjacent Ellesmerian Fold Belt immediately to the east and south of the basin as well as the more distant Greenland and Canadian cratonic areas. The main bedrock in all these source areas consisted primarily of Devonian siliciclastic strata previously derived from the Caledonian/Ellesmerian Orogenic Belt (Patchett et al., 2004). A small land area, named Crockerland, lay to the northwest of the basin and it provided smaller amounts of siliciclastic sediments (Embry, 1993a, 2009; Anfinson et al., 2016) in Permian and Triassic (Fig. 5). The evidence for the existence of the land area consists mainly of the occurrence of shallow water, sandstone-dominant strata of Permian to Late Triassic age along the northwest margin of the basin. Such shallow water lithologies change facies to deeper water argillaceous strata southwards. The volumes of such northerly derived strata leave little doubt as to the ­existence of a

562  The Sedimentary Basins of the United States and Canada

FIG. 3  The eight phases of development with the characteristic features and timing of each phase. Each phase corresponds with a first-order sequence of the basin.

substantial land area to the north of the Arctic Islands from Permian through Late Triassic (Norian). The principal bedrock of Crockerland is interpreted to be Devonian siliciclastic strata (Embry, 1988; Anfinson et al., 2016). A prominent tectonic arch, the Tanquary High, extends into the northeastern portion of the basin (Nassichuk and Christie, 1969; Maurel, 1989; Embry, in press) (Fig. 1). It was a significant positive feature until latest Triassic and Carboniferous to Norian strata are truncated by sequential unconformities ranging in age from mid-Permian to Late Triassic on the flanks of the arch. The basal strata of Phase 5 (Rhaetian) overlie the crest of the arch and it was not a positive tectonic feature from Rhaetian onwards (Embry, in press). The Amerasia Basin portion of the Arctic Ocean lies northwest of the Sverdrup Basin and it is interpreted to have opened by the counterclockwise rotation of the Arctic Alaska-Chukotka Microplate (AACM) away from the Canadian Arctic Islands (Grantz et al., 2011). The basin is interpreted to have undergone a rift phase from latest Triassic to earliest Cretaceous (Rhaetian-Valanginian) with the formation of hyperextended continental crust and exposed mantle (Grantz et al., 2011; Chian et al., 2016) (Fig. 6). Once rifting began in latest Triassic (Embry and Anfinson, 2014; Anfinson et al., 2016), the Crockerland source region no longer supplied sediment to the Sverdrup Basin, although a narrow rift shoulder, the Sverdrup Rim, occurred along the northern flank of the basin and was an intermittent, minor source of sediment from latest Triassic through Cretaceous (Meneley et al., 1975; Embry, 1993a) (Fig. 6). The extended interval of rifting and hyperextension of the Amerasia Basin was followed by a period of sea floor spreading and the formation of oceanic crust in Early Cretaceous (Hauterivian-Albian) (Embry and Dixon, 1994; Grantz et al., 2011). During this time, a major volcanic ridge (Alpha-Mendeleev Ridge) up to 30 km thick built up in the northern portion of the basin, sourced by a mantle plume (Forsyth et al., 1986a, b; Buchan and Ernst, 2018). Basic intrusives and extrusives occurred on the adjacent continental areas including the Canadian Arctic Islands and the northern Barents Shelf (Embry and Osadetz, 1988; Maher, 2001; Buchan and Ernst, 2006; Drachev and Saunders, 2006). As will be discussed, the tectonic development of this nearby oceanic basin had a significant influence on the tectonic and paleogeographic development of the Sverdrup Basin.

Sverdrup Basin Chapter | 14  563

FIG. 4  NE-SW stratigraphic cross-section of Sverdrup Basin strata. Datum is base Barremian unconformity over much of the basin and the base Aptian unconformity on the basin flanks. Vertical exaggeration about 50× (Modified from Harrison and Jackson (2014).)

564  The Sedimentary Basins of the United States and Canada

FIG.  5  (A) Regional paleogeographic setting for Sverdrup Basin in the Permian and Triassic. Plate restoration following Grantz et  al. (2011). SB, Sverdrup Basin; W, Wrangel Island; C, Chukotka. (B) Schematic, NS cross-section across Sverdrup Basin, Permian–Triassic.

DEPOSITIONAL AND TECTONIC HISTORY Phase 1: From Mountains to Depressions (Early Carboniferous) Following the widespread erosion of the Ellesmerian Orogen, Early Carboniferous rifting proceeding in a general NS direction led to the creation of the E-W trending Sverdrup Basin, in part through extensional reactivation of older thrust faults in the Franklinian Basement (Harrison, 1995). The earliest rift development is recorded in the Emma Fiord Formation (Fig. 7), a unit known from a handful of outcrops on Devon, Axel Heiberg, and Ellesmere islands (Fig. 8), ranging in thickness from a few tens of meters to more than 700 m (Davies and Nassichuk, 1988). Viséan (Early Carboniferous) Emma Fiord sedimentation occurred in a range of lacustrine (shales, carbonates), fluvial (sandstones, conglomerates), and marginally marine (carbonates) environments. The Emma Fiord Formation is characteristically black due to its high organic content (Fig. 9A). It was deposited in a warm and humid and paleoclimate as shown by a rich palynoflora (Davies and Nassichuk, 1988). It is locally an oil shale with significant source rock potential (Fig. 9A).



Sverdrup Basin Chapter | 14  565

FIG. 6  (A) Regional paleogeographic setting for Sverdrup Basin, Middle Jurassic. The Amerasia Basin was expanding due to hyperextension of continental crust (see text). The Sverdrup Basin (SB) was separated from the Amerasia rift basin by Sverdrup Rim (SR), an uplifted rift shoulder. Plate restoration following Grantz et al. (2011). (B) Schematic, NS cross-section across Sverdrup Basin, latest Triassic-Cretaceous.

The second phase of rift development, evidenced by mappable facies distribution of syn-rift conglomerates (Thériault et al., 1993) and observation of growth faults on seismic profiles (Harrison, 1995; Beauchamp et al., 2001), led to a significant enlargement and interconnection of the rift system. This is recorded in the red-colored Borup Fiord Formation (Fig. 7) (Thorsteinsson, 1974), which lies unconformably on Emma Fiord strata, or directly on the Franklinian basement with a profound angular unconformity (Fig. 8). A variety of rift-related fluvial environments and their deposits are recognized, including alluvial fans and braid plain mass-flow and stream-channel conglomerates with Franklinian granules and pebbles derived from subbasin-bounding highs, to sheetflood sandstones and mudstones deposited along the axis of tectonic depressions (Thériault et al., 1993; Beauchamp et al., in press). Minor evaporites locally occur, which, in addition to the red coloration (Fig. 9B) and the widespread development of caliches, indicate a shift to a semiarid climate. Volcanics locally occur within (Trettin, 1988) or immediately above (Audhild volcanics; Thorsteinsson, 1974) the Borup Fiord Formation. The Borup Fiord succession passes upward into marine limestone of Serpukhovian age (late Early Carboniferous), indicating progressive marine invasion of the rift system from the northeast (Beauchamp et al., in press). Shortly after a significant base level drop, coinciding with the Mississippian-Pennsylvanian boundary (Early-Late Carboniferous boundary), led to widespread erosion of Borup Fiord strata and to the progradation of a wedge of marine sandstone in the distal basin axial areas where it lies in the lowest part of the Otto Fiord Formation (Mayr, 1992). That unconformity is a first-order sequence boundary (Fig. 9B) that marks the boundary between phases of development 1 and 2 (Fig. 3); it is locally angular resulting from erosion of rotated rift blocks (Beauchamp et al., in press).

566  The Sedimentary Basins of the United States and Canada

FIG. 7  Carboniferous stratigraphy of Sverdrup Basin. First-order sequences correspond with the tectonic phases of the basin.

N

1

2

3

Northern margin rifted away in Early Cretaceous

117 km

4

70 km

S

110 km

Raanes Nansen

Sakmarian Great Bear Cape

Artinskian

1000 m

Asselian Gzhelian

Kungurian

Kasimovian Moscovian Nansen

Trappers cove

Bashkirian Nansen

Bashkirian

Serpukhovian Emma Fiord

Hare Fiord

Hvitland Peninsula (Tellevak)

Borup Fiord

Viséan

Otto Fiord

Serpukhovian

Fluvial Sandtone and Shale Shelf / Reef Photozoan Carbonate

Fluvial / Alluvial Fan Conglomerate and Sandstone Shelf / Ramp Heterozoan Carbonate

Shelf / Ramp Chert

Subaqueous Evaporite Slope and Basin Carbonate and Chert Mudrock

FIG. 8  Stratigraphic sequences and formations of Phase 1 (Viséan and Serpukhovian) and Phase 2 (Bashkirian to Kungurian) of basin development along northern margin of Sverdrup Basin. Franklinian strata lie unconformably beneath the cross-section. Faults are conjectural. The sub-Moscovian unconformity marks the end of orthogonal rifting in the Sverdrup Basin, but many of the faults were reactivated (not shown) from the Gzhelian to Kungurian. Line of cross-section indicated in Fig. 10.



Sverdrup Basin Chapter | 14  567

FIG. 9  Field photographs of Sverdrup Basin strata of Phases 1 and 2 of development. (A) (Phase 1) Viséan Emma Fiord Formation, Grinnell Peninsula, NW Devon Island. (B) (Phase 1) Serpukhovian Borup Fiord (BF) Formation, unconformably overlain by Nansen (N) Formation, north side of Hare Fiord, NW Ellesmere Island. (C) (Phase 2) Bashkirian Otto Fiord (OF) Formation overlain by Moscovian Hare Fiord (HF) Formation, van Hauen Pass, NW Ellesmere Island. (D) (Phase 2) Moscovian to Kasimovian shelf edge-to-basin transition, Nansen (N) and Hare Fiord (HF) formations, head of Hare Fiord, NW Ellesmere Island.

Phase 2: End of Rifting, Basin Enlargement, Repeated Quiescence, and Fault Reactivation (Late Carboniferous-Early Permian) The lithostratigraphy and sequence stratigraphy of Phase 2 are illustrated in Figs.  7 and 10 and the phase comprises the entire Late Carboniferous and Early Permian. This phase of development started with a third pulse of rifting in the Bashkirian that led to reactivation of the previously developed half grabens and creation of new extensional structures along the northern and southern margins of the basin (Fig. 8). This is evidenced by growth faults and rotated blocks on seismic profiles (Harrison, 1995; Beauchamp et al., 2001) and the distribution of syn-rift conglomerates and evaporites. This led to both a significant deepening and major enlargement of the Sverdrup Basin tens of kilometers outboard of the previous Serpukhovian rift configuration (Thériault, 1991). Fault-controlled subsidence in the axial area led to the widespread invasion of marine waters, resulting in a cyclic succession of open- to restricted-marine carbonates and subaqueous evaporites (gypsum, anhydrite, halite). These rocks belong to the Otto Fiord Formation (Fig. 9C), which is up to 400 m thick in the outcrop belt, but a greater thickness was probably deposited along the basin axis as suggested by the occurrence of hundreds of diapiric structures piercing the overlying succession to the west (Nassichuk and Davies, 1980). Contemporaneous sediment accumulation at the basin margin comprises red-colored cobble to boulder conglomerates and sandstones of alluvial fan to braided river origin deposited in a series of fault-bounded tectonic depressions and passing upward into marginal marine carbonates and rare evaporites. Together, the Otto Fiord Formation and the correlative lower Canyon Fiord Formation are part of a second-order unconformity-bounded sequence (Fig. 7). The rapid transgression that followed, associated with a major base level rise in the Early Moscovian, coincided with the end of orthogonal rifting in the Sverdrup Basin—i.e., extension perpendicular to major basement structures (Beauchamp et al., 2001). This event is recorded by the drowning of the entire Sverdrup Basin area, a complete reconnection with the open ocean, a major invasion of the sea tens of kilometers inland (Middle limestone member, Canyon Fiord Formation), and the offshore growth of huge keep-up carbonate reef-mounds (Tellevak Member of Hvitland Peninsula Formation; Fig. 8), some of which attained thicknesses of up to 600 m before being drowned themselves (Davies and Nassichuk, 1991b). This gain in accommodation likely resulted from the onset of thermal subsidence associated with the cessation of rifting and fault-controlled subsidence.

568  The Sedimentary Basins of the United States and Canada

FIG. 10  Permian stratigraphy of Sverdrup Basin. First-order sequences correspond with the tectonic phases of the basin.

For the next 12 million years, the basin assumed a classic “steer’s head” geometry typical of basins that underwent a rift to postrift development (White and McKenzie, 1988). Previous half-graben highs and rift shoulders were eroded and/ or subsided and were blanketed by marine sediments (Fig. 8). The Late Moscovian to Kasimovian interval was marked by slower, regional, uniform, and passive subsidence. This allowed the progradation of a thick (1.5–2.0 km) peripheral carbonate platform (Nansen Formation) that transitioned basinward into slope to basinal mudrocks (Fig. 9D) (Hare Fiord Formation) in a deep (>1000 m) basin axial area (Fig. 10) (Beauchamp et al., 2013). Nansen shelf carbonates are typically arranged in a series of high-frequency sequences, or cyclothems, which were likely controlled by glacioeustatic fluctuations due to the advance and retreat of contemporaneous Gondawana glaciers, as suggested by the occurrence of similar cycles around the world (Heckel, 1986). Nansen carbonates pass southward into basin-fringing (Fig.  11), mostly fine-grained quartzose sandstones deposited in shallow subtidal to coastal plain environments (Upper clastic member, Canyon Fiord Formation; Fig. 7) and basinward into a large shelf-edge reef succession that is up to 1.5 km thick (Fig. 9D). Basin-fringing sandstones, or even just sand admixtures within Nansen carbonates, are absent from the northern margin of the basin (Fig. 8), suggesting Crockerland was little more than a very low-lying land at that time, one that may have been submerged and covered by carbonates most of the time. Correlative, yet substantially thinner, slope to basinal turbidites and mudrocks are contained in the Hare Fiord Formation (Fig. 8). These observations, plus the occurrences of a wide variety of tropicallike biotic and abiotic carbonate components, attest to a warm marine environment (Beauchamp and Desrochers, 1997), as the basin was located ~25–30°N. A significant base level drop prior to the end Carboniferous (Kasimovian-Gzhelian boundary) led to a widespread subaerial unconformity and coincides with the renewal of fault-controlled differential subsidence during the Gzhelian (Fig. 8). This was the first of four relatively short intervals of regional uplift and fault-controlled differential subsidence, during which some of the previously developed half-grabens continued to grow and others ceased to be active, while new depressions, fault-bounded highs, and broad flexures were developed. This suggests a reorganization of tectonic stresses, both in terms of magnitude and orientation, as orthogonal NS rifting of the previous phase gave way to a more complex history of transtension and transpression along a NW-SE principal compressional stress direction, and a secondary NE-SW

Crockerland

80º

º

0º

90

º

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º

0 11

10

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12

80

75º

Prince Patrick Island

70º

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85º

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?

1

?

2

0º

12

Axel

Banks Island

3

Heiberg Melville

4

Island Island

e er m d s le an El Isl 80º

Greenland 70º

80º

Km

60º

200

0 º

Shelf clastic Shelf/reef carbonate (photozoan) Slope & basin carbonate & chert mudrock

90

º

0 11

FIG. 11  Late Carboniferous paleogeography of Sverdrup Basin. Line of Fig. 8 cross-section (points 1–4) is indicated. (Modified from Beauchamp and Grasby (2012).)

extensional direction, thus oblique to most of the previous rift structures (Beauchamp et al., 2001). Recently documented detrital zircons of latest Carboniferous to Early Permian age suggest the presence of an active arc north of the area presently occupied by northern Axel Heiberg Island (Alonso-Torres et al., 2018). This further suggests active plate interaction along the basin’s northern margin, perhaps associated with renewed subduction and creation of a new compressional regime contemporaneous with the Uralian Orogeny along the eastern margin of Laurussia (Fig. 3). While subsidence remained generally rapid regionally, local highs developed, leading to the creation of a number of subbasins. One such subbasin (Fosheim-Hamilton Subbasin; Beauchamp and Olchowy, 2003) in west-central Ellesmere Island became isolated during the Early Permian and was the site of increasingly deepwater subaqueous evaporite sedimentation (upper Antoinette and Mount Bayley formations). This time marks also the onset of uplift along the Tanquary High, a major positive element that remained episodically active until the end of the Triassic (Embry, in press). Fault-controlled subsidence ceased abruptly during the late Asselian, once again associated with rapid base level rise, keep-up reef-mound development (Tolkien reefs of Beauchamp and Olchowy, 2003), cessation of evaporite sedimentation, creation of a major maximum flooding surface, and volcanism on Axel Heiberg Island (basalts in the upper Nansen Formation). Carbonate progradation resumed as recorded in up to 500 m of highly fossiliferous strata in the upper Nansen (Fig. 8) and Tanquary formations. The next major base level drop across the Asselian-Sakmarian boundary not only marked the renewal of differential, fault-controlled subsidence and uplift, it also coincided with a rapid environmental change as warm-water carbonates of the Nansen Formation gave way to cool- to cold-water carbonates of the overlying Raanes Formation and younger formations (Beauchamp and Henderson, 1994), an abrupt oceanographic event that has left a deep imprint all along the western margin of Pangea (Beauchamp and Baud, 2002). The Sakmarian Raanes Formation (100–250 m) marks the rapid onset of cool-water sedimentation in the Sverdrup Basin, as shown by the extensive deposition of carbonates with impoverished biota (Fig. 8) (heterozoan assemblage of James, 1997), a paleoceanographic event that has been largely associated with the closure of the Uralian seaway (Reid et al., 2007). The Sakmarian Raanes Formation (Fig.  10) is the first of two, mostly progradational, third-order sequences nested with the Sakmarian to Artinskian second-order sequence (Figs.  8 and 10). The second sequence is represented by the bulk of the 300 m thick Artinskian Great Bear Cape Formation and correlative deepwater Trappers Cove Formation. The Kungurian second-order sequence comprises carbonates (up to 250 m thick) contained in the upper part of the Great Bear Cape Formation and deepwater correlatives (Fig.  8). Kungurian carbonates also display cool-water heterozoan carbonates that pass basinward into pale grey to white chert of relatively shallow water origin (Beauchamp and Grasby, 2012). Kungurian carbonates pass landward into a thick succession of shallow subtidal sandstones and coastal plain sediments, interspersed with black coaly seams (Sabine Bay Formation), thus indicating a short-lived shift to more humid conditions. The Sakmarian, Artinskian, and Kungurian sequences prograded basinward during episodes of tectonic quiescence and passive subsidence (Fig. 8), following short-lived intervals of faulting and folding, volcanism (Esayoo Formation), rapid subsidence associated with tectonic stress relaxation and creation of maximum flooding surfaces (Embry et al., in press).

570  The Sedimentary Basins of the United States and Canada

Phase 2 ended in a series of events that changed forever the profile of the Sverdrup Basin succession. First a significant base level drop led to the widespread erosion of Sabine Bay sandstones and correlative carbonates and to extensive basinward progradation of both lithologies. Significant faulting, mostly compressional in nature, followed and this led to more erosion of Artinskian and Kungurian strata at the basin margin, as well as local folding and erosional stripping of even older formations. These events, of variable magnitude and extent in different parts of the basin, are collectively termed the “Melvillian Disturbance” (Thorsteinsson, 1974), which coincides with the Early to Middle Permian boundary (Fig. 3). Up until the Early Cretaceous, tectonic events, although undeniably present, left a far subtler imprint, mostly in the form of broad regional uplifts, than during the previous 80 million years. One notable exception is the Tanquary High area of northern Ellesmere Island, where evidence for repeated fault-controlled uplift until latest Triassic is undeniable (Embry, in press).

Phase 3: Passive Subsidence and Biosiliceous Factory (Middle to Late Permian) Phase 3 started with a major base level rise that drowned the previously exposed Sabine Bay and older formations and the stratigraphy of this phase is illustrated in Figs. 10 and 12. A deepening-upward succession of calcareous sandstones, and finer clastics, locally replete with brachiopods and bryozoans (Roadian Assistance Formation; up to 200 m thick), recorded a transgression that extended well beyond the preexisting margins of the basin (Fig. 12). This was contemporaneous with one last phase of Permian volcanism (northern Axel Heiberg and west-central Ellesmere Island), uplift and emergence of Crockerland, as shown by basin-fringing sandstones along the northern margin of the basin (Fig. 13). Maximum water depth coincided with the widespread deposition of black siliceous shale and spiculitic chert of the van Hauen Formation (up to 600 m), representing basinal to slope deposition (Fig. 12) (Thorsteinsson, 1974). These mudrocks pass upward into progressively shallower carbonates (Fig. 14A) (lower Degerböls Formation) and glauconitic sandstones (lower Trold Fiord Formation). Middle Permian (Wordian) carbonates of the Degerböls Formation contain an even colder biota than their Kungurian and Artinskian counterparts (Reid et al., 2007). Dropstones indicating the presence of at least seasonal ice have been reported at that level (Beauchamp, 1994). A major unconformity lies within the Degerböls and Trold Fiord formations (Fig. 12) (Beauchamp et al., 2009). The sediments that rest above comprise a Capitanian sequence of cherty carbonates, pale colored chert, and glauconitic ­sandstones that are fossil-poor with the exception of sponge spicules (upper Degerböls Formation). Following a base level drop at

S4

3

2

12 km

10 km

1N 20 km Trold Fiord

Wuchiapingian

Changhsingian

Degerböls (lower)

Lindström Degerböls (upper)

Capitanian van Hauen (upper)

Shelf/ramp sandstone

Wordian

Roadian

200 m

Assistance

Black Stripe

van Hauen (lower)

Shelf/ramp heterozoan carbonate

Shelf/ramp spiculic chert

Slope & basin carbonate & chert mudrock

FIG. 12  Stratigraphic sequences and formations of Phase 3 (Roadian to Changhsingian) of Sverdrup Basin development. Cross-section is overlain by uppermost Permian-Lower Triassic Blind Fiord Formation. Line of cross-section indicated in Fig. 13.

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85º

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Crockerland ? 0º

12

Axel

Banks Island

Heiberg Melville

Island Island

4

32

80º

1 Greenland 70º

80º

Km

60º

200

0 º

Shelf clasc Shelf / reef carbonate (heterozoan) Slope & basin chert & mudrock

90

º

0 11

e er m d s le an El Isl

FIG. 13  Middle Permian paleogeography of Sverdrup Basin. Line of Fig. 12 cross-section (points 1–4) is indicated. (Modified from Beauchamp and Grasby (2012).)

FIG. 14  Field photographs of Sverdrup Basin strata of Phase 3 of development. (A) Wordian van Hauen Formation passing upward into Degerböls Formation, West Blind Fiord, SW Ellesmere Island. (B) Upper Permian Black Stripe Formation overlain by Lower Triassic Blind Fiord Formation, Confederation Point, NW Ellesmere Island. Dashed red line coincides with the formation contact, the maximum flooding surface of the Early Triassic second-order sequence, and the P-T extinction event.

the end of the Capitanian, maximum water depth was once again recorded in the widespread development of black shales and cherts (Black Stripe Formation; Fig. 12). These dark mudrocks pass upward and landward into the Wuchiapingian Lindström Formation (up to 100 m thick), which comprises essentially nothing but sponge spicules deposited in a wide range of shallow to deepwater ramp environments (Fig. 14B) (“Glass Ramp” of Gates et al., 2004). Carbonate factories were thus eradicated, replaced by far less productive biosiliceous factories. While cool to cold temperatures played a role in stressing carbonates, Beauchamp and Grasby (2012) proposed that it was the influx of acidic onto the shelf all along the upwelled margin of NW Pangea that led to the eradication of carbonate producers, a unique phenomenon associated with the increase of CO2 in the atmosphere during the Late Permian. The Lindström Formation passes landward into nonfossiliferous, glauconitic sandstones of the upper Trold Fiord Formation (Fig. 12). There is evidence of Late Permian renewed tectonism and reactivation of old fault blocks along the northern margin of the basins (Northern Axel Heiberg Island) and along the Tanquary High, an event contemporaneous with the last pulse of the Uralian Orogeny to the east and the Sonoma Orogeny along the western United States (Fig. 3). Base level dropped significantly near the end of the Permian, subjecting the Lindstrom chert to widespread erosion and to contemporaneous progradation of the shallow chert facies well into the basin. The end of the Paleozoic Era was recorded in a deepening-upward wedge of black chert and shale that was deposited in the distal areas and onlapping the shelf margin (Fig. 14B), while the bulk of the Lindström shelf remained subaerially exposed. Filling that depression took the greater part of the Triassic.

572  The Sedimentary Basins of the United States and Canada

Phase 4: Filling the Deep Basin (Triassic) As the Paleozoic Era came to a close, the exposed flanks of the Sverdrup Basin were gradually being transgressed. A major base level rise initiated Phase 4 and the sea reached inland well beyond the previous margins of the basin. A large bathymetric difference, of probably more than 2 km, existed between the basin margins and basin axis. This deep basin began to form in the Early Carboniferous as rifting and then thermal subsidence progressed and continued to expand landwards. It deepened throughout the Late Paleozoic as subsidence rates of the central part of the Sverdrup Basin exceeded long-term sediment supply rates. A new depositional regime was established at the dawn of the Mesozoic Era. The climate was warm and dry, sedimentation was now siliciclastic dominated, and marine life was sparse and had nothing in common with its Permian counterpart. Phase 4 lasted until latest Triassic (base Rhaetian), when a major tectonic episode established very different depositional and tectonic regimes and initiated a new phase of basin development. The lithostratigraphy and sequence stratigraphy of Phase 4 are illustrated on Fig. 15, and Fig. 16 presents a stratigraphic cross-section for these strata from the eastern basin margin to a basin-center locality. Four second-order sequences comprise the first-order sequence of Phase 4 and each of these is characterized by distinctive depositional and tectonic regimes (Figs. 16 and 17). Early Triassic deltaic and marine strata are up to 2000 m thick and comprise the first second-order sequence (Fig. 15). Major deltas began to prograde into the basin from the south and east (Bjorne Fm) (Fig. 18A), and this huge siliciclastic supply was sourced mainly from Devonian siliciclastic strata that flanked the basin and extended over the craton. The sudden increase in siliciclastic supply suggests regional uplift of the cratonic areas was associated with the tectonic episode that initiated this new phase. The lack of plant-cover due to the preceding P-T extinction event also likely contributed to this increased supply (Midwinter et al., 2017). Throughout the Early Triassic, sandy deltas advanced into the basin (Embry, 1991a, 2011) and pushed the shelf/slope boundary a considerable distance to the north and west. Large submarine fans were deposited in the deep basin (Blind Fiord Fm) throughout the Early Triassic. Substantial sediment was also input from

FIG. 15  Triassic-Jurassic stratigraphic chart. First-order sequences correspond with the tectonic phases of the basin.



Sverdrup Basin Chapter | 14  573

FIG. 16  Stratigraphic cross-section of Phase 4 strata of eastern Sverdrup Basin. The deep central basin was filled during this time.

FIG. 17  Outcrop on Greeley Fiord, Ellesmere Island illustrating the four second-order sequences that comprise Phase 4 strata. B, Barrow Fm; Bj, Bjorne Fm; GP, Gore Point Fm; H, Heiberg Fm; HB, Hoyle Bay Fm; MH, Murray Harbour Fm; PB, Pat Bay Fm.

Crockerland (Embry, 1993a) (Fig. 18A) and detrital zircon data from these sediments indicate that Devonian clastic wedge strata were the primary source, with Permian igneous rocks being a local source in the northeast (Omma et  al., 2011; Anfinson et al., 2016; Alonso-Torres et al., 2018). Marginal uplift, followed by a major transgression, occurred at the Early-Middle Triassic juncture and subsidence and sediment supply rates were greatly reduced. Dark, bituminous mud and silt (Murray Harbour Fm) were widely deposited and minor progradation of shelf sandstones (Roche Point Fm) occurred from the eastern and southern margins

574  The Sedimentary Basins of the United States and Canada

FIG. 18  (A) Late Early Triassic (Spathian) paleogeography with major deltas along the eastern and southern margins of the basin. Thick submarine fans were deposited in the deep basin. Shallow shelf sands on the northern margin were derived from Crockerland. (B) Early Late Triassic (Carnian) paleogeography with Crockerland providing significant volumes of sediment. In the western portion of the basin, shelf sands prograded southward across the basin. A deepwater basin was located in the east.

(Figs. 16 and 17). Middle Triassic strata, which comprise a second-order sequence, do not exceed 300 m in thickness. Along the northwestern margin of the basin, these strata consist mainly of shale and siltstone, although very fine sandstone units of midshelf origin, cored in a well on the northern margin, are likely derived from Crockerland (Kondla et al., 2015). Following another tectonic episode of uplift and transgression in earliest Late Triassic, subsidence and sediment supply rates again significantly increased and a mixed carbonate/siliciclastic shelf/slope (Cape St Andrew, Gore Point formations) advanced well into the basin (Fig. 16). These strata are up to 1400 m thick. This advance was halted by another transgression in early Carnian but siliciclastic supply again quickly overwhelmed subsidence and sandy, inner shelf deposits (Pat Bay Fm) built seaward over mud and silt-dominated slope and outer shelf deposits (Hoyle Bay) (Figs. 16 and 17). Notably, in mid- to late Carnian, Crockerland was the predominant source of sediment for Sverdrup Basin and sandy shelf deposits (Pat Bay Fm) extended southward across the entire basin in the west (Fig. 18B) (Embry, 1993a; Anfinson et al., 2016).



Sverdrup Basin Chapter | 14  575

Detrital zircon data from these Crockerland-derived sediments reveal that on the southwestern portion of the northern margin, the primary locus of sediment input during the Carnian, Devonian siliciclastics of Crockerland were the primary source rocks. However, on the northeastern portion of the northern margin, Carboniferous-Triassic zircons have been identified in a Carnian sandstone (Omma et al., 2011), indicating that the Urals/Novaya Zemlya Orogen also supplied sediment to that portion of the Sverdrup Basin (Anfinson et al., 2016). As discussed in Anfinson et al. (2016), it appears that the final, Late Triassic phase of the Urals/Novaya Orogen (Zhang et al., in press) eliminated the seaway between the orogen and Crockerland, allowing drainage with headwaters in the orogen to extend all the way to the northeast Sverdrup Basin (see Fig. 7 in Anfinson et al., 2016). A transgression in mid-Late Triassic (latest Carnian) again pushed the shorelines to the basin edges. Following this, siliciclastic supply from Crockerland greatly increased and no sediment derived from the cratonic areas to the east and south of the basin have been identified within the Norian second-order sequence (Embry, 2011). During the Norian, shallow shelf sands (Romulus Mbr, Heiberg Fm) prograded across prodelta mud and silt (Barrow Fm) (1000 m) and the basin continued to fill from northeast to southwest (Fig. 19). Over 100,000 cubic kilometers of northerly derived sediment were deposited in the Sverdrup Basin during the Norian. By the end of the Norian, the deepwater, central portion of the Sverdrup Basin that had existed for over 100 million years had been filled, and a shallow seaway was present over most of the basin (Fig. 19A). Four Norian sandstone samples, located along a north-south transect in the eastern portion of the basin, all contain large quantities of Carboniferous to Late Triassic zircons, indicating that the Urals/Novaya Orogen was an important source region for the southwesterly prograding Norian clastics (Anfinson et al., 2016). Unpublished detrital zircon data from a sample from the southwestern portion of the northern margin (L. Heaman, personal communication, 2013) indicate that the Devonian clastics on Crockerland supplied that portion of the basin, although sediment input was very low compared with that of the northeast area. During Phase 4, salt domes and walls, derived from the Otto Fiord Fm, grew upwards in the central portion of the basin and sometimes formed emergent islands (Balkwill, 1978; Embry, 1991a; Harrison and Jackson, 2014).

Phase 5: Shallow Seas (Latest Triassic-Earliest Cretaceous) Widespread uplift terminated Phase 4 of basin development and in latest Triassic (near Norian/Rhaetian boundary) much, if not all, of the basin was subaerially exposed. This notable tectonic episode was coincident with the start of rifting of the adjacent Amerasia Basin (Embry and Anfinson, 2014) and the demise of the Tanquary High (Embry, in press). High rates of subsidence initiated Phase 5 and the exposed basin margins were transgressed in early Rhaetian (Fig. 20A). Phase 5 lasted until latest Valanginian, when basin-wide tectonic uplift terminated the phase. The lithostratigraphy and sequence stratigraphy of Phase 5 are illustrated in Fig. 15. As shown, the first-order sequence that encompasses the strata of Phase 5 consists of four second-order sequences, each characterized by a distinctive depositional and tectonic regime. Sedimentation and subsidence rates remained high during the second-order Rhaetian-Sinemurian sequence but, in contrast to the underlying Norian sequence of the previous phase, the sediment source areas lay to the east and south of the basin. The detrital zircon content of four samples from this sequence is very similar to that of Devonian clastic strata (O. Anfinson, personal communication, 2015), adding further support to the interpretation of Patchett et al. (2004) that these strata covered the cratonic areas at this time. Very little sediment entered the basin from the north where a narrow rift shoulder (Sverdrup Rim) separated the Sverdrup Basin from the initial rift basins of the proto-Amerasia Basin (Fig. 6). In latest Triassic and earliest Jurassic, major sandy deltas prograded from the east and southeast and much of the eastern and central basin became a vegetated, delta plain (Fosheim Mbr, Heiberg Fm) under a warm, temperate climate (650 m) (Figs. 20 and 21A). To the west, shoreline and marine shelf sand deposits (MacLean Strait Fm, King Christian Fm) prograded westward over prodelta and shelf mud and silt (Grosvenor Island and Lougheed Island formations) three times between early Rhaetian and latest Sinemurian (Early Jurassic) (Embry, 1993b; Embry and Johannessen, 1993) (Fig. 21B). In early Pliensbachian, sediment supply significantly waned and the sea transgressed the delta plain, initiating the next second-order sequence (Pliensbachian-Aalenian) and leaving a widespread blanket of marine sand in its wake (Remus Mbr, Heiberg Fm) (100 m). By late Early Jurassic (Toarcian), sedimentation and subsidence rates were low and a shallow sea receiving mainly mud and silt (Jameson Bay Fm) occupied the basin (Embry, 1991a, 1993b, 2011). Uplift in late Aalenian allowed a thin marine shelf sand unit (Sandy Point Fm) to prograde into the basin from the southern, eastern, and northern margins. Sedimentation and subsidence rates reached a nadir in Middle Jurassic (Bajocian-Callovian second-order sequence) and thin shale deposits (200 m) (McConnell Island Fm) of this age occur over most of the basin with shallow marine, sandstone units present in a few areas on the southern and northern basin margins (Hiccles Cove Fm) (Embry, 1993b). Notably, narrow rift basins related to the initiation of the Amerasia Basin developed south of the southwestern margin of the basin (southern Prince Patrick Island) where the underlying Ellesmerian structural trend is NS, parallel to the Amerasia

576  The Sedimentary Basins of the United States and Canada

FIG. 19  (A) Late Triassic (Norian) paleogeography with Crockerland being the only source of sediment. The highest input was in the northeast and the central basin was filled by southwestward progradation. (B) Stratigraphic cross-section of the Norian second-order sequence strata in the eastern Sverdrup Basin illustrating SW progradation.

rift (Harrison et al., 1988; Harrison and Brent, 2005). The normal faults terminate at the Sverdrup Basin margin, which coincides with the beginning of westerly trending Ellesmerian structures. Hadlari et al. (2016) speculated that the Sverdrup Basin also underwent rifting during Jurassic to earliest Cretaceous, coincident with the rift phase of the Amerasia Basin, but the lack of normal faulting anywhere in the basin during this time (T. Brent, personal communication, 2016), facies relationships and thickness trends (Embry, 1993b), and tectonic subsidence analysis (Stephenson et al., 1987, 1994) for the basin all indicate that rifting did not occur within the basin at this time.



Sverdrup Basin Chapter | 14  577

FIG. 20  (A) The first-order sequence boundary that bounds the base of Phase 5 strata occurs at the base of the Rhaetian-Sinemurian second-order sequence, here comprised of the deltaic strata of the Fosheim Mbr of the Heiberg Fm. Yelverton Pass, NE Ellesmere Island. (B) The Oxfordian-Valanginian second-order sequence comprises the upper portion of Phase 5 strata, and the first-order sequence boundary at the base of the Hauterivian-Barremian second-order sequence marks the boundary between Phase 5 and Phase 6 strata. Aw, Awingak Fm; DB, Deer Bay Fm; I, Isachsen Fm; R, Ringnes Fm. Lost Hammer Diapir, Central Axel Heiberg Island.

Subsidence and sediment supply rates increased at the beginning of the Late Jurassic (Oxfordian) following an episode of marginal uplift in the late Callovian. A series of wave-dominated deltas (Awingak Fm) separated by transgressive events prograded over shelf mud and silt (Ringnes Fm) towards the northwest (Embry, 1993b). The deltaic sandstones reach as far as the basin center, where this succession is up to 500 m thick (Figs. 20B and 22). Also, at the beginning of Late Jurassic normal faulting, south of Sverdrup Basin, extended to the Banks Island and mainland areas. This resulted in a seaway that linked the Sverdrup Basin to the Interior Seaway of western North America (see Chapter 9). The final deposits (250 m) of this phase are shelf muds and silts that occupied much of the basin in latest Jurassic and earliest Cretaceous (Deer Bay Fm) (Figs. 20B and 22B). Shoreline to shallow shelf sands (upper Awingak Fm) were deposited on the basin edge during much of this time with highly progradational, delta front sandstones (basal Isachsen Fm) occurring at the top of the succession (Fig. 22B). The salt structures that had been established in the Late Paleozoic continued to ascend and deform the strata. Large, local variations in thicknesses occur near these structures and a significant surge of upward movement occurred at the end of this phase (Fig. 20A) (Jackson and Harrison, 2006; Boutelier et al., 2011; Harrison and Jackson, 2014; Dewing et al., 2016a). The latest Triassic to earliest Cretaceous interval that was dominated by shallow offshore shelf deposits saw a major change in the general paleogeographic framework of Arctic Canada. This change was due to Amerasia Basin rifting,

578  The Sedimentary Basins of the United States and Canada

FIG. 21  (A) Latest Triassic (Rhaetian) paleogeography with a sandy deltaic plain occupying the eastern and central portions of the basin. Sediment input in the west was low and a shallow sea was present. (B) Stratigraphic cross-section of Rhaetian to Sinemurian strata (a second-order sequence that forms the lower portion of Phase 5) in the western Sverdrup Basin. The deltaic siliciclastics prograded westward.

which fragmented Crockerland and left a narrow positive area, Sverdrup Rim, separating the Sverdrup Basin from the proto-Amerasia Basin (Fig. 6). The Sverdrup Rim was part of a rift shoulder that marked the entire eastern margin of the Amerasian rift system and served as a minor, intermittent source area for the Sverdrup Basin. When it was emergent, it cut off the long-established connection between the Sverdrup Basin and the Chukchi Basin (Hanna Trough) of northern Alaska. A new seaway along the cratonic side of the rift shoulder was formed and it connected the interior seaway of western North America with the Sverdrup Basin. This phase was brought to a close by widespread uplift over the entire basin in the latest Valanginian-earliest Hauterivian interval (Embry, 1991a). This tectonic episode is interpreted to coincide with



Sverdrup Basin Chapter | 14  579

FIG. 22  (A) Late Jurassic (Kimmeridgian) paleogeography with a broad band of shallow marine sand along the eastern and southern flanks of the basin. A rift shoulder occurred along the northwest margin of the basin that now opened to the southwest. (B) Stratigraphic cross-section of the OxfordianValanginian second-order sequence in the eastern Sverdrup Basin. Three third-order sequences can be delineated.

the ­beginning of seafloor spreading and the initial formation of oceanic crust in the adjacent Amerasia Basin (Grantz et al., 2011) and the resultant unconformity is sometimes referred to as the “breakup unconformity” (Embry and Dixon, 1994).

Phase 6: Rejuvenation (Early Cretaceous) Subsidence rates substantially increased in the Sverdrup Basin following the major uplift that ended Phase 5. The tectonic regimen of the basin changed from one of slow, passive subsidence that had dominated the previous phase to one of

580  The Sedimentary Basins of the United States and Canada

renewed rifting and extension. Subsidence and sediment supply rates greatly increased and normal faulting and sporadic volcanism also characterize this developmental phase. Galloway et al. (2013) recorded a major palynoassemblage shift across the Phase 5/6 boundary and interpreted it to mark a climate change from a seasonally arid climate to a cooler and more humid one. Phase 6 lasted until latest Albian, when another tectonic episode resulted in widespread uplift, including folding on the basin margin (Embry, 2011; Dewing et al., 2016b). The first-order sequence that encompasses these Hauterivian-Albian strata consists of two second-order sequences (Fig. 23). Thick, coarse-grained, fluvial/deltaic sediments (Isachsen Fm) (max. 1000 m) (Figs. 20B and 24) comprise the first second-order sequence of Hauterivian to late Barremian age (Embry, 1991a; Tullius et al., 2014). Two transgressive marine intervals punctuate the succession and the strata progressively onlap the basin margins (Fig. 24). The coarseness and substantial volume of sediment demonstrate that the cratonic regions to the east and south must have experienced substantial uplift with the initiation of this phase. Detrital zircon analysis from four samples of Isachsen Fm (Røhr et al., 2010) indicate the Devonian clastic strata were still a dominant source for the clastics. However, the common presence of vein quartz pebbles up to 10 cm across within the fluvial strata leave no doubt that the Canadian Shield was also exposed now. Marginal uplift in latest Barremian was followed in Aptian by perhaps the largest transgressive episode in the history of the basin. The shorelines were pushed well onto the craton far to the east and south and the Sverdrup Rim was drowned. The basin received thick deposits of offshore mud and silt (Christopher Fm), which prograded northward (1100 m) (Embry, 1991a; Schroder-Adams et al., 2014) (Fig. 25). A shelf sandstone unit prograded into the basin in mid-Albian (top Invincible Point Mbr) (Fig. 25), but was subsequently drowned by another major transgressive interval. Late in Early Cretaceous, shoreline and shallow shelf sands (Hassel Fm) prograded into the basin from the south and east (200 m) (Figs. 25 and 26) and heralded widespread uplift in latest Early Cretaceous. Sporadic episodes of basaltic volcanism occurred during this phase from northern Ellesmere Island in the east to central Ellef Ringnes Island in the west, and diabase sills were intruded into the Sverdrup Basin succession over most of the basin during this phase (Embry and Osadetz, 1988; Estrada, 2015; Estrada et al., 2016; Evenchick et al., 2015; Kingsbury et al., 2016; Saumur et al., 2016) (Fig. 27). This volcanism is related to the occurrence of a mantle plume that lay to the north of the basin at this time (Embry and Osadetz, 1988; Buchan and Ernst, 2006). The plume was also responsible for the construction of a huge volcanic edifice, the 30 km thick Alpha-Mendeleev Ridge in the adjacent Amerasia Ocean Basin, and subsequent expressions of the plume may include the thick volcanic edifices of Baffin Bay and Iceland (Forsyth et al., 1986a; Lawver and Mueller, 1994).

FIG. 23  Cretaceous-Paleogene stratigraphic chart. First-order sequences correspond with the tectonic phases of the basin.



Sverdrup Basin Chapter | 14  581

FIG. 24  Stratigraphic cross-section of the Hauterivian-Barremian second-order sequence, which is the first second-order sequence of Phase 6. Note that parts of, or all of, four third-order sequences comprise the sandstone-dominant Isachsen Fm.

Phase 6 was terminated by widespread uplift in latest Albian, which subjected the basin margins to significant erosion. Dewing et al. (2016b) have demonstrated that the Drake Point anticline on the SW basin was initially formed during this tectonic episode. Notably this structure contains the largest gas field in the Canadian Arctic.

Phase 7: Quiescence (Late Cretaceous) Phase 7 began with renewed subsidence and transgression in earliest Cenomanian (base Late Cretaceous) and ended with major uplift of much of the basin in late Maastrichtian. The first-order sequence that encompasses these strata includes the entire Late Cretaceous succession and contains three second-order sequences (Fig. 23). The first second-order sequence is Cenomanian in age and consists mainly of shallow marine to delta plain deposits (upper Hassel Fm, Bastion Ridge Fm) (Fig. 25). Notably, thick basaltic volcanic flows (Strand Fiord Fm) of Cenomanian age (Tarduno et al., 1998; Dostal and MacRae, 2018) were extruded in the basin center and were associated with diabase intrusions (Kingsbury et al., 2018) (Fig. 25) and this volcanic unit thickens northward reaching a maximum thickness of 900 m on northern Axel Heiberg Island (Ricketts et al., 1985). Basaltic flows of this age have also been recognized on northern Ellesmere Island (Osadetz and Moore, 1988; Estrada, 2015). The location and thickness trends of these basalts indicate they were derived from the Alpha-Mendeleev mantle plume to the north (Embry and Osadetz, 1988). A major transgression occurred in latest Cenomanian and initiated the next second-order sequence of Turonian-Santonian age. The shorelines were pushed back far beyond the margins of the Sverdrup Basin and the basin underwent slow, passive subsidence during Turonian and Santonian. The basin received mud and silt that contained considerable volcanic ash and bituminous material (Kanguk Fm) (Nunez-Betelu et al., 1995; Hills and Strong, 2007; Pugh et al., 2014; Schroder-Adams et al., 2014; Davis et al., 2017; Davies et al., 2018). An episode of margin uplift and notable regression occurred in earliest Campanian and the following transgression in early Campanian initiated the third and final second-order sequence. The sediment input rate increased in the latter part of the Campanian and shoreline to shallow marine sandstones prograded into the basin (Expedition Fm) (Fig. 23). During this time, up to 500 m of felsic volcanics (rhyodacites, trachyandesites, and rhyolites) (Hansen Point Fm) were extruded on northernmost Ellesmere Island and the volcanics rest on strata as old as Carboniferous (Trettin and Parrish, 1987; Falcon-Lang et al., 2004; Estrada et al., 2016). These volcanics are thought to

582  The Sedimentary Basins of the United States and Canada

FIG. 25  (A) Stratigraphic cross-section of the Aptian-Albian second-order sequence, which is the upper second-order sequence of Phase 6. The sequence is overlain by the Cenomanian second-order sequence, which is the first of three second-order sequences of Phase 7. (B) Outcrop of Aptian-Cenomanian strata in the Strand Fiord area of Axel Heiberg Island (equivalent to westernmost section on cross-section). C-IP Invincible Point Mbr, Christopher Fm, C-MP McDougall Point Mbr, Christopher Fm, H Hassel Fm, BR Bastion Ridge Fm, SF Strand Fiord Fm.

Sverdrup Basin Chapter | 14  583



FIG. 26  Late Albian paleogeography with a sandy deltaic plain occupying the central portion of the basin. Alpha Ridge was fed by a mantle plume and the crest of the ridge was likely subaerially exposed.

Alpha ridge s, Volcanis flow lls si dykes and

Dy

ke s an

d

e

er

sil

ls

sm

le El

Greenland

FIG. 27  Distribution of Cretaceous extrusive and intrusive rocks that represent the on-land termination of Alpha Ridge, a hotspot track that crosses the Amerasian Basin.

be related to volcanism related to the initial rifting of the Eurasian portion of the Arctic Ocean (Estrada and Henjes, 2004; Tegner et al., 2011). The maximum thickness of the Late Cretaceous succession is about 800 m. Widespread uplift in late Maastrichtian, reflecting the initial compressional tectonics of the Eurekan Orogeny, marked the termination of this phase (Fig. 28).

Phase 8: Fragmentation and Uplift (Paleocene-Eocene) Once again, the tectonic regime of the Sverdrup Basin underwent a drastic change in latest Cretaceous/early Paleocene. Following widespread uplift, the basin was transgressed in Paleocene and parts of the eastern portion of the basin ­underwent

584  The Sedimentary Basins of the United States and Canada

FIG. 28  Outcrop of the Expedition Fm (E), the basal strata of Phase 8, unconformably overlying the Kanguk Fm (K) of Phase 7. The unconformity is a first-order sequence boundary. Central Ellesmere Island.

rapid subsidence related to compressional loading driven by the opening of the Labrador Sea and Baffin Bay and the consequent impingement of Greenland on the Arctic Islands area in early Tertiary (Eurekan Orogeny) (Ricketts and Stephenson, 1994; Tessensohn and Piepjohn, 2000). Other parts of the basin such as the Princess Margaret Arch and Cornwall Arch underwent uplift (Ricketts, 1987; Stephenson et al., 1990), and the adjacent subsiding areas received a high supply of siliciclastic sediment (Ricketts, 1994; Ricketts and Stephenson, 1994). The lithostratigraphy, sequence stratigraphy, and paleogeographic evolution of Sverdrup Basin in Paleocene-midEocene are discussed in detail in Miall (1991), Ricketts (1994), and Ricketts and Stephenson (1994). In summary, the succession in the foreland basins consists of a basal transgressive sandstone unit (upper Expedition Fm) (Fig. 28) followed by regressive, marine shale, and siltstone (Strand Bay Fm) and thick, sand-dominated, coastal to fluvial deposits with abundant coal (Iceberg Bay Fm) (3000 m) (Fig. 23). Deformation and uplift progressed through the Paleocene and Eocene (Arne et al., 2002), and syn-tectonic conglomerates (Buchanan Lake Fm) up to 1000 m thick were deposited in front of the advancing thrust sheets in mid-Eocene. These strata contain the remarkable fossil forest (Greenwood and Basinger, 1994). The deformation climaxed in late Eocene (Eurekan Orogeny) and the entire basin was uplifted, bringing to a close a 300-million-year history of deposition. The eastern part of the basin was substantially deformed by thrusting and folding and deformation gradually decreased in a southwestward direction (Piepjohn et al., 2016) (Fig. 2). The western portion of the basin is slightly deformed by broad folds and throughout the basin the salt structures exhibited large vertical growth during this compressive interval (Stephenson et al., 1992; Harrison and Jackson, 2014; Dewing et al., 2016a). The Sverdrup Basin area has remained under compression and has acted as a major source area for the adjacent Amerasia Basin.

TECTONIC EPISODES The Sverdrup Basin originated due to an episode of extensional tectonics that affected much of the Caledonian/Ellesmerian Orogenic Belt in Early Carboniferous. The basin was uplifted and deformed in late Eocene due to compression associated with the opening of the Labrador Sea. Between the time of its formation and its demise, the Sverdrup Basin was affected by a number of notable tectonic episodes, each of which is now expressed by the occurrence of a widespread unconformity on the basin margins and significant shoreline regression. The characteristics of these unconformities leave no doubt as to their tectonic origin (Embry, 1990, 1993b, 1997; Beauchamp et al., 2001; Embry et al., in press). The uplift phase of each tectonic episode was followed by a phase of rapid tectonic subsidence, which resulted in pronounced transgression and the drowning of the basin margins. The time interval between the start of tectonic uplift and the end of fast subsidence and major transgression encompasses a tectonic episode (Embry, 1993b). Biostratigraphic and thickness data indicate that the tectonic episodes were of relatively short duration compared with the intervening times of relative tectonic quiescence, which were characterized by slow subsidence (Embry, 1993b). Embry et al. (in press) estimated that a tectonic episode lasted 1–2 m.y. The largest magnitude unconformities allow the succession to be subdivided into eight first-order sequences and each represents a distinctive tectonic and depositional phase of basin development as described in the previous sections (Beauchamp et al., 2001; Embry, 1991a, Embry, 1993a, b, Embry, 1997, Embry, 2011). The first-order sequences contain



Sverdrup Basin Chapter | 14  585

smaller magnitude (second-order) sequence boundaries that represent lesser magnitude tectonic episodes. The first-order sequence boundaries closely match those recognized in various areas of the North American craton and the origin of these is interpreted to be due to various plate tectonic processes that affected the continent (Sloss, 1988; Chapter 2). It seems reasonable to assume that the smaller magnitude unconformities were also generated by crustal movements driven by plate tectonic interactions. As discussed in Embry et al. (in press), the Sverdrup Basin was affected, on average, by a relatively short-lived, tectonic episode once every 10 million years and that the magnitude of such an episode varied from quite large (widespread uplift and large changes in tectonic and depositional regimes) to moderate (marginal uplift and a change in depositional regime). They suggested that these chaotic tectonic episodes were the result of short-lived changes in horizontal stress fields affecting the basin, which in turn were driven by episodic, plate tectonic reorganizations. The major transgression associated with each tectonic episode was termed a “ten-million-year flood.”

ECONOMIC GEOLOGY Petroleum Exploration for petroleum in the Sverdrup Basin began in 1968 soon after the formation of Panarctic Oils Limited, a consortium of numerous oil companies and the federal government. A string of major gas fields was discovered between northeastern Melville Island and western Ellef Ringnes Island from 1969 to 1980 (Fig. 29). In 1981 a major oil field, Cisco, was discovered west of Lougheed Island but following discoveries were disappointing in their small quantities of contained oil. Chen et al. (2000) estimated the discovered reserves to be 500 109 m3 (17.7 TCF) of gas and 294 106 m3 of oil (1.8 BBL). The last well was drilled in 1986 and exploration in the Sverdrup Basin ceased with the collapse of the oil price that year. The very high costs of exploration in this remote frontier area, projected moderate petroleum prices, and major environmental concerns all make it very unlikely any petroleum exploration will happen in the foreseeable future. Strata that are sufficiently porous and permeable to act as reservoir rocks are very common in the Sverdrup Basin. In the Late Paleozoic succession, potential reservoir units include the Nansen, Canyon Fiord, and Sabine Bay formations. The main potential Mesozoic reservoir units are found in the Bjorne, Roche Point, Pat Bay, Heiberg, MacLean Strait, King Christian, Hiccles Cove, Awingak, Isachsen, and Hassel formations (Embry, 2011). The Bjorne sandstones are host to the oil sands of Melville Island (Trettin and Hills, 1966) and numerous oil and gas shows have been encountered in these sandstones. Most of the gas discovered so far occurs in the MacLean Strait and King Christian formations (Embry et al., 1991). These sandstones are of shallow marine origin and have very good to excellent porosity and permeability, especially along the southwestern basin margin (Waylett, 1989). Sandstones of the Remus Member of the Heiberg Fm are also very good reservoirs and contain gas at a few localities. In the basin center area the sandstones of the Heiberg Fm have greatly

FIG. 29  Hydrocarbon fields, western Sverdrup Basin. (From Embry et al. (1991).)

586  The Sedimentary Basins of the United States and Canada

reduced porosity due to cementation. Large quantities of oil and gas are also in shallow marine sandstones of the Awingak Fm. These reservoir units can have porosities up to 15%. The fluvial sandstones of the Isachsen contain small amounts of hydrocarbons. The sandstones of the Isachsen Fm are very porous and permeable over most of the basin but subsurface occurrences are often in communication with nearby outcrops. Four major petroleum source rock intervals have been identified in the Sverdrup Basin: the Early Carboniferous Emma Fiord Fm, the Middle Triassic Murray Harbour Fm, the Late Triassic Hoyle Bay Fm, and the Late Cretaceous Kanguk Fm (Powell, 1978; Embry et al., 1991). Others may well exist. Notably all the discovered oils appear to have been sourced from the Middle and Late Triassic source strata (Brooks et al., 1992). The Triassic shales contain up to 10% TOC and the organic matter is type II and predominantly of algal origin (Kondla et al., 2015). These source rocks are mature over much of the western Sverdrup Basin and on the flanks of the basin on the southeast, eastern, and northern flanks of the basin (Fig. 30) (Dewing and Obermajer, 2011). In the basin center, the Murray Harbour bituminous shales are overmature due to deep burial and the presence of numerous diabase sills (Embry et al., 1991; Jones et al., 2007; Dewing and Obermajer, 2011). The main play in the Sverdrup Basin occurs in Tertiary structures and all the hydrocarbon pools so far discovered occur in such traps (Meneley, 1986; Embry et al., 1991; Chen et al., 2000). The higher amplitude structures are associated with fracturing and loss of hydrocarbons but the fields on low amplitude anticlines have effective seals (Waylett and Embry, 1992). The major facies changes that occur within the Late Paleozoic succession, including the occurrence of large reefs, suggest that traps with a stratigraphic component may well exist in these strata (Beauchamp, 1993). The Mesozoic sandstones might also be involved in stratigraphic/structural traps on the flanks of salt structures. Numerous major unconformities occur within the Mesozoic succession and truncation and onlap-related traps as well as incised valley deposits may well be present (Embry, 2011). The paucity of oil fields in the Eurekan structures of Sverdrup Basin may be due to flushing of the structures by large quantities of gas released from overmature Triassic and older shale units in the basin center by way of extensive fracturing during the Eurekan Orogeny. The gas would have migrated southwestward into growing structures and displaced oil that had been trapped earlier when the source beds were in the oil window. Notably, the only major oil field found so far in a Tertiary structure occurs at the basinward pinch-out edge of the Awingak sandstone (Cisco), a location that may well have escaped the gas flush. Unconventional oil in the form of liquids associated with shale gas may well occur in the thick Middle-Late Triassic bituminous shales (Murray Harbour, Hoyle Bay fms) in the western Sverdrup (Kondla et al., 2016). Early Carboniferous bituminous shales (Emma Fiord Fm) along the southern basin margin also have potential for liquids. The Triassic shales have potential for large shale gas reserves given their extent, thickness, maturity, and organic carbon content. Finally, very large reserves of gas hydrates are also present in Sverdrup Basin (Majorowicz and Osadetz, 2001).

FIG. 30  Maturity map for the Middle-Late Triassic shales (Murray Harbour and Hoyle Bay fms), which are the main source strata for the discovered hydrocarbons.



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Coal Ricketts and Embry (1984) and Bustin and Miall (1991) summarized the coal resources of the basin. Thin seams less than a meter thick occur in Permian, Triassic, and Jurassic units. More numerous and thicker beds of coal up to 2 m thick are present in the Early Cretaceous Isachsen Fm. These coals are up to bituminous in rank. The thickest coals are found in the Paleogene-Eocene Iceberg Bay Fm and seams up to 15 m have been recorded. The Paleogene coal seams range in rank from lignite to bituminous.

SUMMARY The Sverdrup Basin is a major rift basin that developed on the Ellesmerian Orogenic Belt in Early Carboniferous. The basin went through eight phases of development. Each phase is characterized by a distinctive tectonic and depositional setting and was initiated by a tectonic episode characterized by widespread marginal uplift and subsequent collapse and transgression. A notable change in climate often accompanied these tectonic changes that may have been a response to plate tectonic reorganizations. During the first two phases, which occurred during the Carboniferous and Early Permian, carbonate sediments were deposited in a hot climate. Thick salt deposits filled the basin early in the development of the basin and huge reefs grew on the shelf margins at various times. The climate became much cooler in phase 3 (Middle to Late Permian) and spiculitic cherts were deposited on the shelf and in the basin. A new world dawned on the basin with the initiation of the Mesozoic Era and phase 4. The climate became very warm and siliciclastic sediments poured into the basin from the cratonic areas to the east and north and a land area to the north. During the Triassic the deep central basin was gradually filled and shallow-water sediments reached the basin center by Late Triassic when the northern landmass was the main source region. Phase 5 began with high siliciclastic influx in latest Triassic and Early Jurassic in a warm, humid climate. Siliciclastic influx waned for much of the remaining portion of this phase, which extended to earliest Cretaceous. This phase of basin development coincides with the rifting phase of the adjacent Amerasia Basin. Normal faulting related to Amerasian extension affected the area to the south of Sverdrup Basin but did not occur within the basin. The basin was rejuvenated in Early Cretaceous (phase 6) by an extensional episode that coincided with the initiation of sea floor spreading in the adjacent Amerasia Basin. Sediment influx was high and basalts were erupted in the northeast and basin center with accompanying widespread diabase dyke and sill intrusion. These igneous rocks represent the terrestrial termination of Alpha-Mendeleev Ridge, a hotspot track in the Amerasia Basin. Subsidence and sediment supply significantly decreased in early Late Cretaceous and bituminous shale was the main deposit of the basin in the early portion of phase 7. Siliciclastic supply increased during the late Late Cretaceous and alkalic volcanism occurred in the far northeastern portion of the basin. The basin began to be compressed in the Paleogene due to the opening of the Labrador Sea and the consequent counterclockwise rotation of Greenland. Thick, mainly continental siliciclastics were deposited in local foreland basins (phase 8) and the entire Sverdrup Basin was uplifted and deformed in late Eocene. Large gas fields have been discovered in the western Sverdrup within latest Triassic to Early Jurassic sandstones in Paleogene anticlines. The basin is interpreted to have major potential for unconventional gas resources. Coal is common in various nonmarine units from Permian onward, with the thickest seams occurring in the Paleogene strata.

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Gates, L., James, N.P., and Beauchamp, B., 2004, A glass ramp: Shallow-water Permian spiculitic chert sedimentation, Sverdrup Basin, Arctic Canada: Sedimentary Geology, v. 168, p. 125–147. Grantz, A., Hart, P.E., and Childers, V.A., 2011, Geology and tectonic development of the Amerasia and Canada Basins, Arctic Ocean, in Spencer, A.M., Embry,  A.F., Gautier,  D.L., Stoupakova,  A.V., and Sørensen,  K., eds., Arctic Petroleum Geology: Geological Society London Memoir 35, p. 771–799. Greenwood, D.R., and Basinger, J.F., 1994, The paleoecology of high latitude Eocene swamp forests from Axel Heiberg Island, Canadian High Arctic: Review of Palaeobotany and Palynology, v. 81, p. 83–97. Hadlari, T., Midwinter, D., Galloway, J., and Dewing, K., 2016, Mesozoic rift to post-rift tectonostratigraphy of the Sverdrup Basin, Canadian Arctic: Marine and Petroleum Geology, v. 76, p. 148–158. 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Hills, L.V., and Strong, W.L., 2007, Multivariate analysis of Late Cretaceous Kanguk Formation (Arctic Canada) palynomorph assemblages to identify nearshore to distal marine groupings: Bulletin of Canadian Petroleum Geology, v. 55, p. 160–172. Jackson, M.P.A., and Harrison, J.C., 2006, An allochthonous salt canopy on Axel Heiberg Island, Sverdrup Basin, Arctic Canada: Geology, v.  34, p. 1045–1048. James, N.P., 1997, The cool-water carbonate depositional realm, in James,  N.P., and Clarke,  J.A.D., eds., Cool-Water Carbonates: SEPM Special Publication 56, p. 1–22. Jones, S.F., Wielens, H., Williamson, M.C., and Zentilli, M., 2007, Impact of magmatism on petroleum systems in the Sverdrup basin, Canadian Arctic islands, Nunavut: A numerical modelling study: Journal of Petroleum Geology, v. 30, p. 237–256. Kingsbury, C.G., Ernst, R.E., Cousens, B.L., and Williamson, M.-C., 2016, The High Arctic LIP in Canada: Trace element and Sm-Nd isotopic evidence for the role of mantle heterogeneity and crustal assimilation: Norwegian Journal of Geology, v. 96, p. 97–118. Kingsbury, C., Kamo, S., Ernst, R., Söderlund, U., and Cousens, B., 2018, U-Pb geochronology of the plumbing system associated with the Late Cretaceous Strand Fiord Formation, Axel Heiberg Island, Canada: Part of the 130-90 Ma High Arctic large igneous province: Journal of Geodynamics, v. 118, p. 106–117. Kondla, D., Sanei, H., Embry, A.F., Ardakani, O.H., and Clarkson, C.R., 2015, Depositional environment and hydrocarbon potential of the Middle Triassic strata of the Sverdrup Basin, Canada: International Journal of Coal Geology, v. 147–148, p. 71–84. Kondla, D., Sanei, H., Clarkson, C.R., Ardakani, O.H., Wang, X., and Jiang, C., 2016, Effects of organic and mineral matter on reservoir quality in a Middle Triassic mudstone in the Canadian Arctic: International Journal of Coal Geology, v. 153, p. 112–126. Lawver, L.A., and Mueller, R., 1994, Iceland hotspot track: Geology, v. 22, p. 311–314. Maher, H.D., 2001, Manifestations of Cretaceous High Arctic large igneous province in Svalbard: Journal of Geology, v. 109, p. 91–104. Majorowicz, J.A., and Osadetz, K., 2001, Gas hydrate distribution and volume in Canada: American Association of Petroleum Geologists Bulletin, v. 85, p. 1211–1230. Maurel, L.E., 1989, Geometry and evolution of the Tanquary Structural High and its effects on the paleogeography of the Sverdrup basin, northern Ellesmere Island, Canadian Arctic: Geological Survey of Canada Paper 89-1G, p. 177–189. Mayr, U., 1992, Reconnaissance and preliminary interpretation of Upper Devonian to Permian stratigraphy of northeastern Ellesmere Island, Canadian Arctic Archipelago: Geological Survey of Canada Paper 91-08, 117 pp. Meneley, R.A., 1986, Oil and gas fields in the East Coast and Arctic Basins of Canada, in Halbouty, M.T., ed., Future Petroleum Provinces of the World: American Association of Petroleum Geologists Memoir 40, p. 143–176. Meneley, R.A., Henao, D., and Merritt, R.K., 1975, The northwest margin of the Sverdrup Basin, in Yorath, C., Parker, R., and Glass, D., eds., Canada’s Continental Margins and Offshore Petroleum Exploration: Canadian Society of Petroleum Geologists Memoir 4, p. 531–544. Miall, A.D., 1991, Late Cretaceous–Early Tertiary basin development and sedimentation, Arctic Islands, in Trettin, H.P., ed., Innuitian Orogen and Arctic Platform: Canada and Greenland: Geological Survey of Canada, Geology of Canada, no. 3, p. 437–458. 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Sverdrup Basin Chapter | 14  591

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Stephenson, R.A., BoerstoeL, J., Embry, A.F., and Ricketts, B., 1994, Subsidence analysis and tectonic modeling of the Sverdrup Basin, in Thurston, D., and Fujita, K., eds., 1992 Proceedings International Conference on Arctic Margins: Minerals Management Service, U.S. Department of the Interior, Washington, DC, p. 149–154. Tarduno, J.A., Brinkman, D.B., Renne, P.R., Cottrell, R.D., Scher, H., and Castillo, P., 1998, Evidence for extreme climatic warmth from late Cretaceous Arctic vertebrates: Science, v. 282, p. 2241–2244. Tegner, C., Storey, M., Holm, P., Thorarinsson, S., Zhao, X., Lo, C., and Knudsen, M., 2011, Magmatism and Eurekan deformation in the High Arctic Large Igneous Province: 40Ar-39Ar age of Kap Washington Group volcanics, North Greenland: Earth and Planetary Science Letters, v. 303, p. 203–214. Tessensohn, F., and Piepjohn, K., 2000, Eocene compressive deformation in Arctic Canada, north Greenland and Svalbard and its plate tectonic causes: Polarforschung, v. 68, p. 121–124. Thériault, P., 1991. Synrift sedimentation in the Upper Carboniferous Canyon Fiord Formation, SW Ellesmere Island, Canadian Arctic [M.Sc. thesis]: University of Ottawa, 210 pp. Thériault, P., Beauchamp, B., and Steel, R., 1993, Syntectonic deposition of the Carboniferous Borup Fiord Formation, Northwestern Ellesmere Island: Geological Survey of Canada Paper 93-1E, p. 105–112. Thorsteinsson, R., 1974, Carboniferous and Permian stratigraphy of Axel Heiberg Island and western Ellesmere Island, Canadian Arctic Archipelago: Geological Survey of Canada Bulletin 224, 115 pp. Trettin, H.P., 1988, Early Namurian (or older) alkali basalt in the Borup Fiord Formation, northern Axel Heiberg Island, Arctic Canada: Geological Survey of Canada Paper 88-ID, p. 21–26. 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