A thick succession of upper Paleozoic carbonate rocks and minor chert crops out north of the head of Otto Fiord (northwest [NW] Ellesmere Island, Nunavut) in the Canadian Arctic Archipelago. These rocks accumulated in a tectonic subbasin—the Otto Fiord Depression (OFD)—of the Sverdrup Basin that likely originated through rifting during late Early Carboniferous (Serpukhovian). Following a long interval of passive subsidence that allowed a thick succession of Moscovian–Kasimovian carbonate rocks to fill the OFD, tectonic activity resumed during the Gzhelian (Late Pennsylvanian). This resulted in rapid collapse of the depression along its axis and simultaneous uplifts of its margins, a style of tectonism in accord with the inferred basin-wide shift to a transpressional–transtensional stress regime at that time. Late Pennsylvanian–Early Permian sedimentation in the OFD led to the development of four long-term (second-order) transgressive–regressive sequences of early Gzhelian–middle Asselian (<1200 m), late Asselian–late Sakmarian (<380 m), latest Sakmarian–late Artinskian (<160 m) and latest Artinskian–late Kungurian (<60 m) age. These ages are supported by integration of biostratigraphic data from conodonts, fusulinaceans, and small foraminifers. The development of each sequence-bounding unconformity was associated with renewed tectonism in the OFD. Each sequence recorded the development of a depositional system characterized by high energy peripheral shoreface grainstones passing basinward across a gently dipping ramp into deep-water basinal calcareous and siliceous mudstone. The ramp portion of the early Gzhelian–middle Asselian system comprises both cool-heterozoan to warmphotozoan carbonates (Nansen Formation) suggesting a relatively shallow thermocline at that time. These rocks are arranged in a series of high-order cyclothems of glacio-eustatic origin. Cyclothemic sedimentation ended at the Asselian–Sakmarian boundary, simultaneous to a major depositional system shift to cool-water heterozoan sedimentation (Raanes Formation), a change presumably brought on by the closure of the Uralian seaway linking NW Pangea with the Tethyan Ocean. This event led to the destruction of the permanent thermocline, and disappearance of photozoan carbonates by the early Sakmarian despite rising temperatures globally. Cool-water heterozoan sedimentation, associated with relatively shallow outer-ramp to midramp spiculitic chert resumed in the Artinskian and then again in the Kungurian (Great Bear Cape Formation) when the OFD was filled up. The depression ceased to exist as a separate tectonic/subsidence entity with the widespread sub-Middle Permian unconformity, above which sediments were deposited during a passive subsidence regime across most of the Sverdrup Basin. The Pennsylvanian–Lower Permian succession that accumulated in the OFD along the clastic-free northern margin of the Sverdrup Basin is essentially identical, both in terms of tectonic evolution and stratigraphic development, with the coeval succession of Raanes Peninsula, southwest (SW) Ellesmere Island, the type area of the Raanes, Trappers Cove, and Great Bear Cape formations along the clastic-influenced southern margin.

ABSTRACT The Tanquary High is a positive tectonic feature that was identified on the southern margin of the far northeastern portion of Sverdrup Basin. A sequence stratigraphic analysis of the Triassic succession of northern Ellesmere Island, involving 27 measured sections and one well section, has allowed the geometry and evolution of the high in the Triassic to be elucidated. The Triassic succession occurs within five second-order sequences, and each sequence boundary reflects the occurrence of a tectonic episode that included basin margin uplift and basinward movement of the shoreline. The Tanquary High was uplifted during these tectonic episodes, which occurred in the latest Permian, latest Early Triassic, latest Middle Triassic, latest Carnian, and latest Norian. Each sequence is truncated toward the crest of the high where Rhaetian strata now overlie Cambrian strata. Isopach and facies data for each sequence reveal that, at the times of maximum uplift of the Tanquary High, the subaerially exposed part of the high extended 100–150 km down its northwest-trending axis and up to 150–200 km down each flank. Rapid subsidence completed each tectonic episode and initiated the development of a new sequence. The Tanquary High was completely drowned at these times. It is hypothesized that the tectonic episodes were generated by changes in horizontal stress fields driven by plate tectonic reorganizations. The facies and isopach maps of the latest Triassic to early Early Jurassic (Rhaetian-Sinemurian) second-order sequence demonstrate that the Tanquary High ceased to exist following the first order, latest Norian sequence boundary. A complete reversal of source areas and the initiation of the Amerasia rift basin coincided with the demise of the Tanquary High.

ABSTRACT The unit previously mapped as the lower Upper Devonian Okse Bay Formation in the Yelverton Pass area of northern Ellesmere Island, considered indicative of syn-orogenic foreland (Devonian clastic wedge) basin deposition along the apex of the Ellesmerian Orogen, is in fact Early Carboniferous (Serpukhovian) in age and belongs to the Borup Fiord Formation of the successor Sverdrup Basin. The principal lines of evidence in favor of the original Okse Bay formational assignment were: (1) the presence of late Middle (Givetian) or early Late (Frasnian) Devonian palynomorphs; (2) a set of lithofacies presumably different from that of the Borup Fiord Formation; and (3) an angular unconformity between the so-called Okse Bay strata and overlying Pennsylvanian carbonates of the Nansen Formation. Here we demonstrate that the Devonian palynomorphs were eroded from the Devonian clastic wedge, transported for some distance, and deposited into the Sverdrup Basin in the Early Carboniferous. We also show that the units mapped as Okse Bay and Borup Fiord formations share the same clastic lithofacies assemblages, albeit in different proportions. We report the presence of Early Carboniferous palynomorphs in the uppermost part of a section assigned to the Okse Bay Formation, and show that detrital zircons contained in the middle part of the Okse Bay Formation yield dates as young as 358 Ma, thus demonstrating that the rocks that contain them are considerably younger than the assumed youngest age (Frasnian) based on palynology. We conclude that the Okse Bay Formation is the same unit as the Borup Fiord Formation and should be remapped as such. Both units are part of the same unconformity-bounded syn-rift Serpukhovian sequence that was rotated and differentially eroded prior to the widespread Pennsylvanian transgression. The Serpukhovian sequence comprises three lithofacies assemblages: meandering stream clastic, braided stream/alluvial fan clastic, and shallow marine carbonate. These lithofacies assemblages were deposited as part of a differentially subsiding rift system likely bounded to the south by one or more master listric faults and associated footwall uplift, and to the north by hanging wall ramp uplift. The Serpukhovian sequence comprises three fourth-order sequences, each interpreted as corresponding to a rift pulse. Relatively coarse terrigenous sediments derived from the erosion of the Franklinian basement (Laurentia margin) and the Devonian clastic wedge entered the rift basin at a high angle through broad alluvial fans and braided river systems. These streams fed into a NE-flowing basin-axial meandering system, which met a shallow sea to the northeast. An additional source of sediments is Crockerland to the north, including syn- to post-Ellesmerian intrusions that shed detrital zircons of latest Devonian age once sufficient unroofing of these had occurred during the Serpukhovian.

Abstract New deep seismological data from Ellesmere Island and the adjacent Arctic continental margin provide new information about the crustal structure of the region. These data were not available for previous regional crustal models. This paper combines and redisplays previously published results – a gravity-derived Moho map and seismological results –to produce new maps of the Moho depth, the depth to basement and the crystalline crustal thickness of Ellesmere Island and contiguous parts of the Arctic Ocean, Greenland and Axel Heiberg Island. Northern Ellesmere Island is underlain by a thick crustal block (Moho at 41 km, c. 35 km crust). This block is separated from the Canada–Greenland craton in the south by a WSW–ENE-trending channel of thinned crystalline crust (Moho at 30–35 km, <20 km thick crust), which is overlain by a thick succession of metasedimentary and younger sedimentary rocks (15–20 km). The Sverdrup Basin in the west and the Lincoln Sea in the east interrupt the crustal architecture of central Ellesmere Island, which is interpreted to be more representative of its initial post-Ellesmerian Orogen structure, but with a later Sverdrup Basin and Eurekan overprint.

Abstract The 400 km long transect through Ellesmere Island is located perpendicular to the North American continental margin between the Arctic Ocean in the NNW and the Greenland–Canadian Shield in the SSE. It provides an insight into the structural architecture and tectonic history of the upper parts of the continental crust. The northernmost segment of the transect is dominated by the composite Pearya Terrane, which amalgamated with the Laurentian margin during the Late Devonian–Early Carboniferous Ellesmerian Orogeny. The Neoproterozoic to Devonian Franklinian Basin is exposed south of the terrane boundary and most probably overlies the crystalline basement of the Greenland–Canadian Shield. The structures along the transect in this area are dominated by kilometre-scale Ellesmerian folding of the Franklinian Basin deposits above a deep-seated detachment, which is suggested to be located at the boundary between the basement of the Canadian Shield and the overlying >8 km thick Franklinian Basin. Following the development of the Late Mississippian–Palaeogene Sverdrup Basin, the complex Eurekan deformation reactivated Ellesmerian thrust faults and probably parts of the associated deep-seated detachment. In addition, large Eurekan strike-slip faults affected and displaced pre-Eocene deposits and tectonic structures, particularly in the northern part of the transect. Supplementary material: The complete transect (Segment 1 to 5) through Ellesmere Island between the Arctic Ocean in the NNW and Kane Basin in the SSE is available at https://doi.org/10.6084/m9.figshare.c.3783608