Geology, tectonic assemblage map of Alexandra Fiord, central Ellesmere and eastern Axel Heiberg islands, Nunavut

Harrison, J C; Gilbert, Caroline; Lynds, T; Ford, A; Thorsteinsson, R; Frisch, Thomas; Freitas, T. A. de; Kerr, J W

doi:10.4095/292827

Cited by 3 publications

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“…The “warm” sites are located on Cape Herschel ( Fig 2C ), a cape comprised of Paleoproterozoic orthopyroxine granite with localized metasedimentary units [ 29 , 30 ] [ 30 ] and with patchily distributed outcrops of calcareous glacial till [ 29 ]. Our research team has regularly visited and sampled the ponds on Cape Herschel, approximately every three years, for about the past 30 years.…”

Section: Site Descriptionmentioning

confidence: 99%

“…Pim Island is a steep-sided island located ~10 km to the north of Cape Herschel and composed of Paleoproterozoic orthopyroxine granite with metasedimentary enclaves [ 30 ], with occurrences of discontinuous calcareous till [ 32 ]. The exposed, high elevation ponds on the island had no appreciable accumulation of sediment for coring, and therefore we focused on obtaining sediment cores from deeper lakes.…”

Section: Site Descriptionmentioning

confidence: 99%

“…The growing season here spans from late May to early September [ 34 ], and the warmer conditions have resulted in greater vegetation growth as compared to polar desert sites, with enough wet sedge meadow habitat to support a small muskox population [ 35 ]. The pass is an ice-free, U-shaped valley bordered by high cliffs of Cambrian and Lower Ordovician carbonates [ 36 ] and the study ponds are located within a variably argillaceous and arenaceous Cambrian limestone-dolostone [ 30 ]. The protection from wind by the cliffs (e.g.…”

Section: Site Descriptionmentioning

confidence: 99%

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Ice-cover is the principal driver of ecological change in High Arctic lakes and ponds

et al. 2017

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Recent climate change has been especially pronounced in the High Arctic, however, the responses of aquatic biota, such as diatoms, can be modified by site-specific environmental characteristics. To assess if climate-mediated ice cover changes affect the diatom response to climate, we used paleolimnological techniques to examine shifts in diatom assemblages from ten High Arctic lakes and ponds from Ellesmere Island and nearby Pim Island (Nunavut, Canada). The sites were divided a priori into four groups (“warm”, “cool”, “cold”, and “oasis”) based on local elevation and microclimatic differences that result in differing lengths of the ice-free season, as well as about three decades of personal observations. We characterized the species changes as a shift from Condition 1 (i.e. a generally low diversity, predominantly epipelic and epilithic diatom assemblage) to Condition 2 (i.e. a typically more diverse and ecologically complex assemblage with an increasing proportion of epiphytic species). This shift from Condition 1 to Condition 2 was a consistent pattern recorded across the sites that experienced a change in ice cover with warming. The “warm” sites are amongst the first to lose their ice covers in summer and recorded the earliest and highest magnitude changes. The “cool” sites also exhibited a shift from Condition 1 to Condition 2, but, as predicted, the timing of the response lagged the “warm” sites. Meanwhile some of the “cold” sites, which until recently still retained an ice raft in summer, only exhibited this shift in the upper-most sediments. The warmer “oasis” ponds likely supported aquatic vegetation throughout their records. Consequently, the diatoms of the “oasis” sites were characterized as high-diversity, Condition 2 assemblages throughout the record. Our results support the hypothesis that the length of the ice-free season is the principal driver of diatom assemblage responses to climate in the High Arctic, largely driven by the establishment of new aquatic habitats, resulting in increased diversity and the emergence of novel growth forms and epiphytic species.

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Section: Site Descriptionmentioning

confidence: 99%

Section: Site Descriptionmentioning

confidence: 99%

Section: Site Descriptionmentioning

confidence: 99%

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Ice-cover is the principal driver of ecological change in High Arctic lakes and ponds

et al. 2017

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“…Jurassic and earliest Cretaceous deposits are lacking in the study area (Harrison et al., 2015; Thorsteinsson et al., 2009), and this time is generally described as a period of quiescence (Embry & Beauchamp, 2008). We thus assume non‐deposition or minor erosion, and that the cratonic rocks resided in relatively shallow crustal levels.…”

Section: Thermal History Modelingmentioning

confidence: 99%

Phanerozoic Tectonic and Sedimentation History of the Arctic: Constraints From Deep‐Time Low‐Temperature Thermochronology Data of Ellesmere Island and Northwest Greenland

et al. 2023

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Southeast Ellesmere Island was the site of two major deformation events that affected the Arctic during the Phanerozoic; the Late Devonian to Early Carboniferous Ellesmerian Orogeny and the Palaeogene Eurekan Orogeny (e.g., Trettin, 1991). Both deformation belts run parallel or sit on top of each other and stretch for >2,500 km across the Canadian High Arctic, North Greenland, and Svalbard (Figure 1a). The deformation fronts of both orogens cross our study area (Figure 1b). Particularly for the Ellesmerian Orogeny, timing and rates are still poorly constrained (e.g., Beauchamp et al., 2019;McClelland et al., 2023;Piepjohn et al., 2007). In Ellesmere Island, this orogeny affected sediments of the Neoproterozoic to early Palaeozoic Franklinian Basin (Figure 1b). After Ellesmerian deformation ceased, the Sverdrup Basin developed within the area of the former Ellesmerian Orogen. The Sverdrup Basin remained an active depocenter until the Eurekan Orogeny (Embry &

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LOWER CAMBRIANRUSOPHYCUSFROM ELLESMERE ISLAND, ARCTIC CANADA: ICHNOFOSSIL OF A PREDATORY, NON-TRILOBITE ARTHROPOD

Pratt

2022

Palaios

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Cruziana and Rusophycus are commonly assumed to be trilobite trace fossils, although associated exoskeletons are almost invariably absent from host strata. In the lower Cambrian Dallas Bugt Formation of Ellesmere Island, Arctic Canada, high-energy, cross-laminated sandstones locally with dense populations of large Skolithos are overlain by thin-bedded, bioturbated, argillaceous, medium-grained glauconitic sandstones of lagoonal aspect, yielding Rusophycus along with an assortment of other “worm” burrows. Some specimens of Rusophycus are located over small Skolithos shafts and the bottoms of Arenicolites, suggesting a predator-prey relationship. Many preserve the impression of a strongly vaulted carapace with a broad, triangular dorsal outline between 1 cm and 7 cm across. A blunt anterior “prow” projects slightly forward and arches dorsally, forming a keyhole-shaped notch. The arthropod dug into the sediment up to 5 cm deep with an antero-posterior angle of up to ∼ 45° from the sea floor; in some cases it dug obliquely laterally and rarely sideways. Retroverse scratches—preserved in hyporelief as sharp-crested ridges—suggest about 20 pairs of endopodites tipped by a pair of small claws typically dug in unison, the anterior ones starting with a V-angle of 140° and decreasing posteriorly to 90°, in rare cases more tightly. Limb length increased posteriorly, although none extended beyond the carapace. Leg muscles were strong enough to rake through the muddy sand and pull inwards either straight or in a slightly forward-curving arc, but were also slightly flexible to wiggle around obstacles. Some specimens show subsequent re-burrowing which produced cross-cutting and opposed scratches. No evidence for exopodite brushings is present. Successive carapace imprints and scratches organized in transverse rugae in some specimens suggest repeatedly plunging and digging as the arthropod pulled backward in the sediment. This was likely aided by a stout trunk and a fan-shaped uropod-like structure flanking the telson which increased grip and leverage. A pair of eye stalks may have projected from the anterior notch, and these could have been retracted during digging, but there is no evidence for antennae. The tracemaker was not a trilobite but an unrelated crustacean-like arthropod, although there is no known late early Cambrian body fossil to which it can be ascribed. The specimens are classified as Rusophycus jenningsi (Fenton and Fenton, 1937) and a neotype is selected for this ichnospecies from the Gog Group near where it was first collected. Its range extends from the southern Canadian Rocky Mountains north along depositional strike to Victoria Island and northwest to Ellesmere Island and northern Greenland. Two new ichnofamilies are established: Rusophycidae and Cruzianidae.

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Geology, tectonic assemblage map of Alexandra Fiord, central Ellesmere and eastern Axel Heiberg islands, Nunavut

Cited by 3 publications

References 0 publications

Ice-cover is the principal driver of ecological change in High Arctic lakes and ponds

Ice-cover is the principal driver of ecological change in High Arctic lakes and ponds

Phanerozoic Tectonic and Sedimentation History of the Arctic: Constraints From Deep‐Time Low‐Temperature Thermochronology Data of Ellesmere Island and Northwest Greenland

LOWER CAMBRIANRUSOPHYCUSFROM ELLESMERE ISLAND, ARCTIC CANADA: ICHNOFOSSIL OF A PREDATORY, NON-TRILOBITE ARTHROPOD

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