Atrypoidea zonation of the Upper Silurian Read Bay Formation of Somerset and Cornwallis Islands, Arctic Canada

1979 ◽  
Vol 16 (12) ◽  
pp. 2204-2218 ◽  
Author(s):  
Brian Jones
Keyword(s):  
Carbonate Rocks ◽  
Basal Part ◽  
Arctic Canada ◽  
Pressure Point ◽  
Species Overlap ◽  
Conodont Zone ◽  
Upper Silurian ◽  
Somerset Island ◽  
Cornwallis Island ◽  
Distinct Distribution

Species of the brachiopod genus Atrypoidea have a distinct distribution in carbonate rocks of the late Silurian Read Bay Formation of Arctic Canada. Atrypoidea phoca occurs in the basal part of the formation and this species is succeeded by Atrypoidea foxi forma B at higher levels. The ranges of the two species overlap, defining a third useful zone. Locally, as in the Pressure Point area of northwestern Somerset Island, Atrypoidea foxi forma B is succeeded by Atrypoidea foxi forma A. Atrypoidea foxi forma A is generally restricted to carbonates with a low content of detrital material and has a significantly larger shell than Atrypoidea foxi forma B. A higher zone is defined by Atrypoidea erebus which occurs in the basal part of the Somerset Island Formation on Somerset Island and in the basal part of member C of the Read Bay Formation at Goodsir Creek on Cornwallis Island. At the latter locality, Atrypoidea foxi forma A is found with Atrypoidea erebus, thereby demonstrating their overlapping ranges.The overlapping ranges of Atrypoidea phoca and Atrypoidea foxi forma B occur in the middle to late Ludlovian ploeckensis–siluricus conodont zones. On Somerset Island, Atrypoidea foxi forma B and Atrypoidea foxi forma A range through the ploeckensis–siluricus conodont zone. Atrypoidea erebus occurs in late Ludlovian and (or) early Pridolian strata.

The Ordovician–Silurian boundary on Cornwallis and Truro islands, Arctic Canada: preliminary data

1991 ◽  
Vol 28 (11) ◽  
pp. 1854-1862 ◽  
Author(s):  
Michael J. Melchin ◽  
Alexander D. McCracken ◽  
Fred J. Oliff
Keyword(s):  
Sea Level ◽  
Arctic Canada ◽  
Faunal Turnover ◽  
Sea Level Fluctuations ◽  
Continuous Sequence ◽  
Cape Phillips Formation ◽  
Show Evidence ◽  
Conodont Zone ◽  
Continuous Sedimentation ◽  
Cornwallis Island

Four sections of the lower part of the Cape Phillips Formation, two outcrops on northeastern Cornwallis Island and one outcrop and one drill core from Truro Island, Northwest Territories, Canada, provide significant new data on the Ordovician–Silurian boundary. They show evidence of continuous sedimentation through the boundary interval and a continuous sequence of graptolite zones, including the bohemicus and persculptus zones, which have not been previously found in Arctic Canada. Strata yield graptolites, including uncompressed specimens, and conodonts through most of the sections. The ordovicicus conodont Zone occurs within the pacificus to lower persculptus graptolite zones. The nathani conodont Zone contains a "transitional fauna," a mixing of species typical of the preceeding ordovicicus Zone and those generally regarded as Silurian indicators. This conodont zone ranges from the middle of the persculptus graptolite Zone into the lower acuminatus graptolite Zone and, thus, spans the Ordovician–Silurian boundary. The Ordovician–Silurian faunal turnover of the conodonts, therefore, also spans the Ordovician–Silurian boundary and is not coincident with the interval of major graptolite extinction, which occurs earlier, at the end of the pacificus Zone. The base of the kentuckyensis conodont Zone occurs in the acuminatus graptolite Zone. Sedimentologic evidence of the maximum eustatic sea-level drop can be seen within the bohemicus Zone (early Hirnantian) and possibly one or several smaller scale sea-level fluctuations through the underlying zones.

Upper Silurian stromatoporoids from Somerset Island, Arctic Canada

1979 ◽  
Vol 16 (2) ◽  
pp. 364-372 ◽  
Author(s):  
James M. Savelle
Keyword(s):  
High Energy ◽  
Arctic Canada ◽  
Near Shore ◽  
Upper Silurian ◽  
Somerset Island

Plexodictyon katriense Nestor, P. heclae n. sp., Diplostroma sp., Actinostroma furyi n. sp., Actinodictyon netsiliki n. sp., and Vicinostachyodes sokolovi (Riabinin) occur in Upper Silurian (middle to late Ludlovian) strata near Creswell Bay, Somerset Island. Faunal and sedimentological evidence suggests the stromatoporoids inhabited predominantly shallow, high energy, near-shore environments.

The Somerset Island Formation: an upper Silurian to ?Lower Devonian intertidal/supratidal succession, Boothia Uplift region, Arctic Canada

1978 ◽  
Vol 15 (2) ◽  
pp. 181-189 ◽  
Author(s):  
A. D. Miall ◽  
J. Wm. Kerr ◽  
M. R. Gibling
Keyword(s):  
Lower Devonian ◽  
Alluvial Fan ◽  
Similar Sequence ◽  
Island Formation ◽  
Fine Grained ◽  
Rock Types ◽  
Sandstone Rock ◽  
Upper Silurian ◽  
Somerset Island ◽  
Cornwallis Island

The Somerset Island Formation of Somerset Island is a newly defined unit consisting of interbedded fine-grained, grey, planar-laminated dolomite and limestone, grey mottled limestone and dolomite, red quartzose siltstone and red dolosiltite. It forms a transitional unit between the limestone and dolomite of the underlying Read Bay Formation and the sandstone and conglomerate of the overlying Peel Sound Formation, and ranges in thickness from 150 to more than 400 m. The formation was formed predominantly in intertidal and supratidal environments and forms the lowest part of a regressive sequence that culminates in boulder conglomerates of alluvial fan origin in the Peel Sound Formation. The Somerset Island Formation is predominantly Pridolian in age, but may include some strata of Ludlovian and Gedinnian age.The regressive sequence reflects a major pulse of the Cornwallis Disturbance of Boothia Uplift. A similar sequence occurs in Prince of Wales Island, although the lower part of the succession there contains conglomerate and sandstone, rock types that are absent in Somerset Island. These rocks are formally assigned to the Lower Peel Sound Formation but are of similar age to the Somerset Island Formation of the type area.Rocks of similar facies to the Somerset Island Formation of Somerset Island comprise the upper member of the Drake Bay Formation on Russell Island and Member D of the Read Bay Formation on Cornwallis Island. The latter unit is younger than the Somerset Island Formation, reflecting a later commencement of regression in that area.

Microvertebrate assemblages from the Upper Silurian of Cornwallis Island, Arctic Canada

1999 ◽  
Vol 36 (3) ◽  
pp. 349-361 ◽  
Author(s):  
Carole J Burrow ◽  
Jo MJ Vergoossen ◽  
Susan Turner ◽  
Tom T Uyeno ◽  
Ray Thorsteinsson
Keyword(s):  
New Species ◽  
Arctic Canada ◽  
Growth Zones ◽  
Upper Silurian ◽  
The Baltic ◽  
Cornwallis Island

Microvertebrate assemblages from four Upper Silurian (?Ludlow-Pridoli) localities on Cornwallis Island, Arctic Canada, comprise mainly scales, plus dentition cones and jaw fragments from ischnacanthid acanthodians, with rare scales assigned to heterostracan Lepidaspis? sp., ?chondrichthyan Arauzia? sp., and Placodermi? gen. et sp. indet. Most of the scales in sample C-11460 are assigned to the poracanthodid acanthodian Poracanthodes canadensis sp.nov., which shows closest affinity to Poracanthodes punctatus Brotzen variants from the Baltic Pridoli. The flank scales of the new species resemble those of P. punctatus s.s. (Silurian variant; the zone fossil for the late Pridoli in the Standard Silurian microvertebrate scheme), with their superposed crown growth zones, rows of small pores aligned with the underlying zones, number of radial canals, and "arcade" canals connecting these radial canals. They differ in having numerous anterior crown riblets, "zig-zag" rather than straight crown pore rows, and V-shaped arcade canals.

Stratigraphic setting of the type specimen of Carpocrinus arcticus Frest and Strimple from the Late Silurian of Somerset Island, Arctic Canada

1977 ◽  
Vol 14 (9) ◽  
pp. 2168-2168 ◽  
Author(s):  
Guy M. Narbonne
Keyword(s):  
Type Specimen ◽  
Arctic Canada ◽  
Somerset Island ◽  
Upper Boundary

The type specimen of Carpocrinus arcticus Frest and Strimple was collected approximately 65 m below the upper boundary of the Read Bay Formation (Member A) at Fury Point, Somerset Island. Associated brachiopods, trilobites, and bryozoans suggest a Ludlovian age for this specimen.

Heliolitine corals of the topmost Douro and overlying formations (Upper Silurian), Canadian Arctic islands

1998 ◽  
Vol 72 (6) ◽  
pp. 937-966 ◽  
Author(s):  
Owen A. Dixon
Keyword(s):  
New Species ◽  
Canadian Arctic ◽  
Unidentified Species ◽  
Upper Silurian ◽  
Somerset Island

Heliolitine corals occur in Upper Silurian strata of the topmost Douro, lower Barlow Inlet, and lower Somerset Island formations in the Boothia Uplift region. The fauna includesHeliolites(nine species),Propora(two species), the stelliporellid generaPodollites(three species) andStelliporella(one species), and the plasmoporidSquameolites(one species). Species present but not previously reported from the region includeHeliolites arcuatusBondarenko,Heliolites uksunayensisMironova,Stelliporella ilensisBondarenko,Podollites assitusnew species,Podollites parryinew species,Podollites plectilisnew species,Propora tubulata(Lonsdale) and an unidentified species ofPropora.All species occur in reef and reef-associated facies of open carbonate shelf and ramp settings. In restricted nonreefal carbonate shelf settings, diversity attenuates to a minimum, exemplified by numerically abundant monospecific assemblages ofHeliolites uksunayensis.Six of the 16 morphotaxonomic units recognized compare with species reported previously in Silurian faunas of Kazakhstan and Mongolia. Combinations of characters in the species attributed toPodollitessupport revision of the genus, possibly to includeDerivatolitesandTarbagatailites, in a group morphologically intermediate betweenStelliporellaandHeliolites.

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