The Middle-upper Devonian clastic wedge of the Franklinian geosyncline

Bibliography: p. 259-274.Middle - Upper Devonian elastic strata in the Canadian Arctic Islands are present over an area of about 200,000 sq km (75,000 sq miles) and are up to 5000 m (16,000 1) thick. The strata comprise a elastic wedge which was deposited in the Franklinian geosyncline prior to Late Devonian - Early Mississippian deformation. The elastic wedge is divided into eleven formations, and six facies are recognized within the strata. The formations and their facies content are: Blackley (submarine fan); Cape de Bray (marine slope); Weatherall (deltaic-marine shelf); Bird Fiord (open marine shelf and deltaic-marine shelf); Strathcona Fiord (meandering stream); Hecla Bay (braided stream); Fram (meandering stream); Hell Gate {braided stream); Nordstrand Point (meandering stream); Beverley Inlet (meandering stream); and Parry Islands (braided stream, meandering stream and deltaic-marine shelf). Mineralogy, facies distributions, paleocurrent patterns and regional geology all indicate that the source areas of the elastic strata lay to the north and east, and included the Caledonian and Pearya Mountain systems and Precambrian Shield of Greenland. Chert and rock fragments characterize detritus from the Pearya Mountains whereas detritus from the Caledonian Mountains and Precambrian Shield is characterized by a high percentage of monocrystalline quartz. Compositional variations within the elastic wedge indicate that the Pearya Mountains progressively supplied a higher proportion of the detritus throughout wedge development. Paleolatitude estimations, lithologies, fossils and clay minerailogy imply that the elastic wedge was deposited under humid tropical climatic conditions. Lithologic variations in fluvial strata suggest that the climate fluctuated between savanna and very humid. Clastic deposition commenced in the extreme northeast in Eifelian time, and a coastal plain prograded south and west until it covered almost the entire Arctic Islands area by Middle Frasnian. During progradation, submarine fan and marine slope deposits infilled deep basins in the northwest. In Late Frasnian the entire area was uplifted and subjected to erosion. The area was transgressed in latest Frasnian, and a marine shelf was widespread by Early Famennian. In latest Devonian or Early Mississippian the elastic wedge was uplifted and folded to form a "foothills" belt encircling the southwestern termination of the Pearya Mountains. Sandstone units of delta front, beach and distributary channel origin within the Weatherall and Bird Fiord Fms are rated as having the highest potential for petroleum accumulations. The strata may have uranium potential but the meager data, presently available in this regard, are not encouraging

A Late devonian reef tract on northeastern Banks Island, N.W.T.

Bibliography: p. 116-118.The exposed Upper Devonian succession on northeastern Banks Island, N.W.T. is 3700 feet thick and has been correlated with the Griper Bay Formation. It consists mainly of terrigenous elastic rocks which were deposited in a marine shelf to coastal complex environment. The source area was located to the west. The age of the exposed section ranges from the base of the Frasnian to the Middle Famennian. Devonian strata have been moderately deformed,and north-south trending folds and normal faults are present. Deformation occurred during the Mississippian,and the structures were reactivated in the Tertiary. A 200 foot carbonate unit occurs in the middle of the succession . It has been herein named the Mercy Bay Member and is of Middle Frasnian age. It contains many organic buildups and represents a Devonian reef tract. The reef tract was located on the western shelf of an exogeosyncline which extended along the margin of North America between the stable craton and a western tectonic highland. The main facies changes in the Mercy Bay Member occur in an east-west direction. The organic buildups in the eastern part of the study area, which is the seaward edge of the reef tract, are narrow, linear bioherms which trend north-south. They are encased in younger terrigenous elastic rocks. To the west, the organic buildups, which are biohermal in the lower part and biostromal in the upper part, are more numerous. The lower bioherms trend east-west, and the inter-biohermal strata, which consist of dark, fine -grained, argillaceous limestones, are penecontemporaneous. The organic buildups on the western edge of the outcrop area are larger and are biohermal. The shoreward edge of the reef tract is not exposed. The lower portion of all the organic buildups is composed of corals and tabular stromatoporoids which built biogenetic banks in the quiet and intermediate energy zones. These energy zones are postulated to have been below 30 feet of water depth. The upper portion is composed of massive stromatoporoids which built rigid reefs in the high energy zone (above 30 feet). Successive sea level rises allowed the reefs to grow upward. The cessation of reef growth was caused by a rise in sea level and an influx of terrigenous sediment. The Griper Bay Formation appears to be a potential producer of hydrocarbons. The main potential reservoirs are the high energy coastal complex sandstones and possibly the organic buildups of the Mercy Bay Member

Aptian to Santonian Foraminiferal Biostratigraphy and Paleoenvironmental Change in the Sverdrup Basin as Revealed at Glacier Fiord, Axel Heiberg Island, Canadian Arctic Archipelago

Exceptional exposures of a High Arctic Cretaceous sedimentary record were studied at Glacier Fiord, Axel Heiberg Island. The succession reveals a complex Aptian to Santonian paleoenvironmental history of the Sverdrup Basin that documents several global events. Foraminiferal faunas in combination with rare macrofossil occurrences permit the distinction of nine zones that facilitate biostratigraphic correlations to other High Arctic locales, the Beaufort Mackenzie Basin and the Western Interior Sea. The depositional environment as exposed in the Christopher, Hassel, Bastion Ridge and Kanguk formations changed frequently from a shelf to a shoreface setting. Most sequence boundaries appear to be conformable where shoaling reached lower shoreface levels without subaerial exposure. An exception is the top of the Hassel Formation, correlated here with the Albian/Cenomanian disconformity where a paleosol developed on top of an upper shoreface environment. Transgressive/regressive sequences at Glacier Fiord correspond well with globally recognized transgressive/regressive mega cycles. The lower Christopher Formation shows frequent glendonite beds that attest to the Late Aptian/Early Albian cooling event. The required alkaline conditions for glendonites preserved the only calcareous faunule in the succession. Siliceous microplankton are assumed to be taphonomically removed due to deep burial. The Middle to Late Albian oceanic shelf conditions appeared to be most hospitable and foraminifera grew large tests. In the early Cenomanian and lower Bastion Ridge Formation, benthic species disappear. This sudden loss is interpreted as a consequence of nearby volcanic activity related to the Strand Fiord Formation and basin restriction. This is followed by a period of increased preservation of organic carbon and a distinct increase in marine productivity marking the OAE 2 in the Polar Sea straddling the Cenomanian/Turonian boundary. This interval is expressed in a platy shale, devoid of microbioturbation, but characterized with a repopulation event where the low oxygen tolerant genus Trochammina is the dominant component. The Upper Turonian to Santonian interval of the Kanguk Formation reflects shelf conditions that supported mostly rich benthic assemblages, but have at times minute tests as a response to oxygen depletion

Lower Triassic bryozoan beds from Ellesmere Island, High Arctic, Canada

In the Sverdrup Basin (Canadian Arctic), the Lower Triassic Blind Fiord Formation, comprising siltstone and shale, overlies various Middle to Late Permian (post-Wordian) sedimentary units. This formation is subdivided into three members: the Confederation Point, Smith Creek and Svartfjeld members of, respectively, Griesbachian-Dienerian, Smithian-Spathian and Spathian ages. Lower Triassic bryozoan beds are known from many sections of Ellesmere Island, but have never been studied in detail. During the Early Triassic biotic recovery interval, immediately following the Permian/Triassic extinction event, only one new bryozoan genus evolved in the Boreal region: Arcticopora. The first lower Triassic bryozoan bed appears in the upper part of the Confederation Point Member, and is dated as late Dienerian. Succeeding bryozoan levels occur in the upper Smith Creek Member, and are late Smithian-early Spathian in age. Bryozoan beds occupy a similar stratigraphic position in Spitsbergen. There, they occur scattered in silt to coarse sandstone beds, but also in bryozoan-dominated packstone beds resembling the packstone units in the uppermost part of the Confederation Point Member of Ellesmere Island. Previously, bryozoan-rich beds of Triassic age have not been reported, and the present work fills an important time gap in the bryozoan carbonate databas