Ian Knight

Basin evolution in western Newfoundland: New insights from hydrocarbon exploration

The Humber zone is the most external zone of the Appalachian orogen in western Newfoundland. It records multiphase deformation of the Cambrian-Ordovician passive margin and of the Ordovician to Devonian foreland basins by the Taconian, Salinian, and Acadian orogenic events. The recent phase of exploration drilling has provided new evidence for structural, stratigraphic, reservoir, and source rock maturation models of western Newfoundland. The first well, Port au Port 1, supported the hypothesis that the Round Head thrust had an earlier extensional history prior to the Acadian compressional inversion that created the present-day structural high of the Port au Port Peninsula. The well tested a small anticline formed in a footwall shortcut fault of the Round Head thrust. The second well, Long Point M-16, was drilled at the northern tip of Long Point to test a triangle zone identified by previous workers. This well demonstrates that the frontal monocline at the western edge of the triangle zone is elevated by a stack of imbricate thrusts composed of rocks of the Taconian allochthon and compressional basement-involved faults that have uplifted the Cambrian-Ordovician carbonate platform. The structural model developed in the Port au Port area with the aid of these wells has been extended throughout the Humber zone in western Newfoundland. Changes in structural style illustrated by regional cross sections suggest that prospective trap geometries are only developed in the southern and central parts of the region. The reservoir model proposed invokes exposure and karsting of the footwalls of extensional faults formed as the carbonate platform collapsed during a Middle Ordovician hiatus, the St. George unconformity. Structural relief became more pronounced as extensional collapse continued through the Middle Ordovician. (Begin page 394) These structurally high fault footwalls became the foci for dolomitizing and mineralizing fluids that used major faults as fluid conduits during the Devonian. Fluids deposited sulphide ores and created zebra and sparry dolomite and some sucrosic hydrothermal dolomites in the St. George Group and the Table Point Formation. The reservoir model, maturity and source rock data, and the structural models have been combined with seismic and onshore surface geology. This enables the prospectivity of the western Newfoundland Cambrian-Ordovician play trend to be evaluated for further exploration.

Late precambrian volcaniclastic deposits of the avalonian eastport basin (newfoundland appalachians): petrofacies, detrital clinopyroxene geochemistry and palaeotectonic implications

Abstract The Eastport basin contains over 5 km of well-preserved, marine volcaniclastic deposits, that comprise parts of the late Precambrian (Avalonian) Connecting Point and Love Cove groups of the eastern Newfoundland Appalachians. Basin infilling was dominated by deep-sea resedimentation of pyroclastic and epiclastic sediments. Four petrographically and texturally distinct petrofacies have been designated, viz.-tuffs, tuffaceous sandstones and conglomerates, feldspathic sandstones and conglomerates, polymict sandstones and conglomerates. A broad compositional spectrum of volcanogenic detritus, a copious supply of pyroclastic basaltic, andesitic, dacitic and rhyolitic ejecta, and the ubiquity of trace plutonic and metamorphic rock fragments are diagnostic provenance attributes of the basin-fill and these indicate derivation from an evolved magmatic arc, developed on a transitional or possibly continental crust. Detrital calcic clinopyroxenes and calcic amphiboles from the upper part of the Connecting Point Group are low in Ti and Al, display calc-alkaline and calc-alkaline to tholeftic affinity of the parental magma and plot in the field of orogenic basalts. Discriminant function analysis demonstrates that basalts and andesites were the main source of the detrital clinopyroxene. The clinopyroxene major-element chemistry is consistent with the evolved-volcanic-arc provenance suggested by petrographic data. Both datasets independently support other sedimentological and stratigraphic evidence that the Eastport basin records sedimentation adjacent to an active Avalonian-Cadomian volcanic arc, the remnants of which are preserved in part within the presently adjacent, predominantly volcanic Love Cove Group.

Early Ordovician (Skullrockian) trilobites of the Antiklinalbugt Formation, northeast Greenland, and their biostratigraphic significance

Abstract The Antiklinalbugt Formation of northeast Greenland comprises peritidal to subtidal carbonate sediments, deposited in shallow shelf settings during an early Tremadocian transgressive-regressive megacycle. The succession of shales and microbial, muddy and grainy limestone, with minor dolostone at the base and top, terminates at the cryptic Fimbulfjeld disconformity. The formation has yielded trilobites collected on Ella Ø, Albert Heim Bjerge, and Kap Weber by C. Poulsen (1920s and 1930s), J. W. Cowie and P. J. Adams (1950s), and during recent field studies in 2000 and 2001. The fauna includes dimeropygids Tulepyge cowiei and T. tesella n. spp., hystricurids Millardicurus and Hystricurus, and several species of Symphysurina. Micragnostus chiushuensis (Kobayashi, 1931) is rare, as are Chasbellus sp., Clelandia sp., and Lunacrania?. The presence of several Symphysurina species places the Antiklinalbugt Formation within the Symphysurina Zone. Chasbellus indicates the upper (lower Ordovician) part of the Symphysurina Zone for the lower upper Antiklinalbugt Formation. Conodonts place the middle lower formation in the Cordylodus intermedius conodont Biozone, the lower upper part in the Cordylodus angulatus conodont Biozone and the uppermost part in the Rossodus manitouensis conodont Biozone. This combined fauna is characteristic of the upper Skullrockian Stage of the Ibexian Series, with the lower part of the Antiklinalbugt Formation lying within the uppermost Cambrian of North America, and the upper part within the lower Ordovician. The entire formation lies within the global Tremadocian Stage of the early Ordovician.

Lower Ordovician trilobites from the Septembersø formation, North-East Greenland

McCobb, L.M.E., Boyce, W.D., Knight, I. & Stouge, S., 2014. Lower Ordovician trilobites from the Septembersø formation, North-East Greenland. Alcheringa 38, 575–598. ISSN 0311-5518. The informally named Septembersø formation is a 76 m thick succession of microbial and peritidal shelf carbonates deposited on the North-East Greenland shelf of Laurentia. The formation, assigned to the lower part of the Cape Weber Formation in all previous studies, lies disconformably upon the Skullrockian Antiklinalbugt Formation (revised) and conformably below the Tulean to Blackhillsian Cape Weber Formation (revised) in the Fimbulfjeld Group. With the exception of Randaynia, the modest trilobite fauna recovered from the Septembersø formation consists exclusively of bathyurids, and all represent new species. Both Chapmanopyge knudseni sp. nov. and Punka adamsi sp. nov. are represented by sufficient material to merit specific names. The remaining taxa, belonging to Bolbocephalus, Peltabellia, Randaynia and Chapmanopyge are left in open nomenclature. The trilobite genera present suggest that the Septembersø formation is referable to the Tulean Stage of the Ibexian Series, latest Tremadocian/earliest Floian in Global Standard terms. Lucy M. E. McCobb [lucy.mccobb@museumwales.ac.uk], Department of Natural Sciences, National Museum of Wales, Cathays Park, Cardiff CF10 3NP, UK; W. Douglas Boyce [dougboyce@gov.nl.ca] and Ian Knight [ianknight@gov.nl.ca], Geological Survey, Newfoundland and Labrador Department of Natural Resources, PO Box 8700, St. John’s, NL, Canada A1B 4J6; Svend Stouge [svends@snm.ku.dk], Natural History Museum of Denmark (Geological Museum), Øster Voldgade 5–7, DK-1350 Copenhagen K, Denmark.