Cretaceous volcanic rocks, which consist mainly of basalt flows and pyroclastic rocks, occur on northern Ellesmere Island, Axel Heiberg Island, and northernmost Amund Ringnes Island as part of the Sverdrup Basin succession. Volcanic rocks are associated with each of four regional transgressive–regressive (T–R) cycles that constitute the Cretaceous clastic succession of Sverdrup Basin and are of Valanginian – early Barremian, late Barremian – Aptian, latest Aptian – early Cenomanian, and late Cenomanian – Maastrichtian age; the volcanic component of each increases northward. The centre of volcanism appears to have been north of Ellesmere Island and is interpreted as the site of a mantle plume that was active throughout the Cretaceous.Most of the volcanic activity took place from Hauterivian to early Cenomanian (T–R cycles 1–3) and was accompanied by widespread sill and dyke intrusion. This activity coincided with the main rifting phase of the adjacent oceanic Canada Basin and with minor crustal extension in the Sverdrup Basin. From late Cenomanian to Campanian, volcanism was restricted to the extreme northeast, and trachytes and rhyolites were extruded along with basalts. This volcanic succession is interpreted as being the southern limit of Alpha Ridge, a major volcanic edifice that formed as a hot-spot track across Canada Basin during sea-floor spreading in Late Cretaceous.

The Early Triassic record, from the Smithian stratotype, shows that the organic carbon isotope record from northwest Pangea closely corresponds to major fl uctuations in the inorganic carbon records from the Tethys, indicating truly global perturbations of the carbon cycle occurred during this time. Geochemical proxies for anoxia are strongly correlated with carbon isotopes, whereby negative shifts in δ 13 C org are associated with shifts to more anoxic to euxinic conditions, and positive shifts are related to return to more oxic conditions. Rather than by a delayed or prolonged recovery, the Early Triassic is better characterized by a series of aborted biotic recoveries related to shifts back to ocean anoxia, potentially driven by recurrent volcanism.

Transgressive–regressive (T–R) sequence analysis has been applied to the Jurassic succession of the Sverdrup Basin with sequence boundaries drawn at subaerial unconformities or the correlative transgressive surfaces. A hierarchal system of sequence order that reflects the different nature of the boundaries has been formulated on the basis of boundary characteristics. Second- through fifth-order sequences have been recognized in the Jurassic succession, which itself is part of a first-order sequence of mid-Permian – Early Cretaceous age.The Jurassic strata occur within four second-order sequences. The boundaries of these sequences are characterized by widespread subaerial unconformities across which major changes in depositional and subsidence regimes occur. These boundaries are earliest Rhaetian, earliest Pliensbachian, earliest Bajocian, earliest Oxfordian, and Hauterivian in age.Each second-order sequence is divisible into a number of third-order sequences bounded mainly by basin-wide transgressive surfaces with subaerial unconformities present on the basin margins. The ages of the 10 Jurassic third-order sequences are Rhaetian – Hettangian, Sinemurian, Pliensbachian – Toarcian, late Toarcian – Aalenian, Bajocian, Bathonian, Callovian, Oxfordian – early Kimmeridgian, late Kimmeridgian – early Tithonian, and late Tithonian. The third-order sequences commonly contain three to six fourth-order sequences. These sequences are bound entirely by transgressive surfaces that can be correlated only over a portion of the basin.A good correlation between the second- and third-order transgressive events of the Sverdrup Basin and proposed global events is observed. This worldwide occurrence suggests that the events in part reflect eustatic sea-level changes. The characteristics of the second- and third-order boundaries also indicate that each had a tectonic influence that resulted in a rapid relative sea-level fall (uplift) followed by a rapid rise (subsidence). Given the apparent combination of tectonic and eustatic influence on the generation of the second- and third-order sequence boundaries, they are interpreted to reflect significant plate-tectonic reorganizations that affected the intraplate stress regimes of the oceanic (eustatic) and continental (tectonic) portions of each lithospheric plate.

A refined scheme o~ reefal limestone classification, which places more emphasis on the > 2 mm components (conglomeratic fraction) and on the mode of organic binding, allows for a more detailed facies description of organic buildups. The classification has been applied to Late Devonian organic buildups which outcrop on northeastern Banks Island, Canadian Arctic Archipelago. The distribution and sequences of facies in one organic buildup has led to the determination of absolute water depth limits of three major Late Devonian paleoecological zones. Corals were the dominant fauna below 70 feet (21 m.); tabular stromatoporoids flourished between 70 feet (21 m.) and 30 feet (9 m.) of water depth; massive stromatoporoids were the dominant fauna between 80 feet (9 m.) and sea level. The main controlling factor on the depth limits of the zones was wave energy (normal wave base, 80 feet [9 m.]; storm wave base, 70 feet [21 re.l). R6sum~Une classification sch6matique et d6taill6e des calcaires de r6cif sup~rieur insistant sur les constituents d'une grosseur ~ 2 mm. (fraction comglomeratique) et sur la mani~re avec laquelle les constituents ont 6t6 li6 spar des organismes permet une d6scription plus d6taill6e des facies d'6difices organiques. Elle a 6t6 appliqu6e ~ l'6tude de r6cifs qui affleurent dans la partie Nord-est des Banks Island dans l'archipel arctique canadien.Lad distribution et la succession des facies dans un 6difice organique ont permit de pr6ciser les limites des profondeurs absolues d'eau de trois zones pal6o6cologiques principales du d6vonien sup6rieur. Des coraux formaient la faune pr6pond6rante audessous de 21m.; stromatop6roides tabulaires abondaient entre 2Ira. et 9m. de profondeur; des stromatoporoides massifs formaient la faune pr6pond6rante entre la surface de la mer et 9m. de profondeur. Le facteur principal fixant les limites de profondeur des zones pal6o6cologiques 6tait l'6nergie des vagues (base des vagues normales 9 m., base des vagues de temp~te 21 m.). *) Authors' addresses: ASaTON F. EMBRY, III, Mobil Oil Canada Ltd., Calgary, Alberta, Canada; J. EDWARD KLOVAN, The University of Calgary, Calgary, Alberta, Canada. 672 A. F. EMBRY, J. E, KLOVAN --Absolute Water Depth Limits of Late Devonian Is co~ep~aHneCxeMa RzaccHOnKaunH pHqboB1ax 1/13BeCTHHHOB, nprt HOTOpO~ MO~HO pa3ziHqaTb COCTaBHLIe qacTH 6oaee 2 MM (Konr~oMepaTHafI qaCTb) n BH~ opranHqec~nx o6pa-3OBaHH~, pa3pemaeT woqltee onHcaTb ~)aii~i~ pI~)OB. 3Ty I~acc~i~]~nl~ar~r~Io npnMetU~JIH K BepxHe-~eBOHCHRM pH(~aM, HOTOpbIe o6pa3ymT ceBepo-eocwoquyIo qaCTb 6aHoH HcJIaH~C',~OFO 14 Harla~gHoro apHTr~qecKoro apxnHe~ara. Pacnpe~eJienge ~at~H~ ~ ero qepeaonanne B p~q~e pa3pemamT onpe;~eJmwb a6co~mwnym r~y6nHy no~Li B Tpex BaH~HBIX BepxHe~eBOHCHHX 8oHax. l~opaaaH HBJIHJIHCb rocno~cTnyiou~efr qbaHne~ Ha r~y@He 5oaee 21 M; cTepmnenbm cTpOMaTO~trITbI pocJtH Ha raySnue 21--9 M; MaCenBH~e cTpoMaTonopn~l~i rocno~icTeoBa~n OT r~ySnHI)t 9 M XO noBepxnocTn BO;~BL Ba~negrmn~t qba~TOpOM, o~]pe3ean~outHM ray6nny rpannq~ OTnX 3OH, ~Bnnac~ ~eprr~ Bo~noxo~...