First records of a plesiosaurian (Reptilia: Sauropterygia) and an ichthyosaur (Reptilia: Ichthyosauria) from Yukon, Canada

An isolated centrum collected ex situ from marine shales of the Lower Cretaceous (Albian) Arctic Red Formation along the Road River represents the first documented occurrence of a plesiosaurian from Yukon. This centrum represents the northernmost occurrence of plesiosaurians in the Western Interior Sea of North America prior to the establishment of the first continuous seaway (Western Interior Seaway) connecting the Boreal and Tethyan seas. Additionally, this centrum is potentially the secondoldest elasmosaurid specimen known from North America. A second centrum, collected along the Beaver River, is likely derived from the Lower Cretaceous (Lower Albian) Garbutt Formation exposed farther upstream. It represents the first report of an ichthyosaur from Yukon. Additionally, six associated ribs collected from the Arctic Re

Ammonite Faunal Dynamics Across Bio-Events During the Mid-and Late Cretaceous Along the Russian Pacific Coast

Jagt−Yazykova, E.A. 2012. Ammonite faunal dynamics across bio−events during the mid − and Late Cretaceous along th

Jurassic foraminifera from the Queen Charlotte Islands, British Columbia, Canada: Biostratigraphy, paleoenvironments and paleogeographic implications

Lower and Middle Jurassic (Sinemurian to Callovian) foraminifera were examined from 66 localities of the Queen Charlotte Islands, British Columbia, Canada. Over 200 species of well preserved benthic calcareous and agglutinated taxa belonging to 50 genera were identified. Foraminifera from the Lower Jurassic are represented by an abundant and diverse, Tethyan-derived calcareous assemblage, with Boreally derived agglutinated taxa becoming gradually more dominant in the upper Lower Jurassic to lower Middle Jurassic. Sedimentary strata and their faunal components and position of hiatuses correlate approximately with the Jurassic eustatic sea-level curve. Sea-level changes have resulted in a variety of depositional environments ranging from deep-water euxinic shales with abundant tuff beds, characterized by small pyritized foraminifera, to a well oxygenated outer shelf setting, characterized by a major faunal increase, to shoreface sandstones and conglomerates with absent to rare benthic foraminifera. A gradual shallowing from a slope- to a shelf-dominated deposition, with a magmatic arc provenance, is suggested for the Lower Jurassic, changing in the Middle Jurassic to an inner shelf to upper shoreface setting dominated by sedimentary strata of volcaniclastic origin. A marked faunal turnover is observed in the Lower Jurassic Whiteaves Formation (middle Toarcian) with the extinction of several earlier species and the appearance of a new diverse assemblage of 225 taxa. This turnover is also observed in the ammonite and radiolarian assemblages of the Queen Charlotte Islands. In comparison to the dominantly Tethyan-derived taxa of pre-middle Toarcian age, many of the species from the middle Toarcian are found in northern latitudes such as on the northern slope of Alaska, Arctic Islands and the Northwest Territories. Hence, foraminifera, in conjunction wit

Episodic photic zone euxinia in the northeastern Panthalassic Ocean during the end-Triassic extinction

Severe changes in ocean redox, nutrient cycling, and marine productivity accompanied most Phanerozoic mass extinctions. However, evidence for marine photic zone euxinia (PZE) as a globally important extinction mechanism for the end-Triassic extinction (ETE) is currently lacking. Fossil molecular (biomarker) and nitrogen isotopic records from a sedimentary sequence in western Canada provide the first conclusive evidence of PZE and disrupted biogeochemistry in neritic waters of the Panthalassic Ocean during the end Triassic. Increasing water-column stratification and deoxygenation across the ETE led to PZE in the Early Jurassic, paralleled by a perturbed nitrogen cycle and ecological turnovers among noncalcifying groups, including eukaryotic algae and prokaryotic plankton. If such conditions developed widely in the Panthalassic Ocean, PZE might have been a potent mechanism for the ETE

Paleoenvironmental and chronological constraints on the Mount Tatlow succession, British Columbia: First recognition of radiolarian and foraminiferal faunas in the Intermontane Cretaceous back-arc basins of Western Canada

The Cretaceous succession at Mount Tatlow, British Columbia, is a cornerstone of Cordilleran stratigraphy, preserving a mos

Cenomanian to Santonian radiolarian biostratigraphy, carbon isotope stratigraphy and paleoenvironments of the Sverdrup Basin, Ellef Ringnes Island, Nunavut, Canada

An upper Albian to Santonian sedimentary record on Ellef Ringnes Island, Canadian Arctic Archipelago, records variable paleoenvironmental conditions within the Cretaceous Polar Sea and Sverdrup Basin. The upper Albian to lower Cenomanian uppermost Christopher and Hassel formations represent a regressive system tract from offshore to shoreface/terrestrial paleoenvironments. The upper Cenomanian to Santonian shales of the Kanguk Formation signify a distal offshore basin setting controlled by increased subsidence and high global sea levels. Siliceous pelagic faunas and floras dominate the basin and herein, three informal radiolarian partial range zones are proposed for the Polar Sea. Alternating diversity and abundance patterns are interpreted as a response to sea-level controlled productivity systems. Transgressive phases correspond to low diversity shallow dwelling radiolarian taxa with an expanded oxygen minimum zone (OMZ); regressive phases are coupled with radiolarian radiations of deeper dwelling species and a depressed OMZ. The upper Cenomanian to Turonian was marked by increased preservation of marine-type organic matter and organic carbon isotope excursions indicate the presence of the Oceanic Anoxic Event 2 (OAE 2) at the base of the Kanguk Formation. Rock Eval data suggest that an increasing terrestrial influence prevailed during the Coniacian to Campanian time covering the OAE 3. Benthic environments are dominated by anoxic conditions, as suggested by the near lack of benthic foraminifera and extensive intervals of fine platy shale lacking bioturbation. Only the upper Coniacian records a return to dysoxic benthic conditions. Radiolarian faunal comparisons to more southern localities suggest migration routes from the east through a narrow North Atlantic pathway and from the Pacific through the Alaskan-Asian Pathway