Trans-Atlantic correlation of Late Cretaceous high-frequency sea-level cycles

Previous studies of Cretaceous sedimentary rocks have used multi-proxy correlation methods to suggest eustatic change, modulated by the c. 400 kyr long eccentricity rhythm. Although numerous authors have inferred eustatic changes on shorter timescales, none have demonstrated synchronous sea-level changes in separate basins on different plates, thousands of kilometres apart. Our study integrates basin-scale, three-dimensional sequence architecture, molluscan biostratigraphy, and carbon-isotope chemostratigraphy to demonstrate synchronous sea-level changes in upper Turonian to lower Coniacian shallow-marine clastic successions in the Western Canada Foreland Basin, and the Bohemian Cretaceous Basin. Depositional sequences in both basins are plotted in a common time domain using an astronomically calibrated age model, allowing direct comparison. In both basins, at least seven major transgressive events can be shown to be synchronous within the limits of combined biostratigraphic and chemostratigraphic resolution. ‘Major’ and ‘minor’ sequences of late Turonian age appear to have been paced, respectively, by the long (c. 400 kyr) and short (c. 100 kyr) eccentricity cycles. In contrast, early Coniacian sequences evidence pacing by the c. 38 kyr obliquity rhythm. Stratal architecture suggests that sequences developed in response to eustatic changes of c. 14–20 m at average rates ranging 0.08 to >1.3 m/kyr. At a time of ‘warm greenhouse’ climate, sea-level change of this magnitude and timescale may not be explicable entirely as a result of thermal- and aquifer-eustasy, and hence glacio-eustasy may also have been a contributing factor

Mud transport processes on a Cretaceous prodelta

Summary Various processes can transport mud offshore from river mouths. In shallow water, storm wave-resuspension and geostrophic flows are important. Where a significant slope exists, river flood-generated hyperpycnal flows can operate; wave-enhanced sediment gravity flows may transport mud over lower slopes. To test the relevance of these processes to an ancient delta succession, large thin sections of prodelta mudstone were made from mudstones that form allomember G of the Cretaceous Dunvegan Formation. Four mud facies were recognized: wave-rippled or massive clean silt, and silt-streaked mud record turbulent wave and current activity beneath a wave-enhanced sediment gravity flow. Upward gradation into structureless silty mud and clay-rich mud is interpreted to record deposition from poststorm settling of fluid mud. Upward-coarsening successions from mud to silt-streaked mud and silt may record waxing hyperpycnal flows linked to rising river floods. Micro-ripples in the more distal muds indicate paleoflow down the prodelta to the SE. Very fine sand beds in more proximal facies indicate winds from the NE and geostrophic and combined flows to the S and SE. A combination of stormdriven geostrophic flows and gravity-influenced density flows seem to have operated in conjunction to move mud up to ~120 km from the delta front

Arthropleura trails from the Westphalian of eastern Canada

Volume: 27Start Page: 843End Page: 85

Integrated, high-resolution allostratigraphic, biostratigraphic and carbon-isotope correlation of Coniacian strata (Upper Cretaceous), western Alberta and northern Montana

Inoceramid bivalves are the dominant invertebrate fauna of the Coniacian and basal Santonian of the Western Canada Foreland Basin in western Alberta. In the upper lower Coniacian through to basal Santonian, six successive faunas are recognized, which provide the basis for corresponding, formally defined inoceramid zones. From bottom upward these are the zones of: Cremnoceramus crassus crassus /C. deformis deformis, Inoceramus gibbosus, Volviceramus koeneni, Volviceramus involutus, Sphenoceramus subcardissoides, and Sphenoceramus ex gr. pachti. Particular faunas represent assemblages known widely from the Euramerican biogeographic region, although they characterize mostly its northern, boreal area. The inoceramid-based biostratigraphic scheme allows correlation with other parts of the North American Western Interior and with parts of the Euramerican biogeographic region. The studied succession provides a good record of the Inoceramus gibbosus Zone, which characterizes the topmost lower Coniacian. This zone, first recognized from northern Germany, is usually absent, both in Europe and in North America, due to a stratigraphic gap resulting from a eustatic lowstand. The base of the middle Coniacian is marked by the abrupt appearance of the taxonomically variable Volviceramus fauna (V. koeneni (Müller), V. exogyroides (Meek and Hayden)), with associated Inoceramus undabundus Meek and Hayden and Volviceramus cardinalensis, newly described herein. Scaphites (Scaphites) ventricosus Meek and Hayden, the ammonite marker of the base of the middle Coniacian first appears in the late early Coniacian. The base of the upper Coniacian marks the first appearance of the characteristic northern inoceramid species Sphenoceramus subcardissoides (Schlüter), the appearance of which coincides with Scaphites (Scaphites) depressus Reeside, the ammonite marker of this boundary. Close to this boundary Volviceramus stotti also appears, which is newly described from the Canadian sections. The base of the Santonian corresponds to the abrupt appearance of Sphenoceramus ex gr. pachti (Arkhangelsky). The studied sections demonstrate that the appearance of new inoceramid faunas (lowest occurrence of Cremnoceramus crassus crassus (Petrascheck), of various species of Volviceramus, Sphenoceramus subcardissoides (Schlüter) and of S. ex gr. pachti) takes place immediately above major marine flooding surfaces, suggesting a close correspondence between evolutionary and/or migration events and episodes of relative sea-level rise

Scaphitid ammonites from the Upper Cretaceous (Coniacian-Santonian) Western Canada Foreland Basin.

172 pages, 15 folded leaves of plates : illustrations (some color), maps (some color) ; 26 cm. chapter 1. Integrated, high-resolution allostratigraphic, biostratigraphic and carbon-isotope correlation of Coniacian strata (Upper Cretaceous), western Alberta and northern Montana / A. Guy Plint, Elizabeth A. Hooper, Meriem D. Grifi, Ireneusz Walaszczyk, Neil H. Landman, Darren R. Gröcke, João P. Trabucho Alexandre, and Ian Jarvis -- chapter 2. Inoceramid bivalves from the Coniacian and basal Santonian (Upper Cretaceous) of the Western Canada Foreland Basin / Ireneusz Walaszczyk, A. Guy Plint, and Neil H. Landman -- chapter 3. Scaphitid ammonites from the Upper Cretaceous (Coniacian-Santonian) Western Canada Foreland Basin / Neil H. Landman, A. Guy Plint, and Ireneusz Walaszczyk

Equatorward phytoplankton migration during a cold spell within the Late Cretaceous super-greenhouse

Abstract. Oceanic Anoxic Event 2 (OAE2), a ?600 kyrepisode close to the Cenomanian–Turonian boundary(ca. 94 Ma), is characterized by relatively widespread marineanoxia and ranks amongst the warmest intervals ofthe Phanerozoic. The early stages of OAE2 are, however,marked by an episode of widespread transient cooling andbottom water oxygenation: the Plenus Cold Event. This coldspell has been linked to a decline in atmospheric pCO2,resulting from enhanced global organic carbon burial. Toinvestigate the response of phytoplankton to this markedand rapid climate shift we examined the biogeographicalresponse of dinoflagellates to the Plenus Cold Event. Ourstudy is based on a newly generated geochemical and palynologicaldata set from a high-latitude Northern Hemispheresite, Pratts Landing (western Alberta, Canada). We combinethese data with a semi-quantitative global compilationof the stratigraphic distribution of dinoflagellate cyst taxa.The data show that dinoflagellate cysts grouped in the Cyclonepheliumcompactum–membraniphorum morphologicalplexus migrated from high to mid-latitudes during the PlenusCold Event, making it the sole widely found (micro)fossil tomark this cold spell. In addition to earlier reports from regionalmetazoan migrations during the Plenus Cold Event,our findings illustrate the effect of rapid climate change onthe global biogeographical dispersion of phytoplankton