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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.

In north-central Alberta and adjacent British Columbia, clastic strata of the middle to late Albian Peace River and Shaftesbury formations were deposited in alluvial to shallow marine environments across the foredeep of the Western Canada Foreland Basin. A high-resolution, log and core-based allostratigraphic framework for the Paddy Member of the Peace River Formation established nine allomembers, PA to PI, bounded by flooding surfaces and apparently equivalent non-marine surfaces. Within the estimated 2 Myr. duration of the Paddy, allomembers allow the evolving palaeogeography and changing relationship between accommodation and sedimentation rates to be analysed on time-steps on the order of 105 yrs. Paddy strata fill an arcuate depocentre ~ 300 km wide, across which the rocks thin eastward from 125 m to ~ 5-10 m. The northern part of the basin is occupied by muddy, offshore marine deposits that pass abruptly southward into a linear, WSW-ENE-trending body of sandstone deposited in a wave-dominated barrier-strandplain, at least 350 km long. Extending > 200 km to the south of the strandplain was a region of shallow brackish to freshwater lagoons and lakes that graded to the SW into alluvial facies. Within the lagoon region, few m thick, elongate and patchy sandstones represent river dominated deltas. In allomembers PA to PG, these sandstones are concentrated in the west and south, implying supply from the western Cordillera. In allomembers PH and PI, sandstones are mainly in the east and have a distinctive, quartz-rich composition. They can be correlated eastward into the coeval Pelican Formation, and were probably sourced from the Canadian Shield on the opposite side of the basin. In the western foredeep, alluvial rocks comprise aggradational, unconfined floodplain deposits with ribbon sandstones, dissected, on at least nine separate levels, by paleovalleys that are confined to the proximal foredeep. Valleys are 10-20 m deep, few km-wide, and filled with multi-storey channel-bars of pebbly coarse sandstone or conglomerate. Valleys cut down from well-developed interfluve palaeosols that record a falling and then rising water table. Alternating aggradation and degradation, and advance and retreat of the alluvial gravel front is attributed to cycles of varying rainfall intensity, rather than tectonism or eustasy. Apparently coeval transgressive-regressive successions in the lagoon and marine regions are attributed to few-m scale eustatic changes. On the NE margin of the basin, tidal sandstone fills a northward-opening estuary cut on the basal Paddy unconformity. This sandstone contains the first well-documented specimens of Gnesioceramus comancheanus (Cragin), proving contemporaneity with at least part of the marine Joli Fou Formation to the east. Paddy allomembers change shape upward from short blunt wedges, through more acutely tapered wedges, to sheets. This change reflects initially rapid flexural subsidence, attributed to active thickening of the adjacent orogenic wedge. A waning rate of deformation permitted wider dispersal of sediment across the basin, driving broad isostatic subsidence beneath increasingly sheet-like rock bodies. A major hiatal surface, VE3, records non-deposition or subtle erosion attributed to erosional unloading and uplift of the adjacent orogen. A subsequent marine transgression is attributed to renewed thickening of the tectonic wedge that triggered deposition of marine mudstone that thickens westward from 0 to > 110 m over 300 km. A postulated Milankovitch-band climatic control on both local gravel supply (via fluctuating rainfall), and shoreline movement (via ?Antarctic glacio-eustasy or groundwater storage), might account for cycles of alternating incision and aggradation in the alluvial realm. The same mechanism may also explain why shallow marine units such as the Cretaceous Viking and Cardium formations contain abundant conglomerate in lowstand shoreface deposits (higher river discharge), yet have highstand shorelines dominated by sandstone (lower river discharge). This article is protected by copyright. All rights reserved.

The Upper Cretaceous (Coniacian-Santonian) of the Western Canada Foreland Basin, contains a rich record of scaphitid ammonites (scaphites). We describe four species: Scaphites (Scaphites) preventricosus Cobban, 1952, Scaphites (S.) ventricosus Meek and Hayden, 1862, Scaphites (S.) depressus Reeside, 1927, and Clioscaphites saxitonianus (McLearn, 1929). These are widespread index fossils that demarcate the upper lower-middle, middle, and upper Coniacian, and the lower Santonian, respectively. They occur in the lower part of the Wapiabi Formation, Alberta. The Coniacian part of the section has been divided into 24 informal allomembers based on the recognition of marine flooding surfaces, most of which can be traced through the >750 km extent of the study area. The most distinctive feature in the ontogenetic development of scaphites is the change in coiling during ontogeny. At the approach of maturity, the shell uncoils slightly, forming a shaft, which then recurves backward approaching the earlier ...

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. ...

The biostratigraphy of the uppermost Cenomanian – Lower Turonian succession in the lower part of the Blackstone Formation exposed in the Ram River (Alberta, Canada), is interpreted in terms of the standard inoceramid/ammonite zonation of the interval. Four successive inoceramid zones are recognized, those ofInoceramus pictus,Mytiloides puebloensis,M. kossmati, andM. mytiloides, as established in the stratotype section at Pueblo, Colorado. Their correlation to Pueblo is confirmed by ammonite data.The mid-Early Turonian zone ofM. kossmatiyielded an assemblage ofInoceramus, with species showing close affinity to the latest Cenomanian lineages. This multi-species sample proves the survival ofInoceramuslineages into the otherwiseMytiloides-dominated Early Turonian, and indicates that their disappearance from the record of the North American Western Interior was not because of their extinction. It is suggested that the apparent lack ofInoceramusin Lower Turonian strata is due to an extremely low population abundance in the Early Turonian sea.

An echinoderm association is reported from the ?early late Albian Paddy Member of the Peace River Formation of British Columbia, Canada. The association includes Frasericrinus mauricensis gen. et sp. nov., two additional distinctive crinoid column types, a poorly preserved asteroid, and an umbilical fragment of the cephalopod Stelckiceras. This is the first report of a Cretaceous isocrinid from North America. The echinoderm fossils are from the top of a succession of storm-deposited sandstones and mudstones (Boulder Creek Formation) that can be correlated southward into nearshore and terrestrial facies of the Paddy Member of the Peace River Formation. The echinoderm fossils were buried (and probably lived) about 12–14 km from the contemporaneous shoreline in an estimated water depth of 10–20 m. Integration of biostratigraphic and allostratigraphic schemes suggests that the echinoderms are of earliest late Albian age. The association of the echinoderm fauna with ammonites of Boreal affinity indicates deposition in northern waters, although the presence of Tethyan inoceramids in apparently coeval Paddy Member strata 270 km to the east suggests that northward-advancing water from the Gulf of Mexico had reached northwestern Alberta, if not actually merged with the Boreal embayment. The nearshore occurrence of Cretaceous stalked crinoids is indicative of an asynchronous, gradual migration of stalked crinoids to deep-water habitats, to which they are restricted in modern oceans.

Determining sediment transport direction in ancient mudrocks is difficult. In order to determine both process and direction of mud transport, a portion of a well-mapped Cretaceous delta system was studied. Oriented samples from outcrop represent prodelta environments from ca 10 to 120 km offshore. Oriented thin sections of mudstone, cut in three planes, allowed bed microstructure and palaeoflow directions to be determined. Clay mineral platelets are packaged in equant, face-face aggregates 2 to 5 μm in diameter that have a random orientation; these aggregates may have formed through flocculation in fluid mud. Cohesive mud was eroded by storms to make intraclastic aggregates 5 to 20 μm in diameter. Mudstone beds are millimetre-scale, and four microfacies are recognized: Well-sorted siltstone forms millimetre-scale combined-flow ripples overlying scoured surfaces; deposition was from turbulent combined flow. Silt-streaked claystone comprises parallel, sub-millimetre laminae of siliceous silt and clay aggregates sorted by shear in the boundary layer beneath a wave-supported gravity flow of fluid mud. Silty claystone comprises fine siliceous silt grains floating in a matrix of clay and was deposited by vertical settling as fluid mud gelled under minimal current shear. Homogeneous clay-rich mudstone has little silt and may represent late-stage settling of fluid mud, or settling from wave-dissipated fluid mud. It is difficult or impossible to correlate millimetre-scale beds between thin sections from the same sample, spaced only ca 20 mm apart, due to lateral facies change and localized scour and fill. Combined-flow ripples in siltstone show strong preferred migration directly down the regional prodelta slope, estimated at ca 1 : 1000. Ripple migration was effected by drag exerted by an overlying layer of downslope-flowing, wave-supported fluid mud. In the upper part of the studied section, centimetre-scale interbeds of very fine to fine-grained sandstone show wave ripple crests trending shore normal, whereas combined-flow ripples migrated obliquely alongshore and offshore. Storm winds blowing from the north-east drove shore-oblique geostrophic sand transport whereas simultaneously, wave-supported flows of fluid mud travelled downslope under the influence of gravity. Effective wave base for sand, estimated at ca 40 m, intersected the prodelta surface ca 80 km offshore whereas wave base for mud was at ca 70 m and lay ca 120 km offshore. Small-scale bioturbation of mud beds co-occurs with interbedded sandstone but stratigraphically lower, sand-free mudstone has few or no signs of benthic fauna. It is likely that a combination of soupground substrate, frequent storm emplacement of fluid mud, low nutrient availability and possibly reduced bottom-water oxygen content collectively inhibited benthic fauna in the distal prodelta.

Marine mudstone of the Coniacian Muskiki Member was deposited by storms on a shallow-marine ramp across southern Alberta and northern Montana. The rocks range from the C. crassus crassus Zone of th...

During the middle Albian, a southward incursion of the Boreal Ocean flooded northern Alberta and adjacent British Columbia, forming a large embayment known as the Hulcross Sea. Marine mudstones of the Hulcross Formation and Harmon Member of the Peace River Formation record transgression, whereas sandstones of the Cadotte Member of the Peace River Formation record shoreline regression to the north. Abundant hummocky and swaley lamination in the Cadotte sandstone attest to the influence of storms on a shallow shelf. The Cadotte sandstone undergoes a lateral facies change from mud-free shoreface sandstone in the south to heterolithic offshore facies in the north. An articulated crinoid was found within a hummocky sandstone bed about 15 km seaward (north) of the shoreface-shelf facies transition. The articulated state of the crinoid indicates that it was buried very rapidly, and never exhumed. The arms through 20 mm of the column are preserved, but because the details of the aboral cup are not well preserved, this specimen must be left in open nomenclature. The elliptical columnals with a concave latus in the distal portion of the preserved column ally this specimen to the Bourgueticrinida, although with details of the aboral cup lacking and other characters atypical for Mesozoic bourgueticrinids, the Canadian specimen is placed in Bathycrinidae indeterminate. The oldest previously recorded bathycrinids were from the Upper Cretaceous (Maastrichtian), thus this report extends their range to the Lower Cretaceous (Albian).

The stratigraphy of Cretaceous rocks in the Western Canada Foreland Basin is well constrained by dense borehole data that allow three-dimensional mapping of transgressive–regressive events, paleogeography, and subsidence patterns. However, it is difficult to estimate rates of change or to place events in a precise temporal framework because very few of the many bentonite beds have been dated using modern techniques. In this study, two bentonites, of at least regional extent, were dated using isotope dilution – thermal ionization mass spectrometry (ID–TIMS) U–Pb methods on chemically abraded zircon crystals. The older bentonite correlates with the “X” bentonite of the late middle Cenomanian and yields an age of 95.87 ± 0.10 Ma. The Bighorn River Bentonite, which lies just below the Cenomanian–Turonian boundary, yields an age of 94.29 ± 0.13 Ma and is interpreted to equate with the “B” bentonite and bed 80 at Pueblo, Colorado. Both bentonites dated here are older than the previously reported 40Ar/39Ar ages from correlative United States samples, supporting the observation that 40Ar/39Ar ages may systematically underestimate ages of Cretaceous bentonites by ∼1%, as suggested by other recent studies. The X bentonite immediately precedes a major late middle Cenomanian eustatic transgression that inundated the Dunvegan delta complex. The new ages for the X and Bighorn River bentonites indicate an average minimum subsidence rate of ∼0.27 mm/year in the most proximal part of the Cenomanian foredeep in northeast British Columbia during this time. The new age of the Bighorn River Bentonite, coupled with the orbitally tuned time scale of Sageman et al. (2006) , suggests a Cenomanian–Turonian boundary age of 94.12 ± 0.13 Ma.

New allostratigraphic correlations in west-central Alberta show that flooding surfaces in the Sunkay and basal Vimy members of the Blackstone Formation can be traced eastward from Burnt Timber Creek for >500 km to western Saskatchewan, and for 350 km northward into the Dunvegan and Kaskapau formations. At Burnt Timber Creek, a Miliammina manitobensis microfauna in the lowest 1 m of the Sunkay Member indicates equivalence to the Westgate Formation, and an overlying 70 cm conglomerate is correlative with the Fish Scales Formation. Overlying mudstones contain foraminifera of the Verneuilinoides perplexus Zone, indicative of the middle Cenomanian Belle Fourche Formation. The base of the Second White Specks Formation, as currently defined in core in eastern Alberta, equates in outcrop with the lower part of the Sunkay, rather than the base of the Vimy Member as previously thought. The base of the Second White Specks Formation should be placed about 35 m higher in the stratotype core. A bentonite located 9.3 m above the base of the Sunkay Member at Burnt Timber Creek lies near the highest occurrence of Evolutinella sp. aff. E. apricarius, indicating proximity to the "X" bentonite, recognized across the prairies and traceable north into allomember C of the Dunvegan alloformation. A thick bentonite 93.2 m above the base of the Burnt Timber Creek section lies 4 m above the base of the Vimy Member; this bentonite, traceable from northern British Columbia to New Mexico, lies a few metres below the Cenomanian–Turonian boundary and is here formally named the Bighorn River Bentonite.

A black marine mudstone in allomember A of the middle Cenomanian Dunvegan Formation, Alberta, yielded a well-preserved, deep-bodied fish skeleton attributable to a new genus and species, Tycheroichthys dunveganensis, in the Paraclupeidae (Clupeomorpha, Ellimmichthyiformes). This new taxon appears most closely related to members of the subfamily Paraclupeinae, which includes largely freshwater and estuarine or marginal marine species known from South and Central America and China. The Dunvegan Formation represents a large delta complex deposited in the Western Interior Seaway at about 65°N, where mean sea water temperature may have been about 10 °C. The specimen was found about 60 km from the contemporaneous shoreline, and, in life, apparently inhabited a shallow, muddy pro-delta environment characterized by high turbidity and variable salinity. The fish may have died when it was engulfed by brackish floodwater that also introduced suspended mud that rapidly buried the body, preventing physical disarticulation of the skeleton. River outflow probably produced a salinity- and density-stratified water column that limited oxygen transfer to the sea floor, leading to dysaerobic bottom water and an absence of scavengers. High terrestrial phytodetrital content of the sediment also favoured anaerobic conditions that limited bacterial decay.

The Middle Turonian Kaskapau Formation in the Rocky Mountain Foothills of northeastern British Columbia comprises up to 950 m of shallow marine sandstones cyclically interstratified with marine mudstones and minor lagoonal deposits. Transgressive surfaces are commonly mantled by thin pebble lags. A transgressive pebble lag exposed in Quality Creek near Tumbler Ridge town site includes rare, well-rounded quartzite cobbles and a quartzite boulder, which were deposited at a paleolatitude of about 67°N. Encrusting organisms are unevenly distributed over five of the largest clasts. Disciniscid brachiopods are abundant on one cobble but are otherwise rare. A conical-shelled lingulate brachiopod with concentric growth lamellae occurs sparsely, and a weakly ribbed lingulate brachiopod is represented by one shell. Serpulid worm tubes, encrusting bryozoans, and possible basal attachments of corals are also present. Attached foraminifera are abundant and distributed over several clasts. Generic diversity an...

The Kaskapau Formation is a mudstone-dominated wedge up to 950 m thick that spans late Cenomanian to middle Turonian time. The formation has a prominent wedge geometry and was deposited in the foredeep of the Western Canada Foreland Basin. In outcrop in northeast British Columbia, nearshore sandstones are locally well developed and include rare wedges of nonmarine strata. On Quality Creek, near Tumbler Ridge, 11 m of nonmarine strata contain abundant dinosaur tracks and the first in situ dinosaur bone reported from British Columbia. This site, at a paleolatitude of about 67°N, preserves a rare glimpse of Turonian terrestrial environments during global eustatic highstand. Three main dinosaur habitats are recognized: strandplain and beach-ridge; freshwater lake; and brackish lagoon. Back-beach sandstone has a relief of about 2.5 m, interpreted as beach ridges; sandy coals containing abundant dinosaur tracks represent inter-ridge slough deposits. Overlying lake deposits comprising laminated muds with freshwater molluscs grade up into rooted muddy siltstone and locally, dinoturbated sandstone. Lake deposits are capped by lagoonal mudstone with abundant brackish-water molluscs, locally including a dinosaur-trampled oyster bioherm. The upper parts of sandy lagoonal deltas are pervasively dinoturbated. Sandstone filling a tidal channel contains logs, oyster shells, and bones of dinosaurs, turtles, and crocodiles, as well as fish scales. The lagoonal succession is erosively overlain by offshore sandy mudstones. Various lines of evidence suggest that the mean annual temperature at this sea-level location was about 14 °C, with a cold-month mean no less than 5.5 °C. The high-latitude location implies a significant period of winter darkness, and correspondingly diminished plant productivity.

Lower to upper Coniacian rocks in the foredeep of the Western Canada Foreland Basin are dominated by mudstone and subordinate sandstone and were deposited on a very low-gradient, storm-dominated marine ramp. The rocks are organized into several scales of upward-coarsening, upward-shoaling succession, bounded by marine flooding surfaces. Abundant, publicly available wireline log data permit flooding surfaces to be traced for hundreds of kilometers in subsurface. Flooding surfaces can be considered to approximate time surfaces that allow the subsidence history of the basin to be reconstructed. Particularly widely traceable flooding surfaces were chosen, on pragmatic grounds, as the boundaries of 24 informal allomembers, most of which can be mapped along the foredeep for >750 km. Allomembers can also be traced westward into the fold-and-thrust belt to outcrop in the Rocky Mountain Foothills. Some flooding surfaces are mantled with intra- or extrabasinal pebbles that imply a phase of shallowing and, ...

Early-late Cenomanian rocks of the Doe Creek unit are near the base of the Kaskapau Formation and were deposited in a broad, very shallow embayment that occupied the foredeep of the Western Canada foreland basin. The Doe Creek unit consists of 13 upward-shoaling sequences, typically 3–10 m thick. Subsurface correlation shows that sequences can be traced for 100–350 km from the fore-deep toward the forebulge. On the proximal and distal margins of the embayment, each sequence is capped by a flooding surface, commonly underlain by a paleosol developed in marine mudstone. In the center of the embayment, most sequences are capped by one or more isolated, sharp-based sandstone bodies interpreted as lowstand delta-front deposits. Flooding surfaces on top of each sequence are continuously traceable in well logs from the foredeep to the vicinity of the forebulge, implying simultaneous transgression across the basin. Every sequence shows an abrupt upward shallowing, usually to emergence, that was caused by accommodation loss, not sediment accumulation. A vertical relative sea-level excursion of ∼10 m on a time scale spanning a maximum range of ∼9–74 k.y. is estimated for each sequence. Because transgressions and regressions appear to be in phase across the basin, sequences are better explained by eustasy rather than by flexural reciprocal sedimentation: a glacioeustatic mechanism provides the most likely explanation.