Anton Wroblewski

University of Utah | UOU · Department of Geology and Geophysics

Jurassic and Palaeocene tidal deposits of the epeiric Western Interior Sea in Wyoming, USA, differ significantly due to their contrasting climates and tectonic, geographic and depositional settings. Tidally generated, cross‐bedded sandstone bodies contained by incisions are common to both settings and can potentially be uncritically attributed to m...

Oxfordian deposits in northern Colorado and Wyoming, USA preserve proximal, intertidal, clastic, coastal deposits and distal, offshore to nearshore, subtidal bioclastic facies that accumulated during a forced regression of the Jurassic epeiric Sea. This contrasts with the common association between tidal deposits, carbonate facies, and rising sea l...

An evolving tectonic setting during the Late Cretaceous and Paleocene drove the dramatic transformation of southern Wyoming from a broad marine shelf setting to a series of lacustrine basins. Early dominant control of depositional patterns by flexural tectonics gave way to control by dynamic topography and Laramide-style deformation. The southern W...

This study defines a new workflow to investigate the internal facies architecture of a river-dominated delta deposit using outcrops of the Cretaceous Panther Tongue of the Star Point Sandstone in central Utah, U.S.A. Photorealistic virtual outcrop models (VOM) were created from ~13 linear-km of outcrop. The VOMs, alongside field observations, were...

An enigmatic transition from the storm‐dominated, offshore to lower shoreface deposits of the Redwater Shale Member (Sundance Formation) to the overlying mixed tidal and aeolian Windy Hill Sandstone (Morrison Formation) in the Oxfordian of the North American Western Interior has long been a source of intrigue. Previously proposed drivers include th...

Influence of bottom-currents and tectonic activity on shelf sedimentary processes and sand distribution remain poorly constrained. A growing body of research highlights the importance and variability of the shelf sandstone bodies. To explore the roles of fluvial, wave, and bottom current-controlled sediment distribution in the Western Interior Seaw...

Sedimentary structures unique to tidally influenced environments and unambiguously salinity-stressed marine ichnofossil assemblages in the lower Paleocene Ferris and upper Paleocene Hanna formations of Wyoming's Hanna Basin (HB) necessitate major revision of local and regional reconstructions of the Paleocene Western Interior Seaway (WIS). Preserve...

Plaster and resin burrows casts of modern firmground (Tortopus circumfluus) and softground (Hexagenia limbata) mayfly larvae offer new insights into the paleoenvironmental significance of S-, J-, U-, and pouch-shaped ichnofossils. T. circumfluus in the Colorado River, southeastern TX, USA excavates U- and pouch-shaped burrows up to 35 mm long with...

A survey of modern and ancient back-barrier deposits reveals a diversity of depositional styles, processes, lithotypes, and ichnocoenoses. The modern Galveston-Trinity Bay (GTB) is a classic example of a microtidal, humid subtropical, siliciclastic back- barrier complex and has been “the model” for back barrier systems for decades. While some ancie...

Outcrops of the Bathonian-Oxfordian Sundance Formation (SF) at Wyoming’s Glendo (GR), Alcova (AR), and Seminoe (SR) Reservoirs offer the opportunity to test the hypotheses that: 1) the J5 unconformity does not exist, 2) the Windy Hill Member (WH) accumulated as a large tidal delta analogous to the Han River delta, and 3) the SF is divisible into a...

Evidence for the earliest invasion of the marine realm by mammals was previously restricted to Eocene (48.6–37.8 Ma) skeletal remains. We report incontrovertible ichnofossil evidence for brackish-water habitat use by at least two mammalian species in southern Wyoming during the late Paleocene (58 Ma). These are the first Paleocene mammal trackways...

Evidence for the earliest invasion of the marine realm by mammals was previously restricted to Eocene (48.6-37.8 Ma) skeletal remains. We report incontrovertible ichnofossil evidence for brackish-water habitat use by at least two mammalian species in southern Wyoming during the late Paleocene (58 Ma). These are the first Paleocene mammal trackways...

Combined ichnological and sedimentological investigation of two major transgressions of the Paleocene Western Interior Sea in south-central Wyoming with implications for regional paleogeography.

Based on the presence of mineable coal beds, channelform sandstone bodies, freshwater mollusks, terrestrial pollen, and leaf fossils, the latest Cretaceous-Paleogene (~66-62 Ma) Ferris Formation (FF) in southern Wyoming's Hanna Basin (HB) was interpreted to be entirely nonmarine since its initial description in 1918. In the 1990s, sedimentary struc...

The Paleocene-Eocene Thermal Maximum (PETM) has been linked to generation of basin-wide fluvial sheet sand deposits in the Piceance, Uinta, Bighorn, and South-Pyrenean basins. Extrapolating to other basins with siliciclastic fluvial input, it could reasonably be expected that decreased precipitation and increased seasonality would lead to the devel...

Continental-scale drainages host the world's largest rivers and offshore sediment accumulations, many of which contain significant petroleum reserves. Rate of sediment supply in these settings may be a signal of external controls (e.g., tectonics) on landscape evolution, yet deciphering these controls remains a major challenge in interpreting the a...

Five cores through the Joanne and Judy Sandstone members of the Ladinian–Carnian Skagerrak Formation in the Central North Sea contain moderately to well-developed paleosols and associated continental ichnofossil assemblages. Usually considered to represent a classic dryland fluvial depositional setting, the presence of abundant rhizocretions, rhizo...

In late September, 2012, after 1 year of drought and little to no freshwater runoff in the Trinity River basin, saltwater incursion 10.7 km upstream from the mouth of the modern Trinity River made the Wallisville distributary channel 9 ppt, and delta front of the Trinity River bay head delta 12–15 ppt. Small- to medium-sized Ocypode (ghost crabs) w...

Salinity in Galveston Bay is greatest during the summer months, when runoff from the Trinity and San Jacinto rivers is at a minimum, and the inner bay reaches 15-20 ppt while the outer bay, including the back-barrier landward of the barrier island, achieves 20-25 ppt. Fresh water influx during flooding of the Trinity River overwhelms the bay and cr...

Current interpretations of fluvial avulsion style and architecture are largely model-driven and based on experimental tanks and computer simulations. Cretaceous and Paleocene strata of the Hanna Basin have been used to support these models and comprise a large data set (ca. 4,000 m thick and ~60 km of outcrop belt around the basin margins). Climate...

Outcrop-based models of amalgamated channel belts preserved in the Upper Triassic Chinle Formation in the vicinity of Moab, Utah comprise two primary architectural elements: an upper 4-14 m thick, trough cross-stratified, coarse-to fine-grained sand arranged into accretionary barforms, and lower 5-20 m tall, heterolithic macroforms composed of alte...

1. Introduction Numerous studies have demonstrated the utility of continental ichnology in delineating differences in paleohydrology and depositional environments over time and across local areas (Ratcliffe and Fagerstrom, 1980; Hastiotis, 2002; Buatois and Mángano, 2004; Demko et al., 2004; Smith et al., 2008; Krapovickas, 2010). At basin (explora...

Analysis of sand-body distribution reveals that fluvial channel sands in the Upper Cretaceous lower Williams Fork Formation in the central Piceance Basin, Colorado, USA, are not randomly distributed but are predictable in their spatial and stratigraphic position. Sand bodies are organized in channel-belt clusters that are compensationally stacked o...

Depositional Environments and Ichnofossils of the Sundance Formation at Glendo Reservoir, Eastern Wyoming, USA The Sundance Formation is an important hydrocarbon reservoir throughout Wyoming, but there is little consensus as to the origin of the thick sands that comprise the reservoir facies. Over 2.5 km of reasonably well exposed, Upper Jurassic s...

Road log and photos for field excursion to look at Cretaceous through Eocene clastic basin fill in the deepest Laramide Basin in the Rockies.

Large-diameter (2-10 cm) crustacean burrows preserved in the latest Cretaceous and early Paleocene estuarine barforms of southern Wyoming's Ferris Formation exhibit simple, noubranching architecture, elliptical cross sections, J- and U-shaped shaft morphologies, and walking-leg impressions along the burrow walls. The burrows are classified as Psilo...

Oxygen-deficient waters at the bathyal depths of the Santa Cruz Basin in the California Continental Borderland create harsh conditions for marine life. A feeding strategy approach is used for descriptions of the life habits (i.e., the organism’s motility and its living position with respect to the substrate) of benthic fauna and is intended to prov...

The Saint Peter Sandstone is a well-sorted, almost pure quartz arenite deposited during a major mid-Ordovician lowstand. Clastics prograded basinward across a subaerially exposed carbonate platform via eolian transport, as evidenced by the well-rounded, frosted texture of the quartz grains. The Starved Rock Member of the Saint Peter Sandstone is pr...

Historically, sandy paleochannel deposits of the 2,000 m- thick Ferris (Maastrichtian–Danian: 66–62 Ma) and overlying 3,000 m-thick Hanna Formation (Danian–Thanetian: 62–55 Ma) in southern Wyoming's Hanna and Carbon basins have been interpreted as fluvial channel fills. New selachian paleofaunas from both formations are concentrated in stratigraphi...

Despite an extensive described fossil record of Galliformes (Aves: ‘landfowl’), very few specimens have been considered within a phylogenetic context. Here we present a cladistic analysis and description of a new, well-preserved and well-dated fossil specimen from the Middle Eocene Bridger Formation of Wyoming (c. 50 Ma). Amitabha urbsinterdictensi...

A new model based on detailed lithostratigraphic and ichnological analysis of Upper Maastrichtian strata from southern North Dakota to southern Wyoming has emerged to provide a regional perspective on the paleogeographic evolution of the western margin of the Western Interior Sea during the final 5 m.y. of the Cretaceous. The distribution and inter...

Conventional models of valley incision in tectonically active basins depict fluvial incision and base level (sea level) fall as a paired process-response. Sequence boundaries are considered to be markers of episodes of tectonic uplift and/or lowered base level accompanied by a basinward migration of shoreline position. The Hanna Basin of southern W...

A common belief among paleontologists and biostratigraphers of the past century was that morphological complexity increased over time, leading to the rational that plesiomorphic taxa came from older strata. A prime example of the application of this generality toward resolving chronostratigraphic uncertainty is the use of continental vertebrates (p...

Extinction scenarios concerning non-avian dinosaurs across the Cretaceous-Tertiary boundary have been polarized into two groups: 1) catastrophic extinction in which healthy ecosystems are almost instantly destroyed; and 2) gradualist extinction in which long-term (10 m.y.) "declines" in taxonomic diversity are noted before the final K-T event. Clea...

Laramide depositional basins in Wyoming were marine-dominated throughout most of the Campanian (80-72 Ma), with newly established fluvial drainage systems providing sediment to growing delta and coastal plains, as well as barrier islands, channel mouth bars, and shorefaces. During the latest Cretaceous (Maastrichtian: 68-65) and Paleocene (Danian-S...

Sandbody Variability and Classification in the Ferris and Hanna Formations (Maastrichtian-Danian): Implications for Timing of Retreat of the Western Interior Sea Sandstone bodies within the Ferris (ca. 66-63 Ma) and Hanna (ca. 62-55 Ma) formations in Wyoming's Hanna and Carbon basins have been described as braided and/or meandering fluvial channel...

Depositional History Of Paleocene Foreland Basin Strata, Southern Wyoming Paleocene strata (Hanna Formation) of southern Wyoming's Hanna and Carbon basins represent basinward progradation of two separate clastic wedges. The older of the two wedges represents an ~1,000 m thick, as yet unnamed member of the Hanna Formation and is differentiated from...

Stratigraphy, Sedimentology, and Paleontology of the Hell Creek Formation (Maastrichtian) Bowman County, North Dakota The Hell Creek Formation (Lancian: ~67-65 Ma) on the eastern flank of the Cedar Creek Anticline, southwestern North Dakota, provides an opportunity to study the latest Cretaceous sedimentary history of this area. In this area, the l...

Basal strata of the Hanna Formation (?middle Torrejonian-early Wasatchian) in the central Hanna Basin of south-central Wyoming form a series of amalgamated sandstone sheets, known locally northwest of the town of Hanna as Sand Ridge. Sand Ridge is laterally traceable for approximately 10 km before it pinches out to the west and the southeast. At it...