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Basal gravel and sand mantling the bedrock floors of buried valleys throughout the Canadian Interior Plains, and conformably overlying proglacial lacustrine sediment, comprise the Empress Group. While previously conceptualized as stratigraphically equivalent deposits of preglacial rivers prior to the first and most extensive continental and montane glaciations, subsequent stratigraphic studies indicated that buried valley basal gravel must have been deposited between, or during, progressively more extensive continental glaciations and could not be stratigraphically equivalent throughout the buried valley network. However, in the general absence of formation-rank stratigraphic description of basal gravel units that might better inform the geologic history of the deposits, most workers simply consider Empress Group sediments time-transgressive. In this paper, we examine basal gravel at provincial and regional scales to understand its genesis and geologic history. At the provincial scale, we map basal gravel in three dimensions using a novel machine learning approach. At the regional scale, we formally define basal gravel formations at either end of the largest buried valley system in Alberta, which informs its glacial history and physiographic development and shows the importance of formation-rank stratigraphic description. Our results indicate that the buried valley network across Alberta is palimpsest in genesis and basal gravel units within it are chronostratigraphically intercalated between tills. We advocate that the Empress Group definition be extended across Alberta with modifications to improve its clarity and utility, and formally define the Old Fort, Unchaga, Ipiatik, and Winefred formations as part of the Empress Group. [ABSTRACT FROM AUTHOR]

The Eocene to Miocene Cypress Hills Formation (CHF) spans 28 million years and forms the conglomeratic caprock of the Cypress Hills and Swift Current plateaus in southwestern Saskatchewan and southeastern Alberta. These stacked fluvial, floodplain, and lacustrine deposits preserve the only high latitude, non-polar mammalian fossil assemblage (Uintan to Hemingfordian land mammal stages) in Canada. The Quarry is the oldest CHF (Chadronian 1, late Eocene) site documented in the Cypress Hills region north of the town of Eastend. The Quarry was originally discovered in 1962, after bones were found to be eroding out of the base of a road cut north of the ghost town of South Fork on the southeastern flanks of the Cypress Hills. Numerous field campaigns have resulted in the collection of fossils from a multitaxonomic bonebed. This paper presents a detailed sedimentologic, paleontologic, and taphonomic study to establish a depositional environment framework of the Southfork Quarry. This site was deposited at the onset of the Eocene–Oligocene climate transition, a critical time of climate change during the Paleogene. Six facies and two facies associations are characterized for the Quarry, shifting from a braided-fluvial system to a debris flow-filled incised channel. Patterns of skeletal accumulations and bone surface modification indicate that the assemblage accumulated over a significant interval of time in different depositional environments. This study provides critical insight into environmental shifts driven by climate change and relates these findings to a broader understanding of the Eocene–Oligocene transition in North America. [ABSTRACT FROM AUTHOR]

For sheer complexity, braincases are generally considered anatomically conservative. However, recent research on the braincases of tyrannosaurids have revealed extensive morphological variations. This line of inquiry has its root in Dale Russell's review of tyrannosaurids in which he established Daspletosaurus torosus — a large tyrannosaurine from the Campanian of southern Alberta. In the wake of systematic revisions to tyrannosaurines previously assigned to Daspletosaurus, one potentially distinct species remains undescribed. This paper describes and compares a braincase referable to this species with that of the holotype for Daspletosaurustorosus using computerized-tomography-based reconstructions. The two braincases have numerous differences externally and internally. The specimen of Daspletosaurus sp. has a bottlenecked olfactory tract, short and vertical lagena, and a developed ascending column of the anterior tympanic recess. The holotype of Daspletosaurus torosus has many unusual traits, including an anteriorly positioned trochlear root, elongate common carotid canal, distinct chamber of the basisphenoid recess, asymmetry in the internal basipterygoid aperture, and laterally reduced but medially expanded subcondylar recess. This comparison also identified characters that potentially unite the two species of Daspletosaurus, including deep midbrain flexures in the endocasts. However, many character variations in the braincases are known in other tyrannosaurids to correlate with body size and maturity, or represent individual variations. Therefore, taxonomic and phylogenetic signals can be isolated from background variations in a more comprehensive approach by using additional specimens. New information on the two braincases of Daspletosaurus is consistent with the emerging view of tyrannosaurid braincases as highly variable, ontogenetically dynamic character complexes. [ABSTRACT FROM AUTHOR]

Any process that causes a sudden brittle failure of material has the potential to cause earthquake-like seismic events. Cryoseisms represent an underreported class of seismic event due to their (often) small magnitudes. In this paper, we document the phenomenon of some of the largest magnitude lake-associated icequakes (ML 2.0) yet reported. These events occurred nearly simultaneously (within ∼2 h) on geographically separate lakes in Alberta, Canada, starting 1 January 2018. We conjecture that these events were caused by the sudden brittle failure of lake ice due to thermal expansion; the effects of the thermal expansion were compounded by the lack of insulating snow cover, high lake water levels, and a rapid onset of atmospheric warming. These factors also contributed to ice-jacking — a repeating process in which thermal contraction produces tensile cracks (leads) in lake ice that are then filled with water that is frozen during the cooling cycle. Thus, any subsequent thermal expansion must be accommodated by new deformation or brittle failure. This ice-jacking process caused creeping ground deformation after the initial brittle failure and again two weeks later following a second warming period. In many cases, the resulting ground deformation was significant enough to cause property damage. [ABSTRACT FROM AUTHOR]