RECOGNITION OF PARASEQUENCES IN THE MARINE WOODHAWK MEMBER OF THE UPPER CRETACEOUS (CAMPANIAN) JUDITH RIVER FORMATION, MONTANA

2019 ◽  
Author(s):  
Sintra M. Reves-Sohn ◽  
◽  
Joseph A. Baldus ◽  
Raymond R. Rogers
Keyword(s):  
Upper Cretaceous ◽  
Judith River Formation

Isotaphonomy in concept and practice: an exploration of vertebrate microfossil bonebeds in the Upper Cretaceous (Campanian) Judith River Formation, north-central Montana

Paleobiology ◽  
2017 ◽  
Vol 43 (2) ◽  
pp. 248-273 ◽  
Author(s):  
Raymond R. Rogers ◽  
Matthew T. Carrano ◽  
Kristina A. Curry Rogers ◽  
Magaly Perez ◽  
Anik K. Regan
Keyword(s):  
Upper Cretaceous ◽  
Statistical Tests ◽  
Sampling Strategies ◽  
North Central ◽  
Wetland Ecosystems ◽  
Future Studies ◽  
Size And Shape ◽  
Definition Of ◽  
Central Montana ◽  
Judith River Formation

AbstractVertebrate microfossil bonebeds (VMBs)—localized concentrations of small resilient vertebrate hard parts—are commonly studied to recover otherwise rarely found small-bodied taxa, and to document relative taxonomic abundance and species richness in ancient vertebrate communities. Analyses of taphonomic comparability among VMBs have often found significant differences in size and shape distributions, and thus considered them to be non-isotaphonomic. Such outcomes of “strict” statistical tests of isotaphonomy suggest discouraging limits on the potential for broad, comparative paleoecological reconstruction using VMBs. Yet it is not surprising that sensitive statistical tests highlight variations among VMB sites, especially given the general lack of clarity with regard to the definition of “strict” isotaphonomic comparability. We rigorously sampled and compared six VMB localities representing two distinct paleoenvironments (channel and pond/lake) of the Upper Cretaceous Judith River Formation to evaluate biases related to sampling strategies and depositional context. Few defining distinctions in bioclast size and shape are evident in surface collections, and most site-to-site comparisons of sieved collections are indistinguishable (p≤0.003). These results provide a strong case for taphonomic equivalence among the majority of Judith River VMBs, and bode well for future studies of paleoecology, particularly in relation to investigations of faunal membership and community structure in Late Cretaceous wetland ecosystems. The taphonomic comparability of pond/lake and channel-hosted VMBs in the Judith River Formation is also consistent with a formative model that contends that channel-hosted VMBs were reworked from pre-existing pond/lake assemblages, and thus share taphonomic history.

The Denholm landslide, Saskatchewan. Part I: Geology

1983 ◽  
Vol 20 (2) ◽  
pp. 197-207 ◽  
Author(s):  
E. A. Christiansen
Keyword(s):  
Shear Zone ◽  
Radiocarbon Dating ◽  
Upper Cretaceous ◽  
Average Rate ◽  
Surface Expression ◽  
Recent Time ◽  
Displacement Rate ◽  
The North ◽  
Colorado Group ◽  
Judith River Formation

The Denholm landslide, whose surface is composed of scarps, ridges, and elongated depressions, is 160 m high, 2000 m wide, and up to 100 m thick. The shear zone is in silty, montomorillonitic clay of the upper part of the Lea Park Formation and Upper Colorado Group unit. The Upper Cretaceous Judith River Formation and the Quaternary Empress, Sutherland, and Saskatoon groups were affected by the landslide. Although these sediments were fractured and gravity faulted by tension when the landslide moved, they can be readily traced through the landslide, particularly the upper part. The scarps (gravity faults), ridges (horsts), and elongated depressions (grabens) are the surface expression of tension resulting from the stretching of beds during the landslide.The movement of the landslide is thought to have started when the North Saskatchewan spillway eroded to the level of the present shear zone about 11 000 years ago (established by radiocarbon dating) and is believed to have stopped in recent time. During this time, it moved about 390 m across the North Saskatchewan River alluvium at an average rate of 35 mm per year. As the landslide moved across the valley, it encountered deposition of alluvium at an average rate of about 2.4 mm per year which resulted in the curved shear zone on the alluvium. Keywords: retrogressive landslide, shale-alluvium, displacement, rate, age.

scholarly journals Spiclypeus shipporum gen. et sp. nov., a Boldly Audacious New Chasmosaurine Ceratopsid (Dinosauria: Ornithischia) from the Judith River Formation (Upper Cretaceous: Campanian) of Montana, USA

PLoS ONE ◽  
2016 ◽  
Vol 11 (5) ◽  
pp. e0154218 ◽  
Author(s):  
Jordan C. Mallon ◽  
Christopher J. Ott ◽  
Peter L. Larson ◽  
Edward M. Iuliano ◽  
David C. Evans
Keyword(s):  
Upper Cretaceous ◽  
Judith River Formation

The Petrofka landslide, Saskatchewan

1987 ◽  
Vol 24 (1) ◽  
pp. 81-99 ◽  
Author(s):  
B. F. Eckel ◽  
E. Karl Sauer ◽  
E. A. Christiansen
Keyword(s):  
Factor Of Safety ◽  
Upper Cretaceous ◽  
Back Analysis ◽  
Hydraulic Head ◽  
Residual Shear Strength ◽  
Historical Simulation ◽  
Pore Water Pressures ◽  
Artesian Aquifer ◽  
Effective Angle ◽  
Judith River Formation

Both abutments and all piers of the Petrofka bridge are on a landslide. The bridge has performed satisfactorily for 23 years, indicating the factor of safety of the Petrofka landslide is greater than unity. This stability is abnormal because landslide slopes on bedrock clays (shale) in this region are notoriously unstable. A dormant landslide is difficult to analyze because the input parameters must represent a condition of limiting equilibrium.The Petrofka landslide is 70 m high, 880 m long, 3000 m wide, and up to 100 m thick. The shear zone is in highly plastic, montmorillonitic clays in an unnamed formation of probable Tertiary age. The Upper Cretaceous Lea Park, Judith River, and Bearpaw formations and the unnamed formation underly the landslide and are restricted to a collapse structure resulting from dissolution of Devonian evaporites.A retrogressive mechanism developed as valley downcutting progressed. The pore-water pressures could be estimated from the hydraulic head in the artesian aquifer of the Judith River Formation. The hydraulic head was maintained at critical as the valley deepened until the Judith River Formation was eroded downstream. The landslide was active for only a few hundred years, between 11 500 and 11 000 years ago.The back-calculated effective angle of friction for the bedrock clay (shale) was estimated at between 5.6° and 6.5°, assuming c′ = 0, resulting in a present-day factor of safety between 1.2 and 1.3. Key words: back analysis, dormant landslide, collapse structure, artesian pressure, historical simulation, residual shear strength.

New data on pachycephalosaurid dinosaurs (Reptilia: Ornithischia) from North America

1983 ◽  
Vol 20 (3) ◽  
pp. 462-472 ◽  
Author(s):  
Peter M. Galton ◽  
Hans-Dieter Sues
Keyword(s):  
United States ◽  
North America ◽  
Upper Cretaceous ◽  
New Genus ◽  
Biological Significance ◽  
The United States ◽  
Hell Creek Formation ◽  
Unusual Condition ◽  
Judith River Formation

In this paper several new significant specimens of pachycephalosaurid dinosaurs from Upper Cretaceous strata of Canada and the United States are described and figured. The domes of an unusual pachycephalosaurid from the Judith River Formation (Campanian) of Alberta show a slightly thickened frontal with an ornamentation of bony tubercles; they are referred to a new genus. A new genus of Pachycephalosauridae is described from the Hell Creek Formation (Maestrichtian) of Montana; it has horn-like projections on the squamosal. Sutural fusion between the quadrate and squamosal of Pachycephalosaurus is reported; this is an unusual condition among the Ornithischia. The biological significance of certain cranial features is considered.

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