Blackhawk
Description
Source: Wikipédia
The Blackhawk Formation is a geological formation in east-central Utah, United States. It was named for the former town of Blackhawk on the east side of the Wastach Plateau, Carbon County. The formation is composed of mostly light-brown, light-gray and brownish-gray, thin- to medium-bedded, fine- to medium-grained quartzose sandstone that is interbedded with shaly siltstone, shale, carbonaceous shale, and coal. There are many thin to thick bituminous coal seams, including several economically important beds, such as the Sunnyside Coal. The formation thickness ranges from about 120 m (400 ft) to about 270 m (900 ft). It conformably overlies the Star Point Sandstone and unconformably underlies the Castlegate Sandstone.
The sediments that formed the Blackhawk Formation originated from erosion of the Sevier Uplift in western Utah. This sediment was transported eastwards by rivers and deposited on the western coast of the Cretaceous Seaway. At this time, the Seaway was also withdrawing (regression) eastwards, but this was irregular, with occasional episodes of the sea advancing (transgression) to cover coastal lands. This transgression was partially as a result of fluctuating (eustatic) global sea level changes and partly as a result of the shift position of the deltas. These events created wedges of terrestrial sedimentary rock between wedges of marine sedimentary rock (Mancos Shale). These wedges of the Blackhawk Formation have been given names and many of them contain economically important bituminous coal zones, such as the Kenilworth Coal that is up to 11 m (37 feet) thick. The coast probably resembled the Gulf Coast today, being composed of a broad coastal plain, with meandering rivers that ended in wave-dominated deltas. These deltas were flanked by sandy beaches. Swamps were probably developed on the delta plains and on the floodplain (bottomlands) adjacent to the meandering rivers, rather than in brackish-water of lagoons because of the low sulfur content of the coals.
Découvertes
Source: The Paleobiology Database
Site(s) correspondant(s) à cette formation: 1
Spring Canyon tracksite : Utah - Carbon Publication(s)
La base comprend 7 publication(s).
Source: The Paleobiology Database
- ↑1 2 L. R. Parker. 1983. The identity of coalified wood from coal mine roofs in the Upper Cretaceous Blackhawk Formation of Utah. Geological Society of America, Rocky Mountain Section, Abstracts with Programs 15(5):408
- ↑1 M. G. Lockley. 1994. Dinosaur ontogeny and population structure: Interpretations and speculation based on fossil footprints . Dinosaur eggs and babies
- ↑1 R. T. McCrea, M. G. Lockley, and C. A. Meyer. 2001. Global distribution of purported ankylosaur track occurrences. The Armored Dinosaurs, K. Carpenter (ed.), Indiana University Press, Bloomington
- ↑1 L. R. Parker and R. L. Rowley. 1989. Dinosaur footprints from a coal mine in east-central Utah. In D. D. Gillette and M. G. Lockley (eds.), Dinosaur Tracks and Traces. Cambridge Univeristy Press, Cambridge
- ↑1 M. Lockley, T. J. Logue, and J. J. Moratalla, A. P. Hunt, R. J. Schultz, J. W. Robinson. 1995. The fossil trackway Pteraichnus is pterosaurian, not crocodilian: implications for the global distribution of pterosaur tracks. Ichnos 4:7-20 (https://doi.org/10.1080/10420949509380110)
- ↑1 P. J. Currie, G. C. Nadon, and M. G. Lockley. 1991. Dinosaur footprints with skin impressions from the Cretaceous of Alberta and Colorado. Canadian Journal of Earth Sciences 28:102-115 (https://doi.org/10.1139/e91-009)
- ↑1 M. G. Lockley and A. P. Hunt. 1995. Dinosaur Tracks and Other Fossil Footprints of the Western United States (https://doi.org/10.1093/amt/20.1.305)