Arapahoe
Description
Source: Wikipédia
The Arapahoe Formation is a geological formation of latest Cretaceous (Maastrichtian) age that is present within the Denver Basin that underlies the Denver, Colorado, area. The formation includes fossil leaves and dinosaur remains, although none of the latter have yet been referred to a specific genus. It also includes aquifers that are important sources of water for the area.
The Arapahoe Formation consists of alluvial fan and fluvial deposits that prograded eastward from the growing Rocky Mountain Front Ranges. It rests unconformably on the Laramie Formation, and is conformably overlain by the Denver Formation. It reaches a maximum thickness of about 300 ft (91 m).
The base of the Arapahoe Formation is marked by a discontinuous conglomerate, or where the conglomerate is absent, by sandstone beds that commonly contain large ironstone concretions. The conglomerate is composed principally of chert pebbles, but pebbles of granite, gneiss and schist are also present. Medium grey to brown claystone makes up the majority of the formation, with lesser amounts of light grey to light brown quartzose sandstone. The formation top is marked by a change from sandstone and claystone to the tuffaceous sediments of the overlying Denver Formation.
In 2002 the Arapahoe Formation was included as part of a larger unconformity-bounded unit named the D1 Sequence, in order to facilitate basin-wide studies and avoid confusion arising from the lateral and vertical facies changes that occur within the Denver Basin. The base of the D1 coincides with the base of the Arapahoe Formation and is marked by the abrupt change to conglomerate at the top of the Laramie Formation. The top D1 is placed at the base of a regional paleosol series. The Denver Formation and the Dawson Arkose are also included in the D1 Sequence.
Découvertes
Source: The Paleobiology Database
Site(s) correspondant(s) à cette formation: 5
Brighton area, Henderson (1) : Colorado - Adams 7835 12314 13266 53400 55599 59351 78169 Brighton area, near Henderson- Ceratopsidae identifié comme Triceratops galeus n. sp.
- Brighton area, Henderson (2) : Colorado - Adams 13266 Brighton area, near Henderson
- 12th Street tracksite (lower) : Colorado - Jefferson 13266 29242 63566 80662 in CSM clay pits, N of 19th St and E of 6th Avenue (prob. Rte 6); on wall facing W toward 6
- Hoff-Schroeder (DMNH Loc. 1087) : Colorado - Adams 13266
- 12th Street clay pits, Golden : Colorado - Adams 53400 from the 12th St. clay pits, Golden
Publication(s)
La base comprend 10 publication(s).
Source: The Paleobiology Database
- ↑1 2 O. C. Marsh. 1889. Notice of gigantic horned Dinosauria from the Cretaceous. American Journal of Science 38:173-175 (https://doi.org/10.2475/ajs.s3-38.224.173)
- ↑1 R. S. Lull. 1933. A revision of the Ceratopsia or horned dinosaurs. Memoirs of the Peabody Museum of Natural History 3(3):1-175 (https://doi.org/10.5962/bhl.title.5716)
- ↑1 2 3 4 5 6 K. Carpenter and D. B. Young. 2002. Late Cretaceous dinosaurs from the Denver Basin, Colorado. Rocky Mountain Geology 37(2):237-254 (https://doi.org/10.2113/11)
- ↑1 2 3 J. H. Johnson. 1931. The paleontology of the Denver quadrangle, Colorado. Colorado Scientific Society, Proceedings 12(11):355-378
- ↑1 J. H. Ostrom and P. Wellnhofer. 1986. The Munich specimen of Triceratops with a revision of the genus. Zitteliana 14:111-158
- ↑1 T. M. Lehman. 1987. Late Maastrichtian paleoenvironments and dinosaur biogeography in the Western Interior of North America. Palaeogeography, Palaeoclimatology, Palaeoecology 60:189-217 (https://doi.org/10.1016/0031-0182(87)90032-0)
- ↑1 O. C. Marsh. 1897. Vertebrate fossils of the Denver Basin. United States Geological Survey Monograph 27:473-527
- ↑1 2 M. G. Lockley. 1986. A Guide to Dinosaur Tracksites of the Colorado Plateau and American Southwest. University of Colorado at Denver Geology Department Magazine, Special Issue 1:1-56
- ↑1 M. G. Lockley and A. P. Hunt. 1995. Ceratopsid tracks and associated ichnofauna from the Laramie Formation (Upper Cretaceous: Maastrichtian) of Colorado. Journal of Vertebrate Paleontology 15(3):592-614 (https://doi.org/10.1080/02724634.1995.10011251)
- ↑1 J. Wright and M. G. Lockley. 2001. Dinosaur and turtle tracks from the Laramie/Arapahoe formations (Upper Cretaceous), near Denver, Colorado, USA. Cretaceous Research 22:365-376 (https://doi.org/10.1006/cres.2001.0262)