Colorado ,
22-582: The Cloverly Formation is a geological formation of Early and Late Cretaceous age ( Valanginian to Cenomanian stage) that is present in parts of Montana , Wyoming , Colorado and Utah in the western United States. It was named for a post office on the eastern side of the Bighorn Basin in Wyoming by N.H. Darton in 1904. The sedimentary rocks of formation were deposited in floodplain environments and contain vertebrate fossils , including
44-849: A diverse assemblage of dinosaur remains. In 1973, the Cloverly Formation Site was designated as a National Natural Landmark by the National Park Service. The Cloverly Formation rests disconformably on the Morrison Formation and is conformably overlain by the Thermopolis Shale . It is subdivided into a variety of members, depending on the location. In the Bighorn Basin along the Montana-Wyoming border, Moberly (1960) divided
66-611: A geologic formation goes back to the beginnings of modern scientific geology. The term was used by Abraham Gottlob Werner in his theory of the origin of the Earth, which was developed over the period from 1774 to his death in 1817. The concept became increasingly formalized over time and is now codified in such works as the North American Stratigraphic Code and its counterparts in other regions. Geologic maps showing where various formations are exposed at
88-542: A newly designated formation could not be named the Kaibab Formation, since the Kaibab Limestone is already established as a formation name. The first use of a name has precedence over all others, as does the first name applied to a particular formation. As with other stratigraphic units, the formal designation of a formation includes a stratotype which is usually a type section . A type section
110-549: A permanent natural or artificial feature of the geographic area in which they were first described. The name consists of the geographic name plus either "Formation" or a descriptive name. Examples include the Morrison Formation , named for the town of Morrison, Colorado , and the Kaibab Limestone , named after the Kaibab Plateau of Arizona. The names must not duplicate previous formation names, so, for example,
132-806: A predator-prey relationship between the two. Microvenator M. celer Its remains are "extremely rare." Known only from a "[p]artial skeleton with partial skull." The specimen lacks feet and is catalogued as AMNH 3041. The type specimen AMNH 3041 was recovered by Barnum Brown from Cloverly strata in Montana in 1933 . Ornithomimus O. velox Later found to be indeterminate ornithomimid remains. Astroconodon A. sp. cf. Atokatheridium Bryceomys B. sp. Corviconodon C. montanensis Gobiconodon G. ostromi Janumys J. sp. Montanalestes M. keeblerorum cf. Oklatheridium Formation (geology) A geological formation , or simply formation ,
154-449: Is not a valid lithological basis for defining a formation. The contrast in lithology between formations required to justify their establishment varies with the complexity of the geology of a region. Formations must be able to be delineated at the scale of geologic mapping normally practiced in the region; the thickness of formations may range from less than a meter to several thousand meters. Geologic formations are typically named after
176-412: Is a body of rock having a consistent set of physical characteristics ( lithology ) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exposed in a geographical region (the stratigraphic column ). It is the fundamental unit of lithostratigraphy , the study of strata or rock layers. A formation must be large enough that it can be mapped at
198-434: Is also used informally to describe the odd shapes (forms) that rocks acquire through erosional or depositional processes. Such a formation is abandoned when it is no longer affected by the geologic agent that produced it. Some well-known cave formations include stalactites and stalagmites . Rugocaudia Rugocaudia is a potentially dubious genus of basal titanosauriform sauropod dinosaur known from
220-560: Is central to the geologic discipline of stratigraphy , and the formation is the fundamental unit of stratigraphy. Formations may be combined into groups of strata or divided into members . Members differ from formations in that they need not be mappable at the same scale as formations, though they must be lithologically distinctive where present. The definition and recognition of formations allow geologists to correlate geologic strata across wide distances between outcrops and exposures of rock strata . Formations were at first described as
242-455: Is ideally a good exposure of the formation that shows its entire thickness. If the formation is nowhere entirely exposed, or if it shows considerably lateral variation, additional reference sections may be defined. Long-established formations dating to before the modern codification of stratigraphy, or which lack tabular form (such as volcanic formations), may substitute a type locality for a type section as their stratotype. The geologist defining
SECTION 10
#1732790074135264-641: The Early Cretaceous of Montana , United States. Rugocaudia is known only from the holotype MOR 334, a partial postcranial skeleton which consist of 18 caudal vertebrae and associated material including isolated neural arch , tooth , chevron , and distal section of a metacarpal . It was collected from the Cloverly Formation , dating to the Aptian or the Albian stage of
286-407: The Early Cretaceous . Rugocaudia is considered to be a nomen dubium by D'Emic and Foreman. Rugocaudia was first described and named by D. Cary Woodruff in 2012 and the type species is Rugocaudia cooneyi . The generic name is deriverd from Latin ruga , "wrinkle" and cauda , "tail" in regards to the highly rugose posterior margins of the caudal vertebrae. The specific name honors
308-812: The Cloverly into the following three members: In contrast, Ostrom (1970) divided the formation into four units, which he named Units IV-VII: A stratigraphic revision of the Cloverly Formation using new uranium lead dates reinterpret the formation as spanning the Valanginian-Cenomanian stages of the Cretaceous period. The individual ages of the members are listed below: The sediments of the Cloverly Formation were deposited in alluvial and floodplain environments. The basal conglomerates probably represent braided river deposits, while
330-550: The essential geologic time markers, based on their relative ages and the law of superposition . The divisions of the geological time scale were described and put in chronological order by the geologists and stratigraphers of the 18th and 19th centuries. Geologic formations can be usefully defined for sedimentary rock layers, low-grade metamorphic rocks , and volcanic rocks . Intrusive igneous rocks and highly metamorphosed rocks are generally not considered to be formations, but are described instead as lithodemes . "Formation"
352-522: The formation is expected to describe the stratotype in sufficient detail that other geologists can unequivocally recognize the formation. Although formations should not be defined by any criteria other than primary lithology, it is often useful to define biostratigraphic units on paleontological criteria, chronostratigraphic units on the age of the rocks, and chemostratigraphic units on geochemical criteria, and these are included in stratigraphic codes. The concept of formally defined layers or strata
374-469: The formation. Remains identified by John Ostrom as Ornithomimus are suspected by Jack Horner to be of a new ornithomimid genus. Possible remains of a microraptorian, a troodontid, and a basal tyrannosauroid similar to Moros have also been found here as well. Rugocaudia R. cooneyi Deinonychus D. antirrhopus Its remains are "very rare." Tenontosaurus remains have been recovered in association with Deinonychus teeth, suggesting
396-594: The lungfish Ceratodus . Dinosaur eggs have been found in Montana. References for data: Ostrom 1970; Cifelli et al. 1998; Cifelli 1999; Nydam and Cifelli 2002. Possible goniopholidid remains are known from the formation. Sauropelta S. edwardsorum Known from "several articulated skeletons" and common armor plates. Only one partial skull is known. Articulated skeletons are often encased in carbonate caliche deposits that require acid to be removed safely. Aquilops A. americanus A basal neoceratopsian . Tenontosaurus T. tilleti Its remains are
418-554: The most common of any dinosaur of the formation. Juvenile remains are sometimes found together, suggesting that young Tenontosaurus lived in sibling groups. Deinonychus teeth are sometimes associated with Tenontosaurus , suggesting a predator-prey relationship between the two. Zephyrosaurus Z. schaffi Its remains are "very rare." Theropod eggshell fragments are known from the formation. Unidentifiable ornithomimid remains are present and most commonly represented by toe bones. Indeterminate allosauroid remains are known from
440-444: The sandstones were deposited in fluvial channels. The mudstones that contain most of the fossils represent overbank , lacustrine , and pedogenic deposits. Animals recovered include the dinosaurs Deinonychus , Microvenator , Tenontosaurus , Zephyrosaurus and Sauropelta as well as fragmentary remains of Titanosaurs , Ankylosaurs and Ornithomimids. As well, two genera of turtle Naomichelys and Glyptops and
462-643: The surface are fundamental to such fields as structural geology , allowing geologists to infer the tectonic history of a region or predict likely locations for buried mineral resources. The boundaries of a formation are chosen to give it the greatest practical lithological consistency. Formations should not be defined by any criteria other than lithology. The lithology of a formation includes characteristics such as chemical and mineralogical composition, texture, color, primary depositional structures , fossils regarded as rock-forming particles, or other organic materials such as coal or kerogen . The taxonomy of fossils
SECTION 20
#1732790074135484-432: The surface or traced in the subsurface. Formations are otherwise not defined by the thickness of their rock strata, which can vary widely. They are usually, but not universally, tabular in form. They may consist of a single lithology (rock type), or of alternating beds of two or more lithologies, or even a heterogeneous mixture of lithologies, so long as this distinguishes them from adjacent bodies of rock. The concept of
#134865