In 1907, Barnum Brown named the Hell Creek beds (Formation) for the strata exposed in the Hell Creek Valley and other downstream tributaries of the Missouri River. In the absence of a stratotype section, a lectostratotype is herein proposed for the Hell Creek Formation based on 84.2-m-thick exposures at Flag Butte (local name) in Ried Coulee (archaic use; East Fork of Hell Creek) and East Ried Coulee, tributaries of Hell Creek, Garfield County, Montana (sec. 29, T. 21 N., R. 38 W., NAD27 CONUS; base 47.55931°N, 106.88111°W; top 47.55533°N, 106.86810°W). The formation is underlain with general conformity by sandstone beds of the Fox Hills Formation (as characteristically known, the Colgate Member is absent) and is for the most part conformably overlain locally by the Tullock Member of the Fort Union Formation. The upper contact at Flag Butte is demarcated at the base of the IrZ lignite bed (above an iridium anomaly). The boundary has been demonstrated to be somewhat unconformable in areas to the west. The IrZ bed is also missing at Bug Creek in McCone County. In its type section, the Hell Creek Formation is subdivided (simply and informally) into Ried Coulee (lower Hell Creek), East Ried Coulee (middle Hell Creek), and Flag Butte (upper Hell Creek) units, each containing a sandstone and a mudstone lithofacies. Formational thickness varies with local depositional and erosional history of various coastal-deltaic environments across the Williston Basin and a trend of overall thinning to the east and northeast.

Abstract Paleontological resources (fossils) are the remains of life preserved in a geologic context. Fossils may consist of the physical remains of a biological organism such as a tooth, bone, shell, leaf, cone, seed, or wood. Evidence of biological activity may sometimes be preserved in rocks, hence tracks, traces, burrows, coprolites (fossil dung and feces), and nests represent other valuable types of paleontological resources. The fossil record reveals an extremely rich diversity of ancient organisms preserved in the Earth's strata (layers of rock). The fossil record of life on Earth spans nearly every period of geologic history from Precambrian bacteria, billions of years old, to more recent Pleistocene or Holocene cave fossils dating back only a few thousand years. Together, fossils from around the world yield significant scientific and educational information regarding the history of life on Earth. From the moment of death for an organism, a wide array of agents and forces work toward the breakdown and destruction of its physical remains. Raup and Stanley (1978) identify and describe biological, chemical, and mechanical variables associated with the destruction of biological remains. Only a very small percentage of all living organisms become part of the fossil record, and of those, an even smaller percentage have been discovered, collected and studied. The preservation of fossils and the associated biases in the fossil record are directly attributable to the organism's morphologic composition, rate of post-mortem burial, environment of deposition, diagenetic variables, tapho-nomic (after death) factors, and the post-depositional geologic history of

Abstract The Powder River Basin of northeast Wyoming and southeast Montana contains coal resources larger than those of any other basin of comparable size in the United States. These coal resources are developed in 16 strip mines for coal-fired power plants and for coalbed methane in more than 20,000 wells for distribution throughout the country. During this field trip, strip mining methodology and technology at the Wyodak coal mine, and operations at the nearby Wyodak power plant and in coalbed methane fields will be observed and discussed. The power plant utilizes feed coal from the mine and supplies electricity for the City of Gillette and surrounding areas. Coalbed methane development in the basin has coexisted with coal mining since the early 1980s. The same coal beds that are being mined yield gas in the subsurface, which is produced, collected, and moved to pipelines to access the interstate pipeline grid to serve the Rocky Mountains, Midwest, and California customers. Keywords: Powder River Basin, Wyoming, coal, coalbed methane, gas.

Abstract The 300-km-long Books Cliffs are a world-class field laboratory for studying clastic sedimentology, sedimentary architecture, and sequence stratigraphy, and serve as an outcrop analog for fluvio-deltaic and shoreface-to-shelf hydrocarbon reservoirs worldwide. These famous rocks have been used to develop, test and refine sedimentological and stratigraphic ideas and models over the years, including the principles and concepts of sequence stratigraphy. This field guide focuses on the following themes: (a) sedimentology, sedimentary architecture, and sequence stratigraphy of fluvial, coastal plain, river- and wave-dominated deltas, and shoreface-to-shelf deposits, (b) stacking patterns in high versus low accommodation settings, (c) distribution of reservoir and non-reservoir facies in a predictive sequence stratigraphic framework, (d) relationship between relative sea level, shoreline position, and stratigraphic architecture, and (e) alternative sequence stratigraphic models for the interpretation of channel-shoreface packages. Keywords: accommodation space, Book Cliffs, Cretaceous, deltaic, fluvial, sedimentaryarchitecture, sedimentology, sequence stratigraphy, shelf, shoreface, Western InteriorSeaway