Evidence for fluvial-controlled coal deposition in the upper Tongue River Member (Fort Union Formation, Paleocene) Powder River Basin, Wyoming.

摘要

Recent exploration in the Powder River basin has targeted shallow, coal-bed methane, and basin reserves may be as high as 39 trillion cubic feet. This study had a threefold purpose: (1) establish a regional stratigraphic framework for the upper Tongue River Member of the Fort Union Formation including major coals beds and interbedded sandstones; (2) evaluate stratigraphic evidence as it relates to either the fluvial or deltaic model for the deposition of coal in the Tongue River Member; and (3) determine the controlling factors for the development of shallow folds and potential gas reservoirs.; Nearly 1,700 well logs from an area located along the northern Wyoming border were used in this study. Twelve regional stratigraphic cross sections were constructed to provide a framework for a detailed correlation of the upper Tongue River coals. Upon completion of the correlation, the picks were entered into a spatial database. This database was used to create coal-structure, coal-isolith, coal-isopach, and clastic-sediment isopach maps. Information collected from these four general types of maps was used to create paleogeographic maps. (Abstract shortened by UMI.)