A Preliminary Study of the Ostracoda of the Big Snowy Group, Mississippian, of Montana.

In the field, samples were taken vertically and horizon­tally along the various outcrops in different sections of central and south-central Montana. At important localities the samples were taken about every half-foot verti­cally; in other sections they were taken every few feet.

Upper Mississippian Faunas of Western Montana

The author has made a study of an assemblage of fossils from the Blacktail Range near Dillon Montana with the purpose in view of attempting a correlation of that group with the fauna of the Big Snowy Group. Fossils have also been obtained from a limestone formation in northwestern Montana and from four different areas in the Amsden formation in central and western Mont­ana.

Insoluble Residues of the Lower Mississippian Limestones of the Madison Group

The correlation of non-fossiliferous drill samples is one of the difficult problems that is en­countered in sub-surface stratigraphy. In order to truly correlate a formation, it must have some dis tinctive features and have an areal persistence of these features. These requirements are probably met best by limestone.

Layer-cake, anoxia, and other myths: A new look at the Devonian-Mississippian Bakken Formation Reservoir, Williston Basin, North Dakota

The Upper Devonian-Mississippian Bakken Formation in the Williston Basin is one of the most prolific onshore petroleum systems in the continental U.S., consisting of a middle carbonate-siliciclastic member sandwiched between two organic-rich units, the Lower and Upper Bakken shales. Dr. Egenhoff discusses the formation’s surprising departures from standard stratigraphy models and depositional models which contribute to its unique characteristics.