Date of Award


Document Type


Degree Name

Master of Science (MS)



First Advisor

F.D. Holland, Jr


The distribution of corals, other fossils, and rock types of the Madison Group in the Williston Basin were studied in 29 cores (involving over 6,200 feet of core) from the Bottineau, Tilston, Frobisher-Alida, and Ratcliffe intervals in the western half of North Dakota. Occurrence of rock types, corals, and other fossils (brachiopods, bryozoans, red algae, and gastropods) of the Mission Canyon and lower Charles Formations were plotted in three cross-sections against the informal marker-defined intervals (Tilston, Frobisher-Alida, and Ratcliffe), as identified from well logs. Distribution and abundance of corals in nine of the more extensive cores were related to interpreted depositional environments.

Three regressive carbonate cycles, corresponding to the Tilston, Frobisher-Alida, and Ratcliffe intervals, were recognized for the Mission Canyon and lower Charles. Each depositional cycle was interpreted to comprise five successive depositional environments (I, Supratidal-Intertidal; II, Intertidal; III, Restricted Marine; N, Transitional; and V, Open-Marine) and six subenvironments. Each cycle begins with rocks representing an open-marine environment (V), followed by rocks representing progressively shallower environments (IV, III, and II) and culminating in rocks representing a supratidal-intertidal environment (I) at the top of each cycle.

Ninety-two percent of the coral fauna is dominated by four genera. Forty-five percent of the coral fauna consists of Vesiculophyllum, 18 percent of Sychoelasma, 17 percent of Amplexizaphrentis, and 12 percent of Cyathaxonia. The remaining 8 percent of the coral fauna consists of Syringopora, Siphonodendron, Stelechophyllum, Michelinia, Lophophyllum, and Amplexocarinia. This study is the first record of occurrence of Stelechophyllum micrum and S. banffense in the conterminous United States. The occurrence of these two species in southwestern Alberta indicates a connection between the Mississippian Alberta shelf and the Madison depositional complex in North Dakota.

As the result of this study, four coral zonules are proposed for the Williston Basin of North Dakota; in ascending order they are: the Stelechophyllum micrum zonule, the Michelinia-Cyathaxonia zonule, the Stelechophyllum banffense zonule, and the Siphonodendron oculinum zonule. Diagnostic zonule index corals were found in different lithologies representing several depositional environments, and the zonules were found to parallel the Madison markers which define the intervals. This supports previous suggestions that the marker-defined intervals are time-parallel units in North Dakota. Moreover, the coral zonation can be used in the central part of the basin beyond the limit of the defining log markers.

Coral biostratigraphic data suggest that the Bottineau interval is late Kinderhookian to early Osagean in age, the Tilston interval is middle Osagean, the Frobisher-Alida is late Osagean to early Meramecian, and the Ratcliffe is early Meramecian.

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