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The AAPG/Datapages Combined Publications Database

Williston Basin Symposium

Abstract

SKGS-AAPG

Fifth International Williston Basin Symposium, June 14, 1987 (SP9)

Pages 77 - 82

THE MADISON, A NOMENCLATURAL REVIEW WITH A LOOK TO THE FUTURE

CLARENCE G. CARLSON, North Dakota Industrial Commission Oil and Gas Division, 900 East Boulevard, Bismarck, North Dakota 58505
JULIE A. LEFEVER, North Dakota Geological Survey, University Station Grand Forks, North Dakota 58202

ABSTRACT

The difficulty of extending nomenclature applied to Madison strata of the outcrops in Montana into the subsurface in the Williston Basin was recognized early and led to the addition of the Previous HitCharlesNext Hit Formation to the Madison Group in the subsurface of eastern Montana. Recognition of facies changes across the Basin led to the use of marker horizons to delineate marker-defined units within Madison strata on the east flank of the Basin. Numerous terms were introduced for marker-defined units and different horizons were used in different areas for similar terms. Exploration has now provided a means for establishing the stratigraphic relationships of the marker-defined units, and a review of the stratigraphic code provides a basis for clarifying nomenclature.

It is herein proposed that the lithostratigraphic terms Madison Group, Previous HitCharlesNext Hit, Mission Canyon, and Lodgepole Formations be retained as formal stratigraphic units. The facies relationships of the evaporites and carbonates are recognized by placing the Previous HitCharlesNext Hit-Mission Canyon contact at progressively lower stratigraphic horizons towards the east flank of the Basin, so that the lowest evaporites are in the Previous HitCharlesTop Formation. The marker-defined units or marker horizons are considered informal units and may be referred to as intervals, subintervals, cycles, formats, marker horizons, or facies.

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