Genetic Stratigraphic Analysis of Upper Mission Canyon Formation (Mississippian), Williston Basin, North Dakota

David N. Witter

The fundamental building block of shallow-marine stratigraphic sequences is the progradational unit, herein termed a "genetic sequence." A genetic sequence is the direct product of the interactions of sea level fluctuation, tectonic subsidence, and sediment supply or production. Numerical models that incorporate these controls simulate facies distributions and stratal architecture of siliciclastic marine-shelf to coastal-plain environments. The models also suggest a theoretical basis for extracting time lines directly from rock units. From the theory, a methodology has been developed to accurately correlate rock units of diverse lithologies using well-log data. Although the models were developed for siliciclastics, the upper Mission Canyon, northeastern Williston basin, p ovides a case study for testing the applicability of the genetic stratigraphic correlation technique in marine carbonate and evaporite strata.

Previous correlations within the study interval have relied principally upon radioactive well-log markers. High-resolution facies analysis of cores and calibration of well-log responses to facies and facies successions has led to the recognition and correlation of asymmetric shallowing-upward genetic sequences within marker-defined stratigraphic intervals. These correlations provide significantly greater vertical and temporal resolution than is achieved by correlating well-log markers alone. The genetic stratigraphic correlation technique also allows lateral correlation of dissimilar facies and provides the basis for predicting the spatial distribution of reservoir and seal rocks. Successive genetic sequences are arranged in an overall seaward-stepping hierarchy, with several landward stepping genetic sequences occurring within marker-defined stratigraphic intervals. The spatial geometries of genetic sequences and distributions of reservoir facies within sequences can be predicted from changes in thickness of successive genetic sequences within a single well-log profile.

AAPG Search and Discovery Article #91033©1988 AAPG Rocky Mountain Section, Bismarck, North Dakota, 21-24 August 1988