|Madison Group, Williston Basin
A map by Peterson (1988) was used for this study and gridded (c1madisong). The map shows maximum depth of about 6,000 ft to the north.
Peterson, J. A., Longman, M. W., Anderson, S. B., Pilatzke, R. H., and Kent, D. M., 1987, Williston Basin, anatomy of a cratonic oil province: Rocky Mountain Association of Geologists, 440 p.