QUATERNARY LITHOSTRATIGRAPHIC MAPPING IN THE NORTHERN RED RIVER VALLEY—MINNESOTA, NORTH DAKOTA, AND MANITOBA

The geological surveys of Minnesota and North Dakota are reinterpreting existing studies and conducting new investigations in order to compile a 3-D model of the Phanerozoic geology and stratigraphy of the northern Red River Valley. Our work will be concentrated in a 36,700 km˛ (14,200 mi˛) area in adjacent parts of North Dakota and Minnesota bounded on the north by Manitoba. Our results will be combined with similar work that has been completed in the Fargo-Moorhead and Winnipeg areas to produce a 3-D model of the Phanerozoic geology and stratigraphy of the entire Red River Valley.

Understanding the Quaternary stratigraphy is a key element of this study. This study will combine all available data in the study area with data derived from rotasonic drilling in Manitoba to interpret the Quaternary stratigraphy using computer-assisted techniques. The existing North Dakota and Minnesota database contains information on 1 555 samples; collected from 375 sites; it is being supplemented with 297 addition samples recovered from 23 rotasonic sites in Manitoba.

Computer-assisted interpretation techniques have recognized 34 lithostratigraphic units in previous studies in the US portion of the Red River Valley. We are currently analyzing the Manitoba dataset and conducting new drilling in data-poor areas. Stratigraphic correlations will be made using methods developed at the Minnesota Department of Natural Resources using ArcView-generated, water-well cross sections; geologic control developed by this study; and surficial geologic maps.

A surficial lithostratigraphic map of the study area will be compiled from five existing 30' X 60' geologic maps in North Dakota and Minnesota and new mapping in four Minnesota 30' X 60' quadrangles. Map units will be developed that allowed the geologic maps from the various sources to be combined and interpreted to produce a lithostratigraphic map.

This work is being planned as a cooperative effort between the North Dakota, Minnesota, and Manitoba agencies. It illustrates the fundamental necessity of interagency cooperation for the development of an understanding of the geology of the Red River Valley and associated environmental and water related problems in the area.