EVIDENCE OF FLOW VELOCITY OF GLACIAL RIVER WARREN, MINNESOTA RIVER VALLEY

Glacial River Warren was the southern outlet of the earliest phases of Glacial Lake Agassiz. Deposits and landforms created by Glacial River Warren can be found within the present day Minnesota River Valley. Previous studies (Matsch, 1966, 1983; Bohm, 2000) have debated if changes in the levels of Lake Agassiz resulted in catastrophic flow rates of Glacial River Warren. The goal of this study was to determine the velocity, discharge, and direction of flow from the sediments of Glacial River Warren.

Two exposures of Glacial River Warren sediments were found: one just outside Montevideo, MN and the other at the Meridian Granite Quarry in Granite Falls, MN. At these exposures the dimensions of the largest cobbles were recorded, a sample of random clast sizes were taken, and the strike and dip of the imbricated cobbles were measured. The average b-Axis (intermediate) length of the largest cobbles was 16.8cm. The direction of flow indicated by the imbricated cobbles was to the south. Using the Manning equation, the estimate velocity ranged from 0.82 m/s to 7.48 m/s and the estimate discharge ranged from 22,000 m3/s to 640,000 m3/s.

The velocity and discharge results for Glacial River Warren vary greatly. Although many assumptions are involved in the calculations, paleo- flow rates of Glacial River Warren appear to be typical of large outlet rivers; that is "non-catastrophic" discharge.

Research for this study was funded by a grant from the National Science Foundation- Research Experience for Undergraduates (REU) Program (NSF-EAR 9820249).