Misfit Streams and the Possible Glacial Origin of Their Valleys

A study of misfit streams and meandering depressions developed in ground moraine deposits near Dayton, Ohio has indicated that streams are re-establishing old stream courses, which persist as buried channels previously carved into bedrock. The erosion of deep meandering channels in bedrock appears consistent with melt-water streams let down through glacial ice. Such channels would subsequently be filled with porous stream deposits in post-glacial times, allowing for rapid groundwater flow and enhanced solutioning of predominantly carbonate stream gravels. Once the depressions were lowered below the water table through groundwater solution, misfit channels were established by normal stream erosion. The detailed study of one misfit stream located near Byron, Ohio has indicated the presence of a buried bedrock channel 90 feet deep with a bedrock surface gradient of 400 feet per mile. OHIO J. SCI. 76(3) 123, 1976 In the vicinity of Dayton, Ohio, many relatively shallow surface depressions with large meanders may be observed in the ground moraine material deposited at the end of the Wisconsin glaciation. Some of these depressions contain no regularly observable stream flow, while others contain well-defined channels with meanders at least one order of magnitude smaller than those of the main depression. The depressions are most clearly seen at the boundary between valley train deposits and ground moraine. Proceeding into the ground moraine from this boundary, the depressions appear progressively less well defined until the lack of any channel and the shallow relief make them imperceptible. They may be followed even further towards their sources during periods of high intensity rain, when many temporary streams are flowing in depressions which could not otherwise be observed. Perennial tributaries to major streams also fit this description, but there are many more depressions which are dry most of the time, and which are not apparent to the untrained eye. The density of these misfit streams and meandering depressions without channels Manuscript received July 28, 1975 and in revised form March 25, 1976 (#75-50). is much greater than the density of current stream development. The presence of misfit streams is not peculiar to the Dayton area, but is a common feature of many regions which were once glaciated, and where melting ice once greatly augmented stream flow. The particular misfit streams being considered here give some definite clues to the circumstances and climate under which they originated. Seismic data and other factors suggest that these streams are re-occupying gravel filled channels previously developed into bedrock. MISFIT STREAM CHARACTERISTICS The meandering depressions and misfit channels are observed to fit a remarkably consistent pattern throughout the area under study. In tracing a stream down from its headwaters, a nearly imperceptible depression is seen to connect into a well-incised depression, first containing an intermittent stream and then, down valley, a perennial stream. In all cases, the sinuous stream which eventually flows in the meandering valley has a meander wavelength much smaller than that of the valley itself. Valleys can be seen in all stages of development, and they locally pass through patches of relatively undisturbed woodland (sug-