The Muncie esker, a glaciofluvial ridged system, consists of three sharp-crested esker segments in the proximal and central sections, and a broad=crested, fan shaped distal segment. Grain size ranged from clay to boulders, although a larger presence of coarser material with high standard deviation values occurs in the proximal and central segments, while higher concentrations of finer sediment, primarily sand, exists in the distal segment. Field mapping and description included its geomorphic expression, stratigraphic relationships that consisted of facies identification, sedimentary structure , and paleocurrent direction. Sedimentological parameters, including downesker trends in grain size, sorting, a fractal analysis of grain size persistence, and clast roundness, was also investigated.The interpretation of the results provided us with detailed information allowing us to formulate a specific model of esker genesis. The depositional model consists primarily of nearly continuous, contemporaneous subglacial deposition that reulted in the formation of the proximal and central esker segments, and time-transgressive sedimentation, containing interlayered and randomly distributed ice rafted debris, in the form of a subaqueous delta that prograded beyond the ice-margin, forming the distal esker segment. Early stage deposition consisted of bed load transport from moderate flow velocities within a preglacial bedrock valley that served as an R-channel for preliminary subglacial meltwater drainage. Intermediate stage formation consisted of subglacial sedimentation from a hyperconcentrated deforming bed, induced by an outburst flood, and distal deltaic sedimentation as the subglacial flood discharged beyond the ice margin into an ice-marginal lake. Late stage deposition arises from bed load sedimentation of moderate fluvial activity reworking the upper portions of the hyperconcentrated flow deposits and upper deltaic facies. The finality of esker formation concluded with the ablation of the subglacial tunnel roof, sending a supraglacial debris flow that conformably covers the proximal and central esker segments in the form of a diamicton drape. / Department of Geology
| Identifer | oai:union.ndltd.org:BSU/oai:cardinalscholar.bsu.edu:handle/185965 |
| Date | January 1997 |
| Creators | Terrell, Mark A. |
| Contributors | Ball State University. Dept. of Geology., Grigsby, Jeffry D. |
| Source Sets | Ball State University |
| Detected Language | English |
| Format | x, 152 leaves : ill., maps (some col.) ; 28 cm. |
| Source | Virtual Press |
| Coverage | n-us-in |
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