Ross Brandolino, “Analysis of Subglacial Deformation Present in Pleistocene-Aged Glaciotectonites of Cudahy, WI”
Mentor: John Isbell, Geosciences, Letters & Science (College of)
Poster #131
Deformed bedding interpreted to be glaciotectonic has long been observed in an exposure of late-Pleistocene-aged glacial deposits present within Sheridan Park, Cudahy, WI. Existing studies offer an overview of the deposits present within the succession, however an in-depth analysis of the glaciotectonites in the exposure has yet to be conducted. As such, the aim of this study is to describe the glaciotectonites and their associated deformation structures in conjunction with local ice-flow dynamics to aid in the understanding of the exposure and to inform models of subglacial deformation. Three primary sections of the bluff targeted for an abundance of deformational features were cleared with long-handled scraping tools, machetes, and a battery operated leaf blower. High resolution photography utilizing a drone and hand-held cameras were then used to capture the exposure, targeting sedimentary structures within cleared sections of the glaciotectonite and adjacent strata. Combined with vertical measurements of the strata, these photographs were utilized to begin construction of detailed stratigraphic columns to interpret deformational relationships in a vertical succession and compare against existing models. Further measurements were conducted on sedimentary structures to produce an ice flow direction. Preliminary measurements of deformational features produce a southern ice-flow direction for this exposure. Extensive evidence of brittle and ductile deformation associated with both compressional and extensional forces resulting from ice loading and movement is also present: boudins, micro faulting and folding, hydrofracturing, large-scale folding and shearing, brecciation, and other features have all been noted. Preliminary observations of vertical deformation relationships do not align perfectly to accepted models, however factors such as water saturation, strata cohesion, and distance from basal-ice surface may complicate matters. Further analysis of the deformation will be necessary to offer a comprehensive explanation for the deposits present.