Glacial Sedimentology and Stratigraphy of Northern Illinois: Glacial Processes During Climate Fluctuations
Mentor 1
John Isbell
Location
Union Wisconsin Room
Start Date
27-4-2018 1:00 PM
Description
Towards the end of the Pleistocene Epoch, the Lake Michigan lobe of the Laurentide Ice Sheet extended across northern Illinois. During glacial maximum, the ice produced terminal moraines and extensive melt-water that deposited sediments in braided streams, lakes, marine channels, and deltas. Analyzing these deposits left behind on the landscape helps to understand the dynamic conditions that occurred along the front of this ice sheet as it began to recede. Additionally, these deposits help scientists to understand the transition from glacial to interglacial conditions and the processes that occur during periods of climatic changes. McHenry County, Illinois was a centerpiece during the last ice age, and has a vast amount of glacial driven depositional features produced from the Harvard sub-lobe of the Lake Michigan lobe. Recent studies at a gravel pit in Richmond, Illinois suggest multiple advancements of glaciation that left behind esker, channel fill, and braided stream outwash gravels. Lying on top of the gravels is a subglacially deposited diamict. Additionally, boulders that protruded out of the underlying gravels were sculpted into bullet-shaped clasts with glacial striations that indicate the direction of glacial flow as ice advanced across this area. Diamict-filled cracks in the underlying gravel suggest that the ice advanced over permafrost. Following ice advance, grabben-like structures along the top of the diamict indicate stagnation of the ice lobe and collapse of the glaciated landscape as ice blocks covered in debris melted. Above the diamict, there is evidence of an outwash plain with intergraded fine sands and cobbles that further indicate glacial retreat during a warming climate. The majority of fine sands show ripple and cross-bedded formations that indicates the flow direction of melt water. The evidence found in this study, shows the dynamics of sediment deposition during glacial and interglacial periods. Data collected here can be compared and contrasted to other glacial impacted sites to try and understand the depositional processes and climatic trends during glacial periods.
Glacial Sedimentology and Stratigraphy of Northern Illinois: Glacial Processes During Climate Fluctuations
Union Wisconsin Room
Towards the end of the Pleistocene Epoch, the Lake Michigan lobe of the Laurentide Ice Sheet extended across northern Illinois. During glacial maximum, the ice produced terminal moraines and extensive melt-water that deposited sediments in braided streams, lakes, marine channels, and deltas. Analyzing these deposits left behind on the landscape helps to understand the dynamic conditions that occurred along the front of this ice sheet as it began to recede. Additionally, these deposits help scientists to understand the transition from glacial to interglacial conditions and the processes that occur during periods of climatic changes. McHenry County, Illinois was a centerpiece during the last ice age, and has a vast amount of glacial driven depositional features produced from the Harvard sub-lobe of the Lake Michigan lobe. Recent studies at a gravel pit in Richmond, Illinois suggest multiple advancements of glaciation that left behind esker, channel fill, and braided stream outwash gravels. Lying on top of the gravels is a subglacially deposited diamict. Additionally, boulders that protruded out of the underlying gravels were sculpted into bullet-shaped clasts with glacial striations that indicate the direction of glacial flow as ice advanced across this area. Diamict-filled cracks in the underlying gravel suggest that the ice advanced over permafrost. Following ice advance, grabben-like structures along the top of the diamict indicate stagnation of the ice lobe and collapse of the glaciated landscape as ice blocks covered in debris melted. Above the diamict, there is evidence of an outwash plain with intergraded fine sands and cobbles that further indicate glacial retreat during a warming climate. The majority of fine sands show ripple and cross-bedded formations that indicates the flow direction of melt water. The evidence found in this study, shows the dynamics of sediment deposition during glacial and interglacial periods. Data collected here can be compared and contrasted to other glacial impacted sites to try and understand the depositional processes and climatic trends during glacial periods.
