Boulder-gravel hummocks and wavy basal till contacts: products of subglacial meltwater flow beneath the Saginaw Lobe, south-central Michigan, USA

Fisher, Timothy G.; Taylor, Lawrence D.; Jol, Harry M.

doi:10.1080/03009480301820

Cited by 16 publications

(3 citation statements)

References 28 publications

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“…2008a). Glacial landforms and the distribution of gravels and tills in south‐central Michigan point to subglacial flooding during retreat of the ice sheet (Fisher & Taylor 2002; Fisher et al. 2003).…”

Section: Hydrogeology Of Michigan Basinmentioning

confidence: 99%

Impacts of Pleistocene glaciation on large-scale groundwater flow and salinity in the Michigan Basin

2010

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Pleistocene melting of kilometer-thick continental ice sheets significantly impacted regional-scale groundwater flow in the low-lying stable interiors of the North American and Eurasian cratons. Glacial meltwaters penetrated hundreds of meters into the underlying sedimentary basins and fractured crystalline bedrock, disrupting relatively stagnant saline fluids and creating a strong disequilibrium pattern in fluid salinity. To constrain the impact of continental glaciation on variable density fluid flow, heat and solute transport in the Michigan Basin, we constructed a transient two-dimensional finite-element model of the northern half of the basin and imposed modern versus Pleistocene recharge conditions. The sag-type basin contains up to approximately 5 km of Paleozoic strata (carbonates, siliciclastics, and bedded evaporites) overlain by a thick veneer (up to 300 m) of glacial deposits. Formation water salinity increases exponentially from <0.5 g l )1 total dissolved solids (TDS) near the surface to >350 g l )1 TDS at over 800 m depth. Model simulations show that modern groundwater flow is primarily restricted to shallow glacial drift aquifers with discharge to the Great Lakes. During the Pleistocene, however, high hydraulic heads from melting of the Laurentide Ice Sheet reversed regional flow patterns and focused recharge into Paleozoic carbonate and siliciclastic aquifers. Dilute waters (<20 g l )1 TDS) migrated approximately 110 km laterally into the Devonian carbonate aquifers, significantly depressing the freshwater-saline water mixing zones. These results are consistent with 14 C ages and oxygen isotope values of confined groundwaters in Devonian carbonates along the basin margin, which reflect past recharge beneath the Laurentide Ice Sheet (14-50 ka). Constraining the paleohydrology of glaciated sedimentary basins, such as the Michigan Basin, is important for determining the source and residence times of groundwater resources, in addition to resolving geologic forces responsible for basinal-scale fluid and solute migration.

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Section: Hydrogeology Of Michigan Basinmentioning

confidence: 99%

Impacts of Pleistocene glaciation on large-scale groundwater flow and salinity in the Michigan Basin

2010

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“…Some glacial features across North America suggest a significant portion of glacial meltwaters infiltrated into bedrock aquifers, beneath wet‐based ice sheets (i.e., liquid water present at base of ice sheet, temperature at base of ice sheet is above freezing point). The distribution of gravels and tills and landforms in south central Michigan, for example, point to subglacial flooding during retreat of the Saginaw lobe of the Laurentide Ice Sheet [ Fisher and Taylor , 2002; Fisher et al , 2003]. Esker systems in glaciated regions of Canada are primarily located in areas underlain by crystalline bedrock [ Clark and Walder , 1994], where the low hydraulic conductivity of the Canadian Shield likely prevented infiltration of meltwaters into underlying bedrock aquifers.…”

Section: Introductionmentioning

confidence: 99%

Pleistocene hydrology of North America: The role of ice sheets in reorganizing groundwater flow systems

Person

McIntosh

Bense

et al. 2007

Reviews of Geophysics

147

162

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[1] While the geomorphic consequences of Pleistocene megafloods have been known for some time, it has been only in the past 2 decades that hydrogeologists and glaciologists alike have begun to appreciate the important impact that ice sheet -aquifer interactions have had in controlling subsurface flow patterns, recharge rates, and the distribution of fresh water in confined aquifer systems across North America. In this paper, we document the numerous lines of geochemical, isotopic, and geomechanical evidence of ice sheet hydrogeology across North America. We also review the mechanical, thermal, and hydrologic processes that control subsurface fluid migration beneath ice sheets. Finite element models of subsurface fluid flow, permafrost formation, and ice sheet loading are presented to investigate the coupled nature of transport processes during glaciation/ deglaciation. These indicate that recharge rates as high as 10 times modern values occurred as the Laurentide Ice Sheet overran the margins of sedimentary basins. The effects of ice sheet loading and permafrost formation result in complex transient flow patterns within aquifers and confining units alike. Using geochemical and environmental isotopic data, we estimate that the volume of glacial meltwater emplaced at the margins of sedimentary basins overrun by the Laurentide Ice Sheet totals about 3.7 Â 10 4 km 3 , which is about 0.2% of the volume of the Laurentide Ice Sheet. Subglacial infiltration estimates based on continental-scale hydrologic models are even higher (5 -10% of meltwater generated). These studies in sum call into question the widely held notion that groundwater flow patterns within confined aquifer systems are controlled primarily by the water table configuration during the Pleistocene. Rather, groundwater flow patterns were likely much more complex and transient in nature than has previously been thought. Because Pleistocene recharge rates are believed to be highly variable, these studies have profound implications for water resource managers charged with determining sustainable pumping rates from confined aquifers that host ice sheet meltwater.

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“…In combination with dating techniques, such as optically stimulated luminescence (OSL) or 14 C, GPR imaging has been used to help unravel the depositional record of depositional systems. Examples include studies of, amongst others, eolian dunes (Bristow et al, 2010), coastal sediments (Van Heteren et al, 1998;Nielsen et al, 2009;Johnston et al, 2007), river deltas and fans (Pelpola and Hickin, 2004;Winsemann et al, 2009), fluvial deposits (Bridge et al, 1998;Vandenberghe and Van Overmeeren, 1999;Wooldridge and Hickin, 2005;Sambrook Smith et al, 2009) and glaciofluvial material (Fisher et al, 2003).…”

Section: Gpr Imaging Of An Eolian Dunementioning

confidence: 99%

Landform characterization using geophysics—Recent advances, applications, and emerging tools

Dam

2012

Geomorphology

105

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Boulder-gravel hummocks and wavy basal till contacts: products of subglacial meltwater flow beneath the Saginaw Lobe, south-central Michigan, USA

Cited by 16 publications

References 28 publications

Impacts of Pleistocene glaciation on large-scale groundwater flow and salinity in the Michigan Basin

Impacts of Pleistocene glaciation on large-scale groundwater flow and salinity in the Michigan Basin

Pleistocene hydrology of North America: The role of ice sheets in reorganizing groundwater flow systems

Landform characterization using geophysics—Recent advances, applications, and emerging tools

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