Glacial impacts on hydrologic processes in sedimentary basins: evidence from natural tracer studies

Abstract

This study reviews and synthesizes the results from geochemical and isotopic case studies across Europe, North America, Antarctica, and Greenland to evaluate the effects of Pleistocene glaciation on continental-scale groundwater circulation in sedimentary basins. The most effective studies, in terms of delineating high-resolution records of paleorecharge to aquifers, combine solute chemistry, stable isotopes of water, age tracers, and dissolved noble gases. Some of the lowest d 18 O values ()22&), and noble gas temperatures (0°C), and high excess air concentrations were found in confined groundwaters in northern Estonia, likely derived from Scandinavian Ice Sheet subglacial recharge. These results are consistent with groundwater systems in North America that were recharged beneath the Laurentide Ice Sheet. Late Pleistocene precipitation may have also been an important source of recharge, as indicated by low-temperature, isotopically enriched groundwaters in several basins. Detectable age gaps have been observed in several aquifer systems in North America and Europe, likely caused by a hiatus of groundwater recharge in areas covered by permafrost during the Last Glacial Maximum (10-21 ka). Aquifers that were not covered by ice sheets or permafrost contain continuous records of Pleistocene to Holocene recharge with variable d 18 O values and low paleotemperatures (4-9°C lower than today). The maximum depth of glacial meltwater penetration into sedimentary basins is approximately 50-1000 m. Infiltration of dilute meltwaters dissolved large quantities of halite in evaporite-bearing basins. The presence of clay-rich glacial deposits and bedrock confining units enhanced the storage of meltwaters within low-permeability sediments and limited flushing of paleowaters in underlying aquifers. These results demonstrate the importance of continental glaciation as a driver for basinal-scale fluid and solute transport and have implications for long-term storage of radioactive waste and carbon dioxide at depth in high-latitude sedimentary basins.

Influence of late Pleistocene glaciations on the hydrogeology of the continental shelf offshore Massachusetts, USA

“…We conduct a sensitivity study to address the effects of permeability on freshwater distribution. Permeability has a strong control on the emplacement and preservation of Pleistocene meltwater in glaciated sedimentary basins as low‐permeability confining units prevent flushing of underlying aquifers after ice sheet retreat [ McIntosh et al ., ; Person et al ., ]. Permeability was assigned to the base‐case model based on lithology interpreted from seismic data.…”

“…Evidence of glacially emplaced freshwater into the basins comes from many sources [ Post et al ., ]. Age data from carbon‐14 and noble gases reveal a Pleistocene age for much of the freshwater [ Morrissey et al ., ; Schlegel et al ., ], and oxygen isotope data reveal isotopically light freshwater which is interpreted as water of glacial origin [ Vaikmae et al ., ; McIntosh et al ., ]. In addition, numerical models indicate large volumes of subglacial meltwater may have been driven into basin sediments during Pleistocene glaciations [ Person et al ., , 2012; Post et al ., ].…”

Ice sheet load cycling and fluid underpressures in the Eastern Michigan Basin, Ontario, Canada

“…Aquifers containing glacial meltwater that was recharged under conditions unlike those at present [e.g., McIntosh et al ., ] have shown glaciation can strongly affect subsurface flow systems. Low‐permeability environments might also be expected to bear the imprint of recent glaciations in the form of pressure anomalies [ Person et al ., ], but evidence for this is equivocal [e.g., Bahr et al ., ; Grollimund and Zoback , ; Vinard et al ., ].…”

Constraining groundwater flow in the glacial drift and saginaw aquifers in the Michigan Basin through helium concentrations and isotopic ratios

“…High salinity fluids are found at all depths in the Michigan Basin, from the deep Ordovician St. Peters Sandstone up to the shallowest subsurface levels (e.g., Glacial Drift, Long et al 1988;Wilson 1989). The origin of such high salinities, however, remains uncertain and has been the focus of numerous studies (Long et al 1988;Wilson 1989;Wilson & Long 1993a,b;Ging et al 1996;Martini 1997;McIntosh et al 2004McIntosh et al , 2011McIntosh et al , 2012Ma et al 2005). Upward transport of deep basinal brines and subsequent mixing with meteoric water has been previously proposed to account for the presence of high salinity groundwater in near-surface environments in the Michigan Basin (Long et al 1988;Mandle & Westjohn 1989;Weaver et al 1995;Kolak et al 1999;McIntosh et al 2004McIntosh et al , 2011.…”