Transient hydrodynamics within intercratonic sedimentary basins during glacial cycles

Abstract

[1] The hydrodynamic consequences of a glaciation/deglaciation cycle within an intercratonic sedimentary basin on subsurface transport processes is assessed using numerical models. In our analysis we consider the effects of mechanical ice sheet loading, permafrost formation, variable density fluids, and lithospheric flexure on solute/isotope transport, groundwater residence times, and transient hydraulic head distributions. The simulations are intended to apply, in a generic sense, to intercratonic sedimentary basins that would have been near the southern limit of the Laurentide Ice Sheet during the last glacial maximum ($20 ka B.P.), such as the Williston, Michigan, and Illinois basins. We show that in such basins fluid flow and recharge rates are strongly elevated during glaciation as compared to nonglacial periods. Furthermore, our results illustrate that steady state hydrodynamic conditions in these basins are probably never reached during a 32.5 ka cycle of advance and retreat of a wet-based ice sheet. Present-day hydrogeological conditions across formerly glaciated areas are likely to still reflect the impact of the last glaciation and associated processes that ended locally more than 10 ka B.P. Our results reveal characteristic spatial patterns of underpressure and overpressure that occur in aquitards and aquifers, respectively, as a result of recent glaciation. The calculated emplacement of low salinity, isotopically light glacial meltwater along basin margins is roughly consistent with observations from formerly glaciated basins in North America. The modeling presented in this study will help to improve the management of groundwater resources in formerly glaciated basins as well as to evaluate the viability on geological timescales of nuclear waste repositories located at high latitudes.

Glacially generated overpressure on the New England continental shelf: Integration of full‐waveform inversion and overpressure modeling

“…Our study region has been repeatedly glaciated throughout the late Pleistocene, which can lead to sustained overpressures long after glacial retreat [Bense and Person, 2008]. …”

“…Person et al, 2007]. Many studies have modeled additional effects of ice sheets on fluid flow such as flexure of the crust and the formation of permafrost Bense and Person, 2008;Lemieux et al, 2008]; because we are only concerned with a 1-D model, and our study region is near the edge of the ice sheet, we do not account for flexure. Permafrost can reduce the permeability beneath and beyond the extent of the ice sheet.…”

“…That particular high-permeability clinoform could facilitate fluid migration from down dip where overpressure is interpreted to be higher. We consider two mechanisms that may be sources of overpressure outside our 1-D model domain: (1) overpressure generated on the continental shelf from LGM ice sheet loading and rapid sedimentation near the continental slope ( Figure 11a) [Marksamer et al, 2007] and (2) overpressure generated shoreward, where ice overburden and subsequently overpressure buildup were greater, which could migrate and increase overpressure near the ice margin where there was less ice overburden ( Figure 11b) [Boulton et al, 1993;Boulton and Caban, 1995;Bense and Person, 2008;Iverson and Person, 2012].…”

Antarctic subglacial groundwater: a concept paper on its measurement and potential influence on ice flow

“…Time lags -process (iv) -are evidenced, for example, by contemporary sedimentary basins in the northern USA (Bense & Person 2008). There, groundwater reservoirs were re-charged and overpressured during growth of the Laurentide Ice Sheet, up to the last glacial maximum approximately 20 kyr ago.…”

Hydrological connectivity from glaciers to rivers in the Qinghai–Tibet Plateau: roles of suprapermafrost and subpermafrost groundwater

“…Freezing alters the intrinsic behavior of aquifers because ground ice occupies interstitial voids and reduces the permeability of the water storage matrix (Woo, 2012). Thawing changes hydraulic connections between different water pools (Carey and Woo, 2000), further affecting the groundwater flow path and its interaction with surface water (e.g., Bense and Person, 2008;Carey and Quinton, 2005;Woo et al, 2008;Zhang et al, 2013). For example, groundwater-surface water interactions in Alaska were more commonly found in areas of discontinuous permafrost where hydraulic connections were spatially and temporally variable (e.g., Anderson et al, 2013;Minsley et al, 2012;Walvoord et al, 2012).…”