Tracking the Laurentide – On the trail of the last great ice sheet

Deglaciation – a lot of melt water Deglaciation – a lot of melt water. The terrestrial record of glacial meltwater

Con Mine, Yellowknife, Canada: Glacial meltwater in the Canadian Shield Con Mine, Yellowknife, Canada: Clark, I.D., Douglas, M., Raven, K. and Bottomley, D.J., 2000. Recharge and preservation of glacial meltwater in the Canadian Shield. Ground Water, 38: 735-742.

Con Mine, Yellowknife

Geochemistry of groundwaters

Groundwaters Cl– (mg/L) d18O ‰ VSMOW -30 -25 -20 -15 -10 1 10 100 1000 10,000 100,000 1,000,000 -30 -25 -20 -15 -10 d18O ‰ VSMOW

Modern Glacial Cl– (mg/L) meltwater ? Brine d18O ‰ VSMOW 10 Modern 100 Glacial meltwater ? Cl– (mg/L) 1000 Modern – Brine binary mixing line 10,000 Brine 100,000 -30 -25 -20 -15 -10 d18O ‰ VSMOW

How to recharge glacial meltwater . . . Late Pleistocene time: Laurentide Ice Sheet Shield brine in bedrock

Early Holocene deglaciation:

Mid to late Holocene:

Mining activities:

Finite difference modelling with SWIFT II Stationary margin of Laurentide ice sheet Proglacial Lake McConnell 2000 1000 Salinity gradients after 50 yrs Depth (m) 50% brine 60% brine 70% brine 80% brine 90% brine 0 5 10 15 Distance (km)

Con Mine, Yellowknife East Bull Lake

d2H d2H d18O d18O d2H d2H d18O d18O East Bull Lake Ottawa Chalk River -120 -100 -80 -60 -130 -110 -90 -70 -120 -100 -80 -60 d2H d2H East Bull Lake Ottawa d18O d18O -17 -15 -13 -11 -9 d2H d2H Chalk River Trois Rivières d18O d18O -17 -15 -13 -11 -9

Source: GSC

Deep Geologic Repository for Nuclear Waste

d18O in formation pore waters glacial meltwater basin brine

Glacial Meltwater

The Younger Dryas Cold Period