Abstract ID/ No de résumé: 662
ESTIMATES OF TIMING AND MAGNITUDE OF SUBGLACIAL FLOOD DISCHARGES : LAURENTIAN CHANNEL AND HUDSON STRAIT OUTLETS OF THE LAURENTIDE ICE SHEET
PIPER, D.J.W., Bedford Institute of Oceanography, Dartmouth, N.S., B2Y 4A2; piper@agc.bio.ns.ca
Room for the session: 301a
Board if it is a poster:
Date of the presentation (mm/dd): 05/19
Beginning of the presentation: 14:40
Number of symposium, special session or general session: SY7
Lieu de la présentation: 301a
# du tableau si c'est un poster :
Date de la présentation (mm/dd): 05/19
Début de la présentation: 14:40
No du symposium, de la session spéciale ou de la session générale: SY7
Geologic evidence has been sought for late Wisconsinan subglacial flood discharges from the Laurentian Channel and Hudson Strait outlets of the Laurentide Ice Sheet. A 3-m thick gravel bed on the floor of Eastern Valley of Laurentian Fan has been previously interpreted as deposited from the 1929 "Grand Banks" turbidity current. Stratigraphy of overlying cores and the details of erosion forms suggest this bed is older and is correlative with regional erosional features and a widespread sand bed on the Sohm Abyssal Plain dating from the late Pleistocene. It also appears to correlate with a widespread deposit of red mud on the Scotian Slope that was derived as a plume from the Laurentian Channel. These muds yield dates of 14.5 - 16 ka, with older ages present only on the eastern Scotian Slope. Thick muddy turbidites deposited on Laurentian Fan may be derived either from the flow that deposited the gravel bed, or more probably by evolution of the surface plume by settling.
The total volume of meltwater discharged during the accumulation of these sediments can be estimated. The 14.5 ka gravel and sand deposit is several times larger than the 1929 turbidite, for which total water volume has been estimated as 2-5 x 103 km3. The volume of red clay on the Scotian margin is of order 102 km3, equivalent to more than 104 km3 of water, assuming a suspended sediment concentration of 40 gm/l, the critical concentration required to form a hyperpycnal flow. The presence of a surface plume implies a lower concentration and hence a higher volume than this minimum estimate.
New seismic-reflection profiles from the seabed off Hudson Strait show widespread shallow gullying on the continental slope but no direct evidence of catastrophic flood discharge. New cores on the continental slope south of Hudson Strait show plume and nepheloid layer deposits derived from sediment plumes discharging from Hudson Strait during Heinrich Event 1. Preliminary sediment volume estimates (and hence estimates of volume of water discharged) are similar to those for the Laurentian Channel outlet.
This work on subglacial flood events has been carried out in collaboration with John Shaw, Ken Skene, Reinhard Hesse, Trecia Schell, Harunur Rashid and Donny Barber.
Total number: 1