Jc. Mareschal et al., Heat flow variations in a deep borehole near Sept-Iles, Quebec, Canada: Paleoclimatic interpretation and implications for regional heat flow estimates, GEOPHYS R L, 26(14), 1999, pp. 2049-2052
A deep (> 2000m) borehole in the Sept-lies intrusion, on the north shore of
the Saint Lawrence River, in Quebec, Canada, was repeatedly logged for tem
perature. Systematic variations of the temperature gradient with depth are
not correlated with the thermal conductivity. We interpreted the temperatur
e profile as follows:
(1) During the last glacial maximum, the temperature at the base of the ice
sheet was cold (approximate to -5 degrees C); (2) When the region was belo
w sea level, between 10 and 5ky B.P., the ground surface temperature was wa
rm (approximate to 6 degrees C); (3) The average ground surface temperature
dropped to approximate to 2 degrees C at 5ky B.P. when the region rebounde
d above sea level; (4) The long time averaged ground surface temperature be
fore the last glacial maximum was approximate to 0 - 1 degrees C; (5) The r
eference heat flow (36 - 37mW m(-2)) is 4 - 5mW m(-2) higher than estimated
from the upper 1000m bf the heat flow profile.
This interpretation can not be extrapolated to the entire region covered by
the Laurentide ice sheet. Except for extremely deep (> 1500m) boreholes, t
he small uncertainty (< 15%) affecting heat flow estimates can not be elimi
nated.