Sj. Hurter et Hn. Pollack, EFFECT OF THE CRETACEOUS SERRA-GERAL IGNEOUS EVENT ON THE TEMPERATURES AND HEAT-FLOW OF THE PARANA BASIN, SOUTHERN BRAZIL (VOL 7, PG 239, 1994), Basin research, 7(2), 1995, pp. 215-220
We investigate the effects of the cooling of intrusive and extrusive i
gneous bodies on the temperature history and surface heat flow of the
Parana Basin. The Serra Geral igneous event (130-135 Ma) covered most
of this basin with flood basalts. Associated with this event numerous
sills and dykes intruded the sediments and basement, and extensive und
erplating may have occurred in the lower crust and upper mantle beneat
h the basin. We develop an analytical model of the conductive cooling
of tabular intrusive bodies and use it to calculate temperatures withi
n the sediments as a function of time since emplacement. Depending on
the thickness of these igneous bodies and the timing of sequential emp
lacement, the thermal history of a given locus in the basin can range
from a simple extended period of higher temperatures to multiple episo
des of peak temperatures separated by cooling intervals. The cooling o
f surface flood basalts, sills and dykes is capable of maintaining tem
peratures above the normal geothermal gradient temperatures for a few
hundred thousand years, while large-scale underplating may influence t
emperatures for up to 10 million years. We conclude that any residual
heat from the cooling of the Serra Geral igneous rocks has long since
decayed to insignificant values and that present-day temperatures and
heat flow are not affected. However, the burial of the sediments benea
th the thick basalt cap caused a permanent temperature increase of up
to 50 degrees C in the underlying sediments since the beginning of the
Cretaceous.