Mesozoic Subsidence Rates and Lithospheric Loading in Western Canada Basin

Valerie E. Chamberlain, W. Stuart McKerrow, Richard S. Lambert

The Mesozoic stratigraphy of the Foothills area of the Western Canada basin has been used to estimate sedimentation rates, and, hence, relative crustal subsidence rates, in this region throughout the Mesozoic. Average rates of subsidence range from 0 m/Ma to 120 m/Ma, with prominent maximums occurring three times during the Mesozoic--first during the Tithonian, when rates rose to 100 m/Ma, second, during the Albian to early Santonian, when rates rose to 120 m/Ma in the north and to 70 m/Ma in the south, with subsidence occurring earlier in the north than in the south. The third period of subsidence occurred during the Campanian and Maastrichtian with rates rising to 120 m/Ma in the southern part of the basin. Tectonic loading of the lithosphere is the probable cause of th se peak crustal subsidence rates, the three separate episodes being due to the arrival of accreted terranes, first in northeast Oregon and central west Idaho during the Late Jurassic, secondly in the central Yukon during the Early Cretaceous, and thirdly in southeast British Columbia during the Late Cretaceous. During non-peak periods, average rates of subsidence ranged from 3.5 m/Ma to 35 m/Ma in the Triassic, from 0 m/Ma to 20 m/Ma in the Jurassic, and from 0 m/Ma to 30 m/Ma in the Cretaceous.

AAPG Search and Discovery Article #91040©1987 AAPG Rocky Mountain Section Meeting, Boise, Idaho, September 13-16, 1987.