Structure and Stratigraphy of the Laurentian Basin

Phonse Fagan and Michael Enachescu
Earth Sciences, Memorial University, St. John's, NL, NF, Canada

Objectives:

To map the gross structure and stratigraphy of the Laurentian Basin, located off the south coast of Newfoundland, and investigate linkages between Mesozoic rifting and the underlying Paleozoic basement fabric.

Procedures:

This study is based on a detailed re-interpretation of a re-processed version of Geological Survey of Canada’s Atlantic regional seismic grid supplemented by recently acquired industry seismic, along with public domain well data and regional gravity/mag data.

Results and Conclusions:

Seismic interpretation is complicated by the presence of two salt intervals (Carboniferous and Triassic) which appear to have interacted in places. Having been affected by both strike slip and extensional tectonics the north boundary of the basin is a steep hinge zone manifested as series of down to the basin faults. Late Triassic - Early Jurassic Rifting was followed by seaward tilting of the basin throughout the Jurassic. The regional “Base Cretaceous” unconformity marks the rise of the Avalon Uplift to the east during the Late Jurassic-Early Cretaceous, after which the basin enters the passive margin stage. A relatively undeformed Cretaceous section overlies the unconformity, and is in turn overlain by a seaward prograding Tertiary section. The Tertiary records further subsidence along with dramatic erosional features arising from the interplay of sea level changes with the ancestral St. Lawrence River. There is evidence of renewed strike slip movement along the Paleozoic suture (Cobequid-Chedabuckto Fault) during the Mesozoic rifting from regional geological/geophysical correlations. Although somewhat complicated by salt tectonics seismic data also shows faults radiating from the Cobequid-Chedabuckto fault reaching the seabed in part of the study area.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas