NEW STRUCTURAL CONSTRAINTS ON THE LAURENTIAN MARGIN BENEATH SOUTHERN ONTARIO AND THE ADJACENT USA

Paleozoic rocks underlain by deformed terranes of the Grenville orogen of southern Ontario and adjacent New York form part of the Laurentian margin. Postulated relationships between structural features near the Paleozoic - Precambrian interface and low level earthquake activity in the region have been a recurrent topic of considerable debate.

Definitive structural constraints are contained in over 350 km of new deep crustal vibroseis data collected across southern Ontario in 2000. The seismic sections are complemented by high resolution aeromagnetic data collected in 1999 that include anomalies from near surface features including Lake Erie shipwrecks to crustal elements of the Precambrian basement at depth.

The new seismic and magnetic data, together with previous Lithoprobe data, are calibrated with existing borehole logs and shallow seismic sections to establish details of the crustal architecture of the Laurentian margin. The results provide new parameters in the study of seismic risk and boundary conditions for aquifer studies in southern Ontario and adjacent New York State.

Preliminary interpretations of seismic sections and magnetic anomalies from the Niagara Peninsula area are presented and compared to existing data beneath Lake Erie and adjacent New York State.