Magnetizations in Ordovician petroleum reservoir rocks, southwestern Ontario

Paleomagnetic and rock magnetic analysis was conducted on specimens collected from vertical core in four wells drilled in two producing Ordovician petroleum reservoirs of Ontario. The rock magnetic signatures of both reservoirs are similar, a mixed combination of single domain to pseudosingle domain pyrrhotite and magnetite, with minor hematite content in a few specimens. Characteristic remanent magnetization (ChRM) directions were azimuth-corrected by aligning the viscous remanence magnetization (VRM) with the present Earth's magnetic field direction. Although four distinct ChRM populations were identified through rock magnetic analysis, combined with previous geochemical and petrologic data, only two of the populations produced reliable paleodirections; the limestone (Ls) specimens had a direction of D = 172.2°, I = -0.1° (alpha 95 = 33.5; N = 5; k = 6.18) and the calcite and dolomite fracture fill specimens (Cs) had a direction of D = 183.3°, I = -10.4° (alpha 95 = 3.8; N = 49; k = 130.71). (Abstract shortened by UMI.)...