CONODONTS, MAGNETIC SUSCEPTIBILITY, AND THE FRASNIAN-FAMENNIAN BOUNDARY IN THE KETTLE POINT FORMATION, UPPER DEVONIAN, SUBSURFACE OF WESTERN ONTARIO, CANADA

The Kettle Point Formation represents fine clastic dominated Upper Devonian strata deposited in the Chatham Sag, a low that separates the Algonquin Arch from the Findlay Arch, which form the boundary between the Appalachian and Michigan basins. The Kettle Point rests disconformably on the Hamilton Group (Givetian). The Gore of Chatham drill core from Kent County, Ontario, consists of 110 m of black and interbedded lighter gray and black shales assigned to the Kettle Point that are informally subdivided into four units. The Frasnian-Famennian boundary, based on the conodont study of Winder (1966), has been placed at the base of Unit 2, the lowest thick black shale interval. In this study conodonts were recovered from a 4.5 m sequence starting at the base of the Kettle Point. Bulk magnetic susceptibility was also recorded at 5 cm intervals from this section of core. The lowest conodont recovered was Palmatolepis plana from 136.22 m, 0.4 m above the base of the Kettle Point and indicative of FZ 9-11. Palmatolepis bogartensis, indicative of FZ 13, the highest Frasnian zone, was recovered from 134.94 m. Palmatolepis triangularis, indicative of the Famennian, was recovered from 134.40 m, bracketing the F-F boundary within 0.5 m, which was tentatively placed at 134.59 m based on a negative shift in magnetic susceptibility. Palmatolepis regularis, indicative of the minuta Zone, was recovered from 132.15 m, and Pa. glabra prima, indicative of the prima Zone, was recovered from 125.98 m. The base of Unit 2, where the F-F boundary had been placed, is at approximately 120 m. Conodonts indicate that the F-F boundary, a time of mass extinction and significant global change, is 14.6 m lower, in an interval of interbedded black and gray shale in the lower part of Unit 1.