CONODONT EVENTS OF THE LATE LLANDOVERY (SILURIAN) THROUGH EARLIEST DEVONIAN OF THE NORTH AMERICAN MIDCONTINENT

Eight conodont events can be recognized in the Silurian (late Llandovery-Pridoli) through earliest Devonian in the North American Midcontinent. Four of the conodont events are extinction events. Two conodont extinction events are recognized in the early Wenlock (earliest Sheinwoodian and late Sheinwoodian), one in the early Ludlow (Gorstian), and one in the latest Silurian (latest Pridoli)-earliest Devonian. Three of the extinction events correspond with Silurian oceanic events recognized by Jeppsson (1998): Ireviken, Boge, and Klonk Events. The other extinction event occurred during the early part of the Sproge Primo Episode of Jeppsson (1998). All four conodont extinction events likely occurred over a period of time of less than 500,000 years. The four events also correlate with previously recognized periods of global sea-level fall.

Four of the conodont events are origination events. Two conodont origination events are recognized in the late Llandovery (early Telychian and late Telychian), one in the late Ludlow (Ludfordian), and one in the late Pridoli. Three of the origination events occurred during Silurian oceanic secundo episodes recognized by Jeppsson (1998): Malmøykalven, Hoburgen, and late Pridoli Secundo Episodes. The other conodont origination event occurred during the Snipklint Primo Episode of Jeppsson (1998). All four origination events likely occurred during a period of time of less than 500,000 years. The four events also correlate with previously recognized periods of global sea-level rise.