PRELIMINARY ANALYSIS OF CONODONT APATITE OXYGEN ISOTOPE RATIOS THROUGH THE LATE GIVETIAN GLOBAL TAGHANIC BIOCRISIS IN THE NORTHERN APPALACHIAN BASIN

During the Global Taghanic Biocrisis, approximately 385 Ma, Middle Devonian faunas worldwide underwent a major extinction in apparent conjunction with global warming, eustatic sea level rise (known as the Taghanic Onlap), and decreased oxygenation of epicontinental seas. In the type-area of this biocrisis, the Northern Appalachian Basin, faunal changes have been extensively documented at high-stratigraphic resolution as a series of three bioevents that include faunal migrations and replacements resulting ultimately in the extinction of numerous taxa of the long-lasting (4-5 My) "Hamilton Fauna" through an interval of roughly 500,000 years: 1) the nearly complete replacement of the endemic "Hamilton Fauna" with the previously equatorial "Tully Fauna"; 2) the subsequent extermination of the "Tully Fauna" and recurrence of the "Hamilton Fauna"; and 3) extinction of much of the "Hamilton Fauna", at least locally, the return of a few "Tully" taxa, and the further incursion of additional equatorial taxa. In this study, we test whether relative temperature changes inferred from the oxygen isotope ratios of conodont apatite correspond with the observed faunal transitions in the Northern Appalachian Basin, specifically, whether relatively warmer temperatures correspond to "Tully Fauna" incursions, and, conversely, the presence of the "Hamilton Fauna" corresponds with relatively cooler temperatures. Preliminary analysis of oxygen isotope ratios through the Taghanic Biocrisis show that a relative warming episode (changing from ~17.5‰ before the biocrisis, to ~16.5‰ during) corresponds with the incursion of the equatorial "Tully Fauna" into the northern Appalachian Basin (located at that time at ~30 degrees south latitude). Additionally, this warming episode apparently persisted through the extermination of the "Tully Fauna" and recurrence of the "Hamilton Fauna", such that relative temperature changes could not have been the only control on faunal migration.