Evaluation of colder marine waters hypothesis for cause of the Frasnian-Famennian mass extinction

Anya Kircher

New Mexico State University, Department of Geological Sciences

Las Cruces, New Mexico

[email protected]

The Late Devonian mass extinction is characterized by severe loss of ecological diversity in shallow marine environments. One possible cause of the extinction is global marine temperature change, which is supported by oxygen isotope records of Frasnian and Famennian strata. Most of the evidence for marine cooling comes from locations that faced the Rheic Ocean basin during the Late Devonian. No previous studies have compared the oxygen isotope records from strata of shallow and deeper marine environments. I will test two main hypotheses: 1) global marine waters progressively cooled from the Late Frasnian into the Famennian, and 2) the paleotemperature changes affected both deep marine and shelf environments in a similar manner. The field area, in eastern Nevada, was a shelf setting facing the Panthalassa Ocean during the Late Devonian. I will test my first hypothesis utilizing oxygen isotope analysis of several types of apatitic fossils from two coeval stratigraphic sections, one which represents a shallow shelf environment and one which represents a deeper shelf environment. Comparing these two upper Devonian stratigraphic sections will allow me to test my second hypothesis concerning the paleotemperature equivalence of deep versus shallow marine environments. This study will help establish a global temperature change signal, by contributing more data from the Panthalassa Ocean basin. Since heavier losses are recorded for shallow marine environments than for deeper marine environments, a comparison of temperature changes in both environments will also help determine whether or not temperature is a likely cause of the extinctions.

AAPG Search and Discovery Article #90060©2006 AAPG Foundation Grants-in-Aid