A CASE STUDY IN EXCEPTIONAL PRESERVATION: EVALUATING THE ROLE OF ANOXIA IN A NEW EXAMPLE OF SOFT-BODIED PRESERVATION FROM THE MIDDLE DEVONIAN (GIVETIAN)

The Middle and Late Devonian are well known for anomalous environmental conditions, which are often linked to periods of ecological stress. These culminate in one of the ‘Big 5’ mass extinctions at the Frasnian/Fammenian boundary, however this event was likely preceded by dynamic conditions on both global and local scales. Anoxia has often been implicated as a potential driver of ecological stress during this interval, and is one of the main factors linked to occurrences of exceptional fossil preservation throughout the Phanerozoic. Though there are instances of exceptional soft-bodied preservation known from the Middle and Late Devonian, these are generally understudied and very rarely evaluated from a combined paleoecological and geochemical perspective. Here, we investigate enigmatic soft-bodied discoidal fossils from three localities from the Middle Devonian (Givetian) of upstate New York. These disks occur in an otherwise fossil barren interval, devoid of typical Devonian shelled taxa. The coincident occurrence of these soft-bodied discs with the disappearance of more common shelled taxa suggests a potential shift in redox conditions to those more favorable for exceptional preservation. The occurrence of these fossils in shales facilitates the use of geochemical proxies such as iron speciation and redox-sensitive trace metal concentrations (i.e., Mo, Mn, V). This data will be used to assess local redox conditions and determine the potential role they played in the preservation of these fossils. Data from previous studies suggests a dynamic redox history at this time, which may have facilitated soft-bodied preservation. Importantly, the spatiotemporal distribution of these enigmatic fossilized disks suggests that oxygen stress was regionally widespread in the Appalachian Basin before the more well-known 'anoxic events' associated with global declines in diversity during the Late Devonian.