| Summary
The Late Devonian mass extinction witnessed the collapse
of several ecosystems, including reefs and the planktonic
food chain. Level bottom communities, dominated by brachiopods,
were also devastated. These losses were accompanied by postulated,
dramatic changes in marine redox conditions, with oscillations
from anoxic to fully oxygenated conditions. This project is
evaluating these redox fluctuations using the new technique
of pyrite framboid size assay in combination with traditional
geochemical approaches (authigenic U enrichment) and sedimentological
approaches. The timing of the changes is being compared with
the fossil record of the tentaculitids, an abundant group
of planktonic microfossils, that disappeared druing the crisis.
Fieldwork is concentrating on the global type sections of
the Montagne Noire, S. France and the classic German sections
that contain the Kellwasser Horizons - two bituminous limestones
thought to record anoxic deposition at the time of the extinction.
In addition, the broad spectrum of palaeoenvrionments recorded
in the reef-to-basin centre sections of the Holy Cross Mountains
(Poland) and the inner ramp-to-outer ramp and basin settings
of the foreland basin of eastern Nevada are also under investigation.
It is hoped to get a global appreciation of the intensity
and extent of the Kellwasser anoxic horizons. |
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