Nitrogen and Productivity in the Late Devonian Appalachian Basin

The Late Devonian witnessed the emergence of a new relationship between the terrestrial and marine biogeochemical cycles of the limiting nutrients nitrogen and phosphorus. The development of extensive lowland forest ecosystems augmented the flux of fixed N to coastal marine ecosystems while the development of deep soils retarded the flux of P, increasing the relative abundance of N to P in coastal seas. The accumulation of terrestrially-derived NO3 - would have been particularly pronounced in epicontinental seas such as the Appalachian Basin which enjoyed limited communication with the open ocean. Nitrogen and carbon stable isotope analyses of sediments at or near the Frasnian/ Famennian boundary within the Appalachian Basin indicate an underutilization of NO3 - coupled with high productivity corresponding to the globally correlated Upper and Lower Kellwasser horizons. High Corg:P values from similarly-aged sediments reveal that the supply of P necessary to support high productivity was remobilized from organic matter within oxygen-depleted sediments. Sea level rise may have served as the global trigger for high organic matter deposition during the Upper and Lower Kellwasser intervals by increasing the outwelling flux of terrrestrially-derived organic carbon and nitrate from lowland forests.

Note: Abstract extracted from PDF text