Date of this Version
Moore, B. R., 2016. Santonian-Campanian calcareous nannofossil paleobiogeography. [M.S. thesis]: Lincoln, University of Nebraska, 46 p.
Calcareous nannofossil abundance data from 11 DSDP/ODP sites were analyzed by multivariate methods to assess the paleoceanographic change that is associated with the Santonian-Campanian boundary transition. Data were divided into Santonian or Campanian age groups based on the presence or absence of the lower Campanian nannofossil species, Aspidolithus parcus parcus. All assemblages are dominated by Watznaueria barnesiae, Micula decussata, and Prediscosphaera intercisa. Analyses determined that the relative abundance of M. decussata generally reflects a change in temperature, with a preference for cool water. Prediscosphaera intercisa appears to have had an inverse abundance relationship with M. decussata, suggesting that P. intercisa exploited niche space M. decussata could not fill due to environmental restrictions. W. barnesiae exhibits no clear distribution patterns associated with temperature.
The composition of nannofossil assemblages indicates that temperature was a factor accounting for only 21.2% of the variance within the Santonian, but was responsible for dominating 56.3% of the variance within the Campanian. The factor responsible for the most variance (35.9%) within Santonian assemblages is unknown, as it also was not dictated by nutrient availability or preservation. This study provides clarity on the paleobiogeographic environmental controls affecting nannofossil communities by demonstrating that distribution of taxa became more temperature-dependent across the Santonian-Campanian boundary.
Advisor: David K. Watkins