The objectives of this study were to quantitatively analyze calcareous nannofossil assemblages across the Cretaceous/Tertiary (K/T) boundary of several sections to determine the nature of nannoplankton extinctions and to compare the results with recent hypotheses of step-wise or sequential extinctions of planktonic foraminifer. Objectives were also to compare uppermost Maastrichtian and lowermost Danian nannofossil assemblages across latitude in the Indian, Tethys, and Atlantic Ocean to determine biogeographic gradients indicative of the latitudinal thermal gradients. The results of these investigations are summarized as follows. (1) No step-wise or gradual extinctions are noted. Nannoplankton extinctions are synchronous and correlate with shifts in carbon isotopes, carbonate sedimentation decline, and anomalous iridium abundance. (2) No unequivocal evidence exists for survivorship of Cretaceous species in Danian sediments. Associations with iridium in particular, suggests that Cretaceous specimens in Danian sediments are reworked by processes of bioturbation and/or current activity. (3) There is no evidence of significant changes in latest Maastrichtian nannofossil assemblages. This indicates stable conditions preceding the K/T boundary event. (4) The lowermost Danian is characterized by sequential blooms of surviving and new species. No two localities are the same in terms of the species composition of these blooms. This reflects the unstable conditions around the globe following the K/T boundary crisis. (5) Latitudinal thermal gradients were established in the Southern Hemisphere by latest Maastrichtian time and continued into the early Danian as indicated by the biogeographic provinces defined by Prediscosphaera stoveri and Hornibrookina. / Source: Dissertation Abstracts International, Volume: 54-07, Section: B, page: 3530. / Major Professor: Sherwood W. Wise, Jr. / Thesis (Ph.D.)--The Florida State University, 1993.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_76981 |
| Contributors | Pospichal, James Jude., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 378 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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