High-resolution nannofossil biochronology of middle Paleocene to early Eocene at ODP Site 1262; implications for calcareous nannoplankton evolution

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doi: 10.1016/j.marmicro.2007.05.003
Author(s): Agnini, Claudia; Fornaciari, Eliana; Raffi, Isabella; Rio, Domenico; Röhl, Ursula; Westerhold, Thomas
Author Affiliation(s): Primary:
Universita di Padova, Dipartimento di Geoscienze, Padua, Italy
Other:
Universita G. d'Annunzio di Chieti-Pescara, Italy
Bremen University, Federal Republic of Germany
Volume Title: Marine Micropaleontology
Source: Marine Micropaleontology, 64(3-4), p.215-248. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0377-8398 CODEN: MAMIDH
Note: In English. Supplemental information/data is available in the online version of this article. 105 refs.; illus., incl. strat. cols., 4 plates, 1 table, sketch map
Summary: Over the last several decades debates on the "tempo and mode" of evolution have centered on the question whether morphological evolution preferentially occurs gradually or punctuated, i.e., with long periods of stasis alternating with short periods of rapid morphological change and generation of new species. Another major debate is focused on the question whether long-term evolution is driven by, or at least strongly influenced by changes in the environment, or by interaction with other life forms. Microfossils offer a unique opportunity to obtain the large datasets as well as the precision in dating of subsequent samples to study both these questions. We present high-resolution analyses of selected calcareous nannofossils from the deep-sea section recovered at ODP Site 1262 (Leg 208) in the South-eastern Atlantic. The studied section encompasses nannofossil Zones NP4-NP12 (equivalent to CP3-CP10) and Chrons C27r-C24n. We document more than 70 biohorizons occurring over an about 10 Myr time interval, (∼62.5 Ma to ∼52.5 Ma), and discuss their reliability and reproducibility with respect to previous data, thus providing an improved biostratigraphic framework, which we relate to magnetostratigraphic information, and present for two possible options of a new Paleocene stratigraphic framework based on cyclostratigraphy. This new framework enabled us to tentatively reconstruct steps in the evolution of early Paleogene calcareous nannoplankton through documentation of transitional morphotypes between genera and/or species and of the phylogenetic relations between the genera Fasciculithus, Heliolithus, Discoasteroides and Discoaster, as well as between Rhomboaster and Tribrachiatus. The exceptional record provided by the continuous, composite sequence recovered at Walvis Ridge allows us to describe the mode of evolution among calcareous nannoplankton: new genera and/or new species usually originated through branching of lineages via gradual, but relatively rapid, morphological transitions, as documented by the presence of intermediate forms between the end-member ancestral and descendant forms. Significant modifications in the calcareous nannofossil assemblages are often "related" to significant changes in environmental conditions, but the appearance of structural innovations and radiations within a single genus also occurred during "stable" environmental conditions. These lines of evidence suggest that nannoplankton evolution is not always directly triggered by stressed environmental conditions but could be also driven by endogenous biotic control. Abstract Copyright (2007) Elsevier, B.V.
Year of Publication: 2007
Research Program: ODP Ocean Drilling Program
Key Words: 09 Paleontology, Paleobotany; 12 Stratigraphy, Historical Geology and Paleoecology; Algae; Atlantic Ocean; Biochronology; Biologic evolution; Biostratigraphy; Biozones; Cenozoic; Controls; Depositional environment; Eocene; First occurrence; High-resolution methods; Leg 208; Lower Eocene; Microfossils; Middle Paleocene; Nannofossils; Nannoplankton; ODP Site 1262; Ocean Drilling Program; Paleocene; Paleoecology; Paleogene; Plankton; Plantae; South Atlantic; Tertiary; Walvis Ridge
Coordinates: S271100 S271100 E0013500 E0013400
Record ID: 2008001859
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands