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The Oligocene nannolith Sphenolithus evolutionary lineage: morphometrical insights from the palaeo-equatorial Pacific Ocean
Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
The Natural History Museum, London, UK.
Stockholm University, Faculty of Science, Department of Mathematics.
2010 (English)In: Journal of Micropalaeontology, ISSN 0262-821X, E-ISSN 2041-4978, no 29, 17-35 p.Article in journal (Refereed) Published
Abstract [en]

Changes in morphology within the biostratigraphically important Oligocene nannofossil lineage, Sphenolithus predistentus-distentus-ciperoensis, were investigated in carbonate sediments from the paleo-equatorial Pacific Ocean Site 1218 in order to determine the nature of this evolutionary lineage. Using differences in their morphology and stratigraphic ranges, the aim of this study was to determine whether this set of sphenolith species represents an anagenetic evolutionary lineage or a set of discrete species with overlapping geological ranges. 1000 specimens were analysed morphometrically and the basal ratio (the ratio between the proximal cycle height and basal width), was identified as a key parameter for study of this lineage. We conclude that S. distentus and S. predistentus are intergradational species forming an anagenetic lineage but that S. ciperoensis is a discrete species which evolved relatively abruptly in the Late Oligocene.

Place, publisher, year, edition, pages
2010. no 29, 17-35 p.
Keyword [en]
Oligocene, Sphenolithus predistentus, S. distentus, S. ciperoensis, evolutionary lineage, morphometry, ODP Leg 199 Site 1218, Pacific Ocean
National Category
Geology
Research subject
Geology
Identifiers
URN: urn:nbn:se:su:diva-27597DOI: 10.1144/jm.29.1.17ISI: 000279030100003OAI: oai:DiVA.org:su-27597DiVA: diva2:216399
Available from: 2009-05-08 Created: 2009-05-08 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Late Eocene through Oligocene calcareous nannofossils from the paleo-equatorial Pacific Ocean – taxonomy, preservation history, biochronology and evolution
Open this publication in new window or tab >>Late Eocene through Oligocene calcareous nannofossils from the paleo-equatorial Pacific Ocean – taxonomy, preservation history, biochronology and evolution
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This study aims to unravel the ecological and evolutionary dynamics within the calcareous nannofossil communities at the Eocene/Oligocene (E/O) transition and during the Oligocene time when Cenozoic 'icehouse' conditions were established. The main question this study aims to answer is whether the changes in the nannofossil assemblages were controlled by intrinsic evolutionary trends or if the changes were controlled by environmental factors such as changes in temperature and nutrient availability in the surface water. These questions are addressed with detailed analyses of the taxonomy, biostratigraphy and fluctuations in abundance and diversity of calcareous nannofossil assemblages from a continuous latest Eocene through Oligocene sediment section from the ODP Site 1218 (8°53.38´N, 135°22.00´W), paleo-equatorial Pacific Ocean. An improved nannofossil taxonomy and biostratigraphy has been established. At the E/O transition, changes in the nannofossil preservation mimics changes in calcium carbonate content. A detailed investigation of late Eocene and Oligocene sediments yields age estimates for ten nannofossil bioevents. Morphometric studies of the Reticulofenestra umbilicus-R. hillae show that these cannot be subdivided into two different morphospecies. Based on different morphometry and stratigraphic ranges, the Oligocene Sphenolithus lineage appears to be the result of a combined anagenetic and cladogenetic evolution. A new nannolith species is described: Triquetrorhabdulus longus. High-resolution nannofossil data indicate changes in the composition, abundance and diversity of the mid-Oligocene assemblages. Intervals of high diversity index coincide with Oi-glaciation events. However, visual examination of the variations in abundance of nannofossil taxa do not appear to correlate with changes in either oxygen or carbon isotopes. This presumably indicates that a dynamic equilibrium did not exist between these Oligocene nannoplankton assemblages and changes in surface water temperature or productivity conditions.

 

Place, publisher, year, edition, pages
Stockholm: Department of Geology and Geochemistry, Stockholm University, 2009. 26 p.
Series
Meddelanden från Stockholms universitets institution för geologi och geokemi, ISSN 1101-1599 ; 334
Keyword
marine sediments, calcareous nannofossils, late Eocene, Oligocene, biochronology, evolution, morphometry, taxonomy, ODP Leg 199 Site 1218, paleo-equatorial Pacific Ocean
National Category
Geology
Research subject
Marine Geoscience
Identifiers
urn:nbn:se:su:diva-27600 (URN)978-91-7155-890-9 (ISBN)
Public defence
2009-06-15, William-Olssonsalen, Geovetenskapens hus, Svante Arrhenius väg 8 A, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
Doctoral Thesis in Marine Geoscience at Stockholm University, Sweden 2009Available from: 2009-05-25 Created: 2009-05-08 Last updated: 2009-05-26Bibliographically approved

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