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Smear and spray preparation techniques put to the test (II): reproducibility and accuracy of calcareous nannofossil assemblage counts
Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
2007 (English)In: Journal of Nannoplankton Research, ISSN 1210-8049, Vol. 2, 92-100 p.Article in journal (Refereed) Published
Abstract [en]

In an earlier study (Henderiks and Törner, 2006, Marine Micropaleontology 58, 207-218), nannofossil proportion estimates between replicate smear slides showed substantially higher variance than those obtained from replicate sprayed slides. This study revisits this potentially disconcerting issue, detailing the internal accuracy and reproducibility of relative nannofossil species abundances obtained with the same two preparation techniques: the simple smear slide and the spray method. In addition, accuracy and reproducibility were tested for a semi-quantitative method, in which the number of specimens per mm2 is determined from smear slides.

To test the overall reproducibility of these two preparation methods, replicate slides were prepared and analyzed with each technique for a set of six samples selected from Oligocene deep-sea sediments from the Equatorial Pacific (ODP Leg 199). Both smear and spray replicates indicate a good reproducibility of proportion estimates within the same method, since no statistically significant differences between the replicate slides were observed. However, when comparing the smear with spray replicates, the data set reveals significantly different species proportion between slides, indicating that the two preparation techniques are not statistically comparable. It appears that the dominant taxon, Cyclicargolithus floridanus, is enriched in the smear slides, whereas the abundance of the subordinate taxa is about the same for either method. A comparative test of abundance counts between dense and thin areas on the same smear slide indicates nannofossil size sorting in the smearing technique, with proportionally more large specimens in the dense ripples. This study confirms an earlier observation that the smear method results in lower proportion estimates of larger nannofossil taxa in comparison to the spray method.

Place, publisher, year, edition, pages
UK: Cambridge University Press , 2007. Vol. 2, 92-100 p.
Keyword [en]
calcareous nannofossils, preparation techniques, light microscopy, accuracy, reproducibility, biostratigraphy
National Category
Geology
Research subject
Marine Geoscience
Identifiers
URN: urn:nbn:se:su:diva-27589OAI: oai:DiVA.org:su-27589DiVA: diva2:216395
Available from: 2009-05-08 Created: 2009-05-08 Last updated: 2009-05-11Bibliographically 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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