Geochemical proxy records of sea surface environmental conditions at Blake Nose indicate short-term high amplitude variations. In order to investigate the response of calcareous nannoplankton to these short-term sea-surface environmental changes, we developed a high-resolution Eocene planktonic foraminifera Mg/Ca record and calcareous nannofossil absolute abundance record for ODP Site 1052 spanning the late middle Eocene (37.85 to 37.45 Ma). These data enable direct comparison of the absolute nannofossil abundance data to geochemical paleoenvironmental proxies (Mg/Ca, ?18O and ?13C) to determine the phytoplankton response to paleoenvironmental change and whether temperature or nutrient levels exerted primary control. The nannofossil absolute abundances were estimated using a combination of the random settling technique (RST) and spiking method (SM), which are two independent methods. Both methods yielded similar and reproducible results. The calculated Mg/Ca paleotemperature record indicates a decrease in SSTs from ~33 to 28�C, while the ?18Osw values calculated from the Mg/Ca paleotemperature also decreased from ~3? at 37.83 Ma to ~2? at 37.6 Ma. The combined trends of the SST and ?18Osw suggest that continental ice did not have a major influence on the climate during the study interval. Variations in the Gulf Stream (e.g. track of proto-Gulf stream, number and transit of eddies, and Gulf Stream related upwelling), may have contributed to the reconstructed sea surface hydrographical changes at Blake Nose. However, overall weakening of the hydrological cycle as global climate transitioned from a greenhouse to an icehouse could be the major factor controlling the hydrographical changes at Blake Nose. Approximately 48 nannofossil taxa were identified in this study. These taxa have been grouped into major, minor and rare taxa based on their abundance in any given sample. Results of the statistical analyses (canonical correspondence analysis CCA, Cluster analysis, and correspondence analysis CA) used to relate the nannofossil abundance to environmental parameters did not show expected relationships between the nannofossil absolute abundance and environmental parameters. There are several explanations for this which includes dominance of biotic control over abiotic control, difference in depth habitats between the planktonic foraminifera used for the geochemical proxies and the calcareous nannoplankton, and changing combinations of environmental controls operating during the ~400 ky interval. This suggests that these factors should be taken into account when making conclusions about nannofossil environmental preferences.

Geochemical proxy records of sea surface environmental conditions at Blake Nose indicate short-term high amplitude variations. In order to investigate the response of calcareous nannoplankton to these short-term sea-surface environmental changes, we developed a high-resolution Eocene planktonic foraminifera Mg/Ca record and calcareous nannofossil absolute abundance record for ODP Site 1052 spanning the late middle Eocene (37.85 to 37.45 Ma). These data enable direct comparison of the absolute nannofossil abundance data to geochemical paleoenvironmental proxies (Mg/Ca, ?18O and ?13C) to determine the phytoplankton response to paleoenvironmental change and whether temperature or nutrient levels exerted primary control. The nannofossil absolute abundances were estimated using a combination of the random settling technique (RST) and spiking method (SM), which are two independent methods. Both methods yielded similar and reproducible results. The calculated Mg/Ca paleotemperature record indicates a decrease in SSTs from ~33 to 28�C, while the ?18Osw values calculated from the Mg/Ca paleotemperature also decreased from ~3? at 37.83 Ma to ~2? at 37.6 Ma. The combined trends of the SST and ?18Osw suggest that continental ice did not have a major influence on the climate during the study interval. Variations in the Gulf Stream (e.g. track of proto-Gulf stream, number and transit of eddies, and Gulf Stream related upwelling), may have contributed to the reconstructed sea surface hydrographical changes at Blake Nose. However, overall weakening of the hydrological cycle as global climate transitioned from a greenhouse to an icehouse could be the major factor controlling the hydrographical changes at Blake Nose. Approximately 48 nannofossil taxa were identified in this study. These taxa have been grouped into major, minor and rare taxa based on their abundance in any given sample. Results of the statistical analyses (canonical correspondence analysis CCA, Cluster analysis, and correspondence analysis CA) used to relate the nannofossil abundance to environmental parameters did not show expected relationships between the nannofossil absolute abundance and environmental parameters. There are several explanations for this which includes dominance of biotic control over abiotic control, difference in depth habitats between the planktonic foraminifera used for the geochemical proxies and the calcareous nannoplankton, and changing combinations of environmental controls operating during the ~400 ky interval. This suggests that these factors should be taken into account when making conclusions about nannofossil environmental preferences.

Previous biostratigraphic studies in the Indian Ocean, equatorial Pacific, Atlantic Ocean and the Caribbean Sea document the temporal disappearance of Reticulofenestra pseudoumbilicus in the late Miocene (Tortonian age). This interval has been subsequently defined as the R. pseudoumbilicus paracme. While the cause of the event remains unknown, the geographical extent and global synchronicity of the interval represent an open subject for research. Answers to these questions could help establish the biostratigraphic reliability of the interval and its use for global correlation. In this study, 49 deep-sea drilling sites spread across all major ocean basins were compiled into a biostratigraphic database and studied to evaluate the global extent and timing of the R. pseudoumbilicus paracme. To ensure accurate comparison of the studied sites, the timing of the event was estimated at all sites using the age estimates generated through Undatable MatLab software, which made use of established nannofossil bioevents as age-depth tie points for the analysis. Ages of all nannofossil bioevents were updated to the latest geological time scale. This systematic analysis reveals a prominent distribution of the paracme in the tropical and subtropical regions. The timing of the event in the tropical region appears to be synchronous, with the base around 8.8 Ma and the top of the event around 7.2 Ma. Sites in the equatorial Pacific, central Atlantic and the Indian Oceans record a similar duration of the event. The paracme had a shorter duration towards the southern higher latitudes. Although timings in southern high latitudes are diachronous compared to the tropics, the duration is consistent between sites (Sites 1088 and 1264) in the southern South Atlantic, thereby establishing a new time frame for the event in the region. This study narrows down on ODP Site 806 for a critical evaluation of the nannofossil assemblages, accumulation rates and Reticulofenestra size variation in the late Miocene, including the paracme. Thirty-four samples were collected and analysed for absolute abundance and nannofossil accumulation rates (NAR). Absolute abundance and NAR reveal three distinct stages, herein described as generally low, high, and “crashed” export production of nannofossils. The period of high NAR is characteristic of the late Miocene biogenic bloom interval (ca. 9–4.4 Ma). Importantly, the R. pseudoumbilicus paracme does not only coincide with the start of the biogenic bloom but it was also associated with remarkable changes in Reticulofenestra assemblages. Just before the base of the paracme, all except the smallest (&lt;3 µm in coccolith size) Reticulofenestra groups experienced a sharp decline in abundance. Subsequently, the relative abundance of the Reticulofenestra morphospecies indicates the dominance of bloom-forming small and medium Reticulofenestra during the late Miocene biogenic bloom interval. The end of the biogenic bloom interval is concurrent with a decrease in the contribution of small Reticulofenestra. The exact biotic and abiotic processes that led to these major shifts in plankton composition are yet to be discovered, but the findings presented herein show that the mechanisms behind the temporary disappearance of R. pseudoumbilicus in the tropics most likely involved the interplay between a broad range of ecological changes and evolutionary processes affecting the Reticulofenestra assemblages. / <p>The work for this thesis was financially supported by the Erasmus Mundus Joint Master Degree PANGEAprogramme.</p>

<p>The Geologic <i>TimeScale Creator </i>(TSCreator) project has compiled a range of paleo-environmental and bio-diversity data which provides the opportunity to explore origination, speciation and extinction events. My PhD research has four major interconnected themes which include the visualization methods of evolutionary tree and the impacts of climate change on the evolution of life in longer and shorter timeframes: <b>(1) </b>Evolutionary range data of planktonic foraminifera and nannofossils over the Cenozoic era have been updated with our latest geological timescale. These evolutionary ranges can be visualized in the form of interactive, extensible evolutionary trees and can be compared with other geologic data columns. <b>(2) </b>A novel approach of integrating morphospecies and lineage trees is proposed to expand the scope of exploration of the evolutionary history of microfossils. It is now possible to visualize morphological changes and ancestor-descendant lineage relationships on TSCreator charts which helps mutual learning of these species based on genetic and bio-stratigraphic studies. <b>(3) </b>These evolutionary datasets have been used to analyze semi-periodic cycles in the past bio-diversity and characteristic rates of turnover. Well-known Milankovitch cycles have been found as the drivers of fluctuations in the speciation and extinction processes. <b>(4) </b>Within a shorter 2000-year time period, global cooling events might have been a factor of human civilization turnover. Using our regional and global cultural turnover time series data, the effect of climate change on human culture has been proposed. The enhancement of the evolutionary visualization system accomplished by this research will hopefully allow academic and non-academic users across the world to research and easily explore Earth history data through publicly available TSCreator program and websites. </p>