King, David James; (2019) Evolution and extinction in the Miocene planktonic foraminiferal genus Paragloborotalia, and the importance of the Caribbean in planktonic foraminiferal taxonomy and biostratigraphy. Doctoral thesis (Ph.D), UCL (University College London).

Abstract

Planktonic foraminifera are ideal candidates for evolutionary and extinction studies thanks to their small size, limited stratigraphic range, abundance in oceanic sediments and exceptionally complete fossil record. This thesis falls naturally into two parts. The first part discusses the Miocene component of Paragloborotalia, a genus important in biostratigraphy and evolution, and giving rise to a number of modern-day genera. However, until now Paragloborotalia was poorly understood, and existing data showed conflicting interpretations. Through the integration of historically important material, sample residues from multiple global sites and an extremely thorough review of the literature, one of the most comprehensive resolutions of a planktonic foraminiferal genus has been reached. All 11 Miocene ranging paragloborotaliids are still considered valid, including the highly problematic Paragloborotalia mayeri and Paragloborotalia siakensis morphotypes with the only consistent means to differentiate being the spiral sutures (curved in mayeri vs radial in siakensis). Three species are recognised as being useful in low latitude Oligo-Miocene biostratigraphy (kugleri, pseudokugleri and siakensis), although a coiling change within mid Miocene Subzone M5b (~15.32 Ma) is a useful bioevent. The second part of this thesis focuses on the importance of the Caribbean in Oligo-Miocene planktonic foraminiferal taxonomy and biostratigraphy. The region accounts for the description of over 100 species and the first major planktonic foraminiferal biozonations. Previous work predominantly took place between 1950-1969, and an effort has been made to integrate these findings with the modern taxonomic and palaeoecological understanding through the restudy of type specimens and residues, as well as other important material. A focus has been paid to species with a less certain taxonomy, due to issues with the holotype or lack of type specimens, while the original biozonations applied in the region have been correlated to the modern day biochronology to assess the robustness of the bioevents applied.

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