Composition and structure of foraminiferal agglutinated test walls

• Main Author: Allen, Kathryn
• Format: Thesis
• Language: English
• Published: University of Southampton 1998
• Subjects: Antarctic; Antarc*
• Online Access: https://eprints.soton.ac.uk/463556/

This thesis describes a study of test wall components of agglutinated foraminifera using various high resolution techniques. Laser Raman and FTIR microprobe investigation of test walls in Antarctic shelf agglutinated foraminifera identifies those possessing monomineralic, and also those with several mineral phases, of agglutinate which suggest that, in certain cases, processes of grain selection appear to be functioning. Organic cements exist in all forms studied, confirmed by Scanning Electron Microscopic (SEM) investigation and Fourier Transform Infrared (FTIR) spectroscopy. Using the same techniques marginal marine foraminifera are found to have clay-silt sized agglutinate, in association with abundant organic components. Combination of Electron Dispersive Scattering (EDS) and laser Raman microprobe analysis identifies that Ammobaculites balkwilli agglutinates anatase, a mineral rare in surrounding sediments, and not identified in other species, additionally suggesting specific grain selection processes. A self similar, fractal distribution of grain size is identified in test walls of Hormosina mortenseni. Cyclammina cancellata also has a self similar internal grain distribution, showing variation of external grain arrangement, indicating that construction processes vary. Computer simulation is used to investigate processes of grain fitting and arrangement. Results show that grain selection criteria are operating during production of self similar shell walls, and definitely during the formation of smooth outer layers as seen in C. cancellata. Species of Arabian Gulf foraminifera possessing black and white test colouration have a similar carbonate composition. Black forms display features suggesting early onset of diagenesis; infilled cavities, and lower proportions of aragonite. FTIR investigation does not reveal variations of organic materials present in test types, indicating that these materials are not denatured, and hence not a factor influencing test colouration. No evidence can be found for metal ...