Abstract
Abstract. The major agglutinated constituents in test material of marginal marine foraminifera are identified as α-quartz and clay particles using complementary spectroscopic techniques. Electron dispersive scattering analysis, micro-laser Raman and Fourier transform infrared (FTIR) spectroscopic techniques revealed detail about elemental and mineral polymorph constituents in test walls. Additionally, FTIR identifies the existence of organic cements and lining materials in wall structures. Micro-laser Raman specifically characterized the titanium oxide mineral, anatase, as a distinctive fraction of agglutinate in Ammobaculites balkwilli Haynes. The mineral represents ≈10% of the test material, but comprises a minor component of the sediment and is identified in sediments only after heavy mineral separation. The enhanced concentration of anatase in the test of A. balkwilli suggests that there is a preferential selection for anatase. This provides further evidence that certain foraminifera can select grains specifically, which implies that there exists a selective mechanism and interaction between the organic (secreted) phases in the test walls and inorganic (grain surface) materials.
Highlights
Few biochemical and mineral microprobe investigations have been completed on agglutinated foraminifera, previous microprobe studies have successfully revealed information about the mineral content and the nature of mineral polymorphs present in test walls (Towe, 1977; Lefurgey, 1978; Vknec-Peyre & Jaeschke-Boyer 1978, 1979; Weiner & Erez, 1985; Gooday et a/., 1994; Roberts & Murray, 1995)
Scanning electron microscopy Scanning electron microscopy of the foraminifera indicates that all the specimens selected have detrital grains as the main constituent of the wall structure
Detrital grains in the test walls of T. injlata, J. macrescens and M . fusca are approximately < 1 4 p m in size and are representative of the clay- to silt-sized portion of the sediment, whereas specimens of A . balkwilli have coarser grains in the size range 10-50 pm, which are representative of the silt-sand-sized portion of the sediment (Plate 1, figs 4, 8)
Summary
Few biochemical and mineral microprobe investigations have been completed on agglutinated foraminifera, previous microprobe studies have successfully revealed information about the mineral content and the nature of mineral polymorphs present in test walls (Towe, 1977; Lefurgey, 1978; Vknec-Peyre & Jaeschke-Boyer 1978, 1979; Weiner & Erez, 1985; Gooday et a/., 1994; Roberts & Murray, 1995). The development of more sophisticated analytical techniques provides high spatial resolution to zz 2 pm, allowing the identification of the precise inorganic polymorphs used and secreted by foraminifera in test construction (Roberts & Murray, 1995). These data are of crucial importance as the microstructural nature of wall structures for example, the ~. The three spectroscopic techniques applied vary in the way that they interact with sample surfaces, enabling the acquisition of a variety of data (Fig. 1) These analytical techniques allowed the identification of the nature of inorganic and organic components in the test walls of foraminifera. This paper characterizes material in the agglutinated walls and discusses evidence for specific particle selection on the basis of mineralogy by foraminifera
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