 |
|
|
|
|
|
 |
New Zealand Journal of Marine and Freshwater Research abstractsGLAUCONITIC COATING ON A GASTROPOD, FUSITRITON LAUDANUM, FROM THE CHATHAM RISE, NEW ZEALAND (NOTE)G. P. GlasbyNew Zealand Oceanographic Institute, Department of Scientific and Industrial Research, Wellington, New ZealandAbstract Superficial coatings of glauconite grains have been observed on the gastropod mollusc, Fusitriton laudanum, from the Reserve Bank, Chatham Rise. The glauconite predates the shell on which it accretes and is incorporated on to the shell surface by agglutination of sand-size material by mucus secreted by epizoic anemones.During a recent survey of NZOI biological samples, a superficial black coating of glauconite grains was noticed on shell fragments from several sites on the Reserve Bank, Chatham Rise, New Zealand (Fig. 1). The glauconite coatings are restricted to material from seven dredge stations on the Reserve Bank. Station D119 contains one live Fusitriton laudanum displaying a limited superficial black coating. Station D121, on the other hand, contains masses of polychaete worm tubes, ascidians and barnacles (Balanus) with quantities of sub-fossil F. laudanum and other gastropods (e.g., Coluzea spiralis, Galeodea sp., Iredalina mirabilis, Penion and Xenophalium). The black surface deposit occurs principally as a thin nodular coating, up to 3 mm thick, overlying a mat of colonial coelenterates, probably epizoanthids, on the surface of F. laudanum (Dr E. J. Batham pers. comm.). Usually, this surface coating covers most of the exposed outer surface of the gastropod (Fig. 2). Stations A891, A892, A899, A900 and A901 contain large actiniarian sea anemones with thin, poorly defined black surface coatings which occur mainly in depressions on the surface of the animal. Quantities of black sand-size material are also observed in the mouth of the anemone. Petrographic, X-ray and chemical analyses of the superficial surface coatings indicate the presence of glauconite as the principal mineral phase, with smaller amounts of calcite, fine-grained apatite, and sponge spicules as impurities (Table 1). The higher Ca and P and lower Si, Al and Fe concentrations of the present sample compared with those previously reported for glauconite from this area (Norris 1964: p, 23, Table 2) reflect the presence of these impurities. X-ray diffraction analysis of the sample showed the presence of two glauconite peaks at d (001) = 10 A (1 nm) and d = 4.52 A (0.452 nm) in agreement with previous mineralogical data for glauconite from this area (Bell and Goodell 1967). According to these authors, glauconite from Chatham Rise is characterised by poor crystallinity.
N.Z. Journal of Marine and Freshwater Research 6 (3): 383-6
PDF file of entire paper: medium quality (557K); (scanned from paper original: notes about this process) This year's abstracts | Journal home page | All abstracts | Publishing home page |