Tertiary Non-marine Diatoms from Eastern Australia : Descriptions of Taxa D. p. THOMAS and R. E. GOULD Thomas, D. P., & Gould, R. E. Tertiary non-marine diatoms from eastern Australia: descriptions of taxa. Proc. Linn. Soc. N.S.W. 105 (1), (1980) 1981: 23-52. Non-marine diatomites from eleven localities ii> New South Wales and southeastern Queensland, ranging in age from Late Oligocene to Middle Miocene, have yielded twenty-nine taxa of diatoms (Bacillariophyta) which are figured here. Genera present include Melosira, Fragilaria, Synedra, Eunotia, Achnanthes, Cymbella, Gomphonema, Navicula, Pinnularia, Stauroneis, and Nitzschia. Nax/icula seminuloides Hustedt var. rhombica Thomas is recognized as a new variety. Effects of diagenetic dissolution and re-deposition of silica on frustular morphology are discussed and illustrated. Sponge spicules (Porifera : Spongillidae) are present in all diatomites examined and some examples of these are figured. D. P. Thomas, Botany Department, University of Tasmania, Hobart, Australia 7001, and R. E. Gould, Santos Ltd, North Adelaide, Australia 5006 (both formerly Department of Geology, University of New England, Armidale) ; manuscript received ZOfuly 1979, accepted in revised form 20 August 1980. Introduction Beds of non-marine diatomite and other lake sediments are widely associated with Cainozoic and generally basaltic lavas in eastern Australia (Crespin, 1947) . Many of the lavas have been isotopically dated (e.g. Wellman, 1974, 1978; Wellman and McDougall, 1974) enabling relative geological ages to be assigned to deposits that are widely separated geographically. The deposits in New South Wales and south-eastern Queensland that we have investigated (Fig.l), have been assessed geologically by Herbert (1968) and Bonner (1950, 1951, 1953). Skvortzov (1937) detailed the fossil diatom flora from the Middle Flat deposit near Cooma, and Crespin (1947) listed species from most localities. Hill et al. (1970) figured three specimens from the south-eastern Queensland deposits. In this paper we discuss the taxonomy and illustrate the morphology of diatom frustules from selected Oligocene and Miocene diatomites in south-eastern Queensland and New South Wales. The majority of fossil taxa observed are represented in living assemblages, so lessening reliance on the relatively sparse literature on fossil non-marine diatoms (e.g. Andrews, 1971; Abbott and Van Landingham, 1972) ; our identifications, principally the work of DPT, are based upon reference to European and North American taxonomic works that include both extant and fossil forms (e.g. Hustedt, 1930a, 1959, 1966; A. Schmidt et al, 1874-1959; Patrick and Reimer, 1966, 1975). Our conclusions on environments of deposition, geological history of non-marine diatoms, and biostratigraphic implications follow in a second paper (Thomas and Gould, 1981) . The diatomites were probably formed in slightly eutrophic freshwater lakes. Materials and Methods Diatomite samples were obtained from adits and cuttings at known localities. Lump samples were removed from exposed surfaces at intervals of 0.1 to 1.0 m and from any layers in between which differed visually from those above and below; an Proc. Linn, Soc. N.S.W. , 105 (1), (1980) 1981
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