The Stratigraphic Palynology of the Namoi River Valley, Baan Baa to Boggabri. Northern New South Wales Helene a. Martin Martin, H. A. The stratigraphic palynology of the Namoi River Valley, Baan Baa to Boggabri, Northern New South Wales. Proc. Linn. Soc. N.S.W. 114(1): 45-58(1994). The palynostratigraphy of bores sunk for water exploration shows that the alluvial fill is late Miocene-earliest Phocene and remarkably similar to all the major river valleys ^ of the western slopes. The basement, where encountered, is Stage 5 of the Permian. The vegetation of the Late Tertiary was a mosaic of rainforest with araucarians and sclerophyllous forests with Myrtaceae and/or Casuarinaceae dominant. In latest Pliocene/Pleistocene, the forest became more open. H. A. Martin, School of Biological Science, University of New South Wales, P.O. Box 1, Kensing-ton, N.S.W., 2033; manuscriptreceived 17 Junel992, accepted for publication 16 November 1992. Introduction Numerous shallow bores have been sunk in the alluvial fill of the valleys of the Western Slopes by the New South Wales Department of Water Resources in the search for ground water. This paper records the palynology of some of the bores in the Baan Baa-Boggabri region of the Namoi River Valley and its tributary, Coxs Creek (many bores do not yield pollen). The Late Tertiary history of the vegetation is compared with that of other river valleys of the Western Slopes. The age of the preTertiary basement, where encountered, is reported also. Methods and Materials The samples used in this study are cuttings, as cores were not taken. The possibility of contamination is greater with cuttings than with cores, but with care and appropriate procedures, relatively clean cuttings may be produced. For investigative drilling, from 1.5 to 4.6 m is drilled and then the mud circulated until clean of the coarse fraction. This practice minimises carry-down. Cavings, where sediments higher up may break away from the side of the borehold and be incorporated with cuttings from deeper levels, may be detected by different colours or other properties. While the possibility of contami-nation in cuttings can never be ruled out, experience has shown that cuttings may produce reliable results. Consistent patterns, repeated in bore after bore, would not be possible with appreciable contamination (Martin, 1993). Preparation techniques used hydrochloric and hydrofluoric acids to remove the mineral material, controlled oxidation with cold Schultz solution, and potassium carbonate to clear the residues. Geology The valley fill rests on a basement of Permian and Jurassic sandstones, shales, conglomerates, tuff, coal, limestone and volcanics. The older sediments are uncon-solidated and frequently cannot be identified apart from the Tertiary fills, without palynological evidence. For location of bores, see Fig. 1. The alluvium consists of a clays, silts, sands, and occasionally gravels. Only the grey-coloured clays and silts yield pollen. PROC. LINN. Soc. N.S.W., 114(1), 1994
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