83 A NOTE ON THE STRATIGRAPHY AND STRUCTURE OF THE WELLINGTON-MOLONG-ORANGE-CANOWINDRA REGION. By Gebmaine Joplin, B.A., D.Sc, Ph.D., and Others. (Plate i and two Text-figures.) [Read 30th April, 1952.] Synoi)sis. Reconnaissance mapping-has been carried out over an area of about 2,000 square miles, and it has been shown that Silurian strata have been folded into a great anticlinorium upon which later folding-has been superimposed. The first movement is attributed to the Bowning Orogeny, and the second to the Kanimblan. The Silurian strata have been mapped as the Gamboola, Nanima and Manildra Formations, and there is evidence that the first is of Lower Silurian age. Ordovician, Devonian and Jurassic strata also occur in the area, as well as Tertiary lavas and related intrusions. Granites may be of Kanimbla age. Introduction. The region covered by the map (Plate i) has an area of about 2,000 square miles. Joplin and Culey (1938) published a reconnaissance map of a small part of the area, and subsequent, more detailed mapping has necessitated some modifications, which are incorporated in the present map. The map is a compilation of the work of sixteen people. Six of these workers— Misses E. M. Basnett, M. J. Colditz and E. M. Phillips and Messrs. R. Brewer, D. G. Move and N. C. Stevens— mapped certain areas (see inset) as part of their honours course in the Department of Geology, University of Sydney, and their work has been carried out mainly by compass traverses on parish maps. The work of Basnett and Colditz (1946) and Stevens (1950) is published. Reconnaissance mapping between areas of more detailed mapping has been carried out by Misses M. Breckenridge, A. G. Culey, J. Johnston and G. A. Joplin, and Messrs. T. G. Vallance and K. Sharp, and a part of the work of L. J. Jones (1935), C. A. Sussmilch (1906) and C. A. Sussmilch and H. I. Jensen (1909) has been used to tie the area to already-published work. Although parts of the map are published, it is presented for three reasons: (i) it indicates the regional structure which is not apparent in the maps of isolated areas; (ii) it incorporates work which may not otherwise be published and which may save much time for those undertaking more detailed work in the future; and (iii) the map shows the relation between the Silurian rocks of the Wellington-Molong area and the Ordovician strata to the south (Stevens, 1951). As the general geology of the area is fairly well known from published work, it is proposed only to make amendments and additions to the stratigraphy and to indicate broadly the structure of the area. Stratigraphy. Ordovician. Basnett and Colditz (1946) recorded graptolite-bearing slates surrounded by Silurian andesites at Wellington and at Apsley, and suggested that the Silurian strata were deposited around Ordovician islands. Later Moye found graptolites in slates near Borenore, not far from Lower Silurian limestones (Fletcher, 1950), and recently G. H. Packham* has found Ordovician graptolites near the Nandillyan limestone. Stevens found graptolite slates associated with limestones and andesites faulted against Upper Devonian strata near Cargo and has more recently found Ordovician limestones inter-bedded with andesite on the Belubula River (Stevens, 1951). This discovery raises the question of the age of the andesites and limestones within the area of the present map. I 'ersonal communication.