203 THE STRATIGRAPHY OF THE LOWER MARINE SERIES OF THE PERMIAN SYSTEM IN THE HUNTER RIVER VALLEY, NEW SOUTH WALES. By G. D. Osborne, D.Sc, Ph.D., Reader in Geology, University of Sydney. (Two Text-figures.) [Read 28th September, 1949.] Contents. Page. Introduction 203 The Lower Marine Series 205 Geographic Distribution 205 Areas of Regional Development 206 Relations between the Lower Marine Series and the Kuttung Series 206 Palaeogeographical Setting 206 Stratigraphy of the Lower Marine Series . . 207 The Lochinvar Stage 207 The Allandale Stage 210 The Rutherford Stage .* 213 The Farley Stage 216 The Lower Marine Rocks of the Cranky Corner Basin . . , 217 The Lower Marine Rocks of the Muswellbrook District . . 218 Correlations of Sections 218 Summary of the Stratigraphy 220 Possible Underground Extensions of the Lower Marine Series 220 Lists of Fossils 221 References 222 Introduction. During several field seasons between 1939 and 1946 the stratigraphy of the Lower Marine Series in the Middle and Lower Hunter Valley has been examined and carefully measured. This series has not received much detailed field investigation in the past, although it has been the subject of much discussion and correlation by stratigraphers and palaeontologists. The chief aim of the writer has been to establish, as completely as possible in the time available, the detailed succession in many areas, and to study the facies variation from place to place. Numerous sections have been measured, and some correlation of these has been attempted. Much information concerning the structure of the Lower Marine Series has accrued from the field-study, particularly concerning the area between Bishops Bridge and Ravensfield, and also in the Pokolbin district, but the writer does not intend to discuss tectonics beyond the mention of certain structural relations between the various stages of the Lower Marine, where the consideration of these relationships assists in an understanding of the stratigraphy. The tectonic evolution of the Lochinvar Dome, and particularly the special character of the Pokolbin section of the Dome, are matters of no small importance in any structural survey of the region, and these subjects will be reserved for separate communication. The field-work occupied about twelve weeks and during this aggregate period approximately 500 carefully selected samples were obtained. Apart from a considerable amount of work on foot, about 1500 miles of traverse were made along transport routes. Some general idea of the geographic distribution of the various stages is obtainable from inspection of the accompanying map (Text-fig. 1).