PAPERS AND PROCEEDINGS OF THE ROYAL SOCIETY OF TASMANIA, VOLUME 96 THE PERMIAN SYSTEM IN WESTERN TASMANIA By MAXWELL R. BANKS University oj Tasmania and N. AHMAD University oj Aligarh (With 12 text figures.) ABSTRACT OCCURRENCES of PERMIAN ROCKS Permian rocks occur at Mount Read, Mount Dundas, Mount Sedgwick, Zeehan, Firewood Siding, in Strahan and Point Hibbs in Western Tasmania. The basal formation is exposed at Mount Read, WESTERN TASMANIA Mount Sedgwick, Zeehan and Point Hibbs and consists of tillite. Striations on the basement at Mount Sedgwick indicate ice moving from the west. Sections up to and including the Golden Valley Group (Lower Artinskian) occur at Mount Sedgwick and Point Hibbs and a section from the e MOUNT READ Mersey Group up to and including the Cygnet Formation is found in the Firewood Siding Area near the mouth of the Henty River. The sections at Mount Sedgwick and Firewood Siding are much thinner than corresponding ones in north-western and south-eastern Tasmania but that at Point Hibbs is as thick as or thicker than corresponding sections. INTRODUCTION The first record of Permian rocks in the area studied seems to be ·that of Montgomery (1891) who made brief reference to coal on the Henty River (see map, fig. 1). Johnston (1892) recorded some fossil plants from the Henty River area and correlated the coal measure there with the Mersey Coal Measures. In 1894 Dunn noted the tillite near Mount Read and commented on its similarity to the Dwyka of South Africa and to the conglom­ erates at Wild Duck Creek (DerrinaD, Victoria. In the same year Moore noted ·the Permian fossil­ iferous and glacial beds on Mount Sedgwick and those at Zeehan (Zeehan Tillite) which he also described as Permian. The fluvio-glacial beds near Strahan were first described by Officer, Balfour and Hogg (1895). Several later workers dealt with the deposits mentioned above but no new work was added until Hills (1914) dealt with the Point Hibbs section. In 1925 Reid noted the probable POINT presence of Permian rocks on Mount Dundas. SCALE :- Voisey (1938) included references to this area, o 10 .20 MILES particularly to the Point Hibbs and Malanna ! ==' sections in his work on the Permian of Tasmania. Edwards (1941) noted the exhumed Permian FIGURE' surface on Mount Sedgwick and the Permian of 1 R.S.-2. 2 THE PERMIAN SYSTEM IN WESTEHN TASMANIA Mount Sedgwick was mentioned by Bradley (1954) Zeehan about half a mile south of the "L" Lode Some of the Permian rocks at Firewood Siding, open cut on the south-west slde of Mount Hamilton, near Malanna, were described by Gill and Banks tillite was found in a small depression (co-ordinates (1950). Campana et al (1958) and Spry (1958) 8.5 cms. S.S.W. by S. of C.P., Zeehan 8, 23627) re-establisbed the Permian age of the Zeehan (;see map, fig. 2). Tillite. Others have also commented on the Per­ The Permian rests on "sheared pyroclastics" of mian rocks considered in this paper but only as probable Cambrian age which have a steep easterly repetitions of earlier worlL dip and the Permian has a horizontal fissility of the Permian sections in although no bedding could be seen. The rock is November, when Professor greenish grey. It is sorted with boulders ProfessOl' the University to 18 inches (clay and G. and lVL R. Banks spent a p;radc) matrix. and sections in the Malanna area. In . and 1957, the authors measured sections in Point Hibbs and on Mount bJack slate, and observations on the Permia~l The rock is Mount Re8~d and at Strahall. m'obably not more two feet the trip to Iv'lalanna sections were t,hiek allcl is a small remnant preserved in a hollow Guttings ami creek beds hills of " sheared " which rise level. The Mount to more than 50 above the level of the was 'J'here is no internal evidence in exposure a Permian age. The was measured a, steel degree lithifieation are similar to of the vertical reading PCl'TIl.ian ti.lIitee:; elsewhere State and nesses until the fault zone was met and dissimilar from those of Pleistocene then using the abney level. Thicknesses in the section near rvfaJanna, studie:i SOME PERf\1IAN in 1957, clue to thick under- growth. ON MOUNT READ work tho authors were "Jc.ed on the route to MounL geologists of the Mount also made available services who was of considerable Exploration Hibbs Dossible by authors one each Vilay and Jater made The Zinc and Druett available as a guide. The authors acknow­ with grat,itude the assistance of these com­ and their officers. The authors are also PHOTO to Mr. M. Longman, Geologist at the PRINe IPAL POINT Tasmanian Museum for access to plant shaces from which Johnston had described plants from the Henty River. All bearings are related to true north. MOUNT READ. The earliest mention of Permian rocks near Mount Read is that of Dunn (894) who mentioned a conglomerate with a great variety of pebbles on the south side of the track half way from Mount Read to Moore's Pimple. He remarked on its similarity to the Dwyka of South Africa and the conglomerate on Wild Duck Creek (Derri­ liMIT nal), Victoria, both considered as Permian. Hills OF PERM/.A..N (1915) gave further details. He considered that it was Permian as it contained fragments of undoubted "Silurian" rocks (now known to be Ordovician) Bradley (1954, p. 199) also mentioned this occurrence as showing that the Carboniferous peneplain in this area has an undulating surface SCALE o 20 40 fiO 80 CHAINS with variations up to 80 feet in height. ,~~~~~ ~-==------..L.--.-...-__------d A complete survey was not made by the present authors but ,two areas 'Of Permian rocks were Based on air photo Z",,,,han Run e no. 23627 examined. On the track from Mount Read to FlGURE :2 MAXWELL R. BANKS AND N. AHMAD 3 the West Coast area. The top of the plateau at 0956. p. 193) regarded the age of the Zeeban Mount Read shows no sign of Pleistocene glaciation Tillite as not then established. More recently so that all available evidence from this outcrop Spry (1958) has suggested that the Zeehan Tillite suggests a Permian age. is Permian on structural grounds and because it The Permian age is confirmed by the other contains fragments of Dundas Group and Eldon ox:posure of tillite and associated rocks. In a Group rocks. He has al::;o found a further occur­ hills of "sheared pyroclastics" rence of it no1'[,h of the Pieman River and describes of a mile sout.h-west of "L" the rock from the dIfferent areas in some detail. tillite is found, on the The authors did not visit these areas. (at point 10 ems. 8,S.E. by of C.P, and King (1958) give detailed evidence ,","'CO"""''' 8, 23627) and in a runnel of an old track Permian age for the Zeehan Tillite. a surface of the pyroclastics shows a surface wIth striations trending 0 0 SECTION AT IV/ALANNA (MOUTH OF This may be part of the pavement HENTY RIVER). Permian this not. be established the may be due to The Permian rocks here were first noted by in this reached a (1891, p. 42) who gave the section as of 33 and in addi1;ion to 'c"",n,-,.,eh,,d beds overlain by sandstones and lime- from the first locality include a marine fossils and white grit or Otherwise the tillite at this second Johnston 'l-If' Qo"n mtm',,< is very like thai; from the first" About Go 100 yards north-east this track (at point with curious with co-ordinates 9.7 ems, of C,P. Zeehan 3, botryoidal concretions the coal bearing beds 23627) olive-grey siltstones are exposed dipping at and correlated them with the Coal Measures. a moderate angle to the west off a small hillock of Twelvetrees (1902a) noted that imnure lime- "sheared pyroclastics", 'Thes,eare well-sorted in stones and mUdstones overlie the coa( measures. that erratics aTe rare and small. They are poorly Twelvetrees (1902b, 1903) recorded details of two bedded. These siltstones contain articulated crinoid bores put down near Malanna in a search for coal columns and attached cirri of a type common in and (1902, p, lxxii) that the coal occurred the Permian System in Tasmania. The siltstones on two one exposed near Malanna and overlain by ti.1litic material and similar silt- the other below the limestone. Voisey ( p, occur above the tillitic material, :322) considered that one formatIon vU"""'U''''", further the track and are coal was that the beds with marine lain by tillitic On fossils. this was infl.uenced by the it seems probable that the tillite, undoubted presence of or carbona.ceous siltstone with crinoids, siltstone, tillite, but beds above the marine beds in sec- view of the poor exposure succession cannot tions. However, investigations by the as established. The of the suggest ,that there are two coal bearing formations of Permian type age of by marine beds. 'The authors were unable the succession. of the" curious botryoidal concretions" The surface of the plateau north and eact of in the cuttings nor any Noeggerathiopsis these occurrences was not examined and there may and it is clear from Montgomery's statement (1891, be further outcrops. The two areas of Permian p. 4:3) that the coal being investigated was on the rocks found occupied small depressions in the flats just north of the Henty River. not as far surface of the "sheared pyroclastics" which rises north as the railway cutting.