Southwest Tasmania Research Articles

New evidence from Fraser Cave for glacial age man in south-west Tasmania

The discovery of a rich archaeological occupation site in the Franklin River valley of south-west Tasmania dated at 15–20 kyr BP is described. The stone tools found support the view that the Tasmanian industries were derived from contemporary mainland Australian ones when the two were still connected. Faunal remains from human hunting and cooking activities indicate a hunting strategy targetted at a few favoured species, especially the large wallaby. No extinct megafaunal species were present. During the height of the last ice age, these glacier edge hunters of southern Tasmania were then the most southerly humans on Earth.

The Mammals of the Lower Gordon River Region South-West Tasmania

The terrestrial mammal fauna of the Lower Gordon Basin, a little-known wilderness of western Tasmania, was investigated by means of traps and observations. The occurrence of the species was related to six vegetational structures, reduced from the 17 types recognized by Specht. Eighteen native and one introduced species were found, all of which are widely distributed in Tasmania and which represent 70% of the Tasmanian mammal fauna, including carnivores, insectivores and herbivores. The absence of some species is noteworthy. Fire determines the vegetation structure and therefore the distribution of the mammals. Only one species was abundant, the remainder showing the relatively low density of mammals in this rainforest-sedgeland wilderness.

The South-West Tasmania Wilderness Crisis

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On the Macquarie Harbour Geophysical Anomaly, South-West Tasmania

Attention is drawn to major gravity and aeromagnetic anomalies existing in an area between Macquarie Harbour and High Rocky Point in south-west Tasmania. The correlation of these anomalies is discussed in terms of possible mechanisms for their origin. One postulated mechanism involves movement of crustal blocks relative to west Tasmania and raises the question of the origin of King Island, Bass Strait.

SUBMISSION TO THE SENATE SELECT COMMITTEE ON SOUTHWEST TASMANIA: Evidence presented at Parliament House, Canberra. Extract from Hansard, 19 March 1982

The submission was divided into three sections: 1. The inadequacies of the Gordon River Stage Two Report as regards Aboriginal archaeological remains of the region. 2. A brief account of new archaeological discoveries made in the Gordon-Franklin Rivers region during 1981, and an assessment of their significance. 3. An argument based on prehistoric and environmental data supporting a World Heritage status for Southwest Tasmania.

Recolonisation by bryophytes following fire

The recolonisation of bryophytes on soil during 3½ years following fire in a mixed forest in south-west Tasmania is characterised by the presence of Marchantia berteroana, Funaria hygrometrica, Ceratodon purpureus and Polytrichum juniperinum, while limited cover is provided by Campy lop us introjlexus, Tortella calycina and Bryum sauteri. It has been verified that the protonemal growth of the early colonising mosses is more rapid than non-colonising specles. The preference for spores of Funaria hygrometrica, Ceratodon purpureus and Marchantia berteroana to germinate on burnt soil is confirmed. However, it has been shown that burnt substrates do not inhibit the germination of non-colonising species. Therefore, the rapid development of protonemata and gametophytes in the colonising species may be a critical factor for their success.

Downstream effects of the Gorden River Power Development, south-west Tasmania

A survey of the physicochemical limnology of the Gordon River, designed to provide background environmental data for the proposed stage 2 of the Gordon River Power Development, has, ironically, revealed far-reaching consequences of the dams of stage 1, for which only rudimentary surveys were carried out. An obvious hydrological effect is the damping of seasonal flow variations so that the regulated river experiences higher summer flows and lower winter flows than under natural conditions. River levels are consequently affected and summer growth of photosynthetic algae in former shallows and riffle zones no longer occurs. Other biological effects are unknown. The effective headwaters of the river are now the hypolimnetic strata of a large stratified reservoir, Lake Gordon. Consequently, the river is fed with a relatively constant discharge of water of almost invariable temperature and chemical composition. The effects of influent tributaries downstream are now largely overridden by this constant flow. Temperatures vary little along the length of the regulated river, being above normal in winter and below normal in summer. Chemical variability has been reduced, both in respect of the lower salinity range now experienced and in the suppression of flow-dependent alternation between dominance by sodium chloride or by alkaline earth bicarbonate. An unfortunate hydrological effect is the elimination of an estuarine underflow of salt water on which the meromixis of three lakes depends. While two of them have shown little change in the short time since dam construction, a third became holomictic soon after discharge from the dam commenced. A temporary return to meromixis after a brief shutdown of the power station indicates that an appropriate operating regime, with brief summer shutdowns, could retain the affected lake in a meromictic condition of great scientific interest.

Anomalous stratification behaviour of Lake Gorden, headwater reservoir of the lower Gorden River, Tasmania

Lake Gordon, a large hydro-electric reservoir in south-west Tasmania, holds water of low pH, high colour and low dissolved solids content. It stratifies each year, with consequent anoxia below the thermocline. The nett effect of the inflow pattern, combined with the deep-V morphometry of the reservoir, is to prevent holomixis. For 6 months of the year, the cold inflow of the upper Gordon River follows its old course and rolls down to the dam, intruding first as an underflow, then rising slightly to become an interflow as it warms and finds its density level. This inflow displaces older water upwards, sandwiching the former hypolimnion between the inflow and the epilimnion. The anoxic, sulfuretted water of the sandwiched stratum gradually mixes with water above and below it, leading to its ventilation and dispersion. Meanwhile; the inflowing water stagnates and anoxia develops afresh in bottom waters. This occurs at a time when the upper strata are restratifying, leading to a multiple sandwich of several strata of discrete lineage. The early history of the reservoir indicates that it was predisposed for partial meromixis of the Lake Barrington type, preconditioned by its morphometry and by a mass of flooded vegetation. That a lasting monimolimnetic pool did not form, as expected, is attributable to the annual inflow of dense, oxygenated water. The hypolimnion of Lake Gordon is now the effective headwater of, and greatest contributor to, the lower Gordon River. Because of the stratification pattern, the discharge stratum may be oxygenated or anoxic and laden with hydrogen sulfide, iron and manganese. Any undesirable effects of the latter are rapidly dissipated in a short stretch below the dam, but the relatively invariable nature of the temperature and major ion chemistry of this stratum impose an unwonted uniformity on the river, to its mouth.

Corrigenda - Limnology of Perched Lake, south-west Tasmania

Corrigenda - Limnology of Perched Lake, south-west Tasmania

Limnology of Perched Lake, south-west Tasmania

Perched Lake is one of the few lakes of lowland parts of south-west Tasmania. It is a warm monomictic lake, stratifying for 7-8 months each summer and, unlike most other bodies of standing water in the south-west, is only moderately dystrophic. Oxygen concentrations of the hypolimnion decline late in the stratification period but do not fall below 20% saturation, indicating low areal productivity. Though only moderately dystrophic, there is sufficient organic colour to cause marked attenuation of photosynthetically active radiation, particularly in the blue wavelengths. Its water chemistry is that of dilute seawater. Certain thermal and chemical anomalies are possibly explained by subsurface inflows of artesian water. The plankton of Perched Lake is dominated by chrysophytes and chlorophytes, with no well-defined seasonal change of biomass or species composition. An unusual dinoflagellate with marine affinities. probably Phalacroma sp., occurs in the lake.

Meromictic lakes of south-west Tasmania

Lake Fidler, Lake Morrison and Sulphide Pool are three small, shallow lakes adjacent to the lower reaches of the Gordon River. They are levee lakes, and may be remnants of once more extensive water bodies. Eah of them shows the usual features of meromictic lakes, with a persistent chemocline acioss which the concentration of electrolytes and hydrogen sulfide increases sharply, dissolved oxygen concentration falls to zero, and redox potential changes from positive to negative. In all three lakes the change in electrolyte concentrations takes place over a comparatively thick water stratum, but the redoxcline and oxycline are pronounced, and in their vicinity is a 'plate' of microflagellates and photosynthetic sulfur bacteria, marked by sharp peaks in the profiles of chlorophyll concentration and of turbidity. Their waters are dystrophic, severely attenuating light and limiting plankton populations in the mixolimnia. Photosynthetically active radiation at the depth of the plates of photosynthetic bacteria is considerably less than 1% of surface values. With the chemocline in each case so close to the surface (1.0-2.5 m), and with their shallowness, these are among the most dramatic cases of meromixis yet recorded. Their survival is in doubt because operation of a power station now prevents the entry of estuarine salt on which the state of meromixis appears to depend.

Lithostratigraphy and biostratigraphy of the Florentine Valley Formation in the Tim Shea area, southwest Tasmania

The Florentine Valley Formation is defined. The Formation is subdivided into three members; the Churchill Sandstone Member, the Pontoon Hill Siltstone Member, and the Mt. Field Siltstone Member. Seven consecutive fossil assemblages based on brachiopods and trilobites can be recognised within the Florentine Valley Formation. International correlation of the assemblages in the Florentine Valley Formation is based on graptolites, that of the basal Karmberg Limestone on graptolites and conodonts. The Formation ranges in age from Early Tremadoc to Late Arenig.

Adaptive Technology in Southwest Tasmania1

Louisa Bay, in southwest Tasmania, was archaeologically investigated during two field seasons, eight weeks in 1975 and four weeks in 1976. A total of six sites were sampled. Sites on Maatsuyker Island, to the south, were investigated over two separate two week periods in 1974 and 19 76. This article is intended as a preliminary statement on the Louisa Bay research.

Water power potential of south-western Tasmania

The potential average energy obtainable from the major rivers of South-West Tasmania is about 25% of the total hydro-electric potential of the State. Water power is the only indigenous source of energy of any significance in Tasmania. It is a non polluting and self renewing source o f energy.

Engineering geology of the Gordon Dam, South West Tasmania. 11F, 7T, 11R : Q.J. ENGNG. GEOL., V9, N1, 1976, P1–P24

Engineering geology of the Gordon Dam, South West Tasmania. 11F, 7T, 11R : Q.J. ENGNG. GEOL., V9, N1, 1976, P1–P24

Geological factors in the location of the power station and associated works, Gordon River Power Development, Stage 1, South-West Tasmania : ROBERTS, GT ANDRIC, M 5F, 1T, 6R. 2ND AUS-N. Z. CONF. GEOMECH, BRISBANE, 1975, INST. ENGRS, AUS. NAT. CONF. PUBL. NO. 75/4, P213–217

Geological factors in the location of the power station and associated works, Gordon River Power Development, Stage 1, South-West Tasmania : ROBERTS, GT ANDRIC, M 5F, 1T, 6R. 2ND AUS-N. Z. CONF. GEOMECH, BRISBANE, 1975, INST. ENGRS, AUS. NAT. CONF. PUBL. NO. 75/4, P213–217

Engineering geology of scotts peak dam and adjacent reservoir watertightness : ROBERTS GT COLE BA BARNETT RHW 10F, 4T, 5R. AUST. GEOMECH. J. G5, N1, 1976, P39–47

Scotts Peak and Edgar Dams are located on the southern boundary of the new Lake Pedder, which is a major storage covering 93 square miles (24 x l0{3} ha) in south-west Tasmania. Limestone and cavernous dolomite exist on the storage rim but a limited investigation was sufficient to show that serious leakage from the reservoir was unlikely. At Scotts Peak Dam the poor quality of the plinth foundations led firstly to special treatment to protect the foundation surface and secondly to the inclusion of an impermeable zone of natural gravel within the embankment. Rockfill was the main embankment material, and drilling at five potential quarry sites was carried out before a weak weathered argillite was accepted. Edgar Dam was located to avoid a karst risk. The dam was founded on gravel with a cut-off to phyllite bedrock. The high pemeability of the gravel enabled a well-point system to be used for dewatering during cut-off construction.

Engineering geology of the Gordon Dam, South West Tasmania

Summary The Gordon Dam is a double curvature concrete arch structure 140 m high, forming part of a hydro-electric scheme. The dam is sited on folded and faulted Precambrian quartzite. Driving adits was favoured over diamond drilling in siting the dam and for detailed investigations to prove the stability of the foundations. Considerable excavation on the left abutment was necessary to remove unfavourable rock and a continuous pre-split face of 122 m was produced. The geological conditions found during excavation were better than anticipated thus raising the computed factor of safety.

Investigations into the watertightness of the proposed Gordon-above-Olga hydro-electric storage South-west Tasmania : Roberts, GT, Hydro-Electric Comm. Hobart, Aus Andric, M, Hydor-Electric Comm. Hobart, Aus 6F, 2T, 17R. Q.J. Engng. Geol. V7, N2, 1974, P121–136

Investigations into the watertightness of the proposed Gordon-above-Olga hydro-electric storage South-west Tasmania : Roberts, GT, Hydro-Electric Comm. Hobart, Aus Andric, M, Hydor-Electric Comm. Hobart, Aus 6F, 2T, 17R. Q.J. Engng. Geol. V7, N2, 1974, P121–136

The Late Cambrian to Early Ordovician sequence on the Denison Range, southwest Tasmania

A well-exposed middle Late Cambrian to Early Ordovician clastic sequence, herein referred to as the Denison Subgroup, unconformably overlies Middle Cambrian rocks on the Denison Range and is conformably overlain by Ordovician limestone. Four formations are recognized. The basal Singing Creek Formation (720 m) consists of interbedded siltstone, quartzwacke turbidites, siliceous fine conglomerate, and slump sheets, and contains an abundant Franconian trilobite-brachiopod fauna. It grades upwards into the Great Dome Sandstone (510 m), a shallow marine-deltaic-fluvial sequence of crossbedded quartz sandstone, siltstone and fine conglomerate, with a sparse fauna of probable Late Cambrian age. Above this the Reeds Conglomerate (1560 m) comprises largely non-marine pink siliceous conglomerate and cross-bedded sandstone, probably deposited on alluvial fans. This grades into the marine Squirrel Creek Formation, comprising a lower sandstone member (150 m) with worm burrows and gastropods, a siltstone- limestone member (150 m) with an abundant Early Ordovician shelly fauna, and an upper sandstone member (300 m). The Denison Subgroup is approximately equivalent to the pre-limestone part of the Junee Group in the 'original area of Lewis, and to the Owen Conglomerate of western Tasmania.