Micropalaeontological and biostratigraphic studies have been used to assist understanding of the stratigraphic and structural context of groundwater flow systems in the vicinity of the Woolpunda Groundwater Interception Scheme (WGIS) - a major area of saline groundwater discharge to the River Murray in the western Murray Basin. Structure was defined by tracing several stratigraphic markers in the Late Oligocene to Middle Miocene succession, including the Lepidocyclina foraminiferal zone and three clay or marl units of low permeability. A cross-section through the upper part of the Cainozoic sequence illustrates east- west arching gentle Middle to Late Miocene folding, and intermittent mild Cainozoic uplift. Arching and doming across the WGIS area is confirmed by a structure contour plot on top Renmark Group, and by limited drilling in the deeper Eocene and Cretaceous sediments. The arched structure apparently relates to draping of the Tertiary succession over a high of pre-Tertiary rocks related to the Hamley Fault. This high acts as a permeability barrier to the Renmark Group confined aquifer which thins significantly over it, promoting upward leakage into the water table aquifer, with resultant high saline discharge to the River Murray.

Saline groundwater intrusions into lowland reaches of the Wimmera River, western Victoria, accumulated under low-flow conditions and formed stable saline pools. An extensive area of river downstream was affected, and almost all water in the channel during flow stoppages appeared to be of groundwater origin. Water in these saline pools had conductivity up to seawater level ( > 50000 EC units) , stable temperature of 14-20°C, low dissolved oxygen (< 10% saturation), and low pH (6.1 - 6.4), in contrast with surface water (conductivity < 4000 EC units, oxygen level >60% saturation, and temperature 8- 12°C in winter and over 20°C in summer). Halocline, oxycline and thermocline depths generally coincided, especially in winter. Salinity-related density stratification was very stable even in winter. The stratification pattern remained stable under low to moderate discharge (mean daily discharge < 1000 ML / day) , although major flow events (> 3000 ML / day) mixed or displaced most of the saline bottom layer. Saline pools which re-established within two months of flow decline had similar depth, temperature and conductivity to those found six months before. Under the prevailing intermittent flow regime, saline pools would be expected during the 7-month low-flow period (October to May) in most years. Stable stratification and associated severe hypoxia rendered much of the water in the pools uninhabitable by fish and other aerobic organisms; hypoxia rendered bed substrates and organic debris inaccessible for cover, feeding or resting, and probably reduced secondary production. The habitable area in many pools was confined to upper layers and shallow pool margins. Severe deoxygenation and rapid short term changes in salinity and temperature occurred with a first flush, and displacement of partially mixed saline water produced secondary stratifications in deep pools downstream. Vertical conductivity gradients of < 1000 EC units were associated with persistent deoxygenation at many sites as a result of this process. The total area affected by saline groundwater intrusions extended downstream far beyond the immediate area of the intrusion. The Wimmera River provides a model for other rivers in the Murray-Darling Basin where saline groundwater from rising water tables drains into them. The low-land sections of many rivers and streams proposed as sites for the disposal of saline water might have flow regimes and channel morphology conducive to the formation of stable saline pools. Further studies are required to develop management and control measures to prevent large-scale environmental degradation of riverine habitats in the Murray-Darling Basin through rising water tables, increased groundwater drainage or deliberate disposal of saline water into rivers and streams.

The Ivanhoe Block is a faulted and uplifted concealed basement ridge complex underlying the mallee sand dunes adjacent to the New South Wales part of the Western Riverine Plain in the central Murray Basin. The western ridge of the Ivanhoe Block forms the regional divide between the Darling and Lachlan-Murrumbidgee groundwater systems. The parallel basement ridges of the Ivanhoe Block deflect flow south in the deeper aquifers, and thinner beds on top of the ridges result in convergence of flow in the shallower aquifers. The Geera Clay aquitard is enveloped by the Renmark Group on the Ivanhoe Block this produces an additional barrier to lateral groundwater throughflow. Groundwater salinity is strata-bound in the aquifers of the Ivanhoe Block and Western Riverine Plain, and this enhances the value of electric logs in accomplishing a 3-fold subdivision of the Renmark Group- a basal fluvial succession, overlain by a paralic grading to marginal marine sequence which in turn is overlain by a prograding shoreline succession. The Western Riverine Plain is the regional groundwater discharge zone for the eastern Murray Basin in New South Wales, and it has been created by the impeding action of the bounding Ivanhoe Block . On the basis of rates of change of chloride concentration along regional flow lines in the Tertiary aquifers, the Western Riverine Plain is partitioned into the Balranaid- Hatfield discharge zone in its western half and the Moulamein - Mossgiel buffer zone in its eastern half; the former defines the zone of salt production and accumulation in the shallower Tertiary aquifers and the latter defines the maximum historical extent of up-basin propagation of refluxed salts. In recent years the Ivanhoe Block and western Riverine Plain of New South Wales have been the focus of growing community concern about clearing in the mallee lands and the susceptibility of these areas to land salinisation. This paper addresses the second issue. The Balranald Hatfield discharge zone and the lower Willandra Lakes are most at risk from land salinisation if water tables continue to rise. The Moulamein Mossgiel buffer zone is in the second-highest risk category, and the eastern Riverine Plain has a low risk of sa linisation in its non-irrigated lands.

In the Murray Basin of southeastern Australia, the accelerated emergence of groundwater-related salinity problems in recent decades has led to the realisation that future viability of many of its agricultural communities depends on management of its water resources. Part of the management strategy involves improving our understanding of the relationships between aquifer geometry, permeability barriers, groundwater flow and surface discharge of saline groundwater. This paper summarises the stratigraphy, distribution and geometry of units deposited in the mid-Tertiary which now form major subsurface permeability barriers. Subsurface facies analysis of borelogs and palaeogeographic reconstructions indicate that the Murray Basin has been invaded by the sea on at least three separate occasions during the Cainozoic. The most prolonged of these marine incursions commenced about 32 Ma ago, when the western Murray Basin was invaded by a shallow epicontinental sea, which remained within the basin for at least 20 Ma. In the mid-Oligocene, thin (10- 30 m) calcareous clay (Ettrick Formation) of the lower confining layer was deposited over much of the southwest of the basin . This clay now separates the underlying Renmark Group aquifer system from the overlying Murray Group aquifer system, but does not impede the flow of groundwater from the margins of the basin towards its main depocentre in the central west of the basin. As relative sea level continued to rise in the Late Oligocene, the thin sediments of the lower confining layer were overlain by thicker (generally > 100 m) Upper Oligocene-Middle Miocene limestone of the Murray Group aquifer system. To the north and east, the limestone grades laterally into thick (locally > 100 m) shallow-marine to lagoonal calcareous clay (Winnambool Formation) and shallow to marginal-marine fine terrigenous clastics (Geera Clay). The Winnambool Formation and Geera Clay combine to form the mid- Tertiary low-permeability barrie, in an arcuate zone in west central areas of the basin, which causes major disruption to the flow of groundwater towards the main depocentre in the central west. The Geera Clay forms an important subsurface barrier, resulting in the partial diversion of flow into the overlying Pliocene Sands aquifer system, and locally to surface groundwater discharge complexes. The porosity and permeability of the Geera Clay were examined in a fully cored section in Piangil West-2 borehole. It has previously been assumed that the Geera Clay consisted predominantly of clay minerals, but the section in Piangil West-2 contained only 6% of black plastic clay, and was characterised by dark and carbonaceous semi-consolidated silt and muddy silt (65%), unconsolidated and partly indurated sand (15%), and mud (14%). Visual estimations of mesoscopic and macroscopic interparticle porosity suggest effective porosity is now 0- 7%, whereas the original mesoscopic porosity is thought to have ranged from about 5- 10% in the silt to 30% in the sand. Burrow interparticle porosity predominated. The occlusion of effective interparticle porosity was caused by precipitation of clay, glauconite, pyrite, calcite and dolomite at an early stage. Carbonate and minor pyrite precipitation continued as both replacement and porefill for the duration of shallow compaction through to late diagenesis, when pyrite, resinous organic matter, and traces of arsenopyrite occluded most of the remaining effective porosity.

It has previously been suggested that an ancient Murray River once extended across the present line of the Mt Lofty Ranges, and emptied into Spencer Gulf. Evidence available from a comprehensive study of the Murray Basin shows that this is unlikely, at least during the Cainozoic. Sedimentation patterns reconstructed from several thousand borelogs suggest that a precursor to the modern river existed at least from the Eocene, but that this river emptied into the Murravian Gulf of the Southern Ocean at sites within the Murray Basin during periods of marine flooding, and at sites close to that of the modern mouth at times of lowered sea level. Precursor streams to most major tributaries of the Murray River have also existed since at least the Eocene, and drainage patterns reflect the combined influences of subtle tectonic movement of underlying shallow basement and eustatic overprinting.

Recent detailed studies of key transects throughout the Clarence-Moreton Basin have shown that a revision of nomenclature is required for units in the Late Triassic to Early Jurassic Bundamba Group. Revision of the stratigraphic nomenclature and elimination of the existing confusion in names of units in the basin was considered an essential first step in understanding basin evolution and assessing petroleum potential. We redefine the Marburg Formation as the Marburg Subgroup of the Bundamba Group and divide the Subgroup into two distinct lithostratigraphic units, the uniform sandstone of the Gatton Sandstone and the mixed sandstone and mudrocks of the younger Koukandowie Formation. The formations are upgraded existing members. The Gatton Sandstone contains locally developed members along the western basin margin. The Koreelah Conglomerate Member forms the base of the Gatton Sandstone where it overlaps basement rocks, and the Calamia Member of mixed shale, mudrocks and sandstone is a basal unit in the Gatton Sandstone in more basinward sections. The Heifer Creek Sandstone Member is a prominent quartzose sandstone unit in the Koukandowie Formation along the western margin and central parts of the basin. The older mixed mudrocks and sandstone of the Ma Ma Creek Member of the Koukandowie Formation are mainly known from the northwest. This new nomenclature preserves the integrity of existing stratigraphic names and is applicable basin- wide. One new stratigraphic name, the Koreelah Conglomerate Member, is introduced.

Chemical and mineralogical data are presented for four ferromanganese samples (two nodules and two crusts) from two stations of the West German vessel Sonne. Three samples came from a dredge on the flanks of the Dampier Ridge in water 2400- 2700 m deep. One came from a core on the Lord Howe Rise in water 1549 m deep. Thick ferromanganese deposits overlie a variety of substrates including granite, gabbro and feldspathic sandstone. The ferromanganese deposits, which are up to 20 cm thick, range from round mononucleate nodules with small volcanic nuclei, to polynucleate nodules, to nodules bound together as crusts, and to laminated crusts. Both nodules and crusts are hydrogenetic in origin and have low contents of Ni, Cu and Co, and low Mn:Fe ratios of 0.48-0.91. A comparison of these results with those from three deeper water stations of Galathea and Tangaroa indicates that Mn:Fe ratios, Ni% and Cu% increase markedly in deeper water, where Mn:Fe ratios exceed 2.5, and Ni+Cu+Co values exceed 1.25%. Any future search for nodules of economic significance should be concentrated in the even deeper water areas (>5000 m) east and southeast of Gascoyne Seamount.

On 22 December 1987 a shallow magnitude 4.9 earthquake occurred in western Victoria where there is no record of previous seismic activity. It was felt over a remarkably wide area of Victoria and South Australia and caused minor damage in the epicentral area. There were no foreshocks and only ten aftershocks were recorded on the nearest seismograph, near Willalooka in South Australia. All ten occurred within five days of the mainshock. The earthquake occurred in a seismic zone that extends over a 500 km wide belt along the entire eastern coast of Australia linking the Southeast Seismic Zone of South Australia with the Eastern Highlands Zone through Queensland, New South Wales, Victoria and Tasmania. Its focal mechanism, a thrust with a principal stress directed east-west, is typical of earthquakes in the Lachlan Fold Belt.

The deeply incised northern margin of the Exmouth Plateau has been dredged extensively along seismic reflection profiles, in water 2000- 5600 m deep, by R. V. Sonne (Cruise SO-8) and R. V. Rig Seismic (BMR Cruise 56). Geological samples obtained have greatly increased our understanding of the Late Triassic- Recent history of the margin. Detailed petrography and microfacies analysis have enabled us to define seven major lithofacies associations. Three Late Triassic to Middle Jurassic associations were laid down roughly coevally on this southeastern margin of Tethys: (1) a Late Triassic- early Liassic volcanic and volcaniclastic association of early rift volcanics, (2) a Late Triassic- Middle Jurassic shallow water carbonate association, and (3) a ?Late Triassic- Middle Jurassic coal measure association. The coal measures were uplifted and weathered to form a ?Jurassic ferruginous sediment and ironstone association. We distinguish 14 Late Triassic- Callovian microfacies types of shallow water carbonates, which can be correlated with the facies of coeval platform carbonates in the Alps and Mediterranean area of the Tethys ocean. During Late Triassic times intertidal to shallow-subtidal carbonates were deposited in the Swan Canyon area close to the palaeo-coastline in the east, and deeper subtidal and shelf lithologies in the Wombat Plateau area in the west. During the latest Triassic and earliest Jurassic, the carbonate platform subsided and was structured into shoals with red biomicrites, and basinal areas with hemipelagic autochthonous micrites and redeposited calcarenitic turbidites. Locally, uplifted blocks, such as the Wombat Plateau horst, were subaerially eroded during Jurassic or earliest Cretaceous times. Carbonate platform deposition continued in places until Middle Jurassic time. Following breakup to form the Argo Abyssal Plain in the earliest Cretaceous, the margin started to subside and a Lower Cretaceous marginal-marine claystone association was deposited, followed by a hemipelagic late Lower Cretaceous radiolarian claystone. As subsidence continued, from Turonian times onwards, there was increasingly pelagic deposition of a Late Cretaceous to Cainozoic association of hemipelagic to eupelagic variably silicified marls and chalks. Complex diagenetic transformations involve silica, silicates, carbonates, and phosphates.

Samples dredged during BMR Survey 66 by KV, Rig Seismic in the central Great Australian Bight Basin are examined and their calcareous nannofossils are recorded. The Maastrichtian, Eocene and Oligocene assemblages are compared with those known from the onshore southern Australian sequence, allowing a better understanding of the history of the southern margin of Australia. The Maastrichtian assemblages, the first found in southern Australia, probably represent a marine ingression encompassing three discernible phases. The Eocene record includes assemblages older than any from onshore and is also older than the base of the Eocene section on the Naturaliste Plateau. An offset parallelism with the onshore record is evident: in the offshore (Great Australian Bight) sequence, early Eocene ingressions preceded a middle Eocene transgression, while in the onshore Otway Basin (to the east) middle Eocene ingressions preceded a late Eocene transgression. In both sequences there are earlier Tertiary ingressions which were suited for calcareous foraminiferids but apparently not coccolith-forming nannoplankton. The previously reported excursion of the low-latitude Sphenolithus ciperoensis into southern Australia in the Oligocene is confirmed, being a result of a short warm episode, Surface waters along the southern margin of Australia were warmer in the west than in the east during much of the Eocene and Oligocene, This is attributed to a warm intermittent proto-Leeuwin Current, beginning in the middle Eocene, which brought warm surface waters from northwestern Australia into southern Australia. Dilution of the currents effects on the surface waters of southern Australia would be expected in an easterly direction. Nannofossil evidence, supported by palynological and lithological data, suggests that the seafloor in the Great Australian Bight Basin has subsided considerably since the Late Cretaceous. The onset of the increase in rate of subsidence in the middle Eocene (as reflected by the nannofossil assemblages) marked the end of a stage of very slow subsidence initiated at about 90 Ma ago. The assemblages provide strong evidence for a marked fall in sea level during the latest late Eocene, at a rate considerably higher than that of subsidence, resulting in shoaling well into the Oligocene.