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.

Pseudotachylite vein-breccia networks and pseudotachylites intrafoliated with mylonites occur pervasively in the Tomkinson Ranges, western Musgrave Block, central Australia, about 50 km south and constituting part of the hanging wall of the Woodroffe thrust. The pseudotachylites are almost exclusively confined to gabbro, anorthosite and dolerite, and are rarely seen in basic granulites, felsic granulites and granitic gneiss. Pseudotachylite is ubiquitous in steeply tilted, deformed and mylonite-intersected sectors of the Giles Complex (Hinckley Range, Kalka, Michael Hills) but was not detected in the mildly tilted and little deformed western sectors of the Giles Complex (Blackstone Range, Cavenagh Range, Jameson Range), suggesting that fusion events concentrated in deformed relatively deep crustal levels. Two principal modes of occurrence of pseudotachylite are recognised : 1, vein-breccia networks superimposed on older lithological contacts and associated with brittle fracture systems; 2, penetrative pseudotachylite laminae interleaved with mylonite along shear zones. It is inferred that friction fusion events triggered by seismic faulting have affected intermediate crustal levels where mylonite shears separate brittle fracture domains. Contemporaneous development of pseudotachylite in each domain may be suggested by the lack of observed intersecting relationships between the two types of pseudotachylite vein systems. Alternatively, the mylonite-related pseudotachylites may have formed in quasi-plastic deep crustal zones. Comparisons between the chemistry of pseudotachylites and bulk host rock composition suggest a limited degree of selective fusion, increasing the silica levels and lowering the Mgvalues and Cr levels in the melt. Alternatively, these variations may have been brought about by fluid phase activity. Evidence for a high temperature melt origin of the pseudotachylite includes finer-grained margins, resorbed microclasts, micron-scale subhedral crystal texture of the pseudotachylite and distinct chemistry of microphenocrysts compared with host rock mineral composition. Laser-Raman spectroscopy has shown that the material is mostly crystalline but also suggests the occurrence of minor glass components in the pseudotachylite. High-Al and high-K pyroxenes from the pseudotachylite suggest seismic overpressures of the order of 30 kb, or metastable disequilibrium quench crystallisation of the pseudotachylite melt.

The eastern margin of the Australian continent was the site of convergent plate interaction for much of the Palaeozoic Era. The Tamworth Terrane, a forearc complex resulting from this interaction, occurs in the northeastern corner of New South Wales. This forearc basin, now preserved as a complex erosional and tectonic remnant in the Tamworth belt and Hastings block, originally formed a relatively linear belt before terrane dispersal resulting from Permian orogenesis. Tectonic-subsidence curves derived from thirteen well-exposed sections show that subsidence began abruptly, continued for approximately 50 Ma, and then ceased just as abruptly. Total tectonic subsidence was 4- 6 km at either end of the basin, and 2- 3 km in the intervening areas of the southern Tamworth belt. Depositional patterns were controlled largely by sediment supply and subsidence; the preserved sedimentary rocks form a large-scale upward-shallowing succession. In detail, the effects of eustatic sea level change are also apparent, particularly around the basin margins and in the shallower water associations. The continuous interaction among these three major variables produced a basin that changed in morphology both spatially and temporally.

A microearthquake survey around the fault scarp caused by the 1979 Cadoux, Western Australia, earthquake located 36 earthquakes (ML 0-2.4) over 7 weeks from October to December 1983. The earthquakes show a NNE-SSW trend on the westward side of the fault complex, consistent with a westward dipping fault plane. The earthquakes are evenly distributed along the length of the fault. The more accurately located earthquakes are 0-6 km deep.

An earthquake occurred without warning at 10:27 am on 28 December 1989 (local time) causing loss of life in the city of Newcastle, New South Wales, Australia, the first earthquake to cause fatalities in Australia since European settlement. The magnitude is estimated to have been 5.6 on the Richter scale. Earthquakes of this size occur on average about once every eighteen months in Australia. A single aftershock was recorded on a network of ten seismographs installed on 29 December in and around Newcastle; it had a magnitude of 2.1. The focal depth of the mainshock was 11.5±0.5 km and of the aftershock 13.5±0.8 km, which is beneath the Permian sediments of the Sydney Basin. The epicentres of both earthquakes are coincident within the error bounds and are some 15 km from the centre of damage in the City. The damage in Newcastle was made worse by an underlying thin layer of alluvium which magnified the ground motion substantially. A fault-plane solution indicates that the earthquake had a thrust mechanism with nodal planes striking in a NW-SE direction, parallel to the mapped surface faults in the region. Limited strong motion data were recorded, but not close to the epicentre.

Examination of new Late Cambrian samples from the upper part of the Chatsworth Limestone and lower part of the Ninmaroo Formation from Black Mountain, Georgina Basin, western Queensland (representing the pre-Payntonian, Payntonian and Datsonian Stages) has delineated five conodont assemblages in an interval that had previously not been subdivided using conodonts. Examination of the conodont fauna unambiguously confirms that the entire Payntonian Stage is of Cambrian age, as earlier indicated by the trilobite fauna, and provides three conodont assemblages that may subsequently form the basis for a conodont zonation. The Datsonian Stage, defined by the FAD of the Cordylodus proavus conodont assemblage and previously considered to equate with the Early Tremadoc (= Early Ordovician) of Europe, is now considered to represent the terminal Cambrian stage in northern Australia. The base of the Ordovician, equated with the base of Tremadoc correlatives, lies close to the Datsonian/Warendian boundary on the Black Mountain section. Two new conodont genera, Eodentatus and Hispidodontus, are established, along with four new species, E. bicuspatus, H. resimus, H. appressus and H. discretus. All are found in the Payntonian Stage in the upper part of the Chatsworth Limestone or the lower part of the Ninmaroo Formation.

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Fifteen of 27 potential planktic foraminiferal biostratigraphic events from the latest Pliocene-Holocene have been examined; most of the early Pleistocene was not able to be studied because of a hiatus in the one core which penetrated through the Pleistocene into the top of the Pliocene. Four of these events have been recognised for the first time, and some have been used to establish a formal zonal and subzonal scheme for the region. Two new subzones are proposed, the Globigerinoides quadrilobatus fistulosus Subzone (for the basal part of Zone N.22) and the Bolliella praeadamsi Subzone (for the top part of Zone N.22). These changes have made necessary the redefinition of both the Globorotalia (Truncorotalia) crassaformis viola and the Globorotalia (Truncorotalia) crassaformis hessi Subzones. There is little evidence that changes in palaeoceanographic conditions are related to the faunal changes observed in the cores, although there are strong indications of reworking at some levels within some of the cores (such as late Miocene Zone N.17 in one core), which may have been related to sea-level fluctuations. The assemblages from the cores show a marked stability, with the faunas being dominated by spinose, oligotrophic taxa. Temperate water forms are either very rare or absent, whereas tropical and subtropical species are dominant. A single new species, Bolliella praeadamsi has been described because of its biostratigraphic utility. This species is an evolutionary intermediate between Bo. calida praecalida and Bo. adamsi.

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Conodonts have been recovered in samples from two stratigraphic units in Irian Jaya: the Modio Dolomite in the Charles Louis Range, and probably the Aimau Formation in the central Birds Head. The Modio Dolomite fauna includes Panderodus cf. P. simplex (Branson and Mehl, 1933), and probably has a Silurian age. Two float samples considered to have been derived from the Aimau Formation yielded a fauna comprising Neognalhodus cf. N. bassleri (Harris and Hollingsworth , 1933) and Hindeodus minutus (Ellison, 1941), which indicate a Late Carboniferous age.