In the present study, the relative distributions and stable carbon and hydrogen isotopic compositions of the biomarkers from high grade oil shales (Permian and Carboniferous torbanites) rich in B. braunii fossils (i.e. torbanites) deposited under a range of climatic conditions are stringently scrutinised for any evidence of molecular features which may be characteristic of palaeogeographical location of deposition. Eleven torbanites from Scotland, South Africa and Australia covering the Late Carboniferous to Late Permian have been analysed.

S-type granites of Proterozoic age are rare in Australia, representing only 2.9% of mapped outcrop area.

The extended abstract describes geophysical map units and large geophysical domains determined for the Yilgarn Craton.

The new species Microdinium avocetianum from the Tithonian (Upper Jurassic) of Australia is described. It is a small partiform gonyaulacalean cyst with a distinctive paratabulation style, dark autophragm and low, irregularly denticulate crests. The species may be relatively prominent in the late Tithonian (Pseudoceratium iehiense Range Zone) of the Timor Sea, offshore north-western Australia and the Carnarvon Basin, offshore Western Australia.

Available surface heat flow measurements from Australian Proterozoic terranes (83 1 18 mWm-2) are significantly higher than the global Proterozoic average of ~ 50 mWm-2. Seismic evidence for the presence of relatively cool mantle together with the lack of evidence for neotectonic processes normally associated with thermal transients suggests that anomalous heat flow must reflect crustal radiogenic sources (U, Th and K). This is supported by a compilation of > 6000 analyses from ~ 460 individual granites, granitic gneisses and felsic volcanics which shows that the present day average heat production of these rock types is 4.6 ?Wm-3 when normalized by area of outcrop (over more than 100 000 km2); roughly twice that of "average" granite. At the time of this felsic magmatism (ca. 1850-1500 Ma) heat production rates were some 25%-30% greater than the present day such that the total complement of U, Th and K in many parts of the Australian Proterozoic crust may have contributed as much as 60-85 mWm-2 to the surface heat flow, or 2 to 3 times the present day continental average. This extraordinary enrichment has played a key role in the tectono-thermal evolution of the Australian Proterozoic crust.

Integrating the geology and geophysics of the Pilbara granite-greenstone terrane (GGT) contributes greatly to the understanding of its tectonic and geological evolution. The Pilbara GGT is an ovoid entity some 600 km by 550 km that was extensively reworked along its margins. The Pilbara GGT is characterised by an ovoid geometry of granitoids and encircling greenstones (dome and basin) that extends across the entire Pilbara GGT. The Pilbara GGT is a unique GGT in that it is very deep (~14 km preserved today), and it appears to continue this ovoid geometry to the base of the mid crust. Mapping deep banded iron-formation in the magnetic data provide an understanding of the timing constraints on the development of the dome and basin geometry (mostly after 3.2 Ga), and also shows that a number of the so-called domain boundaries are not significant faults. The gravity structure of large domal greenstone belts does not support the idea of significant volumes of underlying granitoid. These data also illustrate the relatively thin nature of the < 3.0 Ga successor basins (< 5 km), as well as constraints on their 4D geometry and under cover extension.

The ENE-trending Mallina Basin developed in the central part of the Pilbara Craton, NW Australia, between c. 3010 and 2940 Ma, over the boundary between two distinct terrains characterised by greenstones aged c. 3120 and older. The basin preserves an association of igneous rocks characterised by an unusual combination of high-Mg and high LILE concentrations, that provides valuable insight into the geological evolution of the region. The oldest dated components of the Mallina Basin are c. 3010 Ma volcaniclastic rocks found only in the far northwest. Geochronology and field relationships indicate that the main basin deposition, of clastic rocks, occurred from 2970 to 2955 Ma. Towards the end of this depositional phase, siliceous high-Mg basalts (SHMB) formed the upper part of the stratigraphy in the northwestern part of the basin (Whim Creek Belt), and their subvolcanic equivalents intruded the southern part of the basin. Sedimentation was terminated by ESE?WNW compression at c. 2955-2950 Ma. Rocks with boninitic compositions and spatially associated low-Ti tholeiitic gabbro formed sub-volcanic sills in coarse siliciclastic rocks in the southern part of the basin, probably during the waning stages of compression. Immediately after compression, an extensive alkaline granite complex was emplaced into the central and northern part of the basin, coeval with intrusion of a 2955-2945 Ma high-Mg diorite (or sanukitoid) suite. Renewed extension also resulted in renewed basin sedimentation between 2945 and 2935 Ma. Voluminous high-K monzogranite swamped the region between c. 2935 and 2930 Ma, particularly adjacent to, and south of the basin, and was early- to syn-tectonic with respect to SE-NW compression. Monzogranite magmatism becomes systematically younger and less voluminous away from the Mallina Basin.

The early Campanian species Nelsoniella aceras and Xenikoon australis incorporated into the late Campanian - early Maastrichtian assemblage, as observed in GC09. Nelsoniella aceras can be associated with either the O. porifera or X. australis reworking events.

A two-dimensional crustal velocity model has been derived from 1997 wide-angle seismic profiling across the Lachlan Transverse Zone (LTZ) in the eastern Lachlan Orogen. The LTZ is considered to be a significant early tectonic feature controlling structural evolution in eastern Australia. The 364 km north-south profile passed from Ordovician volcanic and volcaniclastic rocks (Molong Volcanic Belt of the Macquarie Arc) in the north across the LTZ into Ordovician turbidites and Early Devonian intrusive granitoids in the south. The velocity model highlights significant lateral variations in sub-surface crustal architecture within the upper and middle crust. In particular, there is a higher P-wave velocity (6.24-6.32 km/s) unit identified in the upper crust under the arc at 5 to15 km depth that is not seen south of the LTZ. Near-surface P-wave velocities within the LTZ are markedly less than those along other parts of the profile and these are attributed to mid-Miocene volcanic centres. In the middle and lower crust there are also poorly defined velocity features that we also interpret to be related to the LTZ. The interpreted Moho depth increases from 37 km in the north to 47 km in the south above an underlying upper mantle with a P-wave velocity of 8.19 km/s. The seismic data indicate significant differences in crustal architecture between the northern and southern parts of the profile within the upper and middle crust, with associated strong indications that the LTZ may also have through-going crustal features to Moho depths.

Crustal reflectivity and bulk seismic velocity variation in the crust do not always closely correlate. Even the most prominent reflection horizons do not always follow iso-velocity contours. These are the major conclusions of co-interpretation of refraction/wide-angle reflection data and conventional reflection profiles on the North West Australian Margin (NWAM).