Large geochronological and geochemical data sets for the Paleo- to Mesoarchean Pilbara and Meso- to Neoarchean Yilgarn cratons, Western Australia, show that both cratons exhibit similar evolutionary trends in felsic magmatism, providing important constraints on Archean tectonics. The most obvious trend is a transition from sodic magmatismthe ubiquitous tonalite-trondhjemite-granodiorite (TTG) series with their high pressure (high-Al) signatureto potassic magmatism. In the Pilbara craton this transition is marked by two periods of potassic magmatism separated by 50 Myr. In the Yilgarn, the transition is mostly diachronous with potassic magmatism broadly younging to the west, except for one terrane where potassic magmatism begins ~40 Ma earlier. The change from sodic to potassic magmatism is, in part, a continuation of trends observable within the sodic granites themselves, which become more LILE-enriched with decreasing age. It is also evident in both cratons that magmatism derived from basaltic precursors is not confined to high-pressure formation of High-Al TTGs but includes lower pressure variants. The latter include low-Al TTGs (significant in the Pilbara Craton), and a group with high-HFSE and low- to moderate LILE-contents typical of A-type magmas. In the Yilgarn Craton such rocks form a locally common, often bimodal, association, representing formation at high-temperature and low-pressure. They are not often recognised as belonging to the sodic magmatic group but clearly reflect a magmatic pathway that starts with a largely mafic protolith, albeit at lower pressures and, unlike the low-Al TTGs, higher temperatures. Another shared trend is the appearance of a diverse group of rocks not unlike those seen in modern-day convergent tectonic settings. These comprise high-Mg diorites (or sanukitoids) (and related rocks), boninite-like rocks, `calc-alkaline basalts and andesites, calc-alkaline lamprophyres, but also syenites and monzonites. These rocks appear well after the first appearance of high- (and low-) Al TTGs and are most abundant just prior to major onset of potassic magmatism. In both cratons they are largely confined to younger linear geological terranes or marginal to/within the larger generally older terranes, and this, along with their enriched geochemistry permits the interpretation that they tap enriched mantle along crustal scale structures. Such rocks form a significant local component but overall are not abundant. The trends documented above are evident in many Archean terranes. The simplest way to explain the variation in the TTGs (high- and low-pressure variants) and the trends from sodic to potassic magmatism is via progressive reworking (maturation) of existing continental crust (for crustal-derived magmatism) and increasing involvement of felsic crust (for non-crustal magmatism). The chemical and isotopic evidence suggests a role for both mechanisms. It is, however, clear that crustal reworking played an early and persistent role in the compositional evolution of both the Pilbara and Yilgarn cratons (and probably Archean cratons in general), suggesting that models advocating a switch from slab-derived TTGs to crustal-derived potassic magmas are too simplistic. The appearance of magmas with an arc-like signature suggests that proto-subduction-like tectonic processes operated, at least intermittently, but not necessarily that they dominated Archean crustal evolution and crust formation.

This paper presents results of repeat surveys of levelling and gravity, analysed to determine areas of vertical ground movement in the Southwest Seismic Zone, 75-200 km east of Perth. Levelling surveys over parts of the earthquake zone have been made during four periods, starting in 1958. Differences between repeat levelling surveys separated by 10 or more years show areas of vertical ground movement, the areas being 20-50 km across with relative height changes of 50-100 mm amplitude. Some of the vertical ground motion is movement at the time of earthquakes, some is later rebound in the same earthquake areas, and other movement does not appear to be associated with large or small earthquakes and could be due to either elastic strain, or non-seismic faulting. Precise gravity observations at 10 km spacing were made in 1980-81 and repeated in 1983. The differences between the surveys do not show any significant gravity changes. Future studies should be set up to monitor stress, strain and earthquakes in a group of small, diverse test areas, using the global positioning system.

The nannostratigraphy of material dredged from the Fremantle Canyon, west of Perth (Western Australia), indicates that the Maastrichtian-Miocene section in the South Perth Basin is more complete than contemporaneous sections in the Perth Abyssal Plain and on the Naturaliste Plateau. The data point to a possible continuous sequence through most of the Paleocene and the entire Eocene in the Fremantle Canyon. In addition to the five rock units previously known to form the Maastrichtian-Miocene succession of the Perth Basin, two (or possibly three) new units have been discovered. The new units, yet to be named, are of Early Eocene and mid Oligocene age; in addition a previously unreported Lower Paleocene sequence could be the lower extension of the Kings Park Formation offshore. The unnamed new Lower Eocene unit fills the stratigraphic gap between the (mainly) Upper Paleocene Kings Park Formation and the Middle Eocene Porpoise Bay Formation. The unnamed new mid (upper Lower) Oligocene unit fits between the Upper Eocene Challenger Formation and the Lower-Middle Miocene Stark Bay Formation, still leaving a large stratigraphic gap between these two formations. The lithological evidence, supported by nannofossil data, indicates that the Porpoise Bay and Challenger Formations merge into a single unit along the canyon walls. This unit is similar to the Lower Eocene and Paleocene carbonates there. A widespread Late Maastrichtian transgression over the Carnarvon and Perth Basins, reaching the Great Australian Bight Basin as an ingression, is seen in the Fremantle Canyon as occurrences of nannofossil association characteristic of the Upper Maastrichtian Breton Marl onshore. Several lines of evidence are discussed to suggest that the onshore Kings Park Formation represents a rapid sea level rise and culmination of the Paleocene transgression over the Perth Basin. Indications of a previously reported significant Middle Eocene reworking episode are recorded at the right level in the Fremantle Canyon succession. Middle Eocene microplanktic components found in the newly reported mid Oligocene of the canyon are thought to have been derived from the Naturaliste Plateau during a major Oligocene erosional event, whose effects have been recorded previously in several DSDP sites in the Southwest Pacific region.

Three new beyrichiacean genera are described from the type section of the Buttons beds, latest Devonian, along the eastern bank of the Ord River: Notoscapha gen. nov. (type species N. oepiki sp.nov.) from the lower part of the section below 120 m, Parabouchekius gen. nov. (type species P. martinssoni sp. nov.) and Katatona gen. nov. (type species K. romei sp. nov.) both from the middle part of the section 120-200 m. They lack traces of a dolonoid closing mechanism, and are interpreted, within Martinssons scheme of beyrichiacean phylogeny, as advanced treposellids. The posterocentral site of a possible rudimentary crumina in a presumed female specimen of Katatona romei may indicate a syllobial origin for the crumina in those genera having a similar type of dimorphism. This type of cruminal dimorphism is present in species from the Late Devonian of the European USSR that have been assigned to Aparchites and to the related genera Bouchekius, Copelandites, and Reversoscapha. The distribution of species of Katatona, Bouchekius, and Parabouchekius is discussed to evaluate their potential for long-distance correlation in the latest Devonian (ie., late Famennian and Strunian). At present, Katatona indicates a Strunian (Fa2d, Tnla) age, and its presence in the Buttons beds supports the age assignment recently proposed on miospore evidence.