A recent field-intensive program in Shark Bay, Western Australia provides new multi-scale perspectives on the world’s most extensive modern stromatolite system. Mapping revealed a unique geographic distribution of morphologically distinct stromatolite structures, many of them previously undocumented. These distinctive structures combined with characteristic shelf physiography define eight ‘Stromatolite Provinces’. Morphological and molecular studies of microbial mat composition resulted in a revised growth model where coccoid cyanobacteria predominate in mat communities forming lithified discrete stromatolite buildups. This contradicts traditional views that stromatolites with the best lamination in Hamelin Pool are formed by filamentous cyanobacterial mats. Finally, analysis of internal fabrics of stromatolites revealed pervasive precipitation of microcrystalline carbonate (i.e. micrite) in microbial mats forming framework and cement that may be analogous to the micritic microstructures typical of Precambrian stromatolites. These discoveries represent fundamental advances in our knowledge of the Shark Bay microbial system, laying a foundation for detailed studies of stromatolite morphogenesis that will advance our understanding of benthic ecosystems on the early Earth.

A remarkable example of an exhumed Middle to Late Devonian barrier-reef belt extends for about 350 km along the northern margin of the Canning basin in Western Australia. The reefs form a series of rugged limestone ranges cut by deep river gorges which provide spectacular sections through the reefs and associated facies. The gross morphology of the ranges and intervening valleys closely resembles that of the Devonian seafloor, so that from the air the reefs are displayed much as they were in Devonian time.The Canning basin reef complexes offer exceptional opportunities for carbonate research because of the excellence of exposures and the wide variety of facies represented; moreover the rocks are little deformed, are not dolomitized extensively and are unmetamorphosed. Some facies have undergone significant compaction through stylolitization; however, most structures and textures in the limestones can be shown to have had depositional or early diagenetic origins.The reef complexes developed as reef-fringed limestone platforms flanked by marginal-slope and basin deposits. They were built by stromatoporoids, algae, and corals in the Givetian and Frasnian and by algae in the Famennian. The platform and basin facies were laid down nearly horizontally, whereas the marginal-slope facies accumulated with steep depositional dips away from the platform. Marginal slopes commonly were as high as 35° in loose talus and were up to vertical where algal binding occurred in association with early lithification. Geopetal fabrics quantify depositional and tectonic/compactional components of observed dips for paleobathymetric studies of the complexes and their fossil biotas.Four main types of platform margin are present: retreating, back-stepping, upright and advancing. The advancing type is characteristic of the Famennian platforms, whereas the other three are typical of the Frasnian. Pinnacle reefs developed during periods of rapid subsidence, especially during the middle Frasnian, are associated with back-stepping and retreating platform margins.Very early submarine cementation was widespread around the platform margins and on parts of the marginal slopes, but it was not generally extensive in the platform interiors. Early fracturing of reef limestones along the platform margins, probably associated with earthquakes, resulted in the development of neptunian dikes and the collapse of some sections of the reef as submarine rockfalls. These often initiated massive debris flows, many of which carved channels in and, somewhat deformed, the underlying marginal-slope deposits.

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