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The Strelley Pool Formation (SPF) is widely distributed in the East Pilbara Terrane (EPT) of the Pilbara Craton, Western Australia, and represents a Paleoarchean shallow-water to subaerial environment. It was deposited ~3.4 billion years ago and displays well-documented carbonate stromatolites. Diverse putative microfossils (SPF microfossils) were recently reported from several localities in the East Strelley, Panorama, Warralong, and Goldsworthy greenstone belts. Thus, the SPF provides unparalleled opportunities to gain insights into a shallow-water to subaerial ecosystem on the early Earth. Our new micro- to nanoscale ultrastructural and microchemical studies of the SPF microfossils show that large (20-70 μm) lenticular organic-walled flanged microfossils retain their structural integrity, morphology, and chain-like arrangements after acid (HF-HCl) extraction (palynology). Scanning and transmitted electron microscopy of extracted microfossils revealed that the central lenticular body is either alveolar or hollow, and the wall is continuous with the surrounding smooth to reticulated discoidal flange. These features demonstrate the evolution of large micro-organisms able to form an acid-resistant recalcitrant envelope or cell wall with complex morphology and to form colonial chains in the Paleoarchean era. This study provides evidence of the evolution of very early and remarkable biological innovations, well before the presumed late emergence of complex cells.

The 3.4-Ga Strelley Pool Formation (SPF) at the informally named 'Waterfall Locality' in the Goldsworthy greenstone belt of the Pilbara Craton, Western Australia, provides deeper insights into ancient, shallow subaqueous to possibly subaerial ecosystems. Outcrops at this locality contain a thin (<3 m) unit of carbonaceous and non-carbonaceous cherts and silicified sandstones that were deposited in a shallow-water coastal environment, with hydrothermal activities, consistent with the previous studies. Carbonaceous, sulfide-rich massive black cherts with coniform structures up to 3 cm high are characterized by diverse rare earth elements (REE) signatures including enrichment of light [light rare earth elements (LREE)] or middle rare earth elements and by enrichment of heavy metals represented by Zn. The massive black cherts were likely deposited by mixing of hydrothermal and non-hydrothermal fluids. Coniform structures in the cherts are characterized by diffuse laminae composed of sulfide particles, suggesting that unlike stromatolites, they were formed dominantly through physico-chemical processes related to hydrothermal activity. The cherts yield microfossils identical to previously described carbonaceous films, small and large spheres, and lenticular microfossils. In addition, new morphological types such as clusters composed of large carbonaceous spheroids (20-40 μm across each) with fluffy or foam-like envelope are identified. Finely laminated carbonaceous cherts are devoid of heavy metals and characterized by the enrichment of LREE. This chert locally contains conical to domal structures characterized by truncation of laminae and trapping of detrital grains and is interpreted as siliceous stromatolite formed by very early or contemporaneous silicification of biomats with the contribution of silica-rich hydrothermal fluids. Biological affinities of described microfossils and microbes constructing siliceous stromatolites are under investigation. However, this study emphasizes how diverse the microbial community in Paleoarchean coastal hydrothermal environment was. We propose the diversity is at least partially due to the availability of various energy sources in this depositional environment including reducing chemicals and sunlight.

New results on the stratigraphy and sedimentary environment of the Middle Jurassic strata of the Murihiku Terrane in the Waikawa district, Southland, New Zealand, are presented. This area has not been subjected to study for a long time, although the Murihiku Terrane is important to understand the Mesozoic geology of New Zealand. Stratigraphically, from bottom to top, the sequence consists of lithofacies associations A, B, C, and D, distinguished by their lithology. Lithofacies association A (250 m thick) is composed of boulder-grade conglomerate, coarse-grained massive sandstone, trough cross-stratified sandstone, and minor fine-grained sediments. Lithofacies association B (90 m thick) contains alternating beds of sandstone and siltstone and fossil-bearing massive siltstone. Lithofacies association C (280 m) consists of poorly to moderately sorted pebble-cobble conglomerates and trough or planar crossstratified sandstones. The characteristic lithofacies of lithofacies association D (>140 m) are planar cross-stratified sandstone, planar horizontally stratified sandstone, grey siltstone, and carbonaceous beds. The depositional age was deduced from bivalve fossils in lithofacies association B, which indicate a Middle Jurassic (Temaikan: BajocianCallovian) age.Paleocurrent flow directions were from the southwest in lithofacies association A and from the southeast in lithofacies associations C and D. Clast compositions also differed between lithofacies associations A and C; andesite volcanic clasts were dominant in A, and rhyolite volcanic clasts were dominant in C.The major sedimentary environments were terrestrial and shallow marine and were affected by sea-level changes. The sediments of lithofacies association B were deposited during periods of transgression and high sea level, and the boundary between lithofacies associations B and C is a depositional- sequence-bounding unconformity. Fluvial sedimentation became dominant in lithofacies associations C and D. Due to progressive aggradation of the sedimentary basin, the gradient became gentle, and the fluvial pattern changed from a braided to a meandering river. The sediment source, as determined from paleocurrent analyses and clast compositions, was also different from that of lithofacies association A. Thus, the Waikawa district sediments apparently were derived from multiple sources. The provenance of the Murihiku Terrane sediments was probably a primitive volcanic or continental margin arc. Volcanic activity in the hinterland fed large amounts of volcanic detritus to the region by flood, debris flow, and fluvial transport.