Non-marine Environments Research Articles

Middle Palaeozoic microvertebrate assemblages and biogeography of East Gondwana (Australasia, Antarctica)

Silurian vertebrate remains are rare in the Australasian region, mostly lacking from the end Ordovician to the mid-Ludlow presumably because of the purported Gondwana Ice Age. Thelodont, placoderm, acanthodian, ?stem actinopterygian, and probable chondrichthyan remains are known from eastern and western Australia and Irian Jaya. Of significance are the links between eastern Australia and China, with sinacanthid spines known only in these regions, and both having porosiform, but not punctatiform, poracanthodid acanthodians, while Western Australia, Iran and possibly Irian Jaya have similar thelodonts, all from shallow marine to evaporitic settings. Earliest Devonian (Lochkovian) vertebrate microfossils include placoderm taxa with circumArctic and Bohemian affinities, but post-Lochkovian marine assemblages comprise mainly endemic forms of turiniid thelodonts, placoderms, acanthodians, chondrichthyans, and sarcopterygians. Most of the Early Devonian marine assemblages from eastern Australia indicate tropical–subtropical depositional environments. From the Middle–Late Devonian, notable index taxa include Phoebodus spp. After the Frasnian-Famennian events, turiniids finally disappear in the Australian record, placoderms also become absent by the end of the period, acanthodians are increasingly dominated by acanthodiforms, and chondrichthyan and actinopterygian diversity increases. For the Carboniferous, vertebrate occurrences are early to mid-Mississippian, disappearing in the early Pennsylvanian in marine and non-marine environments. During the time span of IGCP 491, data on previously poorly known and many new taxa represented only by isolated remains have been analysed, and a wealth of new acanthodian taxa, a new Early Carboniferous tetrapod Ossinodus pueri, and several sarcopterygian taxa have been fully described.

Mineralogical constraints on the paleoenvironments of the Ediacaran Doushantuo Formation

Assemblages of clay minerals are routinely used as proxies for paleoclimatic change and paleoenvironmental conditions in Phanerozoic rocks. However, this tool is rarely applied in older sedimentary units. In this paper, the clay mineralogy of the Doushantuo Formation in South China is documented, providing constraints on depositional conditions of the Ediacaran Yangtze platform that host the earliest animal fossils in the geological record. In multiple sections from the Yangtze Gorges area, trioctahedral smectite (saponite) and its diagenetic products (mixed-layer chlorite/smectite, corrensite, and chlorite) are the dominant clays through the lower 80 m of the formation and constitute up to 30 wt% of the bulk rock. Saponite is interpreted as an in situ early diagenetic phase that formed in alkaline conditions (pH > or = 9). The absence of saponite in stratigraphically equivalent basin sections, 200-400 km to the south, indicates that alkaline conditions were localized in a nonmarine basin near the Yangtze Gorges region. This interpretation is consistent with crustal abundances of redox-sensitive trace elements in saponitic mudstones deposited under anoxic conditions, as well as a 10 per thousand difference in the carbon isotope record between Yangtze Gorges and basin sections. Our findings suggest that nonmarine environments may have been hospitable for the fauna preserved in the Yangtze Gorges, which includes the oldest examples of animal embryo fossils and acanthomorphic acritarchs.

Current perspectives on the Permian–Triassic boundary and end-Permian mass extinction: Preface

The end-Permian mass extinction is now robustly dated at 252.6 ± 0.2 Ma (U–Pb) and the Permian–Triassic (P–T) GSSP level is dated by interpolation at 252.5 Ma. An isotopic geochronological timescale for the Late Permian–Early Triassic, based on recent accurate high-precision U–Pb single zircon dating of volcanic ashes, together with calibrated conodont zonation schemes, is presented. The duration of the Early Triassic (Induan + Olenekian stages) is estimated at only 5.5 million years. The duration of the Induan Stage (Griesbachian + Dienerian sub-stages) is estimated at ca. one million years and the early Olenekian (Smithian sub-stage) at 0.7 million years duration. Considering this timescale, the “delayed” recovery following the end-Permian mass extinction may not in fact have been particularly protracted, in the light of the severity of the extinction. Conodonts evolved rapidly in the first 1 million years following the mass extinction leading to recognition of high-resolution conodont zones. Continued episodic global environmental and climatic stress following the extinction is recognized by multiple carbon isotope excursions, further faunal turnover and peculiar sedimentary and biotic facies (e.g. microbialites). The end-Permian mass extinction is interpreted to be synchronous globally and between marine and non-marine environments. The nature of the double-phased Late Permian extinction (at the Guadalupian–Lopingian boundary and the P–T boundary), linked to large igneous provinces, suggests a primary role for superplume activity that involved geomagnetic polarity change and massive volcanism.

Lithostratigraphy of the Upper Triassic–Middle Jurassic Shemshak Group of Northern Iran

Abstract The Upper Triassic–lower Middle Jurassic Shemshak Group is a siliciclastic unit, up to 4000 m in thickness, which is widespread across the Iran Plate of northern and central Iran. The group is sandwiched between two major unconformities: the contact with the underlying platform carbonates of the Elikah and Shotori formations is characterized by karstification and bauxite–laterite deposits; the top represents a sharp change from siliciclastic rocks to rocks of a Middle–Upper Jurassic carbonate platform–basin system. In the Alborz Mountains, the group consists of a Triassic and a Jurassic unit, separated by an unconformity, which is in part angular in the northern part of the mountain range and less conspicuous towards the south. Published lithostratigraphic schemes are based on insufficient biostratigraphic and lithological information. Here we present a new lithostratigraphic scheme for the central and eastern Alborz Mountains modified and enlarged from an unpublished report produced in 1976. Two major facies belts, a northern and a southern belt running more or less parallel to the strike of the mountain chain, can be distinguished. In the north, the Triassic part of the group is composed of the comparatively deep-marine Ekrasar Formation with the Galanderud Member (new name) at the base followed by the Laleband Formation, which represents prodelta–delta front environments. Up-section, the latter is replaced by the fluvial–lacustrine, coal-bearing Kalariz Formation. The equivalent Triassic lithostratigraphic unit in the south is the Shahmirzad Formation, redefined here, with the Parvar Member at the base. The formation represents fluvial, coastal plain and shallow- to marginal-marine environments. In the north, the Jurassic part of the group consists exclusively of the Javaherdeh Formation, coarse conglomerates of alluvial fan–braided river origin, which towards the south grades into the Alasht Formation, rocks of fluvial–lacustrine origin with coal. Further south, the Alasht Formation represents intertonguing marginal-marine–flood-plain environments and is followed by the Shirindasht Formation, sandstones and siltstones, indicative of the storm-dominated shelf, and the Fillzamin Formation (new), which is characterized by comparatively deep-marine shales. In the south, the group ends with the Dansirit Formation of deltaic–coastal-plain origin. This lithostratigraphic scheme reflects the tectono-sedimentary evolution of the Shemshak Foreland Basin of the Alborz Mountains where, during the Late Triassic, a relict marine basin in the north became gradually infilled, whereas in the south non-sedimentation and subaerial erosion prevailed and sediments record largely non-marine–marginal-marine conditions. During the early Lias, the basin was filled with erosional debris of the rising Cimmerian Mountain Chain, deposited largely in non-marine environments. During the early Middle Jurassic, in contrast, rapid subsidence in the south resulted in the deepening and subsequent infilling of a marine basin.

Structures and sedimentary deposition in the Sunda Strait, Indonesia

The Sunda Strait lies between the islands of Java and Sumatra and separates the nearly orthogonal subduction along the south of Java and oblique subduction beneath Sumatra. The Sumatra fault accommodating most of the trench parallel shear of the oblique subduction initiates in the Sunda Strait. This setting implies that the Sunda Strait is an attractive area to study the geodynamic evolution of the western Indonesian region. Thirteen multichannel seismic lines acquired in the Sunda Strait have allowed a detailed study of the structure, sedimentation patterns and volcanic activities that occurred in the Sunda Strait. The Sunda Strait evolution has been strongly tied with the development of the Sumatra fault in this area. The opening of the Sunda Strait initiated in the early Late Miocene following the commencement of the Sumatra fault system in the Middle Miocene. Since then, three major graben systems have been evolved, which are referred to as the West and East Semangko Grabens, and the Krakatau Graben. These graben systems can be regarded as pull-apart basins developed within the releasing fault overstep area in between the main strand of the Sumatra fault and its relay faults south off Ujung Kulon. Prior to the Late Miocene most of the Sunda Strait and the surroundings probably developed in a non-marine environment. In Late Miocene the Sunda Strait started to open and volcanism began and has been the main source of clastics. Three major sedimentary units can be identified which represent Late Miocene, Pliocene and Pleistocene sediments respectively. The Late Miocene unit has been developed in the shelfal area on top of the Middle Miocene unconformity following a relative rapid sea level rise, and a subsequent highstand prior to the sea level fall at the end of Miocene. Its lower part has syn-structurally been deposited into the Late Miocene basement block faulting. The early deposition of the Pliocene unit was in response to the Pliocene sea level rise and abundant clastic supply. The deposition became very rapid due to graben formation combined with stronger volcanism. However, its lateral distribution was confined by uplift of ridges within the grabens.

Upper Tertiary non-marine environments and climatic changes in Iceland

Upper Tertiary non-marine environments and climatic changes in Iceland

Latest Carboniferous–earliest Permian transgressive deposits in the Paganzo Basin of western Argentina: Lithofacies and sequence stratigraphy of a coastal-plain to bay succession

The upper Paleozoic rocks of Gondwana record a complex paleoclimatic history related to the migration of the supercontinent over high latitudes. Changes in climate and relative sea level can be traced through detailed sedimentologic and sequence-stratigraphic analysis. Our study focuses on transgressive deposits of Stephanian–Early Permian age in the lower member of the Tupe Formation with the objective of characterizing lithofacies and sedimentary environments within a sequence-stratigraphic framework in order to achieve a better understanding of the sedimentary history of the Paganzo Basin and the nature of transgressive deposits. Sixteen lithofacies grouped in eight assemblages were defined and arranged in two complete sequences. A sequence boundary (SB) is identified at the base of the Tupe Formation. Coastal-plain deposits capped by marine embayment lithofacies are included within sequence 1. A relative sea-level fall (SB) is recorded by an abrupt change into braided alluvial-plaine deposits (LST). The beginning of the TST is characterized by the appearance of coal and deltaic lithofacies. Late TST deposits occur above a ravinement surface and comprise bay-margin to distal-bay deposits forming a retrogradational stacking package. These lithofacies are replaced upwards by HST deposits. A relative sea-level fall (SB) is recorded by the presence of fluvial deposits overlying marine lithofacies. The Tupe Formation illustrates the transition of a coastal-plain to a marine embayment. The detection of a transgressive surface within the coastal-plain deposits of sequence 1 expanded significantly the volume of deposits now included as part of the latest Carboniferous–earliest Permian transgression, and underscores the importance of searching for transgressive signatures in non-marine environments. The presence of two sequences supports a punctuated shoreline trajectory with an overall retrogradational stacking pattern. An abrupt relative sea-level fall and increased aridity is recorded at the end of the transgressive event.

Physiological activity of Porphyra in relation to eulittoral zonation

Eulittoral seaweeds at different tidal elevations are exposed to various frequencies and durations of emergence. Their physiological activities (e.g. nutrient uptake) may be affected by water loss during emersion. We used three Porphyra species from different tidal elevations to test whether species at different vertical elevations on the shore respond differently to the increasingly non-marine environment, in terms of their physiological activities including nutrient uptake, tissue carbon, nitrogen and phycoerythrin contents. Simulated tidal cycles produced water losses of 0%, 40 ± 10% and 90 ± 5% tissue water. Emersion was stressful for all species regardless of their habitat. It was more stressful to nitrate and phosphate uptake for the sublittoral species P. yezoensis than eulittoral species, P. umbilicalis and P. leucosticta. Interestingly, tissue N for thalli that had been emerged and then re-submerged was significantly higher than those of continuously submerged individuals. During exposure, tissue N contents of all species declined but recovered quickly (e.g. within 30 min) after re-submergence. This result suggests that emersion-induced N release may constitute an undescribed biogeochemical pathway linking marine, terrestrial, and atmospheric N reservoirs.

The nonmarine environment of Quaternary foraminifers in Yanghuzhuang, China: Evidence from boron and strontium isotopes

The concentrations and isotopic compositions of boron and strontium of Quaternary foraminifers and bivalve fossils collected in the Yanghuzhuang section of Yanqing, Beijing and of modern gastropods living in the Guishui River and of river water were measured. The concentrations and isotopic compositions of Quaternary foraminifers and bivalve fossils differed from those of modern marine foraminifers and were similar to those of modern terrestrial gastropods from the Guishui River. These results indicate that early Quaternary foraminifers in the Yanghuzhuang section inhabited a nonmarine environment and that these foraminifers were not the result of a transgression or sea flooding. The foraminifers were not special halobios and can survive in the terrestrial condition that resembled those of the ocean.

A review of the Carboniferous colonisation of non-marine environments by ostracods

This review examines the nature and chronology of the transition of ostracods from marine to non-marine aquatic environments in the Devonian and Carboniferous. There is putative evidence of ostracods in brackish waters from the middle Silurian, but more robust evidence from the Devonian. The first putative freshwater ostracods are species of the generaCarbonita andGeisina which are found in the early to middle Carboniferous Coal Measures. Freshwater ostracods are common in the middle Pennsylvanian Coal Measures of late Carboniferous age, with species of genera such asDarwinula, Carbonita, Candona andCypridopsis. The Lower Carboniferous Visean succession from the Midland Valley of Scotland provides a unique range of sedimentary environments from marine to non-marine, and a diverse range of ostracods and macrofauna. It is an ideal sequence to study the radiation of the Ostracoda from marine to non-marine realms. Non-marine species ofCarbonita are found in the lower Visean, associated with spirorbids,Naiadites, Estheria, plant and fish fragments. Marginal marine species include the generaGeisina, Parapar-chites, Sbemonaella andCapellina, all of which are eurytopic. The first non-marine environments occupied by ostracods were near the shoreline, and influenced by marine transgressions. The adaptations needed to survive in freshwater or low salinities would have included changes in osmoregulation, feeding, and reproductive strategies such as parthenogenesis, to enable opportunistic colonisation of temporary freshwater habitats such as seasonal pools.

Actinorhodopsins: proteorhodopsin‐like gene sequences found predominantly in non‐marine environments

Proteorhodopsins are light-energy-harvesting transmembrane proteins encoded by genes recently discovered in the surface waters of the world's oceans. Metagenomic data from the Global Ocean Sampling expedition (GOS) recovered 2674 proteorhodopsin-related sequences from 51 aquatic samples. Four of these samples were from non-marine environments, specifically, Lake Gatun within the Panama Canal, Delaware Bay and Chesapeake Bay and the Punta Cormorant Lagoon in Ecuador. Rhodopsins related to but phylogenetically distinct from most sequences designated proteorhodopsins were present at all four of these non-marine sites and comprised three different clades that were almost completely absent from marine samples. Phylogenomic analyses of genes adjacent to those encoding these novel rhodopsins suggest affiliation to the Actinobacteria, and hence we propose to name these divergent, non-marine rhodopsins 'actinorhodopsins'. Actinorhodopsins conserve the acidic amino acid residues critical for proton pumping and their genes lack genomic association with those encoding photo-sensory transducer proteins, thus supporting a putative ion pumping function. The ratio of recA and radA to rhodopsin genes in the different environment types sampled within the GOS indicates that rhodopsins of one type or another are abundant in microbial communities in freshwater, estuarine and lagoon ecosystems, supporting an important role for these photosystems in all aquatic environments influenced by sunlight.

Global diversity of cumaceans & tanaidaceans (Crustacea: Cumacea & Tanaidacea) in freshwater

Cumacea and Tanaidacea are marginal groups in continental waters. Although many euryhaline species from both groups are found in estuaries and coastal lagoons, most occur only temporarily in non-marine habitats, appearing unable to form stable populations there. A total of 21 genuinely non-marine cumaceans are known, mostly concentrated in the Ponto-Caspian region, and only four tanaids have been reported from non-marine environments. Most non-marine cumaceans (19 species) belong in the Pseudocumatidae and appear restricted to the Caspian Sea (with salinity up to 13%) and its peripheral fluvial basins, including the northern, lower salinity zones of the Black Sea (Sea of Azov). There are nine Ponto-Caspian genera, all endemic to the region. Only two other taxa (in the family Nannastacidae) occur in areas free of any marine-water influence, in river basins in North and South America. Both seem able to survive in waters of raised salinity of the lower reaches of these fluvial systems; but neither has been recorded in full salinity marine environments. The only non-marine tanaidacean thus far known lives in a slightly brackish inland spring in Northern Australia. The genus includes a second species, from a brackish-water lake at the Bismarck Archipelago, tentatively included here as non-marine also. Two additional species of tanaidaceans have been reported from non-marine habitats but both also occur in the sea.

Ostracods, ancient and modern: a review of John Neale’s scientific contribution

SUMMARY During a professional career of 42 years, John Neale published 106 scientific papers and book chapters, and edited 5 books, mainly concerning the bivalved crustacean group Ostracoda. Although dominantly taxonomic in nature, this body of work encompasses an extraordinary range of material, both living and fossil, from late Jurassic to modern in age, from a range of marine and non-marine environments, and demonstrates a pioneering combination of palaeontological and zoological methods.

Did the Mediterranean marine reflooding precede the Mio–Pliocene boundary? Paleontological and geochemical evidence from upper Messinian sequences of Tuscany, Italy

The events related to the Messinian salinity crisis are among the most deeply investigated of Earth's history. According to the current hypothesis of Neogene paleogeographic evolution, approximately 5.5 Ma ago, after evaporitic sedimentation and before the Mio–Pliocene boundary, the Mediterranean was characterized by the widespread development of non-marine environments inhabited by molluscs and ostracods of brackish affinity. The Messinian post-evaporitic deposits that testify such a dramatic environmental change are commonly referred to as ‘Lago-mare’ and have been reported from several outcrops and boreholes throughout the entire Mediterranean basin. The origin of ‘Lago-mare’ conditions is commonly interpreted as the result of the synergistic effect of both the humid climatic conditions and change of the drainage patterns at the Mediterranean scale, with the capture of Paratethyan brackish waters. A few recent studies, however, suggest that such a scenario probably represents an oversimplification of the original context, from both a paleogeographical and paleoenvironmental point of view. Unfortunately, the results of these studies have never been commonly accepted and the proposed evidences have been considered questionable. In this paper we describe the fish assemblages from the ‘Lago-mare’ deposits of two localities, Cava Serredi and Podere Torricella, located in the Neogene hinterland basins of Tuscany, central Italy. These assemblages consists of a mixture of marine euryhaline and stenohaline taxa suggesting that the depositional environments were characterized by permanently open connections with a marine basin filled with normal marine waters. In order to better define the paleontological significance of these upper Messinian fish assemblages, the oxygen, carbon and strontium isotopic composition of fish otoliths and other fossils has been measured. These isotopic compositions are strongly indicative of the presence of normal marine conditions close to the depositional environments testified by the sedimentary sequences, thereby implying that the interpretation of the geochemical results are consistent with those derived from the paleoecological analyses of the fish assemblages. Based on the integrated paleoichthyological–geochemical approach discussed in this paper it is possible to unambiguously demonstrate that normal marine rather than fresh- or brackish waters were present in the Mediterranean at least during the upper part of the ‘Lago-mare’ event, providing an unquestionable evidence that the marine refilling of the basin preceded the Mio–Pliocene boundary.

Stratal architecture and origin of lateral accretion deposits (LADs) and conterminuous inner-bank levee deposits in a base-of-slope sinuous channel, lower Isaac Formation (Neoproterozoic), East-Central British Columbia, Canada

In the Castle Creek study area, a vertically dipping, 2.5 km-thick succession of basin-floor to base-of-slope Neoproterozoic rocks are superbly exposed. In part of that outcrop, inner-bend (point-bar) deposits of sharp-based, laterally accreting sinuous channels are exposed, of which one is described in detail (Isaac Channel unit 2.2—IC2.2). IC2.2 is up to 13 m thick and extends laterally for at least 400 m. Lateral-accretion deposits, or simply lateral accretion deposits (LADs), are inclined at 7–12° toward the channel base and are about 120–140 m long. Grain size changes little obliquely upward along an individual LAD, or vertically upward through the channel-fill. LADs consist of two repeating and interstratified kinds: coarse-grained LADs consisting of strata up to granule conglomerate, and fine-grained LADs composed of thin- to medium-bedded finer-grained turbidites. In the lower part of the channel-fill, strata consist only of amalgamated coarse-grained LADs composed of decimetre-thick beds composed of very coarse sandstone/granule conglomerate that grade upward to medium sandstone. Tractional sedimentary structures are absent and fine-grained strata, specifically mudstone, occur only as isolated patches of intraclast breccia. In the upper part of the channel-fill, however, LADs consist of a rhythmic interfingering of coarse- and fine-grained LADs. Coarse-grained LADs consist of 2–3 bed-thick packages that are separated and then pinch-out rapidly into fine-grained LADs. Close to their up-dip pinch-out these coarse strata consist commonly of poorly sorted, ungraded very coarse sandstone/granule conglomerate overlain abruptly by planar-laminated or medium-scale (dune) cross-stratified, medium-grained sandstone. Fine-grained LADs are composed of mudstone interbedded with thin- and medium-bedded T bcd and T cd turbidites that obliquely downward and become truncated as the super- and subjacent coarse-grained LADs amalgamate. The rhythmic intercalation of coarse- and fine-grained LADs is interpreted to be related to temporal changes in the nature of sediment deposition along the point-bar of a deep-marine sinuous channel. Following failure along the cut-bank margin (outer bend), deposition of coarse-grained sediment on the point-bar (inner bend) occurred in order to re-establish an equilibrium channel geometry, and thereby equilibrium sediment transport conditions (i.e. sediment bypass). Once equilibrium was re-established deposition of finer, thinner-bedded strata of the succeeding fine LAD resumed. These strata represent deposition from the dilute tail region of flows that for the most part had already transited that particular channel bend and transported the bulk of its coarse sediment further down-dip. This history of alternating coarse and fine-grained sedimentation was repeated several times in the channel bend as it migrated laterally. Moreover, in coarse LADs, the restricted occurrence of tractional sedimentary structures close to their up-dip pinch-out suggests that although suspension deposition may have dominated over much of the lateral accretion surface, it was succeeded, at least on the upper part of the lateral accretion surface, by sediment reworking and bed-load transport, possibly related to elevated turbulent stresses caused by mixing along the sharp density interface in a strongly stratified turbulent flow. Although seemingly similar to LADs reported from fluvial point-bars, deep-marine LADs of the Windermere exhibit many important differences. Some of these differences are likely related to the differences in the mode of sand (and coarser) sediment transport in deep-marine versus non-marine environments, specifically, suspension versus bed load, respectively. In addition, fundamental differences in the flow structure between subaqueous suspension currents and open-channel flows most probably exert an additional first-order control contributing to these differences.

Tetrapod Ichnofacies: A New Paradigm

We recognize three fundamental terms in ichnology: (1) ichnoassemblage, which is an assemblage of ichnofossils conceptually equivalent to an assemblage of body fossils; (2) ichnocoenosis, which is a trace fossil assemblage produced by a biological community that can be characterized by morphological criteria; and (3) ichnofacies, which refers to recurrent ichnocoenoses that represent a significant portion of Phanerozoic time. There are two different kinds of ichnofacies, ethoichnofacies (mostly invertebrate ichnofacies) and biotaxonichnofacies (mostly tetrapod ichnofacies). Nonmarine invertebrate ichnologists now recognize five archetypal ichnofacies (Mermia, Skolithos, Scoyenia, Coprinisphaera, Psilonichnus) to which we add the Octopodichnus ichnofacies. We propose a coherent and consistent classification and nomenclature for tetrapod ichnofacies. We name five archetypal vertebrate ichnofacies for nonmarine environments: Chelichnus, Grallator, Brontopodus, Batrachichnus and Characichnos ichnofacies.

Genuine modern analogues of Precambrian stromatolites from caldera lakes of Niuafoʻou Island, Tonga

Calcareous or dolomitic, often secondarily silicified, laminated microbial structures known as stromatolites are important keys to reconstruct the chemical and biotic evolution of the early ocean. Most authors assume that cyanobacteria-associated microbialitic structures described from Shark Bay, Western Australia, and Exuma Sound, Bahamas, represent modern marine analogues for Precambrian stromatolites. Although they resemble the Precambrian forms macroscopically, their microstructure and mineralogical composition differ from those characterizing their purported ancient counterparts. Most Precambrian stromatolites are composed of presumably in situ precipitated carbonates, while their assumed modern marine analogues are predominantly products of accretion of grains trapped and bound by microbial, predominantly cyanobacterial, benthic mats and biofilms and only occasionally by their physicochemical activity. It has therefore been suggested that the carbonate chemistry of early Precambrian seawater differed significantly from modern seawater, and that some present-day quasi-marine or non-marine environments supporting growth of calcareous microbialites reflect the hydrochemical conditions controlling the calcification potential of Precambrian microbes better than modern seawater. Here we report the discovery of a non-marine environment sustaining growth of calcareous cyanobacterial microbialites showing macroscopic and microscopic features resembling closely those described from many Precambrian stromatolites.

Permian tetrapod ichnofacies

Abstract Three fundamental terms in ichnology are: (1) assemblage, which is equivalent to an assemblage of body fossils; (2) ichnocoenosis, which is a trace fossil assemblage produced by a biological community that can be characterized by morphological criteria; (3) ichnofacies, which refers to recurrent ichnocoenoses that represent a significant portion of Phanerozoic time. There are five archetypal vertebrate ichnofacies for non-marine environments ( Chelichnus, Grallator, Carichnium, Batrachichnus, Characichichnos ) of which four are present in the Permian: (1) Chelichnus ichnofacies — Chelichnus ichnocoenosis; (2) Batrachichnus ichnofacies — Batrachichnus ichnocoenosis; (3) Brontopodus ichnofacies — Pachypes ichnocoenosis; (4) Characichichnos ichnofacies — Serpentichnus ichnocoenosis. The Chelichnus and Characichichnos ichnofacies occur throughout the Permian, the Batrachichnus ichnofacies is restricted to the Early Permian and the Brontopodus to the Middle to Late Permian. The Batrachichnus ichnocoenosis can be divided into the Ichniotherium sub-ichnocoenosis, Amphisauropus sub-ichnocoenosis and the Dimetropus subichnocoenosis, which represent a spectrum of non-marine environments from alluvial fan to tidal flat.

Eocene stratigraphic succession in the Eucla Basin of South Australia and correlation to major regional sea-level events

Using palynostratigraphy combined with analysis of lithostratigraphy and sedimentary facies of discontinuous outcrops and selected drillholes, we have investigated whether the Eocene sequences and their boundaries in the Eucla Basin of South Australia were synchronous with major sea-level events. The correlation of Eocene sequences and their boundaries in the eastern nearshore and onshore Eucla Basin indicates that these complex marine–nonmarine strata fall into four sequences or allostratigraphic packages that can be seen from the offshore basin to nearshore and onshore basin, including palaeovalleys. Key sedimentary surfaces (disconformities, a tidal/wave ravinement surface, transgressive surfaces, maximum flooding surfaces) bound the packages (including three new revised units) and are coincident with four third-order sequence boundaries. The eastern Eucla Basin stratigraphy accords with the general view of Eocene sea-level patterns and elucidates a stepwise evolution of marine and nonmarine environments.

Evidence that Early Carboniferous ostracods colonised coastal flood plain brackish water environments

A study of the stable isotope composition ( δ 18O, δ 13C) of biogenic (ostracod, mollusc) and authigenic carbonates in the Ballagan Formation, Lower Carboniferous of Scotland, coupled with evidence from sedimentology and associated fossil fauna and flora, supports the argument that this formation was deposited in a coastal flood plain setting, in brackish (0.5 < 30‰ NaCl) and hypersaline (> 40‰ NaCl) waters, but in the absence of persistent normal marine conditions. The oxygen isotope data from the Ballagan Formation divide into three clusters: a diagenetic field defined by low δ 18O (< − 11‰ VPDB); an intermediary field ( δ 18O − 11‰ to − 9‰) composed of a mixture of known primary and secondary (diagenetic) carbonates; and samples within the range of − 9‰ to − 4‰ which, as far as we can ascertain, are largely unaltered. No samples give typical Early Carboniferous δ 18O marine values. Average marine carbonates from Europe have δ 18O between − 4‰ to − 3‰. The Ballagan Formation carbonates were probably deposited in evaporated freshwater and/or brackish water. This conclusion is supported by the presence of evaporites (gypsum, anhydrite, halite pseudomorphs) and common desiccation-cracked mudstone surfaces throughout the Ballagan Formation, suggesting conditions of fluctuating salinity in ephemeral bodies of water. The stable isotope data support the notion that the ostracod assemblages of the Ballagan Formation were colonising brackish water and hypersaline ecologies on a coastal flood plain during the Early Carboniferous, a stage of development that may have encouraged their colonisation of fully non-marine (limnetic) environments during the later Carboniferous. The ostracods include cytherellacean and kloedenellacean species known from marginal marine sites elsewhere, but probably tolerant of brackish water, podocopid species such as ‘ Bythocypris’ aequalis that may have been adapted for brackish water settings on coastal flood plains (ephemeral lakes and lagoons), and paraparchitacean-dominated assemblages that may signal harsh (hypersaline or desiccating) environments.