Context Examining Australia’s late Quaternary subfossil record can be valuable in assessing whether the current diversity of small-bodied mammals seen across some parts of northern Australia is ‘normal’. Such records are important for establishing baselines for measuring historic changes in communities today and into the future. These datasets are becoming increasingly important, given trajectories in current global climate change, and predicted habitat losses and other potential anthropogenic impacts. Aims The main aim of this study is to utilise the local subfossil record from north-eastern Australia to establish a natural baseline for assessing changes in small mammal communities post-European colonisation. Methods Subfossils of vertebrates and other taxa were recovered from surface deposits adjacent to cave entrances at Broken River, near Greenvale in north-eastern Queensland, and were subjected to taxonomic, taphonomic and statistical analyses. These were then compared with local faunal records from modern surveys to compare differences in faunal communities between past and present. Key results Radiocarbon dating showed that these subfossils are geologically young, dating to approximately the time of European colonisation. We provide evidence for the former presence of extinct species of hopping mice (Notomys spp.) and rabbit rats (Conilurus spp.) in the region. Additional locally extirpated taxa such as Cape York bandicoot (Isoodon peninsulae) and Shark Bay mouse (Pseudomys gouldii) demonstrated considerable range contractions since the deposits accumulated, compared with their current distribution. Independent evidence from subfossil land snails recovered from these deposits is, with two exceptions, all modern-day vine thicket, karst-dwelling species indicating a long-term maintenance of vine thicket habitat. Thus, the loss of several mammal species is unlikely to be the result of habitat loss. Conclusions Analysis of the surface deposits showed that local historic small-mammal communities were much more diverse than are the region’s extant faunas recorded by modern surveys. Many extinctions and extirpations evidently occurred prior to such faunas being recorded as local inhabitants of the region. Implications Our data suggested that post-European colonisation small-mammal losses are likely to be substantially worse than previously realised.

Coral reefs are among the most important marine habitats but face significant threats from anthropogenic sources, including climate change. This paper reviews and compares the modern Great Barrier Reef Province and the 360-million-year-old Devonian Great Barrier Reef of western Australia. Despite occurring at times with different climates, biota (both marine and terrestrial), weathering processes and marine chemistry, similar reefs were constructed under certain circumstances. Major differences in global temperature, marine carbonate saturation, sea level behavior and reef community constituents were evaluated. The comparison highlights the integration of, and interdependencies within, reef communities and the need for both carbonate producers and significant binders, whether skeletal or microbial, to construct a reef in a high-energy setting. Devonian communities with abundant corals and skeletal sponges were incapable of making modern reef types without competent binders to unify framework into rigid substrate. The current strong focus on corals and bleaching in modern reef conservation may be obscuring the equally significant issue of ocean acidification, which impacts on equally crucial framework unification, i.e., hard binding by coralline algae and microbialites and early cementation. The comparison also supports the idea that ‘empty bucket’ carbonate platform morphologies require increased accommodation from high-amplitude icehouse sea level oscillations.

Natural ecosystems are routinely impacted by acute disturbances that generate space for early colonizers. Following disturbances, the interaction strengths of top‐down and bottom‐up factors across environmental gradients influence community succession. On coral reefs, rubble beds commonly form following major disturbances and can persist for decades. Yet, there is little understanding of the successional pathways that lead to rubble binding—where rubble is bound and consolidated to form stable substrate suitable for coral recruitment—and subsequent coral recovery. This study used observational and experimental methods to determine: (1) binding likelihood in unstabilized in situ rubble beds 2.5 years following a coral bleaching event in 2016 in the Maldives, and how it varied according to rubble characteristics across environmental gradients; and (2) how the number of binds and binder community composition on experimentally stabilized rubble varied temporally over 1.5 years across environmental gradients. Surveys of rubble beds found that binding was lowest on the reef flat (8% of rubble was bound) and highest at exposed deeper sites (38%), where flow appears low enough to maintain rubble stability but high enough to support binder growth. When experimentally stabilized, ~100% of rubble was bound by at least one bind within 6 months. Yet, while the number of binds per rubble piece in experimental units continued to increase over time on the reef slope, it remained low on the reef flat, and binder community composition was distinct between reef flat and slope—likely due to higher sediment transport on the reef flat. Community composition also was distinct between exposed and cryptic rubble microhabitats. On reefs where rubble is mobilized more frequently than every 6 months, rubble beds will likely have low binding potential and delayed coral recruitment. Where sediment flux and deposition is high, recovery is unlikely even if rubble is actively stabilized. In contrast, infrequently mobilized areas with lower sediment flux are more likely to facilitate natural binding and coral recovery, and thus may not require intervention. Our findings can help to effectively guide managers toward the best strategies that facilitate the recovery of rubble‐dominated coral reefs, while optimizing limited intervention resources through careful prioritization.

The Great Barrier Reef (GBR) is assumed to be a tectonically stable area, but recent studies show that neotectonic activity could have affected the geomorphology and evolution of the coral reefs. We used bathymetry, free-air gravity and 2D seismic data to test the hypothesis that neotectonic (i.e. geologically recent or currently active) faults have affected the morphology and major aspects of reefs’ growth in the northernmost zone of the GBR, 13.5°S–10.5° S. Bathymetry data show that elongated reef platforms, oriented WNW-ESE, are systematically deflected at their ends or, in some cases, offset through their bodies, along interpreted structural lineaments. Submarine stream channels, running mostly in WNW-ESE orientations, have deepened their courses within the areas occupied by elongated platforms. The deflection or offset of the coral reefs is interpreted to result from movement on neotectonic faults based on the following lines of evidence: (1) fault lineaments based on reef platform morphology are almost parallel to those interpreted from free-air gravity data, consistent with deep-seated faults; (2) offsets along the deflected zones of reef platforms are oriented sub-parallel to interpreted fault lineaments, consistent with those faults having deformed reef morphology since reef initiation; (3) some inferred fault positions correspond to faults interpreted from limited 2D seismic reflection data; (4) fluvial incision of the continental shelf between elongated reefs is consistent with neotectonic fault activity; and (5) M > 4 earthquakes have been recorded adjacent to some interpreted lineaments. We propose that the GBR has been affected by localised active tectonism in different ways. Small, localised faults active in the late Pleistocene displaced and deflected coral reefs laterally in the northernmost zone of the GBR. In the central zone of the GBR larger (NNE-SSW trending) bounding faults controlled regional subsidence, thus affecting accommodation and broader reef growth patterns. Our results suggest that recently active faults in the GBR have had, and may continue to have, important ramifications for the developmental history of the reef province. These findings are significant given that the assumption of tectonic stability underpins many interpretations of the potential effects of changing climate and sea level on reef growth.

Stromatoporoids were major reef-builders during the middle Paleozoic; however, no Carboniferous stromatoporoid reefs have been reported. The Akiyoshi Limestone Group of southwest Japan formed on a seamount in the Panthalassa Ocean from the Mississippian (Visean) to the middle Permian (Capitanian). The Early Pennsylvanian (Bashkirian) reef-core setting was well developed and laterally differentiated into several reef environments. Laminated skeletons made up of cystose or flat laminae and pillar-like vertical structures were abundant and, together with Chaetetes, contributed greatly to reef construction in most reef-core environments. The morphology of the laminated skeletons clearly indicates a stromatoporoid, probably labechiid, affinity. Thus, a lineage of reef-building stromatoporoids reappeared on a Panthalassan seamount in a locally warm-water tropical setting after the Late Devonian extinctions. Ongoing global glaciation may have resulted in enhanced ocean circulation, upwelling, and nutrient supply, especially around shallow-water seamounts, culminating in elevated carbonate saturation, which should have favored hypercalcified stromatoporoids and Chaetetes. The Chaetetes-stromatoporoid reefs remained in the Moscovian, but probably died out during the Kasimovian with intensive global cooling and frequent subaerial exposure, to be replaced by Palaeoaplysina-phylloid algal reefs. The occurrence of Bashkirian reef-building stromatoporoids indicates that Paleozoic stromatoporoids continued as reef-builders long after the Late Devonian extinction, at least in Panthalassa. This occurrence emphasizes the significance of rarely preserved open, but isolated oceanic settings like Akiyoshi for global biogeography and evolution.

The Phanerozoic surface ocean is characterized by its high dissolved oxygen content owing to mixing with the atmosphere. However, atmospheric oxygen levels varied in the early Paleozoic and it remains unclear whether the surface ocean was susceptible to significant redox fluctuations in response to extreme environmental events. In this study, we probed the redox structures of shallow middle Cambrian marine depositional environments across the North China Platform, ranging from open tidal flats to relatively deep subtidal environments. We utilized a combination of least diagenetically altered carbonate materials (such as ooid cortices, calcimicrobes, and their fringing cements), as well as in situ element measurement and imaging techniques. By analyzing a set of redox-related elements (e.g., Ce anomaly, Zn/Fe molar ratio, Mn and Cr) and mineralogical proxies (hydrogenetic Fe oxides), we revealed a stratified redox structure in the Drumian surface oceans. Compared to earlier Drumian conditions, late Drumian surface oceans experienced significant intrusions of ferruginous waters, probably reaching into shallow subtidal environments with water depths less than 10 m. Furthermore, we identified shallow subtidal microbial O-2-producing factories, characterized by dendritic Epiphyton thalli. These calcimicrobes exhibited more oxygenated signatures (negative Ce anomalies and enrichment of hydrogenetic Fe oxides) relative to contemporaneous less oxic shallower and deeper environments. This finding indicates that they produced oxygen oases or refuges during periods of both normal and poor dissolved O-2 conditions. This study has the potential to broaden our understanding of redox conditions and microbial oxygen-producing mechanisms in the surface ocean, particularly during intervals characterized by low atmospheric oxygen levels or episodic anoxic events.

The initiation of the Holocene Great Barrier Reef coincided with rapid environmental change as sea level rose and inundated the shelf. Core data from One Tree Reef (southern Great Barrier Reef) shows coral growth started by -8.2 ka, but accretion between 8 and 7 ka was slower, occurred in deeper water, and comprised more sediment-tolerant coral communities compared to growth following sea-level stabilization. It has been postulated that environmental stressors (e.g. increased turbidity and nutrients) suppressed and delayed reef growth, however direct data supporting this hypothesis are scarce. Here we combine the isotopic composition of skeletal bound organic nitrogen (815N) and Ba/Ca ratios of coral skeletons with published geochemical proxies of terrestrial sediment discharge to constrain Holocene water conditions at One Tree Reef. Between 8 and 7 ka the skeletal 815N values from multiple corals and genera were elevated (average of 8.45 +/- 0.89%o) relative to the early transgression and following sea-level stabilization (average of 7.04 +/- 0.82%o). We propose that elevated 815N in corals reflects the discharge of deep terrestrial soil nitrogen resulting from high runoff. This is supported by Ba/Ca measurements and published rare earth element and yttrium (REE + Y) geochemical proxies in coral and reefal microbialites from the same cores. These data suggest that increased terrigenous discharge of sediment and nutrients did not inhibit reef growth, rather led to the establishment of slower-growing, deeper and more sediment-tolerant coral communities. Understanding the capacity for reef growth under adverse environmental conditions provides insight into thresholds and resilience of the GBR over centennial-millennial timescales.

The proportional cover of rubble on reefs is predicted to increase as disturbances increase in intensity and frequency. Unstable rubble can kill coral recruits and impair binding processes that transform rubble into a stable substrate for coral recruitment. A clearer understanding of the mechanisms of inhibited coral recovery on rubble requires characterisation of the hydrodynamic conditions that trigger rubble mobilisation. Here, we investigated rubble mobilisation under regular wave conditions in a wave flume and irregular wave conditions in situ on a coral reef in the Maldives. We examined how changes in near-bed wave orbital velocity influenced the likelihood of rubble motion (e.g. rocking) and transport (by walking, sliding or flipping). Rubble mobilisation was considered as a function of rubble length, branchiness (branched vs. unbranched) and underlying substrate (rubble vs. sand). The effect of near-bed wave orbital velocity on rubble mobilisation was comparable between flume and reef observations. As near-bed wave orbital velocity increased, rubble was more likely to rock, be transported and travel greater distances. Averaged across length, branchiness and substrate, loose rubble had a 50 % chance of transport when near-bed wave orbital velocities reached 0.30 m s−1 in both the wave flume and on the reef. However, small and/or unbranched rubble pieces were generally mobilised more and at lower velocities than larger, branched rubble. Rubble also travelled further distances per day (∼2 cm) on substrates composed of sand than rubble. Importantly, if rubble was interlocked, it was very unlikely to move (< 7 % chance) even at the highest velocity tested (0.4 m s−1). Furthermore, the probability of rubble transport declined over 3 d deployments in the field, suggesting rubble had snagged or settled into more hydrodynamically stable positions within the first days of deployment. We expect that snagged or settled rubble is transported more commonly in locations with higher-energy events and more variable wave environments. At our field site in the Maldives, we expect recovery windows for binding (when rubble is stable) to predominantly occur during the calmer north-eastern monsoon when wave energy impacting the atoll is less and wave heights are smaller. Our results show that rubble beds comprised of small rubble pieces and/or pieces with fewer branches are more likely to have shorter windows of recovery (stability) between mobilisation events, and thus be good candidates for rubble stabilisation interventions to enhance coral recruitment and binding.

Late Pleistocene to Holocene-aged microfaunal assemblages are rarely reported in Australia despite their critical importance for palaeoecological studies, as well as their bearing on the megafaunal extinction debate. Capricorn Caves, central-eastern Queensland, hosts three Late Pleistocene to Holocene deposits containing significant faunal records. Excavations were conducted on these deposits over several seasons, with analyses of recovered material ongoing. Here, we report interim results and explore their implications for our understanding of the microfaunal record of central eastern Queensland. Fern Chamber was previously dated using U-series to the Holocene (> 7.6 +/- 0.2 ka). Honeymoon Suite was dated to > 6.4 +/- 0.2 ka using U-series. However, new charcoal dates from the deposit span approximately 7.5-15.5 ka, although the association between charcoal and fauna is unresolved. The fauna is likely Holocene. Colosseum Chamber is the oldest of the deposits, and new single-grain luminescence ages and age-depth modelling suggest that the deposit likely spans MIS 1-4. We use abundant fragmentary rodent remains to examine palaeoenvironmental change over this period. Carbon and oxygen isotope analyses of rodent incisor fragments reveal broad diets within the rodent community, and significant differences in precipitation between glacial and interglacial conditions. Rodent long bone histological analyses indicate significant differences in bone metabolism at the family level between the MIS 3 and 2 samples, but not MIS 1. We suggest that these data support evidence for a mid-Holocene arid anomaly in the region, and increased aridity through the Holocene relative to the terminal Pleistocene. The sites contain at least 10 small mammal species either globally extinct or locally extirpated, including the Capricorn rabbit-rat (Conilurus capricornensis), the white-footed rabbit-rat (Conilurus albipes), the plains mouse (Pseudomys australis), Gould's mouse (Pseudomys gouldii), Forrest's mouse (Leggadina forresti), the long-tailed hopping mouse (Notomys longicaudatus), swamp rat (Rattus lutreolus), the white-tailed rat (Uromys caudimaculatus), the narrow-nosed planigale (Planigale tenuirostris), the Liverpool Plains striped bandicoot (Perameles fasciata), the Cape York brown bandicoot (Isoodon peninsulae), and the southern brown bandicoot (Isoodon obesulus). We also record significant range contractions for frogs (Philoria sp., Neobatrachus sp.) and earless dragons (Tympanocryptis sp.). This study demonstrates that significant changes in the microfaunal community of tropical Queensland occurred between the Late Pleistocene and the late Holocene. It also reinforces how poorly recorded native faunas are from the late Holocene through the historical period, to today. Such records underpin and are thus vital for modern biodiversity conservation efforts.

With rubble predicted to increase on coral reefs worldwide, we review the physical, biological, and ecological dynamics of rubble beds, with a focus on how rubble generation, mobilization, binding, and coral recruitment is expected to change on future reefs. Major disturbances, including storms and coral bleaching, are predicted to increase in intensity and frequency, and-like localized impacts including blast fishing and ship groundings-generate large quantities of coral rubble. Reefs will have increasingly smaller recovery windows between successive disturbances, leading to persistence of unstable rubble beds on reefs. With more severe storms and increased bioerosion on future reefs, rubble mobilization thresholds will be met more often as smaller, less complex rubble pieces are generated. If rubble remains stable for adequate time, it can be bound by organisms including sponges and coralline algae, and eventually be cemented. However, increasing rubble mobilization frequencies will reduce the time available for binding, while changing ocean chemistry could reduce the efficacy of calcifying binders. Ultimately, increased rubble cover will negatively impact coral recruitment into rubble beds. Rubble mobilization abrades and smothers corals, and rubble beds typically experience altered environmental and ecological conditions to the coral frameworks that precede them. Several knowledge gaps exist in relation to improved rubble mobilization thresholds, binding rates and strengths, and coral survival in varying rubble bed types and hydrodynamic regimes. Addressing these knowledge gaps will improve our ability to predict the recovery trajectory of rubble beds and assess the need for stabilization interventions.

The Australian hopping-mouse Notomys includes 10 species, eight of which are considered extinct, vulnerable, near-threatened or endangered. Here we report a new fossil species from the Broken River Region, northeastern Queensland. Notomys magnus sp. nov. is represented by craniodental material from late Quaternary cave deposits. It was a relatively large-bodied species of Notomys with a mass estimated to be ca 83 g. Notomys magnus sp. nov. is immediately distinguishable from the spinifex hopping-mouse (Notomys alexis), the northern hopping-mouse (Notomys aquilo), the fawn hopping-mouse (Notomys cervinus), the dusky hopping-mouse (Notomys fuscus), Mitchell's hopping-mouse (Notomys mitchellii) and the big-eared hopping-mouse (Notomys macrotis) by its larger size (especially its longer upper molar crown length). Notomys magnus sp. nov. differs from the large-bodied Darling Downs hopping-mouse (Notomys mordax), long-tailed hopping-mouse (Notomys longicaudatus), short-tailed hopping-mouse (Notomys amplus) and broad-cheeked hopping-mouse (Notomys robustus) by possessing a unique first upper molar (M1) morphology including relatively well-developed buccal cusps, cusp T1 prominently isolated from T4, a relatively narrow posterior loph and an incipient anterior accessory cusp. Fossils of N. magnus sp. nov. are found in association with remains of several arid-adapted taxa, including the plains mouse (Pseudomys australis), the northern pig-footed bandicoot (Chaeropus yirratji), and N. longicaudatus, possibly indicating that N. magnus sp. nov. was also arid-adapted. Dating of fossil deposits containing N. magnus sp. nov. demonstrates that it was extant in the mid-Holocene (ca 8.5 ka) so it may have been still extant at the time of European colonization but suffered extinction soon after, mirroring the fate of similarly arid-adapted contemporaneous taxa (Chaeropus yirratji and N. longicaudatus). Historical extinctions in Notomys are biased towards larger species (N. amplus, N. longicaudatus and N. robustus), and the discovery of N. magnus sp. nov. adds further to that list. Given the already high number of extinct and endangered species within Notomys, the discovery of another member that suffered geologically recent extinction has conservation implications for modern critical weight range mammals (including other species of rodents) that are particularly susceptible to extinction. Most historical extinctions of critical weight range mammals were in southern and central Australia, but the discovery of N. magnus sp. nov. suggests that species in the tropical north also were detrimentally affected.

The Great Barrier Reef is generally considered a passive tectonic setting, however the effect of antecedent topography and local geological structures on Holocene reef development is poorly understood. Offshore reefs along the central shelf were recently hypothesized to have grown continuously through a possible small Holocene sea level fall, in response to greater local subsidence, in contrast to reefs immediately to the north and south, which experienced synchronous turnoff phases. We tested this hypothesis by isolating four map zones along the GBR shelf and using: (1) a geomorphic reef type classification applying perceived evolutionary "age" as juvenile, mature, and senile domains based on geomorphology; (2) analysis of bathymetry data to understand the role of antecedent topography on the spatial distribution of reef type domains and general sea floor depths; and (3) the distribution of earthquake epicentres as an indication of possible active geological structures (i.e., faults). The results reveal that juvenile reefs (42.25 %) are more abundant in the central shelf, whereas mature-2 (40 %) and senile (31 %) reefs are more abundant in the northern zone. In the south-central zone, mature-2 reefs are prevalent, while the southern zone includes a mixture of juvenile and mature to senile domains with a sharp internal boundary. These results support the hypothesis that the central zone may have experienced greater active subsidence during the Holocene. Bathymetric data support greater regional subsidence in both central and south-central zones, but reefs are less abundant and cover a lesser percentage area of their antecedent platforms in the central zone, consistent with greater subsidence there. The boundaries between the central zone and adjacent zones are the sites of clusters of recent earthquakes, consistent with the occurrence of active geological faults bounding the zone of greater Holocene subsidence. Combined, our data support the occurrence of a tectonically defined region of active greater subsidence in the central GBR shelf that has affected the geomorphology and growth history of reefs through the Holocene. Knowledge of such spatial partitioning of reef behaviour may allow reef managers to better suite their efforts to local conditions, especially in regard to predicted sea level rise, while highlighting potential seismic risks over longer time frames.

Understanding of global sea-level changes and coral reef development is poorly constrained during Marine Isotope Stage 3 (MIS 3; ~ 60 to 30 ka). Australia’s North West Shelf (NWS), at depths of ~ 50 to 120 m below present sea-level (mbsl), represents an ideal natural laboratory to address these knowledge gaps. In this study, the authors investigate a unique suite of sea-bed rock drill (PROD) cores recovered as part of a geotechnical survey from the NWS ~ 150 km south-east of Ashmore Reef. Twenty cores, penetrating to 28 m below sea floor, were collected from the top of the now drowned platform complex in similar water depths (74.8 to 81.6 mbsl), forming two transects ~ 17 km apart. High-resolution 3D seismic and multibeam bathymetry data reveal three distinct, multigenerational platforms that are rimmed by smaller reef terraces and bisected by deeper channels, placing the core transects into a robust, regional geomorphic context that includes a succession of linear palaeo-shorelines and tidal-estuarine channel systems on the adjacent shelf between ~ 90 to 110 mbsl. The authors have completed detailed logging, high-spatial resolution hyperspectral scanning, petrologic, mineralogic and sedimentary facies analysis of these cores, including a precise palaeoenvironmental reconstruction based on coral, algal and larger benthic foraminifera assemblages; and extensive radiometric dating. The authors have observed a complex suite of lithologies including in situ coralgal reef frameworks, well-lithified to friable grainstones, packstones and coralline algal floatstone facies separated by at least two major palaeosol horizons. Together with thirty 14C-AMS and closed-system U/Th ages spanning 10.7 to > 50 ka, the authors define a complex but consistent record of four distinct chrono-stratigraphic units (Units 1 to 4), representing a repeated succession of shallow reef to deep reef-slope depositional settings as the platforms experienced repeated sea-level oscillations (interstadial/stadial to glacial/deglacial) over the last 75,000 yr. Two distinct phases of shallow-water, high-energy reef development are defined. The age of the older, diagenetically distinct reef unit (Unit 3) is unknown but interpreted to have developed before the MIS 4 lowstand (~ 65 ka). However, firm chronological constraints on the MIS 3 development of the younger reef unit (Unit 2), place the position of relative sea-level (RSL) between ~ 63 to 75 + 1.8 mbsl by 45.95 to 39.23 + 0.2 ka, consistent with other predictions and observations for the region. Following its exposure and demise due to sea-level fall to the Last Glacial Maximum (LGM), the platform system was unable to re-establish fully as it was reflooded during the subsequent deglacial sea-level rise. Deeper reef slope (Unit 1) facies dominate the core tops between ~ 13.2 to 10.7 ka, representing a major hiatus in shallow-water reef development on the platforms. Deglacial sea-level rise was either too fast and/or other environmental conditions inadequate (i.e. massive riverine sediment flux due to the strengthening Australian summer monsoon and/or reworking of shelf sediments) to allow re-establishment of shallow-water coral reef development on the platforms apart from a few isolated and distal locations (i.e. Ashmore, Cartier, Adele and Scott Reefs).

Anthropocene climate change and water quality degradation represent unprecedented challenges to modern coral reefs. Although declining reef health after European colonization is well documented around the world and increased terrigenous sediment flux is known to have terminated deglacial reefs in the Great Barrier Reef (GBR), longer-term patterns of water quality are poorly understood. Here we present the first direct proxy-based Holocene water quality reconstruction for any reef. The unique geochronological framework provided by cores from Heron and One Tree reefs (offshore, southern GBR) allowed reconstruction of offshore water quality from 8200 to 1800 years before present (BP) using centennially resolved microbialite-based geochemical proxies. Terrigenous sediment-sourced trace elements were measured in microbialites from a well dated succession of reef rock and in paleosol (ancient soil) formed at the Pleistocene-Holocene unconformity. Microbialite-hosted rare earth element and yttrium distributions (e.g., Nd/YbSN = 0.36; Y/Ho = 57) are consistent with precipitation from shallow oxygenated seawater but show a non-linear trend through the Holocene with distinct intervals of higher and lower terrigenous influence relative to average values. Immediately following reef initiation (>8300 years ago) our data suggest increasing terrigenous influence by 8000 ka. Surrounding reef seawater became less affected by terrigenous runoff from-7000 years ago, but showed marked mid-Holocene variability related to regional climatic factors. Major fluctuations between intervals of high and low relative terrigenous influence correlate well with particular regional and more global climate records. These include local relative sea level fluctuations, fluctuations in Indian-Australian Summer Monsoon (IASM) strength, and dampened El Nino Southern Oscillation (ENSO) frequency corresponding to greater terrigenous influence in the southern GBR at-7.0, 5.4, and 2.7 ka BP. Water quality then improved significantly after 3200 years BP. More broadly, it is well established that water quality has a major effect on reefs and reef communities, but for past reef history, inferences about water quality are commonly highly speculative. Reefal microbialite geochemistry provides an independent, high-quality proxy for ambient water quality that can be used to directly compare contemporaneous reef growth dynamics and ecological shifts to changing water quality. The high concentrations of trace elements in reefal microbialites, relative to other marine carbonates, provide a very robust, if time averaged, proxy for investigating ancient seawater chemistry, even in offshore reefs, such as Heron Reef. At the same time, the proxy provides a new independent data set for that may aid interpretation and model of climate change relevant to reef growth at centennial to millennial scales. As reefal microbialites are common in many global reef systems, where associated with high quality dating, they may provide useful proxies for investigating secular changes in water quality and associated climatic drivers at various temporal scales in other regions of the world.

Redox-sensitive element (RSE) compositions in marine sedimentary archives have been important in improving our understanding of redox history, especially in the Meso-Neoproterozoic ocean, where early biological innovations took place before the Cambrian Explosion. However, despite increasing availability of RSE data that represent this long time interval, temporal comparisons are difficult, and thus provide poor constraints on the dramatic changes in atmosphere-ocean chemical settings. Here we analyzed carbonate rocks and black shales from the North China and Yangtze platforms (eastern China) for trace elements and isotopic compositions (δ13C, δ34S and 87Sr/86Sr). These data were combined with previously published RSE data to allow establishment of successive elemental chemostratigraphies from sequences of both black shale and carbonate RSE archives, thus yielding direct insights into the role of marine RSE cycling. Generally low Th/RSE ratios in relatively pure carbonate rocks (Al < 0.35%, Th < 0.5 μg/g) and black shales likely indicate enriched RSEs in oxidized shallow conditions, consistent with a more oxidized Neoproterozoic ocean or confined water body. The chemostratigraphy of RSEs not only shows enrichment in Neoproterozoic marine sediments, but temporally variable trends in the Meso-Neoproterozoic. A mass balance model based on modern marine budgets demonstrates that even a small oxidation event within the dominantly anoxic setting could be an important factor for increasing dissolved RSE reservoirs, and that observed heterogeneous elemental records may represent the amplified results of a fluctuating palaeoredox (oxic-anoxic) structure with pulsed marine oxidation. Meso-Neoproterozoic marine redox heterogeneity in eastern China suggests that increases in free oxygen were potentially related to: 1) supercontinent cycles, 2) enhanced weathering inputs with high 87Sr/86Sr ratios (> 0.705 at ca. <1.4–1.1 Ga), and 3) previously reported biological processes as emphasized by biological C-S cycles. Thus, pulsed oxic conditions may have provided sequential opportunities for biological innovation.

Measuring the amount of carbon captured in deep-sea limestones is fundamental to understanding the long-term carbon cycle because pelagic limestones represent Earth’s largest carbon sink since the mid-Mesozoic. However, their contribution to the long-term carbon cycle is poorly quantified. Here, we use X-ray fluorescence and scanning X-ray diffraction microscopy for high-resolution chemical and structural analysis of pelagic limestone from the Paleocene Kaiwhata Formation in New Zealand. We identify densely packed diagenetic micro-dissolution seams that are invisible to light and electron-beam microscopes in most cases. Mass-balance calculations indicate that individual seams remove ~50% of the calcite mud matrix while their bulk-sample carbon loss adds up to ~10%. The liberated carbon is trapped in situ as calcite cement or returned to the ocean during physical compaction or soft-sediment deformation. We suggest micro-dissolution structures may play an important role in the long-term carbon cycle by modulating carbon exchange between the geosphere and hydrosphere.

Despite their broad occurrence in Australian basins, lower-level taxonomy of Australian Early Cretaceous plesiosaurs is hindered by the scarcity of skulls and other diagnostic elements. This paper presents a morphological and morphometric analysis of the vertebrae of Australian plesiosaurs and a comparison with selected non -Australian elasmosaurids (basal elasmosaurs, styxosaurines, aristonectines). Biometric analysis involved measurements that include centrum height (CH), centrum width (CW), centrum length (CL), width of zygapophyses, and others. Principal component analysis (PCA) and multivariate analysis of variance (MANOVA) were carried out on CH, CW, and CL. Morphometric ratios [Vertebral Length Index (VLI), Height Index (HI), and Breadth Index (BI)] were plotted along the length of the vertebral column and on bivariate graphs where the analysis is independent of vertebral position and correct sequencing. Direct comparison of homologous groups of vertebrae (especially anterior cervicals) easily distinguished an Australian polycotylid from all elasmosaurids in all plots. Most Australian elasmosaurid specimens plotted near basal 'Cimoliasaurus'grade elasmosaurs, where they clustered as a group relatively distinct from, but overlapping coeval non-Australian forms. However, one specimen plotted consistently with the non-Australian styxosaurines and Opallionectes andamookaensis plotted with the aristonectines. Although it is not possible to distinguish phylogenetic relationships from morphological convergence in the plotted positions, the analyses provide potential hypotheses to be tested with additional data. Hence, vertebrae have some taxonomic value for potential assignment of Australian plesiosaurs, even in the absence of skulls or other diagnostic material.

Degradation of inshore water quality associated with catchment modification is threatening global coral reef ecosystems. Coral trace element proxies are widely applied to document the magnitude and timing of historical changes in river runoff and other disturbances. However, conflicting interpretations of commonly used coral proxies (Ba/Ca, Y/Ca and Mn/Ca) complicate their application for examining historical changes in coastal water quality. The exploration of other coral trace element proxies (such as rare earth elements, REE) is limited in space and time, and to few coral genera. This study examined the dynamics of dissolved REE and yttrium (REEY) in the Fitzroy and Burdekin river tributaries and estuaries, Queensland, Australia. In addition, monthly-resolution long-term temporal records of Ba/Ca, Mn/Ca, Y/Ca and REEY proxies were investigated in two Porites and one Cyphastrea coral colonies from the central and southern Great Barrier Reef in order to test the reliability of these proxies to record the variability of river runoff and local anthropogenic disturbances. The results showed large scale removal of REEY (55–86%) in the low salinity mixing zones of both estuaries with significant fractionation of Nd-Yb and Y-Ho, confirming the ability of coral REEY to act as a terrestrial runoff proxy. Coralline Ba/Ca, Y/Ca and Mn/Ca records generally lack coherence with proximal discharge. However, temporal fluctuations of REEY proxies, irrespective of geographic location and coral genus, showed consistent behaviour relative to regional discharge with progressive increase of total REE/Ca and shale normalized Nd/Yb and decrease of Y/Ho during high-flow summer periods. The shifting baselines of REEY proxies in Cyphastrea grown in the turbid water setting of Rat Island effectively captured the timing of Gladstone Port dredging activities. Our findings suggest that shale normalized coral REEY distributions outperformed other commonly used trace element proxies and are robust indicators of changing inshore water quality. Longer-term records of coral REEY, even covering the period before European settlement from the 1850s, may provide a means to identify shifting baselines and evaluate and quantify the impacts of catchment alteration on coastal water quality and specific coral reef communities.