Evolution of the Great Barrier Reef over the last 130 ka; a multifaceted approach, integrating palaeo ecological, palaeo environmental and chronological data from cores.

Over the last few decades there has been a significant decline in the health and diversity of modern reefs globally. High resolution millennial scale records of coral reef response to environmental per- turbations are needed to determine if this decline is the result of recent anthropogenic activity, or represents part of a natural longer-term geological cycle. Hence, a range of multi-proxy palaeode- positional indicators (coralgal assemblages, sedimentary facies and associated biota) were integrated with chronologic data, to provide a greater understanding of the geologic and ecologic factors which controlled reef development during the Holocene and Last Interglacial (LIG). This constitutes the most comprehensive regional chronologic and ecologic investigation of mid-outer platform reefs, in the Great Barrier Reef (GBR) over the past 130 ka. Fifteen pre-existing long cores (10 ka) geological timescales. Results suggest that the palaeoenvironments during the initial turn-on phases of the two interglacial intervals (Holocene and LIG) were signi - cantly di erent. However, similar composition of ultimate shallow-water coralgal assemblages and slow reef aggradation rates following stabilisation of sea level, suggest both the LIG and Holocene reefs developed in a similar way as they approached mean sea level. These results further suggest that if rapid sea level rise were to occur in the future, similar to that at the onset of the LIG and in combination with other environmental stresses (e.g. warmer SST, increased turbidity, ocean acidi - cation, increased bleaching, excess nutrient runo ), the GBR may experience a near drowning event analogous to that experienced during the LIG

New Insights from Seafloor Mapping of a Hawaiian Marine Monument

On 15 June 2006, when U.S. President George W. Bush signed the proclamation creating the Papahānaumokuākea Marine National Monument (PMNM), he probably wasn’t thinking about underwater morphology. To fully understand the coral reefs and marine ecosystems that the monument was created to protect, however, scientists need to have a detailed picture of the seafloor features, home to corals and other species, as well as the geologic history of the area. Thanks to a recent, multi-institution expedition, such a seafloor features that will not only inform conservation efforts but also enable geologists and geophysicists to revise their understanding of Hawaii’s complex geologic past. Specifically, data should help scientists answer fundamental questions about the area’s regional geology. For instance, which seamounts were truly formed because of Hawaiian hotspot volcanism, and which seamounts were not

Lavoro totale

Le componenti culturali, creative e relazionali investono in modo crescente gli ambiti dell’innovazione sociale e dell’auto-imprenditorialità e come tali vengono ampiamente studiate, ma è solo spostando l’attenzione dalle varietà del lavoro cognitivo alle forze che lo determinano che possiamo tentare di cogliere e interpretare la dinamica del cambiamento in atto. Apprendimento continuo, autonomia, responsabilità, flessibilità, individualizzazione, svalorizzazione e cooperazione diventano così traiettorie di sviluppo del lavoro e non contingenze di alcuni settori o fenomeni. Analizzare le strutture che fondano l’attuale condizione del lavoro cognitivo nei campi dell’innovazione sociale e dell’auto-imprenditorialità può allora aiutarci a comprendere le forze sottostanti ai processi di riorganizzazione del lavoro in atto. L’urgenza e l’originalità di questo libro di Maurizio Busacca consistono nell’analisi di queste strutture, cercando di rintracciare ed evidenziare contraddizioni e distorsioni prima di accettare acriticamente e astoricamente le retoriche più diffuse e dirompenti, e indagando la struttura di fondo del lavoro cognitivo, nella sua dinamica storica e esistenziale, attraverso il concetto di Lavorototale-Improduttivitàmalata. Il lavoro totale si profila come una delle forme di vita economica e sociale, ma anche di patologia individuale, che già contraddistingue nel presente il lavoro cognitivo e minaccia di estendersi a settori sempre più ampi nell’immediato futuro. L’improduttività malata è il suo risvolto, o il fratello gemello. Questo libro di Maurizio Busacca ne indaga i meccanismi, anche alla luce del magistero di Franco Basaglia, e mentre ne denuncia i pericoli cerca di individuare possibili alternative o vie d’uscita

Geochemistry-based coral palaeoclimate studies and the potential of 'non-traditional' (non-massive Porites) corals: Recent developments and future progression

Understanding the natural variability of the Earth's climate system and accurately identifying potential anthropogenic influences requires long term, geographically distributed records of key climate indicators, such as temperature and precipitation that extend prior to the last 400. years of the Holocene. Reef corals provide an excellent source of high resolution climate records, and importantly represent the tropical marine environment where palaeoclimate data are urgently required. Recent decades have seen significant improvement in our understanding of coral biomineralisation, the associated uptake of geochemical proxies and methods of identifying and understanding the effects of both early and late, post depositional diagenetic alteration. These processes all have significant implications for interpreting geochemical proxies relevant to palaeoclimatic reconstructions. This paper reviews the current 'state of the art' in terms of coral based palaeoclimate reconstructions and highlights a key remaining problem. The majority of coral based palaeoclimate research has been derived from massive colonies of Porites. However, massive Porites are not globally abundant and may not provide material of a particular age of interest in those regions where they are present. Therefore, there is great potential for alternate coral genera to act as complimentary climate archives. While it remains critical to consider five key factors - vital effects, differential growth morphologies, geochemical heterogeneity in the skeletal ultrastructure, transfer equation selection and diagenetic screening of skeletal material - in order to allow the highest level of accuracy in coral palaeoclimate reconstructions, it is also important to develop alternate taxa for palaeoclimate studies in regions where Porites colonies are absent or rare. Currently as many as nine genera other than Porites have proven at least limited utility in palaeothermometry, most of which are found in the Atlantic/Caribbean region where massive Porites do not exist. Even branching taxa such as Acropora have significant potential to preserve environmental archives. Increasing this capability will greatly expand the number of potential geochemical archives available for longer term temporal records of palaeoclimate

Successive phases of Holocene reef flat development: Evidence from the mid- to outer Great Barrier Reef

A re-examination of 46 recently published U/Th reef flat ages from Heron and One Tree reefs in the southern Great Barrier Reef (GBR) identified several distinct Holocene reef growth phases with a clear 2.3-kyr hiatus in lateral reef accretion from 3.9 ka to 1.5 ka. An analysis of all available published radiocarbon reef flat ages (165) from 27 other mid-outer platform reefs revealed a similar hiatus between 3.6 ka and 1.6 ka for the northern, south-central and southern GBR. However, no hiatus in reef flat growth was observed in reefs from the central GBR with ages ranging from 7.6 ka to 0.9 ka. Increased upwelling, turbidity and cyclone activity in response to increased sea-surface temperature (SST's), precipitation and El-Nino Southern Oscillation variability have been ruled out as possible mechanisms of reef turn-off for the mid-outer platform reefs. Rather, a fall (~ 0.5 m) in relative sea level at 4–3.5 ka is the most likely explanation for why reefs in the northern and southern regions turned off during this time. Greater hydro-isostatic adjustment of the central GBR and long term subsidence of the Halifax-Basin may have provided greater vertical accommodation for the mid-outer reefs of the central GBR, thus allowing these reefs to continue to accrete vertically despite a fall in sea level ~ 4–3.5 ka. Further evidence for greater subsidence in this region includes the lack of senile reefs and dominance of incipient and juvenile reefs in the central GBR. This suggests that these reefs approached sea level considerably later than the northern and southern reefs, consistent with their deeper antecedent substrates. Thus, these results not only provide important information about possible reef flat demise in response to natural environmental factors, but also provide insights into regional subsidence that affected relative sea level along the east Australian margin during the Holocene

The evolution of the Great Barrier Reef during the Last Interglacial Period

Reef response to Last Interglacial (LIG) sea level and palaeoenvironmental change has been well documented at a limited number of far-field sites remote from former ice sheets. However, the age and development of LIG reefs in the Great Barrier Reef (GBR) remain poorly understood due to their location beneath modern living reefs. Here we report thirty-nine new mass spectrometry U-Th ages from seven LIG platform reefs across the northern, central and southern GBR. Two distinct geochemical populations of corals were observed, displaying activity ratios consistent with either closed or open system evolution. Our closed-system ages (~ 129–126 ka) provide the first reliable LIG ages for the entire GBR. Combined with our open-system model ages, we are able to constrain the interval of significant LIG reef growth in the southern GBR to between ~ 129–121 ka. Using age-elevation data in conjunction with newly defined coralgal assemblages and sedimentary facies analysis we have defined three distinct phases of LIG reef development in response to major sea level and oceanographic changes. These phases include: Phase 1 (> 129 ka), a shallow-water coralgal colonisation phase following initial flooding of the older, likely Marine Isotope Stage 7 (MIS7) antecedent platform; Phase 2 (~ 129 ka), a near drowning event in response to rapid sea level rise and greater nutrient-rich upwelling and; Phase 3 (~ 128–121 ka), establishment of significant reef framework through catch-up reef growth, initially characterised by deeper, more turbid coralgal assemblages (Phase 3a) that transition to shallow-water assemblages following sea level stabilisation (Phase 3b). Coralgal assemblage analysis indicates that the palaeoenvironments during initial reef growth phases (1 and 2) of the LIG were significantly different than the initial reef growth phases in the Holocene. However, the similar composition of ultimate shallow-water coralgal assemblages and slow reef accretion rates following stabilisation of sea level (phase 3b) suggest that reefs of both ages developed in a similar way during the main phase of relatively stable sea level

TOUGH2-Seed: a coupled fluid flow and mechanical-Stochastic approach to model injection-induced seismicity

Understanding the injection-induced triggering mechanism is a fundamental step towards controlling the seismicity generated by deep underground exploitation. Here we propose a modeling approach based on coupling the TOUGH2 simulator with a geomechanical-stochastic model. The hydro-mechanical-stochastic model provides a good representation of different mechanisms influencing each other during and after the injection phase. Each mechanism affects the induced seismicity in a different way and at different times during the reservoir stimulation, confirming that a complex interaction is in place, and that more sophisticated and physics-based approaches coupled with statistical model are required to explain such a complex interaction. In addition to previous statistical and hybrid models, our approach accounts for a full 3D formulation of both stresses and fluid flow, further including all the TOUGH2 capabilities. Furthermore, it includes interactions between triggered seismic events through calculation of static stress transfer. In this work, we present the main capabilities of TOUGH2-SEED and apply the model to the Basel EGS case, successfully reproducing the injection pressure as well as the evolution of the seismicity

High-resolution hyperspectral imaging of diagenesis and clays in fossil coral reef material: a nondestructive tool for improving environmental and climate reconstructions

Hyperspectral imagery (1000–2500 nm) was used to quantitatively map carbonate and clay minerals in fossil reef cores that are relevant to accurately reconstructing past environmental and climatic conditions. Techniques were developed using hyperspectral imagery of fossil reef corals and cores acquired from three different geological settings, and were validated against independent measures of calcite to aragonite ratios. Aragonite, calcite, and dolomite were distinguished using a combination of the wavelength position and asymmetry of the primary carbonate absorption between 2300 and 2350 nm. Areas of core containing small amounts of calcite (>2–5%) were distinguished from aragonite in imagery of two cores, enabling quantitative maps of these minerals to be constructed. Dolomite was found to be the dominant mineral in another core. Trace amounts of the aluminium-rich clay mineral kaolinite were detected, quantified, and mapped in one core using its diagnostic absorption feature near 2200 nm. The amounts of clay detected from hyperspectral imagery were below the limits of detection by standard X-ray diffraction techniques but its presence was confirmed by Fourier Transform Infrared Spectroscopy. Hyperspectral imagery acquired at high spatial resolution simplifies vetting procedures for secondary carbonate minerals in coral reef cores, significantly reduces sampling time and costs, and is a powerful nondestructive tool to identify well-preserved coral aragonite in cores for uses in paleoclimate, paleoenvironment and paleoecosystem reconstruction

Holocene reef growth over irregular Pleistocene karst confirms major influence of hydrodynamic factors on Holocene reef development

Many factors govern reef growth through time, but their relative contributions are commonly poorly known. A prime example is the degree to which modern reef morphology is controlled by contemporary hydrodynamic settings or antecedent topography. Fortunately, reefs record essential information for interpreting palaeoclimate and palaeoenvironment within their structure as they accrete in response to environmental change. Five new cores recovered from the margin of Heron Reef, southern Great Barrier Reef (GBR), provide new insights into Holocene reef development and relationships between Holocene reefs and Pleistocene antecedent topography, suggesting much more irregular underlying topography than expected based on the configuration of the overlying modern reef margin. Cores were recovered to depths of 30 m and 94 new Th ages document growth between 8408 ± 24 and 2222 ± 16 yrs. BP. One core penetrated Pleistocene basement at ∼15.3 m with Holocene reef growth initiated by ∼8.4 ka BP. However, 1.83 km west along the same smooth margin, four cores failed to penetrate Pleistocene basement at depths between 20 and 30 m, suggesting that the margin at this location overlies a karst valley, or alternatively, the antecedent platform does not extend there. A 48 m-long margin-perpendicular transect of three cores documents the filling of this topographic low, at least 30 m beneath the current reef top, with seaward lateral accretion at a rate of 34.3 m/ka. Cores indicate steady vertical and lateral accretion between 3.2 and 1.8 ka BP with no evidence of the hiatus in reef flat progradation seen in most other offshore reefs of the GBR at that time. These cores suggest that the relative protection afforded by the valley allowed for unconsolidated sediment to accumulate, enabling continuous progradation even when other areas of the reef flat appear to have ‘turned off’. Additionally, the cores suggest that although reefs in the southern GBR clearly owe their location to Pleistocene antecedent topography, modern reef morphology at sea level primarily reflects the interaction of Holocene reef communities with contemporary hydrodynamics