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The Murray Darling Basin contains 40% of Australia's farms and is subject to multi-year droughts that put severe pressure on southeast Australia's freshwater resources. Yet the long-term frequency, timing and potential severity of these droughts is unknown, as there are few high-resolution paleoclimate records from the basin that extend past the instrumental era. In this study, we investigate the potential of stalagmites from Careys Cave, Wee Jasper, in the Murray-Darling Basin to record past droughts. We use a multiproxy approach of stalagmite stable isotopes, trace element data, and climate reanalysis. We show that (a) stalagmite δ18O at this site likely records either local or regional precipitation amount and (b) stalagmite δ18O shows reasonable coherence with decadal-scale wet and dry changes in regional rainfall over the last 150 years, including the Federation Drought (1895–1902). Therefore, stalagmites from Wee Jasper can be used to draw regional inferences about past rainfall and have potential to extend the record of past droughts in the Murray Darling Basin beyond the limits of historical data. Extracting such a record will enable a better understanding of the causes of multi-year droughts in the region and consequently better planning, mitigation, and resilience in the basin. [ABSTRACT FROM AUTHOR]

Reconstructing coral reef histories provides a window of understanding into reef response to changing environmental and climatic conditions over various temporal scales. Here we present the results of 117 U‐Th dates from emergent reef flat and slope cores and surface death assemblages, combined with previously published fossil microatoll data, to capture the entire sequence of reef growth at Mazie Bay, inshore Southern Great Barrier Reef (GBR). Coral U‐Th dates indicate that Mazie Bay reef initiated ~6,900 years before present (yr. BP) quickly filling accommodation space. While rates of vertical reef accretion (5.3 ± 1.0 mm year−1) were comparable to the GBR average during the mid‐Holocene (~5.0 mm year−1), reef flat progradation occurred at a rate 1.5‐ to 6‐fold previous GBR rates until 5,100 yr. BP (~70.4 cm year−1). Average progradation slowed to ~7.1 cm year−1 in the subsequent ~4,000 years and reef slope cores indicate this reef had largely "turned‐off" by 400 yr. BP, with modern coral communities existing as a veneer over the largely senescent framework. Death assemblage dates highlight coral disturbance and recovery regimes in response to increased cyclone activity 1960–1985 AD and recent extreme sea surface temperature and flood events post 2000 AD. U‐Th dating of mid‐Holocene to modern coral deposits from Mazie Bay reef provides a unique insight into past reef development, response to recent disturbance regimes, and potential for future reef growth. In the case of Mazie Bay, our data suggest limited accommodation space and increased occurrence of sea surface temperature extremes will restrict future reef growth at this site. Key Points: The 117 coral U‐Th dates from Mazie Bay reef provide an insight into reef dynamics at multiple temporal scalesMazie Bay reef initiated ~6,900 yr. BP and rapidly filled optimum available accommodation space, with reef growth slowing by 4,200 yr. BPU‐Th dating of death assemblages revealed quasi‐periodic cycles of disturbance and recovery over the past 60 years [ABSTRACT FROM AUTHOR]

U‐Th dating of carbonate veins in connection with active tectonics has recently been used as an attractive tool for constraining the absolute timing of late Quaternary crustal deformations. In this study, for the first time we correlate U‐Th ages of travertine deposits in coseismic fissures along the North Anatolian Fault Zone with records of paleoseismological studies supported by historical earthquake catalogued data. U‐Th ages are assessed in relation to the recurrence interval and the size and epicenter distance of major Holocene earthquakes. Our statistical evaluations on age correlations indicate that the carbonate vein precipitation is concentrated in eight different periods along the North Anatolian Fault Zone. The periods are well correlated with historical earthquake records and with previous dating results of the nearby trench studies. At least six of the periods correspond to the earthquakes reported in the historical catalogues. The age correlations of carbonate precipitation intervals for the last millennium show a recurrence along the eastern North Anatolian Fault Zone with a mode at 130–330 years that is consistent with a previously proposed paleoseismic recurrence interval of the fault. Recorded events in carbonate veins indicate a close‐epicenter (d < 200 km) and high‐intensity (I > VI) paleoearthquakes. Our results suggest that coseismic carbonate veins could be used to determine paleoseismic records as a supplementary tool to augment paleoseismological techniques. This tool has advantages over traditional paleoseismological methods for the understanding of long‐term earthquake behavior, particularly for prehistoric late Pleistocene events which cannot be dated easily by traditional paleoseismological methods. Key Points: Age distributions of coseismic carbonate veins are comparable with historical earthquakesCoseismic carbonates are precipitated with the close‐epicenter (d < 200 km) and high‐intensity (I > VI) earthquakesCoseismic carbonates are a good candidate to determine the long‐term seismic release records [ABSTRACT FROM AUTHOR]

High-resolution U-Th and 14C dating of two calcite flowstones (RTf: Last Interglacial; RTy: Late Holocene) from the Re Tiberio – Monte Tondo karst system (North Italy) is presented to investigate the palaeoclimate potential of speleothems from gypsum caves. To date, there is a lack of information regarding the dating potential of calcite speleothems that have grown in such gypsum karst environment (e.g. no pseudokarst). High-resolution U-Th dating, aimed at establishing if these speleothems can provide robust radiometric age sequences, is first presented. Although both samples show promise for reliable radiometric dating, about 20% of the ages in the RTf dataset were excluded from the age-model as outliers. These outliers are best explained by post-depositional diagenetic processes affecting the U-Th system rather than anything specific to gypsum karst environment conditions. In contrast, outliers were not detected in the RTy sample, but U-Th analysis was not able to constrain its relatively young age (∼600 years before present, B.P.). Consequently, radiocarbon measurements were undertaken, and combined with the U-Th ages to build an age-model. The latter allowed the estimation of "dead carbon fraction" (DCF), which yields a constant value through time, and a magnitude comparable to other sites where climate is similar to Monte Tondo. Soils were considered the main source of carbon, because bedrock dissolution acted predominantly under open-system conditions, and soil organic matter (SOM) turnover rate appears above average compared to sites studied elsewhere. [ABSTRACT FROM AUTHOR]

Prograded coral rubble ridges have been widely used as archives for reconstructing long-term storm or storminess history. Chronologies of ridge systems in previous studies are often based on a limited number of low-resolution radiocarbon or optically-stimulated luminescence (OSL) ages per ridge (usually only one age per ridge), which carry intrinsic age uncertainties and make interpretation of storm histories problematic. To test the fidelity of storm ridges as palaeo-storm archives, we used high-precision U-Th dating to examine whether different samples from a single ridge are temporally constrained. We surveyed three transects of ridge systems from two continental islands (Normanby Island and High Island) within the Frankland Islands, Great Barrier Reef (GBR), and obtained 96 U-Th dates from coral rubble samples collected from within and between different ridges. Our results revealed significant differences in age ranges between the two islands. The steeper and more defined rubble ridges present on Normanby Island revealed that the majority of U-Th ages (over 60%) from a single ridge clustered within a narrow age range (∼100 years). By contrast, the lower and less defined ridges on High Island, which were more likely formed during both storm and non-storm high-energy events, revealed significant scatter in age distribution (>>200 years) with no notable clustering. The narrower age ranges obtained from the steeper and more defined rubble ridges suggest that previous approaches of using either limited samples from a single ridge or low-precision dating methods to establish chronologies are generally valid at centennial to millennial timescales, although caution must be taken to use such approaches for storm history reconstruction on shorter timescales (e.g. decadal). The correlation between U-Th mortality ages of coral rubble and historical stormy periods highlights the possibility of using coral rubble age distribution from rubble ridges to reconstruct the long-term regional storminess history. U-Th age distribution of all dated coral rubble samples, combined with previously published storm-transported coral block data from the same region, revealed at least six relatively stormy periods in the past 500 years in the Frankland Islands region: 1570–1590, 1760–1780, 1800–1830, 1860–1880, 1940–1960, 1980–2010 CE. Wavelet power analysis of the relative probability of U-Th age distribution indicates that the Pacific Decadal Oscillation (PDO) and El Nino-Southern Oscillation (ENSO) may be partially responsible for the long-term variability in storminess. [ABSTRACT FROM AUTHOR]

High-energy storm-transported coral blocks are widespread on the reef flats of the Great Barrier Reef (GBR), Australia, and have the potential to be used as proxies for reconstructing past storm/cyclone events prior to historical or instrumental records. In this study, samples from 42 individual transported coral blocks were collected from the inshore Frankland Islands, northern GBR for high-precision MC-ICPMS U–Th dating with their surface mortality ages recording the timing of individual storms or cyclones responsible for their uplift from their original growth position. The dated mortality ages were found to match well with known historical storm/cyclone events in the last century, with 80% of them falling within episodes of increased storm activity (1910–1915, 1945–1950, 1955–1960, 1975–1990, 1995–2000 AD) captured by instrumental/historic records, confirming that transported coral blocks on inshore reefs can be used as proxies for past storm/cyclone occurrences. Using this approach, this study also identified 17 additional storm/cyclone events that occurred before European settlement in the 1850s, including three oldest events at 758.4 ± 3.7, 777.9 ± 4.9, and 985.2 ± 4.8 AD, respectively. Our results, despite still preliminary, suggest that the storm/cyclone activity in this region tends to broadly correlate with the positive modes of the Pacific Decadal Oscillation (PDO) during the last millennium. In addition, there appears to be a decreasing age trend from the shore to the reef edge (from 758.4 ± 3.7 AD to 1988.3 ± 1.6 AD), which can be attributed to sea-level fall and/or reef/island progradation over the last 2000 years. [ABSTRACT FROM AUTHOR]

It is increasingly apparent that sea-level data (e.g. microfossil transfer functions, dated coral microatolls and direct observations from satellite and tidal gauges) vary temporally and spatially at regional to local scales, thus limiting our ability to model future sea-level rise for many regions. Understanding sea-level response at ‘far-field’ locations at regional scales is fundamental for formulating more relevant sea-level rise susceptibility models within these regions under future global change projections. Fossil corals and reefs in particular are valuable tools for reconstructing past sea levels and possible environmental phase shifts beyond the temporal constraints of instrumental records. This study used abundant surface geochronological data based on in situ subfossil corals and precise elevation surveys to determine previous sea level in Moreton Bay, eastern Australia, a far-field site. A total of 64 U-Th dates show that relative sea level was at least 1.1 m above modern lowest astronomical tide (LAT) from at least ~6600 cal. yr BP. Furthermore, a rapid synchronous demise in coral reef growth occurred in Moreton Bay ~5800 cal. yr BP, coinciding with reported reef hiatus periods in other areas around the Indo-Pacific region. Evaluating past reef growth patterns and phases allows for a better interpretation of anthropogenic forcing versus natural environmental/climatic cycles that effect reef formation and demise at all scales and may allow better prediction of reef response to future global change. [ABSTRACT FROM AUTHOR]

Abstract: A new middle Pleistocene vertebrate fossil record from eastern Australia, dated by U disequilibrium series, records the first Quaternary record of an Australian tropical rainforest fauna. This exceptionally rich fauna underwent extinction after a long period of relative faunal stability, spanning several glacial cycles, and persisted probably until 280000 years ago. Some time between 280000 and 205000 years ago the rainforest fauna was replaced by a xeric-adapted fauna. Since that time, the xeric-adapted fauna was replaced by a mesic-adapted fauna which was established by the Holocene. This is the first vertebrate faunal evidence in Australia of the middle Pleistocene Mid-Brunhes Climatic Event (MBE), a major climatic reorganisation that led to increased aridity in northern Australia from around 300000 years ago. Several independent palaeoclimate proxies suggest that the climatic shift to aridity was due to increased climatic variability and weakened northern monsoons, which may be manifested in the extinction of the aseasonal rainforest fauna and its replacement by an arid-adapted fauna. We extend the temporal ranges of several taxa from the Pliocene into the middle Pleistocene. We also reveal a longer palaeobiogeographic connection of rainforest taxa and lineages shared between New Guinea and Australia than was previously thought and show that their extinction on mainland Australia occurred sometime after 280000 years ago. [Copyright &y& Elsevier]

We investigate the temporal variations in stable carbon and oxygen and radiogenic Sr isotope as well as rare earth element contents of Akkaya travertine deposits in the Eskipazar region, northwest Turkey. U-Th age data indicate that studied travertines in the periphery of the 1944-earthquake rupture of the North Anatolian Fault Zone formed in a time span of 93 to 1.8 ka BP. The younger group is represented by fissure-filling carbonates whereas the older sequence is composed of veins with varying crystallization ages that are injected to bedded travertines. The age data on vein injections and fissure-ridge travertines in the Akkaya site indicate the seismic reactivation along the west-central part of the North Anatolian Fault Zone to be intensified at least 4 periods (1.8, 20, 47 and 88 ka BP) during the last 90 ka. δ18O and δ13C systematics of Akkaya travertines, which are precipitated by CO 2 –rich fluids depressurized during episodic seismic unrest, are in the range from −15.86 to −7.67‰ (VPDB) and 4.66–8.68‰ (VPDB), respectively. δ18O of the fluid equilibrating with the studied travertines is estimated in the range of −11.2 to −10.2‰ which is quite consistent with the average value (−12.3‰) reported for the Akkaya thermal spring. Stable isotope values of travertines indicate modification by rapid CO 2 degassing associated with seismic events. Helium isotope compositions of gas phase and dissolved gas of thermal fluids in the area refer to mantle contribution up to 12 %. Sr isotope values of Akkaya travertines are probably originated from Upper Cretaceous marine limestones or mafic basement rocks. REY contents are about 3 orders of magnitude lower than those of basement lithologies. [ABSTRACT FROM AUTHOR]

Coral reefs globally are impacted by natural and anthropogenic stressors that are compounded by climate change. Understanding past reef responses to natural stressors (cyclones, sea-level change, freshwater inputs, and sedimentation) can provide important insights to further understand recent (within the past century) trends in coral cover and diversity. Here we use a compilation of recently published data to investigate the Holocene development of five fringing reefs that are located on a cross-shelf transect on the central Great Barrier Reef, and that are exposed to varying degrees of natural and anthropogenic sedimentation, storm exposure, and Holocene sea-level change. Forty-two reef cores collected using a combination of manual percussion coring and hydraulic drilling techniques, were analysed and dated using uranium-thorium methods. The chronostratigraphic records of reef development established using 105 recently published radiometric ages and seven new uranium-thorium ages from the reef cores and fossil microatolls preserved across the reef flats were compared to investigate cross-shelf variations in reef development. This is the first study to conduct an internal investigation of reef framework across an inshore–offshore gradient to examine the varying levels of influence of sedimentation, sea level and cyclones. Our observations from the central Great Barrier Reef show that reefs furthest offshore from the mainland coast were typically initiated earliest after the post-glacial marine transgression. Reef flat size, morphology, and growth style varied according to constraints placed on reef development by the composition, depth, shape, and relief of the underlying substrate. We establish that terrigenous sedimentation had a marked effect on the development of inshore reefs closest to the mainland (within 10 km of the mainland coast). Periods of relatively high terrigenous sedimentation correspond with enhanced reef accretion rates, and also resulted in a superior record of palaeo-ecological coral composition (i.e., better preservation) at inshore sites. In contrast, mid-Holocene cyclones played a seemingly more important role in the development of reefs >10 km from the mainland; although cyclones clearly affect reefs closer inshore, their geomorphology is affected by a range of controlling factors. Insights provided by these five Holocene reef chronostratigraphies provide useful baseline understanding of reef condition and growth along a cross-shelf transect where the reefs are exposed to variable stressors. [ABSTRACT FROM AUTHOR]

Accurate radiocarbon dating of marine samples requires knowledge of the marine radiocarbon reservoir effect. This effect for a particular site/region is generally assumed constant through time when calibrating marine 14 C ages. However, recent studies have shown large temporal variations of several hundred to a couple of thousand years in this effect for a number of regions during the late Quaternary and Holocene. Here we report marine radiocarbon reservoir correction ( Δ R ) for Heron Reef and Moreton Bay in southwestern (SW) Pacific for the last 8 ka derived from 14 C analysis of 230 Th-dated corals. Most of our Δ R for the last ∼5.4 ka agree well with their modern value, but large Δ R variability of ∼410 yr (from trough to peak) with possible decadal/centennial fluctuations is evident for the period ∼5.4–8 ka. The latter time interval also has significant variations with similar features in previously published Δ R values for other sites in the Pacific, including southern Peru–northern Chile in southeastern (SE) Pacific, the South China Sea, Vanuatu and Papua New Guinea, with the largest magnitude of ∼920 yr from SE Pacific. The mechanisms for these large Δ R variations across the Pacific during the mid-Holocene are complex processes involving (1) changes in the quantity and 14 C content of upwelled waters in tropical east Pacific (TEP) (frequency and intensity of ocean upwelling in the TEP, and contribution of Subantarctic Mode Water to the upwelled waters, which is influenced by the intensity and position of southern westerly winds), and (2) variations in ocean circulation associated with climate change (La Niña/El Niño conditions, intensity of easterly trade winds, positions of the Intertropical Convergence Zone and the South Pacific Convergence Zone), which control the spreading of the older upwelled surface waters in the TEP to the western sites. Our results imply the need for employing temporal changes in Δ R values, instead of constant (modern) values, for age calibration of Holocene marine samples not only for the SW Pacific sites but also for other tropical and subtropical sites in the Pacific. [ABSTRACT FROM AUTHOR]

Highlights: [•] Aragonite stalagmites are suitable for palaeoclimate reconstruction. [•] The Holocene Climatic Optimum was synchronous, lasting from ∼10.6 to 4.2ka BP. [•] Our data do not support previously reported asynchronism between EASM and ISM. [Copyright &y& Elsevier]

In the face of changing global climate the future of corals reefs is uncertain. High latitude reefs may offer potential refugia for corals under projected increasing sea surface temperatures (SSTs). To understand the reef growth potential of modern high latitude reefs it is first necessary to understand past reef growth and response to climatic and environmental changes. The history of the Great Barrier Reef (GBR) has been shown to be punctuated by a multi-millennial Mid-Holocene reef "turn-off" or initiation hiatus in the Northern and Southern GBR (∼5500–2500 years before present [yr. BP]). Here we present the results of chronologically constrained reef matrix cores from five continental island fringing reefs and coral communities in the Keppel Islands to revaluate the timing, extent and possible drivers of the Mid-Holocene hiatus in the Southern GBR. Earliest initiation occurred at Wedge and Halfway Islands at 7773 ± 19 yr. BP and 7455 ± 20 yr. BP, respectively. Following initiation, vertical reef accretion at Halfway was comparable to previously reported rates for the GBR of ∼3.4 mm yr−1, increasing to ∼8.0 mm yr−1 between 6100 and 5500 yr. BP. Conversely, the coral community at Wedge Island, located closer to mainland terrestrial influence, accreted <1.0 mm yr−1 to 5500 yr. BP after which a 3000-year stratigraphic hiatus is observed. A negative relative sea level oscillation at 5500 yr. BP coincides with the transition of Halfway reef from vertical accretion to lateral progradation and the "turn-off" of the Wedge Island coral community. The reef at Middle Island appears to have initiated in the midst of the Mid-Holocene hiatus period at ∼3500 yr. BP, with vertical accretion at both Middle and Halfway Islands being the highest for the region's history at 12.5 ± 3.3 mm yr−1 and 15.0 ± 6.0 mm yr−1, respectively, between 3500 and 3000 yr. BP. A proposed late-Holocene relative sea level highstand of ∼1 m at ∼2000 yr. BP coincides with the first dates identified at near-shore Divided Island, and the re-initiation of coral growth at Wedge Island, although both showed limited net vertical accretion. These near-shore sites "turned-off" again between 1300 and 900 yr. BP, likely associated with a rapid relative sea level fall. Reef progradation also slowed at Halfway Island and Middle Island after 1200 yr. BP until a recent increase in reef growth at Middle Island since the late 1970's associated with modern increases in average SSTs. Our data suggests that although reef-scale "turn-off" events occurred, there is no evidence for a regional scale hiatus in coral growth or initiation comparable to that found further north on the GBR. A comparison with other Southern and south-Central GBR reef cores suggests that relative sea level oscillations in conjunction with changes to climate, appear to have driven varying, but synchronous, modifications to reefs at 5500, 4600, 2800 and 1200 yr. BP. • Limited evidence of a regional scale Holocene reef hiatus in the Keppel Islands. • Reefs display both broadly synchronous and completely disparate growth histories. • Sea level variability appears to be the primary driver of synchronous changes. • Palaeoclimate variability is associated with changes in net accretion rates. • The Keppel Islands offer potential refugia for corals under future climate challenges. [ABSTRACT FROM AUTHOR]

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 230 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. [ABSTRACT FROM AUTHOR]

Comparisons between historical and contemporary photographs of coral reef flats from the inshore Great Barrier Reef (GBR) have been cited by various authors and agencies as evidence of reef degradation since European settlement and have been presented as proof of widespread reef decline. The diminished condition is inferred from reduced live coral cover and structural diversity depicted in the contemporary photographs. Anthropogenic causes for this deterioration are most often proposed, usually because it is argued to have coincided with modifications to coastal catchments by European settlers. However, changes in reef condition inferred from photographic comparisons have rarely been verified against quantitative assessments of reef geomorphic state or current reef status. Photographs taken in the late 1800s of the reef flat at Stone Island, located in Edgecumbe Bay in the inshore central GBR, have been compared by others with more recent images to interpret significant reductions in coral cover and diversity over the past 120 or so years. We examined the internal structure of fringing reefs at two locations on Stone Island by collecting 14 percussion cores across the reef flats. Sedimentological analyses coupled with uranium-thorium dating allowed for the reconstruction of reef development over the past ~ 7000 years. Both reefs at Stone Island initiated prior to 7000 calendar years before present (yBP, where present is 1950 AD) and both reef flats were almost entirely emplaced by 4000 yBP. Surveys of the benthic ecology of reefs at Stone Island and at Middle Island, also in Edgecumbe Bay, indicate that coral cover and diversity across reef flats and slopes was patchy and varied spatially within each location and throughout the region. Live coral cover on the Middle Island reef flat reached an average (± 1σ standard deviation) of 63.1 ± 20.2%. This was much higher than the live coral cover on Stone Island reef flats, where only a few small living coral colonies were recorded. We evaluate the use of photographic records from Stone Island to depict regional changes in reef condition by comparing the trends in reef condition determined from photographic records with underlying reef geomorphic state reconstructed from reef cores. We conclude that inferred changes in reef condition at Stone Island are localised and should not be used as evidence of widespread regional decline on the GBR. [ABSTRACT FROM AUTHOR]

Late Pleistocene raised coral reef terraces form extensive outcrops up to 5 km wide along the Saudi coast. Porites coral were dated using U/Th while clastic sediment from Jeddah was dated using thermoluminescence. The pooled mean age for the coral samples is 121.5 ± 0.2 ka suggesting MIS 5e, even for the uplifted 16–20 m high terrace in the north at Haql. In Jeddah the MIS 5e back-reef succession is overlain by fluvial sediment that gave a TL age of 66 ± 13 ka. The structure and faunal composition of the coral terraces suggests that they accumulated in broad shallow embayments following the last interglacial transgression. The consistent elevation of these terraces suggests that the central and southern Saudi coast has been tectonically stable for at least the past 125,000 years and the coral reef terraces (at 3.5–5.5 m elevation) are consistent with the MIS 5e sea level high-stand that peaked at 6–9 m above present sea level. The Saudi coastal coral terrace north of Duba shows progressive uplift to 16–20 m near Haql since 108–120 ka as a result of ongoing transform faulting in the Gulf of Aqaba. [ABSTRACT FROM AUTHOR]

Previous studies have analysed the age distributions of stalagmites harvested from multiple caves and inferred important palaeoclimate changes that explain stalagmite growth phases. However, stalagmites may grow over tens of thousands of years; thus, they are irreplaceable. The value of speleothems to science must be weighed against their potential and current aesthetic and cultural value. In this study, we show that some palaeoclimate information can be extracted from a cave system without the removal of stalagmites. Our case study is based on basal U–Th dates for 77 individual stalagmites from thirteen caves located in and around Bantimurung-Bulusaraung National Park, southwest Sulawesi, Indonesia. The stalagmites grew during discrete intervals within the last ~ 530,000 years, and an analysis of their age distribution shows a first-order exponential decrease in the number of older stalagmites surviving to the present day. Further, this exponential relationship is observed in stalagmite populations around the world and is therefore likely to be a general cave phenomenon. Superimposed on the first-order exponential age distribution in southwest Sulawesi are positive anomalies in stalagmite growth frequency at 425–400, 385–370, 345–335, 330–315, 160–155, 75–70 and 10–5 ka, which are typically coincident with wet periods on Borneo. To explain this distribution, we present a simple model of stalagmite growth and attrition. A first-order trend is controlled by processes intrinsic to karst systems that govern the natural attrition of stalagmites. These processes are nearly constant over time and result in the observed exponential relationship of stalagmite basal ages. Second-order variation is controlled by changes in the rate of stalagmite generation caused by fluctuating climates, which is a well-known concept in the speleothem literature. Removal of the exponential baseline allows for better assessment of relative peak heights and basic palaeoclimate information to be inferred. Importantly, the first- and second-order growth frequency variations can be characterised using basal stalagmite ages only, without the removal of stalagmites, thereby helping reduce the impact of scientific sampling on the cave environment. [ABSTRACT FROM AUTHOR]

We report on new geoarchaeological finds in a recently discovered cave-chamber (Liang Bawah, “Cave Underneath”) positioned below Liang Bua on the island of Flores, Indonesia, where the type specimen for Homo floresiensis was recovered from Late Pleistocene sediment. At the rear of Liang Bua, a 23-m-long shaft, inclined at 60°, leads to a lower chamber measuring 23 m × 24 m × 5 m high (about half the size of Liang Bua). Stone artefacts and bones were found shallowly buried in rubble at the base of the shaft, and around a 5-m-high mud mound that fills the northwest sector of Liang Bawah. We recovered 17 stone artefacts made from chert and volcanics, and more than 220 well-preserved bone elements belonging to endemic giant rats, pigs, primates, small murid rodents, bats and introduced species. Multi-collector inductively coupled plasma mass spectrometer (MC-ICPMS) analysis of uranium and thorium in carbonate coatings on four bones yielded ages of ~ 240–180 ka (endemic giant rat femur), ~ 110–60 ka (unidentified phalanx), ~ 33–23 ka (pig skull fragment), and ~ 7–3 ka (giant rat femur), which overlap with the ~ 95 to 17 ka occupation of Liang Bua by H. floresiensis . The ~ 33–23 ka age of the pig skull fragment indicates that Sus sp. may have dispersed into island Southeast Asia earlier than previously recognised. The passageway at the rear of Liang Bawah, and a currently buried front entrance, represent two possible transport paths for cultural and faunal material to the cave-chamber. Analysis of the geomorphic evolution of Liang Bawah shows that it may have been a Late Pleistocene depocentre for material transported from the occupation chamber of Liang Bua, and a repository for human subsistence refuse, or pit-fall trap, via the rear passage. These physical attributes, and the antiquity of the faunal remains found thus far, indicate that Liang Bawah could contain an archive of the Late Pleistocene and, potentially, remains of H. floresiensis . [ABSTRACT FROM AUTHOR]

Abstract: The emplacement of calcite-filled veins perpendicular to the Dead Sea Fault Zone in northern Israel reflects strain partitioning during transpression. We present structural, geochemical, and U–Th geochronological data that constrain the mechanism, conditions and timing of vein formation. Vein walls are strongly brecciated and commonly cemented with coarsely crystalline calcite, whereas calcite-filled veins are composed of wall-parallel bands of calcite crystals. Elongated blocky and fibrous calcite crystals grew perpendicular to the vein walls and are characterised by a truncate sealing-hiatus morphology, indicating episodes of partial or complete sealing of the fractures during calcite precipitation. Stable isotope and rare-earth element and yttrium (REY) analyses indicate that calcite-filled veins precipitated by karst processes, involving meteoric water and limited fluid-rock interactions. U–Th dating results show a prolonged history of vein growth. While some veins initiated prior to 500 ka, the majority of the veins were active between 358 and 17 ka. Age constraints on vein activity correspond to an ∼E–W regional shortening phase in this sector of the Dead Sea Fault Zone, associated with an increased component of convergence during the late-Pleistocene. [Copyright &y& Elsevier]

Understanding the marine radiocarbon reservoir effect (i.e., marine radiocarbon reservoir age (R) and/or correction (ΔR)) is important for the construction of robust radiocarbon chronologies for marine archives for various research areas including archaeology, palaeoecology, paleoceanography, Quaternary research and climate change studies. In this study, we examined temporal ΔR variability for the South China Sea (SCS) and the Great Barrier Reef (GBR) during the past ∼8.1 ka based on 14C analysis of 230Th-dated corals. Results show large ΔR variations of ∼410 yr and ∼490 yr for the SCS and the northern GBR for ∼5.5–8.1 ka and ∼5.5–7 ka, respectively, and a smaller ΔR variability of ∼200 yr for the SCS for ∼2–3.5 ka. Our data, together with those previously published for the Tropical and South Pacific, indicate that variability in ocean upwelling bringing old subsurface waters to the surface and/or changes in the sources (or 14C level) of the upwelled waters are responsible for seeing large ΔR variations in coastal areas along the eastern Pacific and the Tropical East Pacific (TEP) of several hundred to a thousand years mostly during the Early to Middle Holocene. ΔR variations in the central and western Pacific of several and a couple of hundred years during the Middle and Late Holocene, respectively, might be due to variability in Pacific-wide ocean circulation associated with climatic changes controlling the spread of upwelled waters from the TEP to the west. This mechanism together with local/regional effects, such as changes in ocean upwelling in the SCS resulting from East Asian monsoon variability and changes in upwelling and/or horizontal advection in the northern GBR associated with variability in the El Niño Southern Oscillation, might be responsible for the observed ΔR variations in these areas. The results of our study also indicate the need for regional marine radiocarbon calibration curves for improved radiocarbon dating of marine samples as the observed Holocene ΔR values for the Tropical and South Pacific are not fully reproduced by a recent modelling work using a 3D ocean model, which takes into account climate change effects. Ocean circulation changes were included in the model for the period of 11.5–50 cal kyr BP but possibly not considered or not well represented for the Holocene, which might explain the differences between the observed and modelled ΔR values. • New ΔR for Western Pacific for ∼0–8 ka based on 14C analysis of 230Th-dated corals. • ΔR variability of ∼200–490 yr for Western Pacific during the last ∼8 ka. • ΔR variability of ∼300–1000 yr for coastal Eastern Pacific during the last ∼12 ka. • ΔR variations are mainly due to large scale climate and ocean circulation changes. • Urgent need for local/regional marine calibration curves for improved 14C dating. [ABSTRACT FROM AUTHOR]