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Groundwater is used extensively in the Central Kenya Rift for domestic and agricultural demands. In these active rift settings groundwater can exhibit high fluoride levels. In order to address water security and reduce human exposure to high fluoride in drinking water, knowledge of the source and geochemical processes of enrichment are required. A study was therefore carried out within the Naivasha catchment (Kenya) to understand the genesis, enrichment and seasonal variations of fluoride in the groundwater. Rocks, rain, surface and groundwater sources were sampled for hydrogeochemical and isotopic investigations, the data was statistically and geospatially analyzed. Water sources have variable fluoride concentrations between 0.02–75 mg/L. 73% exceed the health limit (1.5 mg/L) in both dry and wet seasons. F − concentrations in rivers are lower (0.2–9.2 mg/L) than groundwater (0.09 to 43.6 mg/L) while saline lake waters have the highest concentrations (0.27–75 mg/L). The higher values are confined to elevations below 2000 masl. Oxygen (δ 18 O) and hydrogen (δD) isotopic values range from − 6.2 to + 5.8‰ and − 31.3 to + 33.3‰, respectively, they are also highly variable in the rift floor where they attain maximum values. Fluoride base levels in the precursor vitreous volcanic rocks are higher (between 3750–6000 ppm) in minerals such as cordierite and muscovite while secondary minerals like illite and kaolinite have lower remnant fluoride (< 1000 ppm). Thus, geochemical F − enrichment in regional groundwater is mainly due to a) rock alteration, i.e. through long residence times and natural discharge and/or enhanced leakages of deep seated geothermal water reservoirs, b) secondary concentration fortification of natural reservoirs through evaporation, through reduced recharge and/or enhanced abstraction and c) through additional enrichment of fluoride after volcanic emissions. The findings are useful to help improve water management in Naivasha as well as similar active rift setting environments. [ABSTRACT FROM AUTHOR]

Throughout the Holocene, the climate of the Mediterranean region has been strongly influenced by variability in the atmospheric circulation of the high and low latitudes. A prominent example for such Holocene climate perturbations is the ‘8.2 kyr B.P. climatic event’. Reorganization of Northern Hemisphere atmospheric circulation patterns resulted in variations of temperature and precipitation distribution across the Mediterranean. The effects of changing high- and low-latitude atmospheric circulation on Mediterranean climate in relation to the 8.2 kyr B.P. climatic event are, however, not well understood. Here we present a high-resolution record of stable hydrogen isotope composition of plant-wax n -alkanes (δD wax ) across the 8.2 kyr B.P. climatic event from the Tenaghi Philippon peat deposit (NE Greece) in order to characterize patterns of precipitation and changes in atmospheric circulation in the Eastern Mediterranean region. Our record reveals pronounced changes in δD wax that correlate closely with previously published palynological data. A long-term decline in δD wax values characterizes the lower part of the section. The 8.2 kyr B.P. climatic event itself is connected to two distinct positive δD wax excursions: a minor shift in δD wax around 8.2 kyr B.P. and a major shift in δD wax between ca. 8.1 and 8.0 kyr B.P.. The upper part of the section shows a progressive trend towards higher δD wax values. We link shifts in δD wax to changes in Mediterranean air mass trajectories supplying precipitation to NE Greece caused by variations in the relative contributions of northerly-derived, D-depleted moisture and southerly-derived, D-enriched moisture. Possible control mechanisms for alternating air mass trajectories include changes in the influence of the Siberian High and differences in the influence of the African and Asian monsoon circulation on anticyclonic conditions in the Mediterranean region as well as regional inflow of moist air masses from the Aegean Sea. [ABSTRACT FROM AUTHOR]

The development of East African savannas is crucial for the origin and evolution of early hominins. These ecosystems, however, vary widely in their fraction of woody cover and today range from closed woodland to open grassland savanna. Here, we present the first Plio-Pleistocene long-term carbon isotope (δ 13 C) record from pedogenic carbonate and Suidae teeth in the southern East African Rift (EAR). These δ 13 C data from the Chiwondo and Chitimwe Beds (Karonga Basin, Northern Malawi) represent a southern hemisphere record in the EAR, a key region for reconstructing vegetation patterns in today's Zambezian Savanna, and permit correlation with data on the evolution and migration of early hominins in today's Somali-Masai Endemic Zone. The sediments along the northwestern shore of Lake Malawi contain fossils attributed to Homo rudolfensis and Paranthropus boisei . The associated hominin localities (Uraha, Malema) are situated between the well-known hominin bearing sites of the Somali-Masai Endemic Zone in the Eastern Rift and the Highveld Grassland in southern Africa, and fill an important geographical gap for hominin research. Persistent δ 13 C values around −9‰ from pedogenic carbonate and suid enamel covering the last ∼4.3 Ma indicate a C 3 -dominated closed environment with regional patches of C 4 -grasslands in the Karonga Basin. The overall fraction of woody cover of 60–70% reflects significantly higher canopy density in the Malawi Rift than the Eastern Rift through time. The discrepancy between the two savanna types originated in the Late Pliocene, when the Somali-Masai ecosystem started to show increasing evidence for open, C 4 -dominated landscapes. Based on the Malawi δ 13 C data, the evolution of savanna ecosystems in Eastern Africa followed different patterns along the north-south extent of the EAR. The appearance of C 4 -grasses is considered a driver of evolutionary faunal shifts, but despite the difference of ecosystem evolution in the north, similar hominins and suids occurred in both landscapes, pointing to distinct habitat flexibility and also nutritional versatility. [ABSTRACT FROM AUTHOR]

A total of 141 samples mostly located in the Coastal Chain and the Sila Massif of Northern Calabria have been collected from 125 different springs and analyzed chemically and for the isotopic ratios 2 H/ 1 H and 18 O/ 16 O of water, with the ultimate aim to investigate isotope–elevation relationships for local meteoric waters. The Small Springs Method (SSM) has been adopted for this purpose. The hydrogeological characteristics of the watersheds of interest indicate that the sampled springs are discharged from water circuits hosted in alluvial and colluvial deposits rather than in the underlying rock substrata. The chemical characteristics of the sampled waters suggest that they are immature and related to shallow and short water circuits, in spite of the variable degree of chemical evolution. The spring waters of relatively high Total Ionic Salinity (TIS >12.5 meq/L) and those from watersheds of comparatively large elevation range (>650 m) and relatively large areas (>17 km 2 ) have been excluded from the analysis of elevation–isotope relationships. An oxygen isotope lapse rate of −0.194 ‰/100 m has been found for the spring water samples of Northern Calabria as a whole, whereas the obtained hydrogen isotope lapse rates are −1.23 ‰/100 m for the Coastal Chain and −1.45 ‰/100 m for the Sila Massif based on measured isotope values and optimized elevation. The following O-isotopes equation is recommended to estimate the average elevation ( H i in m) of the recharge areas of Northern Calabria aquifer systems: δ O 18 = − 0.00194 · H i − 5.91 (1) The maximum estimated uncertainty due to variations in the δ 18 O value over time is 202 m. Use of H isotopes is not recommended for constraining average recharge elevations due to important local variations, reflecting in different relations for the Coastal Chain and the Sila Massif. Assuming that Equation (1) holds true throughout Northern Calabria, an iso-distribution map of the δ 18 O value in rainfall has been drawn for this area. [ABSTRACT FROM AUTHOR]

The Silltal Fault is the northern brittle continuation of the Brenner Fault Zone, marked by a narrow zone of cataclasis and, in three locations, clay-rich fault gouges. The clay mineral composition of these gouges is dominated by higher temperature 2M polytype illite/muscovite, with no 1M/1M illite or mixed layer illite/smectite detected. Smectite is limited to the northern samples from the Stephansbrücke location, whereas chlorite is present in all samples. The K-Ar ages from the different sample size fractions (<0.1, <0.4, <2, 2-6, 6-10 μm, 'whole rock gouge') show a wide spread, from ca. 115 to 12 Ma, with ages consistently decreasing with grain size. Although the ranges overlap, ages from the northern Stephansbrücke samples are generally older (115-36 Ma) than those from the south near Matrei (55-12 Ma), possibly reflecting increasing regional metamorphic temperatures to the south. The well-defined linear relationship between apparent age and hydrogen stable isotope (δD) values establishes a direct correlation between rejuvenation of the K-Ar system and increased interaction with meteoric water introduced and focussed within the fault zone. The dependence of both apparent age and δD on grain size also indicates that radiogenic and stable isotope exchange was controlled by grain size, reflecting new 2M illite growth, mechanical grinding of protolith muscovite during cataclastic faulting, or both. The results demonstrate the advantages of combining radiogenic and stable isotope analysis in interpretation of K-Ar ages from clay fault gouges. The combined approach was necessary to establish the crucial influence on apparent K-Ar ages of meteoric water influx focussed on the fault zone and its interaction with clay-size-fraction grains. [ABSTRACT FROM AUTHOR]

Interactions between the atmosphere, biosphere, cryosphere, hydrosphere, and geosphere are most active in the critical zone, a region extending from the tops of trees to the top of unweathered bedrock. Changes in one or more of these spheres can result in a cascade of changes throughout the system in ways that are often poorly understood. Here we investigate how past and present climate change have impacted permafrost, hydrology, and ecosystems on the Tibetan Plateau. We do this by compiling existing climate, hydrologic, cryosphere, biosphere, and geologic studies documenting change over decadal to glacial-interglacial timescales and longer. Our emphasis is on showing present-day trends in environmental change and how plateau ecosystems have largely flourished under warmer and wetter periods in the geologic past. We identify two future pathways that could lead to either a favorable greening or unfavorable degradation and desiccation of plateau ecosystems. Both paths are plausible given the available evidence. We contend that the key to which pathway future generations experience lies in what, if any, human intervention measures are implemented. We conclude with suggested management strategies that can be implemented to facilitate a future greening of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

During the Messinian (7.24–5.33 Ma), the highly dynamic Mediterranean environment was concomitantly governed by global climate changes and regional tectonic activity affecting the connectivity to the global ocean. The combined effects generated extreme and rapid paleoenvironmental changes culminating in the Messinian Salinity Crisis (MSC; 5.96–5.33 Ma). Here, we reconstruct paleoenvironmental conditions recorded in the Agios Myron section (Crete Island, Greece) between ∼7.2 and 6.5 Ma that indicate marked changes affecting the eastern Mediterranean region prior to the onset of the MSC. Hydrogen isotope ratios measured on alkenones produced by haptophyte algae within the Mediterranean water column, coupled to carbon isotopes measured on long chain n -alkanes produced by higher terrestrial plants show three important dry periods peaking at 6.98, 6.82 and 6.60 Ma accompanied by shifts in vegetation, transitioning from dominantly C 3 to markedly increased C 4 plants contribution and intermittent recurrence of C 3 vegetation at ∼6.99 Ma and 6.78 Ma. Mean annual air temperatures reconstructed using branched glycerol dialkyl glycerol tetraethers (brGDGTs) average 13 °C with an overall pattern that permits orbitally-controlled pacing of the regional climate. Additionally, the branched and isoprenoid tetraether index and bulk carbon and oxygen isotope ratios indicate changes in the source(s) of organic matter and evolution of the basin towards a closed and arid system. These results support a model of ongoing restriction affecting the eastern Mediterranean Sea from ∼7 Ma onwards and reveal a protracted aridification of the Mediterranean domain prior to the onset of the MSC. • Ongoing isolation and aridification of eastern Mediterranean in Early Messinian. • Highly evaporative intervals are associated with shifts in vegetation. • Increased C 4 plant contribution over an overall cooling continental trend. • Decoupling of marine and continental domains after ∼6.9 Ma. • Overlap of regional and local signals and changes in organic matter sources. [ABSTRACT FROM AUTHOR]

We document the interplay between meteoric fluid flow and deformation processes in quartzite-dominated lithologies within a ductile shear zone in the footwall of a Cordilleran extensional fault (Kettle detachment system, Washington, USA). Across 150 m of shear zone section, hydrogen isotope ratios (δD) from synkinematic muscovite fish are constant (δD ∼ −130‰) and consistent with a meteoric fluid source. Quartz-muscovite oxygen isotope thermometry indicates equilibrium fractionation temperatures of ∼365 ± 30 °C in the lower part of the section, where grain-scale quartz deformation was dominated by grain boundary migration recrystallization. In the upper part of the section, muscovite shows increasing intragrain compositional zoning, and quartz microstructures reflect bulging recrystallization, solution-precipitation, and microcracking that developed during progressive cooling and exhumation. The preserved microstructural characteristics and hydrogen isotope fingerprints of meteoric fluids developed over a short time interval as indicated by consistent mica 40 Ar/ 39 Ar ages ranging between 51 and 50 Ma over the entire section. Pervasive fluid flow became increasingly channelized during detachment activity, leading to microstructural heterogeneity and large shifts in quartz δ 18 O values on a meter scale. Ductile deformation ended when brittle motion on the detachment fault rapidly exhumed the mylonitic footwall. [ABSTRACT FROM AUTHOR]

Combined petrofabric, microstructural, stable isotopic, and 40Ar/39Ar geochronologic data provide a new perspective on the Ceno-zoic evolution of the northern Snake Range metamorphic core complex in east-central Nevada. This core complex is bounded by the northern Snake Range detachment, interpreted as a rolling-hinge detachment, and by an underlying shear zone that is dominated by muscovite-bearing quartzite mylonite and interlayered micaschist. In addition to petrofabric, microstructural analysis, and 40Ar/39Ar geochronology, we use hydrogen isotope ratios (δD) in synkinematic white mica to characterize fluid-rock interaction across the rolling-hinge detachment. Results indicate that the western flank of the range preserves mostly Eocene deformation (49-45 Ma), characterized by coaxial quartz fabrics and the dominant presence of metamorphic fluids, although the imprint of meteoric fluids increases structurally downward and culminates in a shear zone with a white mica 40Ar/39Ar plateau age of ca. 27 Ma. In contrast, the eastern flank of the range displays pervasive noncoaxial (top-to-the-east) fabrics defined by white mica that formed in the presence of meteoric fluids and yield Oligocene-Miocene 40Ar/39Ar ages (27-21 Ma). Evolution of the Oligocene-Miocene rolling-hinge detachment controlled where and when faulting was active or became inactive owing to rotation, and therefore where fluids were able to circulate from the surface to the brittle-ductile transition. On the western flank (rotated detachment), faulting became inactive early, while continued active faulting on the eastern flank of the detachment allowed surface fluids to reach the mylonitic quartzite. The combined effects of synkinematic recrystallization and fluid interaction reset argon and hydrogen isotope ratios in white mica until the early Miocene (ca. 21 Ma), when the brittle-ductile transition was exhumed beneath the detachment. [ABSTRACT FROM AUTHOR]

Paleoelevation reconstructions of the North American Cordillera inferred from the oxygen (δ18O) and hydrogen (δD) isotope ratios of terrestrial paleoclimate proxy materials (soils, ashes, lake sediments) suggest rapid north-to-south migration of topography in the early Cenozoic (pre-49 Ma to 28 Ma). The validation of this reconstruction relies on an accurate understanding of the δ18Op and the associated regional climate change in response to the uplift of the western North America. Here we study this response using a global climate model (GCM) with explicit δ18Op diagnostics (ECHAM5-wiso) focusing on the isotopic effects of different types of precipitation, vapor mixing, recycling and moisture source and compare the response against estimates made using a Rayleigh distillation models of moist adiabatic condensation (RDM). Four experiments are performed with Eocene topography inferred from terrestrial stable isotope paleoaltimetry records to investigate how southward propagation of topography affects regional climate (temperature, precipitation and circulation pattern) and δ18Op over North America. Our experiments predict δ18Op patterns that are broadly consistent with maps of temporally binned proxy δ18O and generally support an early Cenozoic north-to-south propagation of high topography in the North American Cordillera. They do not support the commonly made assumption that isotopic fractionation occurs primarily through rainout following Rayleigh distillation nor the application of modern empirical δ18Op lapse rates to past environments. In our GCM simulations, precipitation processes and climate changes that are not captured by RDMs substantially affect δ18Op. These processes include shifts in local precipitation type between convective and large-scale rain and between rain and snow; intensification of low-level vapor recycling particularly on leeward slopes; development of air mass mixing and changes in wind direction and moisture source. Each of these processes can have significant (≥2‰) influences on δ18Op that are comparable in magnitude to surface uplift of hundreds or even thousands of meters. In many regions, these processes fortuitously compensate each other, explaining the apparent agreement between ECHAM5-wiso and proxy δ18O and, more broadly, between RDM estimates and observed δ18O-elevation relationships. In some regions, compensation is incomplete, and as a result, ECHAM5-wiso δ18Op does not agree with estimates from the RDM. In these regions, including the interior of the northern cordillera and the eastern flank of the southern Cordillera, moderate adjustments of paleoelevations may be in order. [ABSTRACT FROM AUTHOR]

Paleoelevation reconstructions of mountain belts and orogenic plateaus based on stable isotope climate and precipitation records benefit greatly from present-day calibrations that relate the fractionation of hydrogen (ᵟD) and oxygen (ᵟ18O) isotopes in precipitation to orographic rainfall. Here, we establish a first-order template of ᵟD and ᵟ18O of modern meteoric waters across the Central Anatolian Plateau (CAP) and its bordering Pontic and Taurus Mountains. We identify key regions in the plateau interior and along the plateau margins that have the potential to reliably record topography-related paleotemperature and paleoprecipitation changes as recovered from stable isotope paleosol, fossil teeth or lipid proxy data. Based on ᵟD and ᵟ18O data of more than 480 surface water samples from small catchments and springs, we characterize moisture sources affecting the net isotopic budget of precipitation over the CAP and analyze how orographic rainout and plateau aridity shape modern patterns of ᵟD and ᵟ18O in precipitation. The Taurus Mountains bordering the CAP to the south act as a major orographic barrier for transport of predominantly winter moisture and exhibit isotopic lapse rates of approximately -20‰/km for ᵟD and -2.9‰/km for ᵟ18O across an elevation range of nearly 3000 m. The Pontic Mountains at the northern margin of the CAP force perennial moisture to ascend and condensate revealing lapse rates of -19‰/km for ᵟD and -2.6‰/km for ᵟ18O. The difference in the predominant moisture source for the southern and northern margins of the CAP (North African versus Atlantic air masses) is manifested in systematic north-south differences in near-sea level meteoric water compositions of Δ(ᵟDN-S) ~20 permil and Δ(ᵟ18ON-S) ~3 permil in a swath across the central part of the plateau. Stable isotope data from the semi-arid plateau interior with rainfall as low as 300 to 500 mm/yr and mean summer temperatures attaining 23 °C, provide clear evidence for an evaporative regime that drastically affects surface water and runoff compositions and results in a local meteoric water line for the plateau interior that follows ᵟD = 4.0 · ᵟ18O - 29.3. Strongly evaporitic conditions contrast rainfall patterns along the plateau margins including their immediate leeward flanks where ᵟD- and ᵟ18O-elevation relationships are reliable predictors of modern topography. [ABSTRACT FROM AUTHOR]

This study describes the hydroclimate evolution of the eastern Mediterranean Basin during the early Messinian (7.2 to 6.5 Ma) time-interval based on analysis of a succession at Agios Myron (Crete, Greece), prior to the onset of the Messinian Salinity Crisis (5.96–5.33 Ma). Specifically, we report sea surface temperature and salinity reconstructions based on a combined analysis of biomarkers and oxygen isotopes of planktonic foraminifera. Data reveal that a negative water budget and strong hydrologic and climate variability characterized the eastern Mediterranean Basin at this time, and we identify three distinct phases. In Phase 1 (7.2–6.9 Ma), a shift to more positive oxygen isotope values in planktonic foraminifera at ~7.2 Ma is attributed to progressive gateway restriction of Mediterranean–Atlantic corridors and subsequent cooling until 6.9 Ma. In Phase 2 (6.9–6.7 Ma), distinct warm and hypersaline events (at 6.9–6.82 and 6.72 Ma) resulted in stressed marine microfauna during periods of strong evaporation. An important step-change in the Mediterranean restriction at 6.72 Ma may have resulted from shallowing of the Mediterranean gateways and reduced Mediterranean marine outflow. During Phase 3 (6.7–6.5 Ma) this gateway shallowing reduced the oceanic input into the Mediterranean Basin causing significant hydrological changes, reflected in a wide range of temperature and salinity fluctuations accompanied by enhanced water-column stratification. The data presented here counterbalance the general lack of quantitative temperature and especially salinity estimates available for the Mediterranean Messinian, time interval where we still highly rely on modelling for such evaluations. This study highlights the severity of preconditioning stages leading to the Messinian Salinity Crisis in the Mediterranean and sets values for extreme salinity conditions that could still host marine life. [Display omitted] • Three restriction phases affected the eastern Mediterranean between 7.2 and 6.5 Ma. • Colder water and normal salinity characterized the Mediterranean during 7.2–6.9 Ma. • Periods of strong evaporation observed for the 6.9–6.7 Ma interval. • Warm-hypersaline events (6.9–6.82 and 6.72 Ma) caused extreme environmental stress. • Restriction at 6.7–6.5 Ma was induced by tectonics and modulated by climate. [ABSTRACT FROM AUTHOR]

Assessing the geochemical signature and the role of fluids in a key Variscan detachment zone demonstrates the link between crustal deformation, thermo-mechanical events and Variscan mineralization. We document meteoric fluid infiltration into the ductile segment of the Late-Carboniferous Quiberon detachment zone (QDZ), when synkinematic muscovite and tourmaline crystallized and equilibrated with deuterium-depleted surface-derived fluids during high-temperature deformation. Titanium-in-muscovite thermometry supported by microstructures indicate that syntectonic isotope exchange between fluids and hydrous minerals occurred above 500 °C. 40Ar/39Ar muscovite data (∼319–∼303 Ma) and U(–Th)/Pb geochronology on zircon, monazite and apatite (∼318–∼305 Ma) from syntectonic leucogranites together with microstructural and geochemical (U and REE contents) data suggest that meteoric fluid-rock-deformation interaction started at ∼320 Ma and played a major role in leaching uranium at ∼305 Ma. U–Th/Pb data (∼330–∼290 Ma) from migmatites located below the QDZ strengthen the idea that meteoric fluid infiltration, detachment activity, syntectonic leucogranite emplacement and migmatization were coeval and allowed the development of a sustained hydrothermal system. • δD values of synkinematic hydrous minerals document the presence of 300 Ma-old meteoric fluids in a key Variscan detachment zone. • Meteoric fluid-rock interactions occurred during high-temperature deformation (>500 °C) in the Quiberon detachment footwall. • Coeval detachment activity, leucogranite emplacement and migmatization maintained the hydrothermal system for ∼17 Myr. [ABSTRACT FROM AUTHOR]

The surface uplift of mountain belts is generally assumed to reflect progressive shortening and crustal thickening, leading to their gradual rise. Recent studies of the Andes indicate that their elevation remained relatively stable for long periods (tens of millions of years), separated by rapid (1 to 4 million years) changes of 1.5 kilometers or more. Periodic punctuated surface uplift of mountain belts probably reflects the rapid removal of unstable, dense lower lithosphere after long-term thickening of the crust and lithospheric mantle. [ABSTRACT FROM AUTHOR]

Landlocked basins like the Caspian Sea are highly sensitive to changes in their hydrological budget, especially at times of disconnection from the global ocean. Here, we reconstruct the Pliocene to Pleistocene palaeohydrological and palaeoenvironmental changes occurring in the South Caspian Basin between ~3.6 and ~ 1.9 Ma, using compound-specific hydrogen isotope (δ2H) data on long chain n -alkanes and alkenones. Additionally, we established a record of mean annual air temperature (MAT) and the source of organic matter, based on the relative distribution of branched and isoprenoid glycerol dialkyl glycerol tetraethers (BIT). The ~55‰ variation in the δ2H measured on the terrestrial plant long chain n -alkanes indicates significant continental hydrological changes in the region surrounding the Caspian Sea over the investigated 1.7 Myr interval. The MAT and BIT data show that the so-called Akchagylian marine incursion at around 2.75 Ma, marked by influx of marine biota into the Caspian Basin, originated from a cold region of the open ocean, endorsing a hydrological connection with the Arctic domain. The onset of the regional Apsheronian stage at ~2.13 Ma, identified by the invasion of Tyrrhenocythere sp. ostracods, coincided with a change towards constant δ2H n -alkane and is shortly followed by the occurrence of alkenones in the Caspian Basin. The relative distributions of alkenones and their δ2H values indicate that a connection with a saline basin, most likely the Black Sea, was established at the Akchagylian–Apsheronian transition. [Display omitted] • 55‰ δ2H n -alkanes variation hint at hydrology changes in 3.6–1.9 Ma circum-Caspian. • Cooling at 2.75 Ma Akchagylian marine incursion caused by influx from Arctic. • Alkenones and their δ2H support a Caspian–Black Sea connection starting at ~2.13 Ma. [ABSTRACT FROM AUTHOR]

A large and highly dynamic aquatic system called Paratethys governed important elements of the middle and late Miocene (15.97–5.33 Ma) hydrology in western Eurasia. So far, the impact of the vast Paratethys water body on the Eurasian climate, however, is not yet understood. Here we apply biomarker analyses coupled to compound-specific hydrogen and carbon isotope data to track changes in sea surface temperature, mean annual air temperature, hydrological budget and vegetation changes to reconstruct long-term western Eurasian climate conditions between 12.7 and 7.65 Ma in the Black Sea region. Biomarker data from Panagia (Russia) indicate the presence of three exceptionally evaporative intervals peaking at 9.65, 9.4 and 7.9 Ma. These peaks in evaporation relate to aridity, parallel increasing fire activity and are associated with changes in vegetation. Carbon isotope and pollen data support the evidence of an increase in C 4 plants associated with these dry intervals. At 9.66 Ma, alkenone producing algae appear in the basin and thrive for the subsequent two million years. Cumulative fluctuations in both hydrology and surface temperature of Paratethys might have enhanced rainfall seasonality in western Eurasia as a response to changes in evaporation over the Paratethys basin. Our combined data suggest a strong regional imprint on overall climate patterns, dominated by basin dynamics causing Paratethys volume and surface reduction. Collectively, the presented biomarker results provide evidence of severe droughts affecting the late Miocene circum-Paratethys region, leading to a direct impact on the evolution of biota in the basin and its surroundings. [Display omitted] • Three droughts peaking at 9.65, 9.4 and 7.9 Ma disturbed circum-Paratethys ecosystem. • Carbon isotopes indicate increase in C 4 plant contribution during these droughts. • Increased fire activity during droughts parallel changes towards open vegetation. • Alleged connection to a proximal basin may trigger the alkenone producers advent. • Decoupling of Paratethys from the global climate and hydrology hints its importance. [ABSTRACT FROM AUTHOR]

We present the first stable isotope paleoaltimetry estimates for the hinterland of the eroded Variscan Belt of Western Europe based on the hydrogen isotope ratios of muscovite from syntectonic leucogranites that have been emplaced at ∼315 Ma. We focus on the Limousin region (Western Massif Central, France) where peraluminous granites are spatially associated with strike-slip and detachment shear zones that developed as a consequence of Late Carboniferous syn- to post-orogenic extension. In this region, we show that the north-east corner of the Millevaches massif (located at the junction between brittle and ductile fault systems) represented a pathway for Earth surface-derived fluids that penetrated the crust and reached the ductile segment of the low-angle Felletin detachment zone. Using microstructural, thermometry, hydrogen isotope and 40Ar/39Ar geochronological data, we show that these Variscan meteoric fluids interacted with hydrous silicates during high temperature deformation between ∼318 and 310 Ma. For paleoaltimetry purposes, we reference our hydrogen isotope record (δ D) of ancient meteoric fluids from mylonitic rocks to ∼295 Myr-old records retrieved from freshwater shark remains preserved in the Bourbon l'Archambault basin that developed in the external zones of the orogen. A ∼76‰ difference in δ D meteoric water values between the Millevaches massif (δ D meteoric water value = −96 ± 8‰) and the Bourbon l'Archambault foreland basin (δ D water value = −20 ± 6‰) is consistent with paleoaltimetry estimates of 3.4 ± 0.7 km based on a modern lapse rate of ∼-22‰/km for δ D water values. The rather large difference in δ D values between the foreland basin and the continental interior suggests that the hinterland of the Variscan belt of western Europe was high enough to act as a barrier to moisture transport from the south-south-east and induce an orographic rain shadow to the north. • Hydrous silicates represent robust archives for Carboniferous meteoric fluid flow. • Stable isotope paleoaltimetry can be applied to the Paleozoic era. • The Variscan hinterland of Western Europe was a topographic high at 315 Ma. [ABSTRACT FROM AUTHOR]

The central Menderes Massif in western Turkey is a bivergent metamorphic core complex characterised by two detachment faults that operated with opposite sense of shear. Here, we present K–Ar ages and hydrogen isotope data for fault gouge as well as fission track and (U–Th)/He ages for apatite and zircon from bedrock samples to constrain the timing of detachment faulting. Comparison of the K–Ar ages and low-temperature thermochronologic ages indicates brittle faulting at temperatures between ~240 and ~70 °C. At the western termination of the Gediz detachment, K–Ar ages between ~12 and ~5 Ma suggest rather continuous faulting since the mid-Miocene; a Pliocene phase of rapid slip is mainly recorded in the eastern part of this detachment. In contrast, K–Ar ages from the Büyük Menderes detachment cluster at 22–16 and 9–3 Ma and provide evidence for two phases of faulting, which is in accordance with new and published low-temperature thermochronologic data. Hydrogen isotope ratios of −76 to −115‰ indicate infiltration of meteoric water during detachment faulting and gouge formation. The youngest K–Ar ages and cooling histories for hanging and footwall rocks imply that the activity of both detachments ended ~3 Ma ago when the currently active grabens were established. • K–Ar ages of fault gouge record detachment faulting in a bivergent core complex. • Two detachment faults were active diachronously between ~22 Ma and ~3 Ma. • The Büyük Menderes detachment experienced two phases of faulting since ~22 Ma. • The Gediz detachment was active continuously from mid-Miocene to late Pliocene. [ABSTRACT FROM AUTHOR]

The ability of stony corals to thrive in the oligotrophic (low-nutrient, low-productivity) surface waters of the tropical ocean is commonly attributed to their symbiotic relationship with photosynthetic dinoflagellates 1,2 . The evolutionary history of this symbiosis might clarify its organismal and environmental roles 3 , but its prevalence through time, and across taxa, morphologies and oceanic settings, is currently unclear 4-6 . Here we report measurements of the nitrogen isotope ( 15 N/ 14 N) ratio of coral-bound organic matter (CB-δ 15 N) in samples from Mid-Devonian reefs (Givetian, around 385 million years ago), which represent a constraint on the evolution of coral photosymbiosis. Colonial tabulate and fasciculate (dendroid) rugose corals have low CB-δ 15 N values (2.51 ± 0.97‰) in comparison with co-occurring solitary and (pseudo)colonial (cerioid or phaceloid) rugose corals (5.52 ± 1.63‰). The average of the isotopic difference per deposit (3.01 ± 0.58‰) is statistically indistinguishable from that observed between modern symbiont-barren and symbiont-bearing corals (3.38 ± 1.05‰). On the basis of this evidence, we infer that Mid-Devonian tabulate and some fasciculate (dendroid) rugose corals hosted active photosymbionts, while solitary and some (pseudo)colonial (cerioid or phaceloid) rugose corals did not. The low CB-δ 15 N values of the Devonian tabulate and fasciculate rugose corals relative to the modern range suggest that Mid-Devonian reefs formed in biogeochemical regimes analogous to the modern oligotrophic subtropical gyres. Widespread oligotrophy during the Devonian may have promoted coral photosymbiosis, the occurrence of which may explain why Devonian reefs were the most productive reef ecosystems of the Phanerozoic., Competing Interests: Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Individual dietary specialization, where individuals occupy a subset of a population's wider dietary niche, is a key factor determining a species resilience against environmental change. However, the ontogeny of individual specialization, as well as associated underlying social learning, genetic, and environmental drivers, remain poorly understood. Using a multigenerational dataset of female European brown bears (Ursus arctos) followed since birth, we discerned the relative contributions of environmental similarity, genetic heritability, maternal effects, and offspring social learning from the mother to individual specialization. Individual specialization accounted for 43% of phenotypic variation and spanned half a trophic position, with individual diets ranging from omnivorous to carnivorous. The main determinants of dietary specialization were social learning during rearing (13%), environmental similarity (5%), maternal effects (11%), and permanent between-individual effects (9%), whereas the contribution of genetic heritability (3%) was negligible. The trophic position of offspring closely resembled the trophic position of their mothers during the first 3-4 years of independence, but waned with increasing time since separation. Our study shows that social learning and maternal effects were more important for individual dietary specialization than environmental composition. We propose a tighter integration of social effects into studies of range expansion and habitat selection under global change., Competing Interests: Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Conservation of species and ecosystems is increasingly difficult because anthropogenic impacts are pervasive and accelerating. Under this rapid global change, maximizing conservation success requires a paradigm shift from maintaining ecosystems in idealized past states toward facilitating their adaptive and functional capacities, even as species ebb and flow individually. Developing effective strategies under this new paradigm will require deeper understanding of the long-term dynamics that govern ecosystem persistence and reconciliation of conflicts among approaches to conserving historical versus novel ecosystems. Integrating emerging information from conservation biology, paleobiology, and the Earth sciences is an important step forward on the path to success. Maintaining nature in all its aspects will also entail immediately addressing the overarching threats of growing human population, overconsumption, pollution, and climate change., (Copyright © 2017, American Association for the Advancement of Science.)