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The Cordillera Blanca detachment in the highest elevations of the Peruvian Andes has been accommodating synconvergent extension since the late Miocene. Stable isotope analysis of synkinematic mica from its exhumed footwall shear zone provides new constraints on deep meteoric-hydrothermal circulation during ductile deformation and regional paleoelevation. Muscovite and biotite that deformed and/or grew synkinematically in the shear zone have δ2H values of −131‰ to −58‰ and −149‰ to −98‰ (versus Vienna standard mean ocean water, VSMOW), respectively. The δ2H value difference between coexisting muscovite and biotite is consistent with equilibrium fractionation of the same fluid at the same temperature. Calculated δ2H values of water (−107‰ to −78‰) in equilibrium with these micas are indistinguishable from those of present-day, deeply circulated (9–11 km) hot spring waters emanating from the fault. Such low-δ2H fluids indicate circulation of meteoric water to the depths of the brittle-ductile transition that cannot be explained by other mechanisms. Average recharge paleoelevation for water entering the shear zone based on hydrogen isotopes was 3400 + 500/–700 m (1σ). This is near, but ~500 m below, the present-day mean elevation of the catchments feeding modern hot springs of 3965 ± 880 m, and ~700 m below the 4200 + 700/–900 m mean recharge elevation derived from δ2H values of modern surface and thermal water. The consistency between modern and ancient fault-assisted hydrothermal systems and elevation suggests that high topography, steep relief, and meteoric-hydrothermal circulation have persisted throughout the history of the Cordillera Blanca detachment system.

This study provides a new magnetostratigraphy for the stratigraphic interval that includes the late Miocene Haliminhanı and Hayranlı mammal fossil assemblages of the Sivas Basin (central Anatolia, Turkey). The fossil assemblages show high faunal similarities to the Pikermian chronofauna, which forms part of the Old World Savannah Paleobiome that formed during a time of global cooling, aridification, and grassland expansion. Previous biostratigraphic age estimates placed the fossil horizons within European Mammal Neogene (MN) zones MN11-MN12, which tentatively places the Anatolian Haliminhanı and Hayranlı localities in the ca. 9 to 7 Ma time interval. Nearby dated sites harboring Pikermian fauna in Turkey, Greece, and Bulgaria range in age between 11 and 7.3 Ma. Our new magnetostratigraphy in 140 m thick fluviolacustrine deposits refines the age estimate for the Sivas Basin to 8.0–6.5 Ma for the Haliminhanı and Hayranlı fossil mammal-bearing levels. Published bulk carbonate δ13C and δ18O values of the fluvio-lacustrine beds indicate a positive water balance and suggest no significant long-term changes in hydrology and primary productivity within the former Sivas Basin lake. Further inspection of the δ13C and δ18O values shows two intervals of increased δ13C (by ca. 6–8‰) that are followed by a similar decrease over total time intervals of ca. 150 kyr. The increase in δ13C in a lacustrine carbonate can be related to an increase in biogenic productivity, which may result from changes in nutrient input and temperature. The absence of simultaneous changes in δ18O during peaks in δ13C make temperature an unlikely driver and we surmise that adjustments to nutrient input to the basin were responsible for changes in δ13C. Overall, the results suggest that the Pikermian chronofauna of the Sivas Basin thrived under relatively stable local hydrological and climatic conditions. At Haliminhanı, the Pikermian fauna flourished well into the Messinian, as opposed to Greek and Bulgarian sites where faunal turnover was proposed to have occurred under a cooling climate and aridification across the Tortonian-Messinian boundary.

International audience; 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.

Reconstructing long-term continental temperature change provides the required counterpart to age equivalent marine records and can reveal how terrestrial and marine temperatures were related during times of extreme climate change such as the Miocene Climatic Optimum (MCO) and the following Middle Miocene Climatic Transition (MMCT). Carbonate clumped isotope temperatures (T(Δ47)) from 17.5 to 14.0 Ma Central European paleosols (Molasse Basin, Switzerland) display a temperature pattern during the MCO that is similar to coeval marine temperature records. Maximum temperatures in the long-term soil T(Δ47) record (at 16.5 and 14.9 Ma) lag maximum ocean bottom water temperatures, lead global ice volume, and mark the initiation of minimum global ice volume phases. The suggested onset of the MMCT, deduced by a marked and rapid decline in Molasse Basin soil temperatures is coeval with cooling reported in high-latitudinal marine records. This is best explained by a change in the seasonal timing of soil carbonate formation that was likely driven by a modification of rainfall seasonality and thus by a major reorganization of mid-latitude atmospheric circulation across Central Europe. In particular, our data suggest a strong climate coupling between the North Atlantic and Central Europe already in the middle Miocene.

The Black Sea basin is the sink for some of the largest European rivers and has acted as such, since it was part of the Eastern Paratethys. The late Miocene-to-Pliocene sedimentary record of the Black Sea documents several phases of strongly evaporitic conditions associated with extreme changes in regional hydrology. Here, we present the first combined record of continental temperature, soil type, and biomass burning in the circum–Black Sea region from the late Miocene to the transition into Pliocene (~ 10.0 to 5.0 Ma). We use branched glycerol dialkyl glycerol tetraethers (brGDGT) to reconstruct mean annual air temperature (MAT) and soil pH within the catchment of the Black Sea basin and complement these data with evidence from charcoal morphology as a proxy for burned biomass. The brGDGT data reveal generally decreasing temperatures and acidic soils between ~ 10 and 8.5 Ma, overlapping with increase in herbaceous cover in the Black Sea region. The Pontian flooding at 6.12 Ma is characterized by large quantities of organic debris and charcoal fragments in the basin and is followed by cooling starting at 5.97 Ma, event that is superimposed on the TG 20 and TG 22 glacial peaks (at 5.8 Ma). Between 5.8 and 5.0 Ma, the brGDGTs seem to be primarily derived from a cold steppe environment. Enhanced fire activity coinciding with generally cooler temperatures and a higher proportion of herbaceous plants are indicative of increased continentality between 5.8 and 5.0 Ma in the Black Sea region.

Continued Africa-Eurasia convergence resulted in post–11 Ma surface uplift of the Central Anatolian Plateau (CAP) and the westward escape of the Anatolian microplate. Contemporaneously, a central Anatolian fluvio-lacustrine system developed that covered extensive parts of the rising CAP. Today, the semi-arid CAP interior—except for the Konya closed catchment—drains toward the Black Sea, the Mediterranean Sea, and the Persian Gulf. Lake connectivity and drainage patterns of the fluvio-lacustrine system in the evolving plateau region are, however, largely unknown. Here, we present sedimentological and stable isotopic (δ13C and δ18O) data (N = 665) from 13 well-dated lake sections covering the former fluvio-lacustrine depocenters of the southern CAP. Persistently (>1 m.y.) stable paleoenvironmental and hydrological conditions suggest that a low-relief environment characterized the southern CAP during plateau uplift. Throughout the late Miocene, various open and closed lakes of the southern CAP drained into closed, terminal lakes within the plateau interior. Sedimentation east of the Tuz Gölü fault ceased during the early Pliocene (ca. 5.3–3.6 Ma), when the eastern CAP became connected to marine base level as a result of river incision shortly after the switch from regional compression to extension. A final phase of lacustrine carbonate sedimentation characterizes most sampled basins, yet occurred asynchronously over the extent of the CAP. Therefore, the final episode of lacustrine sedimentation is unlikely to have been the result of a climatic event, consistent with the absence of a clear aridification trend in the lacustrine δ18O data. Rather, capping carbonates reflect the interplay of surface uplift and transition from inward- to outward-drained plateau regions and concomitant lake reorganization during the formation of the CAP and its margins.

Hydrothermal veins and altered feldspar are evidence for fluid circulation in granitic rocks in the continental crust. The hydrothermal alteration of feldspar affects the deformation behavior of granitoids, especially if it occurs before orogeny. Geochronology can establish the timing of fluid circulation to determine if this fluid-driven alteration plays a role in crustal deformation. Although existing dating techniques cannot be applied to feldspar alteration directly, absolute ages of fluid circulation can be obtained from hydrothermal veins. We combined U-Pb geochronology and hydrogen isotope data (δD) from epidote [Ca2Al2(Al,Fe3+) Si3O12(OH)] to unravel the hydration of post-Variscan granitoids in the Alpine orogen. The recent protocol for epidote U-Pb dating proves for the first time that fluids of meteoric origin infiltrated the granitoids in Permian times by exploiting synrift faults, consistent with the δD values of the epidote-forming fluids. This hydration event caused at least some degree of feldspar hydration and weakening of the granitic rocks ~260 m.y. before their pervasive structural overprint by the Alpine orogeny. The preservation of Permian U-Pb ages despite Alpine orogenic processes confirms epidote as a powerful tool with which to unveil pre-orogenic hydration events in metagranitoids. Our analytical approach broadens insights into the water cycle in the middle continental crust in orogens.

Many stable isotope paleoaltimetry studies have focused on paleoelevation reconstructions of orogenic plateaus such as the Tibetan or Andean Plateaus. We address the opportunities and challenges of applying stable isotope paleoaltimetry to “smaller” orogens. We do this using a high‐resolution isotope tracking general circulation model (ECHAM5‐wiso) and explore the precipitation δ18O (δ18Op) signal of Cenozoic paleoclimate and topographic change in the European Alps. Results predict a maximum δ18Op change of 4–5‰ (relative to present day) during topographic development of the Alps. This signal of topographic change has the same magnitude as changes in δ18Op values resulting from Pliocene and Last Glacial Maximum global climatic change. Despite the similar magnitude of the isotopic signals resulting from topographic and paleoclimate changes, their spatial patterns across central Europe differ. Our results suggest that an integration of paleoclimate modeling, multiproxy approaches, and low‐elevation reference proxy records distal from an orogen improve topographic reconstructions., Plain Language Summary: Here we use a climate model with water isotopes implemented to explore the maximum precipitation isotopic signal of Cenozoic topographic and paleoclimate change in the European Alps. Our results show that the impact of topography change has the same magnitude as changes in the isotopic composition of local precipitation resulting from Pliocene and Last Glacial Maximum global climatic change., Key Points: High‐resolution isotope tracking general circulation model (ECHAM5‐wiso) is used to explore changes in past oxygen isotope ratios in precipitation in the Alps. Model‐simulated isotopic signals of topographic change and difference between glacials and interglacials show the same magnitude. Low‐elevation proxy records improve reconstructions of paleotopography by reducing long‐term climate change bias., German Research Foundation (DFG) http://dx.doi.org/10.13039/501100001659

Situated at the southern edge of the proto-North Sea the lower Eocene Schöningen Formation of the Helmstedt Lignite Mining District, Lower Saxony, Germany is characterized by several lignite seams alternating with estuarine to brackish interbeds. Here, we present carbon isotope data of bulk organic matter (δ13CTOC), organic carbon content (%TOC), and palynomorphs from a 98 m thick sequence of the Schöningen Formation embedded into a new robust age model. This is based on eustatic sea-level changes, biostratigraphy, and a correlation to existing radiometric ages. Based on the δ13CTOC data we observe six negative carbon isotope excursions (CIEs) reflecting massive short-term carbon cycle perturbations. A strong CIE of −2.6 ‰ in δ13CTOC values in the Main Seam and the succeeding marine interbed can be related to the Paleocene–Eocene Thermal Maximum (PETM). The subsequent CIE of −1.7 ‰ in δ13CTOC values may be correlated with the Eocene Thermal Maximum 2 (ETM2) or slightly older events preceding the ETM2. High-amplitude climate fluctuations including at least 4 minor CIEs with a maximum negative shift of −1.3 ‰ in δ13CTOC in the upper part of the studied section are characteristic for the EECO. Palynological analysis across the Main Seam proved that shifts in δ13CTOC values are correlated with changes in the peat forming wetland vegetation, specifically the change from a mixed angiosperm and gymnosperm flora to an angiosperm dominated vegetation at the onset of the PETM. The PETM-related CIE shows a distinct rebound to higher δ13CTOC values shortly after the onset of the CIE, which is here recognized as a common feature of terrestrial and marginal marine PETM-records worldwide and may be related to changes in the vegetation including different carbon isotope budgets of gymnosperms and angiosperms.

High-precision analysis of the excess abundance (relative to the stochastic distribution) of mass 48 isotopologues in CO2 evolved from acid digestion of carbonates (∆48) has not been possible until recently due to the relatively low natural abundance of 18O. Here we show that the 253 Plus™ gas source mass spectrometer equipped with Faraday cups and 1013 Ω resistors can perform combined ∆47 and ∆48 analyses on carbonates with external reproducibilities (1SD) of 0.010 ‰ and 0.030 ‰, respectively. ~10 mg aliquots of five carbonate reference materials (ETH 1, ETH 2, ETH 3, ETH 4, and Carrara) are digested with phosphoric acid at 90 °C using a common acid bath. The evolved CO2 is purified using an automated gas preparation system (including cryotraps and a GC) and analyzed for its ∆47 and ∆48 compositions using the dual inlet system of a 253 Plus™ gas source mass spectrometer. Raw ∆47 and ∆48 values are finally normalized to the Carbon Dioxide Equilibrium Scale (CDES). In ∆47, CDES 90°C vs. ∆48, CDES 90°C space, calcite reference materials Carrara, ETH 3 and ETH 4 agree with the equilibrium curve for calcite after adding semi-empirically determined 90 °C acid fractionation factors of 0.196 ‰ (for ∆47) and 0.136 ‰ (for ∆48) to theoretical ∆63 and ∆64 data. Agreement between measured and theoretically expected ∆48, CDES 90°C highlights the accuracy of our high-precision clumped isotope analytical setup. Combined analysis of the abundances of mass 47 and mass 48 isotopologues in CO2 evolved from acid digestion of natural carbonates has excellent potential for the determination of accurate and highly precise paleotemperatures as well as for the identification of rate-limiting kinetic processes involved in biomineralization. A formation temperature of 15(±2) °C is obtained on the 95 % confidence level for the Upper Cretaceous chalk sample ETH 3.

AIM: We advocate an interdisciplinary approach to biogeography, integrating geology and paleobiology to examine how biodiversity dynamics evolved as mountain ranges formed through (geological) time. LOCATION: Global; case study: Anatolia (Turkey). METHODS: We discuss the links between surface uplift and biodiversity dynamics and review recent developments for reconstructing the history of geography and biodiversity. To illustrate an integrative approach to biogeography, we present a case study of Neogene Anatolia. In particular, we reconstruct Anatolian paleogeography based on a synthesis of both quantitative and qualitative evidence, and review the fossil record of the regional flora and fauna, to identify changes in compositions that might be induced by surface uplift and associated environmental changes. RESULTS: The Central Anatolian Plateau and its mountainous margins display different histories of surface uplift during the late Miocene to Pliocene, which are detectable in the regional fossil record of large mammals. Overall changes in vegetation and climatic conditions for the whole region also align with the general time frame of surface uplift. MAIN CONCLUSIONS: Our discussion and case study highlight the value of an integrative biogeographic framework, by combining knowledge and techniques from geology and paleobiology to simultaneously consider the biotic and environmental dynamics in space and time. Neogene surface uplift in Anatolia has affected the regional biota, particularly the diversity of plants and large mammals, along with well‐known global and regional changes in climate and other environmental factors. To disentangle the effects of different, but most likely interactive environmental changes at various scales, we call for rigorous examination of the geological record in a biogeographic framework, using innovative methods to uncover how environmental and biotic processes have shaped mountain biodiversity.

Hydrogen isotopic composition (δD) and 40Ar/39Ar geochronological data of neomineralized clay minerals from fault rocks and cleavage seams in the Sevier belt record primary involvement of surface-sourced fluids during Cretaceous–Paleogene mountain building events. δD values of authigenic clays range from − 78.8 ± 1.7 ‰ to − 97.2 ± 3.2 ‰ . Given temperature constraints of mineral formation, we calculate δD values of mineralizing fluids as ∼−63 to −96‰, which fall within the range of δD values of Cretaceous–Paleogene surface waters in the region. The potential infiltration and presence of surface fluids at depths of several kilometers during deformation implies that pore spaces and fractures acted as conduits for surface water. Uplift of thrust sheets generated topography that favored meteoric recharge and flow of fluids into margins of the foreland basin, which were subsequently incorporated into the propagating thrust wedge. This is in contrast to the hypothesis that the release of overpressured metamorphic fluids dominates during fold–thrust belt evolution. As a result of shortening and tectonic uplift, fluid flows through basin sediments toward the foreland basin as meteoric waters recharge sediments at the basin margins. This study shows that stable isotopic compositions of shallow, deformation-related clay minerals are robust and may be used alongside other surface fluid proxies to probe the origin and composition of ancient fluids in orogenic systems.

The Neogene sedimentary successions of the Black Sea basin are ideal to study ancient paleoclimatic and hydrological changes in the Eurasian continental interior. Previous investigations revealed several phases of strongly enhanced evaporitic and dry conditions in the late Miocene. Here, we present the first reconstructed mean annual air temperature (MAAT) and soil pH data, combined with compound specific hydrogen isotopic (δD) records for the late Miocene to early Pliocene Black Sea basin, based on the analyses of biomarkers. Our MAAT, pH and δD data indicate that in the latest Tortonian (~8–7 Ma) mean annual air temperatures were approximately 5° higher than today, and that dry and warm climatic conditions prevailed. The early Messinian (7–6 Ma) is marked by a gradual change towards more humid, but still warm, conditions. The MAAT record shows a sharp decrease from 16 to 8 °C during the late Messinian (6.2–5.8 Ma) coinciding with a change towards extremely dry conditions. This cold and dry interval correlates to the time span marked by the late Miocene cooling of the northern hemisphere, and may also reflect a sea level change, restricting the Azov/Taman basin from the Black Sea. The calculated soil pH values in the range 7.1 to 7.7 are indicative for alkaline soils, such of those in the northern Eurasian hinterland, indicating a dominant northern Black Sea riverine source for the soil biomarkers. Finally, the Pliocene is marked by warmer conditions and lower soil pH, indicating a revival of the climatic conditions that characterized the Black Sea area during the late Messinian.

Reconstructing Oligocene-Miocene paleoelevation contributes to our understanding of the evolutionary history of the European Alps and sheds light on geodynamic and Earth’s surface processes involved in the development of Alpine topography. Despite being one of the most intensively explored mountain ranges worldwide, constraints on the elevation history of the European Alps, however, remain scarce. Here we present stable and clumped isotope geochemistry measurements to provide a new paleoelevation estimate for the mid-Miocene (~14.5 Ma) European Central Alps. We apply stable isotope δ-δ paleoaltimetry on near sea level pedogenic carbonate oxygen isotope (δ18O) records from the Northern Alpine Foreland Basin (Swiss Molasse Basin) and high-Alpine phyllosilicate hydrogen isotope (δD) records from the Simplon Fault Zone (Swiss Alps). We further explore Miocene paleoclimate and paleoenvironmental conditions in the Swiss Molasse Basin through carbonate stable (δ18O, δ13C) and clumped (Δ47) isotope data from three foreland basin sections in different alluvial megafan settings (proximal, mid-fan, and distal). Combined pedogenic carbonate δ18O values and Δ47 temperatures (30 ± 5 °C) yield a near sea level precipitation δ18Ow value of −5.8 ± 0.2 ‰ and in conjunction with the high-Alpine phyllosilicate δD record suggest that the region surrounding the SFZ attained surface elevations of > 4000 m no later than the mid-Miocene. Our near sea level δ18Ow estimate is supported by paleoclimate (iGCM Echam5-wiso) modeled δ18O values, which vary between −4.2 and −7.6 ‰ for the Northern Alpine Foreland Basin.

Determining how the elevation of the Northern Andes has evolved over time is of paramount importance for understanding the response of the Northern Andes to deformational and geodynamic processes and its role as an orographic barrier for atmospheric vapor transport over geologic time. However, a fundamental requirement when using stable isotope data for paleoaltimetry reconstructions is knowledge about the present-day changes of δ18O and δD with elevation (isotopic lapse rate). This study defines the present-day river isotopic lapse rate near the Equator (∼3°S) based on analysis of δ18O and δD of surface waters collected from streams across the Western Cordillera and the Inter-Andean depression in Southern Ecuador. The results for the two domains show a decrease of δ18O with elevation which fits a linear regression with a slope of −0.18‰/100 m (R2= 0.73,n= 83). However, we establish a present-day lapse rate of −0.15‰/100 m for δ18O (R2= 0.88,n= 19) and -1.4‰/100 m for δD (R2= 0.93,n= 19) from water samples collected along the west facing slopes of the Western Ecuadorian Cordillera which is mainly subject to moisture transport from the Pacific. We argue that this empirical relationship, consistent with those obtained in different tropical areas of the world, can inform stable isotope paleoaltimetry reconstructions in tropical latitudes.

Triple oxygen isotope measurements are an emerging tool in paleoclimate reconstructions. In this contribution we develop the application of triple oxygen isotope measurements to lacustrine sediments to reconstruct past elevations. We focus on a well-constrained sample set from the Eocene North American Cordillera (Cherty Limestone Formation, Elko Basin, NV, United States, 42–43.5 Ma) on the east side of the elevated Nevadaplano. We present triple oxygen isotope measurements on freshwater lacustrine chert samples from the Cherty Limestone Formation. Across an evaporation trend spanning 6.5‰ in δ18O values we observe a negative correlation with Δ′17O ranging from −0.066 to −0.111‰ (λRL= 0.528), with an empirical slope (λchert, δ′17O vs. δ′18O) of 0.5236. Additionally, we present new carbonate clumped isotope (Δ47) temperature results on the overlying fluvial-lacustrine Elko Formation, which indicate an error-weighted mean temperature of 32.5 ± 3.8°C (1σ), and evaporatively enriched lake water spanning δ18O values of −3.7 to +3.5‰ (VSMOW). Paired chert and carbonate δ18O values demonstrate that co-equilbrium among the carbonate and chert phases is unlikely. Thus, as also previously suggested, it is most likely that Elko Basin chert formed during early diagenesis in equilbirium with pore waters that reflect evaporatively18O-enriched lake water. Using this scenario we apply a model for back-calculating unevaporated water composition to derive a source water of δ′18O = −16.1‰ (VSMOW), similar to modern local meteoric waters but lower than previous work on paired δ18O- δD measurements from the same chert samples. Further, this back-calculated unevaporated source water is higher than those derived using δD measurements of Late Eocene hydrated volcanic glass from the Elko Basin (average δ′18O equivalent of approximately −18.4‰, VSMOW). This suggests, assuming Eocene meteoric water Δ′17O values similar to today (∼0.032‰), either that: (1) the hypsometric mean elevation recorded by the lacustrine Cherty Limestone was lower than that derived from the average of the volcanic glass δD measurements alone; or (2) there was hydrogen exchange in volcanic glass with later low δD meteoric fluids. Nonetheless, our new findings support a relatively high (∼2.5–3 km) plateau recorded in the Elko Basin during the mid-Eocene.

We present two carbonate oxygen and carbon isotope records from late Miocene – early Pleistocene stratigraphic sections from the southern flank of the Issyk Kul basin, Kyrgyz Tien Shan. The two sections are 700 and 500 m thick and composed of fluvial and lacustrine sediments. They were dated using magnetostratigraphy (Roud et al., G-Cubed, in review) and 26Al/10Be isochron burial dating (presented here).Carbonate stable isotope data is useful for reconstruction of climate in Asia over the Cenozoic. Oxygen isotopes are commonly used to detect moisture sources and their interaction with topography. Pedogenic carbon isotopes are used to reconstruct past atmospheric CO2 levels or the spread of C4 vegetation.The environment of Central Asia is primarily affected by the northern mid-latitude westerlies − winds transporting moisture eastward across Eurasia. Issyk Kul basin is situated on the windward side of the northern Tien Shan. Published data suggest that the Tien Shan mountain ranges interacted with the westerlies since late Oligocene and reorganized Central Asian climate during Neogene (Caves et al., 2017; Charreau et al., 2012; Macaulay et al., 2016; Wang, et al., 2020). The amount of existing published paleoclimate data from northern Central Asia is scarce compared to interior China, and therefore the influence of the Tien Shan uplift on climate in Asia during the Cenozoic is poorly reconstructed.Our data provide new insight into the role of the range and its interaction with the westerlies in forming climate on the windward side of the northern Tien Shan in the late Neogene. We combine our data with published stratigraphically-older sections nearby (Macaulay et al., 2016) to complete the Neogene stable isotope record of the Issyk Kul basin and study how the evolution of the basin influenced regional climate.Our d18O and d13C values show slightly positive trends, unlike stratigraphically-older data from the Issyk Kul basin. The preliminary interpretation suggests that the circulation pattern within the range was changed in late Miocene possibly reflecting active tectonic uplift northward of the basin and an increase in aridification.

The Miocene experienced both, ice-house periods with continental ice-sheets covering both poles and warm greenhouse conditions with strongly increased global temperature, glacier retreat and sea-level rise. The Mid-Miocene Climatic Optimum (MMCO) is the most pronounced warming event in the last 24 Ma, standing out in a time of protracted cooling. The MMCO is marked by a period of intensive global warming between ca. 17 and 15 Ma. The subsequent Mid-Miocene Climate Transition (MMCT), in contrast, was affected by global temperature decline, growth of Antarctic ice sheets, sea level fall and marine biota overturn.Miocene climate conditions were intensely studied on both, global and regional scales, based on i.a. marine isotope records and continental paleobotanical and mammalian fossil data sets. Despite the dense data sets continental Miocene temperature evolution still remains unclear owing to a large range of inferred temperatures and/or poor age constraints of the associated records.Here, we present a long-term terrestrial climate record that covers the time interval between ~20 and ~13 Ma and is based on stable (δ18O) and clumped isotope (Δ47) geochemical data. We apply Δ47 thermometry on terrestrial foreland basin sediments to reconstruct the Middle Miocene continental temperature evolution for central Europe. Pedogenic carbonates from well dated fossil soils from several sites in the Northern Alpine Foreland Basin (Switzerland) reveal warm and stable temperatures for the early Miocene (20 – 19 Ma), followed by overall strongly enhanced variability in temperatures with maximum values attained between ca. 17 and 14 Ma. We observe a highly dynamic transition to cooler climates at the end of the MMCO and a subsequent rapid temperature decline of approximately 20°C after 14 Ma during the MMCT. The highly variable temperature patterns during the cooling period coincide with phases of high seasonality in the precipitation pattern as derived from oxygen isotope compositions of soil water.

The Central Anatolian Plateau (CAP, Turkey, elevation ca. 1-1.5 km) was established during the late Miocene. Prior to Pleistocene surface uplift of its southern margin (Tauride Mountains), a southern margin orographic barrier with similar-to-present elevations (ca. 2 km) existed between 8 and 5 Ma. To unravel the interactions between tectonics and Earth surface processes, we quantify biotic and abiotic parameters for the late Miocene to Pliocene. As the CAP exposes presently incised fluvio-lacustrine sedimentary rocks of well-dated Miocene to Pliocene age, the region provides an excellent archive for reconstructing past landscape dynamics, such as surface uplift, lake hydrology, and drainage integration. Within this established framework, we now reconstruct the late Miocene to Pliocene ecosystem by measuring clumped isotope (Δ47) temperatures of carbonate formation and δ13C and δ18O values of paleosol carbonate and fossil mammal tooth enamel. Collectively, our data allow for the reconstruction of paleoclimate, vegetation types (C3 vs. C4), mammalian diet, landscape heterogeneity, and seasonality. The first clumped isotope-derived paleotemperatures indicate a large (8 °C) temperature difference at ca. 5.5 Ma between lacustrine carbonate from the Mediterranean coastal region (Adana Basin; ca. 26 ± 1.8 °C) and paleosol carbonate from the central Anatolian interior (ca. 18 ± 1.7 °C), which likely reflects the higher elevation of the CAP. Soil carbonate δ13C values from the plateau interior (13 sites, N= 344, ca. 10 to 2 Ma) are much higher between ca. 8 and 5 Ma (ca. –3 to 0 ‰) than earlier or later in time (ca. –8 to –5 ‰), which indicates the presence of a significant component of C4 vegetation, characterized by wooded grasslands and grasslands, during the latest Miocene. In contrast, C3-dominated vegetation reflecting more wooded environments were dominant at ca. 10 Ma and from 4 to 2 Ma. The increase in C4 vegetation during the late Miocene is coeval with surface uplift of the southern CAP margin, whereas an increase of C3 vegetation by the Pliocene could coincide with a phase of subsidence of the southern CAP margin prior to its final phase of Pleistocene surface uplift. Furthermore, we collected mammal tooth enamel samples (equid, bovid, rhinocerotid, suid) from 11 individuals at one ca. 9 Ma-old and one latest Miocene-Pliocene fossil site. δ13C and δ18O values indicate the mammals at the two nearby fossil sites had varying diets and therefore access to different vegetation and water supplies. We are currently improving the stratigraphic framework and dating of these fossil sites, as well as obtaining tooth enamel δ13C and δ18O values of 44 more individuals to further constrain paleoenvironmental conditions and eventually the causality between tectonics and Earth surface processes in central Anatolia. References: Meijers et al., 2018a: Palaeo3, doi: 10.1016/j.palaeo.2018.03.001; Meijers et al., 2018b: EPSL, doi: 10.1016/j.epsl.2018.05.040; Huang, Meijers et al., 2019: J of Biogeography, doi: 10.1111/jbi.13622; Meijers et al., 2020: Geosphere, doi: 10.1130/GES02135.1

The Late Miocene has been considered one of the most climatically stable periods of the Cenozoic, time span characterized by minor long-term cooling and ice growth. Especially, the Tortonian-Messinian Transition is recognized as a priority for paleoenvironmental reconstruction and climate modelling due to the significant paleoenvironmental changes preceding the Messinian Salinity Crisis (MSC; 5.97-5.33 Ma). Here, we present stable oxygen (δ18O) and carbon (δ13C) isotopes measured on benthic and planktonic foraminifera from Potamida section (Crete Island, eastern Mediterranean). The δ18O results indicate a decoupling between the surface and the bottom water column starting before the Tortonian-Messinian boundary. The difference between planktonic and benthic oxygen isotope signals (Δδ18O) further provides an estimate of the degree of water column stratification during that time. The δ13C data indicate a generally trend towards lighter values as an excellent illustration of the Late Miocene Carbon Isotope Shift (LMCIS; 7.6-6.6 Ma) due to progressive restriction of the Mediterranean basin, with the exception of the 7.38-7.26 Ma time interval where significantly heavier δ13C values are documented in both records. Such changes in carbon cycle seem to be most pronounced in the planktonic foraminiferal record (surface waters) through a 6-cycle development indicative of a cyclic productivity pattern during the latest Tortonian. The entire record is substantiated by sea surface temperature (SST) estimates based on TEX86 biomarker based proxy. The reconstructed SST record shows that a warm phase characterized the late Tortonian sea surface (~27⁰C), time followed by a strong, steady cooling starting with earliest Messinian, when the SSTs dropped to values as low as 20⁰C. The outcome of the combined stable isotope and biomarker based SST data hint to increased salinity in the surface waters already before the Messinian, while at the Tortonian-Messinian Transition, the conditions in the surface waters changed towards cooler (~24⁰C) and normal salinity conditions.

International audience; 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 and merge to the northwest with the South Armorican Shear Zone.Here we show that the NE 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 geochemistry and 40Ar/39Ar geochronological data, we show that these Variscan meteoric fluids interacted with hydrous silicates during high temperature deformation between at least ~318 and 310 Ma.For paleoaltimetry purposes, we reference our hydrogen isotope record (δD) 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 δDmeteoric water values between the Millevaches massif (δDmeteoric water value = -96 ± 8‰) and the Bourbon l’Archambault foreland basin (δDwater value = -20 ± 6‰) is consistent with minimum paleoaltimetry estimates of 3400 ± 700 m based on a modern lapse rate of ~-22‰/km for δDwater values. The rather large difference in δD 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.

Soil respiration (Rs), the production of carbon dioxide in soils, increases dramatically from deserts to forested ecosystems. Rs values thus provide a potential tool to identify past ecosystems if recorded in sedimentary archives. Here, we propose a quantitative method to reconstruct past Rs values from paleosols. This method reverses the soil paleobarometer, a proxy that estimates past atmospheric CO2 concentration values (CO2atm) from paleosols while considering a narrow range of variation for Rs. We use past CO2atm values from marine proxies to reconstruct soil respiration from a 20 million year-long isotopic record from northeastern Tibet covering the transition from the Eocene greenhouse to the Oligocene icehouse. We show that Rs dropped at least 4-fold through the transition into the Oligocene icehouse, marking the spread of boreal desert-steppes of Central Asia. We show that increasing aridity and the decline of monsoonal rainfall, in parallel with global cooling, caused the fall of soil respiration. These highly dynamic Rs emphasize the need for a systematic screening of paleosol isotopic data before using the soil paleobarometer to reconstruct CO2atm

Orogenic plateaus are extensive, elevated, arid, generally internally drained, morphotectonic provinces of low internal topographic relief that represent a striking and enigmatic feature of Earth’s continental landscapes. They are located along convergent plate boundaries and have a profound impact on regional and global climate, erosional processes, local- to far-field deformation mechanisms and the long-term distribution of biomes and biodiversity. Although the paramount role of large orogenic plateaus in shaping our planet is widely appreciated, the question of why, where, and how some orogenic systems develop large plateaus remains a first-order problem in our understanding of lithospheric evolution and orogenic processes.Here, we present a clumped isotope paleoaltimetry study to document the elevation history of the Iranian Plateau, with the goal of understanding the rates and mechanisms of orogenic plateau rise. This plateau is in the Arabia-Eurasia collision zone, has a mean elevation of ~ 1.8 km, steep margins with mountain peaks higher than 4 km, and experienced surface uplift sometime after the middle Miocene as documented by the occurrence of ca. 17-My-old marine deposits in the plateau interior.Preliminary results from Early Miocene to Quaternary pedogenic carbonates on the plateau interior and the adjacent, less elevated, intermontane Tarom basin suggest that surface uplift must have occurred sometime between 12-11 and 8 Ma. The lack of significant crustal shortening and thickening during this time interval and the occurrence of a renewed phase of adakitic volcanism by ca. 11 Ma suggests that surface uplift may have been driven by deep-seated processes associated with asthenospheric flow.

Quantifying the interactions between tectonics and Earth surface processes on orogenic plateaus requires the acquisition of a multitude of field observations and geological proxies. Here, we reconstruct the topographic development of the Central Anatolian Plateau (Turkey), identify the geodynamic drivers of plateau formation, and constrain the climatic boundary conditions that shaped the fluvio-lacustrine basins, drainage integration, and vegetation and biodiversity dynamics.Our comprehensive dataset includes sedimentological and field observations, 40Ar/39Ar ages, magnetostratigraphy, lacustrine carbonate δ18O and δ13C data (n=665) from thirteen sections in upper Oligocene to Pliocene continental basins of the CAP interior, and 10Be erosion rates. We also analyze existing fossil faunal (mammal) and floral databases to assess biodiversity dynamics through time and we model isostatic rebound to understand drainage integration.The CAP and its steep, southern Tauride margin emerged from the Mediterranean Sea ~12-11 Ma and ~8-7 Ma ago, respectively. Contemporaneously to surface uplift, a fluvio-lacustrine system covered extensive parts of the rising CAP. Today, the semi-arid CAP interior − except for the Konya Closed Catchment (KCC) − drains towards the Black Sea, Mediterranean Sea and Persian Gulf.Our stable isotope paleoaltimetry data show similar-to-present elevations (~2 km) of the southern CAP margin by 5 Ma. Surface uplift affected the diversity of plants and large mammals, and was coeval with ignimbritic magmatism, forearc shortening and distributed compression. We suggest that removal of lithospheric mantle below Anatolia led to surface uplift of the CAP interior, followed by surface uplift of the southern CAP margin as a result of subduction-related crustal thickening. Persistently (>1 Myr) stable paleoenvironmental and hydrological conditions recorded by the former fluvio-lacustrine Anatolian depocenters suggest that a low-relief environment characterized the CAP during plateau uplift. Throughout the late Miocene, various open and closed lakes of the southern CAP drained into closed, terminal lakes within the plateau interior. Sedimentation east of the Tuz Gölü Fault ceased rapidly during the early Pliocene (from 5.3-3.6 Ma), when river incision led to a connection with marine base level. Analysis of incision patterns reveals that drainage integration was not driven by capture of the interior drainage by aggressive rivers draining the plateau margin, but rather by top-down avulsion or overflow due to the establishment of a more positive water balance in some of the closed catchments of the plateau interior. Drainage integration occurred shortly after the switch from regional compression to extension and the onset of escape tectonics of the new Anatolian microplate, when fault partitioning of the existing low-relief plateau interior may have led to drainage integration.In a next step to reconstruct the paleoenvironmental conditions of the CAP, we obtain δ18O and δ13C values from fossil mammal tooth enamel, which allows for the reconstruction of mammalian diet, and in turn reflects paleovegetation, as well as seasonality for the Mio-Pliocene climate.ReferencesMeijers et al., 2018a: Palaeo3, doi: 10.1016/j.palaeo.2018.03.001Meijers et al., 2018b: EPSL, doi: 10.1016/j.epsl.2018.05.040Huang, Meijers et al., 2019: J of Biogeography, doi: 10.1111/jbi.13622Meijers et al., 2020: Geosphere, doi: 10.1130/GES02135.1

Exhumed fault rock of the central Alpine Fault Zone (South Island, New Zealand) shows extensive clay mineralization, and it has been the focus of recent research that aims to describe the evolution and frictional behavior of the fault. Using Quantitative X-ray powder diffraction, 40 Ar/ 39 Ar geochronology, hydrogen isotope (δD) geochemistry, and electron microbeam analysis, we constrain the thermal and fluid conditions of deformation that produced two predominant clay phases ubiquitous to the exposed fault damage zone, illite and chlorite. Illite polytype analysis indicates that most end-member illite and chlorite material formed in equilibrium with meteoric fluid (δD = −55 to −75‰), but two locations preserve a metamorphic origin of chlorite (δD = −36 to −45‰). Chlorite chemical geothermometry constrains crystal growth to T = 210–296 °C. Isotopic analysis also constrains illite growth to T

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 C4 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.

International audience; 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 (δD) 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 δDmeteoric water values between the Millevaches massif (δDmeteoric water value = −96 ± 8‰) and the Bourbon l'Archambault foreland basin (δDwater value = −20 ± 6‰) is consistent with paleoaltimetry estimates of 3.4 ± 0.7 km based on a modern lapse rate of ∼-22‰/km for δDwater values. The rather large difference in δD 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.

Holocene climate dynamics have strongly influenced precipitation patterns in the Eastern Mediterranean region. This holds particularly true for the ‘8.2 kyr BP climatic event’, arguably the strongest perturbation of early to mid-Holocene climate. Here we present a biomarker record of leaf wax-derived n -alkane distributions and stable isotopic composition of total organic carbon (δ 13 C TOC ) along with palynological data from the fen peat archive of Tenaghi Philippon (TP), NE Greece, spanning the interval from 8.7 to 7.5 kyr BP. Our record documents the response of in situ vegetation within the Philippi peatland to changing hydrological conditions, and addresses the applicability of organic proxies such as the ‘aquatic index’ ( P aq ), average chain length (ACL) and δ 13 C TOC as indicators of peat surface moisture conditions at the study site. The long chain n -alkanes ( n -C 27 , n -C 29 and n -C 31 ) typical of vascular terrestrial plants, dominated the peat sequence. A period of relatively dry surface conditions, indicated by low values of P aq and elevated ACL values, in concert with elevated δ 13 C TOC values, preceded the 8.2 kyr BP climatic event from ca. 8.7 to 8.2 kyr BP. Slightly wetter, more humid conditions, suggested by an increase in P aq as well as reduced ACL and δ 13 C TOC values, characterized the interval of the 8.2 kyr BP climatic event. Notably, the increase in surface wetness, as indicated by the biomarker record, coincided with a marked rise in fern spore proportion as well as increasing proportion of pollen from aquatic taxa. Following the 8.2 kyr BP event, a distinct change in paleohydrology at TP became apparent from ca. 7.9 kyr BP onward. An increase in the abundance of the mid-chain length n -alkanes ( n -C 23 and n -C 25 ), indicative of an increased contribution from aquatic plants to the sediment, together with a steep increase in P aq and a decrease in ACL, as well as variation in δ 13 C TOC , imply considerably elevated surface moisture levels, likely caused by the increased activity of the karstic system of the surrounding mountains. Collectively, the biomarker proxies and pollen data reveal a concise picture of changing moisture conditions at TP in response to the 8.2 kyr BP climatic event.

Enhanced aridification of Central Asia driven by the combined effects of orogenic surface uplift, Paratethys retreat, changes in atmospheric moisture transport and global cooling is one of the most prominent Cenozoic climate change events of the Northern Hemisphere. Deciphering regional long-term patterns of Central Asian hydrology is, therefore, a key element in understanding the role of Northern Hemisphere mid-latitude drying in the global hydrological system. This study characterizes long-term palaeoenvironmental conditions between the late Oligocene and early Miocene in south-eastern Kazakhstan based on stable isotopes, elemental geochemistry and laser ablation uranium–lead geochronology from alluvial, fluvial and pedogenic deposits. Sedimentary facies and geochemical weathering indices suggest an increased surface and ground water discharge fed by orographically-enhanced precipitation in the Tien Shan hinterland. In contrast, pedogenic stable isotope data and elevated rates of magnesium fixation in clay minerals mirror enhanced rates of evaporation in the vadose zone due to protracted aridification. This study posits that pronounced surface uplift of the Tien Shan Mountains during the Oligocene–Miocene transition promoted regionally increased orographic precipitation and the development of fluvial discharge systems. This article is protected by copyright. All rights reserved.

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International audience; Variscan shear zones in the Armorican Massif represent sites of strong fluid‐rock interaction. The hydrogen isotope composition of muscovite (δDMs) from syntectonic leucogranite allows to determine the source of fluids that infiltrated the footwall of three detachment zones and the South Armorican Shear Zone. Using temperatures of hydrogen isotope exchange estimated from microstructural data, we calculate the hydrogen isotope ratios of water (δDwater) present within the shear zones during high‐temperature deformation. A ~40‰ difference in δDwater values from deep to shallow crustal level reveals a mixing relationship between deep crustal fluids with higher δD values that range from −34 to −33‰, and meteoric fluids with δD values as low as −74‰ in the upper part of detachment footwalls.

The Paleocene-Eocene Thermal Maximum (PETM) offers insight into massive short-term carbon cycle perturbations that caused significant warming during a high-pCO2 world, affecting both marine and terrestrial ecosystems. PETM records from the marine-terrestrial interface (e.g. estuarine swamps and mire deposits) are, therefore, of great interest as their present-day counterparts are highly vulnerable to future climate and sea level change. Here, we assess paleoenvironmental changes of mid-latitudinal Late Paleocene-Early Eocene peat mire records along the paleo-North Sea coast. We provide carbon isotope data of bulk organic matter (δ13CTOC), organic carbon content (%TOC), and palynological data from an extensive peat mire deposited at a mid-latitudinal (ca. 41 °N) coastal site (Schöningen, Germany). The δ13CTOC data show a carbon isotope excursion (CIE) of −1.7 ‰ coeval with a conspicuous Apectodinium acme, calling for the presence of the PETM in this coastal section. Due to the exceptionally large stratigraphic thickness of the PETM at Schöningen (10 m of section) we established a detailed palynological record that indicates only minor changes in paleovegetation leading to and during the PETM. Instead, paleovegetation changes mostly follow natural successions in response to changes along the marine-terrestrial interface. Compared to other available peat mire records (Cobham, UK; Vasterival, France) it appears that wetland deposits around the Paleogene North Sea have a typical CIE magnitude of ca. −1.3 ‰ in δ13CTOC. Moreover, the Schöningen record shares major characteristics with the Cobham Lignite, including evidence for increased fire activity prior to the PETM, minor PETM-related plant species changes, a reduced CIE in δ13CTOC, and drowning of the mire (marine ingressions) during much of the PETM. This suggests that paleoenvironmental conditions during the Late Paleocene-Early Eocene, including the PETM, consistently affected major segments of the paleo-North Sea coast.

International audience; The fall into the Oligocene icehouse is marked by a steady decline in global temperature with punctuated cooling at the Eocene-Oligocene transition, both of which are well documented in the marine realm. However, the chronology and mechanisms of cooling on land remain unclear. Here, we use clumped isotope thermometry on northeastern Tibetan continental carbonates to reconstruct a detailed Paleogene surface temperature record for the Asian continental interior, and correlate this to an enhanced pollen data set. Our results show two successive dramatic (>9 °C) temperature drops, at 37 Ma and at 33.5 Ma. These large-magnitude decreases in continental temperatures can only be explained by a combination of both regional cooling and shifts of the rainy season to cooler months, which we interpret to reflect a decline of monsoonal intensity. Our results suggest that the response of Asian surface temperatures and monsoonal rainfall to the steady decline of atmospheric CO2 and global temperature through the late Eocene was nonlinear and occurred in two steps separated by a period of climatic instability. Our results support the onset of the Antarctic Circumpolar Current coeval to the Oligocene isotope event 1 (Oi-1) glaciation at 33.5 Ma, reshaping the distribution of surface heat worldwide; however, the origin of the 37 Ma cooling event remains less clear.

Both the sources and pathways of fluid circulation are key factors to understanding the evolution of low-angle normal fault (LANF) systems and the distribution of mineral deposits in the upper crust. In recent years, several reports have shown the presence of meteoric waters in mylonitic LANF systems at mid-crustal conditions. However, a mechanism for meteoric water infiltration to these mid-crustal depths is not well understood. Here we report paired δ 18 O and δ 2 H isotopic values from dated, neoformed clays in fault gouge in major detachments of the southwest United States. These isotopic values demonstrate that brittle fault rocks formed from exchange with pristine to weakly evolved meteoric waters at multiple depths along the detachment. 40 Ar/ 39 Ar dating of these same neoformed clays constrains the Pliocene ages of fault-gouge formation in the Death Valley area. The infiltration of ancient meteoric fluids to multiple depths in LANFs indicates that crustal-scale normal fault systems are highly permeable on geologic timescales and that they are conduits for efficient, coupled flow of surface fluids to depths of the brittle-plastic transition.

The Plio-Pleistocene expansion of Eastern Africa savanna ecosystems was a major driver for morphological and behavioral innovations in hominin evolution. Most evidence for hominin ecosystem reconstructions originates from the Eastern Rift in today's Somali-Masai Endemic Zone. We provide stable carbon (δ 13 C) and oxygen (δ 18 O) isotope data from 22 bovid, equid, suid, hippopotamid and elephant teeth from the southern part of the East African Rift and supplement these by δ 18 O values of present-day meteoric water. This region (Karonga Basin, Malawi) hosts remains of Homo rudolfensis and Paranthropus boisei . It is situated between hominin-bearing sites in Eastern and Southern Africa and therefore fills an important geographical gap for hominin evolution. Tooth enamel δ 13 C and δ 18 O data of 14 large-bodied mammalian herbivore species from Units 2 and 3 (ca. 4.3 to 0.6 Ma) in the Chiwondo Beds provide information about foraging strategies and vegetation patterns. Our stable isotope data reflect C 3 -dominated ecosystems that permitted access to open C 4 -environments for migratory mammals. Many analyzed taxa show evidence for mixed diets with high abundances of C 3 -biomass consumption; only selected bovids were specialized grazers. δ 18 O of present-day meteoric water reflects rainfall amount and seasonality, elevation, and lake evaporation. δ 18 O values of Karonga Basin herbivore enamel are generally low and cover values similar to present-day drinking water, indicating both, evaporated and freshwater sources. Comparison of δ 13 C values from the Karonga Basin with other Eastern African herbivore communities reveals significant differences in dietary patterns with much more generalized mixed C 3 /C 4 , and pure C 3 feeding behaviors in the Malawi Rift. Similarly, enamel δ 18 O values are lower than in most Plio-Pleistocene Eastern African herbivores, suggesting more humid conditions. Collectively, our data support models in which early hominin foraging activity included access to C 3 -dominated biomes, complicating traditional interpretations linking early human evolutionary innovations to a shift towards savanna habitats.

Eocene hyperthermals are among the most enigmatic phenomena of Cenozoic climate dynamics. These hyperthermals represent temperature extremes superimposed on an already warm Eocene climate and dramatically affected the marine and terrestrial biosphere, yet our knowledge of temperature and rainfall in continental interiors is still rather limited. We present stable isotope (δ18O) and clumped isotope temperature ( Δ 47 ) records from a middle Eocene (41 to 40 Ma) high-elevation mammal fossil locality in the North American continental interior (Montana, USA). Δ 47 paleotemperatures of soil carbonates delineate a rapid +9/−11 °C temperature excursion in the paleosol record. Δ 47 temperatures progressively increase from 23 °C ± 3 °C to peak temperatures of 32 °C ± 3 °C and subsequently drop by 11 °C. This hyperthermal event in the middle Eocene is accompanied by low δ18O values and reduced pedogenic carbonate concentrations in paleosols. Based on laser ablation U/Pb geochronology of paleosol carbonates in combination with magnetostratigraphy, biostratigraphy, stable isotope, and Δ 47 evidence, we suggest that this pronounced warming event reflects the Middle Eocene Climatic Optimum (MECO) in western North America. The terrestrial expression of northern hemisphere MECO in western North America appears to be characterized by warmer and wetter (sub-humid) conditions, compared to the post-MECO phase. Large and rapid shifts in δ18O values of precipitation and pedogenic CaCO3 contents parallel temperature changes, indicating the profound impact of the MECO on atmospheric circulation and rainfall patterns in the western North American continental interior during this transient warming event.