Albert Galy

@article{Tachambalath_etal2023,

title = {Data report: major and trace element composition of silicates and carbonates from Bengal Fan sediments, IODP Expedition 354},

author = {A. P. Tachambalath and C. France-Lanord and A. Galy and T. Rigaudier and J. Charreau},

doi = {10.14379/iodp.proc.354.204.2023},

year  = {2023},

date = {2023-01-01},

journal = {Proceedings of the International Ocean Discovery Program},

volume = {354},

abstract = {During International Ocean Discovery Program Expedition 354, seven sites were drilled along a 320 km east--west transect at 8textdegreeN, constituting a relic of the Neogene sediment record of Himalayan erosion. Bengal Fan is one of the largest deep-sea fans in the world where turbiditic sediments issued from the Ganga and Brahmaputra River Delta and originally supplied by the Himalayan erosion of silicate and carbonate lithologies are deposited and stored. Quantification ofthe chemical composition of silicates and carbonates is necessary to understand the tectonoclimatic history of this region. This report presents the major and trace element concentrations of silicate and carbonate fractions of selected turbiditic samples from Sites U1450 and U1451. Efficient washing followed by refined acid leaching of the sediments was performed to eliminate sea salts and carbonates from these marine sediment samples. Shipboard samples show 20%--40% excess sodium concentration associated with sea salt derived from pore water. Weak acid treatment limits the total carbonate content in the samples to less than 0.1%. Depletion of major and trace elements observed due to acid leaching is attributed to the dissolution of carbonates and cations associated with Fe-Mn oxyhydroxides.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kitayama_etal2021,

title = {Geochemical evidence for carbon and chlorine enrichments in the mantle source of kimberlites (Udachnaya pipe, Siberian craton)},

author = {Y. Kitayama and E. Thomassot and A. Galy and A. Kordakov and A. Golovin and E. DtextquoterightEyrames},

doi = {10.1016/j.gca.2021.09.021},

year  = {2021},

date = {2021-01-01},

journal = {Geochimica et Cosmochimica Acta},

volume = {315},

pages = {295--316},

abstract = {Deep, carbonate-rich melts are key constituents of kimberlites and are crucial for understanding the cycle of volatile elements in the mantle. On the Siberian craton, the Udachnaya-East kimberlite hosts extremely well-preserved nodules composed of chlorides + carbonates + sulfates, that do not present any relict sedimentary textures. These salty nodules display textures that are commonly observed in quenched liquids and may thus represent the very last stage liquid of the kimberlite. Alternatively, they could represent assimilated sedimentary material, or even post-magmatic hydrothermal alteration, because kimberlites are known to ascend through the lithosphere while assimilating material from their wall rocks.Here we focus specifically on those chloride-carbonate nodules, which are composed of 70% chloride + 30% alkali-carbonate and sulfate, and used two radiogenic systems (Rb-Sr, Sm-Nd) and the isotopic composition of sulfur, in addition to their major and trace element compositions (n = 3). We then compared the results with the same geochemical data on host kimberlites (n = 4), sedimentary cover (n = 3) and hydrothermal veins (n = 3).Taken together, our results show that the nodules are not the product of a contamination by the Cambrian sedimentary cover. Trace element patterns of the nodules display extreme enrichments in the same elements that are relatively depleted in the host kimberlite but also in kimberlites worldwide (K, Rb, Sr, Pb), suggesting that chloride-carbonate nodules are snapshots of the latest stage liquid present in the kimberlite system. Their isotopic compositions (Rb-Sr, Sm-Nd and $delta$34S) are consistent with a common magmatic source with their host kimberlite. We propose that chloride-carbonate nodules record a missing compositional endmember, which could explain the trend towards more radiogenic Sr isotope ratios at nearly constant Nd signatures observed in their host kimberlite, as well as in other kimberlites worldwide. This observed trend suggests the presence of a recycled component with high Rb/Sr (such as salts or terrigenous sediments) in the mantle sampled by some kimberlites, either in the lithosphere or the asthenosphere. This study highlights that the role of alkalies and halogens may have been underestimated in the genesis of kimberlites at depths where diamonds are stable, as well as in more evolved magmatic stages. Segregations of chlorides and carbonates occur specifically in sulfate-bearing kimberlites, which may thus sample a mantle domain in which sulfates with $delta$34S \> 0texttenthousand are dominant. The existence of such a reservoir could explain the apparent imbalance observed between the chondritic value ($delta$34S of 0texttenthousand) and the negative S isotopic compositions of mantle sulfides (MORB and peridotites).},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ruan+Galy2021,

title = {On the significance of periglacial conditions in active mountain belts for chemical weathering processes : Insights from the Chayu area, SE Tibet},

author = {X. Ruan and A. Galy},

doi = {10.1016/j.chemgeo.2021.120581},

year  = {2021},

date = {2021-01-01},

journal = {Chemical Geology},

volume = {585},

pages = {120581},

abstract = {Chemical weathering is a key player of the long-term (Ma) timescale carbon cycle. Weathering processes under alpine periglacial environment could be important during the Quaternary glacial-interglacial cycles, but such timescale is difficult to fully apprehend for the weathering impact on C cycles. The Chayu river catchment in SE Tibet spans a geographical gradient from a periglacial environment in the north to a monsoonal environment in the south and we have investigated the various chemical weathering along this climatological gradient. The lithology of the catchment is dominated by granitoid rocks. Due to the active tectonic activity and the periglacial environment, mass wasting deposits including landslide deposits, talus and rock glaciers are found in the catchment. In order to figure out the influence of mass wasting process on water chemistry, we sampled seepage water from the mass wasting deposits and nearby stream water for comparison. Cyclic input contributes 5.7 to 8.2% to the dissolved load of the water samples, suggesting the dominance of weathering contribution within this granitoid catchment. The contributions from sulfuric acid and carbonate to chemical weathering are estimated based on the elemental data and the oxidation of sulfide as the source of dissolved sulfate. In the monsoonal South Chayu, the K*/Si, Ca*/Si ratios of the bedrock landslide seepages are higher than the streams by 265% and 117%, respectively. Together with the high contribution of carbonate (textasciitilde80%) and sulfuric acid (20 to 40%), the results indicates that landslide deposits have strong influences on local water chemistry by processes identical to bedrock landslides of greywacke and carbonate lithology in active mountain belts, suggesting that the enhanced weathering by landslide process can apply to granitoid regions as well. In the North Chayu with periglacial environment, the chemistry of the seepages and streams are nearly identical, and are similar to the landslide seepage water in the south. Such result highlights the role of the periglacial critical zone without the influence of mass wasting deposits that possibly enhances chemical weathering. The high porosity created by repeat freezethaw cycles provides more fresh mineral surfaces for water-rock interaction. But, the low temperature and the partial availability of water, restricted to thaw periods, provide strong kinetic limitations that inhibit the silicate weathering. Such features of the alpine periglacial critical zone led to the preferential weathering of the most reactive mineral phases including calcite, sulfide, and the interlayer K+ of sheet silicates (biotite, chlorite), resulting in the characteristic periglacial water chemistry. The influence of periglacial environment on local water chemistry may apply beyond the North Chayu and may play an important role in modulating the chemical weathering within the transition between Quaternary glacial and interglacial period.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Casola_etal2020,

title = {No evidence for carbon enrichment in the mantle source of carbonatites in eastern Africa},

author = {V. Casola and L. France and A. Galy and N. Bouden and J. Villeneuve},

doi = {10.1130/G47629.1},

year  = {2020},

date = {2020-01-01},

journal = {Geology},

volume = {48},

pages = {971--975},

abstract = {Carbonatites are unusual, carbon-rich magmas thought to form either by the melting of a carbon-rich mantle source or by low-degree partial melting of a carbon-poor (\<80 ppm C) mantle followed by protracted differentiation and/or immiscibility. Carbonate-bearing mantle xenoliths from Oldoinyo Lengai (East African Rift), the only active volcano erupting carbonatites, have provided key support for a C-rich mantle source. Here, we report unique microscale O and C isotopic analyses of those carbonates, which are present as interstitial grains in the silicate host lava, veins in the xenoliths, and pseudo-inclusions in olivine xenoliths. The $delta$18O values vary little, from 19texttenthousand to 29texttenthousand, whereas $delta$13C values are more variable, ranging from --23texttenthousand to +0.5texttenthousand. We show that such carbonate $delta$18O values result from the low-temperature precipitation of carbonate in equilibrium with meteoric water, rather than under mantle conditions. In this framework, the observed $delta$13C values can be reproduced by Rayleigh distillation driven by carbonate precipitation and associated degassing. Together with petrological evidence of a physical connection between the three types of carbonates, our isotopic data support the pedogenic formation of carbonates in the studied xenoliths by soil-water percolation and protracted crystallization along xenolith cracks. Our results refute a mechanism of C enrichment in the form of mantle carbonates in the mantle beneath the Natron Lake magmatic province and instead support carbonatite formation by low-degree partial melting of a C-poor mantle and subsequent protracted differentiation of alkaline magmas.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gou_etal2020,

title = {Seasonal riverine barium isotopic variation in the middle Yellow River : Sources and fractionation},

author = {L. F. Gou and A. Galy and Y. Z. Gong and X. Y. Nuan and C. Jin and X. D. Wang and J. Bouchez and H. M. Cai and J. B. Chen and H. M. Yu and F. Huang},

doi = {10.1016/j.epsl.2019.115990},

year  = {2020},

date = {2020-01-01},

journal = {Earth and Planetary Science Letters},

volume = {531},

pages = {115990},

abstract = {Barium (Ba) isotopes have been used to trace water mass mixing and export productivity in the oceans. However, the sources, isotopic signature and seasonal variation of dissolved Ba in large rivers remain poorly constrained. In order to improve our understanding of sources and fractionation of riverine Ba isotopes at the continental scale, weekly sampling of river water was carried out in the middle Yellow River over the full hydrological year of 2013. Dissolved Ba was mainly sourced from silicate dissolution, whose flux was correlated with physical erosion rate in this arid to semi-arid basin, largely covered by loess. More than half of the annual dissolved Ba flux was transported during the monsoon season (June to mid-September), in particular during a storm event period (accounting for 4% of the annual dissolved Ba flux in 4 days). The dissolved Ba isotopic composition ($delta$138Barw) ranged from +0.17texttenthousand to +0.46texttenthousand, all higher than $delta$138Ba of loess (0.00 textpm 0.04texttenthousand). The seasonal variation in $delta$138Barw is best explained via an adsorption model of light Ba isotopes onto solids in the river, which is sensitive to erosion of loess, in particular during the storm event and the spring-time ice melting intervals, with a potential role of barite precipitation in groundwater during the dry seasons. With one to three orders of magnitude higher particulate matter fluxes during the monsoon seasons in rivers such as the Yellow River, desorption of Ba could result an unaccounted strong variation of Ba concentration and isotopic composition in coastal environments, which further study requires.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Han_etal2020,

title = {Climate transition in the Asia inland at 0.8--0.6 Ma related to astronomically forced ice sheet expansion},

author = {W. Han and E. Appel and A. Galy and W. R\"{o}sler and X. Fang and X. Zhu and J. Vandenberghe and J. Wang and A. Berger and S. L\"{u} and T. Zhang},

doi = {10.1016/j.quascirev.2020.106580},

year  = {2020},

date = {2020-01-01},

journal = {Quaternary Science Reviews},

volume = {248},

pages = {106580},

abstract = {Knowing the evolution history of the climate systems in the Asian inland dominated by either the Westerlies or the Asian monsoon, and understanding their associated driving mechanisms are crucial for assessing future trends of climate and environmental conditions in this region, but both the evolution and mechanisms are still under debate. In this study, we present a comparative analysis of massive data from an accurately dated drill core retrieved from the Westerlies controlled western Qaidam Basin (QB), with records from the Chinese Loess Plateau (CLP) dominated by the East Asia summer monsoon (EASM), to track the time and frequency domain evolution patterns and dynamic changes of the QB and the CLP systems. The results infer two main conclusions. First, a critical transition in the evolution of Qaidam paleolake occurred at 0.8--0.6 Ma, characterized by striking changes in proxy variations and a system shift from periodic variations to more irregular fluctuations after 0.6 Ma. Second, a similar evolution pattern prevailed in the Qaidam paleolake region and in the EASM-dominated CLP between �`u2.7 and �`u1.2 Ma, but a divergence of both systems started at �`u1.2 Ma and fully established after 0.6 Ma, when largely fluctuating climate conditions in the QB with a distinct drying trend was accompanied by synchronous largely fluctuated EASM with an increasing trend after 0.6 Ma. We suggest that ice sheet expansion in the Northern Hemisphere, promoted by co-occurrence of low obliquity amplitudes and low eccentricity, drove both systems across a threshold at �`u1.2 Ma, and the internal forcing due to glaciation disturbed the previous response of both systems to solar insolation and led to the divergence of two systems. At �`u0.9--0.8 Ma, a node of the 1.2-Myr obliquity cycle co-occurred with an eccentricity minimum, which together with coeval decrease in atmospheric CO2 concentration, could have facilitated a striking expansion of ice sheets. The resulting more equatorial and zonally oriented northern hemisphere westerly jet could serve as key factor leading to the final collapse of Qaidam paleolake after �`u0.6 Ma, and the divergence of the QB and the CLP systems.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Huyghe_etal2020,

title = {Rapid exhumation since at least 13 Ma in the Himalaya recorded by detrital apatite fission-track dating of Bengal fan (IODP Expedition 354) and modern Himalayan river sediments},

author = {P. Huyghe and M. Bernet and A. Galy and M. Naylor and J. Cruz and B. R. Gyawali and L. Gemignani and J. L. Mugnier},

doi = {10.1016/j.epsl.2020.116078},

year  = {2020},

date = {2020-01-01},

journal = {Earth and Planetary Science Letters},

volume = {534},

pages = {116078},

abstract = {Apatite fission-track analysis of middle Bengal fan sediments (IODP expedition 354) and modern Himalayan river sediments shows that most of the detrital apatites are very young compared to their depositional ages, independent of their uranium content. Bengal fan apatites display an average central age lag time as short asMyr since at least �`u13 Ma. Such lag times reflect a mean exhumation rate on the order of at least 1-3 km/Myr. The occurrence of detrital apatites with relatively short AFT lag times since at least 13 Ma indicates that there have always been areas of rapid erosional exhumation, supplying detrital apatites to the fluvial system and delivering them to the paleo-Ganges and/or --Brahmaputra plains and finally to the Bengal fan. It also supports that temporary storage of detrital apatites in the floodplains or delta has always been negligible since at least 13 Ma. Comparison of the AFT data of the Bengal fan with those of the Central and Eastern proximal Neogene Himalayan foreland basin shows that both paleo-Ganga and --Brahmaputra catchments provided apatites with similar short lag time to the distal Bengal Fan basin.In the modern drainage system of the Bengal fan, the apatites with young fission-track cooling ages are principally derived from areas where the topography has a sharp relief controlled by threshold hillslope processes and stream power resulting in landslide erosion as a coupled response to tectonic and fluvial forcing. By analogy with the modern erosion processes in the Himalayan range, we suggest that over the past 13 Ma, apatites were mainly derived from areas of sharp relief, where river stream power was high and hill slopes close to the threshold angle. As the exhumation signal is rather consistent since the late Miocene the detrital apatite fission-track data are either not sensitive enough to detect rapid climatically controlled changes in exhumation rates, or overall long-term erosion rates on the orogen scale are not strongly affected by climatic variations such as the variability of the Indian Summer Monsoon. Given the already rapid exhumation rates controlled by tectonics, the impact of climate variability on surface erosion rates cannot be detected with our data, especially in the case of erosion processes dominated by threshold hillslope model.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Song_etal2020,

title = {Miocene 87Sr/86Sr ratios of ostracods in the northern Qaidam Basin, NE Tibetan Plateau, and links with regional provenance, weathering and eolian input},

author = {B. Song and Y. Yang and R. Yang and A. Galy and K. Zhang and J. Ji and Y. Liu and C. Ai and C. Wang and Y. Hou},

doi = {10.1016/j.palaeo.2020.109775},

year  = {2020},

date = {2020-01-01},

journal = {Palaeogeography, Palaeoclimatology, Palaeoecology},

volume = {158},

pages = {109775},

abstract = {Late Cenozoic changes in chemical weathering and the dust cycle in response to the regional aridification and global cooling in the tectonically active northern Tibetan Plateau is an intriguing issue, although it remains poorly understood. The change in the 87Sr/86Sr ratio of basin water is linked to variations in the overall input of various Sr sources with different 87Sr/86Sr ratios, and analyses of such changes can be a useful tool for revealing changes in regional lithology, weathering regimes and the dust cycle linked to tectonics and climate. In this study, we collected fossil shells of ostracods and gastropods from the Miocene Dahonggou section to reconstruct the paleolake water 87Sr/86Sr ratio from 14.8 Ma to 11.1 Ma in the northern Qaidam Basin on the northeastern Tibetan Plateau. The reconstructed paleolake water 87Sr/86Sr ratios based on fossil shells and bulk carbonates from sediments display a coincident and stable 87Sr/86Sr ratio of approximately 0.7115, which did not show any detectable change in response to the enhanced aridification since textasciitilde13 Ma as inferred by the ostracod assemblage and its stable carbon and oxygen isotopes. The results indicate that the Sr influx regime from various sources did not change significantly during the aridification processes textasciitilde13 Ma, which may have been caused by a less detectable change in proportion of silicate versus carbonate weathering, and/or an overwhelming Sr source (e.g., extrabasinal eolian dust) that occurred from 14.8 Ma to 11.1 Ma. Further, the 87Sr/86Sr ratios of modern lake water and river sand carbonates in the study region are significantly higher, approximately �W0.001, than those of the Miocene lake water. This observation can be explained by two possible mechanisms that need to be tested in the future: 1) given a Miocene Sr input regime that is similar to today, a large contribution from some extrabasinal Sr source (e.g., eolian dust) with a much lower 87Sr/86Sr ratio is expected to have prevailed from 14.8 Ma to 11.1 Ma but is absent in the modern setting or 2) given a Miocene Sr input regime that could yield an overall lower lake water 87Sr/86Sr ratio of approximately 0.7115, a significant increase in the 87Sr/86Sr ratio of catchment-scale Sr source may have occurred after 11 Ma in response to the uplift of the Qilian Mountains, which would have enhanced hydrothermal activity, metamorphism, glaciation and landslide processes, thereby resulting in more-radiogenic Sr source. Our study suggests that reconstructions of river/lake water 87Sr/86Sr ratios can place powerful constraints on the complex interactions among tectonics, climate and landscape evolution in the northeastern Tibetan Plateau based on a new perspective.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Sparkes_etal2020,

title = {Survival of graphitized petrogenic organic carbon through multiple erosional cycles},

author = {R. B. Sparkes and N. Hovius and A. Galy and J. T. Liu},

doi = {10.1016/j.epsl.2019.115992},

year  = {2020},

date = {2020-01-01},

journal = {Earth and Planetary Science Letters},

volume = {531},

pages = {115992},

abstract = {Graphite forms the endpoint for organic carbon metamorphism ; it is extremely resilient to physical, biological and chemical degradation. Carbonaceous materials (CM) contained within sediments, collected across Taiwan and from the Gaoping submarine canyon, were analyzed using Raman spectroscopy to determine the crystallinity. This allowed the erosional and orogenic movements of petrogenic organic carbon (OCpetro) during the Taiwanese orogeny to be deduced. After automatically fitting and classifying spectra, the distribution of four groups of CM within the sediments provides evidence that many forms of OCpetro have survived at least one previous cycle of erosion, transport and burial before forming rocks in the Western Foothills of the island. There is extensive detrital graphite present in rocks that have not experienced high-grade metamorphism, and graphite flakes are also found in recently deposited marine sediments off Taiwan. The tectonic and geological history of the island shows that these graphite flakes must have survived at least three episodes of recycling. Therefore, transformation to graphite during burial and orogeny is a mechanism for stabilizing organic carbon over geological time, removing biospheric carbon from the active carbon cycle and protecting it from oxidation during future erosion events.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Fang_etal2019,

title = {Paleogene global cooling--induced temperature feedback on chemical weathering, as recorded in the northern Tibetan Plateau},

author = {X. Fang and A. Galy and Y. Yang and W. Zhang and C. Ye and C. Song},

doi = {10.1130/G46422.1},

year  = {2019},

date = {2019-01-01},

journal = {Geology},

volume = {47},

number = {10},

pages = {992--996},

abstract = {Plate-tectonic processes have long been thought to be the major cause of the Cenozoic global carbon cycle, and global cooling by uplift of the Tibetan Plateau through enhancing silicate weathering and organic carbon burial and/or by weathering of obducted ophiolites during the closure of the Neo-Tethys Ocean. However, the imbalance resulting from accelerated CO2 consumption and a relatively stable CO2 input from volcanic degassing during the Cenozoic should have depleted atmospheric CO2 within a few million years; therefore, a negative feedback mechanism must have stabilized the carbon cycle. Here, we present the first almost-complete Paleogene silicate weathering intensity (SWI) records from continental rocks in the northern Tibetan Plateau showing that silicate weathering in this tectonically inactive area was modulated by global temperature. These findings suggest that Paleogene global cooling was also strongly influenced by a temperature feedback mechanism, which regulated silicate weathering rates and hydrological cycles and maintained a nearly stable carbon cycle. It acted as a negative feedback by decreasing CO2 consumption resulting from the lower SWI and the kinetic limitations in tectonically inactive areas.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gou_etal2019,

title = {Effects of cone combinations on accurate and precise Mg‐isotopic determination using multi‐collector inductively coupled plasma mass spectrometry},

author = {L. F. Gou and Z. Jin and A. Galy and H. Sun and L. Deng and Y. Xu},

doi = {10.1002/rcm.8356},

year  = {2019},

date = {2019-01-01},

journal = {Rapid Communications in Mass Spectrometry},

volume = {33},

pages = {351--360},

abstract = {RationaleHigh‐precision determination of magnesium (Mg) isotopes can now be routinely achieved by multi‐collector inductively coupled plasma mass spectrometry (MC‐ICP‐MS). The analytical sensitivity and instrumental mass discrimination behavior of this method are, however, sensitive to the types of sample and skimmer cones used in these measurements, so it is important that these parameters should be investigated.MethodsUsing the sample‐standard‐bracketing method in the wet‐plasma mode, four available combinations of sample and skimmer cones [Jet sample cone + H skimmer cone (Jet + H), standard sample cone + H skimmer cone (Standard + H), standard sample cone + X skimmer cone (Standard + X), and Jet sample cone + X skimmer cone (Jet + X)] were systematically investigated for peak shape, sensitivity, mass discrimination, accuracy, and precision in Mg‐isotopic ratio determination using a Neptune plus MC‐ICP mass spectrometer.ResultsThe results showed that different cone combinations do not affect peak shapes but would significantly change the sensitivities for Mg‐isotopic determinations. Compared with using the Standard + H, the sensitivities of Mg‐isotopic determinations were enhanced by approximately a factor of 1.3, 1.4, and 1.9 by using the Standard + X, the Jet + H, and the Jet + X combinations, with the most stable mass discrimination behaviors obtained by the Jet + H. The instrumental mass fractionation slope for any combination of a modified cone geometry (i.e. Standard + X, Jet + X, and Jet + H) is 0.500, while it is 0.510 for the Standard + H. In addition, the mass discrimination behavior is related to Mg concentrations once the combination is set, indicating the necessity of concentration match during Mg‐isotopic determination.ConclusionsThe precision and accuracy of the Jet + H combination are better than those of the other combinations, and this is further supported by the validation of the Mg‐isotope data for four international reference materials: Cambridge‐1, NASS‐6, AGV‐2, and BHVO‐2. As the Jet + H combination also provides a high signal, this combination gives the most robust strategy for the highly precise and accurate determination of Mg isotopes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gou_etal2019_2,

title = {Li isotopes in the middle Yellow River: Seasonal variability, sources and fractionation},

author = {L. F. Gou and Z. Jin and P. A. E. Pogge von Strandmann and G. Li and Y. X. Qu and J. Xiao and L. Deng and A. Galy},

doi = {10.1016/j.gca.2019.01.007},

year  = {2019},

date = {2019-01-01},

journal = {Geochimica et Cosmochimica Acta},

volume = {248},

pages = {88--108},

abstract = {To evaluate the roles of climate and hydrology in continental-scale silicate weathering, we applied Li isotopes to the Yellow River and systematically investigated seasonal Li flux, Li isotopic compositions and potential sources. We collected samples from the middle reaches of the Yellow River weekly over the full hydrological year of 2013. We find that the dissolved Li is mainly derived from silicates and evaporites in the arid to semi-arid Yellow River basin. Silicate weathering of loess during the monsoonal season dominates the Li flux in the middle reaches of the Yellow River, with a positive relationship between dissolved Li flux and physical erosion rate. Evaporite contribution for riverine Li was relatively constant in the middle reaches of the Yellow River but slightly increased after the storm event, with an average proportion of �`u25%, which might represent the proportion of evaporite contribution to global oceans. Seasonal variations in the riverine Li isotopic compositions are dominantly controlled by temperature with a fractionation gradient as −0.182texttenthousand per textdegreeC over the full year with deviations likely driven by re-dissolution of suspended particulate matter, extreme hydrological events, and groundwater contribution. Temperature dependent $delta$7Li value variation of river water inputted into oceans indicates that Cenozoic climate cooling itself may be able to explain �`u2texttenthousand of the 9texttenthousand rise of Cenozoic seawater $delta$7Li value (Misra and Froelich, 2012). The seasonal variation in riverine Li isotopes highlights that erosion and weathering of loess may provide valuable clues on secular chemical weathering and seawater $delta$7Li variation spanning a range of time scales.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Lee_etal2019,

title = {Sustained wood burial in the Bengal Fan over the last 19 My},

author = {H. Lee and V. Galy and X. Feng and C. Ponton and A. Galy and C. France-Lanord and S. J. Feakins},

doi = {10.1073/pnas.1913714116},

year  = {2019},

date = {2019-01-01},

journal = {Proceedings of the National Academy of Sciences},

volume = {116},

number = {45},

pages = {22518--22525},

abstract = {The Ganges--Brahmaputra (G-B) River system transports over a billion tons of sediment every year from the Himalayan Mountains to the Bay of Bengal and has built the worldtextquoterights largest active sedimentary deposit, the Bengal Fan. High sedimentation rates drive exceptional organic matter preservation that represents a long-term sink for atmospheric CO2. While much attention has been paid to organic-rich fine sediments, coarse sediments have generally been overlooked as a locus of organic carbon (OC) burial. However, International Ocean Discovery Program Expedition 354 recently discovered abundant woody debris (millimeter- to centimeter-sized fragments) preserved within the coarse sediment layers of turbidite beds recovered from 6 marine drill sites along a transect across the Bengal Fan (�`u8textdegreeN, �`u3,700-m water depth) with recovery spanning 19 My. Analysis of bulk wood and lignin finds mostly lowland origins of wood delivered episodically. In the last 5 My, export included C4 plants, implying that coarse woody, lowland export continued after C4 grassland expansion, albeit in reduced amounts. Substantial export of coarse woody debris in the last 1 My included one wood-rich deposit (�`u0.05 Ma) that encompassed coniferous wood transported from the headwaters. In coarse layers, we found on average 0.16 weight % OC, which is half the typical biospheric OC content of sediments exported by the modern G-B Rivers. Wood burial estimates are hampered by poor drilling recovery of sands. However, high-magnitude, low-frequency wood export events are shown to be a key mechanism for C burial in turbidites.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ruan_etal2019,

title = {Evidence for early (�W12.7 Ma) eolian dust impact on river chemistry in the northeastern Tibetan Plateau},

author = {X. Ruan and Y. Yang and A. Galy and X. Fang and Z. Jin and F. Zhang and R. Yang and L. Deng and Q. Meng and C. Ye and W. Zhang},

doi = {10.1016/j.epsl.2019.03.022},

year  = {2019},

date = {2019-01-01},

journal = {Earth and Planetary Science Letters},

volume = {515},

pages = {79--89},

abstract = {As one of the largest dust sources on the Earthtextquoterights surface, dryland in Central Asia gives rise to thick eolian deposits over East Asia (e.g., the Chinese Loess Plateau, CLP) and significantly influences the regional hydrochemistry in the downwind drainage areas. However, the formation of thick eolian dust deposits requires not only climatic prerequisites for dust emission and transport but also climatic and topographic conditions favourable for deposition and accumulation. The scarcity of widespread eolian deposition around the CLP before 7-8 Ma hinders a full understanding of the processes and mechanisms of Central Asian aridification. The deposition of eolian dust also impacts the hydrogeochemistry of fluvial systems and the precipitation of authigenic phases in continental sedimentary systems could be an archive for studying eolian dust dynamics when pure eolian deposits are scarce. Here, we present the Ca-Mg-Sr concentrations and 87Sr/86Sr isotope compositions of bulk carbonates in a new fluvial sequence (12.7-4.8 Ma) of the Xining Basin. The Mg/Ca and Sr/Ca ratios of the carbonate describe a power law relationship with a power coefficient of �`u0.8, lower than the coefficient characteristic of prior calcite precipitation (PCP). An input of eolian dust with the dissolution of Mg-rich carbonate is likely responsible for the deviation from a pure PCP process. The bulk carbonates also show a general decrease of 87Sr/86Sr ratios from 12.7 to 4.8 Ma, with a transition around 8.6 Ma revealed by lower Sr/Mg ratios. The comparison of these proxies to a previously reported fluvial section (12.2-5.1 Ma) in the Linxia Basin, �`u200 km to the southeast, shows that the 87Sr/86Sr ratios of the bulk carbonates and water-soluble salts in the Linxia Basin are around 0.7098, which is 0.0018 lower than those in the Xining Basin before 8.6 Ma, but shows a significant rise between 8.6 and 7.0 Ma. The two basins share the same range of carbonate 87Sr/86Sr ratios when sediments are younger than 7 Ma. For the last 7 Myrs, the evolution of the 87Sr/86Sr ratios in bulk carbonates of fluvial sediments and Pliocene-Quaternary eolian deposits found in the Xining Basin are similar to those in typical eolian red clays/loess-palaeosol sequences on the CLP. These results suggest a transition of the hydrochemical regime at 8.6 Ma in the Linxia Basin from a catchment only influenced by the weathering of its bedrock to one significantly impacted by eolian dust input. In the Xining Basin, the carbonate elemental and 87Sr/86Sr ratios are consistent with a hydrochemistry more impacted by the presence of the eolian dust. There, the dust input occurred earlier, at �W12.7 Ma, though it has strengthened since 8.6 Ma. The eolian dust impact on fluvial systems in the Xining Basin was much earlier than in the Linxia Basin and also preceded the initial accumulation of widespread eolian red clays on the CLP (7-8 Ma), suggesting a temporally propagating and spatially stepwise expansion of eolian dust delivery across the Asian inland during the late Cenozoic.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Yang_etal2019,

title = {Late miocene intensified tectonic uplift and climatic aridification on the northeastern Tibetan plateau: Evidence from clay mineralogical and geochemical records in the Xining Basin},

author = {R. Yang and Y. Yang and X. Fang and X. Ruan and A. Galy and C. Ye and Q. Meng and W. Han},

doi = {10.1029/2018GC007917},

year  = {2019},

date = {2019-01-01},

journal = {Geochemistry Geophysics Geosystems G3},

volume = {20},

number = {2},

pages = {829--851},

abstract = {The uplift of the Tibetan Plateau (TP) during the late Cenozoic is thought to be one of crucial factors controlling Asian climate. However, the complex interaction between tectonics and climate change is still unclear. Here we present the first record of clay mineralogy and elemental geochemistry covering textasciitilde12.7--4.8 Ma in a fluvial‐lacustrine sequence in the Xining Basin. Geochemical provenance proxies (Th/Sc, Zr/Sc, and Cr/Zr) in the \<2‐$mu$m fraction show a significant provenance change at textasciitilde8.8 Ma. Silicate‐based weathering indexes (CIA, CIW, and PIA) displayed coeval changes with provenance but discrepant changes with regional climate. Since the clay mineralogy exhibits significant change at textasciitilde7.8 Ma uncorrelated with modifications in provenance, it can be employed to reveal regional climate change. The rise in illite and associated decrease in the sum of smectite and illite/smectite mixed layers reflect gradual and slow aridification since textasciitilde12.7 Ma with intensified drying since textasciitilde7.8 Ma until approaching the modern climate status. Our results, together with other regional climatic and tectonic records, clearly illustrate that accelerated uplift of the northeastern TP since textasciitilde8--9 Ma has mainly modulated the regional erosion, weathering, transportation, and sedimentation and amplified the global cooling and drying trend toward the regional climate of modern conditions. Our study suggests that in the tectonically active northeastern TP, a comprehensive mineralogical and geochemical investigation of the fine‐grained fraction of the basin sediments could retrieve the interactions between tectonics and climate behind the complex change in exhumed lithology and sedimentary routing systems.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bickle_etal2018,

title = {Chemical weathering outputs from the flood plain of the Ganga},

author = {M. J. Bickle and H. J. Chapman and E. Tipper and A. Galy and C. De La Rocha and T. Ahmad},

doi = {10.1016/j.gca.2018.01.003},

year  = {2018},

date = {2018-01-01},

journal = {Geochimica et Cosmochimica Acta},

volume = {225},

pages = {146--175},

abstract = {Transport of sediment across riverine flood plains contributes a significant but poorly constrained fraction of the total chemical weathering fluxes from rapidly eroding mountain belts which has important implications for chemical fluxes to the oceans and the impact of orogens on long term climate. We report water and bedload chemical analyses from the Ganges flood-plain, a major transit reservoir of sediment from the Himalayan orogen. Our data comprise six major southern tributaries to the Ganga, 31 additional analyses of major rivers from the Himalayan front in Nepal, 79 samples of the Ganga collected close to the mouth below the Farakka barrage every two weeks over three years and 67 water and 8 bedload samples from tributaries confined to the Ganga flood plain. The flood plain tributaries are characterised by a shallow d18O ?\u{I} dD array, compared to the meteoric water line, with a low dDexcess from evaporative loss from the flood plain which is mirrored in the higher dDexcess of the mountain rivers in Nepal. The stable-isotope data confirms that the waters in the flood plain tributaries are dominantly derived from flood plain rainfall and not by redistribution of waters from the mountains. The flood plain tributaries are chemically distinct from the major Himalayan rivers. They can be divided into two groups. Tributaries from a small area around the Kosi river have 87Sr/86Sr ratios \>0.75 and molar Na/Ca ratios as high as 6. Tributaries from the rest of the flood plain have 87Sr/86Sr ratios \<-0.74 and most have Na/Ca ratios \<1. One sample of the Gomti river and seven small adjacent tributaries have elevated Na concentrations likely caused by dissolution of Na carbonate salts. The compositions of the carbonate and silicate components of the sediments were determined from sequential leaches of floodplain bedloads and these were used to partition the dissolved cation load between silicate and carbonate sources. The 87Sr/86Sr and Sr/Ca ratios of the carbonate inputs were derived from the acetic-acid leach compositions and silicate Na/Ca and 87Sr/86Sr ratios derived from silicate residues from leaching. Modelling based on the 87Sr/86Sr and Sr/Ca ratios of the carbonate inputs and 87Sr/86Sr ratios of the silicates indicates that the flood plain waters have lost up to 70% of their Ca (average 50%) to precipitation of secondary calcite which is abundant as a diagenetic cement in the flood plain sediments. 31% of the Sr, 8% of the Ca and 45% of the Mg are calculated to be derived from silicate minerals. Because of significant evaporative loss of water across the flood plain, and in the absence of hydrological data for flood plain tributaries, chemical weathering fluxes from the flood plain are best calculated by mass balance of the Na, K, Ca, Mg, Sr, SO4 and 87Sr/86Sr compositions of the inputs, comprising the flood plain tributaries, Himalayan rivers and southern rivers, with the chemical discharge in the Ganga at Farakka. The calculated fluxes from the flood plain for Na, K, Ca and Mg are within error of those estimated from changes in sediment chemistry across the flood plain (Lupker et al., 2012, Geochemica Cosmochimica Acta). Flood plain weathering supplies between 41 and 63% of the major cation and Sr fluxes and 58% of the alkalinity flux carried by the Ganga at Farakka which compares with 24% supplied by Himalayan rivers and 18% by the southern tributaries.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Emberson_etal2018,

title = {Weathering of reactive mineral phases in landslides acts as a source of carbon dioxide in mountain belts},

author = {R. Emberson and A. Galy and N. Hovius},

doi = {10.1029/2018JF004672},

year  = {2018},

date = {2018-01-01},

journal = {Journal of Geophysical Research ?\u{I} Earth Surface},

volume = {123},

pages = {2695--2713},

abstract = {Bedrock landsliding in mountain belts can elevate overall chemical weathering rates through rapid dissolution of exhumed reactive mineral phases in transiently stored deposits. This link between a key process of erosion and the resultant weathering affects the sequestering of carbon dioxide through weathering of silicate minerals and broader links between erosion in active orogens and climate change. Here we address the effect on the carbon cycle of weathering induced by bedrock landsliding in Taiwan and the Western Southern Alps of New Zealand. Using solute chemistry data from samples of seepage from landslide deposits and river discharge from catchments with variable proportions of landsliding, we model the proportion of silicate and carbonate weathering and the balance of sulfuric and carbonic acids that act as weathering agents. We correct for secondary precipitation, geothermal, and cyclic input, to find a closer approximation of the weathering explicitly occurring within landslide deposits. We find highly variable proportions of sulfuric and carbonic acids driving weathering in landslides and stable hillslopes. Despite this variability, the predominance of rapid carbonate weathering within landslides and catchments where mass wasting is prevalent results at best in limited sequestration of carbon dioxide by this process of rapid erosion. In many cases where sulfuric acid is a key weathering agent, a net release of CO2 to the atmosphere occurs. This suggests that a causal link between erosion in mountain belts and climate change through the sequestration of CO2, if it exists, must operate through a process other than chemical weathering driven by landsliding.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Schulze-Makuch_etal2018,

title = {Transitory microbial habitat in the hyperarid Atacama Desert},

author = {D. Schulze-Makuch and D. Wagner and S. Kounaves and K. Mangelsdorf and K. G. Devine and J. P. Vera and P. Schmitt-Kopplin and H. P. Grossart and V. Parro and M. Kaupenjohann and A. Galy and al},

doi = {10.1073/pnas.1714341115},

year  = {2018},

date = {2018-01-01},

journal = {PNAS},

abstract = {Traces of life are nearly ubiquitous on Earth. However, a central unresolved question is whether these traces always indicate an active microbial community or whether, in extreme environments, such as hyperarid deserts, they instead reflect just dormant or dead cells. Although microbial biomass and diversity decrease with increasing aridity in the Atacama Desert, we provide multiple lines of evidence for the presence of an at times metabolically active, microbial community in one of the driest places on Earth. We base this observation on four major lines of evidence: (i) a physico-chemical characterization of the soil habitability after an exceptional rain event, (ii) identified biomolecules indicative of potentially active cells [e.g., presence of ATP, phospholipid fatty acids (PLFAs), metabolites, and enzymatic activity], (iii) measurements of in situ replication rates of genomes of uncultivated bacteria reconstructed from selected samples, and (iv) microbial community patterns specific to soil parameters and depths. We infer that the microbial populations have undergone selection and adaptation in response to their specific soil microenvironment and in particular to the degree of aridity. Collectively, our results highlight that even the hyperarid Atacama Desert can provide a habitable environment for microorganisms that allows them to become metabolically active following an episodic increase in moisture and that once it decreases, so does the activity of the microbiota. These results have implications for the prospect of life on other planets such as Mars, which has transitioned from an earlier wetter environment to todaytextquoterights extreme hyperaridity.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bickle_etal2017,

title = {Rapid reactions between CO2, brine and silicate minerals during geological carbon storage: Modelling based on a field CO2 injection experiment},

author = {M. Bickle and N. Kampman and H. Chapman and C. Ballentine and B. Dubacq and A. Galy and T. Sirikitputtisak and O. Warr and and M. Wigley and Z. Zhou},

doi = {10.1016/j.chemgeo.2017.07.031},

year  = {2017},

date = {2017-01-01},

journal = {Chemical Geology},

volume = {468},

pages = {17--31},

abstract = {The dissolution of CO2 into formation brines and the subsequent reactions of the CO2-charged brines with reservoir minerals are two key processes likely to increase the security of geological carbon-dioxide storage. These processes will be dependent on the permeability structure and mineral compositions of the reservoirs, but there is limited observational data on their rates. In this paper we report the cation and anion concentrations and Sr, oxygen and carbon isotopic compositions of formation waters from four extraction wells sampled at surface,over textasciitilde6 months after commencement of CO2 injection in a five spot pattern for enhanced oil recovery at the Salt Creek field, Wyoming. Sampled fluids, separated from the minor oil component, exhibit near-monotonic increases in alkalinity and concentrations of cations but little change in Cl and Br concentrations and oxygen and deuterium isotope ratios. The increases in alkalinity are modelled in terms of reaction with reservoir calcite and silicate minerals as the changes in fluid chemistry and Sr-isotopic compositions are inconsistent with simple addition of injected fluids sampled over the course of the experiment. The reservoir mineral chemical and isotopic compositions are characterised by sampling core as well as surface exposures of the Frontier Formation elsewhere in Wyoming. The evolution of the fluid chemistries reflects extensive dissolution of both carbonateand silicate minerals over the course of the six months sampling implying rapid dissolution of CO2 in the formation waters and reaction of CO2-bearing brines with formation minerals. Rates of CO2 diffusion into the brines and advection of CO2 charged brines in the reservoir are sufficiently slow that, if present, calcite should react to be close to equilibrium with the fluids. This allows estimation of the CO2 partial pressures in the sampled fluids and comparison with the thermodynamic driving force for the relatively rapid average plagioclase dissolution rates of textasciitilde10−12 moltextperiodcenteredm−2textperiodcentereds−1.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Emberson_etal2017,

title = {Combined effect of carbonate and biotite dissolution in landslides biases silicate weathering proxies},

author = {R. Emberson and A. Galy and N. Hovius},

doi = {10.1016/j.gca.2017.07.014},

year  = {2017},

date = {2017-01-01},

journal = {Geochimica et Cosmochimica Acta},

volume = {213},

pages = {418--434},

abstract = {Long-term estimates of the dissolution of silicate rock are generally derived from a range of isotopic proxies, such as the radiogenic strontium isotope ratio (87Sr/86Sr), which are preserved in sediment archives. For these systems to fairly represent silicate weathering, the changes in isotopic ratios in terrestrial surface waters should correspond to changes in the overall silicate dissolution. This assumes that the silicate mineral phases that act as sources of a given isotope dissolve at a rate that is proportional to the overall silicate weathering. Bedrock landsliding exhumes large quantities of fresh rock for weathering in transient storage, and rapid weathering in these deposits is controlled primarily by dissolution of the most reactive phases. Inthis study, we test the hypothesis that preferential weathering of these labile minerals can decouple the dissolution of strontium sources from the actual silicate weathering rates in the rapidly eroding Western Southern Alps (WSA) of New Zealand. We find that rapid dissolution of relatively radiogenic calcite and biotite in landslides leads to high local fluxes in strontium with isotopic ratios that offer no clear discrimination between sources. These higher fluxes of radiogenic strontium are in contrast to silicate weathering rates in landslides that are not systematically elevated. On a mountain belt scale, radiogenic strontium fluxes are not coupled to volumes of recent landslides in large (\>100 km2) catchments, but silicate weathering fluxes are. Such decoupling is likely due first to the broad variability in the strontium content of carbonate minerals, and second to the combination of radiogenic strontium released from both biotite and carbonate in recent landslides. This study supports previous work suggesting the limited utility of strontium isotopes as a system to study silicate weathering in the WSA. Crucially however, in settings where bedrock landsliding is a dominant erosive process there is potential for both random and systematic bias in isotope proxies if the most reactive phases exposed for dissolution by landslides disproportionately contribute to the proxy of choice. This clearly suggests that the isotopic composition of marine Sr is a proxy for periods of rapid mountainuplift and erosion rather than for the associated enhanced silicate weathering.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Galy_etal2017,

title = {Sequestration of carbon as carbonate in the critical zone: insights from the Himalayas and Tibetan Plateau},

author = {A. Galy and Y. Yang and X. Fang},

doi = {10.1007/s11631-017-0170-6},

year  = {2017},

date = {2017-01-01},

journal = {Acta Geochimica},

abstract = {The carbon pool stored in soil carbonate is comparable to the soil organic carbon. Therefore, secondary calcite precipitation in supersaturated catchmentcould be an important, yet poorly constrained, carbon sink within the modern global carbon cycle. The chemical analysis of some dissolved species transported by rivers, such as elevated Sr/Ca and Mg/Ca ratios but also heavy stable Ca isotopic compositions, witness the formation of secondary calcite in rivers draining arid regions. However, in areas affected by active tectonics and rapid physical erosion, co-variations in the fluvial Sr/Ca and Mg/Ca ratioscould also be related to incongruent carbonate weathering processes. Here, we present a model to assess the roles played by incongruent carbonate dissolution and secondary calcite precipitation in modern weathering processes. We tested and applied the model to rivers draining the Himalayan--Tibetan region. The results suggest that regional aridity in the drainage basin promotes carbon sequestrationas secondary carbonate but that for a given runoff, incongruent dissolution of carbonate possibly related to rapid physical erosion amplifies such sequestration. The isotopic compositions (13C/12C and 18O/16O) of detrital carbonate transported by the main rivers in South and South-East Tibet imply that around 1% of the suspended material transported by those rivers corresponds to secondarycarbonate and can represent between 5% and 15% of the alkalinity flux. Most of these alkalinity transported as particulate material is, nevertheless related to the weathering of carbonate lithologies and is also subjected to dissolution prior its final storage in sedimentary basins. However, on glacial-interglacial timescale this will amplify the significant role of mountain weathering on climaticvariations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Hein_etal2017,

title = {Post-glacial climate forcing of surface processes in the Ganges--Brahmaputra river basin and implications for carbon sequestration},

author = {C. J. Hein and V. Galy and A. Galy and C. France-Lanord and H. Kudrass and T. Schwenk},

doi = {10.1016/j.epsl.2017.08.013},

year  = {2017},

date = {2017-01-01},

journal = {Earth and Planetary Science Letters},

volume = {478},

pages = {89--101},

abstract = {Climate has been proposed to control both the rate of terrestrial silicate weathering and the export rate of associated sediments and terrestrial organic carbon to river-dominated margins -- and thus the rate of sequestration of atmospheric CO2in the coastal ocean -- over glacial--interglacial timescales. Focused on the Ganges--Brahmaputra rivers, this study presents records of post-glacial changes in basin-scale Indian summer monsoon intensity and vegetation composition based on stable hydrogen ($delta$D) and carbon ($delta$13C) isotopic compositions of terrestrial plant wax compounds preserved in the channel--levee system of the Bengal Fan. It then explores the role of these changes in controlling the provenance and degree of chemical weathering of sediments exported by these rivers, and the potential climate feedbacks through organic-carbon burial in the Bengal Fan. An observed 40-shift in $delta$D and a 3--4-shift in both bulk organic-carbon and plant-wax $delta$13C values between the late glacial and mid-Holocene, followed by a return to more intermediate values during the late Holocene, correlates well with regional post-glacial paleoclimate records. Sediment provenance proxies (Sr, Nd isotopic compositions) reveal that these changes likely coincided with a subtle focusing of erosion on the southern flank of the Himalayan range during periods of greater monsoon strength and enhanced sediment discharge. However, grain-size-normalized organic-carbon concentrations in the Bengal Fan remained constant through time, despite order-of-magnitude level changes in catchment-scale monsoon precipitation and enhanced chemical weathering (recorded as a gradual increase in K/Si∗and detrital carbonate content, and decrease in H2O+/Si∗, proxies) throughout the study period. These findings demonstrate a partial decoupling of climate change and silicate weathering during the Holocene and that marine organic-carbon sequestration rates primary reflect rates of physical erosion and sediment export as modulated by climatic changes. Together, these results reveal the magnitude of climate changes within the Ganges--Brahmaputra basin following deglaciation and a closer coupling of monsoon strength with OC burial than with silicate weathering on millennial timescales.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kitayama_etal2017,

title = {Co-magmatic sulfides and sulfates in the Udachnaya-East pipe (Siberia): A record of the redox state and isotopic composition of sulfur in kimberlites and their mantle sources},

author = {Y. Kitayama and E. Thomassot and A. Galy and A. Golovin and A. Korsakov and E. DtextquoterightEyrames and N. Assayag and N. Bouden and D. Ionov},

doi = {10.1016/j.chemgeo.2016.10.037},

year  = {2017},

date = {2017-01-01},

journal = {Chemical Geology},

volume = {455},

pages = {315--330},

abstract = {Kimberlites of the Udachnaya-East pipe (Siberia) include a uniquely dry and serpentine-free rock type with anomalously high contents of chlorine (Cl ≤ 6.1 wt%), alkalies (Na2O + K2O ≤ 10 wt%) and sulfur (S ≤ 0.50 wt%), referred to as a textquotelefttextquoteleftsaltytextquoterighttextquoteright kimberlite. The straightforward interpretation is that the Na-, K-, Cl- and S-rich components originate directly from a carbonate-chloride kimberlitic magma that is anhydrous and alkali-rich. However, because brines and evaporites are present on the Siberian craton, previous studies proposed that the kimberlitic magma was contaminated by the assimilation of salt-rich crustal rocks. To clarify the origin of high Cl, alkalies and S in this unusual kimberlite, here we determine its sulfur speciation and isotopic composition and compare it to that of non-salty kimberlites and kimberlitic breccia from the same pipe, as well as potential contamination sources (hydrothermal sulfides and sulfates, country-rock sediment and brine collected in the area). The average $delta$34S of sulfides is−1.4 textpm 2.2texttenthousand in the salty kimberlite, 2.1 textpm 2.7texttenthousand in the non-salty kimberlites and 14.2 textpm 5.8texttenthousand in the breccia. The average $delta$34S of sulfates in the salty kimberlites is 11.1 textpm 1.8texttenthousand and 27.3textpm 1.6texttenthousand in the breccia. In contrast, the $delta$34S of potential contaminants range from 20 to 42texttenthousand for hydrothermal sulfides, from 16 to 34texttenthousand for hydrothermal sulfates, 34texttenthousand for a country-rock sediment (Chukuck suite) and the regional brine aquifer. Our isotope analyses show that (1) in the salty kimberlites, neither sulfates nor sulfides can be simply explained by brine infiltration, hydrothermal alteration or the assimilation of known salt-rich country rocks and instead, we propose that they are late magmatic phases ; (2) in the non-salty kimberlite and breccia, brine infiltration lead to sulfate reduction and the formation of secondary sulfides -- this explains the removal of salts, alkali-carbonates and sulfates, as well as theminor olivine serpentinization ; (3) hydrothermal sulfur was added to the kimberlitic breccia, but not to the massive kimberlites. In situ measurements of sulfides confirm this scenario, clearly showing the addition of two sulfide populations in the breccia (pyrite-pyrrhotites with average $delta$34S of 7.9 textpm 3.4texttenthousand and chalcopyrites with average $delta$34S of 38.0 textpm 0.4texttenthousand) whereas the salty and non-salty kimberlites preserve a unique population of djerfisherites (Cl- and K-rich sulfides) with $delta$34S values within themantle range. This study provides the first direct evidence of alkaline igneous rocks in which magmatic sulfate ismore abundant than sulfide. Although sulfates have been rarely reported in mantle materials, sulfate rich melts may be more common in the mantle than previously thought and could balance the sulfur isotope budget of Earthtextquoterights mantle.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Yang_etal2017,

title = {Eolian dust forcing of river chemistry on the northeastern Tibetan Plateau since 8Ma},

author = {Y. Yang and A. Galy and X. Fang and R. Yang and W. Zhang},

doi = {10.1016/j.epsl.2017.02.009},

year  = {2017},

date = {2017-01-01},

journal = {Earth and Planetary Science Letters},

volume = {464},

pages = {200--210},

abstract = {Eolian dust is one of the most important factors controlling fluvial hydrological evolution in modern arid and semi-arid central Asia. Here, we present the bulk carbonate Ca--Mg--Sr concentrations and Sr isotopic compositions recorded in water soluble salts, carbonate and silicate fractions, as well as the Nd isotopic compositions in the silicate fraction of a Late Miocene (12.2--5.1Ma) fluvial sequence exhibiting paleosol development, in the Linxia Basin on the northeastern Tibetan Plateau (TP). Bulk carbonate Mg--Sr systematics show a distinct pattern in log--log plots of Mg/Ca versuslog Sr/Ca ratios, and clearly higher 87Sr/86Sr ratios since �`u8Ma. These findings cannot be adequately explained by the mechanism of prior calcite precipitation (PCP) -- this latter process results in a positive correlation between the Mg/Ca and Sr/Ca ratios in authigenic calcite, evident in the fixed gradient in their log--log plots and has been isolated as being the major factor controlling carbonate Mg--Sr systematics before 8 Ma. Nor can these findings be explained by other mechanisms related to the catchmenttextquoterights provenance/sedimentation. The dramatic changes in carbonate Sr contents, Sr isotopes, and Sr/Mg ratios since �`u8Ma may therefore be inferred to have been triggered by significant inputs of eolian dust viathe dissolution of dust carbonates and evaporites in the paleowaters where fluvial and paleosol carbonates precipitated. This process of eolian dust input can be reliably illustrated using a binary mixing model corresponding to a series of varying PCP fluxes (identical to processes affecting the area before 8Ma) combined with a constant eolian influx calculated from the co-variations between Mg/Ca, Sr/Ca and Sr isotopic ratios. Eolian dust also leaves a fingerprint in the carbonate and silicate minerals of bulk sediments, as revealed respectively by their Sr and Nd isotopic compositions. Eolian dust compositions for the �`u8--5Ma on the northeastern TP can thus be taken to be characterized by a $epsilon$Ndvalue ≤−10.5for the silicate fraction, and by a 87Sr/86Sr value �W0.7115 for the labile faction (carbonates and evaporites). Eolian dust is now recognized to have made a significant impact on the hydrological evolution of arid and semi-arid northern China as far back as �`u8Ma, suggesting an enhanced regime of dust activity and regional aridification in central Asia at that time.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Yang_etal2017_2,

title = {Glacial-interglacial climate change on the northeastern Tibetan Plateau over the last 600 kyr},

author = {Y. Yang and R. Yang and X. Li and W. Han and J. Zan and X. Fang and E. Appel and A. Galy and F. Wu and S. Yang and Z. Zhang and W. Zhang and C. Ye},

doi = {/10.1016/j.palaeo.2017.04.007},

year  = {2017},

date = {2017-01-01},

journal = {Palaeogeography, Palaeoclimatology, Palaeoecology},

volume = {476},

pages = {181--191},

abstract = {Exploring the interplay between the mid-latitudeWesterlies and East Asian monsoon systems is crucial for revealing the mechanisms and processes behind the aridification of the central Asian interior. In this study, a high-resolution acid-dissolvedMn record of lacustrine sediments from a drilling core (SG-1) in the arid western Qaidam Basin on the northeastern Tibetan Plateau (TP) largely reveals the evolution of lake levels and climate change over the last 600 kyr. The climate in the western Qaidam Basin shows distinct glacial and interglacialchanges in accordance with changes in the global climate, and in North Atlantic sea surface temperatures (SSTs), indicating the teleconnection between the basintextquoterights climate and the North Atlantic in the form of theWesterlies. However, the basintextquoterights climate also correlates closely with East Asian Winter Monsoon (EAWM) activity asrecorded by the grain size variations in loess-paleosol sequences on the Chinese Loess Plateau (CLP) over a glacial-interglacial timescale. Even during glacial periods, some relatively warm/humid stages accompanied by high paleolake levels in the western Qaidam Basin are generally conformable with relatively weak EAWM,whereas these warm/humid stages show a weak relation with the East Asian Summer Monsoon (EASM) and North Atlantic SSTs. These results collectively provide evidence that climate change in the western Qaidam Basin is, and was, not only controlled by the Westerlies, but also strongly influenced by the Siberian High, atleast during glacial periods. The exact driving mechanism, however, needs to be explored further in future studies.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Emberson_etal2016,

title = {Oxidation of sulfides and rapid weathering in recent landslides},

author = {R. Emberson and N. Hovius and A. Galy and O. Marc},

doi = {10.5194/esurf-4-727-2016},

year  = {2016},

date = {2016-01-01},

journal = {Earth Surface Dynamics},

volume = {4},

pages = {727--742},

abstract = {Linking together the processes of rapid physical erosion and the resultant chemical dissolution of rock is a crucial step in building an overall deterministic understanding of weathering in mountain belts. Landslides, which are the most volumetrically important geomorphic process at these high rates of erosion, can generate extremely high rates of very localised weathering. To elucidate how this process works we have taken advantage of uniquely intense landsliding, resulting from Typhoon Morakot, in the Ttextquoterightaimali River and surrounds insouthern Taiwan. Combining detailed analysis of landslide seepage chemistry with estimates of catchment-bycatchment landslide volumes, we demonstrate that in this setting the primary role of landslides is to introduce fresh, highly labile mineral phases into the surface weathering environment. There, rapid weathering is driven by the oxidation of pyrite and the resultant sulfuric-acid-driven dissolution of primarily carbonate rock. The total dissolved load correlates well with dissolved sulfate -- the chief product of this style of weathering -- inboth landslides and streams draining the area (R2 D0.841 and 0.929 respectively; p \< 0.001 in both cases), with solute chemistry in seepage from landslides and catchments affected by significant landsliding governed by the same weathering reactions. The predominance of coupled carbonate--sulfuric-acid-driven weathering is the key difference between these sites and previously studied landslides in New Zealand (Emberson et al., 2016), but in both settings increasing volumes of landslides drive greater overall solute concentrations in streams.Bedrock landslides, by excavating deep below saprolite--rock interfaces, create conditions for weathering in which all mineral phases in a lithology are initially unweathered within landslide deposits. As a result, the most labile phases dominate the weathering immediately after mobilisation and during a transient period of depletion. This mode of dissolution can strongly alter the overall output of solutes from catchments and their contribution to global chemical cycles if landslide-derived material is retained in catchments for extended periods after mass wasting.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Emberson_etal2016_2,

title = {Chemical weathering in active mountain belts controlled by stochastic bedrock landsliding},

author = {R. Emberson and N. Hovius and A. Galy and O. Marc},

year  = {2016},

date = {2016-01-01},

journal = {Nature Geoscience},

volume = {9},

number = {1},

pages = {42--45},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Yang_etal2016,

title = {Plateau uplift forcing climate change around 8.6 Ma on the northeastern Tibetan Plateau: Evidence from an integrated sedimentary Sr record},

author = {Y. Yang and X. Fang and A. Galy and Z. Jin and F. Wu and R. Yang and W. Zhang and J. Zan and X. Liu and S. Gao},

doi = {10.1016/j.palaeo.2016.09.002},

year  = {2016},

date = {2016-01-01},

journal = {Palaeogeography, Palaeoclimatology, Palaeoecology},

volume = {461},

pages = {418--431},

abstract = {The uplift of the northern Tibetan Plateau (TP) has long been regarded as one of major factors accounting for both the enhanced process of aridification recorded in central Asia and the shifts in the Asian monsoonal circulations that are known to have occurred at approximately 8 Ma. Until now, there have been fewsedimentary records reported on which can directly, and in an integrated fashion, shed light on the regiontextquoterights tectonic and climate regimes. This can be largely attributed to the fact that the influence exerted by the presence of source materialsand subsequent sedimentary sorting in this tectonically active regionwould be likely to bias significantly any paleoclimatic interpretation of silicate-derived proxies. Based on detailed investigations of strontium(Sr) distributions revealed by multi-step leaching in a fluvial sequence from the Linxia Basin which includes paleosols, we reconstructed the long-term late Miocene regional climatic and environmental changes likely to have occurred on the northeastern TP from 12.1 to 5.2 Ma. We investigated Sr-related proxies in two typical paleosol profilesto constrain Srmobility in paleosolweathering, and, thus, to further prompt the interpretation of Sr-related proxies along thewhole section.Wewould suggest that carbonate-derived Sr concentrations and Sr/Ca ratios are suitable proxies for tracing regional climate change associated with weathering and pedogenesis; together, they exhibit weakened chemical weathering intensity and pedogenesis at textasciitilde8.6 Ma. The concomitant appearance of immature sediments through poor sedimentary sorting revealed by silicate-derived Rb/Sr, 87Sr/86Sr and Eu anomaly (Eu/Eu*) alongside a sharp increase in sedimentation rates noted at this time suggests that itwas indeed tectonic uplift that principally controlled the dramatic climatic and environmental changes. This multi-proxy record of concomitant tectonic uplift and climate change in the Linxia Basin provides direct geological evidence foruplift driven climate change in the northeastern TP region.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bickle_etal2015,

title = {On discrimination between carbonate and silicate inputs to Himalayan rivers},

author = {M. J. Bickle and ED. Tipper and A. Galy and H. Chapman and N. Harris},

doi = {10.2475/02.2015.02]},

year  = {2015},

date = {2015-01-01},

journal = {American Journal of Science},

volume = {315},

number = {2},

pages = {120--166},

abstract = {We review new and published analyses of river waters, bedloads and their constituent minerals from the Dhauli Ganga and Alaknanda, headwaters of the Ganges in Garhwal, and the Marsyandi in Nepal and their tributaries. These data areused to discriminate between the inputs of major cations and Sr from silicate andcarbonate sources. Methods of estimating the proportion of the carbonate and silicate inputs to river waters using mixing arrays in Sr-Ca-Mg-Na-K-87Sr/86Sr space are shown to suffer from systematic correlations between the magnitude of the precipitation of secondary calcite and the fraction of the silicate component. This results in factor-of two over estimates of the fractions of silicate-derived Ca, Mg and Sr. To correct for this the magnitude of secondary calcite precipitated and relative fractions of silicate and carbonate-derived cations are instead calculated by modeling the displacement of water compositions from the compositions of the carbonate and silicate components of the bedload in subsets of Sr-Ca-Mg-Na-K-87Sr/86Sr space. The compositions of the carbonate and silicate end-members in the bedload are determined by sequential leaching. The results of this modeling are compared with modeling of the modal mineral inputs to waters where mineral compositions are derived from electron microprobe analyses of the minerals in the bedload. In the upper Marsyandi catchment, which drains low-grade Tethyan Sedimentary Series formations, a set of mainstem samples collected over a two-year period define tight correlations in Sr-Ca-Mg-Na-K-87Sr/86Sr space. Modeling of the magnitude of secondary carbonate precipitation and fractions of silicate-derived Ca, Mg and Sr in Sr-Ca-Mg-87Sr/86Sr space gives self consistent results that are compatible with both the calculations of mineral modes and published Mg-isotopic compositions, if the ratio of chlorite to biotite weathering is high or if there is another silicate source of Mg. These calculations imply that between 12 and 31 percent of the Sr and 44 and 72 percent of the Mg is derived from silicate minerals where the range reflects the seasonal change in the ratio of silicate-derived to carbonate-derived cations. Modeling in Sr-Ca-Na and/or K space is inconsistent with the Sr-isotopic and Mg-isotopic constraints and we conclude that in this catchment dissolution of Na and K are incongruent relative to Sr-Ca-Mg. Potassium is preferentially retained in micas whereas the controls on Na are unclear. Modeling of the catchments underlain by High Himalayan Crystalline and Lesser Himalayan Series in Garhwal is complicated by the presence of dolomite as well as calcite in the carbonate and the results imply that dolomite dissolves faster in the acetic acid leaches than in nature. Up to 60 percent of the Sr in the catchment on High Himalayan Crystalline Series and 20 to 30 percent of Sr in the catchments on Lesser Himalayan Series are estimated to be derived from silicates. However it should be noted that the element budgets are not all self-consistent and the use of bedrock-element ratios to model the sources of chemical inputs to river waters remains subject to uncertainties.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gpel_etal2015,

title = {Mn--Cr systematics in primitive meteorites: Insights from mineral separation and partial dissolution},

author = {C. G\"{o}pel and J. L. Birck and A. Galy and J. A. Barrat and B. Zanda},

doi = {10.1016/j.gca.2015.02.008},

year  = {2015},

date = {2015-01-01},

journal = {Geochimica et Cosmochimica Acta},

volume = {156},

number = {05},

pages = {1--24},

abstract = {Cr isotopic compositions have been measured on carbonaceous chondrites (CC): Tafassasset, Paris, Niger I, NWA 5958, NWA 8157 and Jbilet Winselwan. In bulk samples, the 54Cr/52Cr ratios (expressed as e54Cr) range from 0.93 to 1.58 e units.These values are in agreement with values characteristic for distinct petrologic types. Despite this 54Cr heterogeneity, the variability in the 53Cr/52Cr ratios (expressed as e53Cr) of 0.2 e units and the Mn/Cr ratios is consistent with the previous finding of an isochron in the Mn--Cr evolution diagram. The Mn/Cr ratio in CC corresponds to variable abundances of high-T condensate formed and separated at the beginning of the solar system, thus the canonical 53Mn/55Mn ratio can be defined. Based on a consistent chronology for U--Pb and Mn--Cr between the earliest objects formed in the solar nebula and the DtextquoterightOrbigny angrite we define a canonical 53Mn/55Mn ratio and e53Cri of 6.8 ! 10textquotelefttextquoteleft6 and textquoterighttextquoteright0.177, respectively. The internal Mn/Cr systematics in Tafassasset and Paris were studied by two approaches: leaching technique and mineral separation. Despite variable e54Cr values (up to \>30 e) linear co-variations were found between e53Cr and Mn/Cr ratio. The mineral separates as well as the leachates of Tafassasset fall on a common isochron indicating that (1) cooling of the Tafassassettextquoterights parent body occurred at 4563.5 textpm 0.25 Ma, and that (2) 54Cr is decoupled from the other isotopes even though temperatures \>900 !C have been reached during metamorphism. In the case of Paris, the leachates form an alignment with a 53Mn/55Mn ratio higher than the canonical value. This alignment is not an isochron but rather a mixing line. Based on leachates from various CM and CI, we propose the occurrence of three distinct Cr reservoirs in meteoritic material: PURE54, HIGH53 and LOW53 characterized by a e53Cr and e54Cr of 0 and 25,000, textquotelefttextquoteleft2.17 and 8, and 0.5 and textquoterighttextquoteright151, respectively.PURE54 has already been described and is carried by highly refractory nano-spinel; HIGH53 is Mn-rich and most probably carried by sulfides in the matrix, whereas LOW53 is characterized by low Mn/Cr ratios and it is sensitive to metamorphism.This component could correspond to mineral phases such as refractory oxides and carbide. Variable mixing proportions of HIGH53 and LOW53 would explain the larger-than-expected uncertainty (MSWD of 5.5) on the CC bulk regression line. A Monte Carlo simulation allows us to evaluate the impact of the dispersion of the initial Cr isotopic ratios (as a function of variable HIGH53). The co-variation of the Mn/Cr ratio and the e53Cr defined by the mineral separates from Paris correspondsto an age of 4566.44 +0.66/textquotelefttextquoteleft0.75 Ma, while their e54Cr still differ by at least 0.42 e. This age is likely to date the segregation of forsteritic olivines (most probably from type I chondrules) from fayalitic olivines (from type II chondrules) and, given the sampling procedure by handpicking of hundreds of grains, corresponds to the average age of chondrule formation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Sparkes_etal2015,

title = {Redistribution of multi-phase particulate organic carbon in a marine shelf and canyon system during an exceptional river flood: Effects of Typhoon Morakot on the Gaoping River--Canyon system},

author = {R. B. Sparkes and I. T. Lin and N. Hovius and A. Galy and J. T. Liu and X. Xu and R. Yang},

year  = {2015},

date = {2015-01-01},

journal = {Marine Geology},

volume = {363},

number = {05},

pages = {191--201},

abstract = {Volumetrically, turbidity currents are the prime suppliers of sediment to the deep sea, and conveyors of organic carbon fromthe terrestrial biosphere and submarine shelf into marine depositional basins. They result from complex processes of erosion, transport and deposition that can be difficult to study in detail. Here we present data from the Gaoping submarine canyon system, off SW Taiwan, which was perturbed in 2009 by the addition of flood deposits following Typhoon Morakot and sampled by gravity coring less than 2 months after the event. We use the different origins of organic carbon, distinguished by their carbon and nitrogen concentrations and $delta$13C and $delta$15N isotopic composition, to compare and contrast standard and extreme sedimentological conditions. Using well-constrained end-members, the results were de-convolved into inputs of metamorphic and sedimentary fossil organic carbon eroded within the Gaoping River basin, terrestrial non-fossil carbon and marine organic matter. In the upper Gaoping Canyon, sedimentation is dominated by the highly-localised hyperpycnal input ofriver washload and submarine sediment slumps, each associated with extensive flooding following Typhoon Morakot, whilst the shelf experienced deposition and reworking of hemi-pelagic marine sediments. A terrestrial signal is also found in the core-top of a fine-grained shelf sample over 20 km from the Gaoping Canyon, in a region normally dominated by marine carbon deposition, showing that Morakot was an unusually large flood event. Conversely, sediment from just above the canyon thalweg contains 0.23 wt.% depth-averaged marine organic carbon (37% of the TOC content) implying that terrestrial OC-dominated turbidites are tightly constrainedwithin the canyon. Hyperpycnal processes can lead to the rapid and efficient transport of both terrestrial and submarine sediments to more permanent burial locations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Wilson_etal2015,

title = {Quaternary climate modulation of Pb isotopes in the deep Indian Ocean linked to the Himalayan chemical weathering},

author = {D. J. Wilson and A. Galy and A. M. Piotrowski and V. K. Banakar},

doi = {10.1016/j.epsl.2015.05.014},

year  = {2015},

date = {2015-01-01},

journal = {Earth and Planetary Science Letters},

volume = {424},

pages = {256--268},

abstract = {We use reductive sediment leaching to extract lead (Pb) from the authigenic fraction of marine sediments and reconstruct the Pb isotope evolution of the deep central Indian Ocean over the past 250 thousand years at �`u3kyr resolution. Temporal variations define a binary mixing line that is consistent with data from ferromanganese nodules and which records mixing between two well-defined endmembers through time. The unradiogenic endmember appears to represent a widely-distributed Pb source, from mid-ocean ridges or possibly volcanic aerosols, while the radiogenic endmember coincides with the composition of Ganges--Brahmaputra river sediments that are indicative of the Himalayan weathering inputs. Glacial--interglacial Pb isotope variations are striking and can be explained by an enhancement of Himalayan contributions by two to three times during interglacial periods, indicating that climate modulates the supply of dissolved elements to the ocean. While these changes could accurately record variations in the continental chemical weathering flux in response to warmer and wetter conditions during interglacials, the relative proportions of Pb derived from the Ganges and Brahmaputra appear to have been constant through time. This observation may point towards particulate-dissolved interactions in the estuary or pro-delta as a buffer of short timescale variability in the composition (and potentially flux) of the fluvial inputs. In addition, the changes are recorded at 3800m water depth, and with the lack of deep water formation in the Bay of Bengal, a mechanism to transfer such a signature into the deep ocean could either be reversible scavenging of dissolved Pb inputs and/or boundary exchange on the deep sea fan. Unless the mechanism transferring the Pb isotope signature into the deep ocean was itself highly sensitive to global climate cycles, and with the absence of a precessional signal in our Pb isotope data, we suggest that the Indian climate and its influence on basin-scale chemical weathering were strongly modulated by glacial versus interglacial boundary conditions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Wilson_etal2015_2,

title = {Interhemispheric controls on deep ocean circulation and carbon chemistry during the last two glacial cycles},

author = {D. J. Wilson and A. M. Piotrowski and A. Galy and V. K. Banakar},

doi = {10.1002/2014PA002707},

year  = {2015},

date = {2015-01-01},

journal = {Paleoceanography},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Wilson_etal2015_3,

title = {Interhemispheric controls on deep ocean circulation and carbon chemistry during the last two glacial cycles},

author = {D. J. Wilson and A. M. Piotrowski and A. Galy and V. K. Banakar},

doi = {10.1002/2014PA002707},

year  = {2015},

date = {2015-01-01},

journal = {Paleoceanography},

volume = {30},

pages = {621--641},

abstract = {Changes in ocean circulation structure, together with biological cycling, have been proposed for trapping carbon in the deep ocean during glacial periods of the Late Pleistocene, but uncertainty remains in the nature and timing of deep ocean circulation changes through glacial cycles. In this study, we use neodymium (Nd) and carbon isotopes from a deep Indian Ocean sediment core to reconstruct water mass mixing and carbon cycling in Circumpolar Deep Water over the past 250 thousand years, a period encompassing two full glacial cycles and including a range of orbital forcing. Building on recent studies, we use reductive sediment leaching supported by measurements on isolated phases (foraminifera and fish teeth) in order to obtain a robust seawater Nd isotope reconstruction. Neodymium isotopes record a changing North Atlantic Deep Water (NADW) component in the deep Indian Ocean that bears a striking resemblance to Northern Hemisphere climate records. In particular, we identify both an approximately in-phase link to Northern Hemisphere summer insolation in the precession band and a longer-term reduction of NADW contributions over the course of glacial cycles. The orbital timescale changes may record the influence of insolation forcing, for example via NADW temperature and/or Antarctic sea ice extent, on deep stratification and mixing in the Southern Ocean, leading to isolation of the global deep oceans from an NADW source during times of low Northern Hemisphere summer insolation. That evidence could support an active role for changing deep ocean circulation in carbon storage during glacial inceptions. However, mid-depth water mass mixing and deep ocean carbon storage were largely decoupled within glacial periods, and a return to an interglacial-like circulation state during marine isotope stage (MIS) 6.5 was accompanied by only minor changes in atmospheric CO2. Although a gradual reduction of NADW export through glacial periods may have produced slow climate feedbacks linked to the growth of Northern Hemisphere ice sheets, carbon cycling in the glacial ocean was instead more strongly linked to Southern Ocean processes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Yang_etal2015,

title = {Carbonate composition and its impact on fluvial geochemistry in the NE Tibetan Plateau region},

author = {Y. Yang and X. Fan and A. Galy and G. Zhang and S. Liu and J. Zan and F. Wu and Q. Meng and C. Ye and R. Yang and X. Liu},

year  = {2015},

date = {2015-01-01},

journal = {Chemical Geology},

volume = {410},

pages = {138--148},

abstract = {Using co-variations of Sr/Ca and Mg/Ca, we examined the carbonate compositions of various bedrocks (silicate and carbonate rocks) and sediments (eolian and fluvial sediments, sand, and topsoil) found in the NE Tibetan Plateau (TP) region. A combined carbonate composition dataset based on our results and other reported datashows that bedrock carbonate composition on the NE TP displays amuch broader range of Sr/Ca and Mg/Ca ratios than restricted source carbonate endmembers reported upon in previous studies. This has clear implications for modern weathering studies in addition to paleo-reconstructions in this tectonically active and climatically variable area during the Late Cenozoic. Bedrock carbonate compositions are characterized by disseminated carbonates with higher Sr/Ca and Mg/Ca ratios, and sedimentary carbonates (mostly marine) with lower Sr/Ca, butvariable Mg/Ca, ratios. The mostly authigenic carbonates found in sediments show similar trends,with a gradient textasciitilde0.97--1.00 in a plot of log (Sr/Ca) versus log (Mg/Ca), suggesting that textquoteleftcalcite precipitationtextquoteright processes -- i.e. the sources of the dissolved cations in the water -- control their chemistry. Based on observations and modeling, we conclude that the mixing of authigenic and bedrock carbonate endmembers, plus the incongruent dissolution of bedrock carbonates, accounts for the bulk carbonate composition of sediments (e.g. loess, sand and topsoil). A comparison of bedrock and sedimentary carbonate composition with reported fluvial water data in the NETP suggests thatweathering of carbonates in terrigenous sediments, rather than in bedrock, ismostly responsible for the changes in fluvial Sr, Mg and Ca compositions. Our study suggests that interactions between carbonates and water occur widely during the exposure, transport and deposition of sediments, significantly modifying regional carbonate compositions and fluvial geochemistry.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Carignan_etal2004,

title = {A reflection on Mg, Cd, Ca, Li and Si isotopic measurements and related materials},

author = {J. Carignan and D. Cardinal and A. Eisenhauer and A. Galy and M. Rehk\"{a}mper and F. Wombacher and N. Vigier},

doi = {10.1111/j.1751-908X.2004.tb01050.x},

year  = {2004},

date = {2004-01-01},

journal = {Geostandards and Geoanalytical Research},

volume = {28},

number = {1},

pages = {139--148},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Galy_etal2003,

title = {Magnesium isotope heterogeneity of the isotopic standard SRM980 and new reference materials for magnesium-isotope-ratio measurements},

author = {A. Galy and O. Yoffe and P. E. Janney and R. W. Williams and C. Cloquet and O. Alard and L. Alicz and M. Wadhwa and I. D. Hutcheon and E. Ramon and J. Carignan},

doi = {10.1039/b309273a},

year  = {2003},

date = {2003-01-01},

journal = {Journal of Analytical Atomic Spectrometry},

volume = {18},

number = {11},

pages = {1352--1356},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Galy+France-Lanord2001,

title = {Higher erosion rates in the Himalaya : geochemical constraints on riverine fluxes},

author = {A. Galy and C. France-Lanord},

year  = {2001},

date = {2001-01-01},

journal = {Geology},

volume = {29},

number = {1},

pages = {23--26},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Huyghe_etal2001,

title = {Propagation of the thrust system and erosion in the Lesser Himalaya: Geochemical and sedimentological evidence},

author = {P. Huyghe and A. Galy and J. Mugnier and C. France-Lanord},

doi = {10.1130/0091-7613(2001)029\<1007:POTTSA\>2.0.CO;2},

year  = {2001},

date = {2001-01-01},

journal = {Geology},

volume = {29},

number = {11},

pages = {1007--1010},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Galy+France-Lanord1999,

title = {Processes of the weathering in the Ganges-Brahmaputra basin and the riverine alkalinity budget},

author = {A. Galy and C. France-Lanord},

year  = {1999},

date = {1999-01-01},

journal = {Chemical Geology},

volume = {159},

pages = {31--60},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Galy+France-Lanord1999_2,

title = {Weathering processes in the Ganges-Brahmaputra basin and the riverine alkalinity budget},

author = {A. Galy and C. France-Lanord},

year  = {1999},

date = {1999-01-01},

journal = {Chemical Geology (Isotope Geoscience Section)},

volume = {159},

pages = {31--60},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Galy_etal1999,

title = {The strontium isotopic budget of Himalayan Rivers in Nepal and Bangladesh},

author = {A. Galy and C. France-Lanord and L. A. Derry},

doi = {10.1016/S0016-7037(99)00081-2},

year  = {1999},

date = {1999-01-01},

journal = {Geochimica et Cosmochimica Acta},

volume = {63},

number = {13/14},

pages = {1905--1926},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Jouanne_etal1999,

title = {Oblique convergence in the Himalayas of western Nepal deduced from preliminary results of GPS measurements},

author = {F. Jouanne and J. L. Mugnier and M. R. Pandey and J. F. Gamond and P. Le Fort and L. Serrurier and C. Vigny and J. P. Avouac and A. Galy},

doi = {10.1029/1999GL900416},

year  = {1999},

date = {1999-01-01},

journal = {Geophysical Research Letters},

volume = {26},

pages = {1933--1936},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Huyghe_etal1998,

title = {Micro-structures, clay mineralogy and geochemistry of the clay size fraction (\<2 textmum) of thrusted zones (Karnali area, Siwaliks of Western Nepal)},

author = {P. Huyghe and A. Galy and J. L. Mugnier},

year  = {1998},

date = {1998-01-01},

journal = {Journal of Nepal Geological Society},

volume = {18},

pages = {239--248},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Galy_etal1996,

title = {The Late Oligocene-Early Miocene Himalayan belt : constraints deduced from isotopic compositions of Early Miocene turbidites in the Bengal Fan},

author = {A. Galy and C. France-Lanord and L. A. Derry},

year  = {1996},

date = {1996-01-01},

journal = {Tectonophysics},

volume = {260},

pages = {109--119},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Alt_etal1992,

title = {Low temperature hydrothermal alteration of jurassic ocean crust, Site 801},

author = {J. C. Alt and C. France-Lanord and P. A. Floyd and P. Castillo and A. Galy},

year  = {1992},

date = {1992-01-01},

journal = {Proceedings of the Ocean Drilling Program, Scientific Results : College Station, TX (Ocean Drilling Program)},

volume = {129},

pages = {415--427},

keywords = {},

pubstate = {published},

tppubtype = {article}

}