Étude du système binaire CV Ser à l'aide du satellite MOST

Ce mémoire s’intéresse au système binaire massif CV Serpentis, composé d’une Wolf- Rayet riche en carbone et d’une étoile de la séquence principale, de type spectral O (WC8d + O8-9IV). D’abord, certains phénomènes affectant les étoiles massives sont mentionnés, de leur passage sur la séquence principale à leur mort (supernova). Au cours du premier cha- pitre, un rappel est fait concernant certaines bases de l’astrophysique stellaire observa- tionnelle (diagramme Hertzsprung-Russell, phases évolutives, etc...). Au chapitre suivant, un des aspects les plus importants de la vie des étoiles massives est abordé : la perte de masse sous forme de vents stellaires. Un historique de la découverte des vents ouvre le chapitre, suivi des fondements théoriques permettant d’expliquer ce phénomène. Ensuite, différents aspects propres aux vents stellaires sont présentés. Au troisième chapitre, un historique détaillé de CV Ser est présenté en guise d’introduc- tion à cet objet singulier. Ses principales caractéristiques connues y sont mentionnées. Finalement, le cœur de ce mémoire se retrouve au chapitre 4. Des courbes de lumière ultra précises du satellite MOST (2009 et 2010) montrent une variation apparente du taux de perte de masse de la WR de l’ordre de 62% sur une période orbitale de 29.701 jours. L’analyse des résidus permet de trouver une signature suggérant la présence de régions d’interaction en corotation (en anglais corotating interaction regions, ou CIR) dans le vent WR. Une nouvelle solution orbitale est présentée ainsi que les paramètres de la région de collision des vents et les types spectraux sont confirmés.

As relações entre tectonismo e seqüências deposiconais no rifte potiguar - porção SW do Graben de Umbuzeiro, bacia potiguar emersa

Through an integrated approach, using litho, chrono and biostratigraphic data, the relative importance of climate variations and tectonics were recognized in rift sediments of the onshore Potiguar Basin, Northeast Brazil. Concepts of sequence stratigraphy were applied as a template to integrate sedimentological and geochemical data (oxygen isotopes), as well as quantitative palynologic methods to address and recognize the main depositional patterns produced in a rift basin. The main objective was to address the relative importance of climate changes and tectonics to the resultant stratigraphic architecture. The results of computer simulations of sedimentary basin fills of rift basins were quite useful to test working hypothesis and mimic the process of filling a half graben during a rift event. The studied section includes a neovalanginian-eobarremian (Lower Cretaceous) rift interval from the Pendência Formation, located in the southwestern portion of Umbuzeiro Graben, in the offshore Potiguar Basin. The depositional setting is interpreted as progradational deltaic system entering a lake from its flexural margin. Sismoestratigraphyc and well logs analyses allowed to interpret two regressive intervals (Green and Yellow Sequences), separated by a broad transgressive interval (Orange Sequence), known as the Livramento Shale. The depositional history encompass three stages: two tectonically active phases, during the deposition of the Green and Yellow Sequences, and a tectonically quiescent phase, during the deposition of the Orange Sequence. Paleoclimatic interpretation, based on quantitative palynology and geochemical data (��18O), suggests a tendency to arid conditions during the tectonically active phases and wet conditions during the tectonically quiescent phase. Stratigraphic modeling and backstripping techniques, supported by paleoclimatic/paleoecologic interpretations provide a powerful methodology to evaluate the tectonic and climatic controls on tectonic lakes

Caracterização de reservatórios siliciclásticos neoaptianos: um estudo do membro carmópolis no campo de Camorim, sub-bacia de Sergipe, Brasil

The Camorim Oilfield, discovered in 1970 in the shallow water domain of the Sergipe Sub-basin, produces hydrocarbons from the Carmópolis Member of the Muribeca Formation, the main reservoir interval, interpreted as siliciclastics deposited in an alluvial-fluvial-deltaic context during a late rifting phase of Neoaptian age, in the Sergipe-Alagoas Basin. The structural setting of the field defines different production blocks, being associated to the evolution of the Atalaia High during the rift stage and subsequent reactivations, encompassing NE-SW trending major normal faults and NWEW trending secondary faults. The complexity of this field is related to the strong facies variation due to the interaction between continental and coastal depositional environments, coupled with strata juxtaposition along fault blocks. This study aims to geologically characterize its reservoirs, to provide new insights to well drilling locations in order to increase the recovery factor of the field. Facies analysis based on drill cores and geophysical logs and the 3D interpretation of a seismic volume, provide a high resolution stratigraphic analysis approach to be applied in this geodynamic transitional context between the rift and drift evolutionary stages of the basin. The objective was to define spatial and time relations between production zones and the preferential directions of fluid flow, using isochore maps that represent the external geometry of the deposits and facies distribution maps to characterize the internal heterogeneities of these intervals, identified in a 4th order stratigraphic zoning. This work methodology, integrated in a 3D geological modelling process, will help to optimize well drilling and hydrocarbons production. This methodology may be applied in other reservoirs in tectonic and depositional contexts similar to the one observed at Camorim, for example, the oil fields in the Aracaju High, Sergipe Sub-basin, which together represent the largest volume of oil in place in onshore Brazilian basins

Zur Karbonatsedimentologie, Biofazies und sequenzstratigraphischen Architektur eines fossilen Hochenergie-Schelfs aus dem Neogen der Algarve (Miozän, Südportugal)

Die neogene Lagos-Portimão Formation (Unter- bis Mittelmiozän) bildet einen Teil der Steilküste der Algarve (S-Portugal) und besteht aus einer zyklischen Wechsellagerung von Karbonaten und Sand-steinen. Die vorliegende Arbeit bietet ein Modell zur sedimentologischen, faziellen und stratigraphischen Entwicklung dieser Einheit an. Basierend auf Profilen entlang der gesamten lateralen Erstreckung der Einheit wurden verschiedene Gelände- und Labormethoden angewandt, um ein Modell entwickeln zu können. Messungen des Sr87/86-Isotopenverhältnisses sollten Klarheit bezüglich der stratigraphischen Position bringen. Die laterale Korrelation der Profile erfolgte über lithologische und fazielle Ansprachen. Unterstützend wurden einzelne Profile mit einem tragbaren Gammaray-Spektrometer gemessen. Es wurden vier Leithorizonte etabliert, die sich durch fazielle Merkmale und spezielle Fossilführung defi-nieren lassen. Die Mikrofazies wurde qualitativ und quantitativ analysiert. Als statistisches Verfahren wurde unter anderem eine hierarchische Clusteranalyse durchgeführt, über welche fünf Biofaziestypen des warm-temperierten Klimabereichs unterschieden werden. Die Fossilführung wird von Mollusken, Bryozoen und Rotalgen dominiert. Ausnahmen bilden stratigraphisch isolierte Vorkommen von kolo-nialen Korallen, die jedoch keine Riffkörper aufbauen. Die Ergebnisse aller zuvor erwähnten Untersuchungen deuten auf Ablagerungen eines nicht-tropischen Hochenergie-Schelfs hin. Sedimentäre Zyklen sind oftmals unvollständig, es treten Hartgründe und Auf-arbeitungs- bzw- Kondesationshorizonte auf. Die geochemische Altersdatierung weist Alterssprünge und -inversionen auf. Ein Vergleich mit dem SW-australischen Schelf und dem von James et al. (1994) eingeführten Modell des shaved shelf bietet sich aufgrund der Ähnlichkeit der Sedimentgesteine und des ozeanographischen Settings an. Weiterhin werden zeitgleiche bzw. faziell ähnliche Becken vergleichend diskutiert. Das Sedimentationsgeschehen der Lagos-Portimão Formation wird maßgeblich durch eine halokinetisch bedingte unregelmäßige Subsidenz und Hebung beeinflußt. Der Salzdom von Albufeira war während der Sedimentation der Einheit mehrfach in Bewegung. Rutschungspakete, Entlastungsspalten und Sanddikes zeugen davon. Die sequenzstratigraphische Interpretation bietet einen neuen Ansatz, in dem sie von Hochstand-Sandsteinen und Tiefstand-Karbonaten ausgeht.

Organic geochemistry of upper Jurassic-Cretaceous sediments at DSDP Hole 71-511

Cretaceous and Jurassic sediments 435 m thick were drilled at Site 511, in the basin province of the Falkland Plateau, during DSDP Leg 71. The calcareous Unit 3 and the clayey zeolitic Unit 4, both of Senonian age, revealed poorly preserved organic matter indicative of oxidized environments. The same characteristics prevailed for the clayey Unit 5 of Turonian to Albian age. Strictly reducing environments existed for black facies along Unit 6 of earliest Albian to Late Jurassic age and allowed the preservation of a rich organic material that is marine in origin. Besides the transition from reducing conditions in Unit 6 to oxidizing conditions in Unit 5, there are 20 meters of sediments in Cores 56-58 where detrital, nonmarine and then marine organic matter, both implying more or less reducing environments, are interlain by poorly preserved material. In the black shales of the bottom Cores 69 and 70, some nonmarine detritus is mixed with the predominantly marine organic material. An immature stage of evolution can be assigned to all of the samples studied. The chapter also undertakes a comparison with contemporaneous lithologies at adjacent Sites 327 and 330 and attempts some reconstruction of the geography of the eastern Falkland Plateau during the Mesozoic.

Organic geochemistry of lower Cretaceous sediments at DSDP Hole 77-535

At Site 535, the four lithologic units of Cretaceous age are controlled by two types of sedimentologic facies: (1) the massive light-colored limestones or marly limestones in which the total organic carbon (TOC) content is low and the organic matter more or less oxidized and (2) laminated dark facies in which the TOC content is higher and associated with a well-preserved organic matter of Type II origin. Very little typical Type III organic matter occurs in the whole series from late Berriasian to Aptian and Cenomanian. Fluctuations from oxidizing to reducing environments of deposition are proposed to account for the variations in properties of the Type II organic matter between the different facies. Dark laminated layers are good but immature potential source rocks: petroleum potential is often higher than 2 kg HC/t of rock.

Carbonate content and d13C record of a Jordan Cretaceous outcrop (Section GM3 (Ghawr Al Mazar (Ghor al Mazrar))

An evaluation of the global synchronicity and duration of "3rd-order" sea-level fluctuations during the Cretaceous greenhouse has been hampered by poor constraints on potential climatic and tectonic drivers, and limitations of geochronology and chronostratigraphic correlation. To provide insight into the nature of such sea-level fluctuations, here we present a new Late Cretaceous record from the Jordanian Levant Platform, comprising a detailed physical-, bio-, chemo- and sequence stratigraphy. Carbonate content of these strata reflects overall sequence stratigraphic development, and demonstrates a dramatic 3rd-order-scale cycle that is also apparent in the d°C record. Updated radioisotopic constraints and astrochronologic testing provide support for the inference of an ~1 million year long sea-level oscillation associated with this 3rd-order cycle, which likely reflects a long-period obliquity (1.2 Myr) control on eustasy and stratigraphic sequence development, linked to the global carbon cycle. The observation of cyclic sea-level fluctuations on this time scale suggests sustained global modulation of continental fresh-water-storage. The hypothesized link between astronomical forcing and sea-level forms a baseline approach in the global correlation of sequence boundaries.

Organic matter composition and sulfate reduction intensity in Oman Margin sediments

Petrographical and geochemical studies of Neogene marine sediments from the Oman Sea (Leg 117, Sites 720, 724, 726 and 730), show a close relationship between the nature and amount of the organic matter, and the degree of degradation of organic matter by sulfate reduction, i.e. pyritization. Petrographically, three major pyritization types were observed: (1) Finely dispersed pyrite framboids in sediments from Oman Margin and Indus Fan, enriched in autochthonous marine organic matter. (2) Infilling of pores by massive pyrite crystals in Oman Margin sediments with a low TOC and a high microfossil content. (3) Pyrite mineralization of lignaceous fragments in organic-depleted sediments from the Indus Fan leading to more massive pyrite. Geochemically, we can define a sulfate reduction index (SRI) as the percentage of initial organic carbon versus that of residual organic carbon. Finely laminated Pliocene-Pleistocene sediments from the Oman Margin exclusively contain organic matter deriving from organic phytoplankton, for which the quantity (TOC) positively correlates with the geochemical quality (Hydrogen Index). We think that the occurrence of this residual organic matter is linked mainly to a high primary paleo-productivity. The intensity of sulfate reduction is constant for sediments with TOC up to 2% and becomes more important when organic input decreases. This degradation process can destroy up to 50% of the initial organic matter, but is not sufficient to explain some of the encountered very low TOC values. It can be seen that sharp increases of certain plankton species (with mineral skeletons) are responsible for a pronounced degradation of organic matter, due to increased sulfate reduction. In that case, the organic matter may be strongly degraded (high SRI), although deposited in an oxygen-depleted environment. Conversely, Miocene-Pliocene sediments contain an autochthonous organic matter that is typical of both low productivity and oxic processes; their very low sulfate reduction index indicates that very little metabolizable organic matter was initially present.

Stable isotope, seismic sequence boundaries and bioevents in ODP Hole 166-1006A

During ODP Leg 166, the recovery of cores from a transect of drill sites across the Bahamas margin from marginal to deep basin environments was an essential requirement for the study of the response of the sedimentary systems to sea-level changes. A detailed biostratigraphy based on planktonic foraminifera was performed on ODP Hole 1006A for an accurate stratigraphic control. The investigated late middle Miocene-early Pliocene sequence spans the interval from about 12.5 Ma (Biozone N12) to approximately 4.5 Ma (Biozone N19). Several bioevents calibrated with the time scale of Berggren et al. (1995a,b) were identified. The ODP Site 1006 benthic oxygen isotope stratigraphy can be correlated to the corresponding deep-water benthic oxygen isotope curve from ODP Site 846 in the Eastern Equatorial Pacific (Shackleton et al., 1995. Proc. ODP Sci. Res. 138, 337-356), which was orbitally tuned for the entire Pliocene into the latest Miocene at 6.0 Ma. The approximate stratigraphic match of the isotopic signals from both records between 4.5 and 6.0 Ma implies that the paleoceanographic signal from the Bahamas is not simply a record of regional variations but, indeed, represents glacio-eustatic fluctuations. The ODP Site 1006 oxygen and carbon isotope record, based on benthic and planktonic foraminifera, was used to define paleoceanographic changes on the margin, which could be tied to lithostratigraphic events on the Bahamas carbonate platform using seismic sequence stratigraphy. The oxygen isotope values show a general cooling trend from the middle to late Miocene, which was interrupted by a significant trend towards warmer sea-surface temperatures (SST) and associated sea-level rise with decreased ice volume during the latest Miocene. This trend reached a maximum coincident with the Miocene/Pliocene boundary. An abrupt cooling in the early Pliocene then followed the warming which continued into the earliest Pliocene. The late Miocene paleoceanographic evolution along the Bahamas margin can be observed in the ODP Site 1006 delta13C values, which support other evidence for the beginning of the closure of the Panama gateway at 8 Ma followed by a reduced intermediate water supply of water from the Pacific into the Caribbean at about 5 Ma. A general correlation of lower sedimentation rates with the major seismic sequence boundaries (SSBs) was observed. Additionally, the SSBs are associated with transitions towards more positive oxygen isotope excursions. This observed correspondence implies that the presence of a SSB, representing a density impedance contrast in the sedimentary sequence, may reflect changes in the character of the deposited sediment during highstands versus those during lowstands. However, not all of the recorded oxygen isotope excursions correspond to SSBs. The absence of a SSB in association with an oxygen isotope excursion indicates that not all oxygen isotope sea-level events impact the carbonate margin to the same extent, or maybe even represent equivalent sea-level fluctuations. Thus, it can be tentatively concluded that SSBs produced on carbonate margins do record sea-level fluctuations but not every sea-level fluctuation is represented by a SSB in the sequence stratigraphic record.

Magnetic susceptibility (MS) measurements on the Sancerre (France) drill-core

The Toarcian Oceanic Anoxic Event (T-OAE) of the early Jurassic period involves one of the largest perturbations of the carbon cycle in the past 250 Ma, recorded by a pronounced negative carbon-isotope excursion (CIE). Numerous studies have focused on potential causes of the T-OAE and CIE, but are hampered by an uncertain timescale. Here we present high-resolution (~2 kyr) magnetic susceptibility (MS) measurements from the marine marls of the Sancerre-Couy drill-core, southern Paris Basin, spanning the entire Toarcian Stage. The MS variations document a rich series of sub-Milankovitch to Milankovitch frequencies (precession, obliquity and eccentricity) with the periodic g2-g5 (405 kyr) and quasi-periodic g4-g3 (~2.4 Myr Cenozoic mean periodicity) eccentricity terms being the most prominent. The MS-related g4-g3 variation reflects third-order eustatic sequences, and constrains the sequence stratigraphic framework of the Toarcian Stage. In addition, MS variations reveal a modulation of g2-g5 by g4-g3 eccentricity related cycles, suggesting that sea-level change was the main control on the deposition of the Toarcian Sancerre marls, in tune with the astro-climatic frequencies. The stable 405 kyr cyclicity constrains a minimum duration of the Toarcian Stage to ~8.3 Myr, and the well documented CIE, associated with the T-OAE, to ~300 to 500 kyr. The 405 kyr MS timescale calibrates the periodicity of the prominent high-frequency d13C cycles that occur in the decreasing part of the CIE to 30 to 34 kyr, consistent with the Toarcian obliquity period predicted for an Earth experiencing sustained tidal dissipation.

Zinc deposits and related mineralization of the Burketown mineral field, including the world-class Century Deposit, Northern Australia: Fluid inclusion and stable isotope evidence for basin fluid sources

The stratiform Century Zn-Pb deposit and the discordant Zn-Pb lode deposits of the Burketown mineral field, northern Australia, host ore and gangue minerals with primary fluid inclusions that have not been affected by the Isan orogeny, thus providing a unique opportunity to investigate the nature of the ore-forming brines. All of the deposits are hosted in shales and siltstones belonging to the Isa superbasin and comprise sphalerite, pyrite, carbonate, quartz, galena, minor chalcopyrite, and minor illite. According to Pb model ages, the main ore stage of mineralization at Century formed at I575 Ma, some 20 m.y. after deposition of the host shale sequence. Microthermometry on undeformed, primary fluid inclusions hosted in porous sphalerite shows that the Zn at Century was transported to the deposit by a homogeneous, Ca2+- and Na+-bearing brine with a salinity of 21.6 wt percent NaCl equiv. delta D-fluid of the fluid inclusion water ranges from -89 to -83 per mil, consistent with a basinal brine that evolved from meteoric water. Fluid inclusion homogenization temperatures range between 74 degrees and 125 degrees C, which are lower than the 120 degrees to 160 degrees C range calculated from vitrinite reflectance and illite crystallinity data from the deposit. This discrepancy indicates that mineralization likely formed at 50 to 85 Mpa, corresponding to a depth of 1,900 to 3,100 m. Transgressive galena-sphalerite veins that cut stratiform mineralization at Century and breccia-filled quartz-dolomite-sphalerite-galena veins in the discordant Zn-Pb lodes have Pb model ages between 1575 and 1485 Ma. Raman spectroscopy and microthermometry reveal that the primary fluid inclusions in these veins contain Ca2+, Na+. but they have lower salinities between 23 and 10 wt percent NaCl equiv and higher delta D-fluid values ranging from -89 to -61 per mil than fluid inclusions in porous sphalerite from Century. Fluid inclusion water from sphalerite in one of the lode deposits has delta O-18(fluid) values of 1.6 and 2.4 per mil, indistinguishable from delta O-18(fluid) values between -0.3 to +7.4 per mil calculated from the isotopic composition of coexisting quartz, dolomite, and illite. The trend toward lower salinities and higher delta D-fluid values relative to the earlier mineralizing fluids is attributed to mixing between the fluid that formed Century and a seawater-derived fluid from a different source. Based on seismic data from the Lawn Hill platform and paragenetic and geochemical results from the Leichhardt River fault trough to the south, diagenetic aquifers in the Underlying Calvert superbasin appear to have been the most likely sources for the fluids that formed Century and the discordant lode deposits. Paragenetically late sphalerite and calcite cut sphalerite, quartz, and dolomite in the lode deposits and contain Na+-dominated fluid inclusions with much lower salinities than their older counterparts. The isotopic composition of calcite also indicates delta O-18(fluid) from 3.3 to 10.7 per mil, which is larger than the range obtained from synmineralization minerals, supporting the idea that a unique fluid source was involved. The absolute timing of this event is unclear, but a plethora of Pb model, K-Ar, and Ar-40/Ar-39 ages between 1440 and 1300 Ma indicate that a significant volume of fluid was mobilized at this time. The deposition of the Roper superbasin from ca. 1492 +/- 4 Ma suggests that these late veins formed from fluids that may have been derived from aquifers in overlying sediments of the Roper superbasin. Clear, buck, and drusy quartz in veins unrelated to any form of Pb-Zn mineralization record the last major fluid event in the Burketown mineral field and form distinct outcrops and ridges in the district. Fluid inclusions in these veins indicate formation from a low-salinity, 300 degrees +/- 80 degrees C fluid. Temperatures approaching 300 degrees C recorded in organic matter adjacent to faults and at sequence boundaries correspond to K-Ar ages spanning 1300 to 1100 Ma, which coincides with regional hydrothermal activity in the northern Lawn Hill platform and the emplacement of the Lakeview Dolerite at the time of assemblage of the Rodinia supercontinent.

Sedimentology of a Middle Jurassic Base-of-Slope environment, Cutri Formation, Mallorca

The Cutri Formation’s, type location, exposed in the NW of Mallorca, Spain has previously been described by Álvaro et al., (1989) and further interpreted by Abbots (1989) unpublished PhD thesis as a base-of-slope carbonate apron. Incorporating new field and laboratory analysis this paper enhances this interpretation. From this analysis, it can be shown without reasonable doubt that the Cutri Formation was deposited in a carbonate base-of-slope environment on the palaeowindward side of a Mid-Jurassic Tethyan platform. Key evidence such as laterally extensive exposures, abundant deposits of calciturbidtes and debris flows amongst hemipelagic deposits strongly support this interpretation.

Stable isotopes of bulk organic matter to trace carbon and nitrogen dynamics in an estuarine ecosystem in Babitonga Bay (Santa Catarina, Brazil)

The biogeochemical processes affecting the transport and cycling of terrestrial organic carbon in coastal and transition areas are still not fully understood One means of distinguishing between the sources of organic materials contributing to particulate organic matter (POM) in Babitonga Bay waters and sediments is by the direct measurement of delta(13)C of dissolved inorganic carbon (DIC) and delta(13)C and delta(15)N in the organic constituents. An isotopic survey was taken from samples collected in the Bay in late spring of 2004. The results indicate that the delta(13)C and delta(15)N compositions of OM varied from -21.7 parts per thousand to -26 2 parts per thousand. and from + 9 2 parts per thousand. to -0 1 parts per thousand, respectively. delta(13)C from DIC ranges from +0.04 parts per thousand to -12.7 parts per thousand The difference in the isotope compositions enables the determination of three distinct end-members terrestrial, marine and urban Moreover, the evaluation of source contribution to the particulate organic matter (POM) in the Bay, enables assessment of the anthropogenic impact. Comparing the depleted values of delta(13)C(DIC) and delta(13)C(POC) it is possible to further understand the carbon dynamic within Babitonga Bay (C) 2010 Elsevier BV All rights reserved

Bryozoan stable carbon and hydrogen isotopes: relationships between the isotopic composition of zooids, statoblasts and lake water

We explored the extent to which δ13C and δD values of freshwater bryozoan statoblasts can provide information about the isotopic composition of zooids, bryozoan food and surrounding water. Bryozoan samples were collected from 23 sites and encompassed ranges of nearly 30‰ for δ13C and 100‰ for δD values. δ13C offsets between zooids and statoblasts generally ranged from −3 to +4.5‰, with larger offsets observed in four samples. However, a laboratory study with Plumatella emarginata and Lophopus crystallinus demonstrated that, in controlled settings, zooids had only 0–1.2‰ higher δ13C values than statoblasts, and 1.7‰ higher values than their food. At our field sites, we observed a strong positive correlation between median δ13C values of zooids and median δ13C values of corresponding statoblasts. We also observed a positive correlation between median δD values of zooids and statoblasts for Plumatella, and a positive correlation between median δD values of statoblasts and δD values of lake water for Plumatella and when all bryozoan taxa were examined together. Our results suggest that isotope measurements on statoblasts collected from flotsam or sediment samples can provide information on the feeding ecology of bryozoans and the H isotopic composition of lake water.

(Table 1) Organic carbon and radiogenic isotopes analysis of DSDP Hole 22-218 sediments

Modern erosion of the Himalaya, the world's largest mountain range, transfers huge dissolved and particulate loads to the ocean. It plays an important role in the long-term global carbon cycle, mostly through enhanced organic carbon burial in the Bengal Fan. To understand the role of past Himalayan erosion, the influence of changing climate and tectonic on erosion must be determined. Here we use a 12 Myr sedimentary record from the distal Bengal Fan (Deep Sea Drilling Project Site 218) to reconstruct the Mio-Pliocene history of Himalayan erosion. We use carbon stable isotopes (d13C) of bulk organic matter as paleo-environmental proxy and stratigraphic tool. Multi-isotopic - Sr, Nd and Os - data are used as proxies for the source of the sediments deposited in the Bengal Fan over time. d13C values of bulk organic matter shift dramatically towards less depleted values, revealing the widespread Late Miocene (ca. 7.4 Ma) expansion of C4 plants in the basin. Sr, Nd and Os isotopic compositions indicate a rather stable erosion pattern in the Himalaya range during the past 12 Myr. This supports the existence of a strong connection between the southern Tibetan plateau and the Bengal Fan. The tectonic evolution of the Himalaya range and Southern Tibet seems to have been unable to produce large re-organisation of the drainage system. Moreover, our data do not suggest a rapid change of the altitude of the southern Tibetan plateau during the past 12 Myr. Variations in Sr and Nd isotopic compositions around the late Miocene expansion of C4 plants are suggestive of a relative increase in the erosion of High Himalaya Crystalline rock (i.e. a simultaneous reduction of both Transhimalayan batholiths and Lesser Himalaya relative contributions). This could be related to an increase in aridity as suggested by the ecological and sedimentological changes at that time. A reversed trend in Sr and Nd isotopic compositions is observed at the Plio-Pleistocene transition that is likely related to higher precipitation and the development of glaciers in the Himalaya. These almost synchronous moderate changes in erosion pattern and climate changes during the late Miocene and at the Plio-Pleistocene transition support the notion of a dominant control of climate on Himalayan erosion during this time period. However, stable erosion regime during the Pleistocene is suggestive of a limited influence of the glacier development on Himalayan erosion.