Torsten Vennemann | University of Lausanne (original) (raw)

Papers by Torsten Vennemann

Papers in Palaeontology

Some 2.7 myr after the Permian–Triassic boundary mass extinction, a stepwise extinction of the ne... more Some 2.7 myr after the Permian–Triassic boundary mass extinction, a stepwise extinction of the nekton (ammonoids and conodonts) ended at the Smithian–Spathian boundary (SSB) during an episode of climate cooling. SSB records from continental shelves are usually affected by an unconformity, suggesting a forced regression of glacioeustatic origin. Here, we document a new 30-m-thick SSB section from Jebel Aweri (Batain Plain, Oman) that provides an exceptionally complete and expanded record preserved in an exotic block. Most of this SSB section consists of microbial boundstone build-ups with a framework of metazoan bioclasts that formed in shallow water on an offshore seamount. In Wadi Musjah (Hawasina nappes, Oman), another exotic block records the SSB in a deeper water setting represented by Hallstatt-type facies. These two sections provide a unique perspective on the early Spathian rapid re-diversification of conodonts. They led to a thorough revision of conodont taxonomy around the SSB and to the construction of the highest resolution biochronological scheme for this time interval in the Tethys. A total of five SSB sections from Oman representing both offshore seamounts and lower slope deposits were included in a high-resolution, quantitative unitary associations (UA) analysis. The resulting 8 conodont biozones are intercalibrated with ammonoid zones and with the carbonate carbon isotope record ultimately placing the SSB in the interval of separation between UAZ3 and UAZ4. Only the association of Novispathodus pingdingshanensis with Icriospathodus crassatus can be used to unambiguously characterize the base of the Spathian.

Journal of Geophysical Research: Biogeosciences

The global carbonate cycle plays a major role in the functioning of the Earth system and involves... more The global carbonate cycle plays a major role in the functioning of the Earth system and involves dissolution and precipitation reactions mediated by biogeochemical processes operating at distinct time scales (Ridgwell & Zeebe, 2005). Over geological time scales, carbonate reactions are considered ineffective in regulating atmospheric CO 2 as continental weathering of carbonates consuming CO 2 is offset by oceanic depositions that release CO 2 (Calmels et al., 2014). However, at shorter time scales, the carbonate cycle is intimately embedded within the carbon cycle, and its dynamics constrains major transformations across the organic and inorganic carbon reservoirs (Szramek & Walter, 2004). In inland waters, these controls also vary spatially, and the dynamics of carbonate cycling constrains different processes along the aquatic continuum. Carbonate weathering, for instance,

Nature Communications, 2022

Oxygen isotope compositions of fossil foraminifera tests are commonly used proxies for ocean pale... more Oxygen isotope compositions of fossil foraminifera tests are commonly used proxies for ocean paleotemperatures, with reconstructions spanning the last 112 million years. However, the isotopic composition of these calcitic tests can be substantially altered during diagenesis without discernible textural changes. Here, we investigate fluid-mediated isotopic exchange in pristine tests of three modern benthic foraminifera species (Ammonia sp., Haynesina germanica, and Amphistegina lessonii) following immersion into an 18O-enriched artificial seawater at 90 °C for hours to days. Reacted tests remain texturally pristine but their bulk oxygen isotope compositions reveal rapid and species-dependent isotopic exchange with the water. NanoSIMS imaging reveals the 3-dimensional intra-test distributions of 18O-enrichment that correlates with test ultra-structure and associated organic matter. Image analysis is used to quantify species level differences in test ultrastructure, which explains the ...

Frontiers in Earth Science, 2020

Contributions to Mineralogy and Petrology, 2021

Whiteschists from the Monte Rosa Nappe were examined in the field as well as with petrographic, g... more Whiteschists from the Monte Rosa Nappe were examined in the field as well as with petrographic, geochemical, and isotopic methods to constrain the controversial origin of these rocks in their Alpine metamorphic context. Whiteschists occur as ellipsoidal-shaped, decametric-sized bodies, within a Permian metagranite, and consist mainly of chloritoid, talc, phengite, and quartz. The transition from whiteschist to metagranite is marked by multiple sharp mineralogical boundaries defining concentric zones unrelated to Alpine deformation. The development of reaction zones, as well as the geometry of the whiteschist suggest a pervasive fluid infiltration, facilitated and canalized by reaction fingering. Whole-rock compositions of whiteschists and metagranites indicate an enrichment in MgO and H2O and depletion of Na2O, CaO, Ba, Sr, Pb, and Zn in the whiteschist relative to the metagranite. Trace- and rare-earth elements, together with all other major elements, notably K2O and SiO2, were wit...

Earth and Planetary Science Letters, 2018

Syntectonic veins commonly have been used to assess the composition and source of fluids involved... more Syntectonic veins commonly have been used to assess the composition and source of fluids involved in fault zone activity. Such veins also provide information on the ambient stress conditions during deformation and mineralization. Based on bulk sampling and bulk O-and C-isotope analysis, combined with fluid inclusion microthermometry, many studies have demonstrated that syntectonic veins provide snapshots of fluid composition and stress conditions over the course of fault history. This is widely acknowledged for mode I extension veins that develop in the damage zones of faults. However, an important and unanswered question is the extent to which such veins record a more detailed fault history at the micron scale. In this study, we present new detailed in-situ micron-scale δ 18 O data, measured using Secondary Ion Mass Spectrometry (SIMS), combined with detailed fluid inclusion microthermometry and 47 clumped isotope thermometry to document the fluid and temperature conditions during mode I vein growth related to deformation along the Cotiella thrust fault (Pyrenees). All the studied veins show three distinct episodes of vein opening, recording a complex history of varying fluid composition and temperature. Results show that the studied fault portion passed from a hydrological rock-buffered system, in which formation waters were in isotopic equilibrium with the host sediments, to a fluidbuffered system involving meteoric water. However, such information is only achievable at the micron scale using Secondary Ion Mass Spectrometry. This study demonstrates the potential of these new microbeam techniques for investigating fault behavior in more detail than previously available, particularly with respect to the nature of the fluids involved and the P-T conditions extant during fault activity.

Contributions to Mineralogy and Petrology, 2019

Quaternary eruptive products in the Cascade arc include a variety of different basalt types. At M... more Quaternary eruptive products in the Cascade arc include a variety of different basalt types. At Mount St. Helens (MSH), the most active volcano in the Cascades throughout the last 35 ka, three different mafic endmembers erupted at the end of the Castle Creek period (1900-1700 years B.P.): (1) high-field strength element (HFSE)-rich basalt enriched in K, Ti, P, and incompatible trace elements; (2) low-K olivine tholeiite (LKOT) with lower amounts of incompatible trace elements; and (3) calc-alkaline (arc-type) basaltic andesite with a typical subduction signature, i.e., enrichment in fluid-mobile large ion lithophile elements (LILE) relative to immobile high-field strength elements (HFSE). Each type has compositions projecting backwards to more primitive endmembers in the Cascades. Single units encompassing basaltic-to-basaltic andesitic compositions with intermediate trace-element abundances form two almost continuous trends towards basaltic andesite. These trends are interpreted to result from assimilation of pre-existing, more evolved, calc-alkaline material (and in one case mixing of different mafic magma types) during migration of the magmas through the crust. Most of the erupted basalts are porphyritic (10-30%) with an assemblage dominated by olivine and plagioclase and show disequilibrium textures preventing detailed reconstruction of mantle melting processes. Although typical hydrous arc basalt produced by flux melting in the mantle is absent in the eruptive products of MSH, arc-type basaltic andesite suggests its presence at depth. LKOT magmas are interpreted as decompression melts from the upper mantle, whereas HFSE-rich basalts are likely derived from the water-poor periphery of the main flux melting regime, potentially tapping a trace-element-enriched source. Primitive spinel compositions and whole-rock trace-element variations indicate at least two distinct, relatively fertile lherzolite sources for these two basalt types. Weak crustal zones associated with an old fracture system beneath MSH likely provide conduits for fast and isolated ascent of distinct batches of magma, bypassing the lower crustal mush zone. The eruption of the basalts through the upper crustal magma system and main edifice is consistent with an offset plumbing system suggested by geophysical data.

Chemical Geology, 2018

This paper aims at providing new insights into W-Sn ore-forming processes within one of the large... more This paper aims at providing new insights into W-Sn ore-forming processes within one of the largest granitic provinces in the world (Nanling Range, South China), which was emplaced during the Jurassic-Cretaceous period. The origin, composition and pressure-temperature conditions of fluids involved in the W-Sn ore-forming processes have been investigated by microthermometry, Raman spectroscopy, LA-ICPMS, hydrogen isotope analyses of fluid inclusions and oxygen isotope analyses of minerals from the Maoping and Piaotang W-Sn deposits. For each deposit, pre-(quartz), syn-(wolframite and cassiterite) and post-ore (quartz, topaz and fluorite) minerals were studied. In both deposits, the vast majority of fluid inclusions are aqueous with salinities between 0.0 and 12.6 wt. % equiv. NaCl and homogenization temperatures between 136 and 349 °C. A minor proportion (~5%) of inclusions observed in the ore-stage quartz from Maoping have aquo-carbonic compositions. For both deposits, four compositional groups are defined. Early quartz fluid inclusions are characterized by salinities between 0.4 and 9.0 wt. % equiv. NaCl, trapping temperatures between 150 and 350 °C, and pressures between 20 and 150 MPa. LA-ICPMS analyses of these fluid inclusions reveal a wide range of Na, K and Li concentrations, as well as relatively low metal contents (W < 40 ppm). Values of δ 18 O in quartz range from-3.6 to 5.3 ‰ VSMOW while δD values of the fluid inclusions range from-59 to-51 ‰ VSMOW. The salinity of fluid inclusions in wolframite, cassiterite, topaz and fluorite is between 2.4 and 11.2 wt. % equiv. NaCl, trapping temperatures are between 200 and 600 °C, and pressures range from 20 to 250 MPa. LA-ICPMS analyses of these fluid inclusions reveal higher concentrations of Na, K and Li as well as Cs and metals (e.g. between 10 and 220 ppm W). Values of δ 18 O in wolframite, cassiterite, topaz and fluorite crystals range from-3.0 to 3.3 3 ‰ VSMOW while δD values of fluid inclusions in these mineral phases range from-78 to-72 ‰ VSMOW. At Piaotang, fluid inclusions in wolframite as well as in post-ore quartz and fluorite have salinities of 5.6 to 12.6 wt.% eq. NaCl, trapping temperatures between 150 and 400 °C and pressures of 20 to 150 MPa. LA-ICPMS analyses of these fluid inclusions reveal similar compositions to early quartz fluid inclusions. Values of δ O in wolframite and quartz crystals range from-0.8 to 5.2 ‰ VSMOW, while the δD values of fluid inclusions range from-66 to-62 ‰ VSMOW. Collectively, the data suggest the involvement of four aqueous fluid end-members, mixed episodically in the mineralization process: (A) a low-salinity, low-temperature, metal-poor, low-δ 18 O, low-δD fluid derived from meteoric water; (B) a high-salinity, high-temperature, metal-poor, high-δ 18 O, low-δD fluid derived from a differentiated peraluminous granitic magma; (C) a high-salinity, high-temperature, metal-rich, lower δD magmatic fluid derived from a more differentiated peraluminous granitic magma; and (D) a high-salinity, hightemperature, metal-rich, high-δ 18 O, low-δD magmatic fluid. This study shows that multiple fluids with distinct magmatic and meteoric origins were involved in the formation of these W-Sn deposits and that the dilution of metal-bearing magmatic fluids by meteoric fluids was probably the main driver for ore deposition. The common fluid history of the two deposits studied, as well as similarities with other deposits in the Jiangxi province, points towards common ore-forming processes at the regional scale.

$Research paper thumbnail of Syn-orogenic fluid flow in the Jaca basin (south Pyrenean fold and thrust belt) from fracture and vein analyses$

Gondwana Research, 2017

New investigations in the Nanpanjiang Basin indicate that the onset of the iconic microbialites a... more New investigations in the Nanpanjiang Basin indicate that the onset of the iconic microbialites associated with the Paleozoic-Mesozoic boundary was Early Triassic in age. Bathymetry (water agitation, oxygenation, light penetration) and clastic load are shown to have exerted a direct control on the growth of microbialites. Carbonate supersaturation is also required for the deposition of the microbialites. Bathymetric control is further corroborated by the topographic inheritance of a latest Permian pull-apart basin into Early Triassic times, with a distribution of basal Early Triassic microbialites (BETM) restricted to uplifted blocks. This control is also reflected by the accumulation of carbonaceous black shales in adjacent troughs. The geographically most extensive Nanpanjiang BETM bloomed on a large NW-SE trending uplifted block exceeding 12,000 km2 (Luolou Platform) centered on northwestern Guangxi. Post-Triassic displacements along the Youjiang Fault obscure the paleogeographic relation of BETM exposed west of this fault. Triassic foraminifers occur in the basal most BETM episode, which is locally bracketed by high-energy grainstones made of reworked Permian foraminifers. Therefore, the Permian-Triassic boundary (PTB) is within the unconformity that separates the Late Permian Heshan Fm. from the basal most BETM. Where accommodation space was sufficient, up to five event surfaces are associated with the unconformity. Microfacies analysis supports chemical dissolution but did not reveal evidence for subaerial erosion, although intercalated grainstone made of Permian foraminifers indicate reworking. Chemical dissolution and mechanical erosion both conceivably contributed to the genesis of the unconformity. The upward shift from tabulated to domical microbial build-ups is accompanied by accumulation of coquinoid lenses between domes, which indicates deepening of the Luolou Platform BETM. The main drowning resulting from both regional tectonic subsidence and a global sea-level rise led to the cessation of the BETM that were buried under predominant fine siliciclastics. Any concomitant change in sea water chemistry appears unlikely.

Chemical Geology, 2017

Monazite can record several episodes of fluid/rock interaction within a single grain. Coupled in ... more Monazite can record several episodes of fluid/rock interaction within a single grain. Coupled in situ determination of age and oxygen isotope composition by SIMS (Secondary Ions Mass Spectrometer) may characterize such events. Yet, monazite reference materials for oxygen isotope analyses are scarce. Ion probe (CAMECA IMS 1280) and laser fluorination measurements of δ 18 O values from four monazites are presented. Monazites (YREEPO 4) with variable cheralite [CaTh(PO 4) 2 ] and huttonite (ThSiO 4) substitutions, which span a wide compositional range covering most magmatic and metamorphic, as well as hydrothermal monazites were selected. Three monazites, Moacyr, Manangoutry and UNIL-Mnz1, have a homogeneous chemical (determined by electron microprobe analysis and back-scattered imaging) and oxygen isotopic composition with uncertainties (2 SD) in the range of 0.3 to 0.4 ‰ for ion probe measurements.These three samples are thus potentially suitable as reference materials, and sample UNIL-Mnz1 is available for inter-laboratory comparison. Sample UNIL-Mnz2 is less homogeneous, but it is still useful for internal monitoring. Uncertainties (2 SD) on the ion probe data are in the range of 0.5 to 0.6 ‰.

Contributions to Mineralogy and Petrology, 2017

and newly formed synkinematic mineralization) in the Picde-Port-Vieux thrust fault zone (Pyrenees... more and newly formed synkinematic mineralization) in the Picde-Port-Vieux thrust fault zone (Pyrenees, Spain). We demonstrate that two geochemically contrasted rocks have been transformed by fluid flow under low-grade metamorphism conditions during thrusting. The hanging-wall Triassic red pelite was locally bleached, while the footwall Cretaceous dolomitic limestone was mylonitized. The results suggest that thrusting was accompanied by a dynamic calcite recrystallization in the dolomitic limestone as well as by leaching of iron via destabilization of iron oxides and phyllosilicate crystallization in the pelite. Geochemical and physical changes highlighted in this study have strong implications on the understanding of the thrust behavior (tectonic and hydraulic), and improve our knowledge of fluid-rock interactions in open fluid systems in the crust.

Swiss Journal of Geosciences, 2016

An innovative multidisciplinary approach was used on quartz-calcite veins that crosscut pebbles o... more An innovative multidisciplinary approach was used on quartz-calcite veins that crosscut pebbles of several lithologies from the French South Alpine Foreland Basin to discern the source of detrital sediments. Microthermometric results indicate that inclusions contain low to moderate salinity (0.9-9.8 wt% eq. NaCl) fluids. Oxygen and carbon isotope compositions of quartz and calcite (d 18 O mean at ?24.1 and ?24.7 % respectively (V-SMOW) and d 13 C from-1.1 to ?2.0 % (V-PDB)) are comparable with the composition of their host rocks (d 18 O from ?17 to ?24.3 % and d 13 C from-4 to ?1.4 %). The calculated d 18 O and d 13 C values of the fluid trapped in quartz and calcite range from ?9.3 to ?21.9 %, and from-2.6 to ?4.1 % respectively. These data suggest isotopic buffering of the fluid by the host rocks. Fluid trapping conditions were 105-185 MPa and 175-310°C. Using a lithostatic gradient, the conditions of fluid entrapment correspond to a depth of vein formation from 4 to 7 km. Petrographic and geochemical data obtained on the host rocks, their veins and fluid inclusions suggest that the source of the conglomerates is the inner part of the Alps rather than reliefs surrounding the foreland basin. The study of fluid inclusions in veins provides a powerful and innovative approach to link the production of detrital sediments with tectonic events, to trace the provenance of conglomerates and to reconstruct the regional geometry of the drainage system.

Mineralium Deposita, 2016

Willemite (Zn 2 SiO 4) usually reported in hypogene non-sulfide deposits is described as the main... more Willemite (Zn 2 SiO 4) usually reported in hypogene non-sulfide deposits is described as the main ore mineral in the carbonate-hosted Bou Arhous zinc deposit. This deposit is located in the High Atlas intracontinental range that formed during the Tertiary. Based on a set of microscopic observations, it was possible to establish that willemite replaces primary sphalerite. On the basis of cathodoluminescence imaging, three successive generations of willemite are distinguished, with evidence of dissolution-reprecipitation processes. Willemite is also variably enriched in Ge (up to 1000 ppm), while Ge contents lower than 100 ppm are reported in the primary sulfide minerals. Depending on the willemite generation, this substitution was positively or negatively correlated to the Zn-Pb substitution. According to the nature of zoning (sector versus oscillatory), the incorporation of Ge was either controlled by crystallographic factors or by the nature of the mineralizing fluids. Willemite is associated with other oxidation-related mineral species, like cerussite (PbCO 3) but is not in isotopic equilibrium and therefore not considered to be cogenetic. Oxygen isotope compositions support the formation of willemite at temperatures below 130°C, from mixed meteoric and deeper, hydrothermal fluids. The formation of the High Atlas Belt during the Tertiary has contributed to the exhumation of the sulfide minerals and the development of vertical conduits for percolation of meteoric water and ascending hydrothermal fluids. In addition to a local contribution of silicate minerals of the host limestone, hydrothermal fluids probably transported Si and Ge that are incorporated in willemite.

Contributions to Mineralogy and Petrology, 2012

The chemical and isotopic compositions of clay minerals such as illite and chlorite are commonly ... more The chemical and isotopic compositions of clay minerals such as illite and chlorite are commonly used to quantify diagenetic and low-grade metamorphic conditions, an approach that is also used in the present study of the Monte Perdido thrust fault from the South Pyrenean fold-and-thrust belt. The Monte Perdido thrust fault is a shallow thrust juxtaposing upper Cretaceous-Paleocene platform carbonates and Lower Eocene marls and turbidites from the Jaca basin. The core zone of the fault, about 6 m thick, consists of intensely deformed clay-bearing rocks bounded by major shear surfaces. Illite and chlorite are the main hydrous minerals in the fault zone. Illite is oriented along cleavage planes while chlorite formed along shear veins (\50 lm in thickness). Authigenic chlorite provides essential information about the origin of fluids and their temperature. d 18 O and dD values of newly formed chlorite support equilibration with sedimentary interstitial water, directly derived from the local hanging wall and footwall during deformation. Given the absence of largescale fluid flow, the mineralization observed in the thrust faults records the P-T conditions of thrust activity. Temperatures of chlorite formation of about 240°C are obtained via two independent methods: chlorite compositional thermometers and oxygen isotope fractionation between cogenetic chlorite and quartz. Burial depth conditions of 7 km are determined for the Monte Perdido thrust reactivation, coupling calculated temperature and fluid inclusion isochores. The present study demonstrates that both isotopic and thermodynamic methods applied to clay minerals formed in thrust fault are useful to help constrain diagenetic and low-grade metamorphic conditions.

Palaeogeography, Palaeoclimatology, Palaeoecology, Nov 1, 2006

A differentiated reconstruction of palaeolimnologic,-environmental, and-climatic conditions is pr... more A differentiated reconstruction of palaeolimnologic,-environmental, and-climatic conditions is presented for the Middle Miocene long-term freshwater lake (14.3 to 13.5 Ma) of the Steinheim basin, on the basis of a combined C, O, and Sr isotope study of sympatric skeletal fossils of aquatic and terrestrial organisms from the lake sediments. The oxygen isotope composition for lake water of the Steinheim basin (δ 18 O H2O = + 2.0 ± 0.4‰ VSMOW, n = 6) was reconstructed from measurements of δ 18 O PO4 of aquatic turtle bones. The drinking water calculated from the enamel of large mammals (proboscideans, rhinocerotids, equids, cervids, suids) has δ 18 O H2O values (δ 18 O H2O = − 5.9 ± 1.7‰ VSMOW, n = 31) typical for Middle Miocene meteoric water of the area. This δ 18 O H2O value corresponds to a mean annual air temperature (MAT) of 18.8 ± 3.8°C, calculated using a modern-day δ 18 O H2O-MAT relation. Hence, large mammals did not use the lake water as principal drinking water. In contrast, small mammals, especially the then abundant pika Prolagus oeningensis drank from 18 O-enriched water sources (δ 18 O H2O = + 2.7 ± 2.3‰ VSMOW, n = 7), such as the lake water. Differences in Sr and O isotopic compositions between large and small mammal teeth indicate different home ranges and drinking behaviour and support migration of some large mammals between the Swabian Alb plateau and the nearby Molasse basin, while small mammals ingested their food and water locally. Changes in the lake level, water chemistry, and temperature were inferred using isotopic compositions of ostracod and gastropod shells from a composite lake sediment profile. Calcitic ostracod valves (Ilyocypris binocularis; δ 18 O = + 1.7 ± 1.2‰ VPDB, δ 13 C = −0.5 ± 0.9‰, VPDB, n = 68) and aragonitic gastropod shells (Gyraulus spp.; δ 18 O = + 2.0 ± 1.3‰ VPDB, δ 13 C = −1.1 ± 1.3‰ VPDB, n = 89) have δ 18 O and δ 13 C values similar to or even higher than those of marine carbonates. δ 13 C values of the biogenic carbonates parallel lake level fluctuations while δ 18 O values scatter around + 2 ± 2‰ and reflect the short term variability of meteoric water inflow vs. longer term evaporation. 87 Sr/ 86 Sr ratios of aragonitic Gyraulus spp. gastropod shells parallel the lake level fluctuations, reflecting variable inputs of groundwater and surface waters. Using a water δ 18 O H2O value of + 2.0‰ VSMOW, water temperatures calculated from skeletal tissue δ 18 O values of ostracods are 16.7 ± 5.0°C, gastropods 20.6 ± 5.6°C, otoliths 21.8 ± 1.4°C, and fish teeth 17.0 ± 2.7°C.

AGU Fall Meeting Abstracts, Dec 1, 2005

The Tertiary circum-Alpine Molasse sediments were deposited during major periods of Alpine tecton... more The Tertiary circum-Alpine Molasse sediments were deposited during major periods of Alpine tectonism but also at a time of large global climatic change. They are well suited to study the effects of tectonic forcing on climate, because the sediments were deposited in marginal basins, partly to completely isolated from other major oceanic basins. Hence, a comparison of the past climatic and oceanographic evolution indicated by the sediments to those on a global scale, does allow for a qualitative evaluation of the relationship between tectonism and regional climate. Much is known about the geological-geochronological framework of alpine tectonism, including associated erosional rates and sediment volumes. Estimates of changes in paleoelevation and its direct influence on climate have, however, been less well constrained. Three independent lines of evidence indicate significant altitudes of the Alps during the Miocene: 1) H isotope compositions of clay minerals, formed as weathering products and subsequently deposited as part of the Alpine Molasse, have deltaD reaching values as low as -970/00. 2) O isotope compositions of retrograde metamorphic vein and fissure quartz and H isotope composition of its included fluids have delta18O values as low as -3.50/00 and deltaD values of -1400/00, respectively. 3) ``Exotic" shark teeth from Swiss Upper Marine Molasse sediments that have delta18O values (VSMOW) around 110/00 (n=2), values unlike those from other teeth of the same locality (20.7 to 21.80/00; n=6), but for which the REE patterns support the same diagenetic history, hence supporting a freshwater formation of the low delta18O teeth (also supported by distinct Sr isotope compositions). Using these three approaches as a basis for estimating the isotopic composition of past precipitation and applying the present-day altitude effects on the compositions, it can be concluded that the Miocene Alps had mean altitudes of about 1500 to 2000 m, that is elevations similar to those of today. Paleoclimatic reconstructions from North Alpine Molasse sediments are based on oxygen isotope compositions of fossil mammalian tooth enamel for freshwater molasse deposits, and shark teeth, marine ostracoda, foraminifera, and mammalian phosphatic fossils for the Upper Marine Molasse deposits. The delta18O values (VPDB) of carbonate in phosphate from Oligocene and Miocene large mammal teeth (n=270), for example, vary over a large range from -11.90/00 to -0.50/00, but these variations parallel the composite O isotope curve of Tertiary benthic foraminifera, thus reflecting major global climatic changes such as the Late Oligocene warming, Mid-Miocene climate optimum, and Middle to Late Miocene cooling trends. The delta18O values (VSMOW) of phosphate in shark teeth (19.8 to 23.30/00; n=130) from Miocene marine molasse sediments as well as those of ostracods and foraminifera from these sediments all have variations that parallel those of composite curves for global changes. Collectively, the data support a Neogene paleogeography with a high mountain belt adjacent to marginal marine or freshwater depositional basins but with a regional climate, at least for the northern Molasse realm, that was strongly coupled to the global climate. The Alps thus appear not have influenced the local climate and/or atmospheric circulation patterns significantly.