We present strontium (Sr) isotope ratios that, unlike traditional 87 Sr/ 86 Sr data, are not normalized to a fixed 88 Sr/ 86 Sr ratio of 8.375209 (defined as d 88/86 Sr = 0 relative to NIST SRM 987). Instead, we correct for isotope fractionation during mass spectrometry with a 87 Sr-84 Sr double spike. This technique yields two independent ratios for 87 Sr/ 86 Sr and 88 Sr/ 86 Sr that are reported as ( 87 Sr/ 86 Sr*) and (d 88/86 Sr), respectively. The difference between the traditional radiogenic ( 87 Sr/ 86 Sr normalized to 88 Sr/ 86 Sr = 8.375209) and the new 87 Sr/ 86 Sr* values reflect natural mass-dependent isotope fractionation. In order to constrain glacial/interglacial changes in the marine Sr budget we compare the isotope composition of modern seawater (( 87 Sr/ 86 Sr*, d 88/86 Sr) Seawater ) and modern marine biogenic carbonates (( 87 Sr/ 86 Sr*, d 88/86 Sr) Carbonates ) with the corresponding values of river waters (( 87 Sr/ 86 Sr*, d 88/86 Sr) River ) and hydrothermal solutions (( 87 Sr/ 86 Sr*, d 88/86 Sr) HydEnd ) in a triple isotope plot. The measured ( 87 Sr/ 86 Sr*, d 88/86 Sr) River values of selected rivers that together account for $18% of the global Sr discharge yield a Sr flux-weighted mean of (0.7114 (8), 0.315(8)&). The average ( 87 Sr/ 86 Sr*, d 88/86 Sr) HydEnd values for hydrothermal solutions from the Atlantic Ocean are (0.7045(5), 0.27(3)&). In contrast, the ( 87 Sr/ 86 Sr*, d 88/86 Sr) Carbonates values representing the marine Sr output are (0.70926(2), 0.21(2)&). We estimate the modern Sr isotope composition of the sources at (0.7106(8), 0.310(8)&).The difference between the estimated ( 87 Sr/ 86 Sr*, d 88/86 Sr) input and ( 87 Sr/ 86 Sr*, d 88/86 Sr) output values reflects isotope disequilibrium with respect to Sr inputs and outputs. In contrast to the modern ocean, isotope equilibrium between inputs and outputs during the last glacial maximum (10-30 ka before present) can be explained by invoking three times higher Sr inputs from a uniquely "glacial" source: weathering of shelf carbonates exposed at low sea levels. Our data are also consistent with the "weathering peak" hypothesis that invokes enhanced Sr inputs resulting from weathering of postglacial exposure of abundant fine-grained material.

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Seismological data from recent subduction earthquakes suggest that megathrust earthquakes induce transient stress changes in the upper plate that shift accretionary wedges into an unstable state. These stress changes have, however, never been linked to geological structures preserved in fossil accretionary complexes. The importance of coseismically induced wedge failure has therefore remained largely elusive. Here we show that brittle faulting and vein formation in the palaeo-accretionary complex of the European Alps record stress changes generated by subduction-related earthquakes. Early veins formed at shallow levels by bedding-parallel shear during coseismic compression of the outer wedge. In contrast, subsequent vein formation occurred by normal faulting and extensional fracturing at deeper levels in response to coseismic extension of the inner wedge. Our study demonstrates how mineral veins can be used to reveal the dynamics of outer and inner wedges, which respond in opposite ways to megathrust earthquakes by compressional and extensional faulting, respectively.

The isotopic composition of Phanerozoic marine sediments provides important information about changes in seawater chemistry. In particular, the radiogenic strontium isotope ( 87 Sr/ 86 Sr) system is a powerful tool for constraining plate tectonic processes and their influence on atmospheric CO 2 concentrations. However, the 87 Sr/ 86 Sr isotope ratio of seawater is not sensitive to temporal changes in the marine strontium (Sr) output flux, which is primarily controlled by the burial of calcium carbonate (CaCO 3 ) at the ocean floor. The Sr budget of the Phanerozoic ocean, including the associated changes in the amount of CaCO 3 burial, is therefore only poorly constrained. Here, we present the first stable isotope record of Sr for Phanerozoic skeletal carbonates, and by inference for Phanerozoic seawater (δ 88/86 Sr sw ), which we find to be sensitive to imbalances in the Sr input and output fluxes. This δ 88/86 Sr sw record varies from ~0.25‰ to ~0.60‰ (vs. SRM987) with a mean of ~0.37‰. The fractionation factor between modern seawater and skeletal The oceanic net carbonate flux of Sr (F(Sr) carb ) varied between an output of -4.7x10 10 mol/Myr and an input of +2.3x10 10 mol/Myr with a mean of -1.6x10 10 mol/Myr.On time scales in excess of 100Myrs the F(Sr) carb is proposed to have been controlled by the relative importance of calcium carbonate precipitates during the "aragonite" and "calcite" sea episodes. On time scales less than 20Myrs the F(Sr) carb seems to be controlled by variable combinations of carbonate burial rate, shelf carbonate weathering and recrystallization, ocean acidification, and ocean anoxia. In particular, the Permian/Triassic transition is marked by a prominent positive δ 88/86 Sr sw -peak that reflects a significantly enhanced burial flux of Sr and carbonate, likely driven by bacterial sulfate reduction (BSR) and the related alkalinity production in deeper anoxic waters. We also argue that the residence time of Sr in the Phanerozoic ocean ranged from ~1Myrs to ~20Myrs.