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Gelnhausen, Germany

Mix H.T.,Santa Clara University | Mix H.T.,Stanford University | Ibarra D.E.,Stanford University | Mulch A.,Senckenberg Biodiversity and Climate Research Center | And 4 more authors.
Bulletin of the Geological Society of America | Year: 2016

Despite broad interest in determining the topographic and climatic histories of mountain ranges, the evolution of California's Sierra Nevada remains actively debated. Prior stable isotope-based studies of the Sierra Nevada have relied primarily on hydrogen isotopes in kaolinite, hydrated volcanic glass, and leaf n-alkanes. Here, we reconstruct the temperature and elevation of the early Eocene Sierra Nevada using the oxygen isotope composition of kaolinitized granite clasts from the ancestral Yuba and American Rivers that drained the windward (Pacific) flank of the Sierra Nevada. First, we evaluated the possible contributions of hydrogen isotope exchange in kaolinite by direct comparison with oxygen isotope measurements. Next, we utilized differences in the hydrogen and oxygen isotope fractionation in kaolinite to constrain early Eocene midlatitude weathering temperatures. Oxygen isotope geochemistry of in situ kaolinites indicates upstream (eastward) depletion of 18O in the northern Sierra Nevada. The δ18O values, ranging from 11.4‰ to 14.4‰ at the easternmost localities, correspond to paleoelevations as high as 2400 m when simulating the orographic precipitation of moisture from a Pacific source using Eocene boundary conditions. This result is consistent with prior hydrogen isotope studies of the northern Sierra, but oxygen isotope-based paleoelevation estimates are systematically ~500-1000 m higher than those from hydrogen-based estimates from the same samples. Kaolinite geothermometry from 16 samples produced early Eocene weathering temperatures of 13.0-36.7 °C, with an average of 23.2 ± 6.4 °C (1σ). These kaolinite temperature reconstructions are in general agreement with paleofloral and geochemical constraints from Eocene California localities and climate model simulations. Our results confirm prior hydrogen isotope-based paleoelevation estimates and further substantiate the existence of a hot and high Eocene Sierra Nevada. © 2015 Geological Society of America. Source


McFadden R.R.,Salem State University | Mulch A.,Senckenberg Research Institutes | Mulch A.,Goethe University Frankfurt | Teyssier C.,University of Minnesota | Heizler M.,New Mexico Institute of Mining and Technology
Lithosphere | Year: 2015

The relationship between microstructure and fluid flow traced by hydrogen isotope ratios (δD) is examined within the Wildhorse detachment system of the Pioneer metamorphic core complex in south-central Idaho. Within the detachment footwall, 100-m-thick mylonitic quartzite containing minor white mica and K-feldspar displays a NW-trending stretching lineation and consistent top-to-the-NW sense of shear criteria. Microstructures within the detachment footwall comprise two groups: quartz ribbons and relict quartz grains flattened within the foliation, with porphyroclastic white mica fish; and intensely deformed and recrystallized quartz with high-aspect-ratio white mica arranged within C' shear bands. White mica dD values are highly negative and cluster around -145‰ in high-aspect-ratio white mica and around -120‰ in porphyroclastic white mica fish. The most negative values are interpreted to reflect interaction with meteoric fluids from a high-elevation catchment (3000-4000 m), and the less negative values are interpreted to represent incomplete hydrogen isotope exchange between the meteoric fluid and the pre-extensional metamorphic fluid dD values in the white mica porphyroclasts. A suite of tightly clustered 40Ar/39Ar ages from synkinematic white mica in the detachment footwall dates deformation, recrystallization, fluid-rock interaction, and therefore the presence of high topography at 38-37 Ma; these ages are consistent with the cooling/exhumation history of the high-grade core of the Pioneer metamorphic core complex in the late Eocene. The 38-37 Ma 40Ar/39Ar ages are substantially younger than previously published ages of high topography in British Columbia to the north (49-47 Ma), in line with the hypothesis that high topography propagated from north to south in the northern segment of the North American Cordillera through Eocene time. © Geological Society of America. Source


Eronen J.T.,Senckenberg Research Institutes | Eronen J.T.,University of Helsinki | Janis C.M.,Brown University | Chamberlain C.P.,Stanford University | And 2 more authors.
Proceedings of the Royal Society B: Biological Sciences | Year: 2015

Patterns of late Palaeogene mammalian evolution appear to be very different between Eurasia and NorthAmerica. Around the Eocene–Oligocene (EO) transition global temperatures in the Northern Hemisphere plummet: following this, European mammal faunas undergo a profound extinction event (the Grande Coupure), while in North America they appear to pass through this temperature event unscathed. Here, we investigate the role of surface uplift to environmental change and mammalian evolution through the Palaeogene (66–23 Ma). Palaeogene regional surface uplift in North America caused large-scale reorganization of precipitation patterns, particularly in the continental interior, in accord with our combined stable isotope and ecometric data. Changes in mammalian faunas reflect that these were dry and high-elevation palaeoenvironments. The scenario of Middle to Late Eocene (50–37 Ma) surface uplift, together with decreasing precipitation in higher-altitude regions of western North America, explains the enigma of the apparent lack of the large-scale mammal faunal change around the EO transition that characterized western Europe. We suggest that North American mammalian faunas were already pre-adapted to cooler and drier conditions preceding the EO boundary, resulting from the effects of a protracted history of surface uplift. © 2015 The Author(s) Published by the Royal Society. All rights reserved. Source


Frosch C.,Senckenberg Research Institutes | Dutsov A.,Balkani Wildlife Society | Georgiev G.,Regional Environmental Inspectorate of Ministry of Environment and Water Smolyan 16 | Nowak C.,Senckenberg Research Institutes | Nowak C.,Biodiversity and Climate Research Center
Forensic Science International: Genetics | Year: 2011

Fatal bear attacks on humans are extremely rare across Europe. Here we report a fatal bear attack on a man in Bulgaria. We used microsatellite analysis for bear individualization based on hair samples found near the man's corpse. The genetic profile of the killing bear was compared to that of a bear shot three days later near the killing scene. Our results show that the wrong bear has been shot. Shortly after our results were reported a second person was attacked by a bear nearby. This case documents the importance of forensic DNA analysis following severe wildlife attacks in order to improve wildlife management actions in regions were direct human-bear conflicts are likely to happen. © 2011 Elsevier Ireland Ltd. All rights reserved. Source

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