Introduction

At present members of the Earth Surface Processes Group at Hannover concentrate on three broad areas of research:

1) The feedbacks between the topographic evolution of Cenozoic mountain ranges and climate. We establish continental stable isotope records of precipitation patterns that reflect reliable archives of past climate. At current we focus on field sites in the western United States, Turkey,and  the Alps.

2) Fluid migration in all levels of continental crust and its relationship to the geodynamic processes that govern mountain building and development of large continental plateaus. Current field areas include the metamorphic core complexes of the western United States, Papua New Guinea, and the Swiss Alps.

3) Long-term Cenozoic climate change. Isotope records of individual time intervals in the past that were characterized by high atmospheric CO2 levels provide valuable insight into the rates and magnitudes of future climate change. One of our goals is to characterize teleconnections and feedbacks between oceanic and terrestrial climate records.

1) Cenozoic Evolution of Topography in the North American Cordillera Recorded in Coupled Basin-Detachment Systems

Changes in paleotopography can be reconstructed using systematic changes in the stable isotopic composition of meteoric waters that occur during orographic ascent of air masses and passage over a mountain range. Currently our applications focus on:

Characterization of stable isotope patterns in intermontane basins of the North American Cordillera, the Turkish Plateau, the Alpine Molasse basin , and the foreland basins of the Bolivian Andes.

Surface elevation is one of the most important characteristics of Earth’s continental crust in that it reflects the distribution of mass and heat inside the Earth, controls drainage patterns and detrital recycling, and influences atmospheric currents and therefore climate Yet, paleoelevation is one of the most elusive parameters in the Earth’s paleorecord. Recent developments in paleoaltimetry studies are allowing a wide range of tectonic problems to be addressed. We currently conduct a paleoaltimetry analyses of the North American Cordillera, the Turkish Plateau, and the Bolivian Andes combining stable isotopic, structural, and sedimentological studies of metamorphic core complexes, their adjacent sedimentary basins, and various other surface records to reconstruct the Cenozoic paleoelevation of the major orogens and continental plateaus to test multiple hypotheses regarding the
driving forces of mountain building and subsequent extension.

With the advent of new methods to determine paleotopography of mountain belts we are beginning to better understand the relationships and feedbacks among topography, tectonics, and climate.  Stable isotope paleoaltimetry is based on the observation that precipitation and surface waters become depleted in 18O and D with increasing elevation. Once this “altitude effect” has been quantified quantitative bounds can be placed on the elevation of past mountain ranges.

In collaboration with C. Page Chamberlain (Stanford University), C. Teyssier (University of Minnesota), S.A. Graham (Stanford University), M. Wells (University of Nevada), M.A.Cosca (USGS), Mike Perkins (Utah), M. Strecker (Universität Potsdam)

2) Rates, Timing, and Compositions of Fluid Flow in orogen-scale brittle to ductile Shear Zones

1. determination of fluid flow patterns and their isotopic signature in ductile detachments
2. understanding the coupling between ductile flow in the crust, basin development and surface topography

Extensional mylonitic shear zones or detachment zones that separate rocks with completely different temperature-time-deformation histories are key tectonic features of metamorphic core complexes and orogenic belts in general.  Commonly, ductile detachment zones at depth are temporally and kinematically linked to brittle normal faults in the upper crust to form detachment systems responsible for tectonically-driven, rapid exhumation of lower plate rocks.

Extensional detachment systems channelize surface waters to depth where the isotopic fingerprint of such ancient surface waters can be picked up in shear zone minerals.

Mylonitic quartzite provides a perfect target for deepening our understanding of the driving forces and feedbacks that control fault and shear zone movements as the deformation behavior is relatively well known and microstructural and geochronologic data can be supplemented by results from stable isotope geochemistry and numerical flow models.

In order to adequately characterize the temporal, kinematic, and tectonic evolution of  we routinely use high-spatial resolution 40Ar/39Ar geochronology, oxygen isotope thermometry, and hydrogen isotopes as tracers for fluid flow.

Currently, we have started to integrate field and laboratory data with the results of numerical modelling of fluid flow in evolving extensional detachment systems.

Collaborators: C. Teyssier (University of Minnesota)
                        M.A. Cosca (USGS)
                        N. Mancktelow (ETH Zürich)
                        M. Person (Indiana University)

3) Long-term Cenozoic climate change

-currently in progress-
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