High mountains in a zone of extended crust: Insights into the Neogene-Quaternary topographic development of northeastern Iberia

Article Abstract:

There is evidence that much of the current configuration of the northeastern Iberian Peninsula is the result of Neogene-Quaternary opening of the western Mediterranean basins after the Pyrenean orogeny. There is much research on rifted margins clarifying the connection between rift structures and geomorphic features such as elevated or incised topography. New research has sought to document the lateral extent and geometry of elevated and incised topography. Westward migration of extension and volcanism into the Iberian Peninsula may be the result of migration of a thermal anomaly or of the mechanical removal of the mantle lithosphere.

Iberian Peninsula

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Stress magnitude, strain rate, and rheology of extended middle continental crust inferred from quartz grain sizes in the Whipple Mountains, California

Article Abstract:

The theoretically derived and experimentally determined microstructural piezometry of the quartz grain sizes in the Whipple Mountains, California, reveal the stress magnitude, strain rate and rheology of the extended middle continental crust. Mylonitization occurs at differential stresses of approximately 40-150 MPa and at a temperature not more than 500 degrees centigrade. The maximum shear stresses during mylonitization are approximately 20-75 MPa. The strain rates are faster than 10 to the -14th power per second. Mechanical conditions in the middle and lower crusts are also revealed.

Analysis, Environmental aspects, California, Strains and stresses, Stresses (Materials), Quartz, Mylonite

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Ar/Ar geochronology of ultrahigh-pressure metamorphism in central China

Article Abstract:

Analysis of 21 Dabie hornblende, phengite, and biotite samples of metamorphic rock from the Dabie Shan of China by the 40Ar/39Ar method suggests that cooling from optimum metamorphic temperatures to nearly 300 degrees took place between about 206 and 178 Ma and the widespread Cretaceous ages show reheating by a post-ultrahigh-pressure magnetic/extensional episode. Dabie ultrahigh pressure metamorphic rocks have temporary relation with blueschist-facies rocks farther west in the suture zone.

China, Metamorphism (Geology), Geological time, Geochronology

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