ABSTRACT

In order to understand the tectonic processes, which deform the Earth, it is important to know what long-term deformation rates are and how they vary through time. Typically, long chronologies of deformation have only coarse time resolution and evidence from many mountain belts suggests that deformation is discontinuous both spatially and temporally. In this study, climate signals driven by long-term variation in the Earth's orbit (Milankovitch cycles, Precession cyclicity every ~20,000 years, Obliquity cyclicity every ~40,000 years), are being used to provide high-resolution dating of sedimentary layers deposited atop a large, growing anticline, which developed in northern Spain (Jaca Basin) 42-36 million years ago. Growth strata, layers of rock deposited during deformation, provide a unique opportunity to unravel deformational and depositional processes of deforming landscapes and can provide exceptional time markers of deformation. This will be accomplished using structural, stratigraphic, and magnetic data from growth strata associated with the Pico del Aguila anticline, Spanish Pyrenees. Prolonged fold growth occurred in varying water depths and environments of deposition and was recorded by changes in growth strata thickness and orientation. As part of this study, the mesurement of stratigraphic sections and sampling of rocks for magnetic susceptibility, anisotropy of magnetic susceptibility, (rock magnetic proxies for orbitally driven climate variability) and remanent magnetization are being conducted. The climate signal is being analyzed by collaborative laboratory work and time series analysis. The characteristic remanent magnetization is being used to correlate the growth strata to the global magnetic polarity time scale, which provides an absolute date at eight specific horizons and the Milankovitch rhythms time other horizons every ~20,000 years. High-resolution Global Positioning System data, supported by UNAVCO, Inc., is being used to map individual beds in order to generate an equally high-resolution geometric reconstruction of the fold. Collectively, these measurements are permitting detailed reconstructions of deformation and providing novel insights into long-term deformation rates.

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