International Geologiical Congress - Oslo 2008


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HPS-05 Recent developments in the Geologic Timescale


An astronomical time scale for the mesozoic era


Linda Hinnov, Johns Hopkins University (United States)
James Ogg, Purdue University (United States)


We report on an ongoing project to assemble long and short term orbital-climate cycles recorded in stratigraphic data into a continuous 'Astronomical Time Scale' (ATS) for the Mesozoic Era. The goal is to extend the ATS, now virtually complete for the Cenozoic Era, to encompass the past quarter-billion years of Earth history. The detailed stratigraphy of the sedimentary successions, the astronomical target algorithms and the analytical tools that are used are being documented and stored in a public database system. Emphasis is placed on the goodness of fit of stratigraphic signals to astronomical models, duplication of interpreted records from different regions, and high-resolution calibration to geomagnetic polarity signatures and integrated bio- and chemostratigraphy. Numerical ages from the reconstructed ATS will be inter-calibrated with dating techniques (i.e., radioisotopes) in conjunction with the EARTHTIME Project. The results fulfill an ongoing initiative of the International Commission on Stratigraphy to develop a continuous, astronomically calibrated international Geologic Time Scale for the past 250 Ma. An ATS for the Mesozoic Era represents a major breakthrough in geoscientific research. Estimates of rates and magnitudes for a wide range of Earth system processes will be improved by at least an order of magnitude. Longstanding questions can be addressed in disciplines as far-ranging as astrodynamics, geodynamics, paleoclimatology, paleoceanography, plate tectonics, and biotic evolution.


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