|2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM|
|Paper No. 209-1|
|Presentation Time: 1:40 PM-2:00 PM|
Implications of the Geological Determination of “Grand Cycles” of the Milankovitch Band for Behavior of the Solar System
OLSEN, Paul, Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964-1000, email@example.com|
Attention has historically focused on the 21, 41, and 100 ky Milankovitch periods, but cycles of 405 ky and up to several million years are present in the orbital solutions. The latter I have previously termed "grand cycles" of the Milankovitch band. Laskar (1) has shown there is long-term chaotic evolution in planetary orbits that render grand cycles frequencies <1/405 ky unpredictable over deep time, especially the g4-g3 cycle with a present frequency of ~1/2.35 m.y. While Cenozoic records (2) lack observable change in this frequency, I have shown that early Mesozoic paleotropical lake level records (199-235 Ma) provide a "geological interferometer" revealing that g4-g3 had a frequency of 1/1.75 m.y., consistent with chaotic diffusion (3). Wavelet analysis shows this 1/1.75 m.y. frequency was stable over at least 25 m.y. The g1-g5 and g2-g1 frequencies are also present. The Triassic 1/1.75 m.y. frequency is consistent with multiple marine 206Pb/238U ash ages tied to the lacustrine records by magnetostratigraphy. Because the tropical lake sequences show no obliquity signal, their spectral properties can be used as a template to identify grand cycles in obliquity from contemporaneous higher latitude records. With obliquity records, s4-s3 can be determined, and through this the resonance state of the Earth-Mars system. If this can be done for the rest of the Jurassic and Cretaceous, the grand cycle "geological interferometer" will allow the development of a high-precision solution for the behavior of the Solar System over 235 million years and a robust test of general relativity derived from the quadrupole moment J2 of the Sun as has been noted by Laskar (1). References: 1, Laskar, 1999, Phil. Trans. R. Soc. Lond. A, 357:1735; 2, PŠlike et al., 2004, Geology 32: 929; 3, Olsen & Kent, 1999. Phil Trans. R. Soc. Lond. A, 357:1761.
2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM
General Information for this Meeting
|Session No. 209|
The Astronomically Forced Sedimentary Record: From Geologic Time Scales to Lunar-Tidal History
George R. Brown Convention Center: 361DE
1:30 PM-5:30 PM, Monday, 6 October 2008
Geological Society of America Abstracts with Programs, Vol. 40, No. 6, p. 282
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