CONSTRAINING ORBITAL SOLUTIONS USING THE CRETAEOUS GEOLOGICAL RECORD

Cyclostratigraphy is widely used for constructing high-resolution geological time scales. Due to the chaotic behavior of the Solar System, however, the theoretical astronomical solution for the geologic past is only valid to ~50 Ma. In order to better constrain the theoretical orbital solutions for the past and test for chaotic transitions in Solar System behavior older than 50Ma, this study compiles two previously studied orbitally-forced geological records spanning 82-97 Ma from the Western Interior Seaway (USA). The new composite cyclostratigraphy: (1) provides an astronomically-calibrated high-resolution carbon isotope record from 82-97 Ma, (2) quantifies the influence of the Earth-Mars secular resonance, which is a sensitive indicator of Solar System chaos, and (3) indicates a chaotic transition of the Earth-Mars secular resonance from the 2.4 Myr cycle to the 1.2 Myr cycle, and back again, within the 82-97 Ma study interval.