CONTRIBUTION OF THE NEWARK BASIN CORING PROJECT TO ASTROCHRONOLOGY AND CELESTIAL MECHANICS

The Newark Basin Coring Project (NBCP) was designed to core the entire Triassic age sedimentary record of the Newark continental rift basin of NY, NJ, and PA. Funded by the Continental Dynamics program of NSF, with AMOCO Production Company and Longyear as contractors, the project recovered 6770 m of continuous from seven sites in New Jersey from 1990-1993. An offset drilling method was used taking advantage of the deeply eroded half-graben structure of the basin. The nearly 25% overlap zones between each of the stratigraphically adjacent cores was used to test lateral correlations, scale the cores to one another, and combine them in a 4,660 m thick composite section. This composite shows that most of the sedimentary section consists of a hierarchy of sedimentary cycles of Milankovitch origin including all of the main precession-related periods. Evolutive Fourier and Wavelet analysis clearly shows that periodicities in thickness are remarkably stationary, spanning three orders of magnitude, with few changes in long-term accumulation rates.

With 24 m.y. of the Newark basin record calibrated by Milankovitch cyclicity, and with 47 major magnetic polarity zones, the NBCP composite record is the basis for an astronomically tuned geomagnetic time scale for the Late Triassic and earliest Jurassic. First proposed in 1995, the Newark basin AGPTS has been enhanced with data from the Taylorville and Hartford basins that modify the oldest and youngest parts of the record extending the time scale into the Sinemurian of the Early Jurassic, and in turn is correlated with polarity stratigraphies of Tethyian marine sequences permitting extension of marine stages, substages, and zones into continental sequences and vice versa globally.

The precession-related frequencies revealed in the NBCP cores generally follow predicted values, with the exception of the unpredictable longest period cycles related to Earth and Mars, the periods of which (1.75 and 3.5 m.a.) that differ significantly from the modern periods because of chaotic diffusion of the Solar System. This is the first calibration of the behavior of these cycles deviating from modern values and is a necessary first step in the future construction of an astronomically tuned time scale for the Phanerozoic.