Abstract: Orbital Cyclostratigraphy Above and Below the Cretaceous-Tertiary Boundary

W. G. H. Z. Ten Kate, R. A. Sprenger

We investigated the rhythms of pelagic limestone-marl successions in Spain and present evidence of their orbital control. Three sections were surveyed and sampled in detail: Agost and Relleu in the province of Alicante, and Zumaya in the Basque country. The carbonate content of 2779 samples was determined and used as a proxy to determine cyclicities.

Conventional paleomagnetic and micropaleontologic datum planes are few and show the usual uncertainties. Power spectra based on the few reliable datum planes available are unstable. In an unconventional way more datum planes were created: by visual correlation of the local maxima and minima of the carbonate curves to those of the relevant part of the theoretical eccentricity curve of Berger, 1978 (Contribution de l'institut d'astronomie et geophysique G. Lemaitre, v.18, p.1-48). Such method has merit because the eccentricity parameters are considered rather stable throughout the Phanerozoic. The result supports the thesis that the carbonate rhythmicity at Agost, Relleu and Zumaya is orbitally controlled. The superposition of what we interpret as the 100,000 yr and 400,000 yr cycles of eccentricity provides a cyclostratigraphic framework with a resolution of better than 50 000 years. The age of the K/T boundary is estimated at 64.56 million years.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994