The marl-limestone rhythmites from the Lower Kimmeridgian (Platynota Zone) of the central Prebetic and their relationship with variations in orbital parameters

Abstract

The origin of the rhythmic marl-limestone bedding recognized in Lower Kimmeridgian (Platynota Zone) succesions of the central Prebetic (Southern Spain) is interpreted. A detailed analysis was carried out on the basis of field observations and mathematical procedures of two sections characterized by the variable alternation of marly and limestone horizons. The study primarily reveals signs of a possible secondary imprint in the stratification. However, we conclude that this imprint cannot have been sufficiently important to cause the recorded stratification or significantly alter the existing primary bedding. The mathematical procedure applied to the thicknesses of the beds reveals the existence of different orders of cyclicity that are not recognizable in the field. We were able to date these cycles by detailed biostratigraphy and the application of Fourier/spectral analysis. The close relationship between the timing calculated for the marl-limestone rhythms recognized in the Lower Kimmeridgian (Platynota Zone) successions and the periodicity assumed for Milankovitch cycles has been shown for the first time in the Prebetic Zone and leads us to accept the influence of orbital variations on sedimentation in the sector that was studied. We have also been able to recognize the influence of local factors which determined differences in the depositional organization in the sections studied.