Multifactorial control on deposition of epicontinental hemi-pelagic carbonates during the earliest Kimmeridgian (Prebetic Zone, southern Spain)

Abstract

Two successions of marly limestone–limestone couplets, occasionally with significant intercalations of marls, have been investigated in the lower Kimmeridgian (Platynota Zone) in the central sector of the Prebetic Zone (southern Spain). The aim of this paper is to identify and evaluate possible interactions between global signals (orbital fluctuations, climate and eustasy) and local–regional tectonics forcing deposition and ecospace on an epicontinental shelf. High-resolution ammonite biostratigraphy, together with sedimentological, stratigraphical, mineralogical data, and ecostratigraphic interpretations, were re-examined to provide evidence for the combined action of tectonics, eustasy and insolation fluctuations on sedimentation in two sections which clearly differ in stratal pattern, both in the average thickness of limestone beds and in the frequency and character of marl intercalations. The detailed analysis of stratal patterns was used to identify and calibrate the influence of the different factors investigated. The identification of significant bedding planes in the sections studied enabled the recognition of eight bundles of beds (major cycles). The analysis and comparison of their internal structure, together with the information about tectonic and eustatic influences, enabled us to interpret the lower part of the sections (bundles 1 and 2) as being forced by interactions between orbital signals and tectonics, the upper part (bundles 6, 7 and 8) as being caused by interactions between orbital signals and eustasy, and the middle part (bundles 3, 4 and 5) as being related mainly to orbital forcing.