Suscetibilidade magnética em sequências carbonatadas silúricas da Ibéria: primeira aproximação

Abstract

Magnetic susceptibility studies (magnetostratigraphy) are a tool for correlating stratigraphic sequences of similar ages, especially for situations where biostratigraphy is not applicable or presents little precision in the range of ages that can be obtained from it. These studies are also used as a tool for the correlation of paleoclimate events on a regional or global scale. In this work, three Silurian sequences of the Iberian Peninsula were studied: Campanhó (Silurian, uncertain stage, Central Iberian Zone); Mós (Pridoli, Central Iberian Zone); and El Pintado (Pridoli, Ossa-Morena Zone). The main objective was to compare the magnetic susceptibility (K) variation profiles in these sequences to find similar patterns of variation and, tentatively, date the Campanhó limestones, which geological context is identical to that of the remaining sequences and which age has not yet been confirmed by other methods, namely by biostratigraphy. The results obtained show very different patterns of variation of K from sequence to sequence and show the little effect that lithology has on susceptibility values, with a variation within the same order of magnitude in all facies. It is concluded in this work that the compositional variations of the strata for this age and tectonostratigraphic contexts are large enough to be measurable from the magnetic point of view and that their distribution was variable over time.