Discontinuidades sedimentarias en la transición Cámbrico Inferior-Medio del manto del Esla, Zona Cantábrica

Abstract

In the Esla nappe, three major discontinuities have been recognized within the Lancara Formation. Discontinuity D1 is located at the top of the white bedded limestones. It is recognized as an erosive contact and marks a sharp change from a peritidal-dominant, homoclinal ramp to a ramp with oolitic and bioclastic shoals distinguished here as the grey lenticular limestones. Discontinuity D2 is placed at the top of the grey lenticular limestones and is the boundary between the lower and upper Lancara members. A discontinuous ferruginous level or hard ground marks the boundary in the Esla nappe. Discontinuity D3 is placed at the bottom of the griotte tectofacies. It marks a major tectonic pulse and the input of fine-grained siliciclastics. In some areas, it is not sharp but gradual. D3 is a diachronous boundary, dated in some areas of the Cantabrian platform. The D3 surface is easily recognisable in SW Europe as a tectonically induced contact reflecting the diachronous and progressive breakdown of some platforms in SW Europe.