Observaciones bioestratigráficas y sedimentológicas sobre el Calloviense en la provincia de Zaragoza.

Abstract

Callovian materials (Middle iurassic) fron NE Iberian Chain. Southern Zaragoza Province. are te subject of a detailed biostratigraphic analysis. Four scctions, following a general NW-SE direction, have been sampled lcvel-by-level: Ricla, Tosos, Moneva y Barranco de la Peisqucra (Lécera). In the Ricla-Tosos area, tnost of the biohorizons mecently defined by Cariou (1984) for the Callovian of W. Europe have been evidenced. the Callovian-Oxfomdian stratigraphic gap bening minimum here, and affecting partly the materials of Lamberti Biozone. At the Moneva-Peisquera area, the Callovian-Oxfordian gap appears as maximum (post-Coronatum to Lower Oxfordian, Claromontanus Biozone). Callovian materials at Moneva and Peisquera contain ammonites beloging to Macrocephalus Biozone. Aboye a sharp discontinuity marked by an trregular denudation surface, an oolitic limestone level of Upper Callovian? tu Lower Oxfordian age eontains numerous ammonites, reworked moulds, identified as characteristic of Macrocephalus, Gracilis, Anceps and Coronatum Biozones. Two explanations appear as possible: 1) Feoolites formed from Macrocephalus Biozone onwards, gradually spreading towards pcripheric areas, 2) Fe-oolitic Depositional Sequence started at Upper Callovian? or Lower Oxfordian?, its deposition provoking 4w remobilisation of underlying, callovian materials and the incorporation of numerous Callovian ammonites as reworked moulds.