Sedimentología y bioestratigrafía del Viseense y Serpujoviense del área de Sierra Palacios, Valle del Guadiato (Córdoba, España)

Resumen

Some calcareous outcrops at Sierra Palacios belonging to the San Antonio-La Juliana Unit at Guadiato Valley (Cózar & Rodríguez, 1999) have been studied (Fig. 1). They have been mapped, one stratigraphic section has been described, microfacies analysis have been done and foraminifera and Incertae sedis have been studied. The outcrops are so strongly karstified that field observations are very poor, particularly at the uppermost part of the section. In addition, areas around Sierra Palacios are covered by hillside colluvial fans that impede to analyse the relationships between the calcareous outcrops and the surrounding rocks (Fig. 2). The structure of Sierra Palacios is quite complex. Up to six limestone blocks diverse in size (SPL1-6) show an imbricate disposition (Fig. 2). They are regarded as olistolites placed into a talus. They were afterwards imbricated by sinestral transpressive tectonic movements. Some small outcrops located southwards are identified as SPL7 (Fig. 2). The most complete stratigraphic section is located in SPL1 (Fig. 3). The units 1-5 show a transgressive sequence from subtidal flat to open platform deposits. Calcareous sand shoals and algal mounds are conspicuous in unit 3. The unit 6 shows a regressive sequence from open platform to intertidal flat deposits. The foraminiferal assemblage indicates an upper Viséan epoch for SPL1-6 (Zones 14 and 15 of Mamet, 1974) (Fig. 4, Plates II-III) The foraminifera assemblage of the Zone 14 is characterised by abundant Lituotubella glomospiroides Rauser-Chernoussova of great size (= L. magna Rauser-Chernoussova auct.), Pseudolituotuba gravata (Conil and Lys), Tetrataxis ex gr. minima Lee & Chen, Priscella prisca (Rauser-Chernoussova & Reitlinger), Eostaffella radiata (Brady), Archaediscus ex gr. chernoussovensis Mamet, and Nodosarchaediscus saleei (Conil and Lys), as well as several types of Incertae sedis like Parathurammina ex gr. spinosa Lipina, and Polysphaerinella bulla (Conil and Lys). The most singular element of this assemblage is the single occurrence at Guadiato Valley of Plectogyrina fomichaensis (Lebedeva). The most important foraminifers in the Zone 15 assemblage are Howchinia bradyana (Howchin) emend. Davis, Monotaxinoides priscus Brazhnikova & Yartseva, and the high abundance of Saccamminopsis fusulinaeformis (McCoy). the foraminiferal assemblage of SPL7 is characterised by the abundance of Planospirodiscus and Neoarchaediscus and the appearance of Asteroarchaediscus with almost totally occluded lumen. It is regarded as belonging to the Zone 17 of Mamet (1974) which is lower Serpukhovian.