Abstract
En este trabajo se describe la estratigrafía y sedimentología de la Formación Conglomerados de Andatza. Mediante el análisis de facies se han interpretado tres asociaciones de facies principales correspondientes a un sistema turbidítico (de grano grueso) y al talud: un sistema turbidítico interno (o cañón), un talud fangoso de alto gradiente y otro de bajo gradiente. La distribución cartográfica de las asociaciones de facies junto con el análisis de paleocorrientes describen un modelo sedimentario de sistema turbidítico de grano grueso en forma de “L” para los Conglomerados de Andatza, cuya morfología fue controlada por fallas normales sinsedimentarias de basamento. El carácter grosero del tamaño de grano de este sistema turbidítico indica la proximidad del área fuente de los conglomerados, que alimentaría el cañón turbidítico desde el norte a través de una estrecha plataforma marina.
Highlights
Aptian−Albian basin-margin coarse-grained sedimentary rocks in the Basque-Cantabrian rift basin have usually been interpreted as fan-delta deposits laid down in coastal environments (Andatza Fm; García-Mondéjar, 1982; Monte Grande Fm; Robles et al, 1988a,b; Oiartzun Fm; Fernández-Carrasco et al, 1990a,b), indicating the erosion of an emerged basement adjacent to the coast line
Agirrezabala & García-Mondéjar (1994) evidenced that deep-marine coarse-grained sedimentation occurred in the Albian of the Basque-Cantabrian basin (BCB), and suggested the presence of a narrow shelf between the emerged source area and the deep-marine basin
In this field-based study, new data based on mapping, stratigraphic correlation and sedimentological analysis is presented, that enable a new depositional model to be proposed for the Andatza Conglomerates during the late Albian−lower Cenomanian of the northeastern BCB margin, to the northwest of the Palaeozoic Bortziriak (Cinco Villas) Massif
Summary
Aptian−Albian basin-margin coarse-grained sedimentary rocks in the Basque-Cantabrian rift basin have usually been interpreted as fan-delta deposits laid down in coastal environments (Andatza Fm; García-Mondéjar, 1982; Monte Grande Fm; Robles et al, 1988a,b; Oiartzun Fm; Fernández-Carrasco et al, 1990a,b), indicating the erosion of an emerged basement adjacent to the coast line. Fig. 2.—SW-NE chronostratigraphic chart of the Lasarte sub-basin (study area) with indication of the formations of the Andatza turbidite system and adjacent slopes (after Bodego et al, 2015). Sandstones and mudstones are similar to the facies of this facies association, which indicates that they are intraclasts.
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