El complejo Turbidítico del Carbonífero del Priorato (Tarragona)

Abstract

[ES] Se caracterizan las facies de una sucesion de 2.250 m de potencia de sedimentos carboniferos turbiditicos de la parte central del Priorato (zona de las vilellas-Poboleda). En 10s materiales paleozoicos de este area se distinguen tres unidades IitoestratigrAficas carboniferas que integran el Complejo Turbidítico del Prioraro y que yacen discordantes sobre 10s materiales del Devdnico medio-superior (unidad 1). Los materiales de la unidad inferior (unidad 2) se depositaron en un ambiente de talud - apron y constan fundamentalmente de areniscas que intercalan niveles deslizados de liditas, calizas y areniscas. Los depdsitos de las unidades 3 y 4 rnuestran diversas asociaciones de facies tipicas de ambientes de abanico submarino profundo. La unidad 3 muestra facies de llanura de cuenca y depositos arenosos de un canal intercalado. La unidad 4 esta constituida por tres megasecuencias negativas que corresponden a otros tantos episodios de progradacion de un sistema de lóbulo de abanico submarino. Se discuten las relaciones entre las asociaciones de facies de las tres unidades litoestratigraficas del complejo turbiditico y su asimilacidn a unidades deposicionales dentro de modelos de sedimentaoidn submarina.

[EN] Facies characteristics are described for a 2.250 m thick succesion of Carboniferous sediments which crops out along the Las Vilellas- Poboleda road (central zone of El Priorato, Catalan Coastal Ranges). In the studied area three main Carboniferous lithostratigraphic units have been distinguished. The lower Carboniferous unit unconformably overlie a basal Devonian unit (unit 1 or Vilellas unit), which is formed by shales alternating with cherts and quarztose sandstones. Unit 2 (Basetas unit) is mainly composed of lithic sandstones. These caotic sediments are interpreted like deposits of a slopeapron system. Severa1 facies associations, typical from deep sea fan environments, are recognized in the two uppermost units: outer fan facies and channel deposits in the Scala Dei unit (unit 3) and distal lobe, proximal non-channelized lobe and proximal channelized lobe facies associations in the Poboleda unit (unit 4). The outer fan deposits consist of monotonous shales with interbedded thin sandstones. A sandstone level, 60 m thick, is found within this facies and has been interpreted as channel deposits. The fan-lobe deposits are arranged in three coarsening and thickening upward megasequences, 500 m thick each one and reflect three major episodes of a fan system progradation. The distal-fan lobe deposits are composed of medium to thick-bedded classical turbidites (low density turbidite currents) internally organized in thickening upward cycles too. The proximal, channelized fan-lobe deposits are formed by amalgamated sandstones and pebbly sandstones deposited through high density currents. The entire sequence of the El Priorato Turbidite Complex seems more likely originated by three well differenciated turbidite systems, which were probably originated by palaeogeographic changes related to tectonic and eustatic changes.