El Neógeno de la Cuenca Guadalquivir- Cádiz Basin (South Sapin)

• Wenceslao Martínez del Olmo ^[1] ; D. Martín ^[1]
  1. [1] Oil and Gas Capital. s.l. Ángel Muñoz ,3, 28043 Madrid
• Localización: Revista de la Sociedad Geológica de España, ISSN 0214-2708, Vol. 29, Nº. 1, 2016, págs. 35-58
• Idioma: español
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• Resumen
  • español

    La cuenca miocena de antepaís alpino del Guadalquivir-Golfo de Cádiz contiene numerosos yacimientos de gas biogénico, motivo por el que muchos datos de sísmica y sondeo permiten reconocer tanto su estructura como las siete Secuencias de Depósito de tercer orden que contiene. Las tres primeras, Langhiense inferior a Serravalliense tienen un área de depósito restringida al Golfo de Cádiz. La Secuencia Tortoniense se inicia con un evento transgresivo que incrementa enormemente el área marina de la cuenca. La extensión y continuidad de sus facies marino someras permiten dudar de la existencia del estrecho Norbético. Su cortejo sedimentario de alto nivel (HST) es coetáneo con el deslizamiento de olistostromas de procedencia S-SE y contiene dos sistemas de turbiditas arenosas: las de procedencia NE y las de procedencia N-NO. La Secuencia Tortoniense-Messiniense 1 se inicia por un nuevo y modesto ascenso de nivel marino, prograda desde el NNO y es prácticamente pelicular en el eje de la cuenca. La Secuencia Messiniense 2-Plioceno 1 se inicia por un cortejo sedimentario de nivel bajo (LST) provocado por una importante caída del nivel marino que ocasionó drásticos cambios paleogeográficos: erosión, bypassing sedimentario y transporte de turbiditas arenosas hasta el Golfo de Cádiz. Este LST bien desarrollado finaliza con la transgresión pliocena que da paso a un HST de espesor considerable. La Secuencia Plioceno 2 - Pleistoceno está pobremente representada por sedimentos en facies continentales y marinas depositadas respectivamente en los actuales segmentos terrestre y marino de la cuenca.

  • English

    The Alpine foreland of the Guadalquivir-Gulf of Cadiz basin contains 45 biogenic gas fields in Miocene sandy reservoirs. Their past and actual hydrocarbon exploration provided a very good hard data base that allow recognize its structure and their sedimentary infill. The Neogene deposits contain seven Depositional Sequences of 3rd order, whose description and special features make the main purpose of this work. The first three Depositional Sequences (Langhian-Serravallian) were sedimented in a restricted area located in the more internal segment of the basin, SW of the Gulf of Cadiz. The Tortonian Depositional Sequence begins with a TST event that greatly increases the marine area of the basin and their continuity, thickness and shallow marine facies cast doubt about the existence of the Northbetic Strait. Their following HST provided a very important deep water facies sedimentary volume that contains two systems of sandy turbidites with NE and NNW flow direction. The first one may be derived from six-seven main hiperpicnic flows, and the second one is a classic system from delta bottom set. The HST is coetaneous with the thick olisthostromes sliding from S-SE. The Tortonian-Messinian 1 Depositional Sequence starts with a new and modest sea level rise and their HST prograde from the NNW of the basin margin and suffers a major sedimentary condensation on the distal basin segments, however in shallower locations their TST and HST provided siliciclastic and thin limestone beds. The Messinian 2-Pliocene 1 Depositional Sequence means a paleogeographic revolution promoted from erosion and its correlative sediment transport induced by an important intra-Messinian sea level drop. The sea level fall promote a sedimentary bypassing and a highly developed system of sandy turbidites in the distal Gulf of Cadiz locations, that can be composed by Basin floor fan (Bff), Slope fan complex (Sfc) and the Prograding complex (Pc). The LST turbidite system is fossilized by the Pliocene sea level rise. The Pliocene 2 – Pleistocene Depositional Sequence is poorly represented by continental and marine facies, respectively located in the current terrestrial and marine segments of the basin.