Evolución tectonosedimentaria de una cuenca extensional intraplaca: La cuenca finijurásica-eocretácica de Los Cameros (La Rioja-Soria)

Abstract

Located in the northwestern part of the Iberian Ranges, Los Cameros Basin was developed under a very subsident extensional regime during the Latest Jurassic-Early Cretaceous interval. This basin was filled with a very thick serie (up to 9000 m) of essentially continental deposits. In the basin evolution three main geotectonic events can be distinguish: 1) Sin-rift extension and synchronous infilling (Latest Jurassic-Early Cretaceous); 2) Post-rift metamorphism (Middle-Late Cretaceous) and 3) Tectonic inversion (Tertiary). The basin infilling (Tithonian-Early Albian) corresponds to a large cycle bounded by two main unconformities that can be divided into six Depositional Sequences. Its development took place into two rifting phases. In the first one (Latest Jurassic) the other two main basin of the Iberian Rifting were also created: South Iberian and Maestrazgo. During the Valanginian-Hauterivian age both rates and areas of deposition were drastically reduced. The second rifting phase (Barremian-Early Albian) caused a renewed increment of the sedimentation rate, being specially remarkable in Los Cameros Basin. Moreover a neat parallelism is recognizable between cycles of lacustrine facies development and the global eustatic cycles. Los Cameros Basin is structurally interpreted as a synclinal basin formed upon a south dip ramp in a subhorizontal extensive fault (extensional ramp basin) located several kilometers deep into the basement. The displacement of this fault caused the basin and its progressive increase in size. Depocenters of the successive Depositional Sequences were migrating towards the north as consequence of the fault displacement. Tertiary compression (Paleogene-Early Miocene) provoked the basin inversion by means of a neoformed thrust in its northern margin (up to 30 km displacement over the Tertiary Ebro Basin) and a system of thrusts in the southern margin (over the Tertiary Duero and Almazán basins).