Early Cretaceous Lacustrine Systems of the Aguilón Subbasin Central Iberian Range, Northeastern Spain

Resumen

The Aguil6n subbasin is one of the Cretaceous sedimentary subbasins of the Iberian basin situated in the Central Iberian paleogeographic domain (Figure 1)(see also Figure 1 in Soria et al., this volume, concerningan overview of the geology and tectonics of the Iberian basin). Extensive facies analysis is based on the study of 13 sections and 10 boreholes (Figures 2/ 3).Figure 4 shows the main facies and stratigraphic unit distribution in the basin from correlation of the two most representative and complete sections. Facies correlation and age assignments are based on charophytes.Two lithostratigraphic units are distinguished (Soria et al., 1995a, b, 1997; Soria, 1997): the Villanuevade Huerva Formation (Valanginian-middle Hauterivian)and the Aguil6n Formation (late Hauterivianearly Barremian) (Figures 2-4). Both units are separatedby a regional unconformity, which has been related to local extensional tectonics (i.e., tilting of blocks along normal faults).Formation of the Aguil6n subbasin was controlled by extensional tectonic events that were related to therifting that took place during the Early Cretaceous in the Iberian Basin (Salas et al., 1995; Salas and Casas,1993). This tectonic control allowed the creation of horsts, grabens, and half-grabens (Salas, 1987)/ which were controlled by listric faults (probably originated285in the late Hercynian) and defined isolated intracratonic basins. Two fault systems controlling thicknes sand facies distribution are identified in the Aguil6nsubbasin (Figures 2/ 3). The main fault system has a northwest-southeast trend and the secondary fault system has a northeast-southwest trend. Two lake systems are recognized in the Aguil6nsubbasin: the Villanueva de Huerva and Aguil6n formations. These systems developed independently (see Figure 4) of each other during the Valanginian-middleHauterivian and the latest Hauterivian-earliestBarremian.