Aalenian pulses of tectonic activity in the Iberian Basin, Spain

Abstract

In the northwest Iberian Range the Aalenian to Bajocian interval is represented by condensed, as well as more expanded marine carbonate strata deposited in a shallow epicontinental-sea setting. Precise biochronological data (successive ammonites assemblages) from 29 measured sections, along with a bedby- bed facies analysis, allowed a detailed correlation between sections, the definition of a number of successive transgressive–regressive cycles and of two distinct sedimentation areas, as well as the compilation of isopach maps for short time intervals (duration of ammonites Zone/Subzone) and the assessment of sediment accumulation rates. Differences in facies and thickness in the studied interval, and the sequential organization, reveal significant changes in the depositional environment. A tectonically-controlled compartmentalization of the sedimentation area is suggested by a detailed reconstruction of the accumulation history. An active extensional tectonic regime is supported by contemporaneous volcanic activity in the southeastern Iberian Basin. A precise timing of the main tectonic pulses recorded in NW Iberian Basin for the Upper Toarcian–Lower Bajocian interval is presented, which may help to better resolve the stratigraphy in otherW European during this time interval.