Heterogeneous subsidence and paleogeographic elements in an extensional setting revealed through the correlation of a storm deposit unit (Aptian, E Spain)

Resum

A coastal marine siliciclastic unit has been studied from a palaeogeographic and structural stratigraphic point of view. The unit was deposited during the Aptian in the extensional Las Parras sub-basin (Maestrazgo basin, E Spain), and it has been subdivided in four coarsening-upward sequences. A general description of each sequence is done but we focus in the third sequence (S3), which is built up of fi ne to coarse-grained sandstones, representing a vertical facies shift from storm dominated lower shoreface to upper shoreface environments. Both physical and genetic criteria have been used to correlate sequence S3. Top of sequence S3 is a minor... (Ver más) erosive surface and is considered a reliable cronostratigraphic datum for correlation across the study area. Lateral facies changes of sequence S3 suggest the location of a siliciclastic discharge system toward the southeast of the study area. Drainage entry could be related to an intersection of basin bounding faults. Over the datum surface, coarsening upwards sequence S4 lacks its lower part in the south easternmost area. An intra-S4 local discontinuity is defi ned and correlated toward the north western area. The south-eastern area was located over a different subsiding block than the other sections and different subsidence histories for these blocks are interpreted on the basis of thickness trends and features of the intra-S4 discontinuity. Intra-S4 discontinuity marks the change from siliciclastic to carbonate dominated sedimentation, thus it could be representing a major break in the sedimentary dynamic. Spatial thickness trends of each sequence at the intra-block scale probably represent alternating episodes of homogeneous and heterogeneous subsidence that may be related to extensional dynamics.