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Fault-controlled Stratabound Dolomitization of Aptian Shallow-water Carbonates in the SE Maestrat Basin (E Spain)

Juan Diego Martín, Enrique Gomez-Rivas, Anna Travé, Ramon Salas, Mercè Corbella, Telm Bover-Arnal, Sherry L. Stafford, and Jaume Vergés

Syn-rift shallow-marine carbonates of Middle Aptian to Early Albian age crop out in a well-exposed area of the southern Maestrat Basin (E Spain). The area registers the thickest Aptian-to-Albian succession of the Maestrat basin, and one of the most complete carbonate successions of this age reported in the northern Tethyan margin. In addition, the host limestones (Benassal Formation) are partially replaced by dolostones providing an outcrop analogue of fault-controlled hydrothermal dolomitization.

The syn-rift deposits filled a semigraben controlled by basement normal faults. The carbonates are dominated by the typical age-equivalent facies characterized by the presence of orbitolinid foraminifera, coral and rudist bivalve fauna. The succession is stacked in three transgressive-regressive sequences (T-R) bounded by surfaces with sequence stratigraphic significance.

The dolomitization of the host rock is spatially associated with two sets of basement faults, and forms seismic-scale stratabound tabular geobodies that extend several kilometres away from the faults, mostly in their hanging walls. The dolostones registers the typical hydrothermal paragenesis constituted by host limestone replacement, dolomite cementation and sulfide MVT mineralization. The replacement preferentially affected middle to inner ramp graindominated facies consisting of bioclastic pakestones and peloidal grainstones. Field, petrology and geochemical data indicate that the replacement took place after early calcite cementation and compaction, most likely during the Late Cretaceous post-rift stage of the basin.

The studied Aptian succession provides a stratigraphic framework that can be used for oil exploration in ageequivalent rocks, especially in the València Trough, offshore Spain. Moreover, this new case study is a world-class example of stratabound partially dolomitized carbonate reservoirs.

AAPG Search and Discovery Article #90161©2013 AAPG European Regional Conference, Barcelona, Spain, 8-10 April 2013