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Microbial-dominated Carbonate Platforms during the Ladinian Rifting: Analogical Models for Microbialite Reservoirs (Catalan Basin, NE Spain)

Ramon Mercedes-Martin, Ramon Salas, and Concepción Arenas

The Ladinian sedimentary record represents a major marine transgressive pulse over the Mediterranean region (north-eastern Iberia) during the Middle Triassic. This record is arranged in two transgressiveregressive sequences formed by two steepened microbial-dominated carbonate ramp systems. Syn-rift subsidence which controlled the creation of accommodation space, also determined the depositional styles and, especially, the palaeogeographical domains where specific microbialites proliferated (thrombolites and stromatolites).

Thrombolite bodies (ca. 40m thick) display two types of architectures: biostromal and mud-mounded, whereas stromatolite bodies (at least 7m thick) shows stratiform and domed, head-shaped morphologies. Domed and mounded forms usually developed during stages of increasing accommodation rates, whereas stratiform and biostromal morphologies tended to grow in association with periods of low accommodation rates.

Taking into account the three types of microbialitic facies (thrombolites, stromatolites and ooidal-peloidal stromatolites) and modal porosity estimations, a 2D conceptual model of trends of porosities has been performed. Thrombolite samples display a mainly intraparticle and intracristaline vuggy porosity, reaching porosity values of 5 to 15%. Domal and planar stromatolite samples are prone to develop fenestral and vuggy porosities with values ranging from 15 to 20 %. Ooidal-peloidal stromatolite samples develop interparticle and keystone porosities varying from 5 to 20%.

The Middle Triassic microbial-dominated carbonate systems of the Mediterranean region can be used as analogical models in reservoir analysis due to the diversity, abundance and preservation of their microbialites and the well-known sequence stratigraphic framework, architectures and palaeogeographical constraints associated with them.

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