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Integrating outcrop data and forward computer modelling to unravel the development of a Messinian carbonate platform in SE Spain (Sorbas Basin)



Geological mapping, definition of facies distributions and reconstruction of platform-interior growth geometries of the Messinian Cariatiz carbonate platform (Sorbas basin, South Spain), were performed to evaluate the controlling factors in platform growth and to test a 3-D computer simulation program. For the simulation with the program REPRO, five platform-related facies were modelled: (1) the reef crest facies by the numerical solution of a Fisher equation; (2) the lagoonal facies by a function of water depth-dependent carbonate production; (3) the proximal and middle slope facies (breccia and block facies, calcarenite facies) by a subroutine simulating gravity-driven particle export from the reef crest; (4) a distal slope; and (5) a basinal facies by a pelagic rain function. Development of a fan delta conglomeratic system is simulated by using a siliciclastic point source and gravity-driven particle redistribution. A best fit between the observed platform growth geometries and modelling results is achieved by assuming that high-frequency sea-level changes superimposed onto a longer term sea-level fall controlled platform growth. For the modelling, a relative sea-level curve was reconstructed, which is based on a deep-sea benthic foraminiferal stable oxygen isotope record at ODP Site 926 with a 45 m eustatic sea-level fall, and a tectonic uplift component of 20 m. The consistency of 3-D simulation results is corroborated by the coral growth rates provided by the Fisher-equation subroutine. These rates of 2–8 mm year−1 compare well to the coral growth rates in Recent fringing reefs. We propose that during the early stage of platform evolution the high-frequency fluctuations were obliquity-modulated precessional cycles, whereas precessional cycles control later stages of platform growth. REPRO provides a separate visualization of the different facies bodies as a function of time and space, showing the intrinsic pattern of facies distribution in the platform. This is the result of a combination of platform growth and syndepositional subaerial erosion. For example, only the youngest stages of reef framework facies in the development of the Cariatiz carbonate platform are preserved.