ORIGINAL ARTICLE Similarities and differences in the dolomitization history of two coeval Middle Triassic carbonate platforms, Balaton Highland, Hungary Ja ´nos Haas • Tama ´s Budai • Orsolya Gy} ori • Sa ´ndor Kele Received: 25 November 2013 / Accepted: 3 February 2014 Ó Springer-Verlag Berlin Heidelberg 2014 Abstract Dolomitization of platform carbonates is com- monly the result of multiphase processes. Documentation of the complex dolomitization history is difficult if com- pletely dolomitized sections are studied. Two Middle Anisian sections representing two coeval carbonate plat- forms were investigated and compared in the present study. Both sections are made up of meter-scale peritidal–lagoo- nal cycles with significant pedogenic overprint. One of the sections contains non-dolomitized, partially dolomitized, and completely dolomitized intervals, whereas the other is completely dolomitized. Based on investigations of the partially dolomitized section, penecontemporaneous dolo- mite formation and/or very early post-depositional dolo- mitization were identified in various lithofacies types. In shallow subtidal facies, porphyrotopic dolomite was found preferentially in microbial micritic fabrics. Microbially induced dolomite precipitation and/or progressive replacement of carbonate sediments could be interpreted for stromatolites. Cryptocrystalline to very finely crystal- line dolomite, probably of pedogenic origin, was encoun- tered in paleosoil horizons. Fabric-destructive dolomite commonly found below these horizons was likely formed via reflux of evaporated seawater. As a result of the different paleogeographic settings of the two platforms, their shallow-burial conditions were significantly different. One of the studied sections was located at the basinward platform margin where pervasive fabric-retentive dolomi- tization took place in a shallow-burial setting, probably via thermal convection. In contrast, in the area of the other, smaller platform shallow-water carbonates were covered by basinal deposits, preventing fluid circulation and accordingly pervasive shallow-burial dolomitization. In the intermediate to deep burial zone, recrystallization of par- tially dolomitized limestone and occlusion of newly opened fractures and pores by coarsely crystalline dolomite took place. Keywords Dolomitization Á Carbonate platform Á Depositional cycle Á Pedogenesis Á Stable isotopes Á Middle Triassic Á Balaton Highland Á Hungary Introduction Petrogenesis of dolomites is commonly the result of mul- tistage processes (e.g., Machel 2004; Nader et al. 2004; Chen et al. 2004; Fu and Quing 2011; Bazargani-Guiliani et al. 2010; Di Cuia et al. 2011). As a result of overprinting of the consecutive dolomitization stages, detection of the paragenetic succession is difficult or cannot be unambig- uously achieved in the pervasively dolomitized rocks. However, in some cases, there are contemporaneous rock bodies of similar sedimentological characteristics, which show different grades and modes of dolomitization, i.e., non-dolomitized or only partially dolomitized successions and completely dolomitized ones occurring relatively close to one another, in the same structural unit. Comparative analysis of these successions provides a good opportunity J. Haas (&) Á O. Gy} ori MTA-ELTE Geological, Geophysical and Space Science Research, Pa ´zma ´ny P. se ´ta ´ny 1/c, Budapest 1117, Hungary e-mail: haas@ludens.elte.hu T. Budai Geological and Geophysical Institute of Hungary, Stefa ´nia u ´t 14, Budapest 1143, Hungary S. Kele Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Budao ¨rsi u ´t 45, Budapest 1112, Hungary 123 Facies DOI 10.1007/s10347-014-0397-1