Shallow carbonate lacustrine facies models in the Permian of the aragon-bearn basin (Western Spanish-French Pyrenees)

Abstract

Massive facies and an apparent lack of well-defined sequences or sedimentary subenvironments are characteristic first impressions from shallow lacustrine carbonate series. Combined sedimentological, petrological and geochemical studies, however, define complex processes and different facies and associations which result from their interaction. This paper examines shallow carbonate lacustrine facies from the Permian ‘Unidad Roja Superior’ of Aragon-Bearn Basin, Western Spanish-French Pyrenees which serve as models of deposition on low gradient lacustrine margins. The suite of pedogenic and subaerial exposure features present in these facies require a soil-micromorphological terminology for their description and interpretation. We propose three facies models: i) low energy margins or ‘palustrine’, ii) high energy margins—wave influenced, and iii) saline. This variability of facies and sequences in closed, small, shallow, alluvial fan-related carbonate lakes emphasizes the response potential of these systems to environmental changes from climate, tectonics, paleohydrology and sedimentary setting. The proposed facies models can be applied as a test of the relative role of these factors in other geological settings.