Facies model of a sedimentary record for a Pantanal‐like inland wetland

Abstract

Despite recent advances in wetland studies, ancient wetland deposits are still not well documented, and their facies characteristics are poorly registered. Sedimentary facies and sequence stratigraphic analysis of the Miocene Yecua Formation (Chaco foreland basin, Central Andes, Bolivia) and their comparison to Pantanal-like modern wetlands provide an insight into their variability, suggesting a facies model for large inland wetlands that developed in a tropical?subtropical climate. Sedimentological features show that clastic, chemical and biological processes in these environments lead to distinguishable lithofacies variations. Six architectural elements are described: (i) muddy sublittoral (FA1); (ii) mixed siliciclastic?carbonate shoreface (FA2); (iii) sand-flat (FA3) and (iv) mud-flat (FA4) deposits; (iv) floodplain (FA5); and (vi) simple channel deposits (FA6). The succession is composed of shallowing-upward parasequences with different facies characteristics caused by climatically-driven changes of the water level over three orders of magnitude and cyclicity. These cyclic changes reflect a climatic control on the sedimentation. A palaeoclimatic interpretation suggests a generally warm, humid climate with marked rainfall regime changes. The aim of this article is to use this dataset to improve the understanding of depositional elements, lithologies and stratigraphy in tropical?subtropical large inland wetlands. The proposed criteria will help in recognizing inland wetland deposits in other sedimentary basins.