MISS diversity from saline lakes of Brazilian Pantanal: Origin, potential of preservation and comparison with examples of the Ediacaran‐Cambrian shallow depositional settings

Abstract

One of the largest wetlands on Earth, the Brazilian Pantanal contains roughly 10 000 natural lakes, about 1000 of which are hypersaline. In these environmentally stressful settings, animal life struggles to survive, while cyanobacteria form extensive mats. Physical processes and parameters—such as wind shear, wave action, dynamics of the lake-bed substrate and the unrestricted growth and accumulation of mostly bacterial biomass along the shoreline— interact to produce a variety of sedimentary structures linked to microbial activity. At water depths of <5 cm, features such as gas bubbles, reticulated and corrugated patterns, and gas domes are observed. The close resemblance of these structures to those described in late Ediacaran-early Cambrian settings is striking, prompting a debate on whether such occurrences were formed in shallow marine or lacustrine environments. The development of microbially induced sedimentary structures (MISS) in different settings indicates that microbial communities will thrive in environments that favour their development. In the case of the Brazilian Pantanal, the extreme ecological conditions of the saline lakes preclude metazoan life and allow the formation of MISS in a bioturbation-free environment, in a similar scenario to that prevalent during the late Ediacaran-early Cambrian interval.