MICROBIALLY INDUCED SEDIMENTARY STRUCTURES INDICATING CLIMATOLOGICAL CONDITIONS AND SEDIMENTARY DYNAMICS IN RECENT AND PLEISTOCENE COASTAL SABKHAS OF TUNISIA

Benthic cyanobacteria construct microbial mats that interact with the specific climatological conditions and sedimentological processes at the sites of bacterial colonization. This interaction causes characteristic ‘microbially induced sedimentary structures – MISS’. This group of structures has been defined as own category in the Classification of Primary Sedimentary Structures, and forms the counterparts to the familiar stromatolites.

Whereas MISS are well known from shallow-marine and tidal settings, this study focuses on sabkha-like environments in the subtropical-arid climate belt. Extensive areas of the coastal sabkhas of Tunisia are overgrown by microbial mats that cause MISS such as petees (not tepees!), polygonal fractures, tapestry bulges, reticulate tuft patterns, and others. The structures record seasonal changes in humidity, changes in salinities, as well as winter/summer rhythms of sedimentation.

A succession of Pleistocene rocks displays a similar set of sedimentary structures, which record an ancient coastline in a past tropical-arid climate zone.

The study documents that MISS are useful tools in the reconstruction of paleoclimate conditions and coastal facies zones.