Stromatolitic Origin of Laminar Crusts in Palustrine Environments (Pleistocene of Borj Edouana Unit, Northwestern Tunisia)

Abstract

The Pleistocene Borj Edouane in NW Tunisia unit consists of two principal facies associations: (1) calcrete-palustrine-laminar crust facies and (2) microbialites. The laminar crusts consist of millimeter-thick couples (ranging from 0.7 to 3 mm thick) of light (from 0.4 to 2 mm) and dark (from 0.2 to 1 mm) laminae. The laminar alternation represents the succession of events with biological remains under quite hydrodynamic conditions (dark laminae) and of slight erosion and transport episodes by thin water sheets and/or eolian activity (detrital phases, light laminae). The presence of intervening intraclastic-ooidal layers indicate erosive processes and the action of weak sheet flows. The laminar crusts were developed in marginal palustrine environments.