Sedimentary Controls on the Formation and Preservation of Microbial Mats in Siliciclastic Deposits: A Case Study from the Upper Neoproterozoic Nama Group, Namibia

Shallow-marine, siliciclastic depositional systems are dom-inated by physical sedimentary processes, with penecon-temporaneous cementation playing only a minor role in sed-iment dynamics. For this reason, microbial mats rarely form stromatolites in siliciclastic environments; instead, mats are preserved as wrinkle structures on bedding sur-faces. Microbial mat signatures should be widespread in silici-clastic rocks deposited before the Cambrian Period; howev-er, siliciclastic shelf successions of the upper Neoproterozoic Nudaus Formation, Nama Group, Namibia, contain only sparsely distributed wrinkle structures. The facies distri-bution of observed structures reflects the superposition of a taphonomic window of mat preservation on the ecological window of mat development. Mat colonization is favored by