Diatoms and Benthic Microbial Carbonates

Abstract

Benthic diatoms date from the Early Jurassic and since that time have probably been associated with stromatolites, travertines, and related microbial carbonates in much the same manner as they are today. Diatoms and the extracellular mucilage they produce are important in the stromatolite building process by trapping and binding grains and in the diagenesis of the sediments. Mucilage is produced and deposited on the substrate during migration by motile diatoms and comprises the stalks, tubes, filaments, and envelopes of sessile species. In marine stromatolite and associated habitats, diatoms coat ooids and larger grains and other hardgrounds, as well as the filaments of cyanobacteria and algae. In freshwater carbonate settings diatoms are also a significant component of most microbial communities. To determine the quality of diatom preservation in fossil freshwater microbial carbonates, material from extensive Quaternary travertine deposits in Mexico and Italy was analyzed. Samples were selected to represent as many travertine depositional facies as possible. Results show that diatoms are preserved within all the fossil travertine facies examined.