The Ultramicrostructure of Tubiphyte Walls

Abstract

An ultramicroscopic study of tubiphytes—tubular formations, composed of pelitomorphic calcite from the Lower Permian Tra-Tau reef (Cis-Urals)—was carried out. A multilayer structure of the walls was recognized. The inner layer is an ultrathin layer of acicular calcite crystals, which often has aragonite habit; the next layer is a relatively thick one represented by a dense pelitomorphic mass, which is often encrusted with the calcite crystals. Between the first and second layers are traces of mineralized biofilms, “lace” secretions of mineralized glycocalyx. It is assumed the inner layer is the tubiphyte wall and the pelitomorphic one is the result of biochemogenic carbonate precipitation as a consequence of ability of epiphytic bacterial activity, which colonized the walls of an original organism. A relatively high C/Ca ratio in the glycocalyx relics, its consequent decrease from the acicular wall towards the pelitomorphic one, and finally to the purely chemogenic crystalline formations of crustified rims is an indirect proof of such a formation mechanism of tubiphytes.