Study of fossil microborings; new approach

Resin casting of recent microbial borings with simultaneous embedding of the resident microorganisms was introduced in 1970. Scanning electron microscopy (SEM) of the cast permitted a three-dimensional perception and thus, detailed characterization of borehole morphologies. It also demonstrated the complexity, diversity, and biological specificity of boring patterns. Combined with light microscopy of sectioned, double-embedded resin preparations, SEM images have been identified in terms of their specific microbial origins. These studies constitute a solid basis from which to approach and understand the ancient endoliths.

A new technique for preparation of fossil microborings introduced in 1978 permits SEM resolution of a quality that had not been achieved previously. This technique permits a direct comparison of fossil to recent microborings. The new approach has been applied to Pliocene microborings in oyster shells, Upper Cretaceous borings in belemnite rostra, organically preserved Upper Silurian endolithic rhodophytes, and microborings in Ordovician brachiopod shells. Thus it opens 600 m.y. of microbial endolithic activity to detailed study and interpretation. Examples of microbial borings throughout the fossil record retain a structural fidelity comparable on a submicron level with recent microborings.