New microbial fossils from ∼1.3 billion‐year‐old rocks of Eastern California

Publisher Website
Google Scholar
Abstract
New types of microbial fossils and new occurrences of fossils previously reported only from the Beck Spring Dolomite of the Pahrump Group are now recognized from each of the 3 formations of the Pahrump Group (Crystal Spring Formation, Beck Spring Dolomite and Kingston Peak Formation) approximately 1.3 .times. 109 yr old. Comprising perhaps 8 or 9 distinctive forms, these fossils are characteristically preserved as faint ghost-like structures whose low-contrast outlines are clearly revealed only when illuminated by a Xe lamp and recorded on high-contrast film. They represent a distinctive, previously overlooked or neglected type of preservation that has significantly extended the known distribution of microbial fossils in the Pahrump. They include the oldest occurrence known of filaments designatable as Girvanella and apparently the 1st from rocks of pre-Phanerozoic age. Similar fossils were also found, using the same techniques, in the Chuar Group of the Grand Canyon [USA] and in the Uluntui Suite of middle Riphean age in eastern Siberia [USSR]. Although time correlation of pre-Phanerozoic rocks based on similar microbial assemblages would be premature, similarity between such assemblages in all formations of the Pahrump Group and with that of the Uluntui Suite is consistent with the inferred unity and middle Riphean age of the Pahrump Group. In addition to the Girvanella, 2 smaller types of filaments, 2 kinds of simple spheroids, and 3 composite forms (2 spheroids and 1 stalked cluster) that attain diameters up to 80 .mu.m and are probably eucaryotic were found.