WHO IS THAT MYSTERIOUS BIOMINERALIZER? THE DIAGENETIC MASKING OF CLOUDINA'S PALEOECOLOGY IN THE WHITE-INYO REGION OF CALIFORNIA AND NEVADA, USA

Biomineralized skeletons of benthic organisms are first recorded in the Ediacaran period with the appearance of Cloudina (~548 Ma), a small (length up to 2 cm; 2–4 mm diameter) tube-dwelling organism. Cloudina were examined from the Reed Formation and the overlying lower member of the Deep Spring Formation at several localities in eastern California and western Nevada. At these study sites, Cloudina occurs primarily in shell beds with varying evidence for transportation before final deposition. However, there is also a diagenetic influence on the preservation of these early biomineralizers in the White-Inyo region. Here we present a semi-quantitative alteration index for the levels of dolomitic alteration to the Cloudina specimens and the matrix in which they are preserved. We find significant variety in the alteration levels at the study sites, ranging from thoroughly dolomitized to completely unaltered. There is a geographical pattern to this dolomitic alteration, with the highest levels generally found in the westernmost localities and lowest levels found in the east. In addition to exposing such patterns, the alteration index also aids in the reexamination of previous interpretations of early biomineralizers from the White-Inyo region. The utility of this alteration index in tandem with the wide range of alteration levels found throughout the White-Inyo region could make the area useful as a correlation point when putting the evolution of Cloudina into a global context.