Benthic invertebrates living in low oxygen regions of the Black Sea, Gulf of California, and basins off Southern California form three major biofacies associated with the following concentrations of dissolved oxygen: (1) an azoic region (≤ 0.1 ml/1), (2) a low diversity, small, soft-bodied infauna (0.3–1.0 ml/1), and (3) a diverse calcareous fauna (2 1.0 ml/l). These biofacies recapitulate the chronologic appearance of Pre-Cambrian trace fossils followed by a diverse calcified fauna in the Cambrian.
The basin model has been used to reconstruct a Lower Cambrian oxygen level of 0.1 P.A.L. (present atmospheric level). This value is ten-fold that proposed in the Berkner-Marshall hypothesis.