This digital database is an inventory of microfossil samples in units or formations containing mottled mudstones and units or formations stratigraphically above and below units containing mottled mudstones. This database contains detailed information about each sample (e.g., USGS laboratory number, field number, collector and date collected, location quadrangle etc.) and database entries from selected published references relevant to this research. The latter entries include only as much of this information as is available based on available records. References used in this inventory are cited at the end. Modifications to this database are expected as new information becomes available, research expands into southern California, and papers are published.