PALEOBIOLOGICAL IMPLICATIONS OF SKELETAL CONCENTRATIONS IN ORGANIC-RICH RECORDS: TAPHONOMY OF SHELL- AND FISH-RICH INTERVALS OF THE PERMIAN PHOSPHORIA FORMATION
Despite strong regional facies variation, several shell-rich beds persist across most of the basin. These shell beds are associated with significant stratigraphic surfaces, and thin sections reveal multiple phases of phosphatization, calcitization, and silicification. (3) Densely packed, current-oriented siliceous sponge spicules with subsidiary phosphatic grains and fish debris: these mantle parasequence-scale flooding surfaces, are only locally traceable, and reflect a moderate degree of time-averaging. (4) Loosely packed, damaged, phosphatic bioclasts with phosphatic nodules, often with evidence of hardground development. These hiatal beds occur at major flooding surfaces, are traceable for tens of kilometers, and are highly time-averaged. (5) Densely packed, highly damaged, dominantly phosphatic bioclasts associated with pervasive bioturbation and skeletal bioerosion. This hiatal bed mantles the basal sequence boundary, is traceable throughout nearly the entire basin, and reflects extensive winnowing and time-averaging. These lithologic characteristics indicate that even in settings of low sedimentation rate and nutrient enrichment, stratigraphic hiatuses regulate the abundance, preservation, and likely time-averaging of the shelly fossil record.