Conceptual Framework for the Analysis and Classification of Fossil Concentrations

Abstract

Densely fossiliferous deposits are receiving increasing attention for their yield of paleobiologic data and their usefulness in sedimentology and stratigraphy. This trend has created a pressing need for standardized descriptive terminology and a genetic classification based on a coherent conceptual framework. The descriptive procedure outlined here for skeletal concentrations stresses four features -taxonomic composition, bioclastic fabric, geometry, and internal structure-that can be described readily in the field by nonspecialists. The genetic classification scheme is based on three end members, representing biologic, sedimentologic, and diagenetic factors in skeletal concentration. Concentrations created through the simultaneous or sequential action of two or more factors are classified as mixed types. As a conceptual framework for comparative biostratinomic analysis, the broad categories of this ternary classification scheme should facilitate recognition of large-scale temporal and spatial patterns in skeletal accumulation. The usefulness of this approach is suggested by the good agreement between biostratinomic patterns observed in ancient onshore-offshore facies tracts and those predicted across paleobathymetric transects based on modern processes of skeletal concentration.