Description and analysis of bioturbation and ichnofabric

TLDR

The authors propose a new scheme for describing and analyzing bioturbation and its resulting ichnofabrics. The scheme comprises a bioturbation index that grades disturbance based on burrow overlap and loss of primary fabric, and an ichnofabric constituent diagram that graphically plots ichnotaxa dimensions, order of emplacement, and coverage. Compared to prior semi‑quantitative methods, the scheme visually portrays ichnofabric, enabling comparative studies and aiding facies analysis, ichnocoenosis and tier diagram construction, and sequence‑stratigraphic identification of hiatal surfaces.

Abstract

A new scheme for the description and analysis of bioturbation and the resultant ichnofabrics is proposed. This system can be used in core and field-based studies and consists of two parts. (1) A bioturbation index in which a descriptive grade is assigned to the degree of bioturbation. This integrates the sedimentology and ichnology, where the higher grades of bioturbation result from increased burrow overlap and the subsequent loss of the primary sedimentary fabric. (2) An ichnofabric constituent diagram which records the detail of the ichnofabric by graphically plotting the dimensional data of the ichnotaxa and their order of emplacement against their coverage. This scheme differs from previous attempts to characterize bioturbation using semi-quantatitive methods and visually portrays the ichnofabric so that comparative studies can be carried out. This is of particular use in facies analysis, the establishment of the ichnocoenoses and tier diagrams, and within sequence stratigraphic studies so that hiatal surfaces can be recognized.