Reports
A radiographic examination of physical and biogenic sedimentary structures in the Chesapeake Bay
1982, Reinharz, E., Nilsen, K.J., Boesch, D.F., Bertelsen, R., and O'Connell, A.E.
Report of Investigations 36
Abstract
Radiographs of box cores collected from nearly 200 stations serve as a basis for a descriptive study of the Chesapeake Bay bottom. Eighteen plates of characteristic sedimentary environments are included in this paper, identifying pertinent physical and biogenic features.
Prominent physical sedimentary structures include large-scale cross-bedding in medium to coarse sands, small-scale cross-bedding in fine sands, interbedded mud and sand in mixed sediments and laminated mud bedding in fine-grained sediments.
Almost all of our cores showed some evidence of biogenic sedimentary structures. Salient features include tubes and burrows as well as bioturbated textures. Many of these structures are associated with polychaetous annelids.
Biological activities dominate physical processes throughout much of Chesapeake Bay bottom. The prevalence of physical structures over biological features occurs in the upper Bay and in the deep-water channel regimes . Heterogenously textured mud environments are produced by sedentary tube inhabitants and relatively permanent burrow-dwelling species, primarily occupying the sediment surface. The more motile deep-burrowing fauna in sands tend to create homogenous fabrics. The composition of the benthic community is an essential aspect in the assessment of biological effects on the sedimentary environment.
