Northeastern Section–41st Annual Meeting (20–22 March 2006)

Paper No. 5
Presentation Time: 10:00 AM


STROTHER, Paul K.1, CAMPBELL, Leslie2 and BECK, John H.2, (1)Geology & Geophysics, Boston College, Weston Observatory, 381 Concord Road, Weston, MA 02493, (2)Department of Geology & Geophysics, Boston College, Weston Observatory, 381 Concord Road, Weston, MA 02493,

Samples from the JOY-2 core through the Conasauga Group in eastern Tennessee have been used to examine the paleoecology of the Rogersville Shale. This Middle Cambrian formation, which is dominated by mudstones with minor marly beds, contains lingulellid brachiopod fragments and a rich palynoflora dominated by non-marine cryptospores. The paleontological signature suggests an originally estuarine environment of deposition. A detailed examination of petrography is used to support this interpretation. The Rogersville Shale contains abundant autochthonous glauconite and is heavily bioturbated, as determined by micro-scale disruption of laminae. In conjunction with the recovery of incompletely oxidized organic matter in the form of palynomorphs, this indicates deposition in a fully oxygenated environment that experienced rapid deposition. The rate of fine-sediment deposition is not easily quantified, but we are attempting to provide a range of estimates based on modern systems in which complete bioturbation and oxidation of particulate organic matter is interrupted due to progressive burial of an active surface layer. The occurrence of glauconite in ancient sediments has long been viewed as indicating deep water deposition, but this actualistic view is sorely in need of revision, as numerous deposits throughout the geologic column clearly violate this paradigm. Our goal is to utilize palynology in conjunction with sedimentary petrology and ichnology to provide constraints on the reconstruction of depositional environments and paleoecology of Middle Cambrian rocks around the Laurentian margin, many of which appear to more proximal than previously thought.