Ichnology of Neritic Turbidite: Silurian Red Mountain Formation, Georgia and Tennessee: ABSTRACT

Abstract

It has recently been shown by others that two thousand units in the Red Mountain Formation are relatively shallow-water turbidites, water depth roughly 100 to 300 ft (30 to 91 m). The turbidites, probably storm-generated, consist of alternating sandstones and shales in fining-upward sequences with scoured bases; the lower turbidite grades upward into hummocky bedded alternating sandstones and shales. Biogenic structures are dominated by Chondrites gracilis, C. flexuosus, and Trichophycus striatus, which occur through most of the units. Others include Dictyodora, Asterosoma, Planolites spp., ?Megagrapton, as yet unnamed radiating grazing trails, and rare Fraena, Aulichnites, Monocraterion, Halopoa, and ?Bifungites. The traces are preserved largely as sandstone hypichnia, h nce most were the work of mud-dwellers. Deposit-feeding evidently predominated over suspension-feeding; ?Megagrapton is an example of a bacteria-farming network. The ethology of Trichophycus is uncertain; the burrow was partly a dwelling structure but may have been the work of a deposit-feeder, suspension-feeder, or carnivore. Stellate forms of Trichophycus are perhaps analogous to circular patterns of burrow apertures seen in deep-sea photographs. The assemblage is a mixture of genera from Cruziana (shelf) and Zoophycos (slope) ichnofacies, as might be expected in a neritic turbidite. Without recently published stratigraphic evidence, the units could be misinterpreted as bathyal turbidites. End_of_Article - Last_Page 979------------