Analysis of the upper Lenoir and Holston formations : deposited along a Middle Ordovician shelf reentrant, Rutledge Pike locality, Knoxville, Tennessee

Paleoecological and paleoenvironmental interpretations were determined for the upper Lenoir and Holston formations at the Rutledge Pike locality in Knoxville, Tennessee. The Holston represents deposition along a shelf margin reentrant, as part of a major reef tract which bordered a large carbonate bank during Middle Ordovician time. At this locality the Lenoir represents a near-reef lagoon, and the Holston is a complex of anastomosing mud-mounds, skeletal sand-banks, organic thickets, and patch reefs deposited in shallow water.

The Lenoir is composed of packstone and wackestone with distinctive faunal and floral assemblages. Echinoderms, Girvanella oncolites, stromatoporoids, and lesser Eimounts of bryozoans are the major faunal constituents. The algal assemblage consists of Nuia, Solenopora, and Girvanella, with minor amounts of Kazakhstanelia. The Holston at Rutledge Pike is composed of skeletal grainstone with subdominant packstone and associated boundstone which contain an unusual fossil assemblage when compared with other Holston localities. Ramose bryozoans and pelmatozoans dominate the grainstone and packstone whereas encrusting bryozoans and stromatoporoids dominate the boundstone. Algae are quite common throughout the Holston with Girvanella and Solenopora the most frequently observed. The presence of abundant algae and stromatoporoids in the Holston is unique to this locality.

Twelve different genera of bryozoans were observed in the Holston along with undifferentiated genera from three additional families. Growth forms, diversities and relative abundances of bryozoans responded to changes in environmental conditions. The distribution of six genera of algae infers specific paleoenvironmental information. Stromatoporoids are commonly found in patch reefs and organic thickets where they competed with, and often outcompeted, bryozoans as encrusting framework builders and as sediment binders.

The Holston Formation at Rutledge Pike was deposited as an up-slope, shallow water, reefoid accumulation on a shelf-margin reentrant. In contrast, down-slope, deeper deposits of the Holston occur to the southwest at Alcoa Highway, Knoxville, Tennessee.

At Rutledge Pike, Stictopora-Batostoma-Nicholsonella dominate the boundstone and Stictopora-Batostoma-Nicholsonella dominate the grainstone and packstone facies. Comparatively, at Alcoa Highway, Stictopora-Batostoma-Nicholsonella dominate core facies, or boundstones. Stictopora-Bythopora-Hemiphragma-Ottoseetaxis dominate grainstone flank facies.