UNUSUAL STROMATOLITE MORPHOLOGY AND DIAGENESIS IN THE UPPER CAMBRIAN COPPER RIDGE DOLOMITE, CHEROKEE LAKE, EAST TENNESSEE

The Copper Ridge Dolomite is exposed within the Saltville thrust sheet along the banks of Cherokee Lake in Grainger County, Tennessee, occurring as thin to thick beds of highly stromatolitic and oolitic dolostone with chert nodules and synaresis cracks. Regionally, the Copper Ridge deposits have been interpreted as representing shallow subtidal to intertidal. Approximately 21 distinct stromatolite clusters exposed at extreme low lake level were identified east of the Turney Mill Plantation development in a narrowly confined horizon of undetermined thickness of the Copper Ridge Dolomite. The distinctive stromatolites occur in a poorly exposed portion of the lower Copper Ridge. The preserved external weathering expression of the stromatolites may not always correlate with the growth form of the stromatolites. These weathered external forms include “balls,” “domes,” “coconuts,” “stacked mounds,” and “pillars”. The secondary surface patterns produced by stromatolitic laminations include “bilete,” “trilete,” “tetralete,” “pentalete,” “mammilate,” “multimammilate,” “birdsnest,” “digitate,” and “simple mounds.” Some of the surface patterns represent stromatolitic laminations and infill relationships. The outer surfaces (laminae) of the stromatolites are trunctated suggesting erosion. Internal growth forms are dominated by smoothly arcing microbial laminations radiating away from the center in most of the external form shape. The infill between the stromatolites includes lamina and thin beds of ooid grainstone and intraclasts. The origin and mechanism which produces the external forms and secondary surface patterns remains problematic; however, the stromatolite morphologies are similar to diagenetically-derived structures. The distinctive Turney Mill stromatolite occurrence is possibly correlative with Copper Ridge stromatolites at Norris Lake (Harris, 1966).