Abstract

Middle Ordovician conglomerates at about the same stratigraphic position have been studied in six areas along the southeastern margin of the Valley and Ridge Province for 325 miles from Fincastle, Virginia, through eastern Tennessee to northern Georgia.

Pebbles and cobbles in the conglomerates are mainly limestone derived from the Upper Cambrian and Lower Ordovician, but many are quartzite, sandstone, or siltstone from the Middle and Lower Cambrian.

Studies of the rounding of pebbles and cobbles and the distribution of the coarser beds show that the source area lay to the southeast. These conglomerates are interpreted as deposits laid down in a subsiding trough near discharge points of major streams draining recently uplifted highlands to the southeast. The conglomerates record early pulsations of the erogenic disturbance which affected the southern Appalachians from Chazy to early Trenton time.

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