Trail Geology

Trail Geology. . , The sedimentary rocks along the trail between Johnson City and Elizabethton consist of, from oldest to youngest, the Honaker dolomite (a modified limestone), Nolichucky Shale, and Knox Group limestones. They range in age from 542-488 million years and were deposited in a shallow tropical sea on the coastline of Laurentia (North America) when it was located south of the equator. The limestones and dolomites were formed by the accumulation of countless shells and body parts of animals that lived in these seas. The shale was formed by clay deposits washed off the continent and into the sea. , Sedimentary rocks are generally deposited as flat lying layers on the sea floor but the rocks on the trail are all tilted. The tilting occurred during the Alleghanian orogeny, a mountain-building event that took place about 325 million years ago when Laurentia collided with Gondwana (Africa) creating the supercontinent of Pangea and the Appalachian Mountains. The orogeny deformed the sedimentary rocks causing them to be tilted, fractured, and faulted. It also recrystallized the limestone destroying most of the original fossils formed in the rock.