Regional Geology

The geologic history of Elk Knob and the surrounding area begins with the break-up of the supercontinent Rodinia and birth of the ancient Iapetus Ocean between the rifted continental masses. As the Iapetus Ocean grew, it separated Laurentia from another continental landmass called Gondwana, which was comprised of South America, Africa, Antarctica, and Austrailia.

The break-up of Rodinia spanned ~185 million years as marked by two distinct pulses of volcanism.

The first period of failed rifting in the southern and central Appalachians began 750-735 million years ago, resulting in formation ofthe Crossnore plutonic-volcanic suite, and Mt. Rogers and Grandfather Mountain formations.

The Iapetus Ocean formed as the supercontinent Rodinia rifted apart separating the two ancient landmass, Laurentia and Gondwana. Drafted after Scotese, Paleomap Project available on the world-wide web @ http://www.scotese.com/.
The second period of successful rifting occurred ~565 million years ago as evident by Catoctin basalts, which are interlayered and overlain by upward-maturing siliciclastic sequences of the Cambrian Chilhowee Group (Aleinikoff et al., 1995; Hatcher, 2010).

Overlying Chilhowee Group rocks is the Cambrian Shady Dolomite, a carbonate shelf deposit that indicates a transition from rift-to-drift tectonics to development of an open ocean and a stable continental margin by the end of the Cambrian (Hatcher, 2010).

Many of the aforementioned rock formations can be found in within ~25 miles of Elk Knob as noted on the geologic map of northeastern Tennessee and northwestern North Carolina shown below (modified from Hatcher et al., 2006).

 

GEOLOGIC MAP OF NORTHEAST TENNESSEE AND NORTHWEST NORTH CAROLINA

Regional geologic map of northeast Tennessee and northwest North Carolina, modified from Hatcher et al., 2006.

 

Rocks at Elk Knob occur in the uppermost Blue Ridge thrust sheet and are part of a sequence of rocks referred to as the Ashe Metamorphic Suite. These rocks represent oceanic crust and distal margin sediments that formed subsequent to rifting and formation of the Iapetus Ocean off the Laurentia margin.  It is uncertain whether the ocean crust was generated at a mid-ocean spreading center or volcanic back-arc basin, although many studies favor the later (Abbott and Raymond, 1984; Misra and Conte, 1991; Raymond et al., 2003a; Raymond et al., 2003b; Swanson et al., 2005; Swanson and Raymond, 2010).  If the Ashe Metamorphic suite originated as a mid-ocean spreading center, it could be as old as NeoProterozoic (i.e., ~735–565 million years old).  Conversely, if originated in a back-arc rift environment, the Ashe Metamorphic suite maybe as young as Ordovician (~450 million years old), a time when volcanic arc terranes outlined the Laurentia margin.