The road to Red Top Mountain State Park passes over Lake Allatoona on Bethany Bridge. At the west end of Bethany Bridge, in winter when water levels are low, you may see intrusive contact between Corbin Meta-granite and Rowland Spring formation.
Corbin meta-granite is estimated to be 1 to 1.5 billion years old. The Rowland Spring formation was intruded by the Corbin, and therefore is considerably older.
At this location and many others, riprap around bridge abutments may contain a crazy assortment of rock from Ridge and Valley or Piedmont sources.
Intrusive contact between
Corbin Meta-granite and Rowland Spring formation
Corbin is lighter massive rock (right side);
Rowland Spring is darker laminated rock (left side)
West end of Bethany Bridge approaching Red Top Mountain State Park,
Lake Allatoona, Georgia
Tectonic catastrophe in riprap
Fractured carbonate interfingered with
quartz-pebble conglomerate.
Riprap boulder, west end of Bethany Bridge,
Lake Allatoona, Georgia
(Hat for scale)