Ouachita orogeny (a mountain building event) had marine sedimentation left extensive deposits later a flysch sequence with dark shales was deposited.
The Ouachita orogeny was a mountain building event that resulted in the folding and faulting of strata currently exposed in the Ouachita Mountains. Through the Ordovician, Silurian, Devonian, and early Carboniferous, marine sedimentation left extensive deposits of black shale, quartzose sandstone, and chert beds. During the Mississippian, a flysch sequence with dark shales and graywackes was deposited. 
