During the post-Maysville, pre-Richmond interval a stream flowing southeastward on the southeastern flank of the Nashville dome cut the Pulaski Channel in Giles and Lincoln counties, Tennessee, for a known length of 32 miles with average width of 1500 feet and depth of 100 feet. During Richmond time this channel was filled with clastic sediments brought in from the southeast by the advancing Richmond sea. About 75 feet of Lower shale and Conglomeratic sandstone was deposited during the first, or estuarine, phase. Lenses of Lower limestone conglomerate consisting of pebbles and cobbles of older underlying limestone in a matrix of sandstone were deposited during this phase. The second, or marine, phase began when the Richmond sea invaded the region and submerged the channel now three-quarters filled with estuarine sediments. Along the submerged channel a total of 70 feet of Upper limestone conglomerate, Upper shale, and Sandstone member of the Mannie shale was deposited contemporary with the accumulation of about 45 feet of normal Richmond over the surrounding region, consisting of Fernvale formation, Mannie shale, and Sandstone member of the Mannie shale. The Upper limestone conglomerate, which is equivalent to the Fernvale limestone member, was deposited upon the upper slopes of the channel and upon the top of the Lower shale. The submerged channel was filled flush with the surrounding sea floor by the Upper, or Mannie, shale.
At the same time the Fayetteville Channel in Lincoln County underwent a similar history, but the sediments filling this channel are too poorly preserved to permit satisfactory investigation and interpretation except by analogy with the Pulaski Channel.