LIMESTONES OF WESTERN TENNESSEE 573 



The rock exposures along the river at Savannah belong to the 

 Glenkirk horizon. The Brownsport bed, overlying red rock, is 

 exposed at Cravens, and also a mile farther down the river, at 

 Cerro Gordo. At the latter locality the Brownsport exposure is 

 25 feet thick and richly fossiliferous. Above Saltillo the Glenkirk 

 bed is seen again. The Saltillo limestone occurs along a creek 

 southwest of town a little over a mile. At the landing, a well 

 50 feet deep struck plenty of undoubted Chattanooga black 

 shale. The richly fossiliferous glade region of the Tennessee 

 River valley region between Swallow Bluff and Perryville offers 

 numerous exposures of the Brownsport bed. Swallow Bluff is 

 situated on the north side of the Tennessee River, about half- 

 way between the mouths of Indian and Hardin Creeks. 



At Brownsport Furnace, about two miles west of Vice's store, 

 the Brownsport beds, 120 feet thick, forms two glades, south of 

 the old furnace. The southern glade exposes the lower part of 

 the Brownsport bed resting on the Dixon red clay. The north- 

 ern glade exposes the middle and upper part of the Brownsport 

 bed. At the base of the northern glade occur several beds of 

 limestone containing Strop]io7iella roemeri and Platyceras broivns- 

 portensis. Immediately above, the clay is richly fossiliferous. 

 The horizon occurs about 50 feet above the Dixon bed. Owing 

 to the dip of the rocks, the actual vertical interval is about 35 

 feet. Fossils occur also at other elevations. The most interest- 

 ing horizon is formed by the upper 20 feet of the section. At 

 the top corals are numerous. Immediately beneath the coral 

 horizon occur Atrypa arctostriatus , Rhipidomella lentiadaris, and 

 Rhynchonella lindenefisis. Various silicified sponges belonging to 

 species common in the Brownsport bed occur, loose, at the very 

 top of the exposure. The Chattanooga black shale was exposed 

 by excavations for ore along the hillside northwest of the old 

 furnace. There is no evidence of the presence of the Linden 

 bed at this locality. 



9. Dixon Spri/ig; localities visited by Roemcr. — The Dixon 

 Spring, located on the old Colonel Wallis Dixon farm, 3 miles 

 south of Perryville, is in the midst of ^classic ground, since the 

 collections of Silurian fossils made bv Roemer during his five 



