' EAELIER TERTIARY (EOCENE AND OLIGOCENE). 735 



probable that the Lagrange includes more than the Wilcox, probably beds of Claiborne age, and 

 perhaps some as late as Jackson, as the formation includes all the beds between the Porters 

 Creek clay below and the Lafayette above. The following description of the Lagrange formation 

 is adapted from Glenn i^"" 



The formation consists of interbedded sands, clays, and Hgnitic material. Much the larger 

 part is sand, which is mostly fine grained, though here and there throughout the formation 

 beds of medium or coarse sand or even gravel may be found. Such coarser beds do not seem 

 to be continuous over any large area. 



The sands exposed to view are usually strongly cross-bedded and were deposited under 

 brackish water in a sea characterized by strong and ever varying currents. The clays of the 

 Lagrange vary from pure, fine-grained plastic material to sandy, sUty clays that are in places 

 dark from organic matter or black from lignite. The clays of the lower part of the formation 

 are characteristically fine grained, pure, plastic, and either very hght colored or white. Chemi- 

 cally they are highly sUiceous. The plastic siliceous clays occur as lenses embedded in the sands 

 and outcrop in a belt along the eastern part of the Lagrange area in both Tennessee and Ken- 

 tucky. Many of the beds contain great numbers of beautifully preserved leaf impressions, and 

 numerous collections of these remains have been made. It is entirely possible or even probable 

 that the upper part should be separated from the middle and lower parts and after very detailed 

 work criteria may be forthcoming for this discrimination. At present it is impracticable and 

 all the beds are lumped together, though certain facts render it probable that the upper clay 

 is considerably younger than the plant-bearing clays in the lower part of the formation at Grand 

 Junction, Tenn., and elsewhere. Lignitic material is found throughout the formation but is 

 more abundant in the upper part. Glenn gives the maximum known thickness as 963 feet. 



The eastern edge of the Lagrange formation extends from the southwestern part of Harde- 

 man County, Tenn., north-northeastward through Chester, Madison, Henderson, Carroll, and 

 Henry counties, Tenn., and southwestern Calloway, northeastern Graves, middle McCracken, 

 and northern BaUard counties, Ky. It then passes westward into Pulaski County, 111., not 

 far south of Caledonia Landing. It is not possible to follow it westward across Pulaski and 

 Alexander counties because it is concealed beneath later deposits. 



Shepard '^' reports the Lagrange formation from wells in Caruthersville and Morehouse, Mo. 



Claiborne group. — This group, which overlies the Wilcox, is easUy divisible in Alabama into 

 three formations, the lowest being the Tallahatta buhrstone, the middle the Lisbon formation, 

 and the upper the Gosport sand. Smith ''^°'' describes the Tallahatta as follows: 



"The Tallahatta buhrstone, in the western part of the State, is predominantly composed 

 of aluminous sandstone or siliceous clays tones. They vary shghtly in composition but are 

 always poor in fossils except the microscopic siliceous shells of marine diatoms and Radiolaria. 

 To the east the percentage of clay decreases, the rocks becoming more calcareous and fossils more 

 abundant, and in place of the silicified shell casts of the Tombigbee and Alabama drainage 

 basins are extensive beds of shells, mostly oyster shells. The thickness of the buhrstone varies 

 from 400 feet in the western part of the State to 200 feet in the eastern part. In the western 

 part of Alabama and still more in Mississippi, beds of fossiliferous greensand are abundant in 

 both the Tallahatta and in the Lisbon strata of the Claiborne. The decay of the greensands has 

 in many places given rise 'to the accumulation of deposits of brown iron ore. The Tallahatta 

 buhrstone as here defined is the equivalent of the Siliceous Claiborne of HUgard." 



The Lisbon formation lies between the Tallahatta buhrstone and the Gosport sand and con- 

 sists of about 115 feet of calcareous clayey sands and sandy clays, generally fossiliferous. It is 

 thus described by Smith.'"" 



"The lower half of these beds contains a great number and variety of weU-preserved shells; 

 in the upper half the shells of Ostrea sellseformis and several species of Pecten greatly preponder- 

 ate over other forms. The most characteristic exposures in Alabama of these beds, which are 

 the equivalents of HUgard's Calcareous Claiborne, are at the Claiborne and Lisbon bluffs on 

 the Alabama River." • 



