888 HISTORICAL GEOLOGY. 



from the seacoast ; and in the Mississippi valle}^ — then a great bay, as in 

 the Cretaceous period — it. extends northward over 500 miles, covering on 

 the east a broad portion of the state of Tennessee, and reaching into Illinois, 

 and on the tvest, an eastern portion of Missouri and Arkansas. From Texas 

 it extends southward into Mexico. 



The formation exposed to view from New Jersey through Virginia con- 

 sists of sand-beds of different colors, including greensand or glauconitic beds, 

 often shell-bearing, and is referred to the Lignitic Eocene. In South Caro- 

 lina the exposure reaches nearly to the coast, and is more varied in its con- 

 stitution. Along the inner margin occurs a stratum of Bichrstone, about 200 

 feet thick, a cellular siliceous rock, from which the shells have been dissolved 

 away by siliceous waters ; and over this, to the eastward, occur calcareous 

 beds with some greensand, the Santee beds of Tuomey, and the related Ashley 

 and Cooper beds, or beds along the basins of the Ashley and Cooper rivers. 

 On the Gulf border the belt averages 65 miles in width. 



1. The Ilidway, the lowest member of the Eocene, was named thus after a landing on 

 Alabama River, Wilcox County, Ala., by Smith and Johnson in 1887. It was regarded 

 by them as a subdivision of the Lignitic ; it is made by Harris to include the Black Bluff 

 and Matthews' Landing beds, and given coordinate rank with the Lignitic ; the Clayton 

 or Monterey beds of Langdon. 



It is distinguished from the Lignitic by (1) its fossil contents and (2) the off-shore 

 character of its deposits. In the region of Red River and the Mississippi Embayment, 

 marine fossils are often wanting, and the beds are more or less lignitic ; open sea deposits- 

 are found in southeast central Texas, central Arkansas, eastern Alabama and Georgia. 

 No outcrops of this group have been recorded to the northeast of the last mentioned state. 

 Total thickness, about 250'. 



2. The term Lignitic was used by E. W. Hilgard (1860) for the Lower Eocene of Mis- 

 sissippi, consisting partly of freshwater lignitic beds and partly of estuarine fossiliferous 

 deposits. The name Lignitic formation had been still earlier used by Conrad ; and Eo- 

 lignitic was proposed by Heilprin in 1884 ; Lignitic is used by Smitli and Johnson (1887), 

 to designate all Eocene deposits lying beneath the Buhrstone. The name has recently 

 been restricted by Harris to the beds lying between the Buhrstone and the Mattheios Land- 

 ing clays, and is so employed here. The formation includes shallow-water depositions. 

 Lignitic clay beds alternate with sands ; the latter are often cross-bedded ; huge bowlders 

 or septaria-llke concretions are locally very abundant. Animal remains are scarce or 

 wanting in the deposits west of the Mississippi ; but in Alabama and to the northeast, in 

 Maryland and Virginia, they are abundant in certain layers. Where most typically devel- 

 oped (in Alabama) the various subdivisions have received the following names and estimates 

 of thickness from Smith and Johnson: (1) Nanafalia, 200'; (2) Bell's Landing, 140',' 

 (3) Wood's Bluff, 80'-85'; (4) Hatchetigbee, 175'; total, 600'. 



The Pamunkey formation (Darton), i.e. the Eocene deposits of Maryland and Vir- 

 ginia, are referable to the Bell's Landing horizon. 



3. The Lower Claibor^ie was so designated by Harris to distinguish it from the Claiborne 

 proper. It is represented in South Carolina, Georgia, and Alabama by the Buhrstone of 

 Tuomey and Lyell ; in Mississippi by the Siliceous and Calcareo2is Claiborne of Hilgard ; 

 in Louisiana by the Lower Claihorne of Harris ; in Texas by the Timber Belt beds and 

 the Lafayette beds in part, of Penrose ; in California by part of the Tejon group of Gabb 

 and Whitney. Near the axis of the Mississippi Embayment this group is without marine 

 fossils ; elsewhere, especially in its upper portion, it is often highly fossiliferous. In Ala- 



