142 GEOLOGY. 



The Cretaceous formations of Alabama illustrate some of the 

 peculiarities of structure displayed by the corresponding beds of New 

 Jersey. The Selma Chalk, which is thick in the western part of the 

 state, thins to the eastward, and disappears altogether before the 

 eastern border of the state is reached. Two formations in the eastern 

 part of the state, therefore, seem to be the equivalent of the three 

 in the western part. The interpretation of these relations has been 

 suggested elsewhere. The relations of the several formations to each 

 other and to the Tuscaloosa, are shown in Fig. 389. 



The Cretaceous beds of the Gulf coast (Alabama) have been dis- 

 turbed to a greater extent than the corresponding beds along these 

 parts of the Atlantic coast where the system has been carefully studied. 

 They have been deformed into low anticlines and synclines in some 

 places, and even faulted (Fig. 390) to a slight extent. 



Fig. 390. — Section of the Ripley formation on the right bank of the Tombigbee river, 

 Alabama, above Moscow, showing deformation and faulting. The total thick- 

 ness of the beds shown in the figure is not more than 75 feet. The faults are there- 

 fore slight. (Smith.) 



The Western Gulf border region. 1 — The general stratigraphic rela- 

 tions of the system in this region are the same as farther east, but 

 deposition seems to have been well under way before the oldest beds 

 of the corresponding system farther east began to be laid down. The 

 system here is much thicker than that farther east, and is made up 

 of a series of alternating beds of sand, shale, limestone, and marl, most 

 of which are of marine origin, attaining a maximum thickness of 4000 

 feet. Three principal series are recognized 2 : The Dakota (or Wood- 

 bine) formation; (2) the Colorado series, including the Eagle Ford, 

 the Austin, and the Taylor formations, and (3) the Montana series, 

 or Navarro formation. 



The Dakota series, 600 feet and less thick, is largely of ferruginous, 

 argillaceous sand, with some lignite, and is probably of non-marine 

 origin. The Eagle Ford formation, about 500 feet thick, is essentially 



1 Hill and Vaughan, 18th Ann. Kept. U. S. Geol. Surv., Pt. II, pp. 238-242. 



2 Hill, 21st Ann. Rept., U. S. Geol. Surv., Pt. VII, p. '114. These names sup- 

 plant older ones. Woodbine is the equivalent of the old Lower Cross Timber, and the 

 Taylor and Navarro formations were formerly described under the name Ponderosa. 



