PHYSIOGRAPHIC RELATIONS OF SERPENTINE 589 



In Central Alabama the basic magnesian and serpentine belt 

 passes beneath the Coastal Plain and the conditions become favor- 

 able to the occurrence of statenlithic domes. It is interesting, 

 therefore, to find directly on this line 90 miles and 120 miles 

 respectively, from the border, the Lower Peach Tree anticline and 

 the Hatchetigbee anticline, the one intersected by the Alabama 

 River and the other by the Tombigbee River. These deformations 

 of the Coastal Plain sediments are essentially unique east of the 

 Mississippi. That they are normal folds, due to horizontal com- 

 pressive stress, is sufficiently improbable to suggest that they may 

 be either saline domes or statenlithic domes; and it is hoped that 

 the testimony of the drill will decide the matter in the near 

 future. 



Although these anticlines have marked geologic relief, the up- 

 ward arching of the Eocene, and, presumably, of the Cretaceous 

 strata amounting to hundreds of feet, they are devoid of topo- 

 graphic relief, the Pliocene (Lafayette) strata crossing them with- 

 out deviation. In other words, they were base-leveled in Pliocene 

 time and have suffered no subsequent deformation, the power of 

 growth, whatever its source, seeming to be quiescent or exhausted. 

 A further distinct indication that they are not true statenlithic 

 domes is found in the fact that their axes, trending with the strike 

 of the Coastal Plain formations, are directly transverse to the 

 course of the basic magnesian or serpentine belt. 



It appears, then, that an unquestionable statenlithic dome 

 remains to be identified; although it may be suggested in passing 

 that in so far as the saline domes are due to the derivation in situ 

 of gypsum from anhydrite they belong to this new type of relief. 



The contact of the statenlith with the bordering formations is a 

 true fault; and to this extent Willis and Dodge are right in their 

 interpretation of Staten Island geology. But they err, as I believe, 

 in correlating the obvious displacement with ordinary fracture and 

 slip faults and with the extended, rectilinear displacements of the 

 Triassic strata. The latter originated in a profound crustal 

 readjustment involving the entire depth of the katamorphic zone 

 and tapping, in some cases, reservoirs of the most truly abyssal 

 magmas. The statenlith displacement, on the other hand, strictly 



