804 INDEX TO THE STKATIGRAPHY OF NORTH AMERICA. 



Surrounding the greater portion of Cuba, but especially along the northern coast and 

 bordering the southern coast of Oriente from Cape Maisi to Cape Cruz, is a low coastal shelf 

 nowhere exceeding a maximum elevation of 30 or 40 feet. There is beneath this shelf in places 

 a lower terrace some 5 or 6 feet above the water's edge. Both of these terraces are composed 

 of elevated coral-reef rock. The material is a limestone presenting an extremely i-ough upper 

 surface and replete with the remains of numerous species of corals which are all, so far as exam- 

 ined, at present living in the surrounding Antillean seas. These reefs have been formed and 

 elevated within very late geologic time. 



A coating of surface gravel exists over the plain in the Province of Pinar del Rio on the south 

 side of the Sierra de los Organos. The material has been derived from the rocks constituting the 

 mountains and has been distributed through the agencies of streams and floods. It is probably 

 of Pleistocene age. 



G-H 14, H-I 15. TEXAS, LOTJISIANA, AND ARKANSAS. 



The following discussion has been compiled by T. W. Vaughan from the litera- 

 ture and from manuscripts of A. F. Crider and Alexander Deussen. Most of the 

 literature is cited in Chapter XVI (p. 723) ; other references are given in the discussion. 



MIOCENE. 



No surface outcrops of marine Miocene deposits between Mississippi River and the Rio 

 Grande have yet been described. Buried marine Miocene beds occur in southern Louisiana 

 and in the coastal region of Texas. The two most thoroughly studied occurrences are those 

 of the Jennings oil well, Louisiana, and the deep well at Galveston, Tex. 



In the Jennings area the equivalent of the Pascagoula formation of Mississippi was pene- 

 trated at depths ranging from 1,040 to 2,183 feet, the variation being due to folding.**"* In the 

 Crowley field the "Rangia johnsoni" zone is from 1,960 to 2,600 feet below the surface.*""' 



Harris *°^ has described a large Miocene fauna encountered in the Galveston deep well 

 between 2,158 and 2,920 feet below the surface. 



Deussen has discovered in De Witt County, Tex., littoral or fresh-water beds in which the 

 remains of Miocene vertebrates were found. The material consists of cross-bedded coarse gray 

 semi-indurated sands, gray sandstones, and local lenses of clay. The beds grade seaward into a 

 marine phase and are overlain by Pleistocene deposits. Deussen thinks that these beds may be 

 a littoral phase of the marine Miocene encountered in the Galveston well. 



Dumble ^'"'^ has proposed the name Oakville for "grits and coarse sands, cross-bedded, with 

 some beds of clay, but oftener with balls, nodules, or lenses of clay embedded in the grit. Some 

 of the sands form a sandrock which is apparently firm and hard, but much of it is so feebly 

 coherent as to fall apart on a slight blow of the hammer. Local beds of conglomerate occur." 

 A few fossil vertebrates were obtained, but they were considered sufficient to determine the age 

 of the formation as "Loup Fork." The formation in which Deussen found Miocene vertebrates 

 in De Witt County may belong to Dumble's Oakville. 



Above Dumble's Oakville are formations named by him Lapara and Lagarto,^^"^ but they 

 have not been correlated with the geologic time scale. 



PLIOCENE. 



No marine Pliocene deposits are known to outcrop between Mississippi River and the 

 Rio Grande, but a recent discovery of G. C. Matson in Louisiana, 8 miles west of south of Alex- 

 andria, indicates that such deposits may have a considerable development in south-central 

 Louisiana and may even extend into Texas. 



The problematic Lafayette formation covers extensive areas in northeastern Arkansas, 

 southern Arkansas, northern and central Louisiana (especially over the Catahoula and Fleming 

 formations), and eastern Texas. 



