ECTLicH.] SOUTHERN AREA — MESOZOIC FORIVIATIONS. 121 



area over wLicli they were originally exposed is covered by drift, so that 

 but fragmentary information can be obtained. In general arrangement 

 of the succession of strata the groui) here compares favorably witli the 

 outcrops in the Seminole Hills. So far as I could determine, the thick- 

 ness is diminished, amounting to about 1,400 to 1,G00 feet. "With the 

 steadily changing dip and the disconnected exposui-es, it is a difficidt 

 matter to reach any accui'ate estimate of the vertical dimensions. Within 

 these limestones, Froductus, Orthis, and some Crinoids were tbund. 



Fermian Group. 



East of the anticlinal fold, resting directly upon the upper portions of 

 the Carboniferous limestones, some yellow, light-gray, and pink sand- 

 stones and shales occur. They closely resemble the Permian beds from 

 adjoining regions. Drift covered all but a small portion of them, so 

 that I nowhere obtained a satisfactory exposure. The thickness of this 

 series will here not much, if any, exceed 150 feet. 



TEXAS. 



On the eastern side, the Triassic beds are almost entirely hidden by 

 di'ift, but they were found exposed to the north and west. They occupy 

 but a comparatively small area, bemg covered partly by drift, partly by 

 the succeeding yoimger formations. Sandstones and shales of a dark- 

 red color below are followed by massive beds of bright-red shales. 

 Heavy sandstones interstratified with shales, red at first, and changing 

 into i)ink, yellow, and whitish, close the formation. In the thick beds of 

 shale the characteristic banks of dolomitic composition are found that 

 occur elsewhere in the same horizon. jSTear the base of the lower sand- 

 stones Mr. S. F. Emmons* observed a bed of semi-crystalline lime- 

 stone, and collected from it a number of specimens of Natica Lelia. This 

 is the only genus and species which I know to have been found in the 

 Triassic formation of our district. From the outcrops to the west and 

 north the total thickness of the teds may be regarded as over 600 feet. 

 In strati graphical arrangement the Triassic beds are conformable to 

 those described above. 



JUKA. 



A series of marls and limestones which occur above the red beds, indi- 

 cate the i^resence of the Jurassic formation. We find the arrangement 

 of the strata to be relatively the same as observed at other localities. 

 Dark-gray, partly argillaceous and arenaceous limestones near the base, 

 followed by yellow, graj'^, and white shales and marls, which contain an 

 occasional interstratum of limestone. Emmons obtained Camptoncctes, 

 Belemnites, JEumicrotis, and Astarte from the lower limestones ; we found 

 Felemnites while passing over them. The vertical development of the 

 Jurassic beds has somewhat diminished as compared to occurrences 

 further north. We may regard the thickness as a little over 100 feet 



CRETACEOUS. 



Within this southern area we have a full development of the Cretaceous 

 formation. While the groups heretofore described owe their surface 

 exposure to a cause that may be regarded as accidental, we can consider 

 the Cretaceous beds as typical for the southeastern portion of our dis- 



*Rep. Geol. Expl. 40tli PaiaUcl, vol. ii, 1877, p. 1G2. 



