﻿O. Meyer — Tertiary and Grand Gulf of Mississippi. 25 



The Jacksonian stratum " d" occurs at Moody's Branch at a 

 higher level than southeast from there at the bridge over the 

 Pearl Biver. This would indicate a southern dip. On the 

 other hand, following Moody's Branch toward its mouth in a 

 southeastern direction the «>lder strata dip up stream. Stratum 

 "e" is seen at the uppermost part of the creek two feet above 

 the water ; a few hundred yards below, its surface is five feet 

 above the water, and farther below, the whole stratum is about 

 four feet above the water. Supposing a difference in the water 

 level of four feet even, which must be a maximum there, there 

 is yet a northern dip for these strata at this creek. 



Grand Gulf formation in Grand Gulf. 



The material of the Grand Gulf formation in Grand Gulf is 

 quite variable. Cross-bedded sands pass over and alternate 

 with friable as well as hard sandstones of the same structure 

 and even regular quartzites occur. The clays have different 

 degrees of induration. I did not notice here the laminated 

 clays found in Terry. It may be that these laminated clays 

 occupy the highest horizon of the Grand Gulf formation, above 

 the sandstones which form the top of the strata in Grand Gulf 

 — if the "Grand Gulf formation" is one single formation. 



The sandstones enclose silicified trees. Although making a 

 careful search I was unable to detect any shells as such in these 

 strata, but some of the indurated clays, besides traces of lignit- 

 ized plants, contain impressions of fresh-water bivalves, and these 

 cannot be said to be very rare. The most distinct ones which 

 I was able to collect are two casts of TJnio, each showing both 

 valves. I procured in all casts of at least three species of TJnio. 



Resume. 



1. After studying the literature as well as the field, I do not 

 know any place where Grand Gulf strata can be seen in actual 

 superposition over the Marine Tertiary. 



2. There are two places where strata which cannot be dis- 

 tinguished from unquestioned Grand Gulf can be seen actually 

 overlaid by Marine Tertiary. In one of the cases, moreover, 

 there is internal evidence that these strata were dry land or 

 nearly dry land before the Marine Tertiary was deposited 

 upon them. 



3. The Grand Gulf formation, at least for its main part, is 

 not a marine formation ; it contains fresh-water shells. 



4. A thick and extended marine greensand formation with 

 a numerous fauna is found in Eastern Mississippi. It is 

 parallel to the strata immediately below the Claiborne profile. 

 Its fauna is Claibornian, but approaches the Jacksonian. 



