BR O WN A ND YELL OW LOAM OF NORTH MISSISSIPPI 3 ° l 



very interesting deposit of siliceous sandstone blocks is found 

 at Rockyford, Union county, Mississippi, twenty-two miles east 

 of Oxford. Along the hills on either side of Tallahatchie 

 River, near the village, blocks of hard white or gray sandstone 

 either rest directly upon the soil (the prevailing position), or 

 are loosely imbedded in sand. Some of these bowlders will 

 weigh, perhaps, 300 or 400 tons, and many of them present 

 square cut surfaces as if just plucked from some parent ledge. 

 These extend for about one-half mile only on each side of the 

 river. The nearest bed rock at all like these blocks is a Sub- 

 Carboniferous sandstone found in southern Tishomingo county 

 some fifty or sixty miles distant and across the Tallahatchie-Tom- 

 bigbee divide, on the headwaters of the latter. These bowlders 

 must have been brought down by icebergs from the north, or 

 possibly from the northeast, coming down the Tennessee River 

 valley and across the divide between this and the Tallahatchie, 

 into the latter, where they deposited their load by melting or by 

 overturning. 



A smaller block of angular fossiliferous chert, weighing 150 

 or 200 pounds, was found at the juncture of the Lafayette and 

 the Yellow Loam at a point about seven miles east of Senatobia, 

 in Tate county. 



Similar bowlders are reported from other parts of the State, 

 but with these I am not personally familiar. 



Absence of stratification in the Yellow Loam may be due in 

 part to its deposition from sluggish currents overloaded with 

 fine detritus (see "Conditions of Sedimentary Deposition," 

 Jour. Geol., Vol. I), but the subsequent alteration of the deposit 

 seems generally to have been great enough to have destroyed all 

 traces of stratification which may have existed. 



D. Subsequent alteration. — In the study of this formation it 

 seems to me that the idea of great chemical alteration subse- 

 quent to deposition has not been properly stressed. The fact 

 is evidenced by the present decayed appearance of the loam 

 proper, and by the surface alteration of the loess ; by the segre- 

 gation of part of the lime and iron in the former into " buckshot " 



