84 THE PLIOCENE AND PLEISTOCENE DEPOSITS OF MARYLAND 



Section of Lafayette Formation One and One-half Miles Southeast of 



PlSCATAWAT. 



Pine grayish-yellow loam 5 feet. 



Medium coarse gravel in a matrix of gray sand 4 



Yellow cross-bedded sand 3 



Unassorted gravel mixed with gray sand 5 " 



Total 17 " 



'Steatigraphic Eelations. — The Lafayette formation is developed as 

 a terrace lying irregularly and miconformably on whatever older forma- 

 tion chances to be beneath it. These range from the pre-Cambrian and 

 Paleozoic crystalline and metamorphic rocks of the Piedmont Plateau 

 up into the later members of the Miocene beds. About five miles north 

 of Frederick in western Maryland there is a small area of gravel resting 

 unconformably on the Newark at an elevation of 500 feet. This deposit 

 in some respects suggests Lafayette although its age is not and perhaps 

 never will be definitely determined. As a whole, the Lafayette forms the 

 surface cover over the region where it is developed, its surface correspond- 

 ing to the surface of the country. In southern Maryland, however, 

 where the Sunderland formation laps up around its base, it is believed 

 to run out for some little distance under the Sunderland. In that case, 

 it would be overlaid uncomformably along its margin by the latter 

 formation. As a whole, the Lafayette formation is developed as a terrace 

 and, although the oldest of the surficial deposits, lies topographically 

 highest and at the center of a concentric border of younger terrace 

 formations which wrap about it. 



THE PLEISTOCENE PERIOD. 



To this period have been referred the Sunderland, Wicomico, and 

 Talbot formations. There are several lines of evidence which indicate 

 that these formations are Pleistocene. In the first place, they are 

 separated from the Lafayette by a pronounced uncomformity which 

 represents a period of uplift and erosion. Again, they are separated 

 from the Eecent shore deposits and subaqueous platform by an uncon- 

 formity which also represents a period of uplift and erosion, although 



