MARYLAND GEOLOGICAL SURVEY 167 



The materials composing the Lafayette formation consist mostly of 

 quartzitic sands and gravels, either loosely held together or united 

 more or less firmly with a cement of iron oxide. There are also 

 found in places small admixtures of clay which aid in binding the 

 otherwise loose sands together. The consistency of the materials varies 

 anywhere from loose sand and gravel to conglomerate. Where the iron 

 has not succeeded in binding the materials firmly together the face 

 of an exposure has the appearance of being case-hardened when dry, 

 although somewhat less obdurate when wet. The outliers of Lafay- 

 ette are frequently hidden in the midst of thick woods and covered 

 over with heavy undergrowth. Where the streams have cut into 

 them the banks rapidly fall in and are quickly covered with vegetable 

 growth. Good exposures are consequently very rare in this forma- 

 tion. Only where the material is artificially exposed by the opening 

 of pits, is one able to gain a good idea of its internal structure. One 

 of these gravel pits is found at a height of 380 feet on M. Marple's 

 farm, one mile west of Egg Hill. Here there is a gravel hill which 

 has been used for road-material for miles around. The gravel, how- 

 ever, is not as coarse and the proportion of pebbles to fine gravel 

 and sand is about equal. There is also a little clay mixed in the 

 deposit. Near the top of the hill at a height of about 400 feet there 

 is a heavy bed of iron-sandstone and conglomerate, varying from 3 

 to 5 feet in thickness. This is so firmly cemented that it has been 

 used for building purposes. 



The best exposure of the Lafayette formation is on the highway 

 one mile south of Bay View. Here, in a large pit which has been 

 opened for road-material, there is an 18-foot exposure of coarse gravel 

 in which some of the pebbles are between one and two inches in diame- 

 ter, and are mixed with brownish-yellow sand, containing a little 

 clay. The proportion of pebbles to very fine sand is about 2 to 1. 

 The whole is colored brownish by iron, but in no place is it cemented. 

 The grade of coarseness of the gravel is remarkably uniform from 

 the bottom to the top of the exposure. 



On Elk Neck there are no good exposures in the Lafayette for- 

 mation. There is abundant proof, however, that the formation is 



