MARYLAND GEOLOGICAL SURVEY Ixxxiii 



Shore, it is present, if at all, in Caroline, Talbot, Wicomico and Dor- 

 chester counties. This region, however, is covered by a heavy mantle 

 of sand and loam so that it has never been found extensively developed on 

 the surface, nor is there any paleontological evidence of its presence in the 

 records of excavations and well borings. This surface-cover makes it 

 extremely difficult to fix definitely the northern and southern boundaries 

 of the formation, and the lines which indicate them on the map are 

 only approximately correct. The northern boundary of the St. Mary's 

 formation probably enters Caroline county about midway between Den- 

 ton and Federalsburg, runs southwest, passing south of Cambridge and 

 on to Chesapeake Bay. The southern boundary doubtless runs in a 

 direction approximately parallel to the northern one. It probably 

 enters the state in the northern part of Wicomico county and then runs 

 southwest to the mouth of the Honga river. Throughout this region, 

 the country is low and flat. Streams have not opened up channels of 

 any importance, and the occurrence of the St. Mary's formation must be, 

 consequent!}', nearly coincident with the line of strike. 



On the Western Shore the St. Mary's formation is found developed 

 in southern Calvert and in southern St. Mary's counties. In this 

 region, also, it is very much obscured by a mantle of younger material 

 belonging to the Columbia group and is, therefore, seldom seen on the 

 surface. Good exposures, however, are found along the Bay shore, the 

 Patuxent river and its tributaries and in the banks of the St. Mary's 

 river. The most extensive exposure is found in Calvert county along 

 the Bay shore from Point of Kocks to Drum Point. Other exposures 

 are found on both banks of the Patuxent river. In St. Mary's county, 

 exposures may be seen one-half mile west of Millstone on the Patuxent 

 river, where the beds contain beautiful clusters of g}'psum crystals, and 

 along St. Johns Creek and Mill Creek. On St. Mary's river, the forma- 

 tions are exposed at intervals from Windmill Point up the stream toward 

 its head-waters. 



The northern boundary of the St. Mary's formation on the Western 

 Shore is very sinuous and can only be approximately located on account 

 of the cover of surface loams which obscure the underlying formation. 

 The exact location of the southern border is also a matter of conjec- 

 ture, but cannot be very far from correct. Marls belonging to the St. 



