MAllVLAXU GEOLOGICAL SURVEY 95 



of the Columbia Group which are deposited in terraces at a lower level. 

 On the eastern margin of the county these lower formations have in a 

 large measure been removed by erosion so that the Sunderland stands 

 out prominently and frequently may be seen occupying the uppermost 

 stratum of the cliffs, overlying unconformably the older deposits of 

 Miocene beneath. 



Many streams have forced their headwaters back into the body of the 

 Sunderland formation so that it no longer is as continuous as when 

 first deposited, but has developed a sinuous outline and is broken up into 

 a number of isolated areas (Plate VII, Fig. 1). The most important of 

 these areas extends from Lyons Creek southward to the Fishing-Hunting 

 Creek depressions. Another one extends from this point southward to the 

 Parker-Battle Creek valleys, and a third from this depression southward 

 to Cove Point, although it is almost severed by the headwaters of St. 

 Leonard Creek opposite Flag Pond. These areas stood out as islands 

 when the country was submerged during Wicomico time (Fig. 2 and 

 Geological map). 



Structure and Thickness. 

 In the northern portion of Calvert County the base of the Sunderland 

 formation lies at an elevation of about 90 feet, and in the southern por- 

 tion at about 70 feet, indicating a difference between the two localities 

 of 20 feet in 32 miles, or a dip of .7 of a foot per mile toward the south- 

 east. The highest point of the surface of the Sunderland formation is 

 near ]\It. Harmony in the northern part of the county, where the eleva- 

 tion reached is abov.t ISO feet. Farther south, near the mouth of the 

 Patuxent River, the surface of the Sunderland does not exceed 127 feet, 

 and where it finally disappears, near Drum Point, it is about 90 feet 

 in height. This slope of the surface is probably due not only to a slight 

 dip of the formation toward the southeast, but also to the initial slope 

 which was imparted to the formation while it was being deposited as a 

 terrace beneath the waves of the Sunderland sea. Beside the slope to- 

 ward the southeast there is also a gentle decline from the water-shed 

 which passes down the backbone of the county to the Patuxent River 



