94 . THE GEOLOGY OF ST. JIARY's COUNTY 



the valleys of the Patuxeut and Potomac rivers, as well as in tlie de- 

 pression of their principal tributaries, and along the Bay sliore, the 

 Talbot formation is well developed. It is best seen, however, along 

 the margin of the Potomac Eiver, where it occupies broad flats, par- 

 ticularly on the peninsula between Wicomico Eiver and St. Clement 

 Bay. Along the margin of the Patuxent Eiver. between Horse Landing 

 and St. Johns creeks, the Talbot, altliough present, has been reduced 

 by erosion to a narrow belt scarcely separating the Wicomico on one 

 side from the Eecent beach on the other. 



A large number of streams liave started to sink guillies in the body 

 of the Talbot formation, but as yet have not developed extensive drain- 

 age systems and the continuity of the deposit has been, therefore, little 

 affected by them. 



Structure and Thicl'ness. 

 The base of the Talbot formation ranges in elevation from a few 

 feet above to a few feet below tide. There seems to be no general rule 

 for this variation and it is apparently due to deposition on a slightly 

 uneven surface. The highest portions of the surface of the Talbot 

 formation are found around the margin, where it abuts against the 

 Wicomico formation. In the northern part of the county the surface 

 of the Talbot formation, where it abuts against the Wicomico, has an 

 elevation of about 4.0 or 45 feet. This same elevation is continued 

 southward to the vicinity of Town Creek on the Patuxent, and Breton 

 Bay on the Potomac. From these localities it declines gently toward 

 the southeast until at Scotland, near Point Lookout, the surface lies 

 at a height of 10 feet. This gentle decline is probably due to a slight 

 tilting in the direction of the Atlantic Ocean. The same feature has 

 been described for the Wicomico and Sunderland formations in this 

 region. The thickness of the Talbot formation is variable. Xear 

 Millstone a thickness of about 30 feet has been observed. In many 

 other places the formation lias been found to thin down and disappear. 

 Its average thickness is about 15 feet. 



