682 INDEX TO THE STEATIGRAPHY OF NORTH AMERICA. 



K 14-15. IOWA AND MINNESOTA. 



In Iowa the Cretaceous is represented by the Dakota sandstone and the Colo- 

 rado group. The Dakota is exposed in the western part of the State where it was 

 originally studied and was named from the town of Dakota, Nebr., on Missouri 

 River. It is also penetrated in many artesian weUs and has a thickness of 50 to 

 100 feet. The formation consists of more or less calcareous shale and sandstone, 

 with thin bands of lignite .^^° 



The Colorado exhibits a section of shale and chalky limestone, having near 

 Hawarden, Iowa, a thickness of 50 feet but elsewhere ranging from a thin edge to 

 150 feet. The strata carry Prionocydus wyomingensis, Inoceramus labiatus, and 

 Ostrea congesta. Selenite is of common occurrence in the shales. 



In Minnesota the Cretaceous is widely distributed over the western part of the 

 State but so heavily covered by drift that but few outcrops appear. HaU.^^** 

 gives a total of 500 feet of beds, white sandstone of the Dakota at the base and soft 

 blue shale and incoherent sandstone of the Benton above. 



K 18. LONG ISLAND. 



The Cretaceous strata which appear along the northern shore of Long Island 

 have been carefuUy correlated with the New Jersey section by Veatch,^^''^ who con- 

 cludes that the "basal beds are the stratigraphic equivalents of the Raritan and 

 are Upper Cretaceous. The Matawan beds are apparently well represented but their 

 character changes going seaward" to gray sands and clays. "No greensand beds 

 comparable to the great greensand marl beds of New Jersey have been found, their 

 stratigraphic position being occupied by fine lignitiferous sand with occasional clay 

 beds." HoUick^*" expresses another view. 



K 19. MASSACHUSETTS. 



At Gay Head and elsewhere on the island of Marthas Vineyard are exposures of 

 the Vineyard series of Shaler,^^*'' which comprises Cretaceous strata and Miocene 

 beds (unconformable?) upon them. Shaler says: 



The Gay Head section consists of tliree divisions. The central part (that is, that part 

 which faces nearly west) has a length of about 3,500 and an average height above the sea of 

 about 80 feet. At the southern end of this section there is an exposure of about 2,000 feet in 

 length, which trends toward the southeast. At the northern end of the principal section there 

 is another short and incomplete section which trends nearly east and west. These three divi- 

 sions constitute one great and nearly continuous sea cliff having a length of over 6,000 feet. 



The face of this cliff shows us a great number of thick, steeply inclined beds of sand, clay, 

 and lignitic matter, of extremely vivid and contrasted colors. The colors range from the 

 dazzling white of the sandy beds to the nearly pure black of the carbonaceous layers, with 

 intermediate hues of brown, green, yellow,, and red. * * * 



The orderly arrangement of the beds in the section is greatly masked by the continued 

 slipping of large wedges of the deposits down the steep incline of the talus. When we apply a 

 correction for this slipping the beds are seen to lie in a tolerably regular order, dipping usually 

 to the northeast, with inclinations varying in general from 20° to 60° of decUvity but rising 

 in one place to 90°. 



