W. B. Clark — The Matawan Formation. 439 



sand and the Marslialltown sand and clay of the New Jersey 

 Geological Survey.* 



The Matawan formation gradually thins from about 220 feet 

 on the shores of the Paritan Bay to less than 20 feet along the 

 Potomac, where the formation finally disappears. The country 

 throughout much of this distance of nearly 200 miles is more 

 or less thickly covered with deposits of Pleistocene age which 

 make it impossible to trace the beds continuously, although the 

 numerous well-borings have greatly aided in the interpretation 

 of the deposits. For cartographic purposes, on the scales 

 adopted by the IT. S. Geological Survey and the Maryland 

 Geological Survey, it has not been thought desirable to 

 attempt the mapping of the subsidiary divisions of the Mata- 

 wan, although this is reported to have been successfully accom- 

 plished for the State Geological Survey of 'New Jersey by Mr. 

 G. N. Knapp, who has recognized four members in the Mata- 

 wan, known from below upward as the Merchant ville clay bed, 

 the Woodbury clay bed, the Columbus sand bed, and the 

 Marshalltown sand and clay bed,f which he has extended 

 practically across the State of New Jersey, although the 

 Columbus sand bed 100 feet thick in Monmouth County is 

 represented as reduced to 20 feet at Swedesboro and "farther 

 southwest it seems to pinch out." These beds, because of the 

 different physical conditions attending their formation, are 

 reported by the State Geologist of New Jersey to show minor 

 differences in their faunas, these faunules being recognized 

 wherever the deposits appear. These subdivisions cannot, 

 however, be satisfactorily recognized in Maryland, where the 

 Matawan possesses greater homogeneity, being throughout 

 predominantly a micaceous sandy clay. J Similar faunal dif- 

 ferences commonly appear with lithologic variations, and in 

 Maryland many such occurrences have been recognized and 

 described in the Paleozoic and Tertiary formations, although 

 from their size it has not seemed wise to cartographically rep- 

 resent them. 



Many attempts have been made to correlate the Atlantic 

 Coast Cretaceous deposits with other American and with Euro- 

 pean formations. In an earlier paper the author referred to 

 the Senonian and Danian affinities of the higher Cretaceous 

 formations in New Jersey, while the paleobotanists have 

 regarded the lower Cretaceous formations to be the equivalent 



* See description of these beds in vol. vi, Final Rept. of the State Geolo- 

 gist of New Jersey, pp. 155-161. 



f These names first appeared in print in the Annual Report of the State 

 Geologist for 1898 published in 1899, although the field work was started 

 some years earlier. 



\ The more sandy character of the upper Matawan is still recognized in 

 Cecil County but becomes largely lost in Kent County where the black mica- 

 ceous sandy clay increases, and is found in the upper as well as the 

 lower beds. Farther south no differentiation in the formation appears pos- 

 sible and the deposits become mainly black micaceous sandy clays through- 

 out, although the few feet of the lower and often slightly darker beds of 

 the undifferentiated red sands above may possibly represent the upper 

 Matawan farther north. 



