426 A. "^\ GRABAU THE SHERBURNE SAXDSTON'E 



from the remains, thev are land plants and were probably swept to their 

 present position by river currents. 



Besides these undoubted plant remains, there are elongated, raised 

 ridges on the under side of many of the sandstone layers, which represent 

 the natural fillings or casts of depressions of similar form in the surface 

 of the mud layer next below. These have been doubtfully referred to 

 fucoids by Tanuxem and described as Fucoides grapliica, because they 

 resemble "the stiff, simple markings, excepting as to size, of the juvenile 

 scholar.'*'^ They are most probably not plant remains, their character 

 being more nearly that of depressed trails or tracks made in the surface 

 of the mud flat. But what organism could be responsible for the making 

 of such tracks, if tracks they are, does not appear. The absence of re- 

 mains of the organism itself suggests that it was a land form, which 

 visited this region temporarily, or else that it was soft-bodied and so left 

 no remains. There is, however, another interpretation of these structures, 

 recently advanced by J. ^I. Clarke^ after a suggestion by J. B. Wood- 

 worth, namely, that they are groves formed by ice crystals, such as are 

 produced by the formation of ground ice in shallow water. 



EASTWARD EXTEXSIOX OF THE HORIZOX OF THE SHERBURXE SAXDSTONE 



Traced eastward along the outcrop, the Sherburne sandstone holds its 

 own as far as the Unadilla Eiver valley, some ten miles from Sherburne. 

 It everwhere rests upon the Hamilton shales and throughout is suc- 

 ceeded by shales with the Ithaca fauna. The Sherburne formation con- 

 sists of shales and micaceous sandstones, the latter characterized by the 

 markings termed Fucoides graphica by Vanuxem. In the Unadilla Eiver 

 section the TuUy and Genesee are absent, the unfossiliferous Sherburne 

 sands and shales resting directly upon the fossiUferous Hamilton shales 

 and sands. The transition from the Hamilton to the Sherburne is shown 

 in some of the sections along the brooks entering the Unadilla near Xew 

 Berlin. Prosser records the fact that in the dark shale beds immediately 

 above the fossiliferous Hamilton ^^only two fragments of a goniatite and 

 another of a different shell . . ."" were found. East of the I'nadilla, 

 in Otsego and Schoharie counties, the rocks of the horizon of the Sher- 

 burne sandstone, while retaining a somewhat similar lithic character, 

 have become more or less fossiliferous, the contained organic remains 

 being those of the Hamilton fauna. East of the Schoharie Valley, how- 

 ever, in Green and Ulster counties, these beds again pass into unfossili- 

 ferous bluish and grayish sandstones with intercalated red shales, con- 

 stituting the lower part of the Oneonta formation, or the Upper Flagstone 



s Loc. cit 



^ J. M. Clarke : Loc. cit.. pp. 205-207. 



