CAPE COD GEOLOGY 



181 



Conditions during deposition. — The conditions during the deposition of the 

 Herod gravel were those due to an invading ice sheet. In addition there may 

 have been a slight shallowing of the water, as the type of deposit formed suggests 

 that the water was shallower than it was during the deposition of the Jacob 

 sand; but the change in the type of deposit may perhaps be better explained 

 by the change in conditions due to the approach of the ice. Deposition was 

 greatly accelerated by the increase in the volume of water pouring from the 

 melting ice and by the increase in the amount of material fed to the water by 

 the ice. The climate was probably colder and precipitation was probably greater 

 in Herod than in Gardiners and Jacob time. The currents were stronger, and 

 other agencies were more active. Near the end of Herod deposition the water 

 in this region had grown much shallower, largely because of the great quantity 

 of gravel laid down. 



Distribution. — The Herod gravel is the most widely distributed member of 

 the Manhasset formation, the Montauk and Hempstead members being of smaller 

 areal extent. The Herod probably covers a larger area than any other Pleistocene 

 deposit on Marthas Vineyard. The smaller areal extent of the two later Man- 

 hasset members is not due to their smaller areal deposition but to their greater 

 erosion during the Vineyard stage, which preceded the Wisconsin stage. The 

 Herod gravel flanks both sides of the western area and doubtless underlies 

 both the northeastern area and the great plain. It is well exposed in the Stone- 

 wall Beach (fig. 15), Nashaquitsa, Cedar Tree Neck (figs. 14 and 16), and Gay 

 Head cliffs. Along the northwest shore it is seen in nearly all the cliffs, es- 



Fig. 14. — Section one mile south of Cedar Tree Neck. Man- 

 hasset formation in morainal topography. A, Herod 

 gravel member; B, Montauk till member. 



pecially north of Prospect Hill and at Norton Point. As the Herod gravel 

 is much like the Hempstead and the Wisconsin gravel, it cannot easily be 

 distinguished from these in the interior of the island, for exposures are scarce 

 and more than one formation must be exposed in order to permit identification 

 of any one. Where the Montauk till and an underlying gravel are exposed the 

 gravel is usually the Herod. Some such exposures are seen along the State road 

 in Gay Head and Nashaquitsa, but very few are seen on the roads in the rest 

 of the western area. 



