GEOLOGY OF THE POUGHKEEPSIE QUADRANGLE 7/ 



elsewhere to the north toward Hopewell Junction and east toward 

 Stormville. The discussion of the structural features will bring out 

 the fact that there must have been a strong tendency toward crushing 

 and mashing along the limbs of minor folds within this formation. 



In the woods west of Wood's greenhouses at Fishkill Village are 

 numerous outcrops of a very fine-grained metamorphosed rock 

 which suggests an altered silicious ooze. It was noted in several 

 places within short distances of each other and not far from ledges 

 carrying Ophileta compacta. It appears to be a rather 

 abrupt variation of the rock with which it is associated, and prob- 

 ably is to be regarded as a variation of the Beekmantown, 



Certain varieties are plainly the products of metamorphism and 

 will be referred to again under that heading. 



In most cases, the lithology of the Fishkill limestones does not 

 convey anything definite of which one may make use for provisional 

 correlation. In the new cuts along the road from Brinckerhoff to 

 Stormville even the fresh surfaces convey very little. In some of 

 the ledges near Gayhead ^ the fresh surface carries numerous rusty 

 patches, possibly siderite, which recall some surfaces seen in the 

 quarry at Stoneco. ' 



The magnesian character of some of these limestones is well 

 known. There is some reason for thinking that they were accumu- 

 lated in somewhat restricted bodies of water. Possibly they are 

 partly the products of precipitation from saturated solutions. 



If during the time these deposits were accumulating there were 

 several basins more or less completely cut ofif from each other, it 

 is easy to understand that there would have been some diversity in 

 the condition of sedimentation in this region. In some places there 

 would have been normal marine conditions with characteristic 

 animal forms, while in others, perhaps, there would have been an 

 accumulation of sediments peculiar to basins more or less com- 

 pletely cut off from the sea with an absence of animal forms. An 

 influx of the sea in these restricted basins would carry with it a 

 change in sediments and a marine fauna and a fossiliferous lens 

 might thus be produced within a barren dolomite. 



The absence of the conglomerate and overlying formations over 

 most of the Fishkill limestone indicates that it is composed chiefly 

 of older strata, probably ranging discontinuously from Lower 

 Cambric to Beekmantown. As the folds in the limestones are 



1 East Fishkill is invariably referred to as '' Gayhead," in this region. The 

 name seems to have originated from the head adornments of the ladies v^ho 

 flocked to this place for dance festivals in early years. 



