LINEAR TRACINGS USED TO DETERMINE SUBSURFACE STRUCTURES IN ORDOVICIAN FLYSCH II

This poster is a continuation of the research presented in Poster Session 30 at the Annual Meeting in Boston (Abstract 29289). There is now better resolution between the location of linears traced from remotely sensed imagery to surface and subsurface fractures on the ground. Bore hole BHN87-2, which is in the vicinity of the pinch-out, or funneling of the middle unit (Ramseyburg) of the Martinsburg Group equivalents in SE New York, shows very high fracture frequencies. This bore hole and the strike of surface outcrop in the area is located in alignment with the course of the Wallkill River, and what may be a fault trace. The approximate location of this borehole is at N41 37'50"Lat., W74 13'01"Long. The geological map of the area which was prepared by Kirby Young for the EBASCO study shows a widening of the mapped Ramseyburg from less than a mile near the bore hole to over six miles across a zone almost centered on the coordinates N41 30'Lat., W74 22'30". The N41 30' Latitude is close to the latitude of a major splaying of the Ramapo Fault to the east of this area. The story which seems to be unfolding could be of differntial movements along major long-lived crustal shears. Such movements could produce rapid thinning of units by elevating or lowering preexisting floating basement blocks, or by rotating them. cf Kingma, J.T. (1958):Possible Origin of Piercement Structures, Local Unconformities and Secondary Basins in the Eastern Geosyncline, New Zealand, N.Z. J. Geol. , Geophys. V1, p. 269-74.