Stratigraphy and structure of the Ganson Hill area: northern Taconic Allochthon

The Ganson Hill study area is located in the Giddings Brook Slice of the Taconic Allochthon. It contains rocks of Cambrian(?), Cambrian and Ordovician age. The predominant rock type is slate with subordinate lithologies including quartzite, limestone, micrite, arenite and graywacke. The lithostratigraphy identified in the Ganson Hill area extends from the basal Bomoseen wacke to the Poultney slate. A more precisely defined lithostratigraphy is derived from the study area by the occurrence and recognition of the Middle Granville Slate Formation and the documentation of a second Cambrian black/green boundary. Previous workers have included this formation in different places, in two different formations creating much confusion. Three stages of deformation have been recognized in the Ganson Hill study area. They are: pre-slaty cleavage folding, slaty cleavage development with associated folding, and faulting and seen only sporadically, crenulation cleavage development with associated folding and faulting. Documented in this thesis is the Hubbardton Gulf Thrust Fault which places Cambrian green slate (Undifferentiated Bull Fm.) over black and gray slate with interbedded quartzite (Poultney Fm.). An early Ordovician contourite deposit has been identified in the Poultney unit. The grain size, the composition and the lateral extent of the quartz-rich beds in the Poultney Formation in addition to sharp top and bottom bedding contacts and preserved sedimentary structures are distinguishing characteristics of the contourite deposit. Paleocurrent directions indicate northerly flowing bottom currents depositing and reworking material fed from the North American Platform adjacent to and south of the present area of the Taconics