11 Structural Geology and Tectonics (Posters)

Sunday, 22 March 2026
8:00 AM - 12:00 PM
CCC, Ballroom C

Borehole Geophysical Responses in Staten Island's Deepest Continous Corehole- Including Sepentines and Manhattan Schist( A) For matioins the Manhattan Prong

Paper number: 11-5
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

 

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Snug Harbor Pilot Borehole B1A, drilled ( 2006) and cored to a depth of 869' (263m) in Staten Island. It is  one of the deepest  continuously cored  borehole drilled in New York. The purpose of his presentation is to review the  Optical Televiewer (OTV), Acoustic Televiewer (ATV), Acoustic Caliper, Fluid Temperature, and Fluid resistivity geophysical logs  originally  for the NYC Department of Design and Construction by Hager-Richer Geoscience of New Jersey.

The the borehole geophysical logging results are1)The serpentinite between 194 feet and 353 feet deep is highly foliated and contains abundant light colored veins. And  falls into two distinct populations dipping to the northwest and southeast.2) 133 fractures were detected in the serpentinite.  The fractures mainly dip to the northwest, essentially parallel to the foliation.3)  An approximately 3½-foot thick shear zone is present near the base of the serpentinite between the depths of 318 feet and 321.5 feet . The shear zone dips to the south. There is no detectable water flow from the shear zone under ambient conditions.4) The  amphibolite schist between 353 feet and 362 feet deep and metasedimentary pelitic Walloomsac ( Manhattan Schist A )  to the bottom of the borehole at 870 feet is highly foliated but remarkably non-fractured. The foliation and veins in the schist consistently dip to the southwest. Only 31 fractures were detected in the 517 feet of schist. The fractures mainly dip to the southwest, parallel to the foliation, with a smaller population of fractures dipping northwest. The fluid temperature and fluid resistivity logs indicate  no water flow in the borehole under ambient conditions.

 The serpentinite ophiolite bodies, were accreted and thrusted over the Walloomsac metapelitic schist part of the  Laurentian Plate during the  Middle to Late Ordovician Taconic Orogeny. It’s orientation ( northwest-southeast) of foliation, fractures, and faults were result of obducted thrust sheets with the thin sliver of  upper mantle amphibolite( hornblende schist).  

The borehole reflects a complex Manhattan Prong geology from Staten Island New York to the western side of the Hudson River to Hoboken New Jersey. The Walloomsac Formation crosses the Hudson River (eastside) to Manhattan at Leroy Street and north to West 57th street, associated with serpentine and  outcrops at the Bronx Botanical Gardens.

 

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411103

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