Structural Implications of Walloomsac and Hartland Rocks Displayed by Borings in Southern Manhattan

indicates that the m ap of Baskerville (1994) is incorrect in that he identifies the region to be underlain by Manhattan Schist. Rather, internally sheared and migmatized units of the Hartland and Walloomsac formations and associated granitoid rocks clearly predominate. This extended abstract outlines the distinction between the various schist units in four of the more interesting sites and offers preliminary views of structural and tectonic implications of our findings. GEOLOGY OF NEW YORK CITY NYC's durable underlying structure consisting of glacially-sculpted Paleozoic and older crysta lline rock has enabled the construction of enormous towering skyscrapers and has supported the construction of multiple levels of subsurface engineering. First studied by naturalists in the 1700's, and by geologists in the 1800's and 1900's, the bedrock geology of the NYC area was mapped in systematic detail beginning in the mid- to late 1800's by L. D. Gale (1839, 1843), W. W. Mather (1838, 1840,1843), and F. J. H. Merrill (1890, 1898, 1902). NYC is situated at the extreme southern end of the Manhattan Prong, a northeast-trending, deeply eroded sequence of metamorphosed Proterozoic to Lower Paleozoic rocks that widen northeastward into the crystalline terrains of New England. Southward from NYC, the rocks of the Manhattan Prong plunge unconformably beneath predominately buried Mesozoic rocks, Cretaceous strata, and overlying Pleistocene (glacial) sediment that cap Long Island and much of Staten Island. Bedrock Stratigraphy of New York City