Mineral found in granite radiometric dating

The Manhattan Schist is an allochthon, a detached sheet of rock (Figure 2), and its age and origin have been unclear.

Zircons from the Yonkers gneiss in Westchester County have been dated at 563 Ma (Rankin and others, 1997), compatible with Late Neoproterozoic rifting elsewhere.For over twenty years we have studied the Manhattan Prong, principally in Westchester County.Field geology- the mapping of rocks and geologic structures, together with petrography- has been the springboard of our work, though we have been supplementing these with electron-microprobe studies of mineral assemblages, whole-rock geochemical analyses, and radiometric age determinations.In recent years we have proposed new interpretations of the metamorphic, stratigraphic, and tectonic histories of the Manhattan Prong (see, for instance, our abstracts for the Long Island Geologists conferences in 1998, 1999, and 2001).Here, we provide a brief outline of the geologic history of the region, which is also summarized on Table 1, Simplified Geologic History of the New York City Area.

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