Mount Merino Chert and Shale, Middle Ordovician, is one of the most siliceous units of the Taconic sequence (eastern New York and western Vermont); it is composed of interbedded shale, siliceous hale, argillite and chert. Non-clastic quartz — aggregates of quartz having a.mosaic or felted texture — predominates in all beds, except `shale. All siliceous beds are finely laminated; most laminae are distinguished from adjacent laminae by the texture of the quartz groundmass, and the amount of clastics, carbonates, chlorite and sulphides. Statistical comparison of the textures of the quartz aggregates which occur with the other mineral components suggests that the components of each lamina represent a stable mineralogic assemblage; the assemblages probably formed during silica precipitation and early diagenesis. These assemblages are compositionally-consistent with experimental data regarding the formation of authigenic minerals in the presence of colloidal silica.
Mount Merino rocks comprise a minor.part of the Giddings Brook slice of the Taconic allochthon; the Mount Merino fauna is the youngest of the Giddings Brook slice rock sequence. Mount Merino rocks also occur as boulders and blocks in Forbes Hill Conglomerate, an autochthonous wildflysch-like terrain underlying the Giddings Brook slice.
Petrographic aspects of Mount Merino rocks indicate a "starved" depositional environment distant from an extensive land area. The predominant source of silica for the rocks was probably vulcanism (the Ammonoosuc volcanics) which became relatively intense during Mount Merino time, just preceding emplacement of the Taconic allochthon.
Lang, D.M., 1969. Origin of the Mount Merino Chert and Shale,
Ordovician, Eastern New York State.
Unpublished MSc. thesis, State University of New York at Albany. 64pp., +v, +26p. tables.
University at Albany Science Library call number: SCIENCE Oversize (*) QE 471 L325X
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