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Types and Origin of Dolomites in the Beekmantown Group (Cambro-Ordovician) of New York

Mossbah M. Kolkas1 and Gerald M. Friedman2

1Department of Natural Science, Bard Early College, New York, NY 10002 and Department of Engineering Science and Physics, The College of Staten Island (CUNY), Staten Island, NY 10314.

2Northeastern Science Foundation, Rensselaer Center for Applied Geology, Troy, NY 12181.

Petrographic and geochemical studies of selected samples from the Beekmantown Group (Cambro-Ordovician) of central and western New York revealed six dolomite textures. These dolomite textures have been classified based on crystal sizes, shapes, uniformity, and trace element distribution. These textures are as follows: 1) unimodal, very finely crystalline, planar-e (euhedral) dolomite, 2) unimodal, very finely crystalline, plannar-s (subhedral) dolomite, 3) medium to coarsely crystalline, planar-e (euhedral) dolomite, 4) coarsely crystalline, non-planar dolomite (non saddle dolomite), 5) very coarsely crystalline, non-planar dolomite (saddle dolomite), and 6) polymodal dolomite.

These dolomite types may be originated as replacement dolomite, primary dolomite (penecontemporaneous), and void filling dolomite.

In places, the process of dolomitization was interrupted by silicification, chemical compaction (stylolitization), and dedolomitization (calcitization).

Chemical analysis using electron microprobe indicates the presence of varies trace-chemical elements including iron, manganese, strontium, and silicon in the dolomite textures. These elemental variations and their concentration values strongly indicate that dolomites of the Beekmantown Group form under various conditions within different environmental settings.

 

AAPG Search and Discovery Article #90059©2006 AAPG Eastern Section Meeting, Buffalo, New York