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Burial History of Lockport Formation (Middle Silurian), New York, in Light of Studies of Ellenburger Group (Lower Ordovician), West Texas-Southeastern New Mexico

Yong Il Lee, Mustafa Ergin, Gerald M. Friedman

For studies of burial depth of the Lockport Formation (Middle Silurian) of the Appalachian basin, we used as a control data from petrographic, stable isotope, and two-phase fluid-inclusion analyses of carbonate rocks cored from 5,000 to 23,000 ft (1.5 to 7 km) burial depth of the Ellenburger Group, west Texas and southeastern New Mexico. The coarse to very coarse crystalline nature of the host-rock dolomite, the vug-filling and fracture-filling saddle dolomite containing relatively light oxygen isotope compositions ranging from -6 to -12 ^pmil (PDB), and the high mean homogenization temperatures for saddle dolomite formation from 100° to 260°C, all suggest diagenetic changes occurred under deep burial conditions.

Using Ellenburger carbonates as a control for burial depth diagenesis studies of saddle dolomite of the surface-exposed Lockport Formation, New York, other literature, and the regional conodont color alteration index (CAI) of 2-3, a former burial depth for the Lockport Formation strata of up to 5 km is indicated, much greater than the present estimation of less than 2 km of paleogeographic reconstruction. This depth was confirmed by ^dgr18O values ranging from -9 to -11 ^pmil, and two-phase fluid-inclusion homogenization temperatures ranging from 110° to 200°C with an average of 150°C.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.