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Articles |
New York State Museum, The State Education Department, Albany, NY 12230, USA (e-mail: cverstra{at}mail.nysed.gov)
A new synthesis of the Lower to Middle Devonian (upper Pragian, Emsian and Eifelian) succession across the Appalachian Basin has been developed by high resolution event and sequence stratigraphic analysis. The correlation of numerous marker beds and a hierarchy of cycles in the interval of the Oriskany Sandstone to lower Hamilton Group provide a refined picture of the depositional patterns, faunal changes, formation to member-level (and finer) relationships, and sea-level trends. The succession begins above the Wallbridge Unconformity, or its correlative conformity, which lies beneath the Oriskany Sandstone, not above it as previously thought. The new sequence-stratigraphic framework of Oriskany to lower Hamilton strata comprises nine ‘third order’ stratigraphic sequences (cycles), though an interval of some 25 million years. At a coarse scale, the eustatic Pragian to Eifelian sea-level curve for Euramerica of Johnson et al. (1985) shows broad variance with the Appalachian curve, reflecting the regional influence of the Acadian orogeny. However at the finer sequence-scale, the Euramerican sea-level trends are recognizable in the Appalachian Basin succession.
