Abstract

Fold structures in Cambro-Ordovician schists of the Stoke Mountain complex are compared with similar structures in adjacent Middle Ordovician and Siluro-Devonian slaty rocks. Schistosity in the complex lies parallel to the axial surfaces of obscure F1 folds. F2 isoclines in the schistosity and first generation isoclinal folds in bedding within the Siluro-Devonian rocks are essentially coplanar and coaxial; both are steeply inclined and plunge dominantly northeast. Parallel folds in Middle Ordovician and younger rocks apparently pass upward into Siluro-Devonian strata. Hence the F2 folds are plausibly correlated with those in the Siluro-Devonian rocks, which are of Acadian (mid-Devonian) age. Nevertheless, the steeply inclined F2-type folds in the Middle Ordovician rocks can be traced northeast along the Appalachians to localities where they are truncated by an angular unconformity beneath Siluro-Devonian rocks. It is evident that here the folds are not Acadian but late Ordovician (Taconic) structures.The conflicting evidence as to the age of the F2-type folds, which is not resolved by radiometric data, casts doubt on both local and regional correlations based on fold form and orientation.

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