The concept of a klippe was applied to the Taconic region of the Hudson River valley to explain the occurrence, side by side, of contrasting facies of supposedly time-equivalent rock formations: the autochthonous carbonate sequence, and the clastic Taconic sequences interpreted as allochthonous. For the southern half of the Taconic region the structural evidence is incompatible with the hypothesis. An alternative view, which attempted to see in the two sequences facies deposited essentially in situ in one basin does not explain the remarkable uniformity of the carbonate stratigraphy over the whole region.

Field studies by the writer and several of his students have produced results that suggest that some of the stratigraphic units are not time equivalents as had been supposed. Three important unconformities, produced by broad arching and subsequent erosion, separate the following stratigraphic units: (1) The Lower Cambrian clastic series (Poughquag-Stissing in the south, Nassau-Schodack in the north) from the Upper Cambrian to Canadian carbonate series. Locally the latter lies on Lower Cambrian and even on the Precambrian. (2) The carbonate sequence from the Schaghticoke-Deepkill-Lower Normanskill shale sequence, which locally rests directly on the Precambrian or Lower Cambrian. (3) The Schaghticoke-Deepkill-Lower Normanskill series from an Upper Normanskill series (of Middle Trenton age) which transgresses far and wide across all earlier formations on to the Precambrian.

Most of the paper is devoted to specific evidence from over a dozen quadrangles. Twenty-nine critical localities are shown on a key map together with broad geologic features. A few significant structural details are illustrated with drawings and photographs.

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