The Taconic sequence, predominantly argillaceous-arenaceous strata, is both autochthonous and allochthonous. The allochthonous rocks constitute the Taconic klippe, which extends from southeastern New York to west-central Vermont. They are of Cambrian(?), Cambrian, and early and middle Ordovician ages, as are the rocks of the autochthonous carbonate belt that surrounds the Taconic region. Autochthonous rocks of the Taconic sequence are middle Ordovician shale and graywacke that extensively overlie the carbonate rocks.

Complex geometric and spatial relations within the Taconic allochthon, and between it and the autochthonous rocks, involve regionally extensive, successive thrust slices, Wildflysch-type conglomerate, and cryptic sedimentary boundaries between the allochthon and autochthon.

In 1961, Zen proposed that the allochthon was emplaced by westward submarine gravity sliding of Taconic-sequence rocks into mud (now Normanskill shale) contemporaneously accumulating in a basin that developed within the region of the previous carbonate accumulation (now the autochthonous carbonate rocks). Fossiliferous, allochthonous, Taconic-sequence rocks, originally deposited on the east, represent deeper water, lateral facies correlatives of the carbonate rocks. Stratigraphic-structural relations between the allochthon and autochthon, and extensive Wildflysch-type conglomerate and associated flysch within Normanskill shale of Trentonian age, are direct evidence for the proposed Taconic submarine gravity sliding.