James Dwight Dana and the Taconic controversy

Abstract

James D. Dana, being out of the country at the time, took no part in the early stages of the Taconic controversy (1840-1842). When he returned, he simply accepted the opinion of the majority, who rejected Emmons' claim that the Taconic System is separate from and entirely older than the New-York System-the well exposed and clearly displayed Lower and Middle Paleozoic stratigraphic sequence in New York State then being established by Emmons and his colleagues. When in 1861 Barrande showed that two trilobites described by Emmons in 1844 from a single locality in his Taconic slate were in fact "Primordial" (we would now call them Early Cambrian) and hence older than the oldest strata in the New-York System (Late Cambrian), Dana agreed to the age assignment. But he argued consistently that the validity of Emmons' Taconic System must be judged from the "original" or "true" Taconic of 1842, not from the greatly broadened Taconic of 1844 in which the trilobites were found. In 1871 Dana began fifteen summers of field work in the original Taconic region of Berkshire County, Massachusetts, and its extensions. Fossils had already been found and more were discovered, and they showed that at least the greater part of the "original Taconic" is in fact coeval with the lower part of the New-York System. But at the same time S. W. Ford showed that Emmons' trilobites and associated "Primordial" fossils are common in a belt west of the original Taconic region but between it and the established New-York System. Ford also showed that the contact of that belt with the New-York System to the west is not an unconformity, as Emmons had thought, but a major fault, comparable to the "great dislocation" found by Logan in the analogous position at Quebec City. Finally C. D. Walcott found additional fossil localities, which showed that both the original and the broadened Taconic include both strata older than and strata coeval with the New-York System; he concluded that the name Taconic has no further usefulness in stratigraphic nomenclature, and the matter was then considered closed. (The fossils also showed however that Dana's, as well as Emmons', concepts of the structure were far too simple, and they led to a second, 20th-century, Taconic controversy.)