Stratigraphic implications of facies within the Boston Basin
Anthony D. Socci, Geoffrey W. Smith, 1990. "Stratigraphic implications of facies within the Boston Basin", Geology of the Composite Avalon Terrane of Southern New England, Anthony D. Socci, James W. Skehan, Geoffrey W. Smith
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Based on a detailed analysis of facies assemblages within the Boston Basin (Boston Bay Group), we have concluded, to a first approximation, that the Boston Bay Group was originally laid down as a sequence of inclined strata that appears to have formed a submarine fan/slope/apron at unknown water depths. There appears to be a systematic progression of facies and the imprints of depositional mechanisms from the southern (more proximal) portion of the basin, in the vicinity of Nantasket and Hingham, to the northern and northeastern (more distal) portion of the basin, in the vicinity of Newton and Somerville. In the more proximal areas of the basin, the facies assemblages are characterized by bouldery and cobbly debris-flow deposits and high-density turbidites; in the more distal reaches of the basin, the facies assemblages are characterized by high-to low-density turbidites, pebbly and cobbly high-density turbidites and/or debris-flow deposits, and traction-generated features. Syndepositional slump features are ubiquitous, and dropstones are present in most fine-grained facies investigated. The rocks appear to have been transported into the basin from the south and possibly from the west.
Consequently, on the basis of our investigation of facies assemblages, we are forced to conclude that the historic stratigraphy and stratigraphic units of the Boston Basin are suspect. Insofar as this historic stratigraphy has at times been used to infer the presence of structure, and insofar as this stratigraphy has been used as the basis for interpreting the depositional history of the Boston Basin, we are also forced to conclude that many of the stratigraphically derived interpretations of the depositional history of the Boston Basin, as well as some unknown parts of the structure, are also suspect.