Bedrock geology of the Paleozoic rocks of western New Haven quadrangle, Connecticut

The Paleozoic rocks underlying the western third of the New Haven Quadrangle, Connecticut, are mapped at a scale of 1:24,000. This area of ∼41.5 km2, previously mapped only in reconnaissance, contains polymetamorphic argillites and mafic rocks. The northern portion of the mapped area contains the pelitic Wepawaug schist, whereas the southern portion is underlain by the pelitic Savin Schist. Between them lies the Maltby Lakes Complex (MLC) that contains newly identified fault slivers of variably metamorphosed mafic phyllites and amphibolites. Metamorphic foliations in both the MLC and the Savin Schist are truncated by a swarm of basalt dikes: the Allingtown porphyry, which is itself commonly schistose and locally mylonitic. Previous interpretations held that these rocks constitute a conformable, northwest-topping stratigraphic sequence. In contrast, we propose that Ordovician(?) oceanic rocks of the MLC were variably metamorphosed and faulted against the Ordovician(?) Savin Schist. These were intruded by a swarm of stitching Allingtown dikes. This package of rocks was then faulted against Siluro-Devonian(?) Wepawaug forearc sediments. Existing thermochronology indicates a Devonian age of the subsequent regional metamorphism, overprinted by low-grade Permian fabrics associated with dextral transpression and final terrane assembly.