Reinterpretation of Cambrian--Silurian-Devonian unconformities, southeast coastal Maine

摘要

Differentiated volcanic rocks and co-magmatic plutons in southeast coastal Maine have been mapped as Silurian to Devonian in age. They are flanked by volcaniclastic and pelitic rocks considered Upper Cambrian to Lower Ordovician based on isotopic and paleontologic dating, and because of fragmental rocks, interpreted as representing erosional unconformities between the lavas and pelites. However, metal deposits contained within both lithologies have trends in form and element assemblages consistent with progression from proximal, through distal, to basinal volcanic environment. Therefore, we have re-evaluated the stratigraphy and the criteria on which relative ages were assigned previously.