Geology topics
James B. Thompson
Publications and source records attributed to James B. Thompson.
A guide to continent-ocean transect E-1: Adirondacks to Georges Bank
The geologic strip-map for Transect E-l cuts a swath from the Thousand Islands region on the New York-Ontario border to the Atlantic Ocean floor off Georges Bank (see Fig. 1). It includes portions of New York, Ontario and of all of the New England states. The western part, mainly in New York, belongs to the North American craton. The remainder of the onland portion, east of Logan's Line, belongs to the Appalachian Orogen. Southeastward from Logan's Line the transect crosses a series of distinctive terranes. Several of these terranes are believed to be exotic, and to have been accreted to the North American craton during the Paleozoic. Superposed on these are several grabens and half-grabens containing early Mesozoic sediments and mafic volcanics. There are also Mesozoic eruptive complexes of an alkalic nature cutting across the Appalachian Orogen from southern Quebec, across New England, and continuing as a chain of seamounts offshore. Cenozoic rocks are limited to a small, but significant occurrence near Brandon, Vermont (BL on Fig. 2) and a few occurrences in the Cape Cod region and on the adjacent islands in southeastern Massachusetts.
Metamorphosed middle Paleozoic fossils from Central Massachusetts, eastern Vermont, and western New Hampshire
Study of thin and polished sections and spectrographic analyses indicate that the brachiopod most recently used to date the Bernardston Formation in Massachusetts probably came from Lower Devonian beds (chlorite zone) in Nova Scotia, and not from Bernardston, Massachusetts. Restudy of the faunule from the calcareous quartzite (garnet zone) of the Bernardston Formation indicates that it is probably of Silurian rather than Devonian age. The upper part of the Clough Formation on Skitchewaug Mountain (garnet zone) in eastern Vermont contains tetracorals of Silurian or Devonian age. The Clough Formation on Croydon Mountain (sillimanite zone) in west-central New Hampshire contains tetracorals. The fossiliferous zone in the lower part of the Bernardston Formation is possibly equivalent to the upper part of the Clough Formation.