Abstract 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. Offshore the corridor passes over the Gulf of Maine and Long Island Platforms, thence across Georges Bank and into the North Atlantic Basin. The Gulf of Maine and Long Island Platforms (Fig. 2) are underlain by Paleozoic metamorphic and plutonic rocks and early Mesozoic grabens, as in the adjacent onland regions, but are partially covered offshore by a 1-3 km section of late Mesozoic and

Abstract Sea-level changes have had an important influence on the distribution of late Quaternary inner continental-shelf sediment in the western Gulf of Maine. Previous stratigraphic models of sea-level change in the region were based on terrestrial observations and a large quantity of offshore high-resolution seismic-reflection data. These models, however, were not constrained by core data. Integration of new vibracore data with earlier observations indicates that nearshore regions were (1) probably deglaciated and subjected to glacio-marine conditions around 13.5 ka, (2) subaerially exposed by a fall in sea level sometime after 11 ka, and (3) flooded by a transgressing sea following an inferred lowstand of sea level between 11 and 9 ka. The greatest amount of sediment accumulated on the shelf during the initial transgression, under glacio-marine conditions. Sandy fluvial sediment accumulated in large quantities during the following regression and early Holocene transgression. Sediment influx from eroding bluffs of glacial origin was significant throughout the Holocene transgression, especially in regions lacking a fluvial source.

Glacial marine sedimentation dominated the inner shelf and coastal lowlands of Maine between ca. 14,000 and 11,000 B.P. Three major seismic facies interpreted as glacial marine deposits beneath the inner shelf are identified by recent high-resolution seismic reflection profiling. These are: (1) GM-M, massive glacial marine sediment, a uniform, draping blanket with abundant ice-rafted detritus, either mud or diamicton; (2) GM-D, conformable glacial marine mud, with a distinct draping geometry, usually well stratified; and (3) GM-P, less well-stratified glacial marine mud with a distinctly ponded, variable geometry. These glacial marine facies are associated with underlying seismic facies interpreted as till, stratified drift and bedrock, and overlying seismic facies interpreted as Holocene littoral and marine facies. The glacial marine facies are contained within one of two seismic stratigraphic sequences, which record rapidly changing sea levels and sedimentary environments. Sequence G is composed of till, stratified drift, and glacial marine mud. It records the deglaciation of the northern Gulf of Maine and Maine coast. It is overlain by a distinct unconformity above the −60-m sea-level lowstand, which grades to a conformity in deeper basins, further overlain by seismic sequence H. A critical issue concerning deglaciation of the area is identification of deglacial environments. A working hypothesis is that the initial deglaciation, ca. 18,000 to 14,000 B.P., was through a series of small, topographically buttressed, warm-based ice shelves, which were abundantly productive of poorly sorted sediment. These shelves may have formed and disintegrated in a sequential stepwise fashion, temporarily grounding on highs north of the major basins in the Gulf of Maine. After about 14,000 B.P., the ice front was a calving embayment, producing ice-rafted detritus, turbid suspensions, and subaqueous outwash. After 12,500 B.P., the ice margin was terrestrial, feeding melt-water streams and producing little ice-rafted detritus. The Maine inner shelf preserves this sequence in shelf valleys. Elsewhere, erosion during local relative sea-level changes has stripped bedrock highs of the majority of sediments, between the −60-m isobath and the inland marine limit (60- to 132-m elevation).