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The glaciated, passive continental margin of northern New England is not a likely location for either tectonic activity or hydrocarbon accumulation, but neotectonic action has played a role in creating favorable stratigraphic traps for natural gas in the Quaternary inner-shelf and estuarine deposits of Maine. During late glacial time (13,000 years B.P.), a marine inundation accompanied ice retreat across the isostatically depressed lowlands of coastal Maine and blanketed the area with marine sediment (Presumpscot Formation) up to 50 m thick. Unloading of the ice led to rapid coastal rebound within a few thousand years, and the former sea floor became emergent to present depths of -65 m. A gullied and weathered lag surface on the muddy Presumpscot Formation marks the regre sion that followed deposition. Since about 8,000 years B.P., sea level has risen in Maine, and within historic times it has been accompanied by seismicity and subsidence rates up to 9 mm/yr. Examinations of over 1,500 km of seismic reflection profiles and limited coring reveal the presence of abundant natural gas in Holocene sediments filling ravines cut into the Presumpscot Formation during emergence. It appears that the gas is derived from the trapped by mud deposited in estuarine depocenters that migrated landward during the Holocene transgression.
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