Holocene depositional history of a large glaciated estuary, Penobscot Bay, Maine

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6321400

Knebel, H J

Data from seismic-reflection profiles, sidescan-sonar images, and sediment samples reveal the Holocene depositional history of the large (1100 km/sup 2/) Penobscot Bay estuary of coastal Maine. Isostatic recovery of the crust caused the bay to emerge during the immediate postglacial period, and relative sea level stood at about -40 m sometime between 9000 and 11,000 years ago. During the postglacial low stand, the ancestral Penobscot River flowed across the subaerially exposed head of the bay and debouched into Middle Passage. Organic-matter-rich silty clays form the river were deposited in the glacially eroded lower reaches of Middle and West Passages behind a shallow bedrock sill at the mouth of the bay. East Passage was isolated from the rest of the system and received only small amounts of locally derived sediment. During the ensuing Holocene transgression, the locus of sedimentation shifted to the head of the bay. Here, fluvial sediments filled the ancestral channels of the Penobscot River as base level rose, and the migrating surf zone created a gently dipping erosional unconformity, marked by a thin, reworked lag deposit of coarse sand and gravel. As sea level continued to rise, a relatively thick layer (as much as 15 m) of silty clay was deposited at the head of West Passage. During and since the transgression, tidal currents and waves have eroded and reworked Holocene deposits along the shore, within restricted channels, around topographic highs, and over the shallow bay-mouth sill.

• Research Organization: Geological Survey, Woods Hole, MA (USA)
• OSTI ID: 6321400
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580100* -- Geology & Hydrology-- (-1989)
CENOZOIC ERA
COASTAL REGIONS
ESTUARIES
FEDERAL REGION I
GEOLOGIC AGES
GEOLOGIC HISTORY
GEOLOGY
GEOPHYSICAL SURVEYS
GLACIERS
LEVELS
MAINE
NORTH AMERICA
PALEOCLIMATOLOGY
PALEONTOLOGY
QUATERNARY PERIOD
SEA LEVEL
SEDIMENTS
SEISMIC SURVEYS
STRATIGRAPHY
SURFACE WATERS
SURVEYS
USA
VARIATIONS