Late Quaternary history of southern Chesapeake Bay

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

OSTI ID:6646492

Colman, S M; Hobbs, III, C H; Halka, J P

More than 700 km of high-resolution, seismic-reflection profiles and sidescan-sonar images provide new information about the late Quaternary history of southern Chesapeake Bay. Sidescan-sonar images show that, excluding the nearshore zone, most of the bay bottom has a monotonously smooth surface, except that sand waves, ripples, and other bedforms occur in local areas affected by tidal currents. Seismic-reflection data show that the Quaternary stratigraphy of the southern part of the Bay is related primarily to the last cycle of sea-level change. The Quaternary section overlies an erosion surface cut deeply into gently seaward-dipping marine beds of Neogene age. Fluvial paleochannels, related to the last major low sea-level stand, are characterized by as much as 55 m of incision and by thin, irregular, terrace and channel-bottom deposits. Marine and estuarine deposits related to the Holocene transgression partially or fully bury the fluvial valleys and overlie the interfluves. A prominent feature of the Bay-mouth area is a wedge of sediment that has prograded into the Bay from the inner shelf. The common assumption--that the Chesapeake Bay is the drowned valley of the Pleistocene Susquehanna River--is only partially valid for the southern part of the Bay. The Bay mouth area, in general, is relatively young. The axial channel of the Bay is a modern tidal channel that is actively eroding Tertiary deposits and migrating toward the south and west; it is unrelated to older fluvial channels. Also, the positions of the modern axial channel and the last two fluvial paleochannels indicate long-term southward migration of the Bay mouth.

• Research Organization: Geological Survey, Woods Hole, MA (USA)
• OSTI ID: 6646492
• 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)
580203 -- Geophysics-- Geophysical Survey Methods-- (1980-1989)
ACOUSTIC MONITORING
ATLANTIC OCEAN
BAYS
CENOZOIC ERA
CHESAPEAKE BAY
GEOLOGIC AGES
GEOLOGIC HISTORY
GEOLOGY
GEOMORPHOLOGY
GEOPHYSICAL SURVEYS
MEASURING INSTRUMENTS
MONITORING
QUATERNARY PERIOD
RANGE FINDERS
SEA BED
SEAS
SEDIMENTS
SEISMIC SURVEYS
SONAR
STRATIGRAPHY
SURFACE WATERS
SURVEYS