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Document Type
Book Chapter
Department/Program
Virginia Institute of Marine Science
Editors
Bruce W. Nelson
Publication Date
1972
Book Title
Environmental Framework of Coastal Plain Estuaries
Publisher
Geological Society of America
City
Bolder
Volume
133
Series
Geological Society of America Memoir
Abstract
The James River estuary of the Chesapeake Bay region follows the course of a former river valley drowned within the last 9,000 years by the most recent rise of sea level. The floor is shaped into a central channel bordered by submerged shoals. Observations show suspended sediment is transported mainly by alternating tidal currents and secondarily by the net nontidal estuarine circulation. Transport results in a sequence of grain size distributions reflecting the mixing of two textural end members, clay and sand.
Silty clay is deposited in the river and upper estuary, whereas sand occurs near the mouth. Transitional types, clayey sand and sand-silt-clay, predominate in the middle estuary. Additionally, biogenic materials, oyster shells and fecal pellets, and small amounts of residual components eroded from older deposits are mixed into the sediments by currents, waves, and organisms. Bottom sediment types vary widely according to local relief, to varying intensity of environmental processes, and to changing rates of supply from different sources:
Deposition is greatest in the middle estuary where salinity ranges from 5 to 14 parts per thousand. An elongate zone of relatively high deposition in the lower estuary corresponds to the intersection of the level of no-net-motion with the bottom. Despite substantial infilling, it is believed the estuary is maintained by the continued rise of sea level and by currents that flush part of the river-borne load through the estuary.
Recommended Citation
Nichols, Maynard M., "Sediments of the James River Estuary, Virginia" (1972). VIMS Books and Book Chapters. 18.
https://scholarworks.wm.edu/vimsbooks/18
