Recognition of extensive freshwater and brackish marshes and of multiple transgressions and regressions: The Holocene wetlands of the Delaware Bay and Atlantic Ocean coasts
- Univ. of Delaware, Newark, DE (United States). Dept. of Geology
Extensive and closely spaced cores (204) were analyzed to find detailed facies (microfacies) and paleoenvironments in the subsurface sediments along the Delaware Bay and Atlantic Ocean. To determine detailed facies and paleoenvironments, several composite methods were employed: traditional lithological analysis, botanical identification, macro- and micro-paleontological analysis, grain size analysis, organic and inorganic content, water content, mineral composition, particulate plant, and C-14 dating. Twenty-two sedimentary microfacies were identified in the surface and subsurface sediments of the study area. Most of the lower section of the Holocene sediments contained freshwater and brackish marsh microfacies which alternated or intercalated with fluvial microfacies or brackish tidal flat/tidal stream microfacies. After tides encroached upon the freshwater marshes and swamps, several events of transgression and regression were recorded in the stratigraphic section. Finally, saline paleoenvironments predominated at the top section of subsurface sediments. Within saline facies, three subgroups of salt marsh microfacies were identified: high salt marsh sub-microfacies, middle salt marsh sub-microfacies were identified: high salt marsh sub-microfacies, middle salt marsh sub-microfacies, and low salt marsh sub-microfacies. The major controlling factors of these paleoenvironmental changes were local relative sea-level fluctuations, sediment supply, pre-Holocene configuration, fluvial activity, groundwater influence, climatic change, sediment compaction, tectonics, isostasy and biological competition. Ten events of transgression and regression in some areas were found in about 2,000 years, but other areas apparently contained no evidence of multiple events of transgression and regression. Some other areas showed one or two distinctive events of transgression and regression. Therefore, further investigation is necessary to understand the details of these records.
- OSTI ID:
- 5936803
- Report Number(s):
- CONF-921058-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 24:7; Conference: 1992 annual meeting of the Geological Society of America (GSA), Cincinnati, OH (United States), 26-29 Oct 1992; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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