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Development of a salt marsh on the Fraser delta at Boundary Bay, British Columbia, Canada

University of British Columbia

The development of a late Holocene salt marsh was studied on the inactive part of the Fraser Delta at Boundary Bay, southwestern British Columbia. Present-day vegetation zones near 64th Street, South Delta, in the western part of the Bay, were distinguished in the salt marsh and were related to zones found in cores obtained in a transect across the marsh. A sequence of development, related to elevation, was determined. Salicornia and Triglochin are pioneer colonizers of the tidal flats and are sometimes associated with areas elevated by algal mats. As the area was elevated, sediments were trapped by vegetation and stabilized by rhizomes, and other halophytes grew, including Cuscuta, Sperqularia, Atriplex, Distichlis, Grindelia, and Plantago. A zone characterized by abundant Atriplex represents positions of former strandlines. As further emergence occurred, mesophytes became dominant and, in the landward, most emergent zone, a diverse flora of Maius, Sjdalcea, Aster, AchiIlea, Solidaqo, Elymus, Angelica, Juncus, and grasses developed. A radiocarbon date on Salicornia-rich organic silts at a depth of 35 to 40 cm in core 5 suggests that salt marsh development commenced 320 ± 70 years B.P. (GSC-3186). A former salt marsh peat is now partially buried and being actively eroded where exposed near 112th Street, South Delta, in eastern Boundary Bay. A paleoenvironmental reconstruction suggests the peat started developing in freshwater, with ferns, sedges, Typha, and Nuphar. Later, it was successively inundated by marine water and a salt marsh developed, as seen by an increase in the abundance of chenopod pollen. Subsequent emergence of the salt marsh was accompanied by the development of an increasingly diverse vegetation.

Text

2010-03-26

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http://hdl.handle.net/2429/22590

Geological Sciences

University of British Columbia

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