The Flanner Beach Formation was deposited along the Atlantic Coast of North Carolina, during a high stand of sea level about 200,000 years BP. The formation consists of three members in the Neuse River valley: (1) Smith Gut member (new unit), deposited in early transgressive, open bay settings; (2) Arapahoe sand member, deposited in barrier island environments as rate of sea level rise decreased; and (3) Beard Creek member, composed of bay and lagoonal sediments that accumulated in varied estuarine settings landward of the Arapahoe barrier. Time-equivalent deposits along the Pamlico River also consist of three members: (1) Hills Point member (new unit), deposited in restricted lagoonal or river estuary settings; (2) Mauls Point member (new unit), deposited in open lagoonal areas; and (3) an unnamed member resembling the Beard Creek Paleoecologic units identified in the Smith Gut and Beard Creek members included, in ascending stratigraphic order: (1) polyhaline, open bay fossil associations; (2) polyhaline, slightly restricted bay associations; (3) mesohaline, restricted lagoonal associations; (4) polyhaline, open lagoonal associations; and (5) a mesohaline (?), firm-ground association. The sequence of mollusk-dominated associations reflects changes in composition and structure of intergrading, soft-bottom communities that responded to gradual alterations in water circulation patterns, salinity, intensity of seasonal environmental rigor, and to a lesser extent slight changes in bathymetry and substrate properties, during the evolution of a major barrier-lagoon system. This long-period change in benthic communities is an example of gradual community replacement--the substitution of one community of organisms for another in space and time owing to gradual changes in environmental contexts, yielding a sequence of fossil associations each with slightly different paleosynecologic attributes Gradual replacement is dominated by processes of reorganization of species-abundance patterns, with faunal turnover playing a relatively minor role. In rapidly changing environments, turnover is the dominant mechanism of replacement. Reorganization appears to involve the following processes in estuarine benthic communities: (1) changes in numerical importance of superdominant taxa; (2) shifts in rank levels of subdominant taxa; (3) large changes in rank levels of numerically minor taxa; and (4) gradual demotion of certain taxa to lower rank levels through the preserved community sequence. Simple additions and deletions of minor faunal elements also can occur / acase@tulane.edu
| Identifer | oai:union.ndltd.org:TULANE/oai:http://digitallibrary.tulane.edu/:tulane_24822 |
| Date | January 1984 |
| Contributors | Miller, William Charles, Iii (Author) |
| Publisher | Tulane University |
| Source Sets | Tulane University |
| Language | English |
| Detected Language | English |
| Rights | Access requires a license to the Dissertations and Theses (ProQuest) database., Copyright is in accordance with U.S. Copyright law |
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