Surface distribution of Foraminifera in a New England salt marsh: Plum Island, Massachusetts
DOI :
https://doi.org/10.4138/1628Résumé
Salt marsh agglutinated foraminiferal assemblages, floristie zones and environmental subdivisions along the Plum Island barrier island system in Massachusetts resemble the zonation pattern for coastal marshes in the Maritime Provinces of Canada. Forty-three surface samples from high marsh, low marsh, tidal channel margin and elevated surface environments yielded seven species: Trochanmina macrescens, Tr. Inflate, Miliammina fusca. Tiphotrocha comprimata. Amotium sal sum, Haplophragmoides bonplandi, and Arenoparelia mexicana. Analysis of the dead to living ratios does not show a significant preservational difference among the salt marsh environments. Analysis of the total distributions indicates significant differences among the foraminiferal assemblages as a function of surface environments. The high marsh is characterized by Trochanmina macrescens, Tiphotrocha comprimata and two of the lesa common species. The low marsh is characterized by Miliammina fusca, Trochanmina inflate, and Ammotium salsum. The tidal channel margin assemblage is similar to that of the low marsh except that Ammotium salsum is no longer significant. Although the elevated marsh surfaces contained no living specimens, a high marsh type assemblage of dead specimens was present. These cosmopolitan foraminiferal assemblages should be valid discriminators for the reconstruction of Holocene salt marsh paleoenvironments in many regions. RÉSUMÉ Dans les marais salants longeant le système de flèches littoralea de Plum Island, au Massachusetts, les assemblages de foraminifères agglutinants, les zones floristiques et les subdivisions environneroentales observés ressemblent au zonage des marais côtlers des Maritimes. Quarante-trois écbantillons de surface des slikkes, schorres, chenaux de marée et bancs de surface élevés ont livre sept espèces: Trochanmina macrescens, Tr. Inflate, Miliammina fusca. Tiphotrocha comprimata. Amotium sal sum, Haplophragmoides bonplandi, et Arenoparelia mexicana. Une analyse des rapports morts/vivants ne montre aucune différence notable entre les environneraents de marais salants. Une analyse des distributions totales indique des différences notables entre les assemblages de foraminifères en fonction des environmements de surface. La schorre se caractérise par T. macrescens, T. comprimata et deux especes moins communes. La slikke se distingue par M. fusca. T. infJata et A. salsum. Les assemblages de bordure des chenaux de marées ressemblent à la slikke bien qu' A. salsum n'y soit plus preponderant. Bien que les bancs élevés du marais ne contiennent aucun spécimen vivant, on y rencontre un assemblage de spécimens morts typique de la schorre. Ces assemblages cosmopolites de foraminifères devraient pouvoir servir d'indicateurs valides lors de la reconstitution des paléomilieux de marais salants holocènes dans plusieurs régions. [Traduit par le journal]Téléchargements
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