Dinoflagellate “communities”; from the lower Eocene Nanjemoy formation of Maryland, U.S.A.

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Abstract
Six distinctive stratigraphically sequential dinoflagellate cyst communities in the Lower Eocene Nanjemoy Formation (Woodstock Member) of Maryland, possibly relate to fluctuations in local environmental conditions. Individual species most commonly are not stratigraphically restricted to a single community; however, their relative abundances (in particular, of the dominant species), as illustrated by rank abundance analysis, are unique to each of the six communities. Major changes in species composition and relative abundances are, for the most part, correlative with pronounced changes in the number of species per sample for the sections. Cluster analyses of the ten most abundant species in each sample, which comprise from 76 to 100 percent of all the dinoflagellates in each sample, also tend to demonstrate the existence of the same six diagnostic cyst communities.