The use of Jadammina macrescens (Brady) and Balticammina pseudomacrescens Brönnimann, Lutze and Whittaker (Protozoa: Foraminiferida) as sea-level indicators

Abstract

In studies of foraminiferal distributions in saltmarshes in New England and Atlantic Canada, Balticammina pseudomacrescens and Jadammina macrescens have formerly been grouped as Trochammina macrescens. This study recognises them as distinct species and shows that they have significantly different distributions on the surface of saltmarshes in Maine. Here, relative abundances of J. macrescens correlate with tidal elevation ( r 2=0.55, p=0.00), whereas those of B. pseudomacrescens do not ( r 2=0.03, p=0.34). Therefore, J. macrescens is a better sea-level indicator in Maine marshes than B. pseudomacrescens. In Menunketesuck River marsh, Connecticut, a clear vertical zonation of saltmarsh foraminifera is absent, which hinders interpretation of fossil data. This study shows that, in Maine, separating B. pseudomacrescens and J. macrescens in counts of fossil data facilitates the detection of transgressional and regressional events in the biostratigraphical record and, hence, the reconstruction of local sea-level histories. Regional variability between northern and southern New England saltmarshes necessitates the establishment of local reference sets of modern analogue data to aid palaeoecological interpretations.