Time/Depth Distribution of Late Quaternary Uvigerina peregrina, North American Continental Margin: Morphological and Paleoceanographic Implications

Abstract

Uvigerina peregrina from the continental slope of the eastern United States exhibits morphological and distributional evidence for distinct populations at water depths from about 700 to 5000 m since 25, 000 years before present (YBP). During the glacial maximum (18, 000 YBP) this species occupied water depths from 2400 to 4350 meters. Beginning 16, 000 YBP, U. peregrina diverged into two populations. The main population rangedfrom 3000 to 4350 m water depth, contracted during late glacial and early Holocene time, and finally vanished from a depth of 3600 m at 8000 YBP. An isolated portion of the glacial age population survived between 2100 and 2300 m and connected the late glacial and late Holocene populations of U. peregrina. The modern population of U. peregrina first appeared about 4000 YBP and is confined to water depths of 900 to 3000 m with its acme between 1600 and 2500 meters. Fourier shape analysis shows that the modern and glacial age populations of U. peregrina are morphologically distinct. The observed morphological and distributional differences indicate that the modern and glacial-age specimens represent discrete populations rather than an upslope migration of a single population. Water masses of the western North Atlantic have significant control on the spatial and temporal distribution of this species. Paleobathymetric and paleoceanographic reconstructions using U. peregrina should consider the population affinity, especially in the western North Atlantic.