TWO RARE PUSTULOSE/SPINOSE MORPHOTYPES OF BENTHIC FORAMINIFERA FROM EASTERN ROSS SEA, ANTARCTICA

摘要

Habitats proximal to grounded ice and below ice shelves are rarely studied for microfossils. A recently described, well-resolved deglaciation record from the Whales Deep Basin of the eastern Ross Sea provided an opportunity to study sub-fossil foraminifera in such settings. Among other foraminiferal taxa, two forms with pustulose/spinose ornamentation were especially important as they were restricted to habitats associated with proximity to the calving front or presence of an ice-shelf. Based on gradation from strongly pustulose/spinose to typical morphologies and existing molecular data, these rarely reported forms are considered to be morphotypes of Globocassidulina biora (Crespin, 1960) and Trifarina earlandi (Parr, 1950). They seemed to flourish in polynya areas near grounding-line and in sub-ice-shelf environments with bottom currents. Their unusual morphologies may be a response to limited food resources. These foraminifera deserve special attention because they appear to be restricted to extreme Antarctic environments and hence are potentially very important for paleoenvironmental reconstructions.