Role of foraminifera in oceanographic events

Abstract

Foraminiferal studies on deep sea cores have revealed that they represent sediments from the Early Cretaceous to the Present, but the cores from the ridge areas are older in age, indicating sea floor spreading along transverse fracture zones; however, large scale drifting does not seem to have occurred since the Lower Miocene. The inter-relationship of palaeotemperature and isotopes of @u18@@O/@u16@@O, @u13@@C/@u12@@C with salinity, temperature and depth stratification of the ancient seas assists in the correlation with foraminifera as indicators. The planktonic assemblages also show effects of climatic control on water masses as seen in some deep sea cores. Species like @iOrbulina universa, Neogloboquadrina pachyderma, Globorotalia menardii neoflexuosa, Globigerinoides obliquus@@ and @iSpheroidinella dehiscens@@ play an important role in stratigraphic, climatic, evolutionary and several other oceanographic studies. Calcium carbonate compensation depth is one of the major factors that determine the dissolution, fragmentation, decalcification and even corrosion of foraminifera at 400-5000 m depth, thus creating an imbalance in the planktonic/benthonic ratio. This is one of the major problems in oceanography today. The diversity pattern of planktonics is a valuable tool in the reconstruction of latitudinal positions and circulation patterns of water masses of the past ages. Thus, species diversity is a consideration of the distribution of individuals among the species. But variability in foraminifera is a tendency to deviate from the normal form which may lead to erection of species into subspecies. Recent trends in taxonomic classification are based on the wall structure, surface ultrastructures and amino acid compositions of Recent and fossil foraminifera which reflect upon the genotypes of living and dead foraminifera. The importance of some of these parameters in the classification and interpretation of evolutionary patterns is generally accepted. Various kinds of pollutants change the normal ecophenotypic system that exists in a regime. This is continuously being altered now-a-days mostly by man. The alteration, modification and tolerance or destruction of foraminifera in the altered environment are being evaluated. Such an assessment becomes valuable in the understanding of similar events in the geological past