Can the confinement index (calculated on the basis of foraminiferal populations) be used in the study of coastal evolution during the quaternary?

Abstract

Abstract One of the major present preoccupations of ecologists is to foresee the effect of the predicted sea level change on the coastline, and therefore on the biosphere. Prospective studies first require a thorough knowledge of present conditions and of past evolution. Paralic environments are very sensitive to coastline variations, and provide one of the most sensitive tools for studying sea level change. One of their main characteristics is the degree of marine influence, named confinement, that depends on climatic conditions and on the coastline morphology and evolution. However, these environments are under the influence of complex interacting parameters, and their study requires a set of complementary tools. A confinement index ( Ic ), calculated on the basis of the main species of foraminifers, has been worked out in the paralic environments of west Africa. It provides a numerical value that can be calculated rapidly, and gives an immediate objective indication of slight changes in the environment, with a tendency toward more restricted ( Ic increases) or less restricted ( Ic decreases) conditions. This tendency might be in relation with sea level change. Thus, Ic is proposed as a preliminary tool for quantifying changes in the paralic ecosystems. Used together with a set of complementary indicators (sedimentology, geochemistry, and so on) it can be used for the detection of sea level change.