Chapter 3 - Stable Isotopes: Tools for Understanding Past Climatic Conditions and Their Applications in Chemostratigraphy

Abstract

The present climatic deterioration including the much debated anthropogenic acceleration to the global warming phenomenon has drawn the attention of scientific community, policy makers as well as the general public to the problem of climate change. Chemostratigraphic techniques have proven to be very useful to understand the past climate of the earth that has been changing naturally on timescales ranging from decades to millions of years. Therefore, it is important to filter out the natural signal to correctly gauge the effects induced by humans. This is where the science of paleoclimatology becomes very important. It helps us to understand the pattern of evolution of the earth's climate system, its rhythm, and pulse using various natural archives such as marine and lacustrine sediments, speleothems, ice cores, corals, trees, etc., that hold the clue to the past climate variability. Several proxies are studied from such natural archives to reconstruct the past climatic changes. Out of these, the stable isotopes are one of the most useful and widely employed. In this present study, we explain the methodology behind the application of the stable isotopes as a proxy to reconstruct past climatic changes. We present here a few examples of the stable isotopes of the most widely used elements viz oxygen, carbon, and nitrogen from the marine realm and their systematics. The use of chemostratigraphic techniques like application of oxygen isotopes in stratigraphy, temperature, salinity, and ice-volume reconstruction; Cenozoic oxygen and carbon isotope curves; the limitations in the form of vital effect and diagenesis in the case of foraminifera; use of nitrogen and carbon isotopes as productivity and provenance indicator, respectively, are presented in this paper.