This monograph was begun with two objectives in mind. The first was to provide a review of research involving the application of neodymium isotopic measurements to pro blems in earth science. In the process of organizing to do this, I realized that the research in this field had produced a need for an updated review of the underlying paradigms. This need had arisen because of the special properties of the samarium-neodymium isotopic system, and because the research had transgressed the traditional boundaries be tween the subfields of earth science. Without such a review, the significance of the results seemed likely to remain un necessarily obscure to interested scientists from related disciplines. Consequently, the second objective became the provision of a theoretical framework for the application of neodymium isotopic studies. Much of what this contains is not new, but it is drawn together here for the first time. At the time the writing was initiated, the literature of the field was still relatively limited. Over the past 5 years it has grown enormously. Considering the rate at which the writing progressed, it became clear that this could not be a fully up-to-date review and still reach completion. The selection of material for the review sections is biased toward earlier studies. Part I presents most of the background information."

Studies of Sr isotopic composition of thousands of samples of marine sediments and fossils have yielded a curve of 87Sr/86Sr versus age for seawater Sr that extends back to 1 billion years. The ratio has fluctuated with large amplitude during this time period, and because the ratio is always uniform in the oceans globally at any one time, it is useful as a stratigraphic correlation and age-dating tool. The ratio also appears to reflect major tectonic and climatic events in Earth history and hence provides clues as to the causes, timing, and consequences of those events. The seawater 87Sr/86Sr ratio is generally high during periods marked by continent-continent collisions, and lower when continental topography is subdued, and seafloor generation rates are high. There is evidence that major shifts in the seawater ratio can be ascribed to specific orogenic events and correlate with large shifts in global climate.