Global glacial isostatic adjustment and coastal tectonics

Abstract A global and gravitationally self-consistent model of the process of glacial isostatic adjustment (GIA) has been developed that extremely well reconciles the vast majority of available records of Holocene relative sea-level history, not only from sites that were ice covered at last glacial maximum (LGM) but also from sites that are well removed from such locations. There do exist, however, data that have been construed to constitute a significant challenge to this theory, namely, the long records of relative sea-level history derived on the basis of U/Th-dated coral sequences from the Huon Peninsula of Papua New Guinea and from Tahiti in the central equatorial Pacific Ocean. Following a review of the theoretical model and a discussion of the extent to which it is able to successfully reconcile a very wide range of Holocene shoreline observations, the discussion focuses upon the interpretation of these very important and interesting records, which are subject to different levels and types of tectonic contamination. These analyses suggest that existing estimates of the levels of Holocene tectonic contamination at both locations may require revision. In this context, it is suggested that the global model of the GIA process is sufficiently accurate that the magnitude and form of local tectonic effects during the Holocene period might be sensibly estimated by simply subtracting the GIA prediction for a given site from the observed variation of relative sea level.