Transgressions and regressions: a model for the influence of tectonic subsidence, deposition and eustasy, with application to Quaternary and Carboniferous examples

Abstract

The position of a coastline in time and space is determined by (1) the vertical displacement and/or tilting of the depositional surface, (2) the rate of sediment accumulation or erosion across that surface, and (3) variation of sea-level. All three rates of change may vary through time. We present computer simulations of coastline movements that illustrate the interaction of the above variables, with (1) and (2) held at various defined levels whilst (3) is varied according to the late Quaternary glacio-eustatic sea-level curve. The Corinth Canal section in central Greece exposes uplifted late Quaternary coastal transgressive cycles, each of which may be related to a radiometrically dated, c. 100 ka duration, cycle of sea-level change. Observed stratigraphic sequence geometries are predicted by forward modelling based on the known glacio-eustatic history over the last 430 ka. Milankovitch orbital parameters are calculated for the Carboniferous period. The obliquity and precession parameters are found to have been significantly shorter than at present. A simulation is presented of the effects of sea-level changes across low gradient, fluvio-deltaic environments such as existed in northern England and other parts of the Laurentian continental margin during Upper Carboniferous time.