Tectonics and seismic sequence stratigraphy: an introduction

Abstract

The application of sequence stratigraphic models to seismic data is restricted by the vertical and spatial resolution of the data. The fundamental stratigraphic unit of the sequence stratigraphic technique is the seismically distinguished 'sequence' although the concept of tectonically related 'mega- sequences' is useful. Basin stratigraphy is controlled to varying degrees by eustatic sea-level change (or base level in lakes), subsidence/uplift and sediment supply. Three main basin types, rift-, wrench-, and thrust-related basins, have distinctive gross stratigraphic architectures. Localized, tectonically controlled subsidence and uplift has a significant control on three-dimensional stratigraphic patterns. Stratigraphy is the partial record of basin evolution resulting from the interaction of a number of factors such as regional and local subsidence/uplift, sediment supply, eustacy and climatic change (Fig. 1). Basins that have a marine connection will show significant stratigraphic variations, especially in coastal deposits, that result from eustatic sea-level fluctuations. Other key factors will include the availability of sediment and the role of tectonically induced subsidence and uplift. Alternatively, land-locked or intermontane basins whose fluvial systems drain ultimately into a lake will preserve a stratigraphy dominated by local relative uplift and subsidence (local tectonics), by climatic controls and the rate of sediment supply. Tectonic activity is an important factor in controlling stratigraphy in the majority of sedimentary basins. Tectonism generates accommodation space in basins, it alters base levels and it controls source areas. When mountain ranges are generated, tectonics may even influence local climatic patterns. It is difficult to separate the relative importance of tectonics versus other factors in controlling stratigraphic architecture in basins. In this introduction, basins formed on continental lithosphere and their associated stratigraphies will be considered.