Modelling tectonic, climatic and eustatic effects on orogen/foreland basin systems

In orogen/foreland basin systems, the development of basin stratigraphy is strongly influenced by the rates of several first order processes: orogen tectonics, surface processes, climate, isostasy and eustasy. A composite kinematic planform model has been developed to look for stratigraphic signatures that reflect the dominant influence of one of these basin controlling processes or the interaction among several processes.;The orogen/foreland basin model links component models of orogen tectonics, surface processes, orographically controlled precipitation, lithospheric flexure and eustasy in an internally consistent manner. Critical Coulomb wedge theory is used to create a doubly-vergent wedge-shaped orogen. The surface processes model couples diffusive and advective transports to erode, redistribute and deposit material. Fluvial transport is determined by both surface slope and discharge; the latter is controlled by precipitation and collection. Orographic rainfall is determined by topography, extraction efficiency and vapour flux. The isostasy model uses either an elastic or a thermally activated linear viscoelastic plate rheology to flexurally compensate for changes in orogenic, sedimentary and water loads. Eustasy is uniform change in model sea level.;Model results show, in planform and section, parallel and oblique continent/continent collision and orogen growth with pro- and retro-foreland basins. The effects of basin setting, along-strike changes in tectonics, prevailing 'wind' direction and feedback among processes on the rates of orogen growth and basin filling are discussed. Stratigraphy is shown as facies bounded by chronostratigraphic and erosional surfaces. Facies are described by characteristics of the model's depositional environments.;Synthetic stratigraphy is presented for orogen/foreland basin systems that have experienced changes in tectonics, climate or eustasy as either step or sinusoid functions. Stratigraphic assemblages show both the transient and steady state system response to these changes. Response times are estimated for tectonic and climatic forcing and used to illustrate how stratal geometry and facies distributions vary when the period of forcing is either approximately the same as or much greater than the response time.;Tectonic and climatic processes are shown to have similar effects on landform evolution and therefore the distribution of alluvial, coastal and marine facies. These similarities allow combinations of tectonic and climatic forcing to enhance or retard their mutual effects on stratigraphic development. Potentially distinctive effects of tectonic and climate processes are discussed. Eustasy is shown to have a subordinate effect to tectonic and climatic processes on alluvial plain development and a dominant effect on landform evolution proximal to the coast. Erosional surfaces associated with eustasy are shown to vary significantly with the rate of sea-level change.