Significance and Origin of Big Rivers

Ancient big river systems can be identified by a combination of facies mapping, paleocurrent study, analysis of unconformities, and the careful reconstruction of the tectonic history of a region. Ancient or modern, the location of big river systems on cratons largely follows structural lows such as deep-seated rifts, aulacogens, and geofracture systems; on a continent-wide scale many big rivers debouch on trailing continental margins and into marginal seas, where they tend to be localized by deep geofracture systems intersecting the coastline. Big river systems have their greatest longevity on cratons where some have persisted as long as one sixteenth of earth history. A major factor in any river system is the marine history of its drainage basin, a history that in turn is dependent upon the region's tectonic history.