Paleohydrology in greenhouse and icehouse stages

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Methodologies of quantitative characterization of morphology and paleohydrology of ancient fluvial systems were investigated on the basis of published empirical relationships among several variables, which represent hydraulic features of modern fluvial systems. Architectural analyses of ancient fluvial successions were used for the better understand of spatial and temporal variations in morphology and paleohydraulic features of ancient fluvial system. Six-hold hierarchy of bounding surfaces and their depositional units were identified from outcrop analysis of ancient fluvial successions. The most laterally continuous bounding surface defines a channel belt and the least laterally continuous bounding surface is a reactivation surface within a bar deposit. On the basis of stacking patterns and lithofacies features of component channel deposits, fluvial styles in an overall transgressive succession does not exhibit any distinct change compared with the standard fluvial sequence-stratigraphic model. In terms of comparison of fluvial systems developed during greenhouse and icehouse stages, distinct variations in morphology, sinuosity and paleohydrology were not necessarily evident and fluvial systems are interpreted not to have intimately responded to changed in paleoclimates. Lower Cretaceous fluvial systems developed in Japan and northeastern China were investigated in terms of spatial variations in fluvial styles and paleohydrology along the eastern margin of the Asian continent. Both areas are characterized by fluvial systems largely similar in paleohydrology, such as average annual discharge, channel width, sinuosity, and channel belt width. Overall, paleodischarge, and channel-belt width decreased with the increase in sinuosity of fluvial channels in response to decline of topographic surfaces in later stage of in filling of sedimentary basins.