Analogs in the study of fluvial successions: Conceptual framework and examples from the Chubut Group (Cretaceous) of Argentina

Abstract

This review presents the theoretical framework of the use of analogies in science, and within the hydrocarbon industry in particular, and develops several approaches employed to study the continental successions of the Cretaceous Chubut Group of the Golfo San Jorge basin (Argentina). The Cretaceous Chubut Group was preserved in an endorheic basin that changed its basin configuration, boundaries, and alluvial organization through its deposition. The study of fossil analogs is presented through the compilation of geometrical data of fluvial channel deposits that belong to the Matasiete (Aptian), Castillo (Albian), and Bajo Barreal (Cenomanian-Turonian?) formations, currently exposed along the San Bernardo Fold Belt. The database reflects the occurrence of (several) multichannel drainage catchments with ribbon to narrow sheet channel geometries mainly in a high-accommodation setting, whose temporal and spatial variations in fluvial processes and alluvial styles were regulated by its (paleo)geomorphological position, overimposed to climatic and tectonic signals. In addition, the finding of current analogs of productive channel belts within the Mina del Carmen Formation (Albian) has been explored through seismic geomorphology, empirical relations derived from current rivers, and global databases of river discharge and area of the drainage catchments.Current analogs of endorheic basins in a seasonal climate occur in the south-central of Africa (Okavango Macrobasin) and central-northwest of Africa (Lake Chad basin). Both endorheic basins contain several drainage catchments of variable orientation with multiple source areas, variable development of fluvial processes (ephemeral, strongly seasonal, perennial) regulated by the overall patterns of precipitation and temperature distribution within the drainage catchments, and multiple base levels (lacustrine, ephemeral pans) in hydrological basins changing between fully integrated, partially-connected or disintegrate according to the water availability. Both analogs record significant changes in the size of the lakes and ephemeral pans through their evolution, regulated by the overall re-organization of the drainage catchments by river capture and climatic cycles; comparable features have not been recognized within the Chubut Group in the subsurface of the Golfo San Jorge basin until now.