From river to rock record. The preservation of fluvial sediments and their subsequent interpretation / От реки до литофикации. Сохранение речных отложений и их последующая интерпретация

It is our impression that, over the last couple of decades, fluvial geomorphology and fluvial sedimentary geology have been developing in parallel, rather than in conjunction as might be expected. Though we tell our students that these are interdependent disciplines, perusal of the literature uggests there has been a failure of each domain to inform and recognize the needs of the other. Many facts have been collected, from both modem and ancient examples, yet our widerstanding of the sedimentary record of 1ivers eems not to have advanced significantly. It is still a struggle to map the architecture ob erved in the preserved rock record to the genetic components recorded from active modern rivers. Determination of the lateral extent and va1iation of lithofacies remains exceedingly problematic, especially in the subsurface.
We contend there are two fundamental causes of this dichotomy and the problems it has brought about. Firstly, whilst there is now a good understanding of the instantaneous processes of sediment transport and bed form development, there remains a poor appreciation of the spatial distribution and longer term temporal evolution of bed forms, and the way these bedforms interact with the channel banks and floodplain. Secondly, current sedimentary models fail to take into account the many erosional and depositional modifications that occur as the sedimentary architecture develops, and imply that the observed planform of modern 1ivers is preserved largely intact. In reality, the rock record is a mosaic of remnants from the original rivers, some small, some large, but few of them with the mutual arrangement they had at the time of deposition.
Of chief concern is the need to remember that interpretation of the rock record is based on what is known about modern settingstypically, we see only what we expect to see and we overlook features with which we are not familiar. In the light of present-day geomorphological knowledge, published fluvial sedimentary facies models, particularly the ones in textbooks, appear over-simplistic but they are still in regular use. For example, there is little recognition in these models of the role of soil and vegetation in modifying river behavior, and few of them take into account the complex interaction between autogenic and allogenic controls of river behavior and sedirnentology <...>