Contents


Preface

In this book, "Sedimentary Processes – Examples from Asia, Turkey, and Nigeria", the geological characteristics of different depositional environments have been singled out, particularly referring to deltas, beach systems, and coastal lacustrine environments. In this book, the other research topics are the riparian zone and the role of mangroves in controlling coastal sedimentation. The sedimentary processes represent one of the most important control factors influencing the facies distribution in a stratigraphic succession and are critical in coastal environments. In deltaic systems the vertical arrangement of depositional cycles is mainly controlled by the decrease of the gradients due to the progradation of the distributary channels. Exceptional events, including floods, storms, and earthquakes also influence the corresponding changes in the sedimentary patterns. The sedimentary processes are strictly related to the role of the sedimentary supply in controlling the stratigraphic architecture of the sedimentary sequences, depending on the availability of sediments, subsidence, and relative sea-level changes. In this framework, two situations may be distinguished, i.e. transgressive and regressive. In the transgressive situation, the subsidence and the sea-level rise are more important than the terrigenous supply and a sediment starvation occurs. Reworking, erosion, and diagenesis take place, coupled with an increase of chemically and biologically formed sediments. In the regressive situation, the subsidence and the sea level rise are less important than the terrigenous supply, resulting in progradation and increase of continental facies. Another important control factor acting on sedimentary processes is represented by the climate, due to the climate affecting the facies apart from temperature and rainfall, seasonal extremes, and sporadic fluctuations. Relative sea-level changes have been brought about by the sediment progradation, by the vertical movements, or by the tectonic tilting of the crustal blocks, by the changes in volume of the oceanic waters, or by the global tectonic changes, such as the variation in volume of the oceanic ridges. Delta models have individuated high constructive (tideinfluenced and wave-influenced) deltas and high destructive (lobate and elongate) deltas. Each delta type is distinguished from a characteristic morphology and facies pattern, which has been described including the vertical sequences, the facies associations, the facies distribution, and the geometry of the sandy bodies and reservoirs. The delta progradation produces a typical facies succession, consisting of prodelta facies, delta front, and delta plain facies. A coarsening upward succession of prodelta sediments to delta front sediments is overlain by a fining upward succession, composed of upper delta front sediments to delta plain sediments. The lacustrine deposits have a high potential of preservation and perhaps they represent excellent sedimentary archives in palaeo-climatic reconstructions. The sedimentary records of varves, annually laminated, provide high-resolution archives of palaeo-environmental conditions, so providing both chronological and geochemical information. Beach depositional systems and their changing morphology have been controlled by storm events, changing the coastal morphology, and triggering the formation of megacusp embayments. The impact of storms on the variation of the beach has been analyzed by combining the historical measurements of the beach profile surveys and the numerical modeling of storm-induced beach changes. The role of mangroves in controlling the coastal sedimentation is critical, since they
