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Stratigraphy and Sedimentation
Published in Supriya Sengupta, Introduction to Sedimentology, 2017
‘A gradational transition from one facies to another implies that the two facies represent environments that were once adjacent laterally’ is a concise expression of what was formulated by Johannes Walther in his Law of Correlation of Facies, usually referred to as Walther’s Law of Succession of Facies (Middleton 1973). Continuous subsidence of the area of sedimentation is an essential prerequisite to such a preservation. The vertical stratigraphic record produced by laterally migrating deposits of a meandering stream channel may be cited here as an illustration of Walther’s Law. At any point of time lenses of channel sand deposited by a meandering stream interfinger with silt and clay laid down in the interchannel flood basin. Continuous subsidence of this basin of deposition produces a succession of multistorey sand bodies, each of which grades laterally into the adjacent flood-basin deposits. The result is a vertical sequence of repetitive sedimentary cycles (‘cyclothems’) of channel sands overlying flood-basin silts and clays. An example of detrital sand lenses preserved due to subsidence of a hypothetical delta complex is given in Fig. 8.6.
Ensemble-based machine learning application for lithofacies classification in a pre-salt carbonate reservoir, Santos Basin, Brazil
Published in Petroleum Science and Technology, 2022
Amir Abbas Babasafari, Alexandre Campane Vidal, Guilherme Furlan Chinelatto, Jean Rangel, Mateus Basso
According to Wright and Barnett (2015), the Barra Velha Formation deposits can be represented by a cyclothem of three facies, beginning with laminated mudstones and developing into spherulites and shrubstones. Reworked facies (grainstones and rudstones) are also common and are associated with the erosion and transport of previously described facies. They can be found throughout the cyclothem. The thickness (centimeters to meters), staking pattern, and facies frequency of the cyclothems may vary depending on paleoenvironmental conditions such as lake level fluctuation and climate, as well as structural position, which varies from low to high due to the presence of faults (Gomes et al. 2020; Ferreira et al. 2021; Minzoni et al. 2021).