No abstract

Reconstructing meandering paleo-channels is attracting global research attention. We implemented a novel method by comprehensively integrating migration models and sedimentary structures. Firstly, the migration architectures of the corresponding characteristics in planform and cross-sectional models were summarised as expansion, translation, expansion and translation, expansion and downstream rotation, constriction and downstream rotation, and expansion and countercurrent rotation models. Secondly, full continuous core data from 270 dense drilling wells were collected from the Daqing Oil Field in the Songliao Basin, China, providing information on rock textures, sedimentary cycles, and boundary information for the two layers being studied. Through a comprehensive analysis of dense drill cores and logging data, the abandoned channels and the initial and final channel centrelines were identified. Consequently, four profiles, including one longitudinal and three transverse sections, were constructed to reveal the cross-sectional structures and planform migration architecture. Profile interpretation revealed the evolution from the initial channel centreline to the final centreline. Using a method of rational interpolation, we were able to reconstruct the migration architecture of the meandering channels. The results showed that the average ancient bankfull width (W c ) was approximately 100 m, a single meandering belt was 800 m, the radius of the curvature was 250 m, the length of the channel bend was 700 m, the average meander wavelength was 1300 m, the sinuosity was 3.0, and the annual average discharge rate was 450 m 3 /s. Furthermore, we compared the results from empirical equations, which verified that our reconstruction is both feasible and potentially widely applicable.

The meandering process has always been the topic through years and still remains a lot of unsolved mysteries. One of the most important focus is the migration architectures and models that the meandering channels follow. This article chooses the Nowitna River as the study object of the typical meandering river with high migratory processes. Though the high-resolution historical satellite images by the techniques of Google Earth and ACME Mapper, 50 meanders in the river is studied and 6 of which are chosen for meticulous characterization. During the process, the planform structure of meandering channel is re-examined and 29 kinds of architecture elements are systematically established. More importantly, in order to make a fine quantitative characterization of the channel structure of meandering river, 5 kinds of characterization parameters are proposed, extraordinarily, the parameters of the difference of along-current deflection angle, a difference of counter-current deflection angle, and expansion coefficient, these three are firstly brought forward and applied introduction. In addition, the conception of sinuosity index and curvature are also different from the original definition. Though these architectures elements the meandering process and migration structure of the Nowitna River is demonstrated. 6 kinds of planform migration structures is revealed with the quantitative characterization of characterization parameters and 9 species of meandering channel migration patterns are concluded and discussed.

The Peruvian Amazon is known for harboring the greatest biodiversity on the planet, with a world record for biodiversity per unit area. Previous studies suggested that the high ecological value depends on correlations between ecosystem functionality and seasonal inundation control vegetation patches. However, the knowledge on how river morphodynamics and its complex erosion-depositional processes influence the aquatic mosaic and fishing activity in the region is still incipient. This study examines the hydrogeomorphology of the Peruvian tropical wetland of Pacaya Samiria, located in Western Amazonia, and its role in the distribution of aquatic habitats. By using remote sensing techniques, the hydrogeomorphological connectivity that bounds the Pacaya Samiria National Reserve is characterized by ancient to modern river processes. Additionally, river signatures developed by the Ucayali, Marañon, Huallaga, Pacaya, and Samiria Rivers overlap with fish extraction and dominant vegetation to describe how geomorphology is associated with the spatial distribution of fishing zones. Results indicated that paleochannels regulate wetland drainage within the Ucamara Depression, supporting stational water stagnation, vegetation cover, and formation of carbon rich detritus, relevant aspects to understand fish traits. Moreover, the Ucayali River dominates river dynamics in the Pacaya Samiria wetland, thus playing a pivotal role in shaping the complexity of streams and lakes. Furthermore, underfit-scavenger meandering rivers are observed in areas where paleochannels from large rivers are found. A geomorphological characterization of drainage patterns in freshwater environments, such as Amazonian wetlands, is crucial to develop sound management strategies. This methodological approach is expected to support decision-making in conservation actions in Amazonian environments based on understanding wetland connectivity and hydrogeomorphological behavior and their influence on commercial fisheries.

Current research on unconformity belt mainly concentrates on the analysis and description of unconformity surface and contact relationship with overlying and underlying strata. Too much emphasis on the division of the "three-layer structure" of unconformity yields obvious disadvantages, i.e., that studies are not only insufficient in the authenticity of architecture but also in the characterization of the combination of the two-and three-dimensional perspectives. Thus, the analysis of genetic mechanism and meticulous depiction is ignored. Accordingly, by making full use of the outcrops and combining previous research findings, this study aims to provide a detailed description and analysis for the unconformity belt structure, and points out the non-uniqueness of the three-layer structure of the unconformity belt. Based on the theory of depositional process and according to the method and principle of the "point-line-surface", a comprehensive characterization method combined with a kind of "two-dimensional structure" and "three-dimensional structure" is proposed. A two-dimensional structure is a kind of surface structure, while the three-dimensional structure is a kind of body structure, Moreover, this study discusses the recognition significance of the visual unconformity line and visual unconformity surface with respect to the unconformity belt structure. According to the spatial allocation and geological significance of the unconformity belt, two types of models are established in order to depict the structure of unconformity belt better. Combined with the structural elements of the unconformity belt and complied from the viewpoint of the sedimentary environment, the formation mechanism of two-and three-dimensional structures is summarized.