Backwash-and-swash-oriented current crescents: indicators of beach slope, current direction and environment
TL;DR: In this paper, backwash-and-swash-oriented current crescents are reported, with their detailed morphology and formation mechanism from the siliciclastic fine sandy beaches of Sagar Island and Lower Long Sand, two tidal islands of the Ganga estuary, northeast India.
About: This article is published in Sedimentary Geology.The article was published on 1993-04-01. It has received 15 citations till now. The article focuses on the topics: Swash.
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01 Jan 2016
TL;DR: In this article, a comprehensive account of congener profiles of polycyclic aromatic hydrocarbons (PAHs) in intertidal bivalve mollusks (Meretrix meretrix, Macoma birmanica, and Sanguilonaria (Soletellina) acuminata) is presented.
Abstract: The chapter highlights the comprehensive account of congener profiles of polycyclic aromatic hydrocarbons (PAHs) in intertidal bivalve mollusks (Meretrix meretrix, Macoma birmanica, and Sanguilonaria (Soletellina) acuminata) of Indian Sundarban mangrove wetland. The main aim of this work was to use the bivalves as bioindicators of the contamination of the 16 USEPA PAH. The PAH profile in bivalves is largely dominated by a petrogenic fingerprint, with over-imposition of pyrolytic PAH sources, as evidenced by diagnostic molecular ratios. Bioaccumulation factors (BAF) of individual compounds from the sediments were calculated, and it reveals overall higher values in the visceral mass of the bivalves. S acuminata showed significantly higher levels of PAHs, especially the high-molecular-weight (HMW) PAHs, compared to the other two species as a sensitive indicator of trace organic stress in future monitoring programmes.
1 citations
TL;DR: In this article, the authors measured Froude numbers during the generation of rhomboid rills and found that the trend of the rhombus angles versus Foude numbers was similar to that in the case of ripples.
Abstract: Rhomboid rills, small sand topographies often observed in the swash zone of beach slopes, are apparently similar but different from rhomboid ripples that have been relatively well researched. Rhomboid rills are composed of thin grooves, while rhomboid ripples are of the tilelike geometry. A recent study showed a difference in the dependence of rhombus angle on the slope gradient between rhomboid rills and rhomboid ripples. In this study, we measured Froude numbers during the generation of rhomboid rills and found that the trend of rhombus angles versus Froude numbers was similar to that in the case of rhomboid ripples. We discuss similarities and dissimilarities between rhomboid rills and rhomboid ripples, showing an open problem.
1 citations
TL;DR: The coastal geomorphic features of West Bengal consist of beaches, islands, estuaries, river mouth bars or tidal islands, tidal rivers, and creeks, coastal dunes, swash platforms, etc as discussed by the authors .
Abstract: Coastal hydrodynamics and the process of sediment transport play a significant role in making various geomorphological features. Coastal geomorphic features of West Bengal consist of beaches, islands, estuaries, river mouth bars or tidal islands, tidal rivers, and creeks, coastal dunes, swash platforms, etc. Generally, the deltaic coastline of West Bengal is showing indented estuarine features because of the outfall of some important rivers and creeks in the Bay of Bengal, and for the longitudinal bars due to cliff erosion of the coastal sand dunes. The coastal area is dominated by physical phenomena like the tidal regime and tidal fluctuation that accelerate the geomorphic evolution of the coast, and for this reason, the coasts of West Bengal may be designated as estuarine delta coasts. Beaches scattered along the coastal region, in the majority, belong to the dissipative dynamic state having gentle rhythmic beach profiles. Each coastal geomorphic zone has a characteristic sand body geometry identified by certain parameters like grain size, bedforms, dimensions of sand bodies, stratifications, and facies sequences. The extreme southern portion of West Bengal in the lap of the Bay of Bengal is geomorphologically a tropical deltaic low-lying coastal region.
01 Jan 2015
TL;DR: Sunderbans forms a part of the world's largest fluvio-marine Ganges- Brahmaputra deltaic plain at the confluence of the Bay of Bengal with the largest block of halophytic mangrove forest.
Abstract: Sunderbans forms a part of the world’s largest fluvio-marine Ganges – Brahmaputra deltaic plain at the confluence of the Bay of Bengal with the largest block of halophytic mangrove forest. It has passed through a dynamic and complex physiographical and geomorphological history. Prograding in phases towards Bay of Bengal during Plio-Pleistocene inter-glacial period, it has left behind numerous distinctive landforms and islands of various shapes and sizes. The intricate network of rivers, tidal creeks and inlets with dynamic flow pattern accelerates the process of erosion and accretion and make the geomorphic set-up of the area a complex one. The important morphotypes of Sunderbans are beaches and inlets, creeks and estuaries, mudflats, coastal dunes, sand flats and mangrove swamps.
References
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01 Jan 1984
TL;DR: In this article, a model of transverse bedforms in Unidirectional Flows is presented, along with cross-stratification patterns of Ripples and Dunes in Changing Flows.
Abstract: 1. Environmental Fluid Dynamics. 2. Entrainment and Transport of Sedimentary Particles. 3. Particle Motions at Low Concentrations: Grading in Pyroclastic-Fall Deposits. 4. Packing of Sedimentary Particles. 5. Orientation of Particles During Sedimentation: Shape-Fabrics. 6. Transition to Turbulence and the Fine Structure of Steady Turbulent Boundary Layers: Parting Lineation and Related Structures. 7. Models of Transverse Bedforms in Unidirectional Flows. 8. Empirical Character of Ripples and Dunes Formed By Unidirectional Flows. 9. Climbing Ripples and Dunes and Their Cross-Stratification Patterns. 10. Bedforms in Supercritical and Related Flows: Transverse Ribs, Rhomboid Features, and Antidunes. 11. Transverse Bedforms in Multidirectional Flows: Wave-Related Ripples Marks, Sand Waves, and Equant Dunes. 12. Ripples and Dunes in Changing Flows.
1,309 citations
TL;DR: In this paper, the authors apply experimental physics to the study of rocks and apply it to six different kinds of physical questions, some of which have been sufficiently studied, but others require experiments which would be very difficult to carry out, and all that can now do is to attempt to deduce plausible results from what is known.
Abstract: 1. Introduction. In the case of nearly all branches of science a great advance was made when accurate quantitative methods were used instead of merely qualitative. One great advantage of this is that it necessitates more accurate thought, points out what remains to be learned, and sometimes small residual quantities, which otherwise would escape attention, indicate important facts. Since it applies to nearly all branches of geology, it is necessarily a wide subject, but so connected together that it seems undesirable to divide it. My object is to apply experimental physics to the study of rocks. At least six different kinds of physical questions are involved, some of which have been sufficiently studied, but others require experiments which would be very difficult to carry out, and all that I can now do is to endeavour to deduce plausible results from what is known. In doing this, it may be necessary to assume cases sufficiently simple for calculation, which may but imperfectly correspond to natural conditions, so that the results may be only approximately correct. In some cases, facts seem to show that there are important properties connected with subsiding material which cannot be explained in a satisfactory manner. Notwithstanding this, it appears desirable to do the best that I can with the material at my disposal, hoping to lead others to do what I intended to do, and correct such errors as are now unavoidable. In order to clear the way for subsequent detail, I describe a few general facts.
210 citations
TL;DR: In this paper, a more flexible and comprehensive approach to palaeocurrent analysis was proposed, in which the geometry of bed forms is two-dimensional or three-dimensional, depending on the interaction between a fluid flow and the sediment transported over or close to the bed.
Abstract: SUMMARY
Bed forms arise by interaction between a fluid flow and the sediment transported over or close to the bed. The geometry of bed forms is two-dimensional or three-dimensional. Two-dimensional bed forms generate two-dimensional internal sedimentary structures and are adjusted to two-dimensional flow-vector fields. Three-dimensional bed forms generate three-dimensional internal sedimentary structures and are adjusted to three-dimensional flow-vector fields. Many shallow-water flow systems observable today are each characterised by flow-vector fields of unequal rank, and hence are hierarchically structured. Hierarchies of bed forms and internal structures which parallel the hierarchies of flow-vector fields can also be established in the case of these flow systems. A single type of bed form or internal structure from an hierarchically structured flow system cannot specify that system fully with regard to either its directional or flow-dynamic characteristics. An approach to palaeocurrent analysis that is more flexible and comprehensive than previously attempted may therefore be desirable.
118 citations
TL;DR: In this article, the authors compared sediments and bed forms from three braided outwash plains and one steep non-braided mountain stream in the Rocky Mountains of Alberta to those exposed in a paleo-out...
Abstract: Sediments and bed forms from three braided outwash plains and one steep non-braided mountain stream in the Rocky Mountains of Alberta are compared to sediments and structures exposed in a paleo-out...
117 citations
87 citations