Submarine slope destabilization and gully formation by water sapping: Physical simulation of an underestimated trigger of subaqueous sediment gravity flows

Sedimentology ◽  
2021 ◽  
Author(s):  
Carolina Holz Boffo ◽  
Daniel Bayer Da Silva ◽  
Rafael Manica ◽  
Ana Luiza De Oliveira Borges ◽  
Adriano R. Viana
Keyword(s):  
Physical Simulation ◽  
Submarine Slope ◽  
Sediment Gravity Flows ◽  
Gravity Flows

scholarly journals A new empirical viscosity model for composed suspensions used in experiments of sediment gravity flows

RBRH ◽  
2021 ◽  
Vol 26 ◽  
Author(s):  
Camila Castro ◽  
Ana Luiza de Oliveira Borges ◽  
Rafael Manica
Keyword(s):  
Physical Simulation ◽  
Relative Viscosity ◽  
Packing Fraction ◽  
Turbidity Currents ◽  
Single Model ◽  
Gravitational Flow ◽  
Sediment Gravity Flows ◽  
Gravity Flows ◽  
Clay Percentage ◽  
Maximum Packing Fraction

ABSTRACT Sediment gravity flows are natural flows composed by water and sediment in which the gravitational flow acts on the sediment. The distinct physical properties of the cohesive (clay) and non-cohesive (sand) sediment, and the interaction between these particles alter the ability of the flow to resist to the movement (rheology) along time and space, represented by the viscosity of a mixture suspension. Hence, we propose to study the rheological properties of those mixtures and calculate their relative viscosity when used in the physical simulation of turbidity currents. Rheological tests were performed with various mixtures composed by water, clay and/or coal. Two equations are proposed to estimate the relative viscosity as a function of volume concentration of each sediment, the maximum packing fraction and the percentage of clay present in the mixture. The results also show an error close to 20% comparing similar models from the literature, which are satisfactory. The results also demonstrate that caution should be exercised when generalizing the use of a single model to predict the relative viscosity of suspensions. The influence of density (ρ), grain shape, clay percentage (Cclay), volumetric concentration (ϕ) and maximum packaging fraction (ϕmax) should be considered in the formulation of the equations.

Benthic foraminiferal zonation in deep-water carbonate platform margin environments, northern Little Bahama Bank

1988 ◽  
Vol 62 (01) ◽  
pp. 1-8 ◽  
Author(s):  
Ronald E. Martin
Keyword(s):  
Deep Water ◽  
Benthic Foraminifera ◽  
Carbonate Platform ◽  
Sedimentary Facies ◽  
Depositional Environments ◽  
Near Surface ◽  
Sediment Gravity Flows ◽  
Gravity Flows ◽  
Platform Margin ◽  
Water Carbonate

The utility of benthic foraminifera in bathymetric interpretation of clastic depositional environments is well established. In contrast, bathymetric distribution of benthic foraminifera in deep-water carbonate environments has been largely neglected. Approximately 260 species and morphotypes of benthic foraminifera were identified from 12 piston core tops and grab samples collected along two traverses 25 km apart across the northern windward margin of Little Bahama Bank at depths of 275-1,135 m. Certain species and operational taxonomic groups of benthic foraminifera correspond to major near-surface sedimentary facies of the windward margin of Little Bahama Bank and serve as reliable depth indicators. Globocassidulina subglobosa, Cibicides rugosus, and Cibicides wuellerstorfi are all reliable depth indicators, being most abundant at depths >1,000 m, and are found in lower slope periplatform aprons, which are primarily comprised of sediment gravity flows. Reef-dwelling peneroplids and soritids (suborder Miliolina) and rotaliines (suborder Rotaliina) are most abundant at depths <300 m, reflecting downslope bottom transport in proximity to bank-margin reefs. Small miliolines, rosalinids, and discorbids are abundant in periplatform ooze at depths <300 m and are winnowed from the carbonate platform. Increased variation in assemblage diversity below 900 m reflects mixing of shallow- and deep-water species by sediment gravity flows.

scholarly journals Role of Upper-Flow-Regime Bedforms Emplaced by Sediment Gravity Flows in the Evolution of Deltas

2019 ◽  
Vol 7 (1) ◽  
pp. 5 ◽  
Author(s):  
Svetlana Kostic ◽  
Daniele Casalbore ◽  
Francesco Chiocci ◽  
Jörg Lang ◽  
Jutta Winsemann
Keyword(s):  
Numerical Analysis ◽  
High Resolution ◽  
Flow Regime ◽  
Case Studies ◽  
Seismic Data ◽  
Lake Level ◽  
Sediment Gravity Flows ◽  
Gravity Flows ◽  
Digital Elevation

Upper-flow-regime bedforms and their role in the evolution of marine and lacustrine deltas are not well understood. Wave-like undulations on delta foresets are by far the most commonly reported bedforms on deltas and it will take time before many of these features get identified as upper-flow-regime bedforms. This study aims at: (1) Providing a summary of our knowledge to date on deltaic bedforms emplaced by sediment gravity flows; (2) illustrating that these features are most likely transitional upper-flow-regime bedforms; and (3) using field case studies of two markedly different deltas in order to examine their role in the evolution of deltas. The study combines numerical analysis with digital elevation models, outcrop, borehole, and high-resolution seismic data. The Mazzarrà river delta in the Gulf of Patti, Italy, is selected to show that upper-flow-regime bedforms in gullies can be linked to the onset, growth, and evolution of marine deltas via processes of gully initiation, filling, and maintenance. Ice-marginal lacustrine deltas in Germany are selected as they illustrate the importance of unconfined upper-flow-regime bedforms in the onset and evolution of distinct delta morphologies under different lake-level trends.

Sedimentology and stratigraphic affinities of Neoproterozoic coarse clastic successions, Glenshirra Group, Inverness-shire, Scotland

2004 ◽  
Vol 40 (2) ◽  
pp. 159-174 ◽  
Author(s):  
C. J. Banks ◽  
J. A. Winchester
Keyword(s):  
Sedimentary Rocks ◽  
Alluvial Fan ◽  
The West ◽  
Scottish Highlands ◽  
Marine Deposits ◽  
Sediment Gravity Flows ◽  
Gravity Flows ◽  
Subsequent Deformation ◽  
Shallow Water Sediments ◽  
Stratigraphic Sequences

SynopsisRecords of ancient environments and past basin histories can be preserved in metasedimentary successions, despite their subsequent deformation and metamorphism. In the Central Scottish Highlands SE of Loch Ness, the Garva Bridge Psammite and the Glen Buck Pebbly Psammite Formations (hitherto included within the Glenshirra Subgroup at the base of the Neoproterozoic Grampian Group) represent a continuum of alluvial fan to shallow water sediments, deposited in a SE thinning fan-delta clastic wedge. These sediments, derived from an uplifted granitoid hinterland to the west, contrast with the overlying marine sedimentary rocks of the Corrieyairack Subgroup, which were deposited by sediment gravity flows within a submarine slope setting. The Glen Buck Pebbly Psammite/Garva Bridge Psammite Formations and the Corrieyairack Subgroup represent two genetic stratigraphic sequences divided by a sharp sequence boundary that records a major reorganization in basin architecture. Hence, we propose that the Garva Bridge Psammite and Glen Buck Pebbly Psammite Formations be included within a separate Glenshirra Group, genetically unrelated to either the marine deposits of the immediately overlying Grampian Group or the earlier, locally migmatized (Moinian?) basement to the Central Highlands. The Glenshirra Group thus represents the earliest phase of post-Knoydartian extension, predating the main Dalradian basin development.

Resedimented conglomerates of Huronian (lower Aphebian) age, from the north shore of Lake Huron, Ontario, Canada

1977 ◽  
Vol 14 (11) ◽  
pp. 2495-2509 ◽  
Author(s):  
Darrel G. F. Long
Keyword(s):  
Matrix Material ◽  
Lake Huron ◽  
Fault System ◽  
North Shore ◽  
The North ◽  
Sediment Gravity Flows ◽  
Gravity Flows

Conglomeratic rocks are present near the top of a dominantly arenaceous sequence, previously ascribed entirely to the Huronian Mississagi Formation, in a belt extending for about 60 km east of Blind River, on the north shore of Lake Huron. These conglomeratic rocks and the massive and planar laminated sandstones which overlie them are herein named the Lauzon member, after the thickest exposed development of the sequence at Lauzon Lake in Striker Township. The presence of dropstones in the sequence at Lauzon Lake suggests that the member is best considered as part of the Bruce Formation. Conglomeratic rocks within the Lauzon member include granule-supported boulder, cobble, and pebble conglomerate; sand-supported cobble and pebble conglomerate; intact framework graded and non-graded pebble and cobble conglomerates; stratified conglomerates and conglomeratic sandstones; and disrupt framework conglomerates. These conglomeratic rocks lack abundant mud-grade matrix material and, hence, are readily distinguished from (glaciogenic?) mixtites of the Ramsay Lake, Bruce, and Gowganda Formations. Conglomerates of the Lauzon member were probably deposited from sediment gravity flows within a series of subaqueous fans or fan head valleys which may have been initiated by contemporaneous movements along a precursor to the Murray Fault system at the onset of the Bruce glaciation.

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