Morphological signature of gully development by rapid slide retrogression in a layered coarse-grained delta foreslope

2020 ◽  
Vol 500 (1) ◽  
pp. 219-234 ◽  
Author(s):  
Jacques Locat ◽  
Ali Azizian ◽  
Jim Stronach ◽  
Aurélien Hospital ◽  
Chris Young ◽  
...  
Keyword(s):  
High Resolution ◽  
Papua New Guinea ◽  
Friction Angle ◽  
Coarse Grained ◽  
Multibeam Bathymetry ◽  
Additional Source ◽  
Delta Front ◽  
Static Liquefaction ◽  
Liquefaction Failure ◽  
Delta Slope

AbstractCoarse-grained deltas are often characterized by steep foreslopes (often more than 10°) that are traversed by delta-front channels. The channels thus erode into relatively steeply inclined bedding. In this context, the slopes flanking the channels can be steeper than the friction angle since they include a component of dip related to the delta-front slope as well as the channel-related erosion slope. In this study, part of the Busu River delta (Papua New Guinea) was imaged using a high-resolution multibeam bathymetry survey over an area where the angle of the slopes flanking the channels locally reaches 50°. A detailed analysis of the delta slope morphology has revealed an additional source of instability due to erosion within the main channels. In some places, erosion cuts into the channel flank forming a local knickpoint inclined in a direction approaching that of the bed dip. The cut can then initiate breaching or static liquefaction failure from that point up to the crest of the interfluve resulting in a V-shaped gully.

scholarly journals New Recent foraminiferal genera and species from the lagoon at Madang, Papua New Guinea

1992 ◽  
Vol 11 (1) ◽  
pp. 85-93 ◽  
Author(s):  
Martin R. Langer
Keyword(s):  
New Species ◽  
Shallow Water ◽  
Papua New Guinea ◽  
New Guinea ◽  
Coarse Grained ◽  
New Genera ◽  
Low Oxygen ◽  
Shell Surface ◽  
Sedimentary Environments ◽  
Tropical Lagoon

Abstract. Two new genera and eight new species of benthic foraminifera are described from the shallow water, tropical lagoon of Madang, Papua New Guinea. The new hauerinid genus Pseudolachlanella is characterized by juvenile cryptoquinqueloculine, adult almost massiline arranged chambers, and a slitlike, curved aperture with parallel sides and a long, slender, curved miliolid tooth. Pitella haigi n. gen., n. sp. is a new foraminifera with cryptoquinqueloculine arranged chambers, an almost entirely pitted shell surface (pseudopores) and a rounded aperture with a short simple tooth. Among the other species described as new are four hauerinids and two agglutinated foraminifera All new species described here occur sporadically in the shallow water back- and forereef environments of the lagoon (0–55m), and live infaunally and epifaunally in well-oxygenated, fine and coarse grained biogenic sediments. They are absent in muddy, organic-rich, low-oxygen sedimentary environments within bay inlets where variations of salinity are considerable.

Influence of soil nail orientations on stabilizing mechanisms of loose fill slopes

2013 ◽  
Vol 50 (12) ◽  
pp. 1236-1249 ◽  
Author(s):  
C.Y. Cheuk ◽  
K.K.S. Ho ◽  
A.Y.T. Lam
Keyword(s):  
Earth Pressure ◽  
Slope Movement ◽  
Numerical Analyses ◽  
Soil Nails ◽  
Soil Nail ◽  
Static Liquefaction ◽  
Liquefaction Failure ◽  
Loose Fill ◽  
Typical Design

Soil nailing has been used to upgrade substandard loose fill slopes in Hong Kong. Due to the possibility of static liquefaction failure, a typical design arrangement comprises a structural slope facing anchored by a grid of soil nails bonded into the in situ ground. Numerical analyses have been conducted to examine the influence of soil nail orientations on the behaviour of the ground nail–facing system. The results suggest that the use of steeply inclined nails throughout the entire slope could avoid global instability, but could lead to significant slope movement especially when sliding failure prevails, for instance, due to interface liquefaction. The numerical analyses also demonstrate that if only subhorizontal nails are used, the earth pressure exerted on the slope facing may cause uplift failure of the slope cover. To overcome the shortcomings of using soil nails at a single orientation, a hybrid nail arrangement comprising nails at two different orientations is proposed. The numerical analyses illustrate that the hybrid nail arrangement would limit slope movement and enhance the robustness of the system.

scholarly journals High-resolution multibeam bathymetry of the northern Mid-Atlantic Ridge at 45–46° N: the Moytirra hydrothermal field

2021 ◽  
Vol 17 (2) ◽  
pp. 184-196
Author(s):  
Luis Somoza ◽  
Teresa Medialdea ◽  
Francisco J. González ◽  
Sara Machancoses ◽  
Jose A. Candón ◽  
...  
Keyword(s):  
High Resolution ◽  
Hydrothermal Field ◽  
Multibeam Bathymetry ◽  
Mid Atlantic Ridge

scholarly journals High-Resolution, Solvent-Free Coarse-Grained Model for Protein-Lipid Interactions

2011 ◽  
Vol 100 (3) ◽  
pp. 640a
Author(s):  
Tristan Bereau ◽  
Zun-Jing Wang ◽  
Markus Deserno
Keyword(s):  
High Resolution ◽  
Solvent Free ◽  
Coarse Grained ◽  
Lipid Interactions ◽  
Coarse Grained Model

Morphology and geological setting of Iseo Lake (Lombardy) through multibeam bathymetry and high-resolution seismic profiles

2007 ◽  
Vol 100 (1) ◽  
pp. 23-40 ◽  
Author(s):  
Alfredo Bini ◽  
Daniele Corbari ◽  
Paolo Falletti ◽  
Mauro Fassina ◽  
Cesare R. Perotti ◽  
...  
Keyword(s):  
High Resolution ◽  
Multibeam Bathymetry ◽  
Seismic Profiles ◽  
Geological Setting

DETERMINING RESERVOIR CONTINUITY IN THE LAMINARIA FORMATION BY INTEGRATED GEOLOGICAL STUDY

2001 ◽  
Vol 41 (1) ◽  
pp. 415 ◽  
Author(s):  
D.C. Barr ◽  
A.F. Kennaird ◽  
J. Fowles ◽  
N.G. Marshall ◽  
V.L. Cutten
Keyword(s):  
Grain Size ◽  
High Resolution ◽  
Sea Level ◽  
Clay Content ◽  
Coarse Grained ◽  
Log Data ◽  
Reservoir Performance ◽  
Subaqueous Dunes ◽  
Reservoir Sandstones ◽  
Reservoir Potential

A recent geological study, integrating sedimentological core-derived descriptions with ichnofacies, high resolution biostratigraphy and wireline log data, establishes the lateral continuity of reservoir sandstones in the Laminaria Formation. By defining a hierarchy of bedding surfaces and correlating this hierarchy with major correlation surfaces, and lateral and vertical facies patterns, it was possible to identify genetically related sediment packages between 12 wells in the study area.The Laminaria Formation is interpreted to have been deposited on a tide and storm-influenced marine shelf, and was strongly influenced by fluctuations in sea level. The formation consists of a series of progradational parasequences, each dominated by good quality, fine- to medium-grained sandstone. These sandstones are believed to have formed as subaqueous dunes or sand banks, exhibiting blanket-like geometry over much of the area. Several sandstones are capped by thin, intraclast-rich layers that mark transgressive surfaces of erosion. These surfaces can be traced across the study area and, therefore, act as important correlative markers.Evidence of gradual transgression, which ultimately led to the drowning of the system, is seen near the top of the formation. Clay content increases upward, while grain size and bedding thickness generally decrease. However, several thin, laterally extensive, medium- to coarse-grained sandstones exist, improving reservoir potential in this part of the formation.The results of this study are being used to estimate reserves and assess reservoir performance, and will serve as a basis for future geological and petrophysical modelling work.

scholarly journals The impact of inhomogeneous subgrid clumping on cosmic reionization

2019 ◽  
Vol 491 (2) ◽  
pp. 1600-1621
Author(s):  
Yi Mao ◽  
Jun Koda ◽  
Paul R Shapiro ◽  
Ilian T Iliev ◽  
Garrelt Mellema ◽  
...  
Keyword(s):  
High Resolution ◽  
Large Scale ◽  
Power Spectra ◽  
Coarse Grained ◽  
Small Scale ◽  
Sources And Sinks ◽  
Coarse Grained Simulations ◽  
Cent Error ◽  
Spatially Varying ◽  
The Impact

ABSTRACT Cosmic reionization was driven by the imbalance between early sources and sinks of ionizing radiation, both of which were dominated by small-scale structure and are thus usually treated in cosmological reionization simulations by subgrid modelling. The recombination rate of intergalactic hydrogen is customarily boosted by a subgrid clumping factor, 〈n2〉/〈n〉2, which corrects for unresolved fluctuations in gas density n on scales below the grid-spacing of coarse-grained simulations. We investigate in detail the impact of this inhomogeneous subgrid clumping on reionization and its observables, as follows: (1) Previous attempts generally underestimated the clumping factor because of insufficient mass resolution. We perform a high-resolution N-body simulation that resolves haloes down to the pre-reionization Jeans mass to derive the time-dependent, spatially varying local clumping factor and a fitting formula for its correlation with local overdensity. (2) We then perform a large-scale N-body and radiative transfer simulation that accounts for this inhomogeneous subgrid clumping by applying this clumping factor-overdensity correlation. Boosting recombination significantly slows the expansion of ionized regions, which delays completion of reionization and suppresses 21 cm power spectra on large scales in the later stages of reionization. (3) We also consider a simplified prescription in which the globally averaged, time-evolving clumping factor from the same high-resolution N-body simulation is applied uniformly to all cells in the reionization simulation, instead. Observables computed with this model agree fairly well with those from the inhomogeneous clumping model, e.g. predicting 21 cm power spectra to within 20 per cent error, suggesting it may be a useful approximation.

Sign in / Sign up

Export Citation Format

Share Document