scholarly journals Architecture, process, and environmental diversity in a late Cretaceous slope channel system

2020 ◽  
Vol 90 (1) ◽  
pp. 1-26 ◽  
Author(s):  
Benjamin Kneller ◽  
Guilherme Bozetti ◽  
Richard Callow ◽  
Mason Dykstra ◽  
Larissa Hansen ◽  
...  
Keyword(s):  
Building Blocks ◽  
Heavy Minerals ◽  
Coarse Grained ◽  
Turbidity Currents ◽  
Axial Region ◽  
Sedimentary Process ◽  
Channel System ◽  
Environmental Diversity ◽  
Channel Belt ◽  
Slope Channel

ABSTRACT Arroyo San Fernando, on the Pacific coast of Baja California, Mexico, provides a superb view of the architecture of a Maastrichtian active margin slope channel system and the record of its evolution through a third-order sea-level cycle. The succession is organized into architectural building blocks (channel-complex sets) consisting of a channel belt with an axial region and a channel-belt margin of terraces and internal levees. The channel belt is confined by an external levee on one side and by an erosion surface into the slope on the other. Each channel-complex set can be subdivided into three stages of evolution: Stage I consists of highly amalgamated coarse-grained channel complexes, Stage II consists of gravelly meander belts with marginal and stratigraphically intervening thin-bedded turbidites, and Stage III consists of mudstones representing abandonment. This succession is associated with repeated and therefore predictable changes in architecture, facies distribution, inferred seafloor morphology, and sedimentary process. We describe variability in the sedimentology, ichnology, palynology, provenance, and inferred sedimentary processes between and within these architectural elements. Channel formation and fill are attributed to erosion, sediment transport, and deposition by turbidity currents and lesser debris flows. Ichnology indicates enhanced oxygenation and supply of organic material, substrate type, and turbidity within the channel belt; the axial region can be differentiated from the terraces by differing response to turbidity-current intensity. Levee environments show ichnological gradients away from the channel towards background slope. Palynology reflects confinement of the supply of terrigenous material to the channel belt, but is also indicative of stratification within the turbidity-currents, as is the distribution of heavy minerals. Provenance is from the extinct part of the continental-margin arc to the east, via high-gradient gravelly streams and across a steep shoreline, with direct supply of coastal material to deep water. Architectural hierarchy bears comparison with other slope channel systems, but in common with them the fill represents only a small fraction of the time that the system was active.

scholarly journals Modeling intentional agency: a neo-Gricean framework

Synthese ◽  
2021 ◽  
Author(s):  
Matti Sarkia
Keyword(s):  
Philosophy Of Mind ◽  
General Framework ◽  
Building Blocks ◽  
Theoretical Modeling ◽  
Model Construction ◽  
Coarse Grained ◽  
Scientific Model ◽  
Types Of Knowledge ◽  
Different Types ◽  
Intentional Agency

AbstractThis paper analyzes three contrasting strategies for modeling intentional agency in contemporary analytic philosophy of mind and action, and draws parallels between them and similar strategies of scientific model-construction. Gricean modeling involves identifying primitive building blocks of intentional agency, and building up from such building blocks to prototypically agential behaviors. Analogical modeling is based on picking out an exemplary type of intentional agency, which is used as a model for other agential types. Theoretical modeling involves reasoning about intentional agency in terms of some domain-general framework of lawlike regularities, which involves no detailed reference to particular building blocks or exemplars of intentional agency (although it may involve coarse-grained or heuristic reference to some of them). Given the contrasting procedural approaches that they employ and the different types of knowledge that they embody, the three strategies are argued to provide mutually complementary perspectives on intentional agency.

scholarly journals Beachrock as a Paleoshoreline Indicator: Example from Wadi Al-Hamd, South Al-Wajh, Saudi Arabia

2021 ◽  
Vol 9 (9) ◽  
pp. 984 ◽  
Author(s):  
Ammar A. Mannaa ◽  
Rabea A. Haredy ◽  
Ibrahim M. Ghandour
Keyword(s):  
Saudi Arabia ◽  
Volcanic Rocks ◽  
Skeletal Remains ◽  
Heavy Minerals ◽  
Coarse Grained ◽  
Coralline Algae ◽  
Sea Level Changes ◽  
Pore Filling ◽  
Δ13c Values ◽  
Δ18o And Δ13c

The present study concerns the Holocene inland beachrocks that are exposed in the Red Sea coastal plain at the mouth of Wadi Al-Hamd, South Al-Wajh City, Saudi Arabia, and their utility as an indicator for Holocene climate and sea level changes. In addition, the framework composition, and carbon and oxygen isotopic data, are employed to interpret the origin of their cement. The beachrock consists mainly of gravel and coarse-grained terrigenous sediments dominated by lithic fragments of volcanic rocks, cherts and rare limestones along with quartz, feldspars and traces of amphiboles and heavy minerals. In addition, rare skeletal remains dominated by coralline algae, benthic foraminifera and mollusca remains are recognized. The allochems are cemented by high Mg-calcite (HMC) formed mainly in the intertidal zone under active marine phreatic conditions. The cement takes the form of isopachous to anisopachous rinds of bladed crystals, micritic rim non-selectively surrounding siliciclastic and skeletal remains, and pore-filling micrite. Pore-filling micrite cement occasionally displays a meniscus fabric, suggesting a vadose environment. The δ18O and δ13C values of carbonate cement range from −0.35‰ to 1‰ (mean 0.25‰) and −0.09‰ to 3.03‰ (mean 1.85‰), respectively, which are compatible with precipitation from marine waters. The slight depletion in δ18O and δ13C values in the proximal sample may suggest a slight meteoric contribution.

scholarly journals Heavy minerals in the Wajid Sandstone from Abha-Khamis Mushayt area, southwestern Saudi Arabia: implications on provenance and regional tectonic setting

GeoArabia ◽  
2004 ◽  
Vol 9 (4) ◽  
pp. 77-102 ◽  
Author(s):  
Mahbub Hussain ◽  
Lameed O. Babalola ◽  
Mustafa M. Hariri
Keyword(s):  
Saudi Arabia ◽  
Tectonic Setting ◽  
Principal Component ◽  
Heavy Mineral ◽  
Heavy Minerals ◽  
Coarse Grained ◽  
Distribution Data ◽  
The South ◽  
Quartz Content ◽  
The North

ABSTRACT The Wajid Sandstone (Ordovician-Permian) as exposed along the road-cut sections of the Abha and Khamis Mushayt areas in southwestern Saudi Arabia, is a mediun to coarse-grained, mineralogically mature quartz arenite with an average quartz content of over 95%. Monocrystalline quartz is the dominant framework grain followed by polycrystalline quartz, feldspar and micas. The non-opaque heavy mineral assemblage of the sandstone is dominated by zircon, tourmaline and rutile (ZTR). Additional heavy minerals, constituting a very minor fraction of the heavies, include epidote, hornblende, and kyanite. Statistical analysis showed significant correlations between zircon, tourmaline, rutile, epidote and hornblende. Principal component R-mode varimax factor analysis of the heavy mineral distribution data shows two strong associations: (1) tourmaline, zircon, rutile, and (2) epidote and hornblende suggesting several likely provenances including igneous, recycled sedimentary and metamorphic rocks. However, an abundance of the ZTR minerals favors a recycled sedimentary source over other possibilities. Mineralogical maturity coupled with characteristic heavy mineral associations, consistent north-directed paleoflow evidence, and the tectonic evolutionary history of the region indicate a provenance south of the study area. The most likely provenances of the lower part (Dibsiyah and Khusayyan members) of the Wajid Sandstone are the Neoproterozoic Afif, Abas, Al-Bayda, Al-Mahfid, and Al-Mukalla terranes, and older recycled sediments of the infra-Cambrian Ghabar Group in Yemen to the south. Because Neoproterozic (650-542 Ma) rocks are not widespread in Somalia, Eritrea and Ethiopia, a significant source further to the south is not likely. The dominance of the ultrastable minerals zircon, tourmaline and rutile and apparent absence of metastable, labile minerals in the heavy mineral suite preclude the exposed arc-derived oceanic terrains of the Arabian Shield in the west and north as a significant contributor of the sandstone. An abundance of finer-grained siliciclastic sequences of the same age in the north, is consistent with a northerly transport direction and the existence of a deeper basin (Tabuk Basin?) to the north. The tectonic and depositional model presented in this paper differs from the existing model that envisages sediment transportation and gradual basin filling from west to east during the Paleozoic.

Similar curvature-to-width ratios for channels and channel belts: Implications for paleo-hydraulics of fluvial ridges on Mars

Geology ◽  
2021 ◽  
Author(s):  
Alistair T. Hayden ◽  
Michael P. Lamb ◽  
Alexander J. Carney
Keyword(s):  
Coarse Grained ◽  
Scaling Relations ◽  
Radius Of Curvature ◽  
Finite Width ◽  
Lateral Migration ◽  
River Channels ◽  
Meandering Rivers ◽  
Channel Belt ◽  
Stacking Patterns ◽  
Geometric Consequence

The surface of Mars contains abundant sinuous ridges that appear similar to river channels in planform, but they stand as topographic highs. Ridges have similar curvature-to-width ratios as terrestrial meandering rivers, which has been used to support the hypothesis that ridges are inverted channels that directly reflect channel geometry. Anomalously wide ridges, in turn, have been interpreted as evidence for larger rivers on Mars compared to Earth. However, an alternate hypothesis is that ridges are exhumed channel-belt deposits—a larger zone of relatively coarse-grained deposits formed from channel lateral migration and aggradation. Here, we measured landform wavelength, radius of curvature, and width to compare terrestrial channels, terrestrial channel belts, and martian ridges. We found that all three landforms follow similar scaling relations, in which ratios of radius of curvature to width range from 1.7 to 7.3, and wavelength-to-width ratios range from 5.8 to 13. We interpret this similarity to be a geometric consequence of a sinuous curved line of finite width. Combined with observations of ridge-stacking patterns, our results suggest that wide ridges on Mars could indicate fluvial channel belts that formed over significant time rather than anomalously large rivers.

scholarly journals Simulations of the 2D self-assembly of tripod-shaped building blocks

2020 ◽  
Vol 11 ◽  
pp. 884-890
Author(s):  
Łukasz Baran ◽  
Wojciech Rżysko ◽  
Edyta Słyk
Keyword(s):  
Molecular Dynamics ◽  
Monte Carlo ◽  
Diffraction Pattern ◽  
Triangular Lattice ◽  
Self Assembly ◽  
Building Blocks ◽  
Coarse Grained ◽  
Coarse Grained Model

We introduce a molecular dynamics (MD) coarse-grained model for the description of tripod building blocks. This model has been used by us already for linear, V-shape, and tetratopic molecules. We wanted to further extend its possibilities to trifunctional molecules to prove its versatility. For the chosen systems we have also compared the MD results with Monte Carlo results on a triangular lattice. We have shown that the constraints present in the latter method can enforce the formation of completely different structures, not reproducible with off-lattice simulations. In addition to that, we have characterized the obtained structures regarding various parameters such as theoretical diffraction pattern and average association number.

scholarly journals The marine record of the Russell Fiord outburst flood, Alaska, U.S.A.

1996 ◽  
Vol 22 ◽  
pp. 194-199 ◽  
Author(s):  
Ellen A. Cowan ◽  
Paul R. Carlson ◽  
Ross D. Powell
Keyword(s):  
High Resolution ◽  
Debris Flow ◽  
Seismic Reflection ◽  
Seismic Facies ◽  
Turbidity Currents ◽  
Outburst Flood ◽  
Gravity Core ◽  
Channel System ◽  
Seismic Reflection Profiles ◽  
Long Channel

The advance of Hubbard Glacier, near Yakutat, Alaska, U.S.A., in spring 1986 blocked the entrance to Russell Fiord with an ice-and-sediment dam, behind which a lake formed. The water level in Russell Lake rose to 25.5 m a.s.l. The dam catastrophically failed in October 1986, releasing 5.4 km3of water into Disenchantment Bay. High-resolution seismic-reflection profiles show a 7.5 km long channel system cut into and buried by glacimarine sediment, represented by continuous, parallel reflections. The chaotic seismic facies filling the channel is interpreted to be debris flow deposits. A gravity core from channel-overbank deposits contained sandy diamicton with mud clasts. Above the channel a 1–2 m thick sediment drape extends across the bay. Laminated mud, fining-upward sand beds and diamicton were recovered from this unit. The sediment-drape deposits were produced by suspension settling from turbid plumes and non-channelized turbidity currents generated by the outburst flood.

scholarly journals Coarse-Grained Molecular Dynamics Simulations of Nanoplastics Interacting with a Hydrophobic Environment in Aqueous Solution

2021 ◽  
Author(s):  
Lorenz Dettmann ◽  
Oliver Kühn ◽  
Ashour A. Ahmed
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Functional Groups ◽  
Critical Role ◽  
Terrestrial Ecosystems ◽  
Building Blocks ◽  
Coarse Grained ◽  
Hydrophobic Polymers ◽  
Dynamics Simulations ◽  
Coarse Grained Molecular Dynamics

<div><div><div><p>Nanoplastics (NPs) are emerging threats for marine and terrestrial ecosystems, but little is known about their fate in the environment at the molecular scale. In this work, coarse-grained molecular dynamics simulations were performed to investigate nature and strength of the interaction between NPs and hydrophobic environments. Specifically, NPs were simulated with different hydrophobic and hydrophilic polymers while carbon nanotubes (CNTs) were used to mimic surface and confinement effects of hydrophobic building blocks occurring in a soil environment. The hydrophobicity of CNTs was modified by introducing different hydrophobic and hydrophilic functional groups at their inner surfaces. The results show that hydrophobic polymers have a strong affinity to adsorb at the outer surface and to be captured inside the CNT. The accumulation within the CNT is even increased in presence of hydrophobic functional groups. This contribution is a first step towards a mechanistic understanding of a variety of processes connected to interaction of nanoscale material with environmental systems. Regarding the fate of NPs in soil, the results point to the critical role of the hydrophobicity of NPs and soil organic matter (SOM) as well as of the chemical nature of functionalized SOM cavities/voids in controlling the accumulation of NPs in soil. Moreover, the results can be related to water treatment technologies as it is shown that the hydrophobicity of CNTs and functionalization of their surfaces may play a crucial role in enhancing the adsorption capacity of CNTs with respect to organic compounds and thus their removal efficiency from wastewater.</p><p><br></p></div></div></div>

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