Modern Death Assemblages and Pleistocene Fossil Assemblages in Open Coast High Energy Environments, San Nicolas Island, California

Palaios ◽  
1991 ◽  
Vol 6 (2) ◽  
pp. 179 ◽  
Author(s):  
Michael P. Russell
Keyword(s):  
High Energy ◽  
San Nicolas Island ◽  
Open Coast ◽  
Death Assemblages ◽  
Fossil Assemblages

MOLLUSCAN LIVE-DEAD FIDELITY OF A STORM-DOMINATED SHALLOW-MARINE SETTING AND ITS IMPLICATIONS

Palaios ◽  
2021 ◽  
Vol 36 (2) ◽  
pp. 77-93
Author(s):  
MADHURA BHATTACHERJEE ◽  
DEVAPRIYA CHATTOPADHYAY ◽  
BIDISHA SOM ◽  
AMMU S. SANKAR ◽  
SATYAKI MAZUMDER
Keyword(s):  
Frequency Distribution ◽  
Large Scale ◽  
Regional Distribution ◽  
High Energy ◽  
Shell Size ◽  
Size Frequency Distribution ◽  
Shallow Marine ◽  
Size Frequency ◽  
Optimal Setting ◽  
Fossil Assemblages

ABSTRACT Actualistic studies are important for evaluating the fidelity of fossil assemblages in representing the living community. Poor live-dead (LD) fidelity in molluscan assemblages may result from transport-induced mixing. Large-scale mixing is more common in siliciclastic settings with a narrow shelf, high sedimentation rate, and those that are frequented by episodically high-energy events. Chandipur-on-sea, on the east coast of India has an optimal setting to promote such conditions. By studying the LD fidelity and modeling size-frequency distribution (SFD) of the fauna, we attempted to evaluate the contribution of “out-of-habitat” versus “within-habitat” mixing in developing the molluscan death assemblage. The correlation between the composition of live (LA) and death assemblages (DA) was insufficient; unlike LAs, the DAs do not show environmental partitioning in ordination space. A numerical simulation of the shell size frequency distribution (SFD) for DAs from LAs was compared with the observed SFD of the DAs. The results of this simulation indicate that DAs are not likely to be a product of within-habitat mixing. DAs probably received considerable input via regional transport, facilitated by frequent tropical cyclones affecting the coast of Odisha. Chandipur receives a large proportion of cyclones originating above 15°N, which causes a high degree of lateral transport and shell mixing between 15° to 21°N, explained by the high compositional similarity of species within this latitudinal extent. Our study highlights the significance of out-of-habitat transport in shaping the regional distribution of marine fossil assemblages, especially in storm dominated siliciclastic shallow-marine settings.

scholarly journals What Darwin did not see: Pleistocene fossil assemblages on a high-energy coast at Ponta das Bicudas, Santiago, Cape Verde Islands

2012 ◽  
Vol 150 (1) ◽  
pp. 183-189 ◽  
Author(s):  
B. GUDVEIG BAARLI ◽  
ANA G. SANTOS ◽  
EDUARDO J. MAYORAL ◽  
JORGE LEDESMA-VÁZQUEZ ◽  
MARKES E. JOHNSON ◽  
...  
Keyword(s):  
Rocky Shore ◽  
High Energy ◽  
Cape Verde ◽  
Tidal Zone ◽  
Cape Verde Islands ◽  
Low Diversity ◽  
Fossil Assemblages ◽  
Santiago Island

AbstractTwo distinct Pleistocene assemblages from SE Santiago Island are comparable to modern analogues elsewhere in the Cape Verde Islands. A low-diversity Siderastrea radians assemblage lived atop basalt knobs surrounded by sand on a slope below a cliff. A Millepora alcicornis–Megabalanus azoricus assemblage occupied the cliff. The latter was a typical rocky-shore assemblage from a high-energy setting below the tidal zone. Bioerosion structures in basalt produced by Circolites kotoncensis and Gastrochaenolites isp. also occur there. Despite extensive studies on local limestone deposits in 1832 and 1836, lack of exposure prevented Darwin from seeing these fossils.

Microwear–mesowear congruence and mortality bias in rhinoceros mass-death assemblages

Paleobiology ◽  
2017 ◽  
Vol 44 (1) ◽  
pp. 131-154 ◽  
Author(s):  
Matthew C. Mihlbachler ◽  
Daniel Campbell ◽  
Charlotte Chen ◽  
Michael Ayoub ◽  
Pawandeep Kaur
Keyword(s):  
Cause Of Death ◽  
Seasonal Change ◽  
Feeding Ecology ◽  
Dental Microwear ◽  
Dental Wear ◽  
Ecological Stress ◽  
Death Assemblages ◽  
Fossil Assemblages ◽  
Stochastic Events ◽  
Ecological Disturbances

AbstractAlthough we do not know the cause of death of most fossil animals, mortality is often associated with ecological stress due to seasonality and other stochastic events (droughts, storms, volcanism) that may have caused shifts in feeding ecology preceding death. In these instances, dental microwear, which reflects feeding ecology in a narrow window of time, may provide a biased view of diet. Mesowear, another dental-wear proxy based on the morphology of worn cusps, requires macroscopic amounts of dental wear and reflects diet for a longer interval and may be less prone to bias from near-death ecological stress. We compared congruence between microwear and mesowear of North American, fossil rhinocerotid mass-death assemblages and collections of hunted modern rhinocerotids to test the hypothesis that fossil assemblages yield more incongruous microwear and mesowear data as a result of near-death ecological disturbances. In extant rhinos, both mesowear and microwear are associated with diet and height of the feeding environment. Mesowear and microwear in the modern rhinocerotid collections are statistically correlated, with strong relationships between average mesowear scores and labially distributed dental microwear. In contrast, a relationship between mesowear and microwear was not observed among the fossil rhinocerotid assemblages. Mesowear suggests that the fossil rhinos had low-abrasion diets, suggesting that they fed from clean, possibly tall vegetation. Some, but not all, mass-death assemblages produce microwear data with excessive scratches and/or pits compared with expectations based on mesowear results, suggesting that dental microwear was altered shortly before death in some but not all of the fossil assemblages. The dental-wear proxies available to paleoecologists provide a mosaic of dietary evidence reflecting diet over long (mesowear) and more abbreviated (microwear) periods of time that, together, provide a richer understanding of feeding ecology and its relationship to environment, seasonal change, and other ecological disturbances.

Modelling transport of larval New Zealand abalone (Haliotis iris) along an open coast

2006 ◽  
Vol 57 (5) ◽  
pp. 519 ◽  
Author(s):  
S. A. Stephens ◽  
N. Broekhuizen ◽  
A. B. Macdiarmid ◽  
C. J. Lundquist ◽  
L. McLeod ◽  
...  
Keyword(s):  
New Zealand ◽  
Larval Dispersal ◽  
Release Site ◽  
High Energy ◽  
Energy Conditions ◽  
Important Species ◽  
Open Coast ◽  
Successful Recruitment ◽  
Starting Point ◽  
Near Shore

The dispersal and transport of larval New Zealand abalone Haliotis iris was simulated using coupled two-dimensional hydrodynamic and Lagrangian particle-trajectory models. The aim was to estimate pelagic larval dispersal potential along the open coast, as a starting point from which basic management questions can be made for this recreationally and commercially important species. Larval dispersal was simulated from representative spawning sites under a range of representative hydrodynamic conditions, including wave-induced circulation cells. Larval presence over near-shore reef habitat declined as the energy of the flow field and corresponding larval dispersal and transport increased. Thus, spawning during high-energy conditions will promote dispersal and transport but reduce successful recruitment on near-shore reefs. This indicates that seeding of the adjacent coast is likely to be sporadic, with existing populations necessarily being somewhat self-recruiting. Results suggest that an ideal management system would ensure that adult populations were maintained at intervals of 10–30 km along the coast to maintain larval supply to areas in between. Dispersal characteristics were specific to the release site, and the simulations suggest that marine reserves can be positioned to accordingly achieve desired functions: for example, optimal choices can be made for seeding areas, recruitment or self-maintaining areas.

Ecophenotypy, temporal and spatial fidelity, functional morphology, and physiological trade-offs among intertidal bivalves

Paleobiology ◽  
2018 ◽  
Vol 44 (3) ◽  
pp. 530-545
Author(s):  
John Warren Huntley ◽  
James D. Schiffbauer ◽  
Teresa D. Avila ◽  
Jesse S. Broce
Keyword(s):  
High Energy ◽  
Shell Morphology ◽  
Time Averaging ◽  
Spatial Averaging ◽  
Substrate Type ◽  
Fine Grained ◽  
Trade Offs ◽  
Death Assemblages ◽  
Temporal And Spatial ◽  
Type Water

AbstractEcophenotypic variation in populations is driven by differences in environmental variables. In marine environments, ecophenotypic variation may be caused by differences in hydrodynamic conditions, substrate type, water depth, temperature, salinity, oxygen concentration, and habitat heterogeneity, among others. Instances of ecophenotypic variation in modern and fossil settings are common, but little is known about the influences of time averaging and spatial averaging on their preservation. Here we examine the shell morphology of two adjacent populations, both live collected and death assemblages, of the infaunal, suspension-feeding, intertidal bivalve Leukoma staminea from the well-studied Argyle Creek and Argyle Lagoon locations on San Juan Island, Washington. Individuals in the low-energy lagoon are free to burrow in the fine-grained substrate, while clams in the high-energy creek are precluded from burrowing in the rocky channel. Our results demonstrate variation in size and shape between the adjacent habitats. Lagoon clams are larger, more disk-shaped, and have relatively larger siphons than their creek counterparts, which are smaller, more spherical in shape, and have a relatively shallower pallial sinus. This ecophenotypy is preserved among death assemblages, although with generally greater variation due to time averaging and shell transport. Our interpretation is that ecophenotypic variation, in this case, is induced by differing hydrodynamic regimes and substrate types, cumulatively resulting in physiological trade-offs diverting resources from feeding and respiration to stability and shell strength, all of which have the potential to be preserved in the fossil record.

The E-ring: interactions with plasma and implications for its evolution

1984 ◽  
Vol 75 ◽  
pp. 599-602
Author(s):  
T.V. Johnson ◽  
G.E. Morfill ◽  
E. Grun
Keyword(s):  
Time Scale ◽  
Particle Density ◽  
High Energy ◽  
Particle Removal ◽  
Density Region ◽  
Drag Forces ◽  
Orbit Evolution ◽  
History Of ◽  
Ring Particle ◽  
Ring Material

A number of lines of evidence suggest that the particles making up the E-ring are small, on the order of a few microns or less in size (Terrile and Tokunaga, 1980, BAAS; Pang et al., 1982 Saturn meeting; Tucson, AZ). This suggests that a variety of electromagnetic and plasma affects may be important in considering the history of such particles. We have shown (Morfill et al., 1982, J. Geophys. Res., in press) that plasma drags forces from the corotating plasma will rapidly evolve E-ring particle orbits to increasing distance from Saturn until a point is reached where radiation drag forces acting to decrease orbital radius balance this outward acceleration. This occurs at approximately Rhea's orbit, although the exact value is subject to many uncertainties. The time scale for plasma drag to move particles from Enceladus' orbit to the outer E-ring is ~104yr. A variety of effects also act to remove particles, primarily sputtering by both high energy charged particles (Cheng et al., 1982, J. Geophys. Res., in press) and corotating plasma (Morfill et al., 1982). The time scale for sputtering away one micron particles is also short, 102 - 10 yrs. Thus the detailed particle density profile in the E-ring is set by a competition between orbit evolution and particle removal. The high density region near Enceladus' orbit may result from the sputtering yeild of corotating ions being less than unity at this radius (e.g. Eviatar et al., 1982, Saturn meeting). In any case, an active source of E-ring material is required if the feature is not very ephemeral - Enceladus itself, with its geologically recent surface, appears still to be the best candidate for the ultimate source of E-ring material.

Analysis of electron-diffraction intensity profiles using a photodiode-array detection system

1983 ◽  
Vol 41 ◽  
pp. 322-323
Author(s):  
J. B. Warren
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Detection System ◽  
High Energy ◽  
Photographic Emulsion ◽  
Diffraction Intensity ◽  
Silicon Photodiode ◽  
Photodiode Array Detection ◽  
Analog To Digital ◽  
Photodiode Array

Electron diffraction intensity profiles have been used extensively in studies of polycrystalline and amorphous thin films. In previous work, diffraction intensity profiles were quantitized either by mechanically scanning the photographic emulsion with a densitometer or by using deflection coils to scan the diffraction pattern over a stationary detector. Such methods tend to be slow, and the intensities must still be converted from analog to digital form for quantitative analysis. The Instrumentation Division at Brookhaven has designed and constructed a electron diffractometer, based on a silicon photodiode array, that overcomes these disadvantages. The instrument is compact (Fig. 1), can be used with any unmodified electron microscope, and acquires the data in a form immediately accessible by microcomputer.Major components include a RETICON 1024 element photodiode array for the de tector, an Analog Devices MAS-1202 analog digital converter and a Digital Equipment LSI 11/2 microcomputer. The photodiode array cannot detect high energy electrons without damage so an f/1.4 lens is used to focus the phosphor screen image of the diffraction pattern on to the photodiode array.

Observation of Superlattice Dislocations on Cube Planes in Ni3Al

1973 ◽  
Vol 31 ◽  
pp. 174-175 ◽  
Author(s):  
J. M. Oblak ◽  
W. H. Rand
Keyword(s):  
Nearest Neighbor ◽  
Antiphase Boundary ◽  
Nearest Neighbors ◽  
High Energy ◽  
Cross Slip ◽  
Octahedral Plane ◽  
Trapping Mechanism ◽  
Slip Traces

The energy of an a/2 <110> shear antiphase. boundary in the Ll2 expected to be at a minimum on {100} cube planes because here strue ture is there is no violation of nearest-neighbor order. The latter however does involve the disruption of second nearest neighbors. It has been suggested that cross slip of paired a/2 <110> dislocations from octahedral onto cube planes is an important dislocation trapping mechanism in Ni3Al; furthermore, slip traces consistent with cube slip are observed above 920°K.Due to the high energy of the {111} antiphase boundary (> 200 mJ/m2), paired a/2 <110> dislocations are tightly constricted on the octahedral plane and cannot be individually resolved.

Microfabrication research at the National Submicron Facility

1983 ◽  
Vol 41 ◽  
pp. 86-89
Author(s):  
E.D. Wolf
Keyword(s):  
Integrated Circuits ◽  
Particle Physics ◽  
High Speed ◽  
New Technology ◽  
High Energy ◽  
High Energy Particle ◽  
New Science ◽  
Wide Range ◽  
Intermediate Domain ◽  
Circuit Function

Most microelectronics devices and circuits operate faster, consume less power, execute more functions and cost less per circuit function when the feature-sizes internal to the devices and circuits are made smaller. This is part of the stimulus for the Very High-Speed Integrated Circuits (VHSIC) program. There is also a need for smaller, more sensitive sensors in a wide range of disciplines that includes electrochemistry, neurophysiology and ultra-high pressure solid state research. There is often fundamental new science (and sometimes new technology) to be revealed (and used) when a basic parameter such as size is extended to new dimensions, as is evident at the two extremes of smallness and largeness, high energy particle physics and cosmology, respectively. However, there is also a very important intermediate domain of size that spans from the diameter of a small cluster of atoms up to near one micrometer which may also have just as profound effects on society as “big” physics.

Void-Lattice Formation in Natural Fluorite by Electron Irradiation

1976 ◽  
Vol 34 ◽  
pp. 614-615 ◽  
Author(s):  
L.E. Murr
Keyword(s):  
Electron Microscope ◽  
Electron Irradiation ◽  
Heavy Ion ◽  
High Energy ◽  
Stoichiometric Ratio ◽  
Direct Observations ◽  
Transmission Electron ◽  
Anion Vacancies ◽  
Cation And Anion Vacancies ◽  
Lattice Formation

The production of void lattices in metals as a result of displacement damage associated with high energy and heavy ion bombardment is now well documented. More recently, Murr has shown that a void lattice can be developed in natural (colored) fluorites observed in the transmission electron microscope. These were the first observations of a void lattice in an irradiated nonmetal, and the first, direct observations of color-center aggregates. Clinard, et al. have also recently observed a void lattice (described as a high density of aligned "pores") in neutron irradiated Al2O3 and Y2O3. In this latter work, itwas pointed out that in order that a cavity be formed,a near-stoichiometric ratio of cation and anion vacancies must aggregate. It was reasoned that two other alternatives to explain the pores were cation metal colloids and highpressure anion gas bubbles.Evans has proposed that void lattices result from the presence of a pre-existing impurity lattice, and predicted that the formation of a void lattice should restrict swelling in irradiated materials because it represents a state of saturation.

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