scholarly journals Diversity patterns and palaeoecology of benthic communities of the Kanosh Formation (Pogonip Group, Utah, western USA)

2020 ◽  
Vol 100 (4) ◽  
pp. 993-1006
Author(s):  
Richard Hofmann ◽  
Jan Philipp Kehl
Keyword(s):  
Great Basin ◽  
Benthic Communities ◽  
Habitat Diversity ◽  
Shelf Zone ◽  
Base Line ◽  
Benthic Assemblages ◽  
Diversity Patterns ◽  
Fine Grained ◽  
Type Area ◽  
Western Us

AbstractThe Dapingian to Darriwilian Kanosh Formation is one of the most fossiliferous units of the Pogonip Group (Great Basin, western US). It records a critical phase of the so-called Great Ordovician Biodiversification Event (GOBE) during which many marine clades diversified on lower systematic levels. However, a comprehensive palaeoecological analysis has not been presented for this unit so far. Based on newly collected material from three sections in the type area at Ibex, we reconstruct benthic marine communities, analyse diversity patterns, and discuss its significance for the GOBE. We find no differences in species’ composition across the formation with respect to brachiopods. Benthic assemblages are dominated by Shoshonorthis michaelis, alongside the presence of Anomalorthis lonensis and Anomalorthis utahensis across the whole unit. Trilobites show a more pronounced facies restriction with species of Kanoshia and Pseudomera being observed in more proximal limestone whereas Bathyurellus and Pseudoolenoides occur in fine-grained, low-energy deposits. The skeletal limestone also records abundant bioclasts of bryozoans, echinoderms, and receptaculitids, suggesting an ecologically diverse and tiered community being present in the inner shelf zone. However, most of these groups are not particularly diverse in terms of species richness. This implies that principle establishment of typical members of the “Palaeozoic Fauna” is not associated with a local diversification of clades. The comparably low habitat diversity of the Kanosh Fauna likely reflects environmental constraints such as high rates of siliclastic input. Additionally, these mainly Dapingian communities still represent a base-line fauna before the principal diversification took place.

scholarly journals Are different benthic communities in Arctic delta lakes distinguishable along a hydrological connectivity gradient using a rapid bioassessment approach?

2020 ◽  
Vol 6 (4) ◽  
pp. 463-487
Author(s):  
Ryan W. Scott ◽  
Suzanne E. Tank ◽  
Xiaowa Wang ◽  
Roberto Quinlan
Keyword(s):  
Climate Change ◽  
Benthic Communities ◽  
Mackenzie Delta ◽  
Benthic Assemblages ◽  
Community Based ◽  
Rapid Bioassessment ◽  
The Family ◽  
Productivity Gradients ◽  
To Come ◽  
Potential Use

Aquatic habitats in the Canadian Arctic are expected to come under increasing stress due to projected effects of climate change. There is a need for community-based biomonitoring programs to observe and understand the effects of these stressors on the environment. Here we present results from a 5 year annual sampling program of benthic invertebrates from lakes in the Mackenzie Delta, Northwest Territories, using a rapid bioassessment protocol. Connectivity between the deltaic lakes and main channels is a major driver of lake function and is expected to be substantially impacted by climate change. Lakes were selected along a gradient of connectivity based on sill elevation above the river. Using multivariate analyses of community structure, we determined that benthic assemblages responded to differences in connection time among lakes. This response was detected using a coarse taxonomic level that could be applied by community groups or volunteers but was stronger when invertebrates were identified to the family and genus levels. A secondary gradient was observed that corresponded to productivity gradients in lakes that are isolated from the river during summer. We show that benthic assemblages have potential use as sensitive indicators of climate-mediated changes to the hydrology of lakes in the Mackenzie Delta.

scholarly journals Unusually variable paleocommunity composition in the oldest metazoan fossil assemblages

Paleobiology ◽  
2019 ◽  
Vol 45 (02) ◽  
pp. 235-245 ◽  
Author(s):  
Seth Finnegan ◽  
James G. Gehling ◽  
Mary L. Droser
Keyword(s):  
Fossil Record ◽  
Benthic Communities ◽  
Benthic Assemblages ◽  
Β Diversity ◽  
Marine Habitats ◽  
Fossil Assemblages ◽  
Early Metazoan ◽  
Insight Into ◽  
Faunal Variability ◽  
Ecological Differences

AbstractRecent excavations of Ediacaran assemblages have revealed striking bed-to-bed variation in diversity–abundance structure, offering potential insight into the ecology and taphonomy of these poorly understood early Metazoan ecosystems. Here we compare faunal variability in Ediacaran assemblages to that of younger benthic assemblages, both fossil and modern. We decompose the diversity of local assemblages into within-collection (α) and among-collection (β) components and show that β diversity in Ediacaran assemblages is unusually high relative to younger assemblages. Average between-bed ecological dissimilarities in the Phanerozoic fossil record are comparable to within-habitat dissimilarities typically observed over meter to kilometer scales in modern benthic marine habitats, but dissimilarities in Ediacaran assemblages are comparable to those typically observed over 10–100 km scales in modern habitats. We suggest that the unusually variable diversity–abundance structure of Ediacaran assemblages is due both to their preservation as near snapshots of benthic communities and to original ecological differences, in particular the paucity of motile taxa and the near lack of predation and infaunalization.

scholarly journals Ecological regime shift preserved in the Anthropocene stratigraphic record

2020 ◽  
Vol 287 (1929) ◽  
pp. 20200695 ◽  
Author(s):  
Adam Tomašových ◽  
Paolo G. Albano ◽  
Tomáš Fuksi ◽  
Ivo Gallmetzer ◽  
Alexandra Haselmair ◽  
...  
Keyword(s):  
Twentieth Century ◽  
Fossil Record ◽  
Regime Shift ◽  
Benthic Communities ◽  
Ecological Change ◽  
Benthic Assemblages ◽  
Northern Adriatic ◽  
Ecological Release ◽  
Continental Shelves ◽  
Decadal Scale

Palaeoecological data are unique historical archives that extend back far beyond the last several decades of ecological observations. However, the fossil record of continental shelves has been perceived as too coarse (with centennial-millennial resolution) and incomplete to detect processes occurring at yearly or decadal scales relevant to ecology and conservation. Here, we show that the youngest (Anthropocene) fossil record on the northern Adriatic continental shelf provides decadal-scale resolution that accurately documents an abrupt ecological change affecting benthic communities during the twentieth century. The magnitude and the duration of the twentieth century shift in body size of the bivalve Corbula gibba is unprecedented given that regional populations of this species were dominated by small-size classes throughout the Holocene. The shift coincided with compositional changes in benthic assemblages, driven by an increase from approximately 25% to approximately 70% in median per-assemblage abundance of C. gibba . This regime shift increase occurred preferentially at sites that experienced at least one hypoxic event per decade in the twentieth century. Larger size and higher abundance of C. gibba probably reflect ecological release as it coincides with an increase in the frequency of seasonal hypoxia that triggered mass mortality of competitors and predators. Higher frequency of hypoxic events is coupled with a decline in the depth of intense sediment mixing by burrowing benthic organisms from several decimetres to less than 20 cm, significantly improving the stratigraphic resolution of the Anthropocene fossil record and making it possible to detect sub-centennial ecological changes on continental shelves.

Reconsidering Paleoarchaic Mobility in the Central Great Basin

2012 ◽  
Vol 77 (2) ◽  
pp. 351-367 ◽  
Author(s):  
George T. Jones ◽  
Lisa M. Fontes ◽  
Rachel A. Horowitz ◽  
Charlotte Beck ◽  
David G. Bailey
Keyword(s):  
Home Range ◽  
Great Basin ◽  
Stone Tools ◽  
Fluorescence Spectrometry ◽  
Zone Model ◽  
X Ray ◽  
Fine Grained

AbstractAnalyzing technological patterns and source provenance of stone tools, Jones, Beck, Jones, and Hughes (2003) argue that Paleoarchuic groups of the central Great Basin moved within an extensive home range, perhaps reaching 400 km in its longest dimension. The Eastern Conveyance Zone, as they refer to this territory, was aligned with the predominantly north-south trending mountains and valleys of the province. To evaluate this model of mobility, artifacts were collected from the southern part of the Eastern Conveyance Zone for geochemical characterizations. X-ray fluorescence spectrometry of 183 obsidian and fine-grained volcanic artifacts identified 12 known rock sources, all from the southern and central sections of the zone. No northern sources are represented among artifacts studied. Revisions of the Eastern Conveyance Zone model are considered in light of these results.

Holocene Environmental Change, Artiodactyl Abundances, and Human Hunting Strategies in the Great Basin

2004 ◽  
Vol 69 (2) ◽  
pp. 235-255 ◽  
Author(s):  
David A. Byers ◽  
Jack M. Broughton
Keyword(s):  
Environmental Change ◽  
Great Basin ◽  
Late Holocene ◽  
Coarse Grained ◽  
Population Increase ◽  
Hunting Behavior ◽  
Fine Grained ◽  
Hunting Strategies ◽  
Bonneville Basin ◽  
Holocene Environmental Change

Despite a deep Great Basin tradition of incorporating paleoenvironmental change within ecologically oriented analyses of past human lifeways, there has been little attention focused on Holocene variation in artiodactyl abundances and the human hunting strategies dependent upon them. Here, we draw upon recently generated paleontological evidence from Homestead Cave of the Bonneville Basin to document a late Holocene artiodactyl population increase. We then use the prey model of foraging theory to predict late Holocene increases in the hunting of artiodactyls, relative to lagomorphs. That prediction is then tested against several fine-grained archaeological records of hunting behavior in the Bonneville Basin, Hogup Cave and Camels Back Cave, and a variety of more coarse-grained faunal records from throughout the Great Basin. Close fits are found between the deductively derived prediction and the empirical records of hunting behavior: dramatic proportional increases in artiodactyl hunting occurred during the late Holocene. The results have far-reaching implications for our understanding of prehistoric human adaptations in the Great Basin.

Superplastic Forming Characteristics of a Fine-Grained Cu-Based Shape Memory Alloy

2012 ◽  
Vol 579 ◽  
pp. 22-31
Author(s):  
Chin Chuan Hsu
Keyword(s):  
Superplastic Forming ◽  
Rate Of Change ◽  
Dome Height ◽  
Base Line ◽  
Fine Grained ◽  
Forming Temperature ◽  
Forming Characteristics ◽  
Temperature And Pressure ◽  
Increasing Temperature ◽  
Free Bulging

The influences of temperature and pressure on the blow forming of CuZnAlZr sheet was investigated under free bulging conditions using argon gas. The effects evaluated were the dome height, measured at the dome apex; the specific thickness, the ratio of the actual thickness to the initial thickness; and the thinning factor, the ratio of the actual thickness to the average thickness. The results show that the dome height and the rate of change of dome height with respect to time, dh/dt, increase with increasing temperature and/or pressure. The specific thickness decreases with increasing fractional height (the ratio of the height of a given point above the base line to the height of the apex), and the specific thickness at the apex decreases with increasing temperature and/or pressure as well. The thinning factor decreases with increasing fractional height. Furthermore, this decrease becomes more significant with an increase in either the forming temperature or pressure. The thinning factor at the apex, as a function of the height to base ratio for all conditions falls into the region between m=0.3 and m=0.75 curves.

scholarly journals Surface sediment chemistry in the Olympic Games 2004 Sailing Center (Saronikos Gulf)

2003 ◽  
Vol 4 (1) ◽  
pp. 5 ◽  
Author(s):  
A.P. KARAGEORGIS ◽  
I. HATZIANESTIS
Keyword(s):  
Heavy Metal ◽  
Olympic Games ◽  
Anthropogenic Pollution ◽  
Anthropogenic Sources ◽  
Sediment Chemistry ◽  
Base Line ◽  
Fine Grained ◽  
Rock Formations ◽  
Marine Traffic ◽  
The Olympic Games

Construction of the Olympic Games 2004 Sailing Center is planned in the Saronikos Gulf, in the area of Agios Kosmas. A multi-disciplinary base-line study was carried out to provide background levels of inorganic and organic pollutants before the construction. Two shallow reefs (water depth 2-3 m) are the predominant features in the area’s underwater topography. The reef consists of solid rock formations and pebbles, whereas sandy sediments cover predominantly the remaining seabed. Some pockets of fine-grained sand were identified within the existing marina. Sedimentary heavy metal contents were found to be low, showing only slight heavy metal enrichment, attributed mainly to heavy mineral abundance in the area. A small enrichment for lead could be related to anthropogenic sources. Patterns of low concentrations were observed for organic carbon and organic nitrogen. Conversely, the sediment petroleum hydrocarbon content was found to be relatively high, implying anthropogenic pollution related to ship effluents and increased marine traffic.

scholarly journals Nové poznatky o terciéru a kvartéru získané geologickým mapováním okolí Lipníka nad Bečvou

2019 ◽  
Vol 26 (1-2) ◽  
Author(s):  
Miroslav Bubík ◽  
Helena Gilíková ◽  
Jiří Otava ◽  
Pavla Tomanová Petrová ◽  
Jan Vít
Keyword(s):  
Fresh Water ◽  
Bohemian Massif ◽  
Mineral Water ◽  
Early Pleistocene ◽  
Clastic Material ◽  
Quaternary Sediments ◽  
Fluvial Terrace ◽  
Fine Grained ◽  
Type Area ◽  
Carpathian Foredeep

Detail geological survey of the Lipník nad Bečvou surroundings brought new geological informations about the area, where Variscan and Carpathian orogens touch each other by their allochthonous nappe units. Detail mapping supported by micropaleontology enabled to fix the spatial extent of the nappe remnants of the Ždánice Unit in poorly exposed areas. Southeastern outskirts of Lipník nad Bečvou are part of the type area of the Menilite Formation defi ned by Glocker (1844) and one of his historical type localities near situated Símře was rediscovered. Lower Miocene strata were subdivided to the Stryszawa and Kroměříž formations based on the provenience of clastic material: Bohemian Massif for the Stryszawa Fm. and Carpathian nappes for the Kroměříž Fm. A new occurrence of rhyolitic fine-grained volcaniclastics was discovered in the Carpathian Foredeep in Lipník nad Bečvou. Quaternary sediments are represented, first of all, by complex fluvial terrace system of the Bečva River that illustrates the evolution of landscape since the latest Early Pleistocene. Remarkable local curiosity is fresh-water limestone (travertine) in Tučín, formed at the spring of thermal mineral water.

Early Holocene pinyon (Pinus monophylla) in the northeastern Great Basin

1990 ◽  
Vol 33 (1) ◽  
pp. 94-101 ◽  
Author(s):  
David B. Madsen ◽  
David Rhode
Keyword(s):  
Great Basin ◽  
Late Quaternary ◽  
Early Holocene ◽  
Hunter Gatherers ◽  
Pinus Monophylla ◽  
East Central ◽  
Lake Bonneville ◽  
Fine Grained ◽  
Pine Nut ◽  
Human Use

AbstractFine-grained excavation and analysis of a stratigraphic column from Danger Cave, northeastern Great Basin, suggests prehistoric hunter-gatherers were collecting and using singleleaf pinyon (Pinus monophylla) near the site for at least the last 7500 yr. Human use of the cave began after the retreat of Lake Bonneville from the Gilbert level, shortly before 10,000 yr B.P. In stratum 9, culturally deposited pine nut hulls appear in the sequence by about 7900 yr B.P. and are continuously present thereafter. A hull fragment in stratum 10 is directly dated to 7410 ± 120 yr B.P. These dates are at least 2000 yr earlier than expected by extrapolation to macrofossil records from the east-central and central Great Basin, and necessitate some revision of current biogeographical models of late Quaternary pinyon migration.

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