Evolution of trilobite biofacies in Cambrian basins of the Siberian Platform

2000 ◽  
Vol 74 (6) ◽  
pp. 1000-1019 ◽  
Author(s):  
Tatyana V. Pegel
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Siberian Platform ◽  
Global Scale ◽  
Depositional Environments ◽  
Sign Reversal ◽  
Middle Cambrian ◽  
Upper Cambrian ◽  
Sea Level Fluctuations ◽  
Stratigraphic Succession

Cambrian biotic zonation on the Siberian Platform reflects differentiation of the depositional environments (inner shelf, outer shelf and open basin). The combination of the chart of trilobite biofacies replacement and the curve of sea-level fluctuations shows that trilobite biofacies replacement occurs as a rule at times of sign reversal and distinct change in the rates of sea-level rise or fall. The boundaries of major Siberian platform Cambrian chronostratigraphic units, such a stages and series, frequently coincide with the boundaries of biofacies in stratigraphic succession related to sea-level fluctuations. If these fluctuations are gradual and restricted, then the boundaries of the Cambrian stages and series cannot be isochronous levels at a global scale. The known levels for intercontinental correlation on the Siberian Platform include boundaries of the adjacent Triplagnostus gibbus and Tomagnostus fissus Zones from the uppermost Amganian Stage (Middle Cambrian) and the Glyptagnostus stolidotus and Glyptagnostus reticulatus Zones of the lower Upper Cambrian. Both levels correspond to boundaries between highstands and lowstands on the Siberian Platform and appear to serve as boundaries of high rank. Evolution of the trilobite biofacies zonation is illustrated by genera typical for each of the various Cambrian paleogeographic environments on the Siberian Platform.

Cenomanian to Coniacian sea-level changes in the Lower Benue Trough (Nkalagu Area, Nigeria) and the Eastern Dahomey Basin: palaeontological and sedimentological evidence for eustasy and tectonism

2019 ◽  
Vol 498 (1) ◽  
pp. 233-255 ◽  
Author(s):  
Holger Gebhardt ◽  
Samuel O. Akande ◽  
Olabisi A. Adekeye
Keyword(s):  
Sea Level ◽  
Deep Water ◽  
Close Relation ◽  
Depositional Environments ◽  
Sea Level Changes ◽  
Foraminiferal Assemblage ◽  
Benue Trough ◽  
Sea Level Fluctuations ◽  
Dahomey Basin ◽  
Lower Benue Trough

AbstractThe Benue Trough formed in close relation to the opening of the South Atlantic and experienced sea-level fluctuations of different magnitudes during the Cenomanian to Coniacian interval. We identify depositional environments from outcrop sections and a drilling as control record. Lines of evidence for the interpretation include facies analyses, foraminiferal assemblage composition (P/B-ratio) and the presence of planktonic deep-water indicators. While the analysis of the well data from the Dahomey Basin indicates a continuous deep-water (bathyal) environment, the succession in the Nkalagu area of the Lower Benue Trough evolved in a different and more complex way. Beginning with latest Cenomanian shoreface to shelf deposits, a long period of subsidence lasted until the middle Turonian when pelagic shales and calcareous turbidites were deposited at upper to middle bathyal depths. These conditions continued during late Turonian and Coniacian times. The general deepening trend of the Lower Benue Trough was mainly controlled by tectonic subsidence and was superimposed by eustatic sea-level changes, resulting in periodically changing palaeowater depths. We were able to identify eight sea-level rises and falls that can be attributed to 405 kyr eccentricity cycles. The amplitudes of the sea-level changes were most likely in the range of several tens to a few hundred metres. The deposition of carbonate turbidites at Nkalagu was probably triggered by eustatic sea-level lowstands.

Facies anatomy of an Upper Cambrian grand cycle: Bison Creek and Mistaya formations, southern Alberta

1989 ◽  
Vol 26 (11) ◽  
pp. 2292-2304 ◽  
Author(s):  
Stephen R. Westrop
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
National Parks ◽  
Carbonate Platform ◽  
Half Cycle ◽  
Upper Cambrian ◽  
Facies Associations ◽  
Southern Alberta ◽  
Shallow Subtidal ◽  
Carbonate Bank

The Bison Creek and Mistaya formations form the youngest Cambrian sedimentary grand cycle exposed in Banff and Jasper national parks. The shaly half-cycle of the Bison Creek Formation records the displacement of a carbonate bank during a major rise in sea level that can be identified in other parts of North America. Lithofacies of the Bison Creek Formation fall into three recurrent associations that represent sedimentation in shallow, subtidal, storm-dominated shelf settings. The Mistaya Formation records the reestablishment of carbonate bank deposition, probably due to a decrease in the rate of sea-level rise, and includes two facies associations that represent a mosaic of shallow subtidal to supratidal environments. The grand cycle was terminated by a sea-level rise, possibly eustatic in nature, that drowned the carbonate platform. The overlying shales, mudstones, packstones, grainstones, and rudstones of the Survey Peak Formation mark a return to subtidal, storm-dominated shelf conditions.

Volume–area scaling parameterisation of Norwegian ice caps: A comparison of different approaches

The Holocene ◽  
2016 ◽  
Vol 27 (1) ◽  
pp. 164-171 ◽  
Author(s):  
Tron Laumann ◽  
Atle Nesje
Keyword(s):  
Water Resources ◽  
Sea Level Rise ◽  
Sea Level ◽  
Sea Level Change ◽  
Global Scale ◽  
Two Dimensional ◽  
Ice Caps ◽  
Level Change ◽  
Global Sea Level ◽  
Best Fit

Over the recent decades, glaciers have in general continued to lose mass, causing surface lowering, volume reduction and frontal retreat, thus contributing to global sea-level rise. When making assessments of present and future sea-level change and management of water resources in glaciated catchments, precise estimates of glacier volume are important. The glacier volume cannot be measured on every single glacier. Therefore, the global glacier volume must be estimated from models or scaling approaches. Volume–area scaling is mostly applied for estimating volumes of glaciers and ice caps on a regional and global scale by using a statistical–theoretical relationship between glacier volume ( V) and area ( A) ( V =  cAγ) (for explanation of the parameters c and γ, see Eq. 1). In this paper, a two-dimensional (2D) glacier model has been applied on four Norwegian ice caps (Hardangerjøkulen, Nordre Folgefonna, Spørteggbreen and Vestre Svartisen) in order to obtain values for the volume–area relationship on ice caps. The curve obtained for valley glaciers gives the best fit to the smallest plateau glaciers when c = 0.027 km3−2 γ and γ = 1.375, and a slightly poorer fit when the glacier increases in size. For ice caps, c = 0.056 km3−2 γ and γ = 1.25 fit reasonably well for the largest, but yield less fit to the smaller.

Smithian shoreline migrations and depositional settings in Timpoweap Canyon (Early Triassic, Utah, USA)

2014 ◽  
Vol 151 (5) ◽  
pp. 938-955 ◽  
Author(s):  
NICOLAS OLIVIER ◽  
ARNAUD BRAYARD ◽  
EMMANUEL FARA ◽  
KEVIN G. BYLUND ◽  
JAMES F. JENKS ◽  
...  
Keyword(s):  
Sea Level ◽  
High Frequency ◽  
Depositional Environments ◽  
Small Scale ◽  
Early Triassic ◽  
Relative Sea Level ◽  
Depositional Sequence ◽  
Sea Level Fluctuations ◽  
Stacking Pattern ◽  
Shallow Subtidal

AbstractIn Timpoweap Canyon near Hurricane (Utah, USA), spectacular outcrop conditions of Early Triassic rocks document the geometric relationships between a massive Smithian fenestral-microbial unit and underlying, lateral and overlying sedimentary units. This allows us to reconstruct the evolution of depositional environments and high-frequency relative sea-level fluctuations in the studied area. Depositional environments evolved from a coastal plain with continental deposits to peritidal settings with fenestral-microbial limestones, which are overlain by intertidal to shallow subtidal marine bioclastic limestones. This transgressive trend of a large-scale depositional sequence marks a long-term sea-level rise that is identified worldwide after the Permian–Triassic boundary. The fenestral-microbial sediments were deposited at the transition between continental settings (with terrigenous deposits) and shallow subtidal marine environments (with bioturbated and bioclastic limestones). Such a lateral zonation questions the interpretation of microbial deposits as anachronistic and disaster facies in the western USA basin. The depositional setting may have triggered the distribution of microbial deposits and contemporaneous marine biota. The fenestral-microbial unit is truncated by an erosional surface reflecting a drop in relative sea level at the scale of a medium depositional sequence. The local inherited topography allowed the recording of small-scale sequences characterized by clinoforms and short-distance lateral facies changes. Stratal stacking pattern and surface geometries allow the reconstruction of relative sea-level fluctuations and tracking of shoreline migrations. The stacking pattern of these small-scale sequences and the amplitude of corresponding high-frequency sea-level fluctuations are consistent with climatic control. Large- and medium-scale sequences suggest a regional tectonic control.

Spatio-temporal decomposition of geophysical signals in North America

2020 ◽  
Author(s):  
Aoibheann Brady ◽  
Jonathan Rougier ◽  
Bramha Dutt Vishwakarma ◽  
Yann Ziegler ◽  
Richard Westaway ◽  
...  
Keyword(s):  
North America ◽  
Sea Level Rise ◽  
Sea Level ◽  
Global Scale ◽  
Bayesian Hierarchical ◽  
Isostatic Adjustment ◽  
Modelling Framework ◽  
Vertical Land Motion ◽  
Early Results ◽  
Spatio Temporal

<p>Sea level rise is one of the most significant consequences of projected future changes in climate. One factor which influences sea level rise is vertical land motion (VLM) due to glacial isostatic adjustment (GIA), which changes the elevation of the ocean floor. Typically, GIA forward models are used for this purpose, but these are known to vary with the assumptions made about ice loading history and Earth structure. In this study, we implement a Bayesian hierarchical modelling framework to explore a data-driven VLM solution for North America, with the aim of separating out the overall signal into its GIA and hydrology (mass change) components. A Bayesian spatio-temporal model is implemented in INLA using satellite (GRACE) and in-situ (GPS) data as observations. Under the assumption that GIA varies in space but is constant in time, and that hydrology is both spatially- and temporally-variable, it is possible to separate the contributions of each component with an associated uncertainty level. Early results will be presented. Extensions to the BHM framework to investigate sea level rise at the global scale, such as the inclusion of additional processes and incorporation of increased volumes of data, will be discussed.</p>

Biogeographic shifts in a transgressive succession: the Cambrian (Furongian, Jiangshanian; Latest Steptoean–earliest Sunwaptan) agnostoid arthropodsKormagnostellaRomanenko andBiciragnostusErgaliev in North America

2013 ◽  
Vol 87 (5) ◽  
pp. 804-817 ◽  
Author(s):  
Stephen R. Westrop ◽  
Jonathan M. Adrain
Keyword(s):  
New Species ◽  
North America ◽  
Sea Level Rise ◽  
Sea Level ◽  
Local Extinction ◽  
Faunal Turnover ◽  
Upper Cambrian ◽  
Extinction Event ◽  
Stratigraphic Interval

The first records of the upper Cambrian agnostoid generaKormagnostella, E. Romanenko,inRomanenko and Romanenko, 1967, andBiciragnostusF. Ergaliev,inEraliev and Ergaliev, 2001, in Laurentian North America are from a narrow stratigraphic interval in the Steptoean–Sunwaptan boundary interval (Furongian, Jiangshanian) of Nevada and Utah. In Nevada, both genera occur in a condensed bioclastic lag below a major flooding surface, andKormagnostellaalso appears in a transgressive interval in Utah. Immigration of these genera is associated with sea level rise, and also with faunal turnover.Biciragnostusis confined to the latestElviniaZone, immediately below the onset of a trilobite and agnostoid extinction event at the base of theIrvingella majorZone (basal Sunwaptan).Kormagnostellais present in the latestElviniaZone, and has its highest occurrence in theI. majorZone. Stratigraphic data from the Karatau-Naryn Terrane, Kazakhstan indicate that both genera disappear near the local extinction ofIrvingella, suggesting that faunal turnover in that region may have been broadly correlative with the more profound extinction in Laurentia. New species areKormagnostella advena,K. insolitaandBiciragnostus viator.

Impacts and responses to sea-level rise: a global analysis of the SRES scenarios over the twenty-first century

2006 ◽  
Vol 364 (1841) ◽  
pp. 1073-1095 ◽  
Author(s):  
Robert J Nicholls ◽  
Richard S.J Tol
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Global Analysis ◽  
Cost Benefit ◽  
Atmospheric Temperature ◽  
Global Scale ◽  
First Century ◽  
Twenty First Century ◽  
Sres Scenarios ◽  
The Impact

Taking the Special Report on Emission Scenarios (SRES) climate and socio-economic scenarios (A1FI, A2, B1 and B2 ‘future worlds’), the potential impacts of sea-level rise through the twenty-first century are explored using complementary impact and economic analysis methods at the global scale. These methods have never been explored together previously. In all scenarios, the exposure and hence the impact potential due to increased flooding by sea-level rise increases significantly compared to the base year (1990). While mitigation reduces impacts, due to the lagged response of sea-level rise to atmospheric temperature rise, impacts cannot be avoided during the twenty-first century by this response alone. Cost–benefit analyses suggest that widespread protection will be an economically rational response to land loss due to sea-level rise in the four SRES futures that are considered. The most vulnerable future worlds to sea-level rise appear to be the A2 and B2 scenarios, which primarily reflects differences in the socio-economic situation (coastal population, Gross Domestic Product (GDP) and GDP/capita), rather than the magnitude of sea-level rise. Small islands and deltaic settings stand out as being more vulnerable as shown in many earlier analyses. Collectively, these results suggest that human societies will have more choice in how they respond to sea-level rise than is often assumed. However, this conclusion needs to be tempered by recognition that we still do not understand these choices and significant impacts remain possible. Future worlds which experience larger rises in sea-level than considered here (above 35 cm), more extreme events, a reactive rather than proactive approach to adaptation, and where GDP growth is slower or more unequal than in the SRES futures remain a concern. There is considerable scope for further research to better understand these diverse issues.

scholarly journals The Bakken Formation - understanding the sequence stratigraphic record of low-gradient sedimentary systems, shale depositional environments, and sea-level changes in an icehouse world

2020 ◽  
Vol 18 (4) ◽  
pp. 4-9
Author(s):  
Sven O Egenhoff ◽  
Neil S Fishman
Keyword(s):  
Sea Level ◽  
High Amplitude ◽  
Depositional Environments ◽  
Ice Age ◽  
Bakken Formation ◽  
Sea Level Changes ◽  
Sequence Stratigraphic ◽  
Sea Level Fluctuations ◽  
Layer Cake ◽  
Low Amplitude

The Bakken Formation is a major petroleum producer in the continental US. However, its deposition in an intracratonic, low-gradient setting has often been mistakenly described as “layer-cake”. This contribution is designed to highlight the time-transgressive nature of its main petroleum-producer, the middle Bakken member. Correlation of individual parasequences reveal the subtle nature of otherwise invisible low-angle stratigraphic geometries. Sequence stratigraphically-relevant surfaces occur throughout the unit and subdivide the entire Bakken into 5 third-order sequences; one of them is a hidden sequence at the base of the petroleum-producing middle Bakken indicating both a lowstand and a subsequent transgression. The organic-rich shales above and below the middle Bakken were deposited in an oxygen-deficient environment and show several burrow/fecal string types and indications of active currents during deposition. The Bakken records high amplitude sea-level changes during sequences compared to relative low amplitude sea-level changes of parasequences. This, coupled with a likely mismatch in timing of Bakken deposition relative to world-wide ice-age-induced cyclicity makes it unlikely that the Bakken sea-level fluctuations were dominated by glaciation.

scholarly journals Sequestering seawater on land: a water-based solution to global issues

F1000Research ◽  
2017 ◽  
Vol 5 ◽  
pp. 889
Author(s):  
Stéphane Boyer ◽  
Marie-Caroline Lefort
Keyword(s):  
Climate Change ◽  
Sea Level Rise ◽  
Sea Level ◽  
Biodiversity Loss ◽  
Global Scale ◽  
Water Desalination ◽  
Global Issues ◽  
Excess Water ◽  
Desalination Plants ◽  
The Cost

The ‘surplus’ of oceanic water generated by climate change offers an unprecedented opportunity to tackle a number of global issues through a very pragmatic process: shifting the excess water from the oceans onto the land. Here we propose that sea-level rise could be mitigated through the desalination of very large amounts of seawater in an international network of massive desalination plants. To efficiently mitigate sea-level rise, desalinized water could be stored on land in the form of crop, wetlands or new forests. Based on a US$ 500 million price to build an individual mega desalination plant with current technology, the cost of controlling current sea-level rise through water desalination approaches US$ 23 trillion in investment and US$ 4 trillion per year in operating costs. However, the economic, environmental and health benefits would also be immense and could contribute to addressing a number of global issues including sea-level rise, food security, biodiversity loss and climate change. Because these issues are intimately intertwined, responses should aim at addressing them all concurrently and at global scale.

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