scholarly journals Hyperpycnites within the Devonian-Carboniferous flysch of the Carpatho-Balkanides (Kostadinovica, eastern Serbia)

2020 ◽  
Vol 73 (3) ◽  
pp. 131-142
Author(s):  
Miloš Radonjić ◽  
Keyword(s):  
Marine Environment ◽  
Relative Abundance ◽  
Vascular Plants ◽  
Early Carboniferous ◽  
Fossil Plants ◽  
Plant Debris ◽  
Material Support ◽  
Fossil Material ◽  
Proposed Model ◽  
Depositional Setting

This study presents new discoveries of vascular plants and the trace fossil Dictyodora liebeana (GEINITZ) from the Devonian–Carboniferous Kučaj-Zvonce flysch of the Carpatho-Balkanides and the implications of this fossil association for its sedimentary setting. The occurrence of the described plant debris in a deep-marine environment indicates the presence of hyperpycnites within the siliciclastic turbidites exposed at the Kostadinovica locality. The sedimentological data and the characteristics of the fossil material support the proposed model in which the sediment was at least partially transported by hyperpycnite currents. Furthermore, based on the assessment to similar palaeofloras from comparable formations, the age of the fossil plants can be determined as Early Carboniferous. This can be used as an additional biostratigraphic criterion given the relative abundance of vascular plants in other localities of the Kučaj-Zvonce flysch described in previous studies. The age and the depositional setting of the succession is further better constrained by the first observation of Dictyodora liebeana (GEINITZ) in the Carpatho-Balkanides of Serbia.

Implications for the age of South African Devonian rocks in which Tropidoleptus (Brachiopoda) has been found

1983 ◽  
Vol 120 (1) ◽  
pp. 51-58 ◽  
Author(s):  
A. J. Boucot ◽  
C. H. C. Brunton ◽  
J. N. Theron
Keyword(s):  
South Africa ◽  
North America ◽  
South African ◽  
Early Carboniferous ◽  
Fossil Plants ◽  
Geological Time ◽  
Marine Sedimentation ◽  
History Of ◽  
Near Shore ◽  
First Time

SummaryThe Devonian brachiopod Tropidoleptus is recognized for the first time in South Africa. It is present in the lower part of the Witteberg Group at four widely separated localities. Data regarding the stratigraphical range of the genus elsewhere, combined with information on recently described fossil plants and vertebrates from underlying strata of the upper Bokkeveld Group, suggest that a Frasnian or even Givetian age is reasonable for the lower part of the Witteberg Group. The recognition of Tropidoleptus in a shallow water, near-shore, molluscan association, at the top of the South African marine Devonian sequence, is similar to its occurrence in Bolivia, and suggests a common Malvinokaffric Realm history of shallowing, prior to later Devonian or early Carboniferous non-marine sedimentation. It is noteworthy that Tropidoleptus is now known to occur in ecologically suitable environments around the Atlantic, but is absent from these same environments in Asia and Australia. Tropidoleptus is an excellent example of dispersal in geological time — first appearing in northern Europe and Nova Scotia, then elsewhere in eastern North America and North Africa, followed by South America and South Africa, while continuing in North America.

scholarly journals Nonlinear Dynamic Characteristic Analysis of a Landing String in Deepwater Riserless Drilling

2018 ◽  
Vol 2018 ◽  
pp. 1-17
Author(s):  
Jun Liu ◽  
Hongliang Zhao ◽  
Simon X. Yang ◽  
Qingyou Liu ◽  
Guorong Wang
Keyword(s):  
Boundary Condition ◽  
Dynamic Model ◽  
Marine Environment ◽  
Lower Boundary ◽  
Dynamic Responses ◽  
Characteristic Analysis ◽  
Lower Boundary Condition ◽  
Response Characteristics ◽  
Proposed Model ◽  
Nonlinear Dynamic Characteristic

The landing string is an important component of deepwater riserless drilling systems. Determination of the dynamic characteristics of the landing string plays an essential role in its design for ensuring its safe operation. In this paper, a dynamic model is developed to investigate the dynamic response characteristics of a landing string, where a landing string in a marine environment is modeled as a flexible slender tube undergoing coupled transverse and axial motions. The heaving motion of the drilling platform is taken as the upper boundary condition and the motion of the drilling bit caused by the interaction between the rock and the bit as the lower boundary condition. A semiempirical Morison equation is used to simulate the effect of the load imposed by the marine environment. The dynamic model, which is nonlinearly coupled and multibody, is discretized by a finite element method and solved by the Newmark technique. Using the proposed model, the dynamic responses of the displacement, axial force, and moment in the landing string are investigated in detail to find out the influences of driving depth of surface catheter, platform motion, bit movement, and marine environment on the dynamical characteristics of the landing string.

scholarly journals Three-dimensional visualization of fossil flowers, fruits, seeds, and other plant remains using synchrotron radiation X-ray tomographic microscopy (SRXTM): new insights into Cretaceous plant diversity

2014 ◽  
Vol 88 (4) ◽  
pp. 684-701 ◽  
Author(s):  
Else Marie Friis ◽  
Federica Marone ◽  
Kaj Raunsgaard Pedersen ◽  
Peter R. Crane ◽  
Marco Stampanoni
Keyword(s):  
Synchrotron Radiation ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Fossil Plants ◽  
Post Processing ◽  
Thin Sections ◽  
X Ray ◽  
Rapid Acquisition ◽  
Fossil Material ◽  
Plant Fossil

The application of synchrotron radiation X-ray tomographic microscopy (SRXTM) to the study of mesofossils of Cretaceous age has created new possibilities for the three-dimensional visualization and analysis of the external and internal structure of critical plant fossil material. SRXTM provides cellular and subcellular resolution of comparable or higher quality to that obtained from permineralized material using thin sections or the peel technique. SRXTM also has the advantage of being non-destructive and results in the rapid acquisition of large quantities of data in digital form. SRXTM thus refocuses the effort of the investigator from physical preparation to the digital post-processing of X-ray tomographic data, which allows great flexibility in the reconstruction, visualization, and analysis of the internal and external structure of fossil material in multiple planes and in two or three dimensions. A review of recent applications in paleobotany demonstrates that SRXTM will dramatically expand the level of information available for diverse fossil plants. Future refinement of SRXTM approaches that further increases resolution and eases digital post-processing, will transform the study of mesofossils and create new possibilities for advancing paleobotanical knowledge. We illustrate these points using a variety of Cretaceous mesofossils, highlighting in particular those cases where SRXTM has been essential for resolving critical structural details that have enhanced systematic understanding and improved phylogenetic interpretations.

scholarly journals The carbon cycle and carbon dioxide over Phanerozoic time: the role of land plants

1998 ◽  
Vol 353 (1365) ◽  
pp. 75-82 ◽  
Author(s):  
Robert A. Berner
Keyword(s):  
Organic Matter ◽  
Carbon Cycle ◽  
Vascular Plants ◽  
Global Climate ◽  
Carbon Isotopic Composition ◽  
Field Studies ◽  
Accelerated Weathering ◽  
Fossil Plants ◽  
Factors Affecting ◽  
Carbon Isotopic

A model (GEOCARB) of the long–term, or multimillion year, carbon cycle has been constructed which includes quantitative treatment of (1) uptake of atmospheric CO 2 by the weathering of silicate and carbonate rocks on the continents, and the deposition of carbonate minerals and organic matter in oceanic sediments; and (2) the release of CO 2 to the atmosphere via the weathering of kerogen in sedimentary rocks and degassing resulting from the volcanic–metamorphic–diagenetic breakdown of carbonates and organic matter at depth. Sensitivity analysis indicates that an important factor affecting CO 2 was the rise of vascular plants in the Palaeozoic. A large Devonian drop in CO 2 was brought about primarily by the acceleration of weathering of silicate rock by the development of deeply rooted plants in well–drained upland soils. The quantitative effect of this accelerated weathering has been crudely estimated by present–day field studies where all factors affecting weathering, other than the presence or absence of vascular plants, have been held relatively constant. An important additional factor, bringing about a further CO 2 drop into the Carboniferous and Permian, was enhanced burial of organic matter in sediments, due probably to the production of microbially resistant plant remains (e.g. lignin). Phanerozoic palaeolevels of atmospheric CO 2 calculated from the GEOCARB model generally agree with independent estimates based on measurements of the carbon isotopic composition of palaeosols and the stomatal index for fossil plants. Correlation of CO 2 levels with estimates of palaeoclimate suggests that the atmospheric greenhouse effect has been a major factor in controlling global climate over the past 600 million years.

A tale of two peats: characterizing ecosystem-driven differences in chemical composition with depth in natural and drained Finnish mires using Py-GC/MS analytical techniques

2020 ◽  
Author(s):  
Kristy Klein ◽  
Miriam Groβ-Schmölders ◽  
Christine Alewell ◽  
Jens Leifeld
Keyword(s):  
Chemical Composition ◽  
Water Table ◽  
Relative Abundance ◽  
Vascular Plants ◽  
Carbon Sink ◽  
Molecular Biomarkers ◽  
Gas Chromatography Mass Spectrometry ◽  
Driving Mechanism ◽  
Aerobic Decomposition ◽  
Relative Abundances

<p>Intact accumulating peatlands are a globally important terrestrial carbon sink. Climate change and agricultural drainage are degrading these ecosystems, and through increases in aerobic decomposition, shifting their C balance from sink to source. To argue the effectiveness of restoration activities (such as rewetting), techniques are needed that clearly show differences between drained and natural (or drained and rewetted) peatlands. Because these changes are not always macroscopically visible, molecular analysis methods are especially needed to distinguish between ecosystems experiencing net pet growth (sequestering carbon), and those where aerobic decomposition is still a primary driving mechanism. Molecular biomarkers are a useful way to use chemical composition to distinguish these mechanisms.</p><p>This study aimed to compare differences in chemical composition with depth between two peatland sites from a large ombrotrophic mire in Lakkasuo Finland – one natural and one drained. To characterize these chemical shifts, pyrolysis gas chromatography mass spectrometry was used to track changes in relative abundance of various molecular biomarkers and compound classes (ie., aromatics, Sphagnum phenols, lignin, N-containing compounds, n-alkanes, etc.) with depth across both sites. Three replicate cores per site were collected, allowing for statistical evaluation of the relative abundances of these compounds. Using radiocarbon dating at three depths per core, the drained and natural sites were also matched by age for reference purposes. Significant differences were found for the Sphagnum-specific biomarker, p-isopropenylphenol, aromatics, and lignin, to the approximate current depth of the drained peatland water table. Higher phenolic compound class abundance indicated inhibited aerobic decomposition in the natural cores. An increasing trend in lignin biomarker relative abundance with depth was observed in the natural site, despite the identification of comparatively fewer vascular plants during the macroscopic analysis. Rather than a higher abundance of palaeo-ecological vascular plants, this trend is considered to be an indicator of preferential preservation of lignin compounds with anaerobic conditions. Below the depth of the water table, the relative abundances of most biomarkers stabilized, indicating the existance of similar environmental conditions in both sites prior to drainage. These data were compared and are in agreement with findings from elemental analysis (CHNO) and bulk isotopic (<sup>13</sup>C and <sup>15</sup>N) data measured on the same cores. Collectively, these data suggest that observed shifts in chemical composition in the natural and drained cores reflect the effect of different hydrological conditions between the two sites.</p>

Vascular plants from the Devonian to Lower Cretaceous in southern Africa

Bothalia ◽  
1983 ◽  
Vol 14 (3/4) ◽  
pp. 337-344 ◽  
Author(s):  
J. M. Anderson ◽  
H. M. Anderson
Keyword(s):  
Species Diversity ◽  
Relative Abundance ◽  
Southern Africa ◽  
Lower Cretaceous ◽  
Vascular Plants ◽  
Floral Development ◽  
Continental Drift ◽  
Upper Triassic ◽  
Climatic Trends ◽  
Faunal Evolution

The succession of pre-angiospermous megafloras in southern Africa from the Devonian to Lower Cretaceous is outlined. Interrelationships between continental drift, global climatic trends, and floral and faunal evolution are emphasized. Data are given on numbers of assemblages sampled; on species diversity; and on relative abundance of each genus per productive ‘formation’. A total of 79 genera and about 250 species are recognized in the 150 assemblages from the 11 horizons considered. Floras are unknown from the Carboniferous and are as yet undescribed from the Jurassic. Aside from these gaps, a good idea of the floral development is obtained. Diversity lows of around 5 to 10 species per ‘formation’ are witnessed in the Devonian, whereas a peak of 112 species is encountered in the Upper Triassic Molteno Formation. Diversity remains around 20 to 30 species for all other ‘formations’.

Research on Modeling and Simulation of Sonar Performance Using Simulink

2011 ◽  
Vol 138-139 ◽  
pp. 804-809
Author(s):  
Ke Hua Li ◽  
Jin Yong Yu ◽  
Jun Wei Lei
Keyword(s):  
Mathematical Models ◽  
Modeling And Simulation ◽  
Target Detection ◽  
Marine Environment ◽  
Acoustic Model ◽  
Acoustic Characteristics ◽  
Proposed Model ◽  
Environment Simulation ◽  
Simulation Results ◽  
Ocean Environment

With respect to different weather and sea conditions, the acoustic model under ocean environment was proposed by analyzing the interaction characteristics between sonar and environment. Based on the sonar equation, the performance mathematical models of active and passive sonar were produced with considering acoustic characteristics of the target and parameters of the marine environment. Simulation results of target detection performance for different target types, sonar parameters and sea conditions show the validity of the proposed model.

Upper Silurian trilete spores and other microfossils from the Read Bay Formation, Cornwallis Island, Canadian Arctic

1978 ◽  
Vol 15 (8) ◽  
pp. 1292-1303 ◽  
Author(s):  
D. C. McGregor ◽  
G. M. Narbonne
Keyword(s):  
New Species ◽  
Marine Environment ◽  
Vascular Plants ◽  
Canadian Arctic ◽  
Type Section ◽  
Stratigraphic Framework ◽  
Near Shore ◽  
Upper Silurian ◽  
One New Species ◽  
Cornwallis Island

A diverse palynomorph assemblage of trilete spores, tetrads, acritarchs, chitinozoans, scolecodonts, and fragments of arthropods, ?hydrozoans, ?graptolites, and possibly nematophytalean and vascular plants occurs 20 m above the base of member B of the Read Bay Formation at the type section on eastern Cornwallis Island, District of Franklin. This assemblage, here described briefly, is late Ludlow according to faunas above and below. The palynomorphs, other fossils, and stratigraphic framework indicate that the shales of member B were deposited in a sheltered near-shore marine environment. One new species of trilete spores, Retusotriletes chartulatus McGregor, is erected.

scholarly journals 1980s population-specific compositions of two related anadromous shad species during the oceanic phase determined by microchemistry of archived otoliths

2020 ◽  
Vol 77 (1) ◽  
pp. 164-176 ◽  
Author(s):  
David José Nachón ◽  
Gilles Bareille ◽  
Hilaire Drouineau ◽  
Hélène Tabouret ◽  
Catherine Taverny ◽  
...  
Keyword(s):  
Marine Environment ◽  
Relative Abundance ◽  
Bayesian Model ◽  
Otolith Microchemistry ◽  
Anadromous Fish ◽  
Metapopulation Dynamics ◽  
Natal Origin ◽  
Alosa Alosa ◽  
Specific Composition ◽  
Alosa Fallax

The specific stock composition and dispersion of anadromous fish species aggregations in the marine environment are poorly known, while they can play a major role in the metapopulation dynamics. Otolith microchemistry has proven to be a powerful tool to address natal origins of anadromous fish. We used archived otolith microchemistry to investigate the population-specific composition of subadult European shads (Alosa alosa and Alosa fallax) in the ocean during the 1980s. The allocation of natal origin was addressed relying on contemporary water and juveniles’ signatures within a Bayesian model. A great discrimination of natal origin was obtained at the Biscay Gulf scale. However, the discrimination of 1980s natal origin for the southern rivers with similar geology based on 2013 water and juveniles’ baselines was doubtful. Our results showed that the most abundant southern populations were dominant, suggesting that population-specific composition was related to population relative abundance. The dispersion in the marine environment was plastic; alternatively, shads were found large distances away from their natal rivers, while others remained in the vicinity of their natal river plume.

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