Tubey or not tubey: Death beds of Ediacaran macrofossils or microbially induced sedimentary structures?

Geology ◽  
2019 ◽  
Vol 47 (10) ◽  
pp. 909-913
Author(s):  
Lyle L. Nelson ◽  
Emily F. Smith
Keyword(s):  
Environmental Conditions ◽  
Trace Fossils ◽  
Microbial Mat ◽  
Sedimentary Structures ◽  
Bedding Planes ◽  
Stratigraphic Interval

Abstract Within the upper Ediacaran Esmeralda Member of the Deep Spring Formation in southeastern California, USA, an ∼3 m stratigraphic interval contains multiple clastic bedding surfaces with enigmatic, three-dimensionally preserved corrugated tubes (<60 cm in length and 6 cm in width). When viewed as fragments and in situ on bedding planes, these resemble larger versions of annulated, tubular soft-bodied macrofossils that are common in late Ediacaran biotic assemblages regionally and globally. Despite superficial similarities to casts and molds of body fossils preserved in correlative strata, we suggest these tubes are instead previously undescribed organosedimentary structures that developed through differential compaction of rippled heterolithic interbeds bound by pyritized microbial mat layers. These distinctive structures formed within peritidal settings in the latest Ediacaran Period as the result of specific ecological and environmental conditions marked by flourishing microbial mat communities and dysoxic sediments. This interpretation may inform the biogenicity of other structures previously reported as macroscopic body or trace fossils.

MixAR

2019 ◽  
Vol 12 (4) ◽  
pp. 1-33 ◽  
Author(s):  
Telmo Adão ◽  
Luís Pádua ◽  
David Narciso ◽  
Joaquim João Sousa ◽  
Luís Agrellos ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Mixed Reality ◽  
The Real ◽  
Points Of Interest ◽  
Real Scene ◽  
The Future

MixAR, a full-stack system capable of providing visualization of virtual reconstructions seamlessly integrated in the real scene (e.g. upon ruins), with the possibility of being freely explored by visitors, in situ, is presented in this article. In addition to its ability to operate with several tracking approaches to be able to deal with a wide variety of environmental conditions, MixAR system also implements an extended environment feature that provides visitors with an insight on surrounding points-of-interest for visitation during mixed reality experiences (positional rough tracking). A procedural modelling tool mainstreams augmentation models production. Tests carried out with participants to ascertain comfort, satisfaction and presence/immersion based on an in-field MR experience and respective results are also presented. Ease to adapt to the experience, desire to see the system in museums and a raised curiosity and motivation contributed as positive points for evaluation. In what regards to sickness and comfort, the lowest number of complaints seems to be satisfactory. Models' illumination/re-lightning must be addressed in the future to improve the user's engagement with the experiences provided by the MixAR system.

scholarly journals In-Situ Metatranscriptomic Analyses Reveal the Metabolic Flexibility of the Thermophilic Anoxygenic Photosynthetic Bacterium Chloroflexusaggregans in a Hot Spring Cyanobacteria-Dominated Microbial Mat

2021 ◽  
Vol 9 (3) ◽  
pp. 652
Author(s):  
Shigeru Kawai ◽  
Joval N. Martinez ◽  
Mads Lichtenberg ◽  
Erik Trampe ◽  
Michael Kühl ◽  
...  
Keyword(s):  
Energy Metabolism ◽  
Environmental Conditions ◽  
Microbial Mats ◽  
Carbon Fixation ◽  
Hot Springs ◽  
Hot Spring ◽  
Photosynthetic Bacterium ◽  
Early Morning ◽  
Metabolic Flexibility

Chloroflexus aggregans is a metabolically versatile, thermophilic, anoxygenic phototrophic member of the phylum Chloroflexota (formerly Chloroflexi), which can grow photoheterotrophically, photoautotrophically, chemoheterotrophically, and chemoautotrophically. In hot spring-associated microbial mats, C. aggregans co-exists with oxygenic cyanobacteria under dynamic micro-environmental conditions. To elucidate the predominant growth modes of C. aggregans, relative transcription levels of energy metabolism- and CO2 fixation-related genes were studied in Nakabusa Hot Springs microbial mats over a diel cycle and correlated with microscale in situ measurements of O2 and light. Metatranscriptomic analyses indicated two periods with different modes of energy metabolism of C. aggregans: (1) phototrophy around midday and (2) chemotrophy in the early morning hours. During midday, C. aggregans mainly employed photoheterotrophy when the microbial mats were hyperoxic (400–800 µmol L−1 O2). In the early morning hours, relative transcription peaks of genes encoding uptake hydrogenase, key enzymes for carbon fixation, respiratory complexes as well as enzymes for TCA cycle and acetate uptake suggest an aerobic chemomixotrophic lifestyle. This is the first in situ study of the versatile energy metabolism of C. aggregans based on gene transcription patterns. The results provide novel insights into the metabolic flexibility of these filamentous anoxygenic phototrophs that thrive under dynamic environmental conditions.

A New and Open CoiledValvata(Gastropoda) from the Pliocene Koobi Fora Formation of the Turkana Basin, Northern Kenya

2010 ◽  
Vol 84 (5) ◽  
pp. 996-1002 ◽  
Author(s):  
Henning Scholz ◽  
Matthias Glaubrecht
Keyword(s):  
New Species ◽  
Environmental Stress ◽  
Environmental Conditions ◽  
Lake Level ◽  
Shell Morphology ◽  
Koobi Fora ◽  
Northern Kenya ◽  
Turkana Basin ◽  
High Level ◽  
Stratigraphic Interval

New field collections allow the study and description ofValvata juliaenew species from the Pliocene upper Burgi Member of the Koobi Fora Formation of Kenya. The shell morphology of this species varies from trochospiral to planispiral to open coiled. The species is restricted to a short stratigraphic interval.Valvata juliaeis considered as an invader of the Turkana Basin during a lacustrine transgression event. The open coiling of the species is interpreted as an ecophenotypic response to a high level of environmental stress caused by lake level fluctuations and emergence of delta systems. These environmental conditions broughtValvata juliaeto extinction soon after it invaded the Turkana Basin.

scholarly journals Transplantation of the Mediterranean seagrass Posidonia oceanica through naturalistic engineering techniques: value, weakness and further improvements

2015 ◽  
Author(s):  
Stefano Acunto ◽  
Luigi Piazzi ◽  
Francesco L. Cinelli ◽  
Anna Maria De Biasi ◽  
Lorenzo Pacciardi ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Large Scale ◽  
Focal Point ◽  
Posidonia Oceanica ◽  
Hydrodynamic Conditions ◽  
Coastal System ◽  
Pros And Cons ◽  
The Mediterranean ◽  
Selection Of

Transplantation of seagrasses is considered a useful method to favour the recovery of degraded meadows. Hence, many projects have been carried out worldwide and a manifold of techniques have been applied. However, the choice of transplantation procedures remains a main problem to be assessed. In order to optimize efforts and to minimize risks of plants loss, the applied methodologies should take into account typology of hosting substratum, hydrodynamic conditions, depth and seagrass species. Due to their fundamental ecological role in the Mediterranean coastal system, many restoration projects aiming to preserve Posidonia oceanica meadows took place in the last decades. Several transplantation techniques have produced different results. In fact the same transplanting methodology may originate diverse results under different environmental conditions. Recently, naturalistic engineering techniques developed on land, have been used for transplantations of P. oceanica. Pilot projects concerning small surfaces were carried out between 2006 and 2010. More recently, a large-scale program (0.1 km2) was realized in 2012 at Civitavecchia (Roma, Thyrrenian Sea). The applied technique consists basically of mattresses filled with sand coupled with a net covering able to hold steady in situ the plant rhizomes. These structures have been variously modified in time to be adapted to the different type of substratum and various hydrodynamic conditions of the transplanting sites. Following the results of these transplantation experiences, we analyzed pros and cons of the techniques in order to improve the methodology. Firstly, these techniques may be considered suitable to large-scale projects allowing to minimize transplantation times. Secondly, the rhizomes may be successfully fixed to the structures; the majority of the transplanted shoots was not damaged showing a very good vegetative vitality with the production of new rhizomes, leaves and roots few months after transplanting. Finally, this procedure is flexible, as the basic technique can be modified and tailored to the various environmental conditions of the different receiving site. However, the results obtained in different areas are highly heterogeneous suggesting that a careful selection of the hosting site is a focal point. To this aim, a pilot study before the beginning of large-scale project seems mandatory, providing a fundamental support to guarantee successful results.

A redescription of a Maastrichtian lobster Hoploparia antarctica Wilckens, 1907 (Crustacea: Decapoda), from Chubut, Argentina

1991 ◽  
Vol 65 (5) ◽  
pp. 795-800 ◽  
Author(s):  
M. B. Aguirre-Urreta ◽  
E. B. Olivero ◽  
F. A. Medina
Keyword(s):  
Geographic Distribution ◽  
Trace Fossils ◽  
Sedimentary Structures ◽  
New Findings ◽  
Southern Patagonia ◽  
Molluscan Fauna

The discovery of beautifully preserved specimens of a macruran decapod provides the basis for redescription of Hoploparia antarctica Wilckens, a hitherto poorly known species from the Campanian–Maastrichtian of the Austral basin of Southern Patagonia. Analyses of the associated molluscan fauna, trace fossils, and sedimentary structures indicate that the material is mostly preserved in calcareous sandstones and coquinas deposited in shallow, well-oxygenated environments. These new findings of H. antarctica in Maastrichtian deposits of the Lefipán Formation of Chubut expand the geographic distribution of the species and add a new element for the comparison of the Lefipán fauna with that of the austral Wedellian Province.

In vitro studies on the induction of sporogenous tissue on leaves of cinnamon fern. I. Environmental factors

1972 ◽  
Vol 50 (12) ◽  
pp. 2673-2682 ◽  
Author(s):  
William H. Harvey ◽  
James D. Caponetti
Keyword(s):  
Environmental Factors ◽  
Light Intensity ◽  
Environmental Conditions ◽  
Light Exposure ◽  
Progressive Increase ◽  
Light Phase ◽  
Sporogenous Tissue ◽  
Light Darkness

Intact, set III, cinnamon fern cataphyll and frond primordia, which were shown to have no predisposition to fertility in situ, produced sporangia when excised and cultured under sterile conditions in Knudson's medium supplemented with various levels of sucrose and maintained on 11 different regimens of light, darkness, and temperature for 10 weeks. Increasing levels of sucrose resulted in increased fertility under all environmental conditions, but the highest percentage of fertility was obtained under conditions of continuous dark at 26 °C. As the length of the light phase of the photoperiods decreased, a progressive increase in induction of fertile leaves was observed, suggesting that periods of long light exposure are inhibitory to the initiation of sporangia. Conversely, as the light intensity was increased, an inhibition of sporophyll differentiation occurred. Sporangia excised from dark-induced sporophylls and cultured in the light produced viable spores which germinated yielding haploid gametophytes that ultimately produced sporophytes.

Palaeoenvironmental significance of storm coquinas in a Lower Cretaceous coastal lagoonal succession (Vectis Formation, Isle of Wight, southern England)

2000 ◽  
Vol 137 (2) ◽  
pp. 193-205 ◽  
Author(s):  
JONATHAN D. RADLEY ◽  
MICHAEL J. BARKER
Keyword(s):  
High Resolution ◽  
Principal Components ◽  
Lower Cretaceous ◽  
Coastal Lagoons ◽  
Trace Fossils ◽  
Isle Of Wight ◽  
Southern England ◽  
Desiccation Cracks ◽  
Stratigraphic Framework

Thin bioclastic limestone beds (‘coquinas’) in the Vectis Formation (Wealden Group, Lower Cretaceous) of the Isle of Wight, southern England, exhibit a range of biofabrics and internal stratigraphies. These features are attributed to both simple and complex storm deposition of allochthonous biogenic and siliciclastic materials in coastal lagoons and on adjacent mudflats. These modes of deposition facilitated preservation of dinosaur trackways, desiccation cracks, shallow-tier trace fossils and in situ bivalve colonies through rapid burial. The coquinas thus preserve a record of surficial muds, commonly lost through reworking. The principal components of the coquinas comprise dispersed elements from within the argillaceous ‘background’ facies. Some of these beds are laterally traceable for up to 27 km, providing the foundations for a high-resolution event-stratigraphic framework.

scholarly journals The Influence of Bedding Planes and Permeability Coefficient on Fracture Propagation of Horizontal Wells in Stratification Shale Reservoirs

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Yuepeng Wang ◽  
Xiangjun Liu ◽  
Lixi Liang ◽  
Jian Xiong
Keyword(s):  
Permeability Coefficient ◽  
In Situ Stress ◽  
Stress Difference ◽  
Strength Parameters ◽  
Breakdown Pressure ◽  
Permeability Coefficients ◽  
Bedding Planes ◽  
Initiation Pressure ◽  
Shale Reservoirs

The complexity of hydraulic fractures (HF) significantly affects the success of reservoir reconstruction. The existence of a bedding plane (BP) in shale impacts the extension of a fracture. For shale reservoirs, in order to investigate the interaction mechanisms of HF and BPs under the action of coupled stress-flow, we simulate the processes of hydraulic fracturing under different conditions, such as the stress difference, permeability coefficients, BP angles, BP spacing, and BP mechanical properties using the rock failure process analysis code (RFPA2D-Flow). Simulation results showed that HF spread outward around the borehole, while the permeability coefficient is uniformly distributed at the model without a BP or stress difference. The HF of the formation without a BP presented a pinnate distribution pattern, and the main direction of the extension is affected by both the ground stress and the permeability coefficient. When there is no stress difference in the model, the fracture extends along the direction of the larger permeability coefficient. In this study, the in situ stress has a greater influence on the extension direction of the main fracture when using the model with stress differences of 6 MPa. As the BP angle increases, the propagation of fractures gradually deviates from the BP direction. The initiation pressure and total breakdown pressure of the models at low permeability coefficients are higher than those under high permeability coefficients. In addition, the initiation pressure and total breakdown pressure of the models are also different. The larger the BP spacing, the higher the compressive strength of the BP, and a larger reduction ratio (the ratio of the strength parameters of the BP to the strength parameters of the matrix) leads to a smaller impact of the BP on fracture initiation and propagation. The elastic modulus has no effect on the failure mode of the model. When HF make contact with the BP, they tend to extend along the BP. Under the same in situ stress condition, the presence of a BP makes the morphology of HF more complex during the process of propagation, which makes it easier to achieve the purpose of stimulated reservoir volume (SRV) fracturing and increased production.

Measuring Radon and Thoron Levels in Sri Lanka

2013 ◽  
Vol 718-720 ◽  
pp. 721-724
Author(s):  
Deepal Subasinghe Nalaka ◽  
Mahakumara Prasad ◽  
Thusitha B. Nimalsiri ◽  
Nuwan B. Suriyaarchchi ◽  
Takeshi Iimoto ◽  
...  
Keyword(s):  
Sri Lanka ◽  
Environmental Conditions ◽  
In Situ Measurements ◽  
Physical Factors ◽  
Preliminary Results ◽  
Radon Measurements ◽  
First Time

For the first time in Sri Lanka, an attempt was made to measure the outdoor radon levels using CR 39 type passive radon detectors. Preliminary results indicate that in Sri Lanka, 220Rn isotope is more abundance than 222Rn isotope. These results were also confirmed by in-situ measurements. Sri Lanka has one of the highest 220Rn values in the region. It was also noted that environmental conditions and other physical factors have a significant effect on the outdoor radon measurements using passive discriminative detectors.

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