The Unmetamorphosed Sedimentary Fill of the Brent Meteorite Crater, Southeastern Ontario

1975 ◽  
Vol 12 (4) ◽  
pp. 606-628 ◽  
Author(s):  
G. P. Lozej ◽  
F. W. Beales
Keyword(s):  
Sea Water ◽  
Sediment Accumulation ◽  
General Level ◽  
Crater Floor ◽  
Middle Ordovician ◽  
Basement Rocks ◽  
Shelf Sea ◽  
Precambrian Terrain ◽  
Sedimentary Fill ◽  
The Impact

A 10 000-ft (~3050-m) diameter circular structure that exhibits rimmed crater form, shock-metamorphic features, and underlying unbrecciated basement rocks occurs near Brent, Ontario, close to the southern margin of the Canadian Shield. In its center 863 ft (263 m) of Middle Ordovician sediments are preserved. Shortly after impact a nearly level crater floor was established and the subsequent sequence appears to have been deposited close to mean sea level. Repeated sediment laminae probably reflected wind-tidal marine incursions onto the low relief margin of the contemporary Ordovician epicontinental sea. Throughout much of its period of sediment accumulation, the crater floor appears to have been nearly flat. A 380-ft (115.8 m) sequence of dolostones, arkosic siltstones, and evaporite layers and veins formed within a breccia-rimmed depression. Initially sea water carrying fine silt invaded the crater and refluxed through the porous and permeable crater rim. Subsequently some 100 ft (30.5 m) of silty arkose blanketed the area, probably resulting from further transgression of the Middle Ordovician seas and breaching of the crater walls. An upper 380 ft (115.8 m) of predominantly thin-bedded lagoonal and shallow shelf sea limestones are divided into upper and lower sequences by a middle regressive set of red beds.The implied near-flat crater floor, coupled with preservation of over 800 ft (>244 m) of crater sediments, suggests continued slow subsidence. Earlier on, this subsidence affected only the crater area, but later episodes of subsidence were regional, involving Ordovician, Silurian, and Devonian sedimentation. The superincumbent load further compacted the total crater sequence. Preservation of the rocks described here is due to final depression of the sequence into a position below the general level of the surrounding Precambrian terrain. If Brent can be considered to be a typical peri-marine meteoritic impact crater, all such craters should have in common an inward-dipping succession of open-circulation sediments overlying a crater-rim restricted sedimentary sequence, which in turn overlies a shock-metamorphosed series of breccias.Compaction of the impact-generated breccias and subsequent unmetamorphosed crater-filling sediments influenced both sediment accumulation and the ultimate crater structure.

Post-impact deposits in Tvären, a marine Middle Ordovician crater south of Stockholm, Sweden

1994 ◽  
Vol 131 (1) ◽  
pp. 91-103 ◽  
Author(s):  
M. Lindström ◽  
T. Flodén ◽  
Y. Grahn ◽  
B. Kathol
Keyword(s):  
Sea Water ◽  
Time Interval ◽  
Early Date ◽  
Middle Cambrian ◽  
Middle Ordovician ◽  
Basement Rocks ◽  
Open Sea ◽  
Post Impact ◽  
The Impact ◽  
Stratigraphic Succession

AbstractThe well-preserved Tvären crater is noteworthy for being one of a small number of Early and Middle Ordovician impact structures formed in a marine environment. It is demonstrated to be an impact structure by the presence of a breccia lens, consisting of crystalline basement rocks, and shocked quartz. The breccia lens formed under dry-hot conditions after expulsion of sea-water by the impact. Resurging sea-water thereupon deposited a positively graded, 60 m thick turbidite-like unit. This graded resurge deposit is a previously unknown feature, to be expected in open-sea impacts. Breccia in the lower part of this graded deposit contains fragments of a remarkably complete orthoceratite limestone succession that existed at the site of impact, resting on non-lithified sand of probably Early to earliest Middle Cambrian age. A sedimentary succession was deposited inside the crater at depths decreasing from more than 200 m in the initial stages to some 100 m at the time of deposition of the youngest preserved beds. The environment within the crater thus favoured deposition of an essentially complete stratigraphic succession with depth-controlled palaeoecology for a significant time interval after the impact. Whereas planktonic members, like graptolites and chitinozoa, are present throughout the post-impact succession, and asaphids, almost as persistent, became established at an early date, burrowers were somewhat reluctant to enter and remopleuridids and small strophomenids came in at a late stage. We suggest as a result of this study that structures formed by impact may offer unique information about the palaeogeology and palaeoenvironment of the region hit by the impact.

Emplacement of sharp-walled sulfide veins during the formation and reactivation of impact-related structures at the Broken Hammer Mine, Sudbury, Ontario

2020 ◽  
Vol 57 (10) ◽  
pp. 1149-1166 ◽  
Author(s):  
M.F. Hall ◽  
B. Lafrance ◽  
H.L. Gibson
Keyword(s):  
Massive Sulfide ◽  
Hydrothermal Fluids ◽  
Crater Floor ◽  
Sudbury Igneous Complex ◽  
Tectonic Events ◽  
Brittle Ductile Transition ◽  
Basement Rocks ◽  
Post Impact ◽  
Platinum Group ◽  
The Impact

Broken Hammer is a hybrid Cu–Ni–Platinum Group Element (PGE) footwall deposit located in Archean basement rocks below the impact-induced Sudbury Igneous Complex (SIC), Canada. The deposit consists of massive chalcopyrite veins surrounded by thin epidote, actinolite, and quartz selvedges and low-sulfide, high-PGE mineralization consisting of disseminated chalcopyrite (<5%) and platinum group minerals, associated with Ni-bearing chlorite overprinting alteration patches of epidote, actinolite, and quartz. The veins are grouped into five steeply-dipping sets, striking northeast-, southwest-, southeast-, south-, and east–west, which were emplaced along impact-related fractures that were reactivated multiple times during stabilization of the crater floor. Early reactivation of the fractures created pathways for the migration of hydrothermal fluids from which quartz and chlorite precipitated sealing the fractures. Renewed slip shattered the quartz–chlorite veins into fragments that were incorporated in massive sulfide veins that crystallized from fractionated sulfide melts or from high temperature (400–500 °C) hydrothermal fluids, which migrated outward into the basement rocks from a cooling and crystallizing SIC melt sheet. Hydrothermal fluids syn-genetic with the epidote–actinolite–quartz alteration distributed the PGE into the footwall rocks, or late hydrothermal fluids associated with the Ni-bearing chlorite leached Ni and PGMs from the sulfide veins and redistributed them to form low-sulfide, high-PGE zones in the footwall rocks. During post-impact tectonic events, slip at temperatures below the brittle–ductile transition for chalcopyrite (<200 °C to 250 °C) produced striations along the vein margins. The Broken Hammer deposit exemplifies how Cu–Ni–PGE footwall deposits formed by the reactivation of impact-related fractures that provided conduits for the migration of melts and hydrothermal fluids.

Granular zircon from Vredefort granophyre (South Africa) confirms the deep injection model for impact melt in large impact structures

Geology ◽  
2019 ◽  
Vol 47 (8) ◽  
pp. 691-694 ◽  
Author(s):  
Elizaveta Kovaleva ◽  
Dmitry A. Zamyatin ◽  
Gerlinde Habler
Keyword(s):  
South Africa ◽  
Large Impact ◽  
Crater Floor ◽  
Pressure Shock ◽  
Impact Melt ◽  
Basement Rocks ◽  
High Shock ◽  
Injection Model ◽  
History Of ◽  
The Impact

Abstract The Vredefort impact structure, South Africa, is a 2.02 Ga deeply eroded meteorite scar that provides an opportunity to study large impact craters at their lower stratigraphic levels. A series of anomalous granophyre dikes in the core of the structure are believed to be composed of an impact melt, which intruded downwards from the crater floor, exploiting fractures in basement rocks. However, the melt emplacement mechanisms and timing are not constrained. The granophyre dikes contain supracrustal xenoliths captured at higher levels, presently eroded. By studying these clasts and shocked minerals within, we can better understand the nature of dikes, magnitude of impact melt movement, conditions that affected target rocks near the impacted surface, and erosional rates. We report “former reidite in granular neoblastic” (FRIGN) zircon within a granite clast enclosed in the granophyre. High-pressure zircon transformation to reidite (ZrSiO4) and reversion to zircon resulted in zircon grains composed of fine neoblasts (∼0.5–3 µm) with two or three orthogonal orientations. Our finding provides new independent constraints on the emplacement history of Vredefort granophyre dikes. Based on the environment, where other FRIGN zircons are found (impact glasses and melts), the clast was possibly captured near the top of the impact melt sheet and transported to the lowermost levels of the structure, traveling some 8–10 km. Our finding not only provides the highest-pressure shock estimates thus far discovered in the Vredefort structure (≥30 GPa), but also shows that microscopic evidence of high shock pressures can be found within large eroded craters at their lowest stratigraphic levels.

Subsurface stratigraphy and basin-fill architecture of the late Paleozoic eastern Taos trough, northern New Mexico, U.S.A.

2020 ◽  
Vol 57 (3) ◽  
pp. 149-176
Author(s):  
Nur Uddin Md Khaled Chowdhury ◽  
Dustin E. Sweet
Keyword(s):  
New Mexico ◽  
Sediment Accumulation ◽  
Late Paleozoic ◽  
North Central ◽  
The North ◽  
Basement Rocks ◽  
Basin Geometry ◽  
Deformation Event ◽  
Thrust System ◽  
Basin Fill

The greater Taos trough located in north-central New Mexico represents one of numerous late Paleozoic basins that formed during the Ancestral Rocky Mountains deformation event. The late Paleozoic stratigraphy and basin geometry of the eastern portion of the greater Taos trough, also called the Rainsville trough, is little known because the strata are all in the subsurface. Numerous wells drilled through the late Paleozoic strata provide a scope for investigating subsurface stratigraphy and basin-fill architecture of the Rainsville trough. Lithologic data obtained predominantly from petrophysical well logs combined with available biostratigraphic data from the greater Taos trough allows construction of a chronostratigraphic framework of the basin fill. Isopach- and structure-maps indicate that the sediment depocenter was just east of the El Oro-Rincon uplift and a westerly thickening wedge-shaped basin-fill geometry existed during the Pennsylvanian. These relationships imply that the thrust system on the east side of the Precambrian-cored El Oro-Rincon uplift was active during the Pennsylvanian and segmented the greater Taos trough into the eastern Rainsville trough and the western Taos trough. During the Permian, sediment depocenter(s) shifted more southerly and easterly and strata onlap Precambrian basement rocks of the Sierra Grande uplift to the east and Cimarron arch to the north of the Rainsville trough. Permian strata appear to demonstrate minimal influence by faults that were active during the Pennsylvanian and sediment accumulation occurred both in the basinal area as well as on previous positive-relief highlands. A general Permian decrease in eustatic sea level and cessation of local-fault-controlled subsidence indicates that regional subsidence must have affected the region in the early Permian.

Effect of long-term moisture exposure on impact response of glass-reinforced vinylester

2021 ◽  
pp. 147509022199616
Author(s):  
Fatemeh Alizadeh ◽  
Navid Kharghani ◽  
Carlos Guedes Soares
Keyword(s):  
Water Uptake ◽  
Failure Modes ◽  
Sea Water ◽  
Composite Plates ◽  
Impact Response ◽  
Low Velocity Impact ◽  
Water Type ◽  
Interfacial Damage ◽  
Impact Properties ◽  
The Impact

Glass/Vinylester composite laminates are comprehensively characterised to assess its impact response behaviour under moisture exposure in marine structures. An instrumented drop weight impact machine is utilised to determine the impact responses of dry and immersed specimens in normal, salted and sea water. The specimens, which had three different thicknesses, were subjected to water exposure for a very long period of over 20 months before tested in a low-velocity impact experiment. Water uptake was measured primarily to study the degradation profiles of GRP laminates after being permeated by water. Matrix dissolution and interfacial damage observed on the laminates after prolonged moisture exposure while the absorption behaviour was found typically non-Fickian. The weight of the composite plates firstly increased because of water diffusion up to month 15 and then decreased due to matrix degradation. The specimens with 3, 6 and 9 mm thickness exhibited maximum water absorption corresponding to 2.6%, 0.7% and 0.5% weight gain, respectively. In general, the results indicated that water uptake and impact properties were affected by thickness and less by water type. Impact properties of prolonged immersed specimens reduced remarkably, and intense failure modes detected almost in all cases. The least sensitive to impact damage were wet specimens with 9 mm thickness as they indicated similar maximum load and absorbed energy for different impact energies.

Microstructure and Corrosion Resistance of HVOF Sprayed 316L Stainless Steel and Ni Base Alloy Coatings

2000 ◽  
Author(s):  
S. Kuroda ◽  
T. Fukushima ◽  
T. Kodama ◽  
M. Sasaki
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
316L Stainless Steel ◽  
Sea Water ◽  
Base Alloy ◽  
Standard Condition ◽  
Polarization Measurement ◽  
Superior Corrosion Resistance ◽  
Distribution Composition ◽  
The Impact

Abstract 316L stainless steel and Hastelloy C alloy powders were sprayed by an HVOF apparatus onto mild steel substrates. The microstructure, pore size distribution, composition and corrosion resistance of thus obtained coatings were evaluated experimentally. Corrosion resistance in sea-water was examined by monitoring the impedance and corrosion potential of samples immersed in artificial sea-water at 300 K over a period of more than 3 months and also by polarization measurement. It was found that the stainless coatings composed mainly of plastically deformed particles and some splats which were molten at the impact. By increasing the combustion pressure, the porosity as measured by mercury porosimeter could be reduced to below 1%. In comparison, Hastelloy C deposits sprayed under the standard condition were so dense that its porosity could not be measured by the porosimeter. The polarization curve and the results of impedance monitoring both exemplified that the Hastelloy C coatings possess much superior corrosion resistance to the stainless coatings in sea-water, which was attributed to the higher density and better adhesion of the Ni-base alloy coatings.

Bioresilience to Mercury Chloride of the Brine Shrimp Artemia Salina after Treatment with Homeopathic Mercurius Corrosivus

Homeopathy ◽  
2021 ◽  
Author(s):  
Andreia Adelaide G. Pinto ◽  
Mirian Y. de Oliveira Nagai ◽  
Ednar Nascimento Coimbra ◽  
Suham Nowrooz Mohammad ◽  
Jefferson Souza Silva ◽  
...  
Keyword(s):  
Sea Water ◽  
Specific Interaction ◽  
Artemia Salina ◽  
Mercury Content ◽  
Mercury Chloride ◽  
Hatching Rate ◽  
Toxic Substances ◽  
Protective Effects ◽  
Cyst Hatching ◽  
The Impact

Abstract Introduction Finding solutions to mitigate the impact of pollution on living systems is a matter of great interest. Homeopathic preparations of toxic substances have been described in the literature as attenuation factors for intoxication. Herein, an experimental study using Artemia salina and mercury chloride was developed as a model to identify aspects related to bioresilience. Aims The aim of the study was to describe the effects of homeopathic Mercurius corrosivus (MC) on Artemia salina cysts hatching and on mercury bioavailability. Methods Artemia salina cysts were exposed to 5.0 µg/mL of mercury chloride during the hatching phase. MC potencies (6cH, 30cH, and 200cH) were prepared in sterile purified water and poured into artificial sea water. Different controls were used (non-challenged cysts and challenged cysts treated with water, succussed water, and Ethilicum 1cH). Four series of nine experiments were performed to evaluate the percentage of cyst hatching. Soluble total mercury (THg) levels and precipitated mercury content were also evaluated. Solvatochromic dyes were used to check for eventual physicochemical markers of MC biological activity. Results Significant delay (p < 0.0001) in cyst hatching was observed only after treatment with MC 30cH, compared with controls. This result was associated with an increase of THg concentration in water (p = 0.0018) and of chlorine/oxygen ratio (p < 0.0001) in suspended micraggregates, suggesting changes in mercury bioavailability. A specific interaction of MC 30cH with the solvatochromic dye ET33 (p = 0.0017) was found. Conclusion Changes in hatching rate and possible changes in Hg bioavailability are postulated as protective effects of MC 30cH on Artemia salina, by improving its natural bioresilience processes.

scholarly journals The European Convention on Human Rights Act 2003 – Ten Years On

2014 ◽  
Vol 3 (1) ◽  
pp. 61-96
Author(s):  
Ronagh JA McQuigg
Keyword(s):  
Human Rights ◽  
The State ◽  
European Convention ◽  
General Level ◽  
Human Rights Act ◽  
Human Rights Act 1998 ◽  
The Impact ◽  
The Relationship

The European Convention on Human Rights Act 2003 has now been in force in Ireland for ten years. This article analyses the Act itself and the impact which it has had on the Irish courts during the first decade of its operation. The use of the European Convention on Human Rights in the Irish courts prior to the enactment of the legislation is discussed, as are the reasons for the passing of the Act. The relationship between the Act and the Irish Constitution is examined, as is the jurisprudence of the Irish courts towards the interpretative obligation found in section 2(1), and the duty placed upon organs of the State by section 3(1). The article ends with a number of observations regarding the impact which the Act has had on the Irish courts at a more general level. Comparisons will be drawn with the uk’s Human Rights Act 1998 throughout the discussion.

scholarly journals The importance of information upon applying IFRS in financial entities that trade at the Colombian stock market

2019 ◽  
Vol 21 (34) ◽  
pp. 137-152
Author(s):  
Miguel Angel Laverde Sarmiento ◽  
Jorge Fernando Garcia Carrillo ◽  
Juan Carlos Lezama Palomino ◽  
Alejandra Patiño Jacinto
Keyword(s):  
Financial Reporting ◽  
Stock Price ◽  
Stock Exchange ◽  
Regulatory Framework ◽  
General Level ◽  
Market Exchange ◽  
Generally Accepted Accounting Principles ◽  
Financial Reporting Standards ◽  
Before And After ◽  
The Impact

The aim of this research is to determine whether the implementation of the International Financial Reporting Standards (IFRS) in the companies of the financial sector listed on the Colombian Stock Exchange has greater relevance compared to the previous accounting regulatory framework known as Generally Accepted Accounting Principles (GAAP) in Colombia, for the years 2009 to 2016. Taking into account the concept of valorative relevance that indicates that the accounting information is relevant if it affects the stock price reflected in the capital market exchange. To determine this relationship, an adaptation of the model proposed by Ohlson (1995) is used, because it is the most frequently used to measure relevance. The modifications made to the model were to include accounting variables of financial instruments of assets and liabilities to better measure the impact of the IFRS. On a general level, the conclusion is reached that the valorative relevance of financial companies listed on the stock exchange between 2009 and 2016, does not change due to the application of the IFRS. The results are because the regulation that financial companies that are listed on the stock exchange of Colombia are subject to has contributed to the relevance being maintained before and after the application of the new regulatory framework. however, when carrying out the study of the information taking into account only the variables and taking into account the regulations under the IFRS, they present a greater degree of significance.

scholarly journals ТЕОРЕТИЧЕСКИЕ И ПРАКТИЧЕСКИЕ ПОДХОДЫ К ОПРЕДЕЛЕНИЮ ОСОБЕННОСТИ ПСИХОЛОГИЧЕСКОЙ ПОМОЩИ ЖЕНАМ ПОГИБШИХ ПРАВООХРАНИТЕЛЕЙ ПРИ УТРАТЕ

World Science ◽  
2018 ◽  
pp. 71-79
Author(s):  
Рыбык Л. А.
Keyword(s):  
Traumatic Event ◽  
Emergency Situation ◽  
Psychological Adaptation ◽  
Psychological Support ◽  
Stress Factors ◽  
Psychological State ◽  
General Level ◽  
Scientific Heritage ◽  
Psychological Assistance ◽  
The Impact

The preambule gives the reasons for the relevance of the problem of experiencing the loss and grief of the perished law enforcers` wives in Ukraine, providing them with psychological counseling and the necessary psychological assistance based on the modern scientific heritage, world and local practical experience. The aim of the study is to examine the theoretical and practical approaches of providing psychological assistance to widows, as well as to analyze the impact of psychological assistance on the overall level of adaptive grieving.The main part reveals the main theoretical and practical approaches to the definition of varieties, structure and content of systemic psychological support based on extreme psychology and crisis intervention. It was noted the necessity of providing emotional support and psychological assistance at the early stages of experiencing grief and loss. It presents the brief description of the factors influencing psychological state of the person, who is in an emergency situation - the sudden death of a loved one.The concept of adaptive and non-adaptive ways of responding to stress factors, based on a study by E. Lindemann, is considered. Psychological reactions are described that correspond to different phases of a crisis state after a traumatic event, accordingly to the studies of D. Aguilera and J. Messick. The results of a comparative experimental psychological examination of the perished law enforcers` wives are set out in order to determine the significance of individual factors of socio-psychological adaptation for the formation of effective psych correctional programs. Statistically reliable data on the impact of psychological support on the general level of socio-psychological adaptation are obtained. In conclusion, it is stated the reasonability of providing the psychological assistance in case of loss, taking into account the hierarchy of personal problems. Experimentally proven that, when providing systemic psychological assistance, there is a tendency towards to of adaptability and emotional comfort indicators, decrease of level and moving away from problem situations avoidance.

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