Hydrochronology of a proposed deep geological repository for low- and intermediate-level nuclear waste in southern Ontario from U–Pb dating of secondary minerals: response to Silurian and Cretaceous events

2020 ◽  
Vol 57 (4) ◽  
pp. 464-476 ◽  
Author(s):  
D.W. Davis ◽  
C.N. Sutcliffe ◽  
A.M. Thibodeau ◽  
J. Spalding ◽  
D. Schneider ◽  
...  
Keyword(s):  
Carbonate Platform ◽  
Sedimentary Rocks ◽  
North American Plate ◽  
Deep Geological Repository ◽  
Near Surface ◽  
Southern Ontario ◽  
The North ◽  
Nuclear Site ◽  
Geological Repository ◽  
Carbonate Formations

A record of fluid flow has been documented within a Paleozoic carbonate platform sequence by U–Pb dating of calcite in veins and vugs from rock core sampled through a shallowly dipping sequence of sedimentary rocks beneath the Bruce nuclear site, Ontario, Canada. Secondary calcite from >650 m deep Ordovician carbonate rocks yields a Silurian age of 434 ± 5 Ma possibly related to infiltration of seawater from overlying evaporitic basins as well as hydrothermal solutions that infiltrated from below. In contrast, near-surface Devonian rocks mostly give vein infill ages over the range of 80–100 Ma with evidence for younger infill down to 50 Ma. Vein calcite samples previously dated from surface outcrops of Ordovician carbonate exposed up to 500 km to the east yielded similar U–Pb ages. Coincidence of near-surface vein calcite ages indicates widespread vein emplacement synchronous with a change in direction of motion of the North American plate as well as possible erosional unroofing following passage of the region over the Great Meteor hotspot approximately 125 Myr ago. Deeper carbonate formations have remained apparently impermeable to post-Paleozoic disturbance despite these perturbations.

Fractures in the northern plains, stream patterns, and the midcontinent stress field

1987 ◽  
Vol 24 (6) ◽  
pp. 1086-1097 ◽  
Author(s):  
Mel R. Stauffer ◽  
Don J. Gendzwill
Keyword(s):  
Stress Field ◽  
Horizontal Stress ◽  
The Body ◽  
North American Plate ◽  
Plate Motion ◽  
Viscous Drag ◽  
Near Surface ◽  
The North ◽  
Elastic Rebound ◽  
Western North Dakota

Fractures in Late Cretaceous to Late Pleistocene sediments in Saskatchewan, eastern Montana, and western North Dakota form two vertical, orthogonal sets trending northeast–southwest and northwest–southeast. The pattern is consistent, regardless of rock type or age (except for concretionary sandstone). Both sets appear to be extensional in origin and are similar in character to joints in Alberta. Modem stream valleys also trend in the same two dominant directions and may be controlled by the underlying fractures.Elevation variations on the sub-Mannville (Early Cretaceous) unconformity form a rectilinear pattern also parallel to the fracture sets, suggesting that fracturing was initiated at least as early as Late Jurassic. It may have begun earlier, but there are insufficient data at present to extend the time of initiation.We interpret the fractures as the result of vertical uplift together with plate motion: the westward drift of North America. The northeast–southwest-directed maximum principal horizontal stress of the midcontinent stress field is generated by viscous drag effects between the North American plate and the mantle. Vertical uplift, erosion, or both together produce a horizontal tensile state in near-surface materials, and with the addition of a directed horizontal stress through plate motion, vertical tension cracks are generated parallel to that horizontal stress (northeast–southwest). Nearly instantaneous elastic rebound results in the production of second-order joints (northwest–southeast) perpendicular to the first. In this manner, the body of rock is being subjected with time to complex alternation of northeast–southwest and northwest–southeast horizontal stresses, resulting in the continuous and contemporaneous production of two perpendicular extensional joint sets.

Upper Ordovician conodont biostratigraphy and the age of the Collingwood Member, southern Ontario, Canada1Earth Science Sector (ESS) Contribution 20100302.

2011 ◽  
Vol 48 (11) ◽  
pp. 1497-1522 ◽  
Author(s):  
Shunxin Zhang ◽  
Glen A. Tarrant ◽  
Christopher R. Barnes
Keyword(s):  
North Atlantic ◽  
Carbonate Platform ◽  
Upper Ordovician ◽  
Hydrocarbon Source Rock ◽  
Southern Ontario ◽  
Blue Mountain ◽  
The North ◽  
Atlantic Province ◽  
Taconic Orogeny ◽  
A New Species

The Upper Ordovician stratigraphy in southern Ontario represents the clastic foredeep associated with the Appalachian Taconic Orogeny transitioning northwest into coeval carbonate platform facies. Ten measured and sampled sections in both the Collingwood area and on Manitoulin Island, Lake Huron, provide two relatively complete composite sections (277 and 95 m, respectively) through the marine part of the sequence. A total of 100 2 kg samples collected for a conodont biostratigraphic study yielded 77 215 well-preserved specimens. Taxonomic study of the fauna, illustrated herein, identified 34 species representing 22 genera and three taxa in open nomenclature. Taxonomic revisions are made to five species of Pseudobelodina and one of Rhipidognathus ; a new species, Pseudobelodina microdentata , is established. The fauna primarily represents the Midcontinent Province with incursions from the North Atlantic Province primarily in the Collingwood area. Four conodont zones are recognized that help refine the ages for the Upper Ordovician upper Lindsay (Collingwood Member), Blue Mountain, Georgian Bay, and Queenston formations. In particular, the Collingwood Member of the Lindsay Formation, a regionally distributed organic-rich shale of hydrocarbon source rock potential, is demonstrated to lie within the Amorphognathus ordovicicus Zone of North Atlantic Province and the Oulodus robustus Zone of Midcontinent Province and to be early Richmondian age.

The Nares Strait gravity anomaly and its implications for crustal structure

1985 ◽  
Vol 22 (9) ◽  
pp. 1322-1328 ◽  
Author(s):  
H. R. Jackson ◽  
L. Koppen
Keyword(s):  
Gravity Anomaly ◽  
Sedimentary Rocks ◽  
Ellesmere Island ◽  
North American Plate ◽  
Nares Strait ◽  
The North ◽  
Free Air ◽  
Plate Reconstructions ◽  
Free Air Gravity ◽  
East West

A negative free-air gravity anomaly is associated with Nares Strait, the waterway that separates Ellesmere Island and Greenland. Two east–west gravity profiles that cross Ellesmere Island and Nares Strait were collected. A low with values in the range of −100 to −120 mGal (−1000 to −1200 μm/s2) was observed, and two-dimensional crustal models were created to identify the cause of the anomaly. The gravity anomaly cannot be attributed wholly to the bathymetry of the strait or to the sedimentary rocks underlying the strait. Crustal models that reproduce the anomaly have a M discontinuity that slopes under Nares Strait towards Ellesmere Island so that the crust beneath Ellesmere Island is thickened. The anomaly is similar to those associated with ancient and modern suture zones, regions of collided continental crust. Plate reconstructions suggest Nares Strait is a collisional boundary between the North American Plate (Ellesmere Island) and the Greenland Plate. The gravity anomaly supports this interpretation of Nares Strait.

Benthic foraminiferal zonation in deep-water carbonate platform margin environments, northern Little Bahama Bank

1988 ◽  
Vol 62 (01) ◽  
pp. 1-8 ◽  
Author(s):  
Ronald E. Martin
Keyword(s):  
Deep Water ◽  
Benthic Foraminifera ◽  
Carbonate Platform ◽  
Sedimentary Facies ◽  
Depositional Environments ◽  
Near Surface ◽  
Sediment Gravity Flows ◽  
Gravity Flows ◽  
Platform Margin ◽  
Water Carbonate

The utility of benthic foraminifera in bathymetric interpretation of clastic depositional environments is well established. In contrast, bathymetric distribution of benthic foraminifera in deep-water carbonate environments has been largely neglected. Approximately 260 species and morphotypes of benthic foraminifera were identified from 12 piston core tops and grab samples collected along two traverses 25 km apart across the northern windward margin of Little Bahama Bank at depths of 275-1,135 m. Certain species and operational taxonomic groups of benthic foraminifera correspond to major near-surface sedimentary facies of the windward margin of Little Bahama Bank and serve as reliable depth indicators. Globocassidulina subglobosa, Cibicides rugosus, and Cibicides wuellerstorfi are all reliable depth indicators, being most abundant at depths >1,000 m, and are found in lower slope periplatform aprons, which are primarily comprised of sediment gravity flows. Reef-dwelling peneroplids and soritids (suborder Miliolina) and rotaliines (suborder Rotaliina) are most abundant at depths <300 m, reflecting downslope bottom transport in proximity to bank-margin reefs. Small miliolines, rosalinids, and discorbids are abundant in periplatform ooze at depths <300 m and are winnowed from the carbonate platform. Increased variation in assemblage diversity below 900 m reflects mixing of shallow- and deep-water species by sediment gravity flows.

Seismite in the Devonian Sultan Formation, Frenchman Mountain, Nevada: Evidence of far-field effect of the Alamo Event

2016 ◽  
Vol 53 (2) ◽  
pp. 93-114
Author(s):  
Jesús Pinto ◽  
John Warme
Keyword(s):  
Carbonate Platform ◽  
Far Field ◽  
Carbonate Sediments ◽  
Impact Event ◽  
Complex Matrix ◽  
Near Surface ◽  
Fault Block ◽  
Southern Nevada ◽  
Salt Pan ◽  
The Alamo

We interpret a discrete, anomalous ~10-m-thick interval of the shallow-marine Middle to Late Devonian Valentine Member of the Sultan Formation at Frenchman Mountain, southern Nevada, to be a seismite, and that it was generated by the Alamo Impact Event. A suite of deformation structures characterize this unique interval of peritidal carbonate facies at the top of the Valentine Member; no other similar intervals have been discovered in the carbonate beds on Frenchman Mountain or in equivalent Devonian beds exposed in ranges of southern Nevada. The disrupted band extends for 5 km along the Mountain, and onto the adjoining Sunrise Mountain fault block for an additional 4+km. The interval displays a range of brittle, ductile and fluidized structures, and is divided into four informal bed-parallel units based on discrete deformation style and internal features that carry laterally across the study area. Their development is interpreted as the result of intrastratal compressional and contractional forces imposed upon the unconsolidated to fully cemented near-surface carbonate sediments at the top of the Valentine Member. The result is an assemblage of fractured, faulted, and brecciated beds, some of which were dilated, fluidized and injected to form new and complex matrix bands between beds. We interpret that the interval is an unusually thick and well displayed seismite. Because the Sultan Formation correlates northward to the Frasnian (lower Upper Devonian) carbonate rocks of the Guilmette Formation, and the Guilmette contains much thicker and more proximal exposures of the Alamo Impact Breccia, including seismites, we interpret the Frenchman Mountain seismite to be a far-field product of the Alamo Impact Event. Accompanying ground motion and deformation of the inner reaches of the Devonian carbonate platform may have resulted in a fall of relative sea level and abrupt shift to a salt-pan paleoenvironment exhibited by the post-event basal beds of the directly overlying Crystal Pass Member.

scholarly journals The evolving response of mesopelagic fishes to declining midwater oxygen concentrations in the southern and central California Current

2018 ◽  
Vol 76 (3) ◽  
pp. 626-638 ◽  
Author(s):  
J Anthony Koslow ◽  
Pete Davison ◽  
Erica Ferrer ◽  
S Patricia A Jiménez Rosenberg ◽  
Gerardo Aceves-Medina ◽  
...  
Keyword(s):  
Baja California ◽  
Southern Oscillation ◽  
Global Climate ◽  
California Current ◽  
Deep Ocean ◽  
Near Surface ◽  
Oxygen Minimum Zones ◽  
The North ◽  
The Pacific ◽  
Oxygen Concentrations

Abstract Declining oxygen concentrations in the deep ocean, particularly in areas with pronounced oxygen minimum zones (OMZs), are a growing global concern related to global climate change. Its potential impacts on marine life remain poorly understood. A previous study suggested that the abundance of a diverse suite of mesopelagic fishes off southern California was closely linked to trends in midwater oxygen concentration. This study expands the spatial and temporal scale of that analysis to examine how mesopelagic fishes are responding to declining oxygen levels in the California Current (CC) off central, southern, and Baja California. Several warm-water mesopelagic species, apparently adapted to the shallower, more intense OMZ off Baja California, are shown to be increasing despite declining midwater oxygen concentrations and becoming increasingly dominant, initially off Baja California and subsequently in the CC region to the north. Their increased abundance is associated with warming near-surface ocean temperature, the warm phase of the Pacific Decadal oscillation and Multivariate El Niño-Southern Oscillation Index, and the increased flux of Pacific Equatorial Water into the southern CC.

scholarly journals Local radon flux maxima in the quaternary sediments of Schleswig–Holstein (Germany)

2021 ◽  
Author(s):  
Johannes Albert ◽  
Maximilian Schärf ◽  
Frieder Enzmann ◽  
Martin Waltl ◽  
Frank Sirocko
Keyword(s):  
Water Content ◽  
Pore Space ◽  
Mineralogical Composition ◽  
Fault System ◽  
Near Surface ◽  
Salt Diapirism ◽  
The North ◽  
Radon Flux ◽  
Published Evidence ◽  
Tectonically Active

AbstractThis paper presents radon flux profiles from four regions in Schleswig–Holstein (Northern Germany). Three of these regions are located over deep-rooted tectonic faults or salt diapirs and one is in an area without any tectonic or halokinetic activity, but with steep topography. Contrary to recently published studies on spatial patterns of soil radon gas concentration we measured flux of radon from soil into the atmosphere. All radon devices of each profile were deployed simultaneously to avoid inconsistencies due to strong diurnal variations of radon exhalation. To compare data from different seasons, values had to be normalized. Observed radon flux patterns are apparently related to the mineralogical composition of the Quaternary strata (particularly to the abundance of reddish granite and porphyry), and its grain size (with a flux maximum in well-sorted sand/silt). Minimum radon flux occurs above non-permeable, clay-rich soil layers. Small amounts of water content in the pore space increase radon flux, whereas excessive water content lessens it. Peak flux values, however, are observed over a deep-rooted fault system on the eastern side of Lake Plön, i.e., at the boundary of the Eastholstein Platform and the Eastholstein Trough. Furthermore, high radon flux values are observed in two regions associated with salt diapirism and near-surface halokinetic faults. These regions show frequent local radon flux maxima, which indicate that the uppermost strata above salt diapirs are very inhomogeneous. Deep-rooted increased permeability (effective radon flux depth) or just the boundaries between permeable and impermeable strata appear to concentrate radon flux. In summary, our radon flux profiles are in accordance with the published evidence of low radon concentrations in the “normal” soils of Schleswig–Holstein. However, very high values of radon flux are likely to occur at distinct locations near salt diapirism at depth, boundaries between permeable and impermeable strata, and finally at the tectonically active flanks of the North German Basin.

scholarly journals Fault source investigation of the 6 December 2016 MwMw 6.5 Pidie Jaya, Indonesia, earthquake based on GPS and its implications of the geological survey result

2020 ◽  
Vol 14 (4) ◽  
pp. 405-412
Author(s):  
Endra Gunawan ◽  
Takuya Nishimura ◽  
Susilo Susilo ◽  
Sri Widiyantoro ◽  
Nanang T. Puspito ◽  
...  
Keyword(s):  
Surface Deformation ◽  
Source Parameters ◽  
Secondary Effects ◽  
Near Surface ◽  
Morphological Attributes ◽  
Ground Shaking ◽  
The North ◽  
Coulomb Failure ◽  
North And South ◽  
Fault Source

AbstractOn 6 December 2016 at 22:03 UTC, a devastating magnitude 6-class strike-slip earthquake occurred along an unidentified and unmapped fault in Pidie Jaya, northern Sumatra. We analysed the possible fault using continuous Global Positioning System (GPS) observation available in the region. In our investigation, we searched for the fault source parameters of the north- and south-dipping left-lateral faults and the west- and east-dipping right-lateral faults. We identified that the fault responsible for the earthquake was located offshore, with a southwest-northeast direction. We also computed the Coulomb failure stress and compared the result with the distribution of the aftershocks. In this study, we demonstrated that the result of the geological field survey conducted soon after the mainshock was attributed to the secondary effects of ground shaking and near-surface deformation, and not surface faulting. The newly identified offshore fault proposed by this study calls for further investigation of the corresponding submarine morphological attributes in this particular region.

scholarly journals Projected Changes in European and North Atlantic Seasonal Wind Climate Derived from CMIP5 Simulations

2019 ◽  
Vol 32 (19) ◽  
pp. 6467-6490 ◽  
Author(s):  
Kimmo Ruosteenoja ◽  
Timo Vihma ◽  
Ari Venäläinen
Keyword(s):  
North Atlantic ◽  
Climate Models ◽  
Global Climate ◽  
Arctic Sea Ice ◽  
Global Climate Models ◽  
Near Surface ◽  
Wind Speeds ◽  
The North ◽  
Seasonal Wind ◽  
Projected Changes

Abstract Future changes in geostrophic winds over Europe and the North Atlantic region were studied utilizing output data from 21 CMIP5 global climate models (GCMs). Changes in temporal means, extremes, and the joint distribution of speed and direction were considered. In concordance with previous research, the time mean and extreme scalar wind speeds do not change pronouncedly in response to the projected climate change; some degree of weakening occurs in the majority of the domain. Nevertheless, substantial changes in high wind speeds are identified when studying the geostrophic winds from different directions separately. In particular, in northern Europe in autumn and in parts of northwestern Europe in winter, the frequency of strong westerly winds is projected to increase by up to 50%. Concurrently, easterly winds become less common. In addition, we evaluated the potential of the GCMs to simulate changes in the near-surface true wind speeds. In ocean areas, changes in the true and geostrophic winds are mainly consistent and the emerging differences can be explained (e.g., by the retreat of Arctic sea ice). Conversely, in several GCMs the continental wind speed response proved to be predominantly determined by fairly arbitrary changes in the surface properties rather than by changes in the atmospheric circulation. Accordingly, true wind projections derived directly from the model output should be treated with caution since they do not necessarily reflect the actual atmospheric response to global warming.

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