scholarly journals Seismo-Stratigraphy and Sedimentology of Holocene Sediments off Grande Rivière de la Baleine, Southeastern Hudson Bay, Québec

2007 ◽  
Vol 47 (2) ◽  
pp. 147-166 ◽  
Author(s):  
Nicole Gonthier ◽  
Bruno d’Anglejan ◽  
Heiner W. Josenhans
Keyword(s):  
Regional Distribution ◽  
Open Water ◽  
Glacial Till ◽  
Hudson Bay ◽  
Glacial Sediments ◽  
Reflection Seismic ◽  
Holocene Sediments ◽  
Seismic Records ◽  
Geochemical Analyses ◽  
Seismic Lines

ABSTRACT The regional distribution of Holocene sediments of eastern Hudson Bay off the Grande Rivière de la Baleine mouth was mapped using a grid of reflection seismic lines (approximately 300 km long and covering an area of approximately 800 km2) and data from 7 piston cores. Based on the seismic records and piston cores, 4 stratigraphic units overlying the Proterozoic bedrock (unit 1) were defined and interpreted: (unit 2) glacial till deposited by a westward flowing ice sheet, (unit 3) rhythmically bedded clays and silts presumably deposited in glacial Lake Ojibway, (unit 4) postglacial marine muds deposited in the Tyrrell Sea overlain by undifferentiated modern marine muds, and (unit 5) distal fluviodeltaic sediments from Grande Rivière de la Baleine. Similar stratigraphie units have been described onshore. Textural and geochemical analyses suggest that unit 3 rhythmites are true varves; dark "summer" laminae were deposited mainly by underflows during the open water season, and light "winter" laminae were deposited by overflows-interflows along thermal stratifications under a seasonal ice cover. Unit 5 covers approximately 400 km2 and occurs as a deltaic constructional wedge protruding as far as 11 km offshore of the Grande Rivière de la Baleine entrance with thicknesses reaching 30 m along the coast. It was deposited between 3500 BP and the present from remobilization of glacial sediments farther upstream due to river downcutting during emergence.

Eddy covariance flux measurements of momentum, heat and carbon dioxide in Hudson Bay at the onset of sea ice melt 

2021 ◽  
Author(s):  
Richard Sims ◽  
Brian Butterworth ◽  
Tim Papakyriakou ◽  
Mohamed Ahmed ◽  
Brent Else
Keyword(s):  
Carbon Dioxide ◽  
Gas Exchange ◽  
Sea Ice ◽  
Eddy Covariance ◽  
Open Water ◽  
The Arctic ◽  
Gas Transfer ◽  
Hudson Bay ◽  
Flux Measurements ◽  
Ice Fraction

<p>Remoteness and tough conditions have made the Arctic Ocean historically difficult to access; until recently this has resulted in an undersampling of trace gas and gas exchange measurements. The seasonal cycle of sea ice completely transforms the air sea interface and the dynamics of gas exchange. To make estimates of gas exchange in the presence of sea ice, sea ice fraction is frequently used to scale open water gas transfer parametrisations. It remains unclear whether this scaling is appropriate for all sea ice regions. Ship based eddy covariance measurements were made in Hudson Bay during the summer of 2018 from the icebreaker CCGS Amundsen. We will present fluxes of carbon dioxide (CO<sub>2</sub>), heat and momentum and will show how they change around the Hudson Bay polynya under varying sea ice conditions. We will explore how these fluxes change with wind speed and sea ice fraction. As freshwater stratification was encountered during the cruise, we will compare our measurements with other recent eddy covariance flux measurements made from icebreakers and also will compare our turbulent CO<sub>2 </sub>fluxes with bulk fluxes calculated using underway and surface bottle pCO<sub>2</sub> data. </p><p> </p>

scholarly journals Ice Thickness and Sea Depth Derived from Reflection-Seismic Measurements on the Central Part of Filchner-Ronne Ice Shelf, Antarctica

1988 ◽  
Vol 11 ◽  
pp. 14-18 ◽  
Author(s):  
J. Determann ◽  
F. Thyssen ◽  
H. Engelhardt
Keyword(s):  
Drill Hole ◽  
Ice Thickness ◽  
Ice Shelf ◽  
Reflection Seismic ◽  
Seismic Records ◽  
3D Processing ◽  
Seismic Measurements ◽  
Good Agreement ◽  
Made In

In January 1986, reflection-seismic measurements were made in the central part of Filchner-Ronne Ice Shelf, north of Henry and Korff ice rises, by a German oversnow traverse. With the help of a newly developed “ice streamer”, two people were able to obtain seismic records nearly every 5km over a distance of 150km within 3d. Processing of digitally recorded seismograms yielded profiles of ice thickness and sea depth. The ice thickness varies from 400 to 500 m and is in good agreement with the thickness of 465 m at a drill hole. The reflection-seismic results are comparable with those obtained from aerogeophysical measurements.

scholarly journals Holocene sediments of the Ustka Cliff (Northern Poland) in view of radiometric dating

2013 ◽  
Vol 40 (3) ◽  
pp. 187-194 ◽  
Author(s):  
Radosław Wróblewski ◽  
Stanisław Fedorowicz ◽  
Katarzyna Kamieńska
Keyword(s):  
Environmental Conditions ◽  
Glacial Till ◽  
Radiometric Dating ◽  
Aeolian Deposits ◽  
Baltic Coast ◽  
Northern Poland ◽  
Holocene Sediments ◽  
Southern Baltic ◽  
First Time ◽  
Research Studies

Abstract The cliff in Ustka is an active one. The area is one of the most eroded sea shores of the Polish coast. The Ustka Cliff mainly consists of Holocene sandy deposits, but its basis is built of glacial till and clay. Field search allowed to recognize the structure and sedimentary conditions of Holocene deposits exposed in the cliff. A comparison of dating results obtained for fossil soils and peat as well as aeolian deposits, using 14C and TL methods, respectively, with available literature records is presented. The evaluation of results obtained allowed to define three main dune-forming phases for the first time for this part of the Polish coast. During the research studies new data on the processes and environmental conditions was gained and the development of structure of the area during the last 10 thousand years was reconstructed. The analysis of available data from other sections of the southern Baltic coast shows that results obtained are age similar to those determined for the Łeba Spit. The research is part of a project concerning the geomorphology of the Ustka Bay.

scholarly journals Inorganic geochemistry data from Lake El'gygytgyn sediments: marine isotope stages 6–11

2014 ◽  
Vol 10 (2) ◽  
pp. 467-485 ◽  
Author(s):  
P. S. Minyuk ◽  
V. Y. Borkhodoev ◽  
V. Wennrich
Keyword(s):  
Environmental Changes ◽  
Ice Cores ◽  
Northeastern Russia ◽  
Rare Element ◽  
Elemental Ratios ◽  
Glacial Sediments ◽  
Inorganic Geochemistry ◽  
Fine Grained ◽  
Lake El’Gygytgyn ◽  
Geochemical Analyses

Abstract. Geochemical analyses were performed on sediments recovered by deep drilling at Lake El'gygytgyn in central Chukotka, northeastern Russia (67°30' N; 172°05' E). Major and rare element concentrations were determined using X-ray fluorescence spectroscopy (XRF) on the < 250 μm fraction from 617 samples dated to ca. 440 and 125 ka, which approximates marine isotope stages (MIS) 11 to 6. The inorganic geochemistry indicates significant variations in elemental composition between glaciations and interglaciations. Interglacial sediments are characterized by high contents of SiO2, Na2O, CaO, K2O, and Sr and are depleted in Al2O3, Fe2O3, TiO2, and MgO. An extreme SiO2 enrichment during MIS 11.3 and 9.3 was caused by an enhanced flux of biogenic silica (BSi). The geochemical structure of MIS 11 shows similar characteristics as seen in MIS 11 records from Lake Baikal (southeastern Siberia) and Antarctic ice cores, thereby arguing for the influence of global forcings on these records. High sediment content of TiO2, Fe2O3, MgO, Al2O3, LOI, Ni, Cr, and Zr typifies glacial stages, with the most marked increases during MIS 7.4 and 6.6. Reducing conditions during glacial times are indicated by peaks in the Fe2O3 content and coinciding low Fe2O3/MnO ratios. This conclusion also is supported by P2O5 and MnO enrichment, indicating an increased abundance of authigenic, fine-grained vivianite. Elemental ratios (CIA, CIW, PIA, and Rb/Sr) indicate that glacial sediments are depleted in mobile elements, like Na, Ca, K and Sr. This depletion was caused by changes in the sedimentation regime and thus reflects environmental changes.

scholarly journals Efficacy of Seismic Interferometry in Removing Surface Waves from Active Seismic Records

2021 ◽  
Author(s):  
Varun Kumar Singla ◽  
Ivan Lokmer
Keyword(s):  
Surface Waves ◽  
Seismic Interferometry ◽  
Coherent Noise ◽  
Seismic Surveys ◽  
Reflection Seismic ◽  
Reflection Data ◽  
Data Driven Approach ◽  
Seismic Records ◽  
Filtering Techniques

&lt;p&gt;While there are seismic techniques which make use of surface waves in imaging the subsurface, there are also those where these types of waves are considered coherent noise. Important examples where the surface waves may significantly degrade the obtained images include different types of reflection seismic surveys (e.g., shallow surveys for engineering, environmental and groundwater investigations, and deep surveys for imaging hydrocarbon reservoirs). In a strongly heterogeneous medium (encountered typically in onshore surveys), the conventional methods for attenuating these waves (such as f-k &quot;velocity&quot; filtering) often do not give satisfactory results.&lt;/p&gt;&lt;p&gt;Seismic interferometry is a data-driven approach that offers a viable alternative for removal of surface waves from active seismic records. In this approach, the reflection data of several sources is considered and for each source, the seismic signals at a pair of receivers are cross-correlated to produce the surface wavefield between the receivers. The cross-correlated waveforms are then summed over all the sources to obtain the &quot;interferometric&quot; signal for the considered receiver pair. During this summation, the reflection and non-physical events cancel out due to the variable differences in the travel times to the considered receiver pair from different sources. The &quot;interferometric&quot; signal consequently contains predominantly the surface waves and this makes it conducive for adaptive subtraction (or filtering) from the original records. This study investigates the efficacy of the commonly used filtering techniques in interferometry to remove the surface waves from active seismic records. For this, the reflection data of a complex 2-D elastic medium is simulated and the filtering techniques are applied to this data. The limitations of these techniques inferred from the quality of the filtered data are discussed and possible remedies to overcome them are suggested.&lt;/p&gt;

scholarly journals Polar Bear Distribution and Abundance on the Southwestern Hudson Bay Coast During Open Water Season, in Relation to Population Trends and Annual Ice Patterns

ARCTIC ◽  
2004 ◽  
Vol 57 (1) ◽  
Author(s):  
Ian Stirling ◽  
N.J. Lunn ◽  
John Iacozza ◽  
Campbell Elliott ◽  
Martyn Obbard
Keyword(s):  
Polar Bear ◽  
Open Water ◽  
Population Trends ◽  
Hudson Bay

A new interpretation of geological structure of Tempoku Coal Field by crooked-line survey

1992 ◽  
Vol 23 (2) ◽  
pp. 241
Author(s):  
O. Nakano ◽  
M. Endo ◽  
E. Ishii ◽  
H. Watanabe
Keyword(s):  
Large Scale ◽  
Geological Structure ◽  
Seismic Survey ◽  
Coal Field ◽  
Coal Seams ◽  
Reflection Seismic ◽  
Line Method ◽  
Northern Island ◽  
New Interpretation ◽  
Seismic Lines

Tempoku Coal Field is located in the northern area of Japan's northern island, Hokkaido. Here the exploration target, the Soya Coal-Bearing Formation, is of Tertiary age overlying Cretaceous basement. The regional structure of the area is characterised by a series of synclines and anticlines trending north-northwest, with several reverse faults. A suite of surveys was carried out in 1991, in the Asajino area in the central part of the coal field. The study included drilling, vertical seismic profiling, and trenching, as well as a reflection seismic survey with the crooked-line method, which is the subject of this paper. The crooked-line method was adopted because of the mountainous terrain of the area. The seismic lines were laid out along existing tracks and valleys. The main geological structure of the area had long been considered to be a monotonous series of folds. However, the 1991 survey revealed a large-scale thrust-related structure in the main coal seams, which presented clear reflectors. Together with the data from other surveys, a reinterpretation of the structure of the Asajino area is proposed.

scholarly journals Extensional shear zones as imaged by reflection seismic lines: the Larderello geothermal field (central Italy)

2003 ◽  
Vol 363 (1-2) ◽  
pp. 127-139 ◽  
Author(s):  
Andrea Brogi ◽  
Antonio Lazzarotto ◽  
Domenico Liotta ◽  
Giorgio Ranalli
Keyword(s):  
Central Italy ◽  
Shear Zones ◽  
Geothermal Field ◽  
Reflection Seismic ◽  
Seismic Lines
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