Shear phenomena in ice-thrust gravels, central Alberta

1978 ◽  
Vol 15 (2) ◽  
pp. 277-283 ◽  
Author(s):  
E. A. Babcock ◽  
M. M. Fenton ◽  
L. D. Andriashek
Keyword(s):  
Ice Sheet ◽  
Coarse Sand ◽  
Moderate Intensity ◽  
Ice Pressure ◽  
Intense Shear

Pressures exerted by the continental ice sheet produced sheared zones and a pervasive crushing of strong quartzite clasts in preglacial Saskatchewan Gravels of central Alberta. Where deformation is of moderate intensity clasts have fractured at points of impingement with other clasts, and clasts of 3–6 cm in the longest dimension are most likely to be shattered. In zones of intense shear nearly all clasts larger than coarse sand have been crushed and drawn out into lensoid masses.An index of fracturing was devised to measure the degree of ice pressure induced deformation where the gravels show no evidence of having been disturbed. A model that defines possible conditions at the time of deformation is presented.

Tracking Late Quaternary ice sheet dynamics by multi-proxy detrital mineral U-Pb analysis: A case study from the Odyssea contourite, Ross Sea, Antarctica

2020 ◽  
Author(s):  
Roland Neofitu ◽  
Chris Mark ◽  
Michele Rebesco ◽  
Renata Giulia Lucchi ◽  
Nessim Douss ◽  
...  
Keyword(s):  
Ross Sea ◽  
Late Quaternary ◽  
Ice Sheet ◽  
Source Area ◽  
Coarse Sand ◽  
Turbidity Currents ◽  
Provenance Analysis ◽  
Geophysical Research ◽  
Antarctic Ice Sheet ◽  
Volcanic Material

<p>Late Quaternary Antarctic ice-sheet instability is recorded by ice-rafted debris (IRD) in mid- to high-latitude marine sediment, especially during marine isotope stages (MIS) 2-3, but drivers of this instability remain enigmatic (Labeyrie et al., 1986). A key step in resolving this puzzle is to determine the location of iceberg calving sites, thus highlighting ice sheet sectors exhibiting repeated instability. Single-grain U-Pb provenance analysis applied to clastic IRD provides a suitable high-resolution tool for this task, and also permits discrimination of continental IRD from volcanic material. The application of multiple proxies (apatite, rutile, and zircon) is critical in order to reduce source area fertility biases: for example, the near exclusive occurrence of zircon in felsic-intermediate igneous rocks (e.g., Hietpas et al., 2010).</p><p>Here, we present detrital apatite, zircon, and rutile U-Pb data from samples taken from a gravity core from the Odyssea contourite drift system, located on the margin of the Ross Sea (Rebesco et al., 2018) and deposited during MIS2-3. Contourites are marine clastic sediment deposits forming by along-slope, bottom currents reworking of fine-grained (clay-silt) sediments delivered by down-slope sedimentary processes (e.g. meltwaters, turbidity currents, debris flows). Crucially, contourite targetting eliminates the challenge of distinguishing IRD from coarse (sand-gravel) turbidite material in basin deposits, as ice-sheet instability is also associated with turbidite production at glaciated shelf margins (e.g., Bart et al., 1999).</p><p>We couple our analysis with the multi-proxy sediment analyses previously performed by Lucchi et al. (2019). We consider the implications of our data for the advance and retreat of the Antarctic Ice Sheet during MIS 2-3, and discuss the further applicability of our multi-proxy approach around Antarctica.</p><p>Bart, P.J, et al., 1999, Journal of Sedimentary Research, v. 69, p. 1276–1289, doi:10.2110/jsr.69.1276.</p><p>Hietpas, J, et al., 2010, Geology, v. 38, p. 167–170, doi:10.1130/G30265.1.</p><p>Lucchi, R.G, et al., 2019. EGU General Assembly 2019, Vienna April 7<sup>th</sup>–12<sup>th</sup>, Geophysical Research Abstracts Vol. 21, EGU2019-10409-1</p><p>Rebesco, M, et al., 2018, preliminary results, in POLAR 2018 SCAR/IASC Open Science Conference, v. GG2 Arctic, p. 14133.</p><p>Labeyrie, L, et al., 1986, Nature, v. 322, p. 701–706.</p>

Ice Pressure Sensor Inclusion Factors

1981 ◽  
Vol 103 (1) ◽  
pp. 82-86 ◽  
Author(s):  
A. C. T. Chen
Keyword(s):  
Sea Ice ◽  
Pressure Distribution ◽  
Pressure Sensor ◽  
Pressure Measurement ◽  
Measurement Data ◽  
Ice Sheet ◽  
Field Tests ◽  
Approximate Equation ◽  
Analytical Work ◽  
Ice Pressure

The inclusion of a pressure sensor in an ice sheet will disturb the pressure distribution in the ice sheet. The ratio of undisturbed ice pressure to the pressure felt by the sensor, defined herein as the inclusion factor, is required in interpreting the ice pressure measurement data. An approximate equation which expresses the inclusion factor in terms of the geometry of sensor and the sea ice/pressure sensor stiffnesses ratio is proposed in this study. Some results of analytical work and field tests which were performed to evaluate the accuracy of this expression are also presented. These results demonstrate the validity of the proposed inclusion equation.

Field In-Ice Pressure Sensor Response Tests

1983 ◽  
Vol 105 (1) ◽  
pp. 6-11
Author(s):  
A. C. T. Chen ◽  
J. S. Templeton
Keyword(s):  
Pressure Sensor ◽  
Data Reduction ◽  
Broad Class ◽  
Applied Pressure ◽  
Pressure Sensors ◽  
Ice Sheet ◽  
Sensor Response ◽  
Sensor Output ◽  
Reduction Procedure ◽  
Ice Pressure

An ice pressure sensor has been designed and built at Exxon Production Research Company (EPR) to measure the pressure in an ice sheet. Laboratory and analytical studies were performed to establish a data reduction procedure to relate the pressure sensor output to the pressure in the ice sheet. However, because of the complex mechanical behavior of sea ice, the present experiment was conducted to validate this data reduction procedure. The validated procedure is considered applicable to a broad class of embedded ice pressure sensors. Field in-ice pressure sensor response tests were conducted near Prudhoe Bay, Alaska, between February and April of 1978. Twenty-two tests were conducted on three test blocks of ice to investigate the in-ice response of three ice pressure sensors. An ice block measuring 10 ft by 20 ft and of full thickness of the natural annual ice was cut free from the surrounding ice sheet after the pressure sensor was installed at the center of the block. This ice block was loaded by an in-situ hydraulic ice loading device capable of delivering approximately two million lb of load. The pressure sensor output and the test load were monitored continuously during each test so that the pressure sensor output could be compared directly to the corresponding applied pressure. The test results indicated ratios of applied ice pressure to measured sensor pressure within the range hindcast by theoretical analysis.

The Distribution of Ice Pressure Acting on Offshore Pile Structure and the Failure Mechanics of Ice Sheet

1987 ◽  
Vol 109 (1) ◽  
pp. 85-92 ◽  
Author(s):  
S. Tanaka ◽  
H. Saeki ◽  
T. Ono
Keyword(s):  
Aspect Ratio ◽  
Strain Rate ◽  
Local Buckling ◽  
Ice Sheet ◽  
Field Tests ◽  
Ice Thickness ◽  
Economic Factors ◽  
Failure Mechanics ◽  
Ice Pressure ◽  
Ice Force

The total ice force acting on offshore pile structures, located in cold regions, has already been investigated by many researchers. Few papers, however, have described the distribution of ice pressure on the structures and the failure mechanics of ice sheet. It is necessary to study them in order to design the pile structures, keeping in mind safety and economic factors. The results of our experiments on failure mechanics of an ice sheet are useful for dynamic analysis. For analysis of stress and, especially, local buckling of structures, it is essential to examine the distribution of ice pressure acting on the structures. This paper describes a systematic study of these aspects through field tests with three rectangular piles (20, 40, 60 cm in width) in Saroma Lagoon in Hokkaido, Japan’s northernmost island, to clarify the effect of aspect ratio. It is clear from our experiments on ice pressure that the distribution of ice pressure can be classified into two types according to the strain rate ε˙ (= V/4B, V: penetration velocity of piles, B: pile width) defined by Michel and Toussaint [1] in each aspect ratio, B/h (h: ice thickness). It is our hypothesis that the failure periods of ice sheet are determined by the aforementioned strain rate and the aspect ratio.

scholarly journals Rock debris in an Antarctic ice shelf

2012 ◽  
Vol 53 (60) ◽  
pp. 235-240 ◽  
Author(s):  
K.W. Nicholls ◽  
H.F.J. Corr ◽  
K. Makinson ◽  
C.J. Pudsey
Keyword(s):  
Sea Water ◽  
Ice Sheet ◽  
Radar Data ◽  
Coarse Sand ◽  
Potential Mechanism ◽  
Ice Shelf ◽  
Ice Streams ◽  
History Of ◽  
Seaward Edge

AbstractWe have discovered a band of stones and coarse sand in the Ronne Ice Shelf, Antarctica, some 60 m above the ice shelf’s base, 40 km from its seaward edge and 420 km from the point where the ice originally went afloat. A study of ice-sounding radar data from across the Ronne Ice Shelf has revealed other areas likely to contain debris in significant quantities. It appears that basal debris at the margins of ice streams feeding the ice shelf can be buried in the ice shelf by sea water freezing-on at the ice-shelf base. These findings are evidence for a mechanism active in a present-day ice-sheet/shelf system, which enables icebergs to transport large volumes of ice-rafted debris, and which also provides a potential mechanism for the formation of ice rises near ice fronts. We anticipate that a seismics study of debris melted from the ice shelf and deposited beneath will provide a valuable control on the history of ice-shelf–ocean interactions.

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