scholarly journals 3D Probabilistic Modelling and Uncertainty Analysis of Glacial and Post-Glacial Deposits of the City of Saguenay, Canada

Geosciences ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 204
Author(s):  
Mohammad Salsabili ◽  
Ali Saeidi ◽  
Alain Rouleau ◽  
Miroslav Nastev

Knowledge of the stratigraphic architecture and geotechnical properties of surficial soil sediments is essential for geotechnical risk assessment. In the Saguenay study area, the Quaternary deposits consist of a basal till layer and heterogeneous post-glacial deposits. Considering the stratigraphic setting and soil type heterogeneity, a multistep stochastic methodology is developed for 3D geological modelling and quantification of the associated uncertainties. This methodology is adopted for regional studies and involves geostatistical interpolation and simulation methods. Empirical Bayesian kriging (EBK) is applied to generate the bedrock topography map and determine the thickness of the till sediments and their uncertainties. The locally varying mean and variance of the EBK method enable accounting for data complexity and moderate nonstationarity. Sequential indicator simulation is then performed to determine the occurrence probability of the discontinuous post-glacial sediments (clay, sand and gravel) on top of the basal till layer. The individual thickness maps of the discontinuous soil layers and uncertainties are generated in a probabilistic manner. The proposed stochastic framework is suitable for heterogeneous soil deposits characterised with complex surface and subsurface datasets.

2013 ◽  
Vol 54 (64) ◽  
pp. 10-20 ◽  
Author(s):  
Andrew J. Stumpf ◽  
Ahmed Ismail

Abstract High-resolution seismic reflection (HRSR) data acquired over the Pesotum Bedrock Valley in central Illinois, USA, helped construct the seismic stratigraphy of a valley fill and the overlying sediments. Integrating these data with drilling and borehole geophysics allowed us to develop a seismo-stratigraphic classification for sediments on undulating and folded bedrock. Seven seismo-stratigraphic units that overlie the bedrock surface were characterized. Seismic units A and B include glacial sediments of multiple Pleistocene glaciations above the Pesotum Bedrock Valley, which completely mask the feature. Seismic units C–F, the valley fill, primarily include tills and glacial lake sediment deposited during the earliest Pleistocene glaciations and preglacial alluvium and colluvium that is draped over in situ weathered bedrock. The preservation of conformable-lying glacial and preglacial deposits and paucity of sand and gravel in the buried valley strongly indicate that little or no incision by glacial meltwaters has occurred. These observations contrast markedly with interpretations from buried valleys elsewhere in North America and northern Europe where valley fills contain significant deposits of sand and gravel in tunnel valleys. The HRSR data assisted the characterization and analysis of heterogeneous sedimentary sequences over a buried valley where existing subsurface information was limited. The extent of Pleistocene-age glacial lakes is inferred from the lateral continuity of silt and clay units.


2021 ◽  
Author(s):  
Daniel Le Heron ◽  
Bethan Davies ◽  
Lars Scharfenberg ◽  
Christoph Kettler ◽  
Michael Ketterman ◽  
...  

<p>Ongoing monitoring of the Gepatsch Glacier, Tirol (Austria) consists of a multifaceted, interdisciplinary project which aims to characterise short term (diurnal in the summer melt season) and longer term (annual to decadal) changes to the glacier snout and forefield in the context of a rapid retreating valley glacier. The glacial valley and forefield comprises amphibolites, para- and orthogneisses that have been smoothed and striated into whalebacks, compound bedrock-sediment bedforms (crag and tail structures), flutes, and annual moraines. The glacial sediments and landforms are undergoing incision and terrace development by meltwater streams. As part of a long term goal to characterise the rates of erosion, sedimentation, and re-deposition, we return to the same site each year in mid-July to collect airborne data with an UAV (Mavic Pro drone) that allows us to produce orthophotos and digital elevation models. We compute the daily and annual elevation changes, allowing us determine zones of erosion and deposition. Measureable evidence for erosion of flutes in the immediate glacial forefield has occurred over a 12-month time period. Till deposited within the last 20 years has undergone substantial mass wasting and re-deposition as subaerial mass flows, or reworked into stream deposits. The lee side of many whaleback structures completely lacks subglacial sediment, and contains instead a sand and gravel deposit interpreted to result from waterlain deposition. Thus, this case study area offers insight into the rates of erosion and deposition in a complex, proglacial setting, allowing some of these processes to be quantified for the first time. This approach is expected to yield a better understanding of the preservation potential of proglacial sedimentary facies, and hence their preservation potential in Earth’s sedimentary record.</p>


2018 ◽  
Vol 91 (1) ◽  
pp. 234-249 ◽  
Author(s):  
William W. Shilts ◽  
Olivier J. Caron

AbstractThe Chaudière River region in the Appalachian Mountains of eastern Canada is approximately 700 km north of the southernmost Pleistocene glacial deposits in New York and New Jersey. Detailed compositional analyses of glacial and non-glacial sediments from stratigraphic exposures and more than 40 boreholes drilled to bedrock provide a compositionally constrained record of glacial events, which include deposits of one Marine Oxygen Isotope Stage (MIS) 6 and two post-MIS 5 glaciations. The glacial and associated proglacial deposits rest on compositionally distinctive, preglacial saprolite that is preserved in deeper valleys. These observations constrain interpretations of the glacial/Pleistocene history of the eastern United States and Canada. The fact that there is no unequivocal evidence of pre-MIS 6 till in the Chaudière River region, while there are well-documented pre-MIS 6 glacial deposits south of there and in the American Midwest, also has major climatic implications. The Laurentide Ice Sheet and its ancestors must have been more robust in the west in the early Pleistocene and in the east most recently.


2020 ◽  
Vol 99 (1-2) ◽  
pp. 62-72
Author(s):  
Svitlana Pyasetska

The article deals with the question of the duration of the preservation and destruction phase which were calculated for ice-free periods of the category of SHP and were observed on the territory of Ukraine in the month of the cold period of the year during certain periods 1991–2000, 2001-2010 and 2011-2016. It was established that the duration of the preservation phase and the destruction of ice-oily deposits in the category of SHP is very volatile and ranges from near-instant destruction after reaching a maximum diameter of several hours or several dozen hours. However, there are cases where the duration of this phase can be 4 days in a row and more than several hundred hours. The study found that for the most part during the investigated period, the glacial deposits of the SHP category were dominated by non-prolonged conservation and degradation phases, regardless of the region where the sediment was formed, and regardless of the overall duration of the sediment itself, which could be significant. In 2001–2010 and 2011–2016, unlike in the period of 1991-2000, in January and December, the number of cases of ice-ousted categories of SHP increased. Moreover, in January, especially in 2011–2016, the number of cases with a significant duration of the phase of preservation and destruction of ice deposits of the category of SHP was increased. From the above we can draw a number of conclusions, namely: – During 1991–2000, the phases of preservation and destruction of ice-clay deposits in the category of HPAs were mostly non-prolonged and ranging from several hours to several dozen hours. The most prolonged phases of preservation and destruction of deposits of iced ice of category SHHA were in cases of sediments in Lower Zirgozakh in January 1996, in March 1998 in Kropivnitsky and most often in November 1999 in Gadyach, Dolynska, Komissarivka, Mariupol, Prisheby, and also in 2000 It is in Novodnistrovsk, Separate, Lyubashevtsi, Serbs, Voznesensk, December 1997 in Loshkarivka, Kryvy Rih, Nikopol, Lyubashevtsi, Prisheb and especially in Donetsk. – In 2001–2010, the amount of ice-cream deposits in the category of SHP increased slightly. In addition, the duration of the preservation and destruction phase compared to the previous period changed slightly, taking into account the individual months. So, in January, along with the relatively long phases of preservation and destruction of ice-clay deposits of the category of SHP (up to several dozen hours), in 2010 deposits with very long phases of conservation and destruction in Debaltsevo and especially in Mysovoye were observed. In December of this period, the long phases of preservation and destruction of deposits of iced ice of category SHP were observed in 2004 in Dar’yivka, and in 2008 in Vinnitsa and Ovruch. In the remaining months, the duration of the conservation and destruction phase was overwhelmingly within a few hours, at least to several dozen golds (11–25 hours) – Unlike in the years 1991-2000 and 2001-2010, in January the number of cases of ice deposits of the category of SHP increased in the five-year period of 2011–2016. They met practically in most regions. Significantly increased cases with them, where the duration of the preservation and destruction phase was significant and exceeded the duration of 4 consecutive days. Such cases were observed in January 2013 in Rava-Ruska, Kamianets Buzka and Poltava, in January 2014 – in Rava-Ruska, Ternopil, Amvrosiyivka, Rosdilna, Mykolayiv, Ochakov, and Simferopol. In December 2012, a similar accident happened in Evpatoria.


1933 ◽  
Vol 70 (5) ◽  
pp. 208-232 ◽  
Author(s):  
T. Neville George

A general description of the drifts of Gower has been given in the memoirs of the Geological Survey,1 in which, however, no distinction was made between deposits of different ages. But it has long been known that there are at least two series of Glacial deposits in South-Western Britain, though until recently their relative extents were only surmised: in South Wales the relations of the drifts have been determined only within the last few years.2 As a consequence of this recent work it is clear that the Newer Drift does not extend into Gower much beyond the Sketty-Fairwood-Mumbles neighbourhood, and while the margin of this Newer Drift as determined by Charlesworth may be questioned in detail, especially further west along the Towy Valley,3 yet it is at least certain that the greater part of Gower is (or was) covered by Boulder Clay and gravels of the older drift. The general absence of deposits characteristic of terminal moraines, the “ mature ” topography, and the great amount of erosion that the drift has suffered are sufficiently distinctive, even apart from the extensive mounds of sand and gravel that mark the boundary of the Newer Drift further east.


The Quaternary sequence of an area of 120 km 2 , centred on Market Bosworth in Leicestershire, is described. The entire sequence is regarded as the product of the Wolstonian stage. The bedrock surface of the area shows the buried Hinckley valley, which opened southwards into the proto-Soar basin. The first evidence of sedimentation onto this surface in western Leicestershire is the Basal Till which betokens an ice advance prior to the accumulation of the extensive glacio-lacustrine member, the Bosworth Clays and Silts. This proglacial lake is interpreted as being the northern continuation of lake Harrison, which was initiated on the retreat and stagnation of ice, following the deposition of the Basal Till. A readvance of ice led to the deposition of a large sandur represented by the Cadeby Sand and Gravel and followed by a till sequence comprising the Pennine and Chalky Tills of northwestern and northeastern provenance, respectively.


1997 ◽  
Vol 43 (145) ◽  
pp. 446-454 ◽  
Author(s):  
John F. Hiemstra ◽  
Jaap J. M. Van Der Meer

AbstractGenetic classification of glacial deposits still proves to be highly controversial. In many cases, it remains unclear whether a particular sediment has been sub-glacially deformed. In the present paper it is suggested that micromorphological research is helpful where current techniques fail to lead to unambiguous interpretations. It is argued that the occurrence of fractured grains in glacial sediments is indicative of subglacial shearing and that such grains may be used as diagnostic evidence of glaciotectonism. Deformational mechanisms associated with the fracturing process are outlined and explained, using a series of thin sections from Wijnjewoude, The Netherlands.


Author(s):  
Carlos Manuel Ramirez López ◽  
Martín Montes Rivera ◽  
Alberto Ochoa ◽  
Julio César Ponce Gallegos ◽  
José Eder Guzmán Mendoza

This research presents the application of Empirical Bayesian Kriging, a geostatistical interpolation method. The case study is about suicide prevention. The dataset is composed of more than one million records, obtained from the report database of the Emergency Service 911 of the Mexican State of Aguascalientes. The purpose is to get prediction surfaces, probability, and standard error prediction for completed suicide cases. Here, the variations in the environment of suicide cases are relative to and dependent on economic, social, and cultural phenomena.


2017 ◽  
Vol 44 (1) ◽  
pp. 49-65 ◽  
Author(s):  
Anna R Agatova ◽  
Roman K Nepop

AbstractGeomorphological evidence of at least two Pleistocene glacial epochsis noted within the Chagan-Uzun river basin, SE Altai. A review and analysis of all available absolute dates for reference Chagan section is presented. The highest correlation amongst all TL dates is observed for the lens of glacio-lacustrine sediments – the most suitable among glacial deposits for luminescence dating, and indicates its possible Middle Pleistocene age. IRSL dates obtained from feldspar indicate a Middle Pleistocene age of moraines already in the upper part of the section. The small number of obtained IRSL dates does not allow making geochronological reconstructions of the Pleistocene glaciations, but gives the possibility for further experiments with different variation of OSL (IRSL) techniques. Strong low temperature peak in TL signal and strong response to IR stimulation are specific regional quartz features, which could be explained by combination of short transportation distance and low number of depositional cycles for mineral grains. Available radiocarbon dates of carbonate concretions from this section are not related to the age of moraine sedimentation and most likely indicate the period of the Chagan river incision into the ancient glacial deposits.This study has shown that TL method is not valid for dating glacial sediments and TL dates cannot be utilized as chronostratigraphic markers. Generally, the Chagan section could hardly serve as a reference section for the Altai stratigraphy; available depositional correlation schemes for the Russian Altai and Siberia which are based on several TL dates obtained in the last century needs to be improved.


1981 ◽  
Vol 47 ◽  
pp. 137-146 ◽  
Author(s):  
Roger Miket

The pit alignment at Milfield North, discussed in the preceding paper, is one of six alignments revealed in the Milfield Basin within the last decade. All discoveries have so far been confined to the sands and gravels of the former delta surface, and whereas additional examples, as well as their extension onto the heavier loams overlying the sandstone series, remain to be found, so crisp has been the definition by means of intensive aerial survey in this valley, that only a limited enlargement of the present distribution pattern by this means is anticipated. The characteristics of the individual alignments are as follows:1. Ewart 1. NT95343209 to NT96103162An irregular line of closely spaced pits that for most of its observable course follows the crest of a gentle but marked elevation in the sand and gravel-terrace. Two interruptions are visible towards its eastern end before it angles southwards to disappear into a wood. Observed over 1100 m.Source: Cambridge University Collection. BDE35, BDE36, BKC40.Museum of Antiquities, Newcastle upon Tyne. A1656–1662.2. Ewart 2. NT95353165 to NT95803159Lying to the south of Ewart 1 and running broadly parallel to it. The pit sizes and spacing is similar to Ewart 1 although their inter-relationship is obscured at their eastern end by a plantation. Ewart 2 fades away at its western extremity. Observed over 300 m.Source: Cambridge University Collection. BDE35, BDE36.


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