100 research outputs found
Quaternary landform and sediment analysis of the Alliston area (southern Simcoe County), Ontario, Canada
No full textUrban expansion and agricultural growth are placing significant stresses on existing groundwater reserves hosted within Quaternary sediments in southern Ontario. Preserving the quality and quantity of groundwater resources requires a detailed knowledge of the three-dimensional distribution of subsurface geologic units. In this study, integrated analysis of surficial sediment exposures, geophysical and remotely-sensed data, and fully-cored boreholes in the Alliston region of southern Ontario has allowed for the identification of landform-sediment associations, or landsystems, which can be used to predict the nature of subsurface sediment types and to assist with the reconstruction of paleoenvironmental change in the region. The landsystems identified in the Alliston region can also be used as a foundation for the development of a stratigraphic framework for hydrogeological investigations. Nine landsystems were identified in the study area and include: i) bedrock escarpment, ii) gravel bench, iii) V-shaped valleys and fills, iv) streamlined uplands, v) low-relief uplands, vi) upland plains and scarps, vii) erosional amphitheatres, viii) hummocky terrain, and ix) lowland plains. These landsystems record the changing distribution of glacial, ice-marginal, glaciofluvial, glaciolacustrine, and post-glacial depositional systems that affected the region during the late Quaternary. The landsystems analysis approach provides a useful framework for discerning the spatiotemporal relationship of a complex suite of depositional systems. Analysis of the distribution and internal composition of landsystems in the study area has allowed the development of a preliminary risk assessment map for aquifer vulnerability in the region. Detailed analysis of 56 outcrop exposures in cutbanks along the Nottawasaga River within the former Lake Algonquin plain has led to the identification of six lithofacies associations (FA 1–6) that present a detailed record of environmental change during the deglacial period. The stratigraphy is floored by the Late Wisconsin Newmarket Till (FA 1) which is locally overlain by ice-proximal debris flows (FA 2). These glacial sediments are overlain by glaciolacustrine silt rhythmites (FA 3) that pass upwards into deltaic sand (FA 4) and channelized fluviodeltaic sand and gravel (FA 5). Lying above the fluvial deposits and capping the succession are widespread sand and silt rhythmites (FA 6), which coarsen up-section. These six facies associations provide a record of changing environmental conditions that existed during deglaciation of the region and give valuable insights into the nature of the evolution of glacial lakes Schomberg, Algonquin, and Nipissing. The deglacial environmental changes described from southern Simcoe County may be valuable analogues for the interpretation of regional-scale events that occurred in extensive lake basins in other formerly glaciated regions. Qualitative observations of groundwater discharge from sediment facies at outcrop faces along the Nottawasaga River have yielded important data on the internal heterogeneity of subsurface units. These data can be used to identify possible preferential groundwater flow pathways through both aquifer and aquitard units in the region. Understanding the geometry and interconnectedness of these subsurface sediments is essential for planning future water supply for growing urban communities and agricultural irrigation needs in the region and for the prediction of contaminant migration pathways.Master of Science (MSc
The pre-Late Wisconsin stratigraphy of southern Simcoe County, Ontario: Implications for ice sheet build-up, decay, and Great Lakes drainage evolution
No full textRecent three-dimensional mapping investigations in southern Simcoe County, Ontario allow refinement of the existing regional stratigraphic framework. Analysis of 25 continuously-cored boreholes has revealed a complex but consistent sediment succession that provides a record of the last two glacial cycles (Marine Isotope Stages 1-6). Five stratigraphic units (SU 1-5) comprise the pre-Late Wisconsin record. The stratigraphy is floored by a presumed Illinoian glacial complex consisting of a lower, coarse-grained till (SU 1), locally overlain by stratified glaciolacustrine and glaciofluvial sediments (SU2), but more commonly capped by a stone-poor, fine-grained till (SU 3) of the Georgian Bay lobe. A widespread subaerial unconformity developed on the upper surface of SU3 contains organic-bearing, non-glacial deposits (SU 4) ranging between 54 800 Âą 3000 (considered beyond the limits of radiocarbon dating) and 37 450 Âą 590 14C yr BP. SU 4 is abruptly overlain by a thick succession of rhythmically laminated lacustrine muds graded upwards into glaciolacustrine silts and clays interrupted by regionally continuous sand bodies (SU 5). The succession is capped (and locally truncated) by Late Wisconsin Newmarket Till. The sedimentary record of southern Simcoe County is correlated with other well-studied reference sections in southern Ontario and contains information that informs reconstructions of former ice extents in the lower Great Lakes region following the Illinoian glaciation. Several sediment units host aquifers, but limited thickness and spatial extent, as well as issues with naturally-occurring dissolved gases and solids, restrict their use for groundwater supply.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
STRATIGRAPHIC ANALYSIS OF LATE WISCONSIN AND HOLOCENE GLACIOLACUSTRINE DEPOSITS EXPOSED ALONG THE NOTTAWASAGA RIVER, SOUTHERN ONTARIO, CANADA
No full textAnalysis of 56 outcrop exposures in cut banks along the Nottawasaga River in southern Simcoe County, Ontario, Canada, has led to the identification of eight stratigraphic units (SU1-8) that represent a record of changing environmental conditions during deglaciation and exhibit strong controls on shallow groundwater flow in the region. The stratigraphic succession is floored by the Late Wisconsin Newmarket Till (SU1) which is locally overlain by ice-proximal debris flow deposits (SU2). These glacial sediments are overlain by glaciolacustrine silt rhythmites (SU3) that pass upwards into deltaic sand (SU4) and channelized fluviodeltaic sand and gravel (SU5). Lying above the fluvial deposits are widespread interbedded glaciolacustrine sands and silt (SU6), which coarsen up-section toward the ground surface. The succession is locally capped by fluviodeltaic (SU7) and younger fluvial (SU8) deposits. These stratigraphic units record sedimentary environments that existed during deglaciation of the region and provide insight into the evolution of glacial lakes Schomberg and Algonquin, and the Nipissing phase of the upper Great Lakes. The environmental changes described from sediments along the Nottawasaga River provide insights into basin-scale events that occurred throughout the upper Great Lakes during deglaciation. Qualitative observations of groundwater discharge from sediments at outcrop faces are used to characterize the hydraulic function of the stratigraphic units as well as possible preferential groundwater flow pathways in the shallow subsurface.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
ONE PIECE OF THE PUZZLE: UNCOVERING THE GENESIS OF LARGE VALLEYS CUT INTO QUATERNARY SEDIMENT AND PALEOZOIC BEDROCK IN SOUTH-CENTRAL ONTARIO, CANADA
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NEW INSIGHTS ON GLACIAL LAKE EVOLUTION IN THE SOUTHEASTERN PART OF THE LAKE HURON BASIN BASED ON SURFICIAL SEDIMENT MAPPING, SEDIMENT DRILLING, AND REMOTELY-SENSED DATA IN SOUTHERN ONTARIO
No full textNIPISSING BARRIER STRATIGRAPHY EXPOSED ALONG THE NOTTAWASAGA RIVER IN WASAGA BEACH, ONTARIO
No full textAn analysis of foreign language lesson discourse : with special reference to the teaching of English in Tunisian secondary schools.
No full textIn this thesis a new model for the analysis of foreign language
lesson discourse has been developed. It draws on existing models but
provides flexibility by focusing on three levels: Frame, Move, Act.
An attempt has been made in this thesis to clarify further the domain
of pragmatics by looking at the various fields that have contributed to it.
This has led the author to (i) differentiate between foreign language
lesson discourse and other discourses and (ii) locate the new model in
relation to other approaches to discourse analysis. The foregoing
discussion has revealed to the author that many researchers and
theoreticians have misunderstood many key terms in pragmatics which have
contributed to unwarranted positions concerning the role of the teacher and
the importance of textbooks in the classroom.
A detailed analysis of discourse in eight English lessons in Tunisian
secondary schools (two in each of the four years) has been undertaken. The
results of the analysis reflect the influence of the textbooks and suggest
different degrees of benefit for the learner.
There are seven chapters in the thesis. Chapter One reviews the
theoretical foundations of the audiolingual method. Chapter Two discusses
Chomskyan theory and its influence on approaches to L2 learning and
teaching. Chapter Three deals with pragmatics, particularly its relevance
to second language learning studies and its importance for the analysis of
second language classroom discourse. Chapter Four looks at the
communicative approach to second language teaching and related developments
in second language acquisition studies. It also discusses Tunisian
learners' communication strategies. Chapter Five gives the reader a general
background about the Tunisian linguistic community and the educational
system there. It also discusses the textbooks used for the teaching of
English in Tunisian secondary schools. Chapter Six gives an account of the
procedure adopted for data collection and presents in detail the model for
the analysis of Tunisian foreign language lesson discourse. Chapter Seven
discusses the results of the quantitative analysis of the Tunisian foreign
language lesson discourses, and proposes some reforms.
The thesis contains a short introduction and conclusion, as well as
eight appendices where the orthographic transcription and analysis of each
lesson discourse is given.
Habib Abdesslem
Laurentide Ice Sheet configuration in southern Ontario, Canada during the last glaciation (MIS 4 to 2) from stratigraphic drilling and LIDAR-based surficial mapping
No full textRegional subsurface mapping of glacial depositional systems preserved in buried bedrock paleovalleys, and quantitative analysis of new LiDAR imagery of surface glacial landforms using machine learning techniques, when combined, are powerful tools for assessing the dynamics of the Laurentide Ice Sheet (LIS) during the last (Wisconsinan) glaciation in southern Ontario. While age dating of deposits preserved below Last Glacial Maximum tills (LGM: marine isotope stage (MIS) 2 < c.24 000 years B.P. (ybp)) is still sparse, newly available sedimentological data derived by cored drilling, combined with legacy outcrop data, identify thick (100 m+) successions of glaciolacustrine sediments and a lack of till(s), indicating that the ice sheet margin did not extend beyond the Niagara Escarpment at the western end of Lake Ontario, during the earliest phases of the glaciation (MIS 4) or the ensuing mid-Wisconsinan (MIS 3). Ice was able to extend into New York State blocking the Rome outlet to the Hudson Valley ponding deep proglacial lakes in the glacio-isostatically depressed Huron–Ontario–Erie basins recorded by thick glaciolacustrine sediments in paleovalleys. These were cannibalized by an expanding Late Wisconsinan ice sheet after ∼24 000 ybp recorded by extensive till sheets resting on a marked erosional unconformity, with drumlinized surfaces. Analysis and visualization of LiDAR data identifies discrete statistically validated flow sets of highly elongated streamlined bedforms (mega-scale glacial lineations (MSGLs)). These provide key evidence of a major reorganization of the ice sheet margin during deglaciation into lobate paleo ice streams shortly after 17 400 ybp. MSGLs are cut across earlier LGM drumlinized tills creating widespread “palimpsest” surfaces. At least two principal phases of fast ice flow can be identified, marked by large fluxes of sediment and the rapid building of large gravel and sand-dominated moraine complexes within interlobate depocentres, the largest glacial landforms in southern Ontario. Analysis of LiDAR data further reveals the common presence of DeGeer moraines where ice margins retreated in water, and iceberg scours. Future work using LiDAR mapping has the objective of fully documenting the number, extent, and timing of ice streams to enhance glaciological modelling when the ice sheet rapidly lost mass
PIECING IT TOGETHER: REGIONAL CORRELATIONS OF ICE MARGINS AND GLACIAL-PROGLACIAL LANDFORMS IN SOUTHERN ONTARIO
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