Landscape analysis, mapping, sedimentology, shallow geophysics, and borehole data are integrated to better understand the complex landform-sediment geometries and event sequences of the Oak Ridges Moraine, southern Ontario. A model for the origin of the Oak Ridges Moraine is based on the recognition that the moraine is built on a high-relief, erosional surface (unconformity) consisting of drumlin uplands and a network of deep, steep-walled, interconnected valleys (tunnel channels). The development of the moraine is thought to have occurred in four stages: I, subglacial sedimentation; II, subaqueous fan sedimentation; III, fan to delta sedimentation; IV, ice-marginal sedimentation. The model traces the transition from subglacial to proglacial conditions during moraine formation and examines the order and timing of sedimentation. It is thought that the early stages of moraine construction are better exposed in the east; in the west, these stages are buried by later stages.
A geological model is presented for the glacial deposits of the Oak Ridges Moraine area of southern Ontario. The model contains four units as well as incised channels dissecting the strata. Channels eroded through the Newmarket Till, a regional aquitard, provide hydraulic connection between the aquifers of the overlying Oak Ridges Moraine and those of the underlying lower drift. Buried channels filled with silt, sand, and gravel, and preferentially oriented north-northeast-southsouthwest, are indicated by drill core and seismic reflection profiles. The model, with two successful case studies, has significant implications for groundwater resource development in the Greater Toronto Area. Groundwater flow to the lower drift may occur through channels so that groundwater resources in the lower drift may be more productive than previously suggested. Gravel sequences within channels may be targets for high yield wells. Further investigations are required to examine buried channel locations, distribution, and sediment fill.
Archival drilling records from water wells, geotechnical, mineral exploration, and hydrogeological studies provide subsurface information for regional geological and hydrogeological investigations. This paper evaluates methods by which water well material descriptions may be standardized. In Ontario, material descriptions are reported in three attribute fields using 82 terms, thus theoretically permitting over 500 000 permutations. Materials descriptions are rationalized to ten classes then reclassified according to two methods, 1) first-attribute method (FAM), and 2) rule-based method (RBM). The first-attribute method is presently applied by hydrogeologists in southern Ontario and uses only the first attribute field; it is a simple, effective method able to broadly delimit aquifers and nonaquifers. The rule-based method applies conditional rules developed from regional geological models. This method is more geologically accurate, and is recommended where water well data are to be integrated into geological and hydrogeological investigations. Successful applications are summarized and general recommendations made. Résumé : Des données provenant de forage de puits d'eau et d'études géotechniques, hydrogéologiques et de prospection minière, renseignent sur les conditions souterraines nécessaires aux études géologiques et hydrogéologiques régionales. Le présent article évalue les méthodes permettant de normaliser les descriptions des matériaux des puits d'eau. En Ontario, les descriptions de matériaux sont consignées dans trois champs d'attributs à l'aide de 82 termes, ce qui, théoriquement, permet de faire plus de 500 000 permutations. La rationalisation des descriptions de matériaux a permis de distinguer dix classes qui ont par la suite été reclassées selon deux méthodes : (1) la méthode des premiers attributs et (2) la méthode basée sur des règles. La méthode des premiers attributs, actuellement appliquée par les hydrogéologistes dans le sud de l'Ontario, utilise uniquement le premier champ d'attributs. Il s'agit d'une méthode simple et efficace pouvant délimiter grossièrement les formations aquifères et non aquifères. La méthode basée sur des règles applique des règles conditionnelles élaborées à partir de modèles géologiques régionaux. D'un point de vue géologique, cette méthode est plus précise. Il est recommandé de l'appliquer là où les données sur les puits d'eau doivent être intégrées aux études géologiques et hydrogéologiques. Les applications réussies sont présentées brièvement dans le présent article, lequel contient également des recommandations d'ordre général. 1 Contribution to the Oak Ridges Moraine NATMAP project
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