The Geological Survey of Canada (GSC) Aurora cored borehole intersects the Yonge Street aquifer (YSA), an important groundwater source in Ontario. The borehole, sited along a 7 km long seismic profile, was drilled in order to provide data to improve sustainable use and management of groundwater in Aurora well fields and the regional aquifer system. Results provide high-quality hydrostratigraphic reference data, geological context, and a prospecting model for this significant buried-valley aquifer. The improved conceptual hydrogeological model offers a plan to effectively stress and assess the YSA system. A 130 m sedimentary succession unconformably overlies subhorizontal Whitby shale and a low-relief bedrock surface with no defined valleys. Gas seeping from the shale is trapped in Thorncliffe Formation, a regional aquifer below confining aquitards. The regional aquifer occurs below ~209 m a.s.l. and is a 80 m thick, fining-upward, sand and gravel sequence. It appears to represent a portion of a northeast-southwest-oriented channel, esker, and subaqueous fan system that fed Thorncliffe Formation aquifer sediments to the south. The newly identified aquifer system occurs above a regional unconformity within the succession. A 25 m thick Newmarket Till and silt-clay rhythmite sequence confines this aquifer. This aquitard drapes into Aurora basin, a possible pre-existing sediment valley. High clay content in aquitard rhythmites may allow conductivity logs to map it as a marker horizon. The overlying Oak Ridges Moraine (ORM) aquifer occurs as a 30 m thick gravel-sand-mud sequence above a second regional unconformity within the succession. This channel fill sequence is thinner than nearby 100 m thick ORM channel sediments.

A large integrated data set of cores, outcrop data, and seismic transects from the mud-buried Vars-Winchester esker in the Champlain Sea basin, Canada, was studied to gain insight into how muddy glaciated basins fill with sediment, and how esker sedimentary systems contribute to this process.Three stratigraphic units-a till sheet over carbonate bedrock, the Vars-Winchester esker, and overlying Champlain Sea mud-are identified in the data set. The till is massive, mud rich, carbonate rich, and drumlinized. The esker is also carbonate rich, and rests erosively on till or bedrock. It consists of two elements, a narrow gravelly central ridge and a broad sandy carapace. Three units comprise the overlying mud package: gray carbonate-rich rhythmites, massive bioturbated mud, and carbonate-poor, red-andgray rhythmites.A sequence stratigraphic model is proposed to explain these observations. Emphasis is placed on gradual ice-front translation superimposed by rapid meltwater events. The esker is interpreted to have been derived from the underlying till by water that flowed through a subglacial conduit (R-channel), within which the narrow gravelly central ridge was deposited. Most mud and finer sand bypassed the conduit and was deposited proglacially on the floor of the Champlain Sea, first as sandy outwash and, farther basinward, as muddy carbonate-rich rhythmites. Gradual ice-front retreat superposed distal facies over proximal facies, generating the upward-fining succession that starts with the esker gravel and ends with muddy rhythmites. Most esker sediment appears to have been deposited during rapid, jokulhlaup-like floods that punctuated gradual retreat. Discharges are estimated to have been high, possibly on the order of several hundred to, perhaps more commonly, several thousand cubic meters per second. The chaotic and random-looking appearance of the resultant sedimentological signatures in the esker sensu stricto is sharply contrasted with the regularity of the muddy rhythmites. If the rhythmites are indeed correlative to the esker, which seems reasonable given their geochemistry and the fact that their volume scales to the volume of mud in the till, the flood events that deposited the esker must have been seasonally mediated, and the basin water must have attenuated the flood signal, resulting in a rhythmic "on-off" signature in more distal portions of the system. The regularity of the rhythmites does not betray the chaotic nature of the esker sensu stricto, and vice versa. Studying either one in isolation would lead to a very different "end-member" impression of how eskers form and how esker sedimentary systems operate during the infilling of glaciated basins.

The Pontypool borehole was drilled by Golder and Associates for the municipality of Kawartha Lakes. The Ontario Ministry of Environment provided funding for the initial drilling and geophysics. The borehole was terminated in bedrock at ~171 m depth and core was collected in 114 runs. The GSC completed bed-by-bed sediment logging of the core, grain size and total organic carbon analysis (TOC), and downhole geophysical logging. The core description consists of 405 individual units ranging from 0.01 to 1.2 m thickness with an average thickness of 0.35 m. The core description is presented in three formats, a typed entry of the logging sheet in MSExcel, a synthesized MSExcel spreadsheet for entry to the database, and the MSAccess database. The core is also documented by 739 photos that have also been combined in 113 photo mosaics. Grain size analysis was completed on 192 samples and TOC analysis on 241 samples. Downhole geophysical logs on this CD include: conductivity, natural gamma, magnetic susceptibility, temperature, and p-wave. Data files are presented in the following, text, MSExcel, MSAccess, Adobe Acrobat, and jpg file formats. The GSC data forms the main content of this CD-ROM. The data has been summarized on the poster "Pontypool 'Golden Spike' Borehole Data Compilation" published as GSC Open File 1746. This Open File is also on this CD as an Adobe Acrobat pdf file. This Core is located within the Pontypool wedge of the Oak Ridges Moraine. It intercepts Oak Ridges Moraine to a depth of ~96 m and is predominantly silt and sand. Below this depth is 74 m of Lower sediment that is predominantly diamicton and silt - clay. Bedrock was intercepted at ~169 m depth. The Oak Ridges Moraine sediment has infilled and buried a tunnel channel.

Hydrogeological models need to be supported by a clear understanding of the subsurface geology to provide effective assessment, flow modelling, or management of groundwater regimes. This paper illustrates how geophysical and sedimentological data can be used to significantly improve watershed-scale hydrostratigraphic models by advancing our understanding of the subsurface through regional hydrogeological investigations in the Greater Toronto Area. The example of a 3 km shallow seismic reflection survey that traverses a buried channel within Bowmanville Creek watershed, Oak Ridges Moraine, Ontario, illustrates a basis for linking geophysical and sedimentological properties to regional hydrostratigraphic parameters. Seismic reflection methods plus seismic stratigraphy and a well-constrained three-dimensional geological framework have helped to (i) identify regional hydrostratigraphic units, (ii) define properties and trends of these units–facies, (iii) improve depositional models that assist hydrogeological analysis, and (iv) establish a hydrostratigraphic framework within a watershed. The extent, proportions, boundaries, and variation in internal properties of major hydrostratigraphic units could be identified to greater than 100 m depth. Geostatistical analysis of seismic amplitudes was used to provide a quantitative measure of heterogeneity in a glaciofluvial aquifer with inadequate parameter support. Benefits to engineering practice include improved siting of monitors and tests from portrayal of the spatial organization, geometry, and variability of hydrostratigraphic units based on sedimentary architecture and environments of deposition. Hydrogeological modelling can be improved with better knowledge of the geometry of aquifers and aquitards and grid-cell boundaries that correspond with the defined sediment boundaries that control properties.Key words: Oak Ridges Moraine, hydrogeology, seismic stratigraphy, southern Ontario, sedimentology.

Geological maps are keys to communicating earth science information and their use is fundamental to land-use planning. A new 1:200 000 scale surficial geology map synthesizes recent 1:50 000 and 1:20 000 mapping in the Oak Ridges Moraine-Greater Toronto Area. These regional geological data provide consistent mapping across the area in aid of terrain analysis, resource evaluation, and environmental assessment. The mapping provides, for the first time, the basis for developing regional geological models within the area. The geological mapping synthesizes approximately 20 000 new and archival ground observations that are grouped into 11 deposits or map units. Map units have been organized into major sediment packages depicted in a three-dimensional regional geological model that highlights six principal stratigraphic elements. These regional strata, from oldest to youngest, are: 1) bedrock, 2) lower deposits, 3) Newmarket Till, 4) Channel fill, 5) Oak Ridges Moraine, and 6) Halton Till.

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.