Regional-scale groundwater geoscience in southern Ontario: an Ontario Geological Survey and Geological Survey of Canada groundwater geoscience open house

A disk-shaped massive colony of Tetradium, from the Middle Ordovician Bobcaygeon Formation in southern Ontario, displays features of a coral microatoll. This is the first pre-Holocene coral microatoll yet described, indicating that some tabulate corals in level-bottom communities were growing as microatolls as do many modern colonial skeleton-secreting organisms.The microatoll therefore is not strictly a Quaternary or even Cenozoic phenomenon, but has a fossil record that may span most of the Phanerozoic. This indicates that the special conditions necessary for microatoll growth have existed outside of reef environments, and were present before the advent of scleractinian coral reefs. It may be possible to use ancient microatolls to estimate absolute water depths at low tide, thereby providing a means for estimating maximum water depths on a local and regional scale.

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Chapman, L. J. et Putman, D. F. (1984) : The Physiography of Southern Ontario. 3 édition, Toronto, Ontario Geological Survey, Special Volume 2, 270 p., 12 tabl., 30 fig., 86 photos, 1 carte couleur à 1/600 000, 21 x 30 cm

Géographie physique et Quaternaire ◽

10.7202/032592ar ◽

1985 ◽

Vol 39 (1) ◽

pp. 108

Author(s):

Jean-Marie Dubois

Keyword(s):

Geological Survey ◽

Special Volume ◽

Southern Ontario

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Dolomitization of Paleozoic Successions, Huron Domain of Southern Ontario, Canada: Fluid Flow and Dolomite Evolution

Water ◽

10.3390/w13172449 ◽

2021 ◽

Vol 13 (17) ◽

pp. 2449

Author(s):

Ihsan S. Al-Aasm ◽

Richard Crowe ◽

Marco Tortola

Keyword(s):

Regional Scale ◽

Carbon Isotopic Composition ◽

Warm Water ◽

Geochemical Data ◽

Fluid Composition ◽

Rock Interaction ◽

Near Surface ◽

Southern Ontario ◽

Ce Anomaly ◽

Diagenetic Fluids

Integrated petrographic, isotopic, fluid inclusion microthermometry, and geochemical analyses of Paleozoic carbonate successions from multiple boreholes within the Huron Domain, southern Ontario were conducted to characterize the diagenetic history and fluid composition, on a regional scale, and evaluate the nature and origin of dolomitized beds. Multiple generations of non-stochiometric dolomite have been observed. These dolomites occur as both replacement (D1 and D2) and cement (saddle dolomite; SD) and formed either at near-surface to shallow burial zone (D1) or intermediate burial (D2 and SD). Petrographic and geochemical data of dolomite types and calcite cement suggest that these carbonates have experienced multiple fluid events that affected dolomite formation and other diagenetic processes. Cambrian and Ordovician strata have two possibly isolated diagenetic fluid systems; an earlier fluid system that is characterized by a pronounced negative shift in oxygen and carbon isotopic composition, more radiogenic Sr ratios, warm and saline signatures, higher average ∑REE compared to warm water marine brachiopods, negative La anomaly, and positive Ce anomaly; and a later Ordovician system, characterized by less negative shifts in oxygen and carbon isotopes, comparable Th, hypersaline, a less radiogenic, less negative La anomaly, and primarily positive Ce anomaly but also higher average ∑REE compared to warm water marine brachiopods. Ordovician, Silurian, and Devonian Sr isotopic ratios, however, show seawater composition of their respective age as the primary source of diagenetic fluids with minor rock/water interactions. In contrast, the isotopic data of the overlying Silurian and Devonian carbonates show overlaps between δ13C and δ18O values. However, δ18O values show evidence of dolomite recrystallization. D2 shows wide Th values and medium to high salinity values. Higher Th and salinity are observed in SD in the Silurian carbonates, which suggest the involvement of localized fluxes of hydrothermal fluids during its formation during Paleozoic orogenesis. Geochemical proxies suggest that in both age groups the diagenetic fluids were originally of coeval seawater composition, subsequently modified via water-rock interaction possibly related to brines, which were modified by the dissolution of Silurian evaporites from the Salina series. The integration of the obtained data in the present study demonstrates the linkage between fluid flux history, fluid compartmentalization, and related diagenesis during the regional tectonic evolution of the Michigan Basin.

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Hydrochemical interpretation of groundwater flow systems in Quaternary sediments of southern Ontario

Canadian Journal of Earth Sciences ◽

10.1139/e86-095 ◽

1986 ◽

Vol 23 (7) ◽

pp. 938-947 ◽

Cited By ~ 25

Author(s):

K. W. F. Howard ◽

P. Beck

Keyword(s):

Major Ions ◽

Regional Scale ◽

Shallow Aquifer ◽

Sediment Geochemistry ◽

Quaternary Sediments ◽

Southern Ontario ◽

Water Types ◽

Regional Flow ◽

Aquifer Systems ◽

Composite Flow

Shallow aquifer systems in surficial Quaternary sediments are geometrically complex, with highly variable hydraulic characteristics. Consequently these systems are extremely difficult to assess hydrogeologically using conventional investigation techniques and are often poorly understood. In a 500 km2 area of southern Ontario, hydrochemical techniques were used to investigate the hydraulic integrity and regional flow behaviour of 14 aquifer systems defined within 100 m of Quaternary overburden. This type of approach had been used successfully in more extensive bedrock aquifer systems but had not previously been applied on a regional scale to shallow Quaternary systems where sediment geochemistry and flow conditions are highly variable and rarely known. The study involved analysis of over 260 well waters for pH, major ions (Ca, Mg, Na, K, HCO3, Cl, and SO4) and subsidiary ions (NO3, I, Br, and F). Selected samples were analyzed for tritium.The groundwaters are classified into eight water types, two of which are sodium chloride in character and of bedrock origin. Of the remaining six, four are related by a chemical evolutionary sequence showing transition from a tritiated (> 30 TU), low-iodide (< 5 μg/L) CaHCO3 recharge water to an ion-exchanged, NaHCO3 water low in tritium (< 15 TU) and enriched in iodide (> 15 μg/L). The existence of this sequence implies a regional, composite flow system involving seven supposedly discrete aquifer systems.The two remaining water types are recent tritiated waters (> 20 TU) contaminated by road salt (Cl > 40 mg/L) and agricultural nitrate (NO3 > 10 mg/L). Together with the CaHCO3 waters these clearly delineate major areas of recharge and show that the covering of Halton Till is extensively permeable.

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Overview of surficial geochemistry and indicator mineral surveys and case studies from the Geological Survey of Canada's GEM Program

Geochemistry Exploration Environment Analysis ◽

10.1144/geochem2021-070 ◽

2021 ◽

pp. geochem2021-070

Author(s):

M.B. McClenaghan ◽

W.A. Spirito ◽

S.J.A. Day ◽

M.W. McCurdy ◽

R.J. McNeil ◽

...

Keyword(s):

Northwest Territories ◽

Case Studies ◽

Stream Water ◽

Regional Scale ◽

Stream Sediment ◽

Geological Survey ◽

Ice Flow ◽

Northern Canada ◽

Indicator Mineral ◽

Indicator Minerals

The Geological Survey of Canada carried out reconnaissance-scale to deposit-scale geochemical and indicator-mineral surveys and case studies across northern Canada between 2008 and 2020 as part of its Geo-mapping for Energy and Minerals (GEM) program. In these studies, surficial geochemistry was used to determine the concentrations of up to 65 elements in various sample media including lake sediment, lake water, stream sediment, stream water, or till samples across approximately 1 000 000 km2 of northern Canada. As part of these surficial geochemistry surveys, indicator mineral methods were also used in regional-scale and deposit-scale stream sediment and till surveys. Through this program, areas with anomalous concentrations of elements and/or indicator minerals that are indicative of bedrock mineralization were identified, new mineral exploration models and protocols were developed, a new generation of geoscientists was trained, and geoscience knowledge was transferred to northern communities. Regional- and deposit-scale studies demonstrated how transport data (till geochemistry, indicator mineral abundance) and ice-flow indicator data can be used together to identify and understand complex ice flow and glacial transport. Detailed studies at the Izok Lake Zn-Cu-Pb-Ag VMS, Nunavut, the Pine Point carbonate-hosted Pb-Zn in the Northwest Territories, the Strange Lake REE deposit in Quebec and Labrador as well as U-Cu-Fe-F and Cu-Ag-Au-Au IOCG deposits in the Great Bear magmatic zone, Northwest Territories demonstrate new suites of indicator minerals that can now be used in future reconnaissance- and regional-scale stream sediment and till surveys across Canada.

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Hypogeal geological survey in the “Grotta del Re Tiberio” natural cave (Apennines, Italy): a valid tool for reconstructing the structural setting

Open Geosciences ◽

10.2478/s13533-011-0012-8 ◽

2011 ◽

Vol 3 (2) ◽

Author(s):

Alice Ghiselli ◽

Marzio Merazzi ◽

Andrea Strini ◽

Roberto Margutti ◽

Michele Mercuriali

Keyword(s):

Regional Scale ◽

Geological Survey ◽

Open Pit ◽

Karst Area ◽

Fracture System ◽

Three Dimensional Model ◽

Structural Setting ◽

Fault Systems ◽

Surface Data ◽

Karst Areas

AbstractAs karst systems are natural windows to the underground, speleology, combined with geological surveys, can be useful tools for helping understand the geological evolution of karst areas.In order to enhance the reconstruction of the structural setting in a gypsum karst area (Vena del Gesso, Romagna Apennines), a detailed analysis has been carried out on hypogeal data. Structural features (faults, fractures, tectonic foliations, bedding) have been mapped in the ”Grotta del Re Tiberio” cave, in the nearby gypsum quarry tunnels and open pit benches. Five fracture systems and six fault systems have been identified. The fault systems have been further analyzed through stereographic projections and geometric-kinematic evaluations in order to reconstruct the relative chronology of these structures. This analysis led to the detection of two deformation phases.The results permitted linking of the hypogeal data with the surface data both at a local and regional scale. At the local scale, fracture data collected in the underground have been compared with previous authors’ surface data coming from the quarry area. The two data sets show a very good correspondence, as every underground fracture system matches with one of the surface fracture system. Moreover, in the cave, a larger number of fractures belonging to each system could be mapped. At the regional scale, the two deformation phases detected can be integrated in the structural setting of the study area, thereby enhancing the tectonic interpretation of the area (e.g., structures belonging to a new deformation phase, not reported before, have been identified underground). The structural detailed hypogeal survey has, thus, provided very useful data, both by integrating the existing information and revealing new data not detected at the surface. In particular, some small structures (e.g., displacement markers and short fractures) are better preserved in the hypogeal environment than on the surface where the outcropping gypsum is more exposed to dissolution and recrystallization.The hypogeal geological survey, therefore, can be considered a powerful tool for integrating the surface and log data in order to enhance the reconstruction of the deformational history and to get a three-dimensional model of the bedrock in karst areas.

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