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

1986 ◽  
Vol 23 (7) ◽  
pp. 938-947 ◽  
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.

scholarly journals Origin and Residence Time of Groundwater in the Shallow Coastal Aquifer of Eastern Dahomey Basin, Southwestern Nigeria, Using δ18O and δD Isotopes

2020 ◽  
Vol 10 (22) ◽  
pp. 7980
Author(s):  
Jamiu A. Aladejana ◽  
Robert M. Kalin ◽  
Ibrahim Hassan ◽  
Philippe Sentenac ◽  
Moshood N. Tijani
Keyword(s):  
Residence Time ◽  
Vadose Zone ◽  
Major Ions ◽  
Dry Season ◽  
Global Network ◽  
Shallow Aquifer ◽  
Seasonal Effect ◽  
Water Types ◽  
Groundwater Samples ◽  
Dahomey Basin

This study employed stable isotopes of δ18O and δ2H in conjunction with other hydrological parameters to understand the origin, inferred residence time, and seasonal effect of groundwater in the shallow aquifers of the eastern Dahomey Basin. A total of 230 groundwater samples (97 in the wet season and 133 in the dry season) were collected from the borehole and shallow aquifer between May 2017 and April 2018. Groundwater analysis included major ions and δ18O and δ2H, isotopes data in precipitation from three selected Global Network of Isotope in Precipitation (GNIP) stations across West Africa, Douala in Cameroon, Cotonou in Republic of Benin, and Kano in Nigeria were used in comparative analysis. Results of the hydrochemical model revealed Ca-HCO3 and Na-Cl as dominant water types with other mixing water types such as Ca–SO4, Ca–Cl, Na–SO4, and K–Mg–HCO3, which characterised early stage of groundwater transformation as it infiltrates through vadose zone into the aquifer. δ18O and δ2H precipitation data from the three stations plotted along with the groundwater samples indicate recent meteoric water origin, with little effect of evaporation during the dry season. The plot of Total Dissolved Solids (TDS) against δ18O showed clustering of the water samples between the recharge and the evaporation zone with dry season samples trending towards increased TDS, which is an indication of the subtle effect of evaporation during this period. Tracing groundwater types along the flow paths within the basin is problematic and attributed to the heterogeneity of the aquifer with anthropogenic influences. Moreover, a comparison of the δ18O and δ2H isotopic compositions of groundwater and precipitation in the three selected stations, with their respective deuterium excess (D-excess) values established low evapotranspiration induced isotope enrichment, which could be due to higher precipitation and humidity in the region resulting in low isotope fractionation; hence, little effect of seasonal variations. The study, therefore, suggested groundwater recharge in the shallow aquifer in the eastern Dahomey Basin is of meteoric origin with a short residence time of water flows from soils through the vadose zone to the aquifers.

Closing a scale-gap in Earth observation using regional-scale airborne geophysics in the lower Mississippi Valley

2021 ◽  
Author(s):  
Burke Minsley ◽  
James Rigby ◽  
Stephanie James ◽  
Bethany Burton ◽  
Katherine Knierim ◽  
...  
Keyword(s):  
United States ◽  
Groundwater Resources ◽  
Regional Scale ◽  
The United States ◽  
Shallow Aquifer ◽  
New Madrid Seismic Zone ◽  
Seismic Zone ◽  
Aquifer Systems ◽  
Regional Hydrogeology ◽  
New Madrid

&lt;p&gt;Critical groundwater resources and hidden seismic hazards underly much of the Mississippi Alluvial Plain. Spanning nearly 100,000 square kilometers across seven states, this region hosts one of the most prolific shallow aquifer systems in the United States that supports a $12 billion agricultural economy amidst chronic groundwater decline. Further, underlying fault structures of the Reelfoot Rift and New Madrid Seismic Zone represent an important and poorly understood hazard with a complex pattern of historical impacts. Despite its societal and economic importance, mapping of shallow subsurface architecture with spatial resolution needed for effective management is insufficient. Here, we report the results of 40,000 flight-line-kilometers of electromagnetic, magnetic, and radiometric data collectively providing a system-scale snapshot of an entire aquifer system, the first such effort in the United States. This survey enables new understanding of the regional hydrogeology while also revealing previously unseen large vertical displacements (exceeding 50 m) in the uppermost Tertiary units within the New Madrid Seismic Zone.&lt;/p&gt;

scholarly journals Airborne geophysical surveys of the lower Mississippi Valley demonstrate system-scale mapping of subsurface architecture

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Burke J. Minsley ◽  
J. R. Rigby ◽  
Stephanie R. James ◽  
Bethany L. Burton ◽  
Katherine J. Knierim ◽  
...  
Keyword(s):  
Groundwater Age ◽  
Regional Scale ◽  
The United States ◽  
Shallow Aquifer ◽  
Mississippi Valley ◽  
Seismic Zone ◽  
Lower Mississippi Valley ◽  
Shallow Subsurface ◽  
Aquifer Systems ◽  
Geophysical Surveys

AbstractThe Mississippi Alluvial Plain hosts one of the most prolific shallow aquifer systems in the United States but is experiencing chronic groundwater decline. The Reelfoot rift and New Madrid seismic zone underlie the region and represent an important and poorly understood seismic hazard. Despite its societal and economic importance, the shallow subsurface architecture has not been mapped with the spatial resolution needed for effective management. Here, we present airborne electromagnetic, magnetic, and radiometric observations, measured over more than 43,000 flight-line-kilometers, which collectively provide a system-scale snapshot of the entire region. We develop detailed maps of aquifer connectivity and shallow geologic structure, infer relationships between structure and groundwater age, and identify previously unseen paleochannels and shallow fault structures. This dataset demonstrates how regional-scale airborne geophysics can close a scale gap in Earth observation by providing observational data at suitable scales and resolutions to improve our understanding of subsurface structures.

HYDRODYNAMIC ANALYSIS OF FLOW SYSTEMS AND FAULT SEAL INTEGRITY IN THE NORTH WEST SHELF OF AUSTRALIA

2001 ◽  
Vol 41 (1) ◽  
pp. 347 ◽  
Author(s):  
C.J. Otto ◽  
J.R. Underschultz ◽  
A.L. Hennig ◽  
V.J. Roy
Keyword(s):  
Fluid Flow ◽  
Regional Scale ◽  
Local Flow ◽  
Hydrodynamic Analysis ◽  
North West ◽  
Seal Integrity ◽  
The North ◽  
Regional Flow ◽  
Aquifer Systems ◽  
Migration Pathways

The North West Shelf hydrodynamics pressure database, developed as part of the North West Shelf Hydrodynamics Project, currently contains 7,780 pressure data points and hundreds of stress, temperature and water salinity data. All data have been ranked using a newly developed quality-control system. Equivalent hydraulic head mapping (fluid potential energy analysis) to interpret fluid migration pathways, hydraulic barriers and conduits was shown to be a valid technique despite lateral and vertical fluid density variations. Pressureelevation analysis identified six major aquifer systems (hydrostratigraphic units) in the regional North West Shelf. On a regional scale, the general flow direction in the North West Shelf is from the basins’ depocentres towards the onshore and upwards to the shallower aquifer systems. Compaction-driven flow is the main driving force for fluid flow in the North West Shelf. Overpressured compartments in the Carnarvon Basin are leaking, not hydraulically isolated from the regional flow field, thus generating their own local flow system. In general, fluid flow within the hydrostratigraphic units is parallel to the trend of major fault systems, which act as barriers in the horizontal plane of the aquifer. However, local-scale hydrodynamic analysis has shown that faults can act as fluid conduits between hydrostratigraphic units providing vertical hydraulic communication (e.g. Mardie to Barrow aquifers). Case studies in the Harriet, Gorgon, Griffin, Goodwyn and Vulcan areas have shown that the migration paths can be very complex due to the hydraulic nature of the faults and the presence of overpressured compartments

Hydraulics of horizontal wells in fractured shallow aquifer systems

2003 ◽  
Vol 281 (1-2) ◽  
pp. 147-158 ◽  
Author(s):  
Eungyu Park ◽  
Hongbin Zhan
Keyword(s):  
Horizontal Wells ◽  
Shallow Aquifer ◽  
Aquifer Systems

Coral microatolls and a probable Middle Ordovician example

1990 ◽  
Vol 64 (1) ◽  
pp. 39-43 ◽  
Author(s):  
David R. Kobluk ◽  
Iqbal Noor
Keyword(s):  
Coral Reefs ◽  
Fossil Record ◽  
Scleractinian Coral ◽  
Regional Scale ◽  
Southern Ontario ◽  
Middle Ordovician ◽  
Reef Environments ◽  
Maximum Water ◽  
Water Depths ◽  
Tabulate Corals

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.

scholarly journals Eburnean deformation pattern of Burkina Faso and the tectonic significance of shear zones in the West African craton

2020 ◽  
Vol 191 ◽  
pp. 2 ◽  
Author(s):  
Dominique Chardon ◽  
Ousmane Bamba ◽  
Kalidou Traoré
Keyword(s):  
Burkina Faso ◽  
Shear Zone ◽  
Regional Scale ◽  
Kinematic Model ◽  
Shear Zones ◽  
West African ◽  
Deformation Pattern ◽  
The West ◽  
West African Craton ◽  
Regional Flow

Shear zones of the Paleoproterozoic Eburnean accretionary Orogen (West African craton) are investigated by means of large-scale structural mapping. Regional scale (10-100 km) mapping was based on the aeromagnetic survey of Burkina Faso and craton-scale (1000 km) mapping on a compilation of fabric data. At both scales, shear zones are arranged as an anastomosed transpressional network that accommodated distributed shortening and lateral flow of the orogenic lithosphere between the converging Kénéma-Man and Congo Archean provinces. Structural interference patterns at both scales were due to three-dimensional partitioning of progressive transpressional deformation and interactions among shear zones that absorbed heterogeneities in the regional flow patterns while maintaining the connectivity of the shear zone network. Such orogen-scale kinematic patterns call for caution in using the deformation phase approach without considering the “bigger structural picture” and interpreting displacement history of individual shear zones in terms of plate kinematics. The West African shear zone pattern is linked to that of the Guiana shield through a new transatlantic correlation to produce an integrated kinematic model of the Eburnean-Transamazonian orogen.

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