A geospatial investigation of interlinkage between basement fault
architecture and coastal aquifer hydrogeochemistry
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Abstract
The Mahanadi delta, deposited on a series of horst and graben basement structures, is considered an extension of
the East Lambert Rift of Antarctica. Current study is based on the hydrogeochemical assessment of this deltaic
aquifer system and geospatial analysis thereof, to appreciate the basement structure influence on groundwater
chemistry. Major ion chemistry of subsurface waters portrays a distinct saline contamination across the terrain
and varied regimes of water types, specifically with respect to southern and northern parts of this aquifer system.
Findings of the study indicate a general near surface saline horizon and significant fragmentation of the hydrostatic
units. This, in turn, implies noteworthy influence of formational water to salinity regimes and basin
structural changes for the escape of these waters to surroundings. A plot of recent low intensity earthquakes
displays proximity of epicenters to the faults as well as striking similarity to the trend of terrestrial faults indicating
multiple reactivations of the faults. To further corroborate the above findings, spatial pattern analysis of
individual hydrochemical variables is carried out which reveals specific clusters of sources (groundwater mixing)
and sinks (groundwater dispersion) in proximity to basement fault dispositions. While the faults can be disregarded
as conduits or barriers owing to their great depth, the overlying sedimentary mass, particularly, the
horizons with significant clayey content have been distorted due to post rift subsidence and fault reactivations. A
proximity analysis of ionic clusters points towards a greater influence of longitudinal faults to that of the
transverse ones on groundwater mixing or dispersion.
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