Final answer:
The geochemical plot comparing Sr and Nd isotopic values is the most effective at constraining the source of the sandstones, providing precise information about rock provenance, vital for hydrogeologists analyzing potential groundwater reservoirs.
Step-by-step explanation:
Of the three geochemical plots used in geosciences to constrain the source of the sandstones, the one involving the analysis of Sr and Nd values proves to be the most effective. Such isotope geochemistry methods are typically able to provide more precise information regarding the provenance of sedimentary rocks. When dealing with samples containing proportions of sand, silt, and clay, triangular plots can be very useful for the classification of the sedimentary rocks, however, this might not be sufficient for source determination without additional information.
By comparing the geochemical signatures of potential source areas with those found in the sediment, one can often delineate which source rocks have contributed to the sediments in question. For instance, finding a close match between the sediment's isotope geochemistry and that of a known rock formation could much more reliably indicate its source. Additionally, sandstones can suggest specific tectonic settings, with their composition and characteristics offering clues to the level of tectonic activity.
Geochemical Analysis for Source Determination
With little known about the geology in the study area, determining the average age of the rocks at potential source locations through geochemical methods like radiometric dating can reveal important clues. When analyzing Sr and Nd isotopic ratios, a plot that compares these values for various source areas will likely offer conclusive evidence of the sandstone's origins. It's important to note the role of tectonic settings as inferred from rock types such as limestones, sandstones, shales, and conglomerates.
Groundwater and Reservoir Analysis
Hydrogeologists employ concepts like pore space in rocks to determine the best aquifers, with laterally continuous sand layers being identified as ideal. When creating a cross-section between cores 2 and 3, the focus is on the thickness of these potential reservoirs. This information will inform the minimum depth to drill to access groundwater in new wells, making it vital to locate economically viable and sustainable sources of water.