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Oxygen and carbon isotope ratios of soil carbonate and carbon isotope ratios of soil organic matter (SOM) separated from three cores, Kalpi, IITK and Firozpur, of the Ganga Plain, India are used to reconstruct past rainfall variations and their effect on ambient vegetation. The δ18O values of soil carbonate (δ18OSC) analyzed from the cores range from −8.2 to −4.1‰. Using these variations in δ18OSC values we are able, for the first time, to show periodic change in rainfall amount between 100 and 18 ka with three peaks of higher monsoon at about 100, 40 and 25 ka. The estimation of rainfall variations using δ18O value of rainwater-amount effect suggests maximum decrease in rainfall intensity (~ 20%) during the last glacial maximum. The δ13C values of soil carbonate (δ13CSC) and SOM (δ13CSOM) range from −6.3 to + 1.6‰ and −28.9 to −19.4‰, respectively, implying varying proportions of C3 and C4 vegetations over the Ganga Plain during the last 100 ka. The comparison between monsoonal rainfall and atmospheric CO2 with vegetation for the time period 84 to 18 ka indicate that relative abundances of C3 and C4 vegetations were mainly driven by variations in monsoonal rainfall.

Remediation of nitrate pollution of Earth’s rivers and aquifers is hampered by cumulative biogeochemical processes and nitrogen sources. Isotopes (δ15N, δ18O) help unravel spatiotemporal nitrogen(N)-cycling of aquatic nitrate (NO3−). We synthesized nitrate isotope data (n = ~5200) for global rivers and shallow aquifers for common patterns and processes. Rivers had lower median NO3− (0.3 ± 0.2 mg L−1, n = 2902) compared to aquifers (5.5 ± 5.1 mg L−1, n = 2291) and slightly lower δ15N values (+7.1 ± 3.8‰, n = 2902 vs +7.7 ± 4.5‰, n = 2291), but were indistinguishable in δ18O (+2.3 ± 6.2‰, n = 2790 vs +2.3 ± 5.4‰, n = 2235). The isotope composition of NO3− was correlated with water temperature revealing enhanced N-cascading in warmer climates. Seasonal analyses revealed higher δ15N and δ18O values in wintertime, suggesting waste-related N-source signals are better preserved in the cold seasons. Isotopic assays of nitrate biogeochemical transformations are key to understanding nitrate pollution and to inform beneficial agricultural and land management strategies.

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Mapping, sedimentological studies, and sequence stratigraphic analysis in parts of the Himalayan peripheral foreland basin of northwest India suggest that deposition of basinal turbidites, derived from both the orogenic and ramp sides, took place due to progressive uplift of the basin margin, causing forced regression. The forced regressive wedge of shoreface white sandstone, thus deposited throughout the foreland basin across the regressive surface of marine erosion, cannot be included in the alluvial sediments of Dagshai Formation. Contrary to earlier inferences, the unconformity between the Subathu and Dagshai Formations is found to occur at the top of the white sandstone marked by caliche development or erosion by Dagshai channel sand interpreted as a Type 1 sequence boundary. The reworked fossils in calciturbidite units suggest that the upper limit of the Subathu Formation must be signifi cantly younger than ca. 44 Ma, and the proposition of a synchronous orogenscale unconformity of >10 m.y. duration and early exhumation of Himalayan rocks should be reassessed. The duration of unconformity between Subathu and Dagshai Formations is interpreted to be ≤3 m.y. The sea-level fall and shoaling of Subathu Sea that was already set in by forced regression received tectonic enhancement only at the beginning of the Dagshai Formation, which resulted a total turnaround from a marine to a continental alluvial system.