Hydrogeochemical characteristics of groundwater and pore-water and the paleoenvironmental evolution in the past 3.10 Ma in the Xiong’an New Area,North China

The groundwater level has been continuously decreasing due to climate change and long-time overexploitation in the Xiong’an New Area,North China,which caused the enhanced mixing of groundwater in different aquifers and significant changes in regional groundwater chemistry characteristics.In this study,groundwater and sediment pore-water in drilling cores obtained from a 600 m borehole were investigated to evaluate hydrogeochemical processes in shallow and deep aquifers and paleo-environmental evolution in the past ca.3.10 Ma.Results showed that there was no obvious change overall in chemical composition along the direction of groundwater runoff,but different hydrochemical processes occurred in shallow and deep groundwater in the vertical direction.Shallow groundwater(<150 m)in the Xiong’an New Area was characterized by high salinity(TDS>1000 mg/L)and high concentrations of Mn and Fe,while deep groundwater had better water quality with lower salinity.The high TDS values mostly occurred in aquifers with depth<70 m and>500 m below land surface.Water isotopes showed that aquifer pore-water mostly originated from meteoric water under the influence of evaporation,and aquitard pore-water belonged to Paleo meteoric water.In addition,the evolution of the paleoclimate since 3.10 Ma BP was reconstructed,and four climate periods were determined by theδ18O profiles of pore-water and sporopollen records from sediments at different depths.It can be inferred that the Quaternary Pleistocene(0.78‒2.58 Ma BP)was dominated by the cold and dry climate of the glacial period,with three interglacial intervals of warm and humid climate.What’s more,this study demonstrates the possibilities of the applications of pore-water on the hydrogeochemical study and further supports the finding that pore-water could retain the feature of paleo-sedimentary water.

Multi-Elemental Chemostratigraphy,Sequence Development,Depositional History,and Environmental Importance of Early Eocene Red Beds(Kuldana Formation)in NW Himalayas,Pakistan

The Eocene Kuldana Formation(KF)in the Yadgar area of Pakistan,comprises a diverse range of sedimentary facies,including variegated red beds of shales,mudstones,and sandstones,as well as interbedded limestone and marl.In this study,we conducted an integrated micropaleontological,sedimentological,mineralogical,and geochemical investigation to determine the depositional setting,biochronology,provenance,and paleoclimate of the KF.The study identified six lithofacies and six microfacies,which indicate a variety of environments ranging from floodplains and channels to the margins and shallow marine settings.The nannofossil biostratigraphy places the KF in the Early Eocene,more precisely the NP10 zone(Ypresian),and the fossil zone of benthic foraminifera classifies the study section as the Shallow Benthic Zone SBZ-8(Middle Ilerdian 2).In terms of petrography,the KF sandstone was classified as litharenite and feldspathic litharenite,while the QtFL diagram suggests a recycled orogen.Geochemical proxies indicate an oxidizing environment,a high-to-low regular sedimentation rate,moderate-to-intense chemical weathering in the source region,and a warm-humid to dry climate during the deposition of KF.Overall,the findings suggest that the deposition of KF marks the end of Neo-Tethys due to the Early Eocene Indian–Kohistan collision and that the uplifting of the Himalayas provided the source for the deposition of KF in the foreland basin.The study provides new insights into the depositional environment,biochronology,provenance,and paleoclimate of KF,and highlights the potential for red beds as reliable indicators of oxygenation levels in proximity to mineral deposits.