Reconstruction of Thermal Conditions in the Subboreal Inferred from Isotopic Studies of Groundwater and Calcareous Tufa from the Spring Mire Cupola in Wardzyń (Central Poland)

Abstract

Studies with application of stable isotopes of oxygen and carbon have been performed on calcareous tufa, groundwater and dissolved inorganic carbon (DIC) from the spring mire cupola in Wardzyń. This study was focused on the verification of the a priori hypothesis that the analysed calcareous tufa is a chemical deposit and on the attempt to supplement an earlier scenario of environmental changes in the Subboreal with oscillations of water temperature. The constructed model of chemical and isotope balance, and δ13C determinations in DIC, allowed for calculating ratios of stable isotopes of carbon in particular speciations and in gaseous CO2. The obtained results coupled with δ13C values in calcite indicate that this mineral precipitated from the solution chemically (without the contribution of living organisms). Additionally, it was possible to reconstruct the temperature range at which the calcareous tufa was formed. The reconstructed scenario of changes in the thermal conditions was refined based on δ18O determinations in groundwater and calcite. Accordingly, the oldest calcareous tufa, with an age of about 5500 cal years BP, was formed in cool climate conditions (with average annual temperatures by about 3 °C lower than presently). The formation of younger series of the calcareous tufa took place between 4400–2900 cal years BP and represents a much warmer period with two distinct cooler episodes at 3900 and 3000 cal years BP, respectively. The course of the obtained temperature curves correlates well with the GISP2 curve and curves obtained for other sites in Northern, and Central Europe.

Facies and Origin of Tufa Deposits from the Gostilje River Basin and the Sopotnica River Basin (SW Serbia)

“…Nevertheless, tufa deposits have been studied worldwide as their isotopic composition can point to environmental conditions. A number of studies dealt with tufa deposits from an environmental point of view in the Mediterranean region [17,22,26,39,42,[47][48][49][50][51][52], Central Europe [21,38,53], and Great Britain [54][55][56]. Stable isotope data of the studied sites were compared with some well-known tufa deposits in Europe at Figure 6.…”

Method for Identifying and Estimating Karst Groundwater Runoff Components Based on the Frequency Distributions of Conductivity and Discharge

“…Due to the technological problem, some data in 2015 were missed, and hydrological years (2016-2018) with complete time series were analyzed. After the correction of the measurement results in Xiangxi river basin, the rating curve of Heilongquan Spring was established through measurements of the discharge at different water levels, and the monitored water level was converted to discharge, expressed in Equations (5) and (6).…”

“…However, the heterogeneity of karst aquifers poses a barrier to this knowledge [2]. Traditional methods such as field surveys, fracture measurement, cave detection, hydrogeological drilling, and geophysical methods [3,4] are often costly, whereas separating karst groundwater runoff components through tracer tests, isotope analysis and hydrograph recession analysis [5][6][7][8] have some spatial and temporal scale limitations. High-frequency online monitoring of conductivity and discharge has been widely used in karst hydrogeological surveys [7][8][9][10][11].…”