Salinity of Quaternary sediments and halophytes at Starunia palaeontological site and vicinity (Carpathian region, Ukraine)

Abstract

Interdisciplinary geophysical, geochemical and botanical studies were performed to recognize the problem of salinity of Quaternary sediments in the place, where woolly rhinoceroses were discovered at the beginning of the 20th century. Geoelectric methods (high resolution geoelectric research with electromagnetic conductivity meter) enabled construction of maps of the distribution of conductivity of near-surface sediments. Variation of conductivity with depth was recognized with penetrometer-based geoelectric measurements. Measured conductivity mainly depends on the level of mineralization (salinity) of underground water filling the pores and voids of poorly consolidated Quaternary sediments and partly underlying Miocene strata. Several samples were taken from geological boreholes. The analysis of these cores enabled estimation of salt (chloride ion) content in the solid phase of sediments. This content varies from place to place and with depth in an unpredictable way. The highest values reached 8.5 wt%. Generally, on the basis of a qualitative comparison, the salinity data gained from sampled cores correlate with distribution of apparent conductivity obtained with geoelectric methods. Nevertheless, in some places there is a discrepancy between geophysical and geochemical data, especially for penetrometer versus borehole data. It may be partly explained by an unavoidable difference in location of the geological borehole and penetrometer site (technically this cannot be the same place). During botanical field studies a group of vascular plants growing on saline soils (halophytes) was found. Halophytes indicate a higher salt concentration in the soil. Their aggregations are extremely rare in the Carpathian region. The pattern of halophytes distribution reflected the presence of saline water sources, and their flows and soils affected by them. Generally, the distribution of halophytes showed a good correlation with the distribution of high-conductivity anomalies determined with the surface geoelectric survey.