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

Mościcki W. J., Toboła T., Zarzyka-Ryszka M.

Annales Societatis Geologorum Poloniae

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2009

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Vol. 79, No 3

391-402

EN

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.

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Electric resistivity and compactness of sediments in the vicinity of boreholes drilled in the years 2007-2008 in the area of Starunia palaeontological site (Carpathian region, Ukraine)

Mościcki W. J., Sokołowski T.

Annales Societatis Geologorum Poloniae

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2009

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Vol. 79, No 3

343-355

EN

Geoelectric research aiming to assess heterogeneity of geological environment was carried out in the Starunia area, where the unique specimens of woolly rhinoceros were discovered at the beginning of the 20th century. The DC azimuthal pole-dipole resistivity soundings and penetrometer-based resistivity profiling with simultaneous penetration-velocity measurements were used to study variability of environment in the vicinity of geological boreholes. No evident correlation was found between lithology of drilled sediments and geophysical data. Nevertheless, remarkable horizontal and vertical variability of geophysical parameters were observed. The largest horizontal changes may reflect an existence of some sharp boundaries in study area. The measured physical properties of geological strata: electric resistivity and compactness (estimated from penetration velocity) change also with the depth but correlation with geological structure can be found in limited cases only. Registered variability may have originated from several reasons: complex geological arrangement of shallow layers, salty underground water and bitumen presence in voids and pores, influence of neotectonic activity, and/or from transformations of near surface environment caused by past mining activity.

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Characterization of near-surface sediments based on combined geoelectric studies at Starunia palaeontological site and vicinity (Carpathian region, Ukraine)

Mościcki W. J.

Annales Societatis Geologorum Poloniae

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2009

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Vol. 79, No 3

333-342

EN

Combined geoelectric research was performed in the Starunia area, where the specimens of woolly rhinoceros were discovered at the beginning of the 20th century. The work included: DC resistivity soundings, electromagnetic terrain conductivity measurements, resistivity imaging and penetrometer-based resistivity profiling. The main purpose of the survey was to give geoelectric characterization of near-to-surface sediments and estimate their variability (extent, thickness and electric resistivity). Generally, resistivity of geological strata is low and decreases with depth but its spatial distribution is locally complex. This complexity reflects joint effects caused by the presence of salty underground water outflows from the salt-bearing Miocene Vorotyshcha beds into the Quaternary sediments, distinct transformations of the geological medium by former ozokerite and oil exploitation and current activity of the natural geological processes in the area.