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A continuous stable isotope record of last interglacial age from the Bulgarian Cave Orlova Chuka

Pawlak Jacek, Błaszczyk Marcin, Hercman Helena, Matoušková Šárka

Geochronometria

2019

Vol. 46, no. 1

87--101

Recent research shows that the last interglacial climate was more unstable in comparison to Holocene. Lack of suitable dating techniques and precisely defined absolute age benchmarks is one from main problems for present LIG studies. Therefore many of LIG chronologies base on indirect dating techniques like record alignment strategies. In this context, speleothems are valuable paleoclimate archives because of their capability to be dated by U-series method. In Europe LIG speleothem records are known mostly from western and central part of the continent. In this paper we present a 1,650 mm long stalagmite (ocz-6) from Bulgarian Cave Orlova Chuka. The ocz-6 stalagmite records the period of time ca. 129–112 ka. Ocz-6 stalagmite was analyzed in terms of stable isotopic composition of calcite and trace elements content. All analyzed geochemical proxies point to dynamic changes in the environment during the Last Interglacial time. At the time of interglacial development (129–126.5 ka), ocz-6 records shows systematic change in proportion of moisture delivered from Atlantic source and other sources. The beginning of last interglacial optimum is connected with a rapid change to more humid and warm conditions. During interglacial demise local climate become more dependent from regional settings.

Colourful speleothems in the Wieliczka Salt Mine

Sawłowicz Z., Przybyło J., Boroń K.

Geological Quarterly

2014

Vol. 58, No. 3

449--458

Secondary halite deposits in the Wieliczka Salt Mine are represented by various forms of speleothems. Some of them, e.g. stalactites, cauliflowers or crusts, reveal various hues, yellow to red to brown. These hues are related to iron compounds, but the forms, occurrence and composition of these compounds has not previously been studied. To explain the origin of their colours a detailed study of samples collected in the mine, including brines and water soluble extracts and produced experimentally in the laboratory, has been undertaken using SEM, XRD and AAS. The colourful speleothems are compared, using SEM-EDS, with the forms and composition of rusting metal artefacts, where several iron oxide minerals have been identified. We suggest that coloured halite is generally pure halite of which the surface was covered by a ferric minerals suspension in the brine. Colours of the speleothems stem from the various colours of iron minerals whereas their intensity is related probably to the type of fluid that coated the crystals, a continuous film or finely dispersed micron-size mineral aggregates.