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Estimation of the durations of breaks in deposition – Speleothem case study

Pawlak J., Hercman H., Sierpień P., Pruner P., Gąsiorowski M., Mihevc A., Zupan Hajna N., Bosák P., Błaszczyk M., Wach B.

Geochronometria

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2020

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Vol. 47, no.1

154--170

EN

Speleothems provide one of the most continuous terrestrial archives. However, due to changing conditions in temperature/humidity or the chemistry of percolating water, sedimentation breaks (hiatuses) and erosional events are possible and are commonly recorded in speleothems. Sedimentation breaks with durations longer than the resolution of the studied record should be considered in potential speleothem age-depth models. The most classic and reliable solution to the problem is the independent construction of age-depth models for the parts of speleothems separated by the hiatuses. However, in some cases, it is not possible to obtain a sufficient number of dating results for reliable age-depth model estimation. In such cases, the problem can be solved by the application of other sources of chronological information. Here, based on a few speleothem examples, an alternative approach – oxygen isotopic stratigraphy – is used to estimate the chronology for the parts of speleothems where there is not enough chronological information for classic age-depth models. As a result, the deposition break duration can be estimated.

2

Record of the Pleistocene at karst sites of the Świętokrzyskie (Holy Cross) Mountains region – a review

Urban Jan, Hercman Helena, Ochman Katarzyna, Kasza Andrzej

Studia Quaternaria

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2019

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Vol. 36, Nr 2

87--108

EN

The objective of this paper is a review of data on reconstruction of the Pleistocene palaeogeography (environment) and stratigraphy based on studies of karst sites in the Świętokrzyskie (Holy Cross) Mountains. Although the number of known Pleistocene karst sites in this region is small, the investigations of them have played a crucial role in a research of the Pleistocene. The study of the Kozi Grzbiet site provided the first evidences for new climatostratigraphy and classification of glaciations in Poland. The explanation of genesis of cryogenic calcite crystals discovered in Chelosiowa Jama-Jaskinia Jaworznicka cave system started a new direction of palaeoenvironmental reconstructions of the last glacial period. Kadzielnia palaeontological site was one of the first Early Pleistocene fossil assemblages in karst studied in Poland, whereas Raj cave provided abundant palaeontological and archaeological material from the Last Glacial. Other sites are of less scientific importance, however some of them can be used in education and popularisation of geosciences. Small number of already studied sites does not exclude discoveries of next sites of high scientific importance.

3

Cryogenic carbonates and cryogenic speleothem damage in the Za Hájovnou Cave (Javoříčko Karst, Czech Republic)

Žak K., Lipták V., Filippi M., Orvošová M., Hercman H., Matouškova Š.

Geological Quarterly

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2018

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Vol. 62, No. 4

829--839

EN

A new locality of coarse-grained cryogenic cave carbonates has been found in the Za Hájovnou Cave in Javoříčko Karst in Central Moravia, Czech Republic. Crystals and crystal aggregates, usually up to 15 mm in size, form typical loose accumulations on the surface of large fallen limestone blocks and clays covering the bottoms of several cave chambers distant from the cave entrance. The cryogenic origin of the carbonates is supported by their mode of occurrence, specific crystal and aggregate morphology, and C and O stable isotope data. U-series dating of one sample of cryogenic carbonate (age 29.5 ±0.1 ka) indicated that a period of karst water freezing occurred in marine isotope stage (MIS) 3, within the Weichselian. The cave also hosts numerous examples of speleothem damage. As shown in this paper, some of these are clearly connected with freezing conditions and cave ice action.

4

New isotopic data on karst development in the northern Kraków-Wieluń Upland (southern Poland)

Hercman H., Gąiorowski M., Sujka G.

Annales Societatis Geologorum Poloniae

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2016

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Vol. 86, No. 4

429--436

EN

The Kraków-Wieluñ Upland is one of the major palaeokarst regions in Poland. However, the stages of karst development in this area are neither well documented nor reconstructed. A series of samples from a new location in the vicinity of Raciszyn was analysed. On the basis of the results of U-series dating, four phases of speleothem deposition were distinguished: (1) older than 600 ka, (2) from more than 600 ka to 290 ka, (3) around 150 ka, and the youngest (4), younger than 3 ka. On the basis of all geochronological data from the region, eight stages of karst development were described. The structure of the oldest speleothems indicates even more stages of deposition and erosion that cannot be recognized using the 230Th/234U dating method. These results indicate that the initial creation of empty spaces in the limestone took place in pre-Pleistocene time. After 600 ka ago, climatic conditions were stable for more than 300 ka, allowing the continuous deposition of speleothems. Several episodes of erosion, deposition of clastic sediments and speleothem growth during the Middle and Early Pleistocene were described. This variability of the sedimentation regime clearly reflects climate changes during that period.

5

Evolution of Brestovská Cave based on U-series dating of speleothems

Hercman H., Gradziński M., Bella P.

Geochronometria

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2008

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Vol. 32

1-12

EN

The U-series dating indicates five episodes of flowstone growth in Brestovská Cave, namely: ca. 200 ka, ca. 128-88 ka, ca. 82-65 ka, ca. 64-50 ka, and during the Holocene. The age of flowstones and their spatial distribution within the cave prove that the upper storey of the cave was dewatered before 200 ka. At that time the lower storey also existed and was able to carry the whole water flowing through the cave. It suggests that 200 ka ago the water-table was at similar level as it is at present. Hence, one should accept that the valley bottom was then also at the present level. During at least a part of the MIS 6 the growth of speleothems was possible in the cave. It suggests that the cave was located outside the permafrost zone then. Between 50 ka and Holocene, Brestovská Cave was flooded by invasion waters originating from the melting of the Würm glacier; the water-table was additionally raised due to the blockage of a resurgence by glacifluvial sediments. The flooding event caused the destruction of older deposits, including speleothems, and deposition of fine-grained clastics on the cave walls.

6

Uranium-series dating of marly sediments: application to Jaroszów fossil lake (SW Poland)

Debaene G.

Geochronometria

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2003

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Vol. 22

15-26

EN

A U-series (230Th/U) study was carried out on the carbonate sediments from the fossil lake of Jaroszów (SW Poland). Six marly samples of unit 5 have been dated with isochron method. Two procedures for obtaining sub-samples have been investigated, the Successive Leaching (SL) and the Full Leaching (FL). It appears that with SL method thorium isotopes are subjected to isotope fractionation. On the other hand, FL method presents no significant isotopic fractionation and gives a wide range of values for isotopic ratios, which is very convenient for plotting isochrons. A simple graphical representation of sample sub-sets was created to detect isotopic fractionation. Even though FL procedure is efficient, results are not in agreement with stratigraphy. Three possible explanations can be given for these stratigraphic inconsistencies: (1) detrital contamination, (2) open system, and (3) mixing of carbonates of different ages.

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Reconstruction of palaeoclimatic changes in Central Europe between 10 and 200 thousand years BP, based on analysis of growth frequency of speleothems

Hercman H.

Studia Quaternaria

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2000

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Vol. 17

35-70

EN

The present study is an attempt to utilise the uranium-thorium dates of speleothems as a source of palaeoclimatic data. The clue is that the changing climate influenced intensity of speleothem deposition, which is reflected in clustering of USeries dates of speleothems in certain time intervals. This work discusses and improves various methods of com bined presentation of dates, with a special attention to the presentation in form of growth frequency (`pdf') curves. Using the `bootstrap' method the confidence intervals of the `pdf' curves could be determined. Also the algorithm, originally developed to determine parameters of arbitrarily chosen maxima in the curve, has been modified. Due to that an assessment of number of maxima has been possible. This method enables objective distinction of phases of speleothem growth, which cannot be done `by eye' when the `pdf' curve is smooth. The statistical tests show that the reliable `pdf'curve should contain more than 150 dates. Basing on 308 Useries dates of cave speleothems from southern Poland and other regions of central Europe, the growth frequency curves for the Carpathians and Uplands have been constructed. Comparison of phases of speleothem growth, distinguished by various authors for several regions of Europe, indicates that the climatic changes were syn chronous over the whole region. However, different shapes of the `pdf' curves reflect increasing continuity of speleo them growth in the N-S transect southwards. This may be connected with the N-S climatic gradient in Europe. Using the `pdf' curves from caves of Tatra and Low Tatra Mountains the most probable timing of development phases of mountain glaciers has been delimited.