12 research outputs found
Integration of new and revised chronological data to constrain the terrace evolution of the Danube River (Gerecse Hills, Pannonian Basin)
Terrace ages deduced from diverse geochronological records yielded inconsistent data in the Danube valley in
Hungary. The problem of discrepancies in the different chronological datasets has to be resolved before the Quaternary
tectonic and climatic processes leading to valley incision and terrace formation may be properly evaluated.
To establish a more robust chronology of the Danube valley in Hungary, new cosmogenic nuclide- (10Be depth
profiles, 26Al/10Be burial durations and burial depth profile) and luminescence-based (pIRIR290) terrace ages
were acquired and compared to revised paleontological and published U/Th and magnetostratigraphic data. All
the applied geo-chronometers led to concordant terrace ages, with the exception of the U/Th method applied on
travertine deposits covering terraces. U/Th ages predating the last interglacial manifest a bias towards younger
ages, and so they were ignored in relation to the quantification of terrace ages. As a result, terrace ages from
the Late Pliocene to Late Pleistocene were settled. With regard to data from the Middle Pleistocene onwards, the
combination of diverse methodologies led to a tighter bracketing of terrace ages than would be possible using
a single dating method. The modelling of cosmogenic 26Al and 10Be concentrations enabled to derive surface
denudation rates and their combination with paleontological data also allowed us to decide between diverse
landscape evolution scenarios
Integration of new and revised chronological data to constrain the terrace evolution of the Danube River (Gerecse Hills, Pannonian Basin)
International audienc
Recommended from our members
Fluvial magnetic susceptibility as a proxy for long-term variations of mountain permafrost development in the Alp-Carpathian region
Low field magnetic susceptibility (MS) records of 13 reference boreholes representing the whole Quaternary fluvial succession of the Great Hungarian Plain were correlated to develop regional stratigraphy. Data from 12 of
the boreholes were published between 2016 and 2020, the Tiszainoka borehole is newly reported in this paper. Eleven magnetic susceptibility cycles, capped by the most emergent master MS peaks (MP) and bordered by susceptibility termination surfaces, have been correlated. Supported by the already evaluated palaeomagnetic reversals and instability events, MPs have been correlated to the cold stages of the marine isotope stage (MIS)
records. MPs represent MIS 104, 100, 98, 82, 60, 52, 34(-36) and 26 of increased heavy oxygen isotope value, constituting the significant Early Pleistocene glaciations, and MIS 18, 16, 12, 8, 6 and 2 mostly representing the substantial Middle and Upper Pleistocene European glaciation events. The interpretation of early postglacial fluvial MS maxima, that emphasise the escape of weathering-sensitive magnetic minerals from the catchment
area triggered by the thawing of mountain permafrost, is confirmed by the correlation of MPs to the changes of the global ice volume. As a result, fluvial MS records can be considered as a proxy for mountain permafrost
development in the catchment areas. Regional correlations confirmed that the Körös and Jászság Basins and the Makó Trough are sites of almost continuous fluvial records of the past 2600 ka. Thus, the Pannonian Quaternary fluvial succession is sufficiently complete to provide satisfactory record of mountain permafrost development of the Alp-Carpathian region the latter being a globally relevant European representative of mid-latitude mountain regions. The similarity of the Pannonian fluvial MS succession as a permafrost proxy to the marine ice-rafted detritus (IRD) and Chinese loess/palaeosol MS records promises the possibility of comparative investigations of globally relevant proxy records and mid-latitude mountain permafrost development
Recommended from our members
Obliquity-driven mountain permafrost-related fluvial magnetic susceptibility cycles in the Quaternary mid-latitude long-term (2.5 Ma) fluvial Maros Fan in the Pannonian Basin
Magnetic susceptibility (SUS) of the Quaternary long-term mid-latitude Maros fluvial fan (Pannonian Basin) was recorded to understand the stratigraphic features of source proximal fluvial depositional settings. Three fully cored 500 m deep boreholes were sampled with 0.5 m intervals; low field and frequency dependent magnetic susceptibility were measured, and complementary hysteresis and SEM-EDAX investigations were performed on selected samples. Logged SUS data were also used to log correlations established by a comparison of wireline log and laboratory measurements. The time-series analyses of the SUS records reveal the apparent occurrence of the ~41 ka frequency together with the customary ~100 ka cycles. Towards the source-distal sections the intensity of the ~41 ka cycles decreases, while that of the ~100 ka cycles remains strong. Stratigraphic and spectral similarities were observed between fluvial fan and loess SUS records ; however, based on complementary magnetic data, the magnetic phase of the Maros Fan sections is related to the detrital magnetite that originates from the catchment during early postglacial permafrost degradations. The amplification of the ~41 ka cycles revealed can be attributed to the very high SUS values in source proximal settings and to the special stratigraphic feature of the distributive fluvial settings. This comprises the increased avulsion frequency on the fluvial fans in ‘glacial recession periods’, in concert with the ‘early postglacial’ occurrence of the permafrost-related magnetite originated from the catchment. As a local phenomenon, this is significant since it records the obliquity-driven variations of permafrost development in a catchment. However, fluvial and alluvial fans are widespread depositional landforms within the Eurasian Mountains and were possibly the same during the Quaternary deglaciations. Thus, obliquity-driven SUS variations of source-proximal fan deposits attached or adjacent to regions of loess deposition should also be considered when scanning for potential source material of aeolian deposits
Comparability of heavy mineral data – The first interlaboratory round robin test
Heavy minerals are typically rare but important components of siliciclastic sediments and rocks. Their abundance, proportions, and variability carry valuable information on source rocks, climatic, environmental and transport conditions between source to sink, and diagenetic processes. They are important for practical purposes such as prospecting for mineral resources or the correlation and interpretation of geologic reservoirs. Despite the extensive use of heavy mineral analysis in sedimentary petrography and quite diverse methods for quantifying heavy mineral assemblages, there has never been a systematic comparison of results obtained by different methods and/or operators. This study provides the first interlaboratory test of heavy mineral analysis. Two synthetic heavy mineral samples were prepared with considerably contrasting compositions intended to resemble natural samples. The contributors were requested to provide (i) metadata describing methods, measurement conditions and experience of the operators and (ii) results tables with mineral species and grain counts. One hundred thirty analyses of the two samples were performed by 67 contributors, encompassing both classical microscopic analyses and data obtained by emerging automated techniques based on electron-beam chemical analysis or Raman spectroscopy. Because relatively low numbers of mineral counts (N) are typical for optical analyses while automated techniques allow for high N, the results vary considerably with respect to the Poisson uncertainty of the counting statistics. Therefore, standard methods used in evaluation of round robin tests are not feasible. In our case the ‘true’ compositions of the test samples are not known. Three methods have been applied to determine possible reference values: (i) the initially measured weight percentages, (ii) calculation of grain percentages using estimates of grain volumes and densities, and (iii) the best-match average calculated from the most reliable analyses following multiple, pragmatic and robust criteria. The range of these three values is taken as best approximation of the ‘true’ composition. The reported grain percentages were evaluated according to (i) their overall scatter relative to the most likely composition, (ii) the number of identified components that were part of the test samples, (iii) the total amount of mistakenly identified mineral grains that were actually not added to the samples, and (iv) the number of major components, which match the reference values with 95% confidence. Results indicate that the overall comparability of the analyses is reasonable. However, there are several issues with respect to methods and/or operators. Optical methods yield the poorest results with respect to the scatter of the data. This, however, is not considered inherent to the method as demonstrated by a significant number of optical analyses fulfilling the criteria for the best-match average. Training of the operators is thus considered paramount for optical analyses. Electron-beam methods yield satisfactory results, but problems in the identification of polymorphs and the discrimination of chain silicates are evident. Labs refining their electron-beam results by optical analysis practically tackle this issue. Raman methods yield the best results as indicated by the highest number of major components correctly quantified with 95% confidence and the fact that all laboratories and operators fulfil the criteria for the best-match average. However, a number of problems must be solved before the full potential of the automated high-throughput techniques in heavy mineral analysis can be achieved