A kállai kavics települési helyzete a tapolcai-medencében geoelektromos szelvények és fúrási adatok tükrében

Csillag Gábor, Sztanó Orsolya, Magyar Imreés, Hámori Zoltán

Research output: Article

17 Citations (Scopus)

Abstract

Gravel, pebbly sand, clean quartz-sand and sandstone - all formed in Lake Pannon - crop out in the vicinity of the Keszthely Hills, Tapolca and Kál Basins; as a geological unit, this is referred to as the Kálla Formation. Up until now its stratigraphic position, its relation to underand overlying formations, as well as to the similar, but virtually older Kisbér Gravel have not been determined with any degree of certainty. Based on descriptions of old wells and sedimentological and stratigraphic data with respect to outcrops, geoelectric measurements were carried out and geological cross-sections were compiled in order to ascertain its stratigraphic relations. Deposits underlying the Kálla Gravel consist of Triassic carbonates, mid-Miocene limestones, pebbly limestones and the Congeria czjzeki-bearing Szák Claymarl. The Kálla Formation is unconformably overlain by silts and sands of the Somló Formation and in some wells by the Tihany Formation (which contains coaly clay beds). The Late Miocene depositional history of the Tapolca Basin can be reconstructed as follows. At about 11-10 Ma, when the lower part of the Szák Claymarl was formed, the area of the present Transdanubian Range was a large peninsula in Lake Pannon. At its southern rim a small, tectonically preformed embayment was created. Around about 10 Ma ago the lake transgressed northwards due to a relative lake-level rise and on the newly-flooded areas small coarse-grained deltas (Kálla Formation) began to form due to small rivers draining the Transdanubian Peninsula. Along the rim of the peninsula several distinct, but coeval gravelly shoreface deposits (Kisbér Gravel) may have been formed. Near to the entry points of rivers (at the deltas) the sedimentation rate compensated and even exceeded the rate of lake-level rise; thus the gravelly-sandy deltaic bodies prograded over the clays, which formerly were deposited below the wave-base. In front of the coarse-grained deltas, the deposition of silts and clays continued. Therefore the Kálla and Szák Formations are partly coeval in the Tapolca Basin. Approximately 9.5-9 ma ago a significant change occurred. Earlier, the sediments were derived from minor local sources (i.e. from the Transdanubian Peninsula); later, following the filling up of the Danube Basin, sediments were derived from the Alps and the Western Carpathians. The major north-western drainage system entered Lake Pannnon as extended deltaic lobes, represented by the silty-sandy beds of the Somló Formation (prodelta and deltafront regions). Parallel with progradation, 9-8 Ma ago the deltaplain corresponding to the Tihany Formation appeared. The overlying alluvial deposits were removed by the Quaternary uplift of the area. With respect to the lithostratigraphic units, it can be concluded that the Szák Claymarl, Kálla and Kisbér Gravels were formed during the same transgressive event. The stratigraphic position of the gravelly formations is different only because of the local variations in sediment input rates. Whereas their source area was the same and their petrographic composition is almost identical. Within the frame of biostratigraphic resolution they are coeval at about 10 Ma and both were formed on the margin of the Transdanubian Peninsula. It is impossible to differentiate the two deposits by geological mapping - therefore their integration as the Kálla Formation is suggested. The Szák Formation, however, is not only a local deposit but can be seen as part of a large clayey lithosome in the fill of Lake Pannon, corresponding to the Endro{double acute}d and Algyo{double acute} Formations. Therefore its timespan over the whole of the Pannonian Basin equals the Late Miocene.

Translated title of the contributionStratigraphy of the kálla gravel in tapolca basin based on multi-electrode probing and well data
Original languageHungarian
Pages (from-to)183-196
Number of pages14
JournalFoldtani Kozlony
Volume140
Issue number2
Publication statusPublished - júl. 19 2010

Keywords

  • High sediment input rate
  • Lake pannon
  • Lake-level rise
  • Multielectrode probing
  • Regression
  • Transgression
  • Upper miocene

ASJC Scopus subject areas

  • Geology
  • Geochemistry and Petrology
  • Stratigraphy
  • Palaeontology

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