Biostratigraphic revision of the Hód-I well

Hungary's deepest borehole failed to reach the base of the Upper Miocene Pannonian stage

Andrea Szuromi-Korecz, Mária Süto-Szentai, I. Magyar

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

Hungary's deepest borehole, Hód-I, was drilled in 1969-71 SE of the town of Hódmezovásárhely, in order to explore one of the thickest Neogene basin fills of the entire Pannonian Basin (the Makó Trough). The final depth of the well was 5842.5 m. According to earlier analyses of 45 core samples taken from die borehole, the lowermost 700 m was thought to belong to the Middle Miocene (Badenian and, possibly, Sarmatian Stages), whereas the overlying part was believed to belong to the Upper Miocene (deposits of Lake Pannon, Pannonian Stage), Pliocene, and Quaternary. In order to establish a more precise position of the Neogene stage boundaries, we carried out micropaleontological investigations on the 4100 to 5823 in interval (cores 25 to 45). Ostracods have been prepared by solution of the samples in acetic acid. Dinoflagellates were investigated in palynological preparations and in petrographic thin sections. It was found that core 34 (5070-5074 m), earlier thought to represent the base of the Pannonian Stage, in fact belongs to the younger part of the Lake Pannon sequence (Spiniferites validus Zone). Downwards to the base of the borehole, the Spiniferites paradoxus, Pontiadinium pecsvaradensis, and Spiniferites bentorii oblongus Zones were found, all belonging to the Pannonian. Accordingly, ostracods indicated the younger part of the Upper Miocene lacustrine sequence for the upper samples of the investigated interval, and older Upper Miocene down to core 44. Thus, the drilling failed to reach the base of the Pannonian Stage. The huge thickness (>6 km) of the postrift sediments above the relatively thin synrift stages (Badenian and ?Sarmatian) in the Makó Trough corroborates the notion that simple rifting models are not sufficient to adequately describe basin evolution in the central part of the Pannonian Basin.

Original languageEnglish
Pages (from-to)475-485
Number of pages11
JournalGeologica Carpathica
Volume55
Issue number6
Publication statusPublished - Dec 2004

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borehole
Miocene
Badenian
ostracod
Neogene
trough
basin fill
lake
basin evolution
thin section
basin
acetic acid
dinoflagellate
rifting
Pliocene
drilling
sediment
young

Keywords

  • Biostratigraphy
  • Dinoflagellata
  • Lake Pannon
  • Ostracoda
  • Pannonian Basin
  • Upper Miocene

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)

Cite this

Biostratigraphic revision of the Hód-I well : Hungary's deepest borehole failed to reach the base of the Upper Miocene Pannonian stage. / Szuromi-Korecz, Andrea; Süto-Szentai, Mária; Magyar, I.

In: Geologica Carpathica, Vol. 55, No. 6, 12.2004, p. 475-485.

Research output: Contribution to journalArticle

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abstract = "Hungary's deepest borehole, H{\'o}d-I, was drilled in 1969-71 SE of the town of H{\'o}dmezov{\'a}s{\'a}rhely, in order to explore one of the thickest Neogene basin fills of the entire Pannonian Basin (the Mak{\'o} Trough). The final depth of the well was 5842.5 m. According to earlier analyses of 45 core samples taken from die borehole, the lowermost 700 m was thought to belong to the Middle Miocene (Badenian and, possibly, Sarmatian Stages), whereas the overlying part was believed to belong to the Upper Miocene (deposits of Lake Pannon, Pannonian Stage), Pliocene, and Quaternary. In order to establish a more precise position of the Neogene stage boundaries, we carried out micropaleontological investigations on the 4100 to 5823 in interval (cores 25 to 45). Ostracods have been prepared by solution of the samples in acetic acid. Dinoflagellates were investigated in palynological preparations and in petrographic thin sections. It was found that core 34 (5070-5074 m), earlier thought to represent the base of the Pannonian Stage, in fact belongs to the younger part of the Lake Pannon sequence (Spiniferites validus Zone). Downwards to the base of the borehole, the Spiniferites paradoxus, Pontiadinium pecsvaradensis, and Spiniferites bentorii oblongus Zones were found, all belonging to the Pannonian. Accordingly, ostracods indicated the younger part of the Upper Miocene lacustrine sequence for the upper samples of the investigated interval, and older Upper Miocene down to core 44. Thus, the drilling failed to reach the base of the Pannonian Stage. The huge thickness (>6 km) of the postrift sediments above the relatively thin synrift stages (Badenian and ?Sarmatian) in the Mak{\'o} Trough corroborates the notion that simple rifting models are not sufficient to adequately describe basin evolution in the central part of the Pannonian Basin.",
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AU - Magyar, I.

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