Facies transition and biostratigraphic correlation of the Upper Silurian and Lower Devonian in West Bulgaria

Authors

  • Iliana Boncheva Bulgarian Academy of Sciences, Geological Institute, Acad. G. Bonchev Str., Bl.24, Sofia 1113, Bulgaria
  • Valeri Sachanski Bulgarian Academy of Sciences, Geological Institute, Acad. G. Bonchev Str., Bl.24, Sofia 1113, Bulgaria
  • Iskra Lakova Bulgarian Academy of Sciences, Geological Institute, Acad. G. Bonchev Str., Bl.24, Sofia 1113, Bulgaria
  • Marlena Yaneva Bulgarian Academy of Sciences, Geological Institute, Acad. G. Bonchev Str., Bl.24, Sofia 1113, Bulgaria

Keywords:

Bulgaria, Upper Silurian, Lower Devonian, conodonts, graptolites, facies transition

Abstract

Upper Silurian and Lower Devonian shelf deposits in West Bulgaria are exposed in three main Alpine tectonic units: the West Balkan Unit, the Lyubash Monocline and the Morava Unit. The West Balkan and Lyubash units consist of siliciclastic deposits: black graptolitic shales, banded pale shales and black siltstones. The Ludlow, Pridoli, Lochkovian, Pragian and Emsian were recognized on the basis of graptolite and tentaculite faunas. In the Morava Unit, the Ludlow black shales are progressively replaced by clayey limestones and nodular and micritic limestones in the Pridoli and Early Devonian. Newly obtained conodonts show the presence of the siluricus, eosteinhornensis, woschmidti, postwoschmidti, delta-pesavis, sulcatus, dehiscens and gronbergi zones. Petrographic study of the Morava Unit shows an increasing carbonate content and shallowing conditions upwards. The biostratigraphical correlation and facies interpretation reveal the coeval existence of two different depositional environments within the same shelf basin as well as a gradual shift in proximal direction.

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Published

2010-03-27

Issue

Vol. 51 No. 4 (2007)

Section

Articles

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