Abstract A stratigraphic investigation of the coal-bearing Miocene siliciclastic succession
in structurally dissected basins of Northern Hungary was performed based on log correlations
and is supported by coal petrology and sulphur data. The succession represents the
Karpatian lower order global eustatic cycle of the Paratethys and was dissected into
six higher order sedimentary sequences (sq-1 – sq-6). The coal-bearing strata in the
Nógrád Basin (sq-1 – sq3) represent a lowstand systems tract (LST) prior to the Karpatian
relative sea level rise. The transgressive systems tract (TST) starts with the ‘Oncophora
Beds’ (sq-4) accumulated above a regional unconformity and containing coal beds in
the Borsod Basin. The TST is superimposed by tectonically-forced higher order lowstand
systems tracts (sq-5, sq-6) containing coal beds only in the relatively elevated East
Borsod Basin. To support the sequence stratigraphic model, the average maceral and
sulphur content of coal seams was also interpreted. The low sulphur (0.47%) content
in sq.-1 reflects the lowstand environment determined by continental derived freshwater
input. Transitional sulphur contents (0.66%–1.02%) in the late lowstand (sq-2 and
sq.-3) indicate occasional saline invasions related to relative sea level rises. High
(2.3%–2.6%) sulphur contents in the TST (sq-4) were caused by regular seawater inundations
into the lagoon, while decreasing sulphur contents in sq-5 and sq-6 (2.28%–2.09%)
reflect the increasing rate of freshwater income in association with the stepwise
basinward shifts of the shoreline and the lagoonal facies. Within the Lower to Middle
Miocene Salgótarján Lignite Formation, the analysis of coal seams contributed to the
interpretation of relative sea level changes, and the sequence stratigraphic context
facilitated both the interpretation of sulphur content in coals and the reliable correlation
of coal seams.
