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The Devonian-Carboniferous boundary : comparison between the Dinant Synclinorium and the northern border of the Rhenish Slate Mountains : a sequence-stratigraphic view
A comparison of the Devonian-Carboniferous transitional interval at the northern border of the Rhenish Slate Mountains with that in the Belgian Dinant Synclinorium shows how the different litho- and biostratigraphic patterns in both areas can be related to the same relative sea-level fall.
A biostratigraphic hiatus near the Devonian-Carboniferous (praesulcata-sulcata conodont) boundary has been associated with a basinward shift of the lithofacies in the mixed carbonate-siliciclastic ramp setting of the Belgian Dinant Synclinorium. The fades shift resulted from a relative sea-level fall at the end of the Devonian. In the neighbouring northern border of the Rhenish Slate Mountains, where the slopes of Devonian reef complexes are exposed, the Devonian-Carboniferous boundary is obliterated in a different way. In such settings either condensed sections occur, or the upper part of the deep-water praesulcata range is truncated by shallow-water strata carrying a different conodont biofacies. This paper suggests that the relative sea-level fall recorded in the Dinant Synclinorium is also responsible for the incision of shoal and slope areas (Seiler Channel) and for the subsequent lowstand fill (Seiler Conglomerate, Hangenberg Shale and Sandstone, Stockum Sandstone), in the Rhenish Slate Mountains. These lowstand deposits are devoid of the deep-water conodonts that currently define the D/C boundary. A deeper-water fauna, consisting of Carboniferous assemblages, was re-established only after a further relative sea-level rise (Hangenberg Limestone and Liegende Alaunshiefer), and now provides good biostratigraphic control.
Understanding the litho- and biostratigraphic response to different rates of relative sea-level change may help to refine lateral correlations within D/C boundary intervals of non-conclusive biostratigraphic control, both within and between different basins.
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A propos de : Mia Van Steenwinkel
P.D.O., P.O. Box 81, Muscat, Sultanate of Oman.