Page 140 - Carbonate Facies in Geologic History

Devonian of the Eifel 127

Dortmund
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Fig.IV-19. Types of buildups and their tectonic positions in the Middle Devonian of the
Rhenish Schiefergebirge. From Krebs (1974, Fig. 12). Black areas are outcrops. Black line
separates trough to east from shelf to west; cross-hatch in lower right indicates basinal
buildups over volcanic highs in Variscan geosynclinal trough (Type 1 b); cross-hatch in upper
right marks buildups at shelf margin, edge of cratonic block (Type 2 b); light dot in upper left
marks buildups in interior of shelf (Type 3c); light dot in lower left indicates biostromes,
continuous reefy beds on shelf (also Type 3c). The buildup types given here are those of the
tectonic classification of Krebs and Montjoy (1972) and the author. Krebs (1971) termed them
as follows (Types A, B 1, B2, and C). Illustration with permission of author and Society of
Economic Paleontologists and Mineralogists

Devonian of the Eifel

An important eastward continuation of the classical Belgian Devonian exists in
the Rheinish Shale Mountains in the Eifel district of West Germany. The tectonic
setting here is similar to that of the Brabant massif and its southern narrow shelf
but it is more complex and was subjected to much greater subsidence. A strong
northeast-southwest linearity suggests basement faulting as a control of buildups.
Studies by Jux (1960) and Krebs (1971) show a shelf area bordering the northern
massif (Fig. IV -19). East of the Rhine this area subsided as a marginal miogeosyn-
clinal shelf. The normal interreef facies (Schwelm) consists of well-bedded dark
limestone and shales with some terrigenous clastics. Isolated elongate NE-SW
carbonate masses and buildups occur along this shelf (Dorp Facies). Buildups