Page 250 - Carbonate Facies in Geologic History

Tectonic Control of Regional Facies and Thickness in the Dolomites 237

Fig. VIII-14. Isopachous map in meters of the Werfen beds showing earlier Permo-Triassic
positive element in relationship to Dolomite banks. Larger banks seem to have formed down
flanks of positive area. After Leonardi (1967, Fig.218 by A. Bosellini)

carbonate platform across the total Dolomite area but thins from 30-100 m
around the Atesino high. In the trough to the east the Serla is from 500-1000 m
thick. From the Serla Dolomite platform rise the great isolated Ladinian banks,
shaping the fantastic landscape of the western Dolomites. To the east, the Serla is
separated from the Ladinian Sciliar (Schlern) dolomite by a relatively thin se-
quence of marine argillaceous strata with ammonites and brachiopods, the Trinodo-
sus beds. In the western Dolomites these beds are of lagoonal facies. Thus Lad-
inian carbonate deposition was initiated in very shallow water and kept pace in
many places with a pronounced subsidence. An arc of great carbonate banks
formed in the western Dolomites. The northern banks, the Gardinaccia and Sella
Groups, lie over, and just east of the crest of the Atesino high (Figs. VIII-14 and
II -7). The southern members loop around the south flank of the positive area
(Marmolada-Catinaccio-Sciliar-Latimar-Agnello Banks). West 'of the site of the
great isolated banks, thick, more or less continuous Middle Triassic strata exist in
the Adige River area. Here a wide platform existed whose limestones are charac-
terized especially by diplopore dasycladacean algae, indicating banks with re-
stricted circulation. Likewise, east of the western Dolomite banks a thick single
platform of Ladinian dolomite formed, filling in the trough of the eastern Dolo-
mites. These wider platforms east and west of the Atesino high seem to have grown
around it as a halo; the individual, smaller banks developed on its top.
The Ladinian banks are now separated by a thick sedimentary sequence,
mostly volcanic, which filled in deep areas between them. Under the volcanics in
the intervening basins lies a dark basinal facies, termed the Livinallongo or Bu-
chenstein strata. These rocks are mainly nodular and bituminous limestone with