Page 248 - Carbonate Facies in Geologic History

Tectonic Control of Regional Facies and Thickness in the Dolomites 235

D
0 , 10 20 30 '0 50 "., 1 AlluvIal plaIn
,
,
,
,
,
D Jurassic
2 Teniaryand
3 Troas Wllh
buildups
4 PermIan
Ignombrlles
5. Melamorphlc
basemenl

f~f.,gif-~.:j 6. Intrusions

7 Major faulls
8 Teclonlc
boundary ollhe
Soulhern Alps
IlIuslfalion counesy
of aUlhors and
Socielvof
EconomIC
Paleonlologlsls and
Moneraloglsls

Fig.VIII-I1. Regional geological setting of the Dolomites from Bosellini and Rossi (1974,
Fig. 2).

The stratigraphic section for the Triassic of these regions is given in Fig. VIII-
12. The total Triassic in the western Dolomites is more than 2000 m thick-and in
the eastern Dolomites much greater.

Tectonic Control of Regional Facies and Thickness in the Dolomites
Three natural regions may be distinguished in the Dolomites: (1) an area of thick-
bedded limestone and dolomite in the area of the Adige River Valley, west of the
Dolomites proper, (2) the area of the western Dolomites, east of the Isarco River
and the city of Bolzano (Bozen) where great isolated banks rise from a plateau,
and (3) a formerly unified platform of thick-bedded massive Triassic limestone
and dolomite also deeply dissected by erosion and lying still farther east around
Cortina d'Ampezzo, the eastern Dolomites.
Apparently movement on or around a basement fault block controlled the
location of the series of great banks comprising the western Dolomites but the
cause oflocation of individual banks is not very clear. According to Bossellini (in
Leonardi, 1967), the oldest Triassic Werfen beds, which constitute a variable
sequence of terrigenous clastics and limestone, measure only a few meters in the
Gardena Pass area of the western Dolomites but thicken eastward to about 500 m
in the eastern Dolomites. A pronounced area of very thin, earliest Triassic beds is
shown on Fig. VIII-14 and interpreted to represent a north-south positive area.