Page 251 - Carbonate Facies in Geologic History

238 Permo-Triassic Buildups and Late Triassic Ecologic Reefs

N ~.~-------------------- 9km long s

Terroro.o Vojolet Cotinoccio Forcello Mo.or.
lummit Towers

80 nk Interior South Flonk
COltalungo
Pall
'
~ onkoid ~ ivalve. ~ Thecolmilia '
B
L.LJ dend roid coral
~ crinoid Ii] Oiplopor.
Do Iyclad acea n
Fig. VIII-15. Fauna and flora across the Catinnaccio-Sciliar bank from north to south. Note
presence of dendroid "T hecosmilia" and onkoids all along bank and dasyc\adacean and large
bivalves in interior lagoon at Vajolet Towers. Vertical exaggeration only X 1.5. From Leon-
ardi (1967, Fig. 128-a traverse by D. Rossi)

greenstones (altered volcanic tuffs). The limestone is highly siliceous and cherty
and contains radiolarians; it has graded beds, lamination, microbreccias and
slump structure. It contains abundant remains of Daonella, a bivalve of probable
nektonic habit. These strata clearly represent deeper water euxinic deposits
formed between the buildups as they grew. Beneath the banks the Livinallongo is
thin as if the banks grew on areas of slight buildups of the underlying Serla
Dolomite. Lateral to the banks, the Livinallongo strata thicken basinward up to
200 m, replacing the dipping forereef transition beds and forming the starved
basin facies during the time of maximum subsidence (Fig.VIII-lS) and bank
growth (Bosellini and Rossi, 1974).
The great banks of the western Dolomites grew as much as 700-1500 m high.
Some are roughly circular with a diameter of several kms. Owing to the gentle
folding and faulting of the Teritary orogeny in the South Alps, they are still more
or less in place. Foreslope talus dips off them from 10 to 30 degrees. Present
erosion has preserved many of the original depositional slopes because the inter-
bank, infilling strata are easily eroded compared to the massive dolomite and
limestone. One can trace these transition beds, (Uberguj3schichten of M ojsisov-
ics), upward from the basin into completely unbedded dolomite along the edge of
several banks. The profile of the bank edges range from almost vertical to inward-
retreating or outward-growing, depending on the ability of organic growth to
compete with subsidence and ingress of volcanic-clastic material (Fig. 11-17).
These flanking beds are composed of coarse nodular dolomite with abundant
cavities and much coarse fibrous calcite infill (stromatactoid-structure or Evino-
spongia of earlier authors).