Geology Reference
In-Depth Information
Adnet case study (Pl. 139):
The Adnet limestones
are variously bedded and nodular, red and gray lime-
stones occurring in the central northern part of the Aus-
trian and Bavarian Northern Calcareous Alps. The lime-
stones exhibit all the microfacies criteria typical of pe-
lagic carbonates deposited in different water depths be-
low the photic zone (Fig. 15.36 on Pl. 139).
Microfacies of the peri-Mediterranean Late Jurassic-
Early Cretaceous Aptychus and Biancone limestones
The facies of the Late Jurassic Oberalm Formation
in the Northern Calcareous Alps is an example of pe-
lagic limestones widely distributed in the Alpine-Medi-
terranean region and better known under the names
Aptychus
limestones and Biancone. The facies is char-
acterized by well-bedded, white micritic limestones,
sometimes with marly partings and cherts. The carbon-
ates comprise radiolarian limestones (Fig. 15.34; Pl.
76/1), calpionellid limestones (Fig. 10.30) and nanno-
fossil limestones with coccolithophorids and nanno-
conids (see Fig. 4.4).
The biotic composition and close association with
radiolarites indicate deposition in very deep bathyal ba-
sins. Intercalations of turbidites (e.g. Barmstein lime-
stones within the Oberalm limestones; Sect. 15.7.3.4)
are common.
The Early Cretaceous Biancone Formation consists
of cherty, white to rose nannofossil micrite with cal-
cite-replaced radiolarians and calpionellids.
Fig. 15.34.
Radiolarian limestone.
This example corresponds
to the deposition site E of Fig. 15.30. The sample shows abun-
dant radiolarians and sponge spicules. Note the different pres-
ervation of spumellarian and nasselarian radiolarians; some
still exhibit characteristics of the test, whereas others are com-
pletely calcitized or infilled with micrite. Late Jurassic
(Oberalm Formation, Tithonian): Hallein, Austria.
Microfacies of the Cretaceous Scaglia facies of the Ve-
netian Alps, Italy
The facies of the Cretaceous Scaglia Rossa Forma-
tion (Fig. 15.35), overlying the Biancone Formation,
is an example of Late Cretaceous pelagic limestones
that are widely distributed all over the Mediterranean
region.
The thin and evenly bedded micritic limestones of
the Venetian Alps are typically developed as pink to
red, slightly nodular skeletal wackestones rich in pe-
lagic foraminifera and nannofossils. Trace fossils and
Fig. 15.35.
Pelagic limestone with abundant planktonic foraminifera.
Scaglia Rossa. This example corresponds to the depo-
sition site B shown in Fig. 15.30. The sample is a bioclastic wackestone. All skeletal grains are shells of planktonic foramin-
ifera or their debris. Late Cretaceous: Sirmione, Lake Garda, northern Italy.
