Porifera-microbialites of the Lower Liassic (Northern Calcareous ...

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Extensive quarrying over the last centuries opened numerous quarries that are scattered over the
entire reef area and expose parts of the Triassic buildup (Eisenmann Quarry and Tropf Quarry),
the T-J boundary transition (Lienbacher Quarry) as well as subsequent Liassic sediments
(e.g. Rot-Grau-Schnöll Quarry) in different paleobathymetrical settings (Fig. 13, 14).
Distal sediments comprise grey limestones that continuously pass the Triassic-Jurassic boundary,
whereas the slope and the top of the former reef are overlain by different Liassic red limestones,
that become more and more condensed towards the drowned reef core by an increasing number
of sedimentary breaks and ferromanganese crusts (Fig. 14). Their onset is represented by
conspicuous red limestones of the Hettangian Schnöll Formation, the lower part of which is
characterized by several spiculitic layers, showing dense populations of par- to autochthonously
preserved sponges. Due to their variegated color, the Schnöll limestones have for a long time
been used as popular decoration stones (“Schnöll-Marmor”). The most complete section is
exposed in the Langmoos Quarry (~13m), where sampling is complicated by a strong cover of
vegetation. Unfortunately its base is more or less hidden by small faults, and also in other old
quarries (Motzen-, Schmiede Quarry), it is currently not accessible. The Schnöll Formation is
best studied in the Rot-Grau-Schnöll Quarry (Adnet quarry no. XXXI, according to Kieslinger
1964).
Fig. 14. Schematic drawing of the onlap of the Schnöll Formation onto the drowned
Adnet Reef slope.
Due to the exposure of many different reef facies types and the exceptionally good possibility to
study large sections on sawn quarry walls, the Adnet reef area has raised to become a classic
locality for many field trips and is the cause for several papers about reef facies analyses and