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

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� The Lower Liassic sediments from Adnet Quarries and Steinplatte/Plattenkogel hill show a
small but distinct negative δ 13 Ccarb-excursion persisting during the Hettangian and presumably
ending in Lower Sinemurian time. Beside an overprint of global biogeochemical processes this
excursion was probably locally influenced by bacterial sulfate reduction during organic matter
degradation and automicrite formation in the sponge biomass.
� Lower Liassic ferromanganese crusts of the Northern Calcareous Alps show a distinct
positive Ce-anomaly and a small positive Gd-anomaly, except for one from Steinplatte /
Plattenkogel locality. The latter is characterized by a negative Ce-anomaly, a small negative Gd-
anomaly and slightly augmented Eu values, all found in the crust material as well as in the
overlying Liassic spiculite. Positive Ce-anomalies in the crusts are interpreted as scavenging
effects due to absorbtion of oxidized Ce by the high amounts of Fe/Mn-oxyhydroxides. The
origin of the negative Ce-anomaly remains unclear. Its correlation with a small Eu-anomaly
suggests diagenetic influence by (hydrothermal?) fluids.
� There is no correlation between sponge settlement and geochemical data, thus colonization
was exclusively controlled by sedimentation rate and water regime.