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

Localities (Facies and Sponge Analyses) 35
� The Triassic-Jurassic boundary section exhibit a Triassic coral limestone, the top of which is
affected by corrosion and partially covered by thin ferromanganese crusts. The onset of Jurassic
sedimentation is shown by only a few centimeters of Schnöll limestone which is mostly covered
by the Fe/Mn crust of the Schlotheimia marmorea zone. Sometimes both pinch out or are limited
to the infill of larger cracks that penetrate the Triassic base up to about half a meter. Due to the
findings of several ammonites, Böhm et al. (1999) were able to attribute the Schnöll limestones
at Lienbacher Quarry to the Guggen Member, because the reef top here displays a hiatus in
sedimentation that covers the period from about Lower to Middle Hettangian.
� The small layer of Schnöll limestone at Lienbacher Quarry displays red biomicrites (wacke-
to packstones) with debris of crinoids, formaminifers and ostracods. As a characteristic feature,
the sediment encompasses a high ratio of corroded and ferromanganese impregnated clasts,
which are predominantly formed by red biomicrites with shell debris and less frequently isolated
hexactin sponge spicules.
� Altogether sponge remains are rare, thus taken samples from the Liassic base (red limestones
of the Schnöll Fm. and from Fe/Mn crusts) were primarily used for geochemical analyses
(chapter 8.)
� The Lienbacher section is described by Böhm (1992) and Böhm et al. (1999).
Sponge Analyses:
Fig. 16. Schematic sketch of a sawn
quarry wall (about 5-6m high) in the
northwestern part of Adnet/Lienbacher
Quarry (see also Pl. 15A).
sf: Schnöll Formation (Middle Hett.,
Guggen Member),
m: marmorea crust (Mid.-Up. Hett.),
sc: Basal Sinemurian Crust,
dws: deep water stromatolites.
Samples of Liassic limestones L 1-13
were taken from the top and from the
infill of cracks of the Triassic reef
limestone.
� All noticed spicules are broken monaxons and hexactins of most likely dislocated, non-rigid
hexactinellids. Sponges did not settle on the firmgrounds of the corroded reef body surface.