Porifera-microbialites of the Lower Liassic (Northern Calcareous ...
Porifera-microbialites of the Lower Liassic (Northern Calcareous ...
Porifera-microbialites of the Lower Liassic (Northern Calcareous ...
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Plate 18<br />
Steinplatte / Plattenkogel –<br />
Features <strong>of</strong> <strong>the</strong> spiculite layer at Plattenkogel hill.<br />
(A): Typical cross section <strong>of</strong> <strong>the</strong> spiculite layer. Spicular mats with collapsed sponges (white<br />
arrows) are separated by different networks <strong>of</strong> stromatactoid cavities. Successive phases <strong>of</strong><br />
compaction and sediment infiltration during syndiagenetic tilting are distinguishable (black<br />
arrows).<br />
(B): Cross section <strong>of</strong> 3 spicular mats. The intraclast in <strong>the</strong> center was hold in place by<br />
microbially fixed carbonates while below compaction <strong>of</strong> spongy horizons took place.<br />
Upper part <strong>of</strong> <strong>the</strong> spiculite is characterized by strongly collapsed sponges and densely<br />
associated micro-stromatactis cavities.<br />
(C): Detail <strong>of</strong> spicular mat showing <strong>the</strong> usual succession <strong>of</strong> a collapsed lyssacinosid sponge (ly),<br />
compacted sediment (cs), reworked micropeloidals (mp) and aborted stromatactis (as),<br />
sensu Neuweiler et al. 2001b, with radiaxial fibrous cements.<br />
(D): Intraclast <strong>of</strong> <strong>the</strong> Pecten-layer with ferromanganese incrustations. An eroded gap was<br />
colonized by a lyssacinosid sponge (ly).
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