Page 35 - Carbonate Sedimentology and Sequence Stratigraphy

26 WOLFGANG SCHLAGER

A)
a

fc

s a

bc

a
ac? a

B) C)

Fig. 2.17.— A) Thin-section of automicrite facies (long side = 1.5 mm). Dark automicrite, (a), with clotted or pelleted texture provides
a basic framework and supports a large cavity filled by inclusion-rich, brownish fibrous calcite (fc) and muddy sediment, (s). Other parts
of the cavity are filled by (late) blocky calcite (bc) and some questionable fibrous aragonite, (ac?). Close intergrowth of automicrite and
fibrous calcite in upper left and lower right. Triassic, Southern Alps, Italy. After Russo et al. (1997), modified. B) Thin section of clotted
and pelleted automicrite with primary pores filled by late blocky calcite. Plane-polarized light. C) Epifluorescence image of thin section
in B.. Fluorescence is induced by organic matter. Automicrite fluoresces considerably, blocky cement remains dark. High content of
(primary) organic matter is characteristic of automicrite. Triassic, Molignon Hut, Southern Alps, Italy. Images B and C by L. Keim, outcrop
documentation in Brandner et al. (1991).
mud-mound platform in shallow water oxygen
after major extinctions photic production Fig. 2.18.— Environmental setting of the ma-
nutrients rine M factory. The factory is best developed in
sea level the nutrient-rich waters of the thermocline but
fair weather wave base may extend into the zone of wave action if the T
factory is weak. Below the zone of wave action,
storm wave base
accumulations usually are mounds, in the zone
of wave action they become flat-topped plat-
forms. Mud-mounds connected to cold seeps or
begin of flattening by waves
hot vents may deviate from these environmental
requirements. After Schlager (2003), modified.
typical mud-mound setting:
deeper water, high nutrients, low oxygen