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Fig. 8. Photomicrographs of sediment of tablets in fast flowing water areas. (a), (b) and (c): from thin sections. The
thickness of the cool and warm period sediment obtained with the MEM is indicated. (a) and (b) from tablet 3. (c) from
tablet 5. In (c) arrows point to the dense cyanobacterial fabric of the upper half of the warm period of 2001. (d), (e), (f),
(g) and (h): images from SEM. (d): Subperpendicular calcite microbial tubes arranged as laminae. The fine tubes at the
base correspond to the warm period of 2002 and the overlying thick ones (arranged as bush-like groups) to the cool
period of 2002 - 2003. An erosion phase separates them (arrowed surface). (e) and (f): Thick calcite microbial tubes
arranged in subvertical, coalescent bush-like groups (e) and in subhorizontal groups as a massive network (f). Calcified
filaments (fi) indicated by arrows. Both correspond to sediment of cool periods. Notice in (f) the overgrowth of the tubes.
(g) and (h): Thin calcite microbial tubes arranged in subvertical, coalescent groups (g) and in subhorizontal groups in a
massive network (h). Both correspond to sediment of warm periods.
mosses or other macrophytes. This facies is made of
millimetre to 1 - 2 centimetre-thick laminae and
layers, commonly marked by differences in colour
and/or thickness, and ocassionally by variations in
porosity, crystal size and biological components.
Laminae range from roughly tabular to smoothly
domed (Fig. 5b, d, f). It is formed of micrite and
spar calcite tube-like bodies, in which the empty
center correspond to decayed microbes, presumably
cyanobacteria, and less common of calcified
microbial filaments and pennated diatoms; spar
and less common micrite calcite is present among
these components (Fig. 8a, b, c). The cyanobacterial
tube-like
bodies
are
either
perpendicular
to
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