Factors controlling growth of modern tufa: results of a field experiment - Tufas and Speleothems: Unravelling the Microbial and Physical Controls - page 163

Fig. 15. (a) Diatoms on tufa surface, Karw ´ w cascade point March 2003; (b) diatoms and EPS on tufa surface, note
small clots of anhedral calcite crystals, H ´ j dam point, May 2002; (c) diatom rich layer in the topmost part of tufa
deposited between November 2002 and March 2003 in H ´ j dam point on limestone tablet; (d) diatoms on tufa surface,
L ´ˇ ky E site, note the nucleation of small calcite crystals directly on the frustules (arrows), March 2003; (e) diatom
frustule mould (arrow), L ´ˇ ky top point, tufa formed on limestone tablet between August 2002 and October 2003;
(f ) calcified colony of coccoid cyanobacteria, L ´ˇ ky E site, tufa on limestone tablet exposed between August 2002 and
October 2003; a, b, d - lyophilized samples, SEM images, c, f - thin sections.

structure. Conversely, loosely arranged filaments
need considerably higher amount of calcite to be
cemented completely into a compact sparry layer
(Figs 10e & 20e).
Some sparry crystals do not exhibit preferred
orientation (Fig. 20a, b, f ). They are between 5 -
15 mm across. They lack enfacial junctions and
compromise boundaries as well. They are loosely
cemented and look like detached from their sub-
strate.

decomposition of the algal tissue acting as a nuclea-
tion surface for the crystals. The whole process
probably took place below a living algal or cyano-
bacterial mat, which prevented removal of the

loose crystals. They were later cemented and

become a component of the fibrous texture.

Sparite bushes. The sparite bushes are intimately
connected with Oocardium stratum. They were
present The detachment is easiest after the only at the Z´zriv´ site. Loose sparite