Factors controlling growth of modern tufa: results of a field experiment - Tufas and Speleothems: Unravelling the Microbial and Physical Controls - page 151

Fig. 5. Proceeding growth of tufa on pair of tablets exposed at the Karw´ w cascade point throughout the whole
experiment, in each photo the limestone tablet (upper one) is much encrusted than copper tablet, (a) in March 2003; (b)
in June 2003; (c) in October 2003 after 204, 286 and 399 days of exposition respectively, upper arrow - limestone tablet
lower arrow copper tablet, in c pencil tip shows a lower left corner of copper tablet.

organic matter. Deeper on, they are preserved as
moulds encrusted with calcite. According to fila-
ment size and shape, three morphotypes can be
distinguished.
The first morphotype comprises non-branching
filaments with diameters ranging from 20 to
30 mm and the lengths exceeding even a few centi-
metres (Fig. 10a, b). They are preserved as smooth-
walled moulds without traces of segmentation. The
moulds are encrusted predominantly with sparry
calcite crystals which commonly constitute the
continuous cover on the filament. The smallest
crystals, growing directly on the filaments are
1-5 mm in size. They exhibit platy or isometric
habit (Fig. 10c, d). The moulds are not filled with
calcite. The filaments exhibit different orientation
from random to parallel to each other (Fig. 10e).
They are parallel or subparallel to the basement,
hardly ever erected and never oriented at an angle
of 908 to the basement. They were formed mostly
in the area of vigorous flow, though are less
common on waterfall or cascade faces, where
water freely falls down. The tufa from the L ´ˇ ky
and Karw ´ w sites abounds in such filaments
which also occur, but subordinately, at the H ´ j site.
The size and shape of these filaments suggest
their affinity to Vaucheria, an alga belonging to
Xanthophyceae, which commonly lives in modern
tufa-depositing environments. It was reported, for
instance, from Germany (Wallner 1934a, b; Irion
&M ¨ller 1968; Flajs 1977), Belgium (Symoens
1957; Janssen et al. 1999), Poland (Szulc 1983,

1984), France (Freytet & Plet 1991), Italy
(Anzalone et al. 2007) and Croatia (Golubi ´ et al.
2008). Vaucheria colonizes the fast flowing sec-
tion of the stream where its filaments are arranged
paralel to water flow (Wallner 1934b; Freytet &
Verrecchia 1998). Living Vaucheria is abundant at
the Karw ´ w and L ´ˇ ky sites, and has been also
found at the H ´ j site (T. Mrozi ´ ska, pers. comm.,
2003). Vaucheria at Karw ´ w was also noted by
Szulc (1984).
Freytet & Verecchia (1998) noted that Vau-
cheria are encrusted exclusively with platy crystals.
The Vaucheria filaments from the L ´ˇ ky site are
initially covered with small isometric or platy crys-
tals. These crystals develop into rhombohedra
oriented perpendicular to the filament which acts
as the base for nucleation (Fig. 10a, f; cf. Golubi ´
et al. 2008). The finding of Vaucheria filaments,
completely overgrown with calcite crystals even in
the youngest part of tufa samples deposited within
a three-month period, proves that overgrowing is a
very quick process. At the L ´ˇ ky site it probably
lasts only a few days. Some filaments seem to be
collapsed or broken, and in thin sections they

display semicircular cross-sections.
The second type of filaments are of smaller
diameter - 5 - 8 mm - while their lengths attain
several dozen micrometres. They are preserved as
moulds encrusted with crystals of micritic or sparitic
size (Fig. 11a - c). The organic filament serves as
nucleation sites for the crystals (Fig. 11d - f ). They
can also be entombed in sparry calcite crystals;