Petrology and geochemistry of annually laminated stalagmites from an Alpine cave (Obir, Austria): seasonal cave physiology - Tufas and Speleothems: Unravelling the Microbial and Physical Controls - page 297

Fig. 2. Petrology of stalagmite sample Obi84. (a) image of ion microprobe section with calendar ages of annual
laminae superimposed. In the central part of the speleothem the laminae are approximately tabular and horizontal, but
curve and merge on the lateral flanks. (b) Photomicrograph under crossed polars of thin section made from synchrotron
sample (viewed to a similar sample depth as in photograph (a) illustrating quasi-columnar crystal morphology
approximately normal to growth surface. 'S' indicates example of crystal with undulose (specifically, radiaxial)
extinction (see text). Small red rectangle indicates area of electron backscatter diffraction (EBSD) map. (c) EBSD map
of a grid of 931 by 701 points at 1 mm resolution. The map has been false-coloured to highlight the relative
crystallographic orientations of the calcite across the map. The colour range blue to red indicates a 08 -158 deviation in
orientation with respect to the crystallographic orientation of the calcite at the reference point indicated by the red
cross near the centre. The large crystals to the right of the map are grey and have no colour as the orientation of these
crystals differ by more than 158 from that of the reference point (see also Fig. 1d). Scattered grey pixels in the upper and
left areas of the map were the results of systematic mis-indexing of the calcite diffraction patterns while others (mostly
in the central areas of the map) represent locations where the quality of the diffraction pattern was too poor to give a
solution for the crystallographic orientation of the calcite and were assigned a zero solution. The map shows that the
large crystals are divided into crystallites around 10 mm wide. (d) Upper-hemisphere stereographic projections of the
poles to potential indicated crystal forms for the crystals illustrated in the EBSD map in Figure 1c. The XY plane of the
projections is that of the surface of the sample section. The colours shown correspond to those in Figure 1c. The
reference point (red cross) shown in Figure 1c was chosen as having a crystallographic orientation close to the centre of
the brightly coloured clusters. The grey clusters indicate the orientation of the large (grey) crystals to the right of
Figure 1c. The f0001g diagram also corresponds to the zone axis and orientation of the z crystallographic axis which can
be seen to be sub-vertical in the diagram, corresponding to sub-perpendicular to the elongation and growth directions of
crystals at the top of the stalagmite, that is, the crystals are optically length-slow. The f10 - 11g diagram displays a pole to
one face approximately in the equatorial plane: this is thought to be equivalent to the flat face seen on crystallite tops in
Figure 3b. Colour references in the caption correspond to the online colour version.

Figure 2d. The crystallites show a range in orien-
tation by up to around 158 within each crystal, but
adjacent crystallites are often mismatched by only
1-28. The pole to f0001g in Figure 1d (left), which

also corresponds to the ,0001. zone axis cluster
near the centre of the projection, indicating that the
z crystallographic axes are near-vertical with
respect to the surface of the sample section shown