The features of tafoni caves (Pampa de Achala, República Argentina)

THE FEATURES OF THE TAFONI CAVES IN PAMPA DE ACHALA (Sierra Grande de Córdoba, República Argentina) ELENA DE UÑA ÁLVAREZ

In the north-western region of Argentina (Sierras Pampeanas), the high granite plains of the Sierra Grande de Córdoba (Cerro Champaquí 2.790 m a.s.l.) Pampa de Achala.

“Los Riojanos” (LR) granite area in the “Pampa de Achala” latitude

31º 28´ 40´´ S – 31º 29´ 15´´ S

longitude 64º 55´ 00´´ W - 64º 55´ 55´´ W

Location of tafoni forms in LR 1.686 m - 1.819 m a.s.l.

LR1

LR1

Sampling • Only just the forms which hostess block remains in situ (not moved or slipt) • Limited to the greatest cavities • Total observations from the field = 25

Data • Field-based information about the cavities axis measures (in m) • Shape aproximation to several geometric bodies • Statistical processing stick to robustness (non-parametric stats)

The tafone cave usually can be represented by a quarter-ellipsoid or hemi-ellipsoid geometric body

Specially is noteworthy the geometry of an empty sphere (lateral section) In this case, the cavity surround the external volume of the hostess block under one rock umbrella

Another cavities can be represented by the geometry of one mid-sphere And a small number of them can be represented by a mid-cylinder or rectangular geometric body

The tafoni measures and shape properties can be related to their evolutive path

Los Riojanos results (n = 25) PLOT by levels of Z axis (in m)

E V O L U T I V

G R E A T E S T

E F S T A G E

O R M S

The geometry and size variations may be determined by the same variations from the host blocks, linked with some endogenous deformation events. The variable Z from LR greatest tafoni (ZTF) is associated with the Z measure of their host blocks (ALTB)

CASE

ALTB

ZTF

LR23 LR9 LR22 LR8 LR1

2,00 2,15 4,00 5,00 8,00

1,35 1,40 2,20 3,20 4,00

The median and the quartiles of the tafoni measures are the goodness indicators of their features and development stage

STATS-STAGE Minimum Lower Quartile Median Upper Quartile Maximum

Y (m) 1,00 2,89 4,30 7,60 24,00

X (m) 0,80 1,55 2,90 3,50 5,10

Z (m) 0,70 1,05 1,25 1,75 4,00