O-146 The formations of the grutas del palmito, (Bustamante, Nuevo

Hellenic Speleological Society
O-146
The formations of the grutas del palmito, (Bustamante, Nuevo León, Mexico), Preliminary Results
Paolo Forti, Univ. Bologna, Via Zamboni 67, I-40127 Bologna, Italy
Arrigo A. Cigna, UIS-SSI, Fraz. Tuffo, I-14023 COCCONATO (Asti), Italy
Abstract
The formations found in the “Grutas del Palmito” confirm the existence of different climatic situations occurred in the cave. Among the more
common formations this cave is characterised by a number of rimstone
pools, sometimes very large. In some of them big cave pearls (up to more
than 10 cm diameter) are found. Physical chemical analysis of the material
of the rimstone pools show a very fast deposition rate with the presence
of thermal water.
Key words: Palmito, formations, rimstone, cave pearls speleogenesis.
Introduction
The cave environment can be divided into three parts (Fig. 1 and 2):
1First part, already used as a show cave: Salon de Baile (about 150
m)
2Middle part: from Paso de la Muerte to Grandes Desniveles (about
160 m)
3Last part: Salon de los Gigantes, Catedral, Cueva de Nieve, etc.
The first part is peculiar for many rimstone pools, often rather large,
ment on the bottom of a shallow sea. Other sediments were deposited
on the limestone, until about 60 million years ago when geologic forces
pushed up the rocks to form the Sierra Madre Oriental. Successively such
rocks have slowly been eroded to expose the limestone and to cut the
Bustamante Valley over 500 m deep.
Physical features of the cave
This cave probably developed under hydrothermal conditions since
there is evidence of gypsum in some formations. On the other hand, thermal waters have been observed in the area (Ojo del agua, with a temperature above 26°C, source S. Lorenzo with a temperature around 25° C, with
the outside temperature around 13°C).
Important cycles of deposition and corrosion may be observed in the
cave; concerning both the formations and the rock. In addition, close to
the entrance, many stalactites have an evident bent toward the entrance
itself, due to an air flow entering the cave when such stalactites developed.
For this reason the cave had another entrance at a lower altitude, which
later was closed by the growth of formation or collapse.
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Fig. 1 - Location of the «Grutas del Palmito»
Fig. 2 - Map of “Grutas de Bustamante” (“Grutas del Palmito”)
in addition to stalactites, stalagmites and column. In some rimstone pools
there are big cave pearls (up to 10 cm in diameter). In the second part,
close to the western side (on the right when entering) there is a room of
some ten of square metres with very nice helictites rather well preserved.
In the last part many columns are found, some of them fallen down in
the past and, successively, other stalagmites grew on them.
From the point of view of formations, this cave has an exceptional
abundance of cave powder (Hill & Forti 1997), which is the main constituent of the rimstone pools and is also found in some rocks, being probably
the remnants of ancient pools. For this reason some small samples were
taken to study their composition and possibly define their origin. In this
note, after the geological and climatological characteristics of the cave
have been summarised, the samples of cave powder are described with
reference to their morphology and mineralogy, and eventually a genetical
interpretation is reported.
Fig. 3 - Sampling points
Geology
Grutas del Palmito (also called Grutas de Bustamante) formed in the
Cupido Limestone, which was deposited 115 million years ago as sedi-
Since the present entrance was the “warm entrance” of the karst system,
the airflow entered during the Summer time. Therefore this fact agrees
with the season of the faster development of the stalactites which occurred
during the Summer, a rainy time in this region. Presently very weak air
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418
Fig. 4 - SEM image of a characteristic calcite aggregate from sample 1
Fig. 5 - SEM image of a “gigantic” calcite crystal from sample 3
Fig. 6- SEM image of a vertex of a crystal characterized by holes induced by insufficient
crystallisation energy
Fig. 7 - SEM image of an aggregate of calcite crystals of sample 3 partially covered by
a thin fractured crust
Fig. 8 - SEM image of filaments growing over the crust covering calcite crystals of
sample 3
Fig. 9 - SEM image of a “biogenic nest” in sample 3
flow were detected (below 1 cm/s) at the entrance, sometimes directed
inside and outside the cave. Such a flow may be due either to a “barometric cave” (i.e. the air moves inside or outside according the change of the
atmospheric pressure outside) or to a chimney effect with a lower entrance
is due to small fractures or the porosity itself of the rock. The phenomenon
of the acoustic resonance was excluded because the time interval between
the change of direction (inflow or outflow) of the air was too long with
respect to the intervals (some minutes) due to this phenomenon.
A series of thermometric measurements inside the cave resulted in a
uniform air temperature around 19.5°C all over the cave, sometimes with
local changes around one tenth of Celsius degree. Such uniformity also
21-28 August 2005, Kalamos, Hellas
in the vicinity of the entrance is a proof of a rather stable equilibrium of
the cave from the energy balance point of view. Therefore the presence of
visitors and the lighting system should not alter such equilibrium.
Experimental
Three samples have been collected in the cave (Fig. 3):
1From the remnant of a ridge in the middle of the main flat chamber.
2From the ridge of the rimstone pool in the same chamber, towards
West.
3From a whitish rock towards the “Paso de la Muerte”
Hellenic Speleological Society
Fig. 10 - Cave pearl with a serpentine nucleus (size 13 mm)
Fig. 11- Cave pearl is composed by the coalescence of at least three pearls.
These samples are quite similar and normally consist of small aggregates of euedral crystal of calcite (Fig. 4), even if larger isolated calcite
crystals have been rarely observed (Fig. 5). Under a higher enlargement
it is possible to see that many vertices of the crystals in samples 1 and 2
have a “skeleton” structure (Fig. 6) with many triangular cavities suggesting an extremely fast growth witho ut the possibility of keeping a euedral structure. In sample 3 such structures if not absent are much rarer.In
sample 3, unlike the previous ones, a thin crust is observed. Such a crust,
characterised by dry up fractures, covers many calcite crystals (Fig. 7). In
addition this crust supported biogenic activities as confirmed by filaments
(Fig. 8) and complex structures (Fig. 9) having an evident bacterial origin.
X-ray analysis confirmed that samples 1 and 2 are composed exclusively
by calcite, while in sample 3 also traces of gypsum were found.
In point 4 of Fig. 3 two calcite cave pearls were collected in two different rimstone pools. They are whitish with a botrioydal structure with
diameter around 7 cm. After having been sectioned and polished, one
has a serpentine nucleus (size 13 mm) while the others is composed by
the coalescence of at least three pearls possibly with nuclei smaller than
1 mm. Both pearls’ calcite layers are alternately “thin and compact” and
“thick and porous”, sometimes botrioydal without any sign of successive
solution or erosion.
ferent conditions. In fact, the calcite (also if in small amounts) was solved
and re-deposited as gypsum.
Some biogenic process, as supported by the presence of hyphae and
globules forms this crust, and the consequent deposition of gypsum probably implies that such reactions could have developed within the cycle of
sulphur (Forti, 1989). Thus, the environmental conditions of the evolution
of the cave powder should have developed in an aerial environment with
the powder slightly wet by condensation water and the presence of small
amounts of organic material. Then some micro-organisms could develop
ad produce a small amount of sulphuric acid, which corroded the calcite
and covered it partially with a thin crust having some gypsum inside.
From the analysis of the two cave pearls described above it is possible
to obtain some information on the paleo-environmental and paleo-hydrological evolution of the cave. The existence of very large cave pearls (up
to 15 cm) is due to a very high “prompt” energy inside the rimstone pools.
On the other hand the pearls did not rotate or knocked heavily among
them due to the absence of erosion. Therefore the water flow in the cave
should have had few but important floods to avoid that the pearls could
attach to the floor but not enough strong to develop any evident erosion
The presence of rather large nuclei (Fig. 10) together with very small nuclei (Fig. 11) agrees with the hypothesis of a water flow rate reported
above. In fact, during the few floods some gravel could be transported
by the flowing water into the pools where, however, for rather long time
intervals, small and very small nuclei would prevail on account of the low
energy of the whole system. The coalescence of some pearls into a larger
one is probably due to some local condition, as the shape of the pool, but
its is not possible to describe any more detailed process on the basis of
the present data.
The inside structure of the cave pearls is more interesting: the abundance of porous layers (sometimes quite botrioydal) is due to long intervals of partial or total emersion of the cave pearls with the development
of structures resulting from the evaporation and not the diffusion of CO2.
Instead, the presence of thin and compact layers is due to intervals when
the water supply of the pools was continuous and constant longer than
one year.
Therefore, during the growth of the cave pearls, the hydrology of the
cave was characterised by few floods and long intervals of dryness whe­n
water in the pools evaporated totally. Anyway, periods of more abundant
rainfall (few years or few tens of years each) should have existed resulting in the growth of more compact layers of the cave pearls. Presently
the water flow in the upper part of cave is connected to heavy rains s a
consequence of more dry climate.
Discussion
The experimental results show that the cave powder samples 1 and
2 are quite identical and therefore also their origin should have been the
same. Sample 3, on account of the presence of larger crystals, of gypsum
traces and organic material, and the absence of “skeleton” structures,
implies an evolution different from those of the previous samples. The
purity, size and imperfection of the crystals of samples 1 and 2 support the
hypothesis of a growth by a fast deposition due to a fast release of CO2
in the atmosphere from water with a relative high concentration of CO2,
probably of thermal origin. The precipitation was due to physical chemical processes only, which justifies the purity of the deposited calcite.
The evolution of sample 3 should have been slower and more complex. Larger sizes of the crystals, together with the absence of “skeleton”
structures support the hypothesis of a slow deposition under a low supersaturation. Accordingly the processes of crystal growth (bi-dimensional) were more frequent than the processes of formation of new nuclei
(three-dimensional). Therefore this cave powder was formed probably
for evaporation than for the diffusion of CO2. The presence of a thin crust
with traces of gypsum above many calcite crystals shows that, after the
deposition of calcite, the evolution continued for a short time under dif-
14th International Congress of Speleology
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Conclusion
The first results of the investigations here reported support the hydrothermal origin of the cave, with a good agreement with the cave morphology. The existence of hydrothermal sources in the vicinity confirms this
evidence. The cave itself shows a number of different conditions, which
probably followed one after the other. In fact, successive conditions of
deposition and corrosion can be observed on many formations, particularly in the part of the cave closer to the entrance.
Further researches both on the hydrothermal sources of the region
and cave formations will provide more details on the processes here described.
Acknowledgements
The authors are very grateful to Orion Knox for his support and particularly for having supplied the map of the cave, and to the Corporación
para el desarrollo turístico de Nuevo León which funded the visit to the
cave.
References
Forti P. 1989 - The role of sulfide-sulfate reactions in speleogenesis.
Proc. 10th Int. Spel Congr., Budapest, 1: 71-73
Hill C.A. & Forti P. 1997 - Cave minerals of the world. Natl. Spel.
Soc., Huntsville: 1- 464.
O-147
The hydrodynamic Behaviour of Cretaceous and Oligomiocene karstic aquifers of Boroujerd (West of Iran)
M.Ahmadipour, B.Ebrahimi
Lorestan University, Iran, Isfahan Regional Water Board, IR.Iran
In this study the development of karst in the Cretaceous limestone and
Oligomicene limestone have been compared. Both the karstic aquifers are
situated in the high Zagros zone of Iran.The analyses of the recession
curves of the springs of Zoorabad and Aziz bad whoich originate from the
cretaceous limestone indicte that due to the development of the secondary
fratures the flow regime is of turbulent type. The analyses of the springs
of Sarab-e- Absardeh and Sarab-e-Golumsoz which discharge from the
Oligomiocen limestone due to the low karstic development is of laminar
flow
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O-148
Recent exploration undertaken by S.EL.A.S. club in the “Dersios” sink-hole at Paleochora, Arcadia
N. Mitsakis, S. Zacharias
S.EL.A.S Club
Between the years 2003 and 2005, cavers of SELAS club have been
extending the exploration done by a French team in the 1970’s in the
“Dersios” sinkhole of Arkadia. The sinkhole is at about 750m altitude and
presents technical difficulties as there are many parallel passages ending in
flooded sections. These have been explored by emptying the sumps or by
21-28 August 2005, Kalamos, Hellas
cave-diving. The expeditions of S.EL.A.S. have doubled the depth of the
explored cave and more than tripled its length. The cave presents a perfect
opportunity to test and perfect techniques at relatively small depths which
can then be applied in deeper caves and it is these techniques which will
form the focal point of our presentation.