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IMAWARÌ YEUTA: A NEW GIANT CAVE SYSTEM IN THE QUARTZ
SANDSTONES OF THE AUYAN TEPUI, BOLIVAR STATE, VENEZUELA
Francesco Sauro
1,2
, Freddy Vergara
1,3
, Antonio De Vivo
1
, Jo De Waele
1,2
1
Associazione di Esplorazioni Geografiche la Venta, Via Priamo Tron 35/F, 31030, Treviso
2
Department of Biological, Geological and Environmental Sciences, Bologna University, Via Zamboni 67, 40126
Bologna, cescosauro@gmail.com
3
Teraphosa Exploring Team, Puerto Ordaz, Venezuela
In February 2013 a new huge cave system in quartz-sandstones has been discovered in the eastern sector of the Auyan
Tepui, Venezuela by an Italian-Venezuelan team (La Venta Esplorazioni Geografiche and Teraphosa Exploring Team). In
twelve days of exploration over 15 km of passages were surveyed and other 4 km were explored. The system has nine
entrances and hosts three rivers giving rise to three resurgences. The cave passages belong to two levels, an active one in
which the rivers flow with a general and gradual WNW trend, and a inactive level located from 4 to 20 metres higher with
a N-S direction. The active levels are lithologically controlled whith typical pillars, potholes and wide and rounded bedrock
channels with very scarce sediment fill. The inactive level instead hosts large quantities of secondary minerals, mainly
sulphates-phosphates, and very nice and rare opal and silica speleothems. Flowing, drip and standing waters have been
analysed in situ for their Si content and many morphological observations have been carried out in order to try and
understand the speleogenesis of such large quartzite caves. Further geological, mineralogical, geomicrobiological and
biological studies are required in this exceptionally interesting quartzite cave.
1. Introduction
About twenty years ago cavers and karst scientists believed
that speleogenesis of caves in the quartz-sandstones of the
tepui mountains (Bolivar State, Venezuela) was related to
exceptional conditions and only of local importance. In the
80s and 90s the exploration of deep and wide shafts called
“simas” was explained as the result of arenisation processes
along open fractures close to the high cliffs surrounding the
plateaus. In these decades the researches didn’t investigate
the inner sectors of the plateus believed to be less promising
for the discovery of caves.
Since 2000, instead, several horizontal cave systems have
been explored and obviously this required to rediscuss the
speleogenesis of quartzite caves (Aubrecht et al. 2011;
Aubrecht et al. 2013; Sauro et al. 2013). After the
exploration of kilometre long caves in the Roraima and
Chimantha massifs (Galán et al. 2004; Sauro 2009;
Brewer Carìas and Audy 2011), in April 2013 a new giant
cave, named Imawarì Yeuta (the Cave where the Gods
live in Pemon Kamarakoto indian language) was
discovered by an Italian-Venezuelan expedition on the
Auyan Tepui in the Canaima National Park. This
exploration suggests that well developed and extensive
underground drainage systems probably occur below the
surface of most of the tepuis in the Gran Sabana area.
Speleological investigations in the quartz-sandstone
mountains of Venezuela and Brazil seems to be only at
the beginning.
This article shows the main results of the expedition
“Auyan Tepui 2013” and the scientific researches planned
for the future.
2. Geographical and geological settings
The Auyan Tepui is one of the largest table mountains of
the Gran Sabana area (700 km
2
, Fig. 1), well known for the
presence of the Angel Falls, considered the highest waterfall
in the world (975 m).
The Gran Sabana is a vaste geographical region located in
northern South America, between Venezuela and Brazil,
crossed by several tributaries of Rio Caroní, which in turn
flows into the Orinoco River. The Auyan Tepui has the
shape of a large table mountain delimited by vertical to
overhanging walls, often more than 1,000 m high. In plan
view it looks like a triangle pointing to the south. In the
inner part the Canyon del Diablo separates the north-
western sector from the north-eastern one, while the
southern part is a continuous plateau reaching its highest
elevation at 2,450 m asl.
Figure 1. The Auyan Tepuy from a Landsate image. The bounding
box represent the North-Eastern sector of the tepui.
Exploration and Cave Techniques – oral 2013 ICS Proceedings
142
From a geological point of view the Gran Sabana is part of
the Guyana Shield. The igneous and ultra-metamorphic
rocks in the northern portion of the shield (Imataca-Bolivar
Province, after González de Juana et al. 1980) have an age
of 3.5 Ga. The silico-clastic rocks (Roraima Group) belong
to the continental-to-pericontinental environment of the
Roraima-Canaima Province (Reid 1974). The age of this
arenaceous group can be inferred only on the basis of the
absolute dating of the granitic basement (2.3–1.8 Ga) and
of the basaltic dykes and sills that cross the upper formation
of the Roraima Group (1.4–1.8 Ga) (Briceño and Schubert
1990; Santos et al. 2003). The Roraima Group was also
intruded by Mesozoic diabases (Hawkes 1966; Teggin et al.
1985). These form thin NE-trending dykes with ages around
200 Ma.
A slight metamorphism, with quartz-pyrophyllite
paragenesis in the more pelitic beds, is the result of the
lithostatic load of almost 3-km-thick sediments now eroded
(Urbani et al. 1977).
3. Brief history of speleological explorations in
the Auyan Tepui
The presence of caves in the Auyan Tepui is reported
already during one of the first ascensions of the mountain,
the expedition of Felix Cardona Puig and the italian
geologist Alfonso Vinci in December of 1946 (Vinci, 1957).
The cave explored and described by Vinci was never found
again (Merlak, 2010).
The first speleological expedition, with helicopter support,
was realized in 1983 by the Sociedad Venezolana de
Espeleología, with the main aim to explore the Sima Aonda
(Fig. 1), previously known thanks to aerial surveys in the
NW sector of the massif. With its 362 m of depth this
collapse was considered the world deepest quartzite cave
until 1993, even if it consists of an elongated depression
and not a true shaft.
Most of the expeditions carried out in the years after were
basically concentrated in this area where the SVE explored
several other deep “simas”, such as the Sima Auyantepuy
Norte and the Sima Aonda Este 2.
In 1992 an Italian expedition organized by four caving clubs
(CAI SEM Milano, Castellanza, Laveno and Cividale del
Friuli) works on the upper Aonda platform and explores
several caves summing up to 1,700 m of development. The
same year La Venta carries out a first aerial recognition in
the Aonda area in order to organize a future expedition. The
year after a big expedition organized by La Venta works in
three different areas of the same western sector: in Camp
Aonda, the team descends Sima Aonda and explores the
active horizontal system at its bottom (Ali Primera Cave)
and other deep shafts of the platform; in Camp 1, slightly
NE, Sima Churun (Sima Auyantepuy Norte 2) is explored,
and in Camp 2, moved further W, Sima Auyantepuy
Noroeste is discovered, becoming the deepest and longest
quartzite cave in the world at that time (3 km, -370).
In 1996 La Venta organizes another expedition in the Aonda
area, exploring several other simas and connecting Sima del
Bloque to Ali Primera, realizing a cave system 352 m deep
and about 2 km long. In 2010 a short prospection to the
south-western plateau allowed to find and explore the
Cueva Guacamaya (1.1 km), the first horizontal cave found
in the Auyan Tepui, presenting peculiar morphologies
similar to those described in the cave systems of the
Chimantha massif.
Before the expedition of April 2013 a total of about 10 km
of cave passages were explored on Auyan Tepui, but
exclusively in the western part of the massif. The southern
and eastern sectors were completely unknown from a
speleological point of view.
4. The expedition Auyan Tepui 2013
The joint Italian-Venezuelan expedition on Auyan Tepui
took place in March 2013. The expedition was organized
by La Venta Esplorazioni Geografiche together with the
Teraphosa Exploring Team from Puerto Ordaz city. Ten
cavers (7 from Italy and 3 from Venezuela) and two park
rangers from InParques took part to the expedition. The
main aim was to explore the southern and eastern sector of
the mountain, with several unknown entrances located
during previous flights by the helicopter pilot Raul Arias.
The expedition was based in Kavak and a helicopter
supported the installation of the exploration camps on the
plateau. A total of 12 days of exploration activity was
carried out on the mountain. A first group reached an
entrance which opens on the eastern wall of the mountain,
suspended nearly a thousand metres above the surrounding
plain. Unfortunately the impressive opening revealed only
a short gallery about sixty meters length. The same day
another group descended a big collapse, named Sima del
Viento (Fig. 2), apparently close to the bottom. After several
hours of research, finally a narrow passage in between big
boulders led to an impressive active gallery. In the days
after a new camp was installed on the border of the collapse,
allowing a continuous work of exploration, survey,
documentation and scientific researches. After only four
days about 5 km were surveyed, following two main rivers
(Fig. 3). The exploration led quickly to two further
entrances, named Mundo Perdido and Grieta de Los
Guacharos. In the meantime the structure of the cave
suggested the presence of another river to the north-west,
in direction of a giant collapse doline. The supposed river
was finally reached from inside the system through a
labyrinthic network of fossil galleries. An underground
Figure 2. The large collapse of Sima del Viento represent the main
entrance of the Imawarì Yeuta Cave. Photo by F. Sauro.
Exploration and Cave Techniques – oral 2013 ICS Proceedings
143
camp of three days permitted to survey about 10.5 km of
new galleries, with huge rooms (the biggest 270 metres long
and 150 metres wide), complex labyrinths and other three
new entrances. Finally the total surveyed length reaches
15,450 metres, thanks to the use of the Polish CaveSniper
instrument (www.caveexplorer.eu). About other 4 kilometres
were explored but not surveyed because of lack of time.
Imawarì Yeuta represents one of the world’s longest
quartzite caves explored until now, consisting in a unique
cave not divided by valleys, collapses or “grietas”. The
structure of the cave is quite complex but the main
hydrological routes draining the plateau are already well
clear (Fig. 4). Only the network of no more active branches
needs to be better explored and documented.
The expedition recovered all the wastes produced and also
all the faeces from the cave and the surface of the tepui to
avoid microbial contamination. The exploration was carried
out using always the same trail to limit our impact on the
vegetation going to the cave and on the fragile cave floor,
in particular in the fossil branches.
5. The cave Imawarì Yeuta
The new cave consists of three hydrologically independent
collectors (Fig. 5), two of which coming from the big
sinkhole of Sima del Viento, while the other one derives
from the catchment area of a large collapse doline to the
north, about five hundred metres wide, and of a nearby
smaller sinkhole. Here a stream falls into the cave with a
waterfall about 90 metres high. During our explorations,
carried out during a particularly dry period, the first two
streams had a minimum discharge of about 20 l/s, while the
main river reaches a minimum of 100 l/s. From the signs
left by water on the walls it is clear that this last river can
probably reach several cubic metres per second during
floods. The direction of drainage is in general from ESE to
WNW following the dip of the sandstone beds. A labyrinth
network of inactive galleries, developed along an evident
bed, interconnects the different rivers. This “open” bed can
reach impressive width (more than 300 metres in some
sectors) creating huge environments where the ceiling is
supported only by random pillars. This situation causes
large collapse zones with chaos of fallen boulders. In some
cases the fossil galleries show palaeo-phreatic rounded
morphologies and are in general almost perpendicular to the
actual vadose drainage.
One of the most impressive peculiarities of the cave is the
presence of widespread crystallizations of gypsum, opal,
and other secondary minerals (probably alunite, sanjuanite
and rossiantonite). The gypsum occurs in form of acicular
crystals, flower-like forms, crusts and desert roses covering
thousands of square metres of the cave floor. Also deposits
of iron hydroxides are present, in form of stalagmites up to
5 metres high, flowstones, rimstone dams, and coralloids.
Anemolites, helictites and stalactites and other speleothems
of opal and amorphous silica are present (Figs 6–7).
These formations are extremely fragile and the exploration-
documentation of the cave must be carried out with double
flagged trails in order to avoid unnecessary damages.
6. Researches and scientific interests
One of the main objectives of the 2013 expedition to Auyan
Tepui was scientific research, especially concerning
speleogenesis on quartzite caves, in the framework of a
PhD thesis by one of the authors (FS). InParques granted
us the autorisation to carry out chemical analyses on
waters, and to make geomorphological observations at the
surface and inside the discovered caves. Water samples
have been taken in underground streams, of drip waters, in
still-standing pools and lakes, and of surface waters. The
very low contents of Si and SiO
2
in the sampled waters
required quick in situ measurements (UNESCO-WHO
1978; Mecchia and Piccini, 1999; Piccini and Mecchia,
2009) with an Aquaquant © 114410 Silicon by Merck, able
to analyse in a concentration range
of 0.01–0.25 mg/l, with
an error lower than 20%. Analyses were carried out within
24 hours from sampling. Samples with a higher
concentration of Si were analysed by dilution with distilled
water. Temperature, pH, and electric conductivity (EC)
were measured by a HI 991300 Hannah Instruments ©
field portable instrument.
Figure 3. Gallery along the “Rio de los Venezuelanos”. Photo
V. Crobu.
Figure 4. Preliminary sketch of the cave plan obtained using the
Cave Sniper instrument.
Exploration and Cave Techniques – oral 2013 ICS Proceedings
144
Running waters have a pH ranging between 3.1 and 5.9.
Still standing waters in cave pools and lakes can reach
neutrality and high SiO
2
values 7–8 mg L
-1
. The highest
SiO
2
content was documented for an about one hundred
cubic metres pool of standing water with a value of
8.6 mg/l. This confirms that running waters (streams) are
always undersaturated with respect to Si because of their
fast passage through the system while percolation waters
are generally much higher in content confirming that a
dissolution process in fractures and cave walls is effective.
These results support the arenisation model of
speleogenesis in quartz-sandstone (Martini 2000; Sauro et
al. 2013), even though also processes of hydrolysis and
laterisation are possible where sandstones also contain
silicates as suggested by Aubrecht et al. (2011). For
morphological and speleogenetic studies we measured size
and bearings of over 100 pillars in the cave, together with
fractures and bedding planes in order to check the theory of
“pillar flow” proposed by Aubrecht et al. (2011). The results
of these studies will be presented soon.
Further researches are planned for the near future also
regarding the secondary minerals deposits present in the cave.
7. Conclusions
Imawarì Yeuta represents one of the largest cave systems in
quartz sandstone in the world. The discovery of this cave
demonstrates that speleogenesis is widespread in the tepuis
of the Gran Sabana region suggesting that many other cave
systems are waiting to be discovered and documented.
The scientific interest of these caves is very high, ranging
from the processes of weathering that lead to the cave
formation, to the exceptional secondary minerals,
speleothems, cave fauna and geomicrobiological
interactions. In particular this last topic will certainly need
more attention in the future in order to better understand all
the processes interacting in the weathering and secondary
mineral deposition processes. For this reason La Venta is
going to organize a new expedition to this cave, hoping to
achieve all the permissions from the Venezuelan Ministery
of Environment for geological, biological and
geomicrobiological sampling, involving Venezuelan cavers
and scientists interested in this project.
The fragility of this cave will require a protocol of
protection similar to those applied in many other caves in
the world (for example Lechuguilla Cave), where the
visits must be carried out only for documentation and
scientific purposes, following restricted trails and
recovering all artificial and human waste in order to
minimize the impact.
Acknowledgements
The following persons took part in the expedition: Virgilio
Abreu, Raul Arias, Alfredo Brunetti, Carla Corongiu,
Vittorio Crobu, Antonio De Vivo, Jo De Waele, Fulvio
Iorio, David Izquierdo, Jesus Lira, Francesco Sauro, Freddy
Vergara, Jesus Vergara, and the helicopter pilot Julio
Testaferro.
Figure 5. Sixty meter wide gallery along the “Collector de
Noroeste”. Photo V. Crobu.
Figure 6. Coralloids of amorphous silica growing on the cave
floor. Photo V. Crobu.
Figure 7. Rounded silica speleothems in the ceiling of the inactive
network. Photo V. Crobu.
Exploration and Cave Techniques – oral 2013 ICS Proceedings
145
The expedition was possible thanks to the permission for
speleological explorations granted by the Director General
Sectorial of InParques Ing. Carlos Cova and by the sponsors
Geotec SPA, Raul Helicopteros and by the following
technical partners, Dolomite, Intermatica, Ferrino,
Amphibious, De Walt, Allemano Metrology, Chelab,
Scurion, GTLine, New Foods, Bialetti, MountainHouse.
A big thanks to Ortensia Berti and to the community of
Kavak, to Felipe Campisi and his Robinson, to Karina
Ratzevicius of Raul Helicopteros, to the Hotel Gran Sabana
and to Elements Adventure for the logistic support.
The following institutions gave their patronage:
Ambassador of the Republic Bolivarian of Venezuela in
Italy Julian Isaias Rodriguez Diaz, Foundation Dolomiti
Unesco, Italian Speleological Society, Central Commission
for Speleology of CAI, CONI Veneto, Italian Institute of
Speleology.
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