Leaving Son La town to the south-east, route 69 brings you to the Nam
Mua river. The area on the eastern side of this road, between Ban Mat and
Ban Cop Men, turned out to be uninteresting from speleological point of
view; the caves, located in the base of low karstic towers, are small and
fossil, most of them being choked with mud almost to the top. A few kilometres
to the south, in the Ban Key-Puon area, close to the karst boundary, we
were showed an interesting cave that drains the water to the valley of
Ban Cup. Because we investigated this area at the end of our stay, no more
were found. However, it seems to be interesting to go back and check the other side-branches of the Nam Mua river.
MS04 Ban Puon
At the end of the valley, close to the sinkhole of the river, 10m above
the bottom, the entrance is a small crack. The moistness of the draught
is so high that glasses become fogged whilst approaching the entrance.
According to different villagers there was a search for gold in the cave
many years ago (we indeed found many traces that much energy was used to
make the cave accessible and to exploit it). Some children said that they
used the cave as a passage to the nearby valley of Ban Cup. After an 8m
pitch, in which stood a rotten bamboo ladder, one arrives in a fossil gallery.
A little climb leads into a muddy chamber, in which a 4m pitch drops into
water which emerges out of the nearby sump. The water becomes deeper; one
has to swim about 15m to arrive in a beautiful calcited chamber, where
we found an old wooden sieve, a small table with rice-bowls and joss-sticks.
A climb over boulders brings you back to the shallow water. The rift widens
and gets very high (one cannot see the ceiling). Here and there the river
is dammed with wattle-work. Some bamboo piers made us think that a bridge
was once built through the wet parts of the cave to keep the gold-diggers
out of the water. After passing a dry chamber with huge boulders on the
floor, one arrives in a section where the water is again deep and stagnant.
Here we found an old knife. The river leads to a lake (10m x 10m) where
a narrow passage gives access to another little chamber, which is filled
with bamboo. These are probably the remains of a platform, on which a ladder
could bring you through a chimney into the higher level of the cave. A
little duck gives access to another little chamber, which is choked with
mud. The way on probably lies beyond the chimney, but we were unable to
climb it. We also explored the emergence in Ban Cup, where the water is
captured by a concrete basin. The access to the cave lies 10m above it.
A 20m long horizontal part is followed by a pitch which was not descended.