The Rock.
This part of the earth is located along the area where the
Arabian Plate meets the Eurasian Plate. The Musandam Peninsula
is
an outcrop that used to be on the sea floor. This
“historical” sea floor is known as the Semail
ophiolite
that was laid down in the Permian to Middle Cretaceous period.
The
movement of these plates is experienced still to this day,
with
earthquakes being fairly common on the Iranian side of the
Straits
of Hormuz and along the Zagros mountains.
The structure of the Oman Ophiolite is fairly complex with
a
range of rocks and minerals present. The slab of Late
Cretaceous
oceanic crust contains: cherts, pillow lavas, sheeted dykes,
gabbros and cumulate peridotite-gabbros; the upper mantle:
depleted
harzburgite-dunite, that was emplaced, largely intact onto
the
continental margin of Arabia. The layer below the ophiolite
(the
“sole” or contact with the mantle) consists of:
garnet
and clinopyroxene amphibolites showing partial melt textures,
epidote amphibolites and a variety of greenschist
meta-sediments
(marbles, quartzites). Although varied, to most of us without
training – or closer inspection, the different rocks will
not
be easily differentiated or identified. This is also not a
requirement of this cache.
The Semail Ophiolite provides one of the best exposure in
the
world to study oceanic lithosphere. The Semail ophiolite is
visible
in a belt 600 km long and 150 km wide and between 5 and 10 km
thick. It can be divided into five structural elements:
The Arabian Platform – initially attached to
Africa, the Arabian Peninsula is moving slow towards Central
Asia
and away from Africa.;
the Huqf-Haushi Uplift;
the Oman Mountains;
the Masirah Ophiolite Uplift
and the Gulf of Oman.
Getting closer to the shore.
This Khor (or inlet or body of water) is surrounded by
looming
mountains that gives it the name on much tourist literature
as
“the fjords of the desert”. The mountains were
pushed
up during the obduction of the Arabian Plate. The
picture
illustrates where the Ophiolites are pushed up exposing the
sea
floor. It is speculated that this rock was deposited on the base
of
the Tethys Ocean (that separated Gondwanaland and Laurasia).
Collision of plates leading to Ophiolite formation
NOTE TO CACHERS - this cache can only be accessed
by
boat. These are easily hired from either Khasab – or for
the
more adventurous (and taking more time) leaving from Dibba.
Alternatively if you have your own kayak or small craft, you
can
access the cache with this.
Diversity around the Khawr.
In order to substantiate your visit and be able to claim
this
Earthcache, a number of questions need to be answered and
submitted
to the cache developer, via e-mail.
You must also post a photograph on the site with your log
of
your GPSr near GZ.
1. Describe what you observed from the spot at or near
Telegraph
Island. Describe any evidence of layering or folding in
particular.
2. Describe any particular geological features that you
found
interesting in the area. I leave this to your discretion.
3. Explain how you understand how the sea floor became a
large
mountain.
4. How did you get to this spot? What mode of transport?
NOTE: You may log your visit prior to approval, but e-mail
submissions that do not meet the above criteria will be
deleted.
