Oman is situated on the southeast coast of the Arabian Peninsula. It is a country in southwest Asia. The sultanate of Oman “borders the United Arabs Emirates in the northwest, Saudi Arabia in the west, and Yemen in southwest. The coast is formed by Arabian sea in the south and east, and the gulf of Oman in the northeast.” (From: http://www.omansultanate.com/).
Oman has a unique geology because 90 million years ago obduction happened in north Oman (see fig.#). Obduction happens when the oceanic crust goes up into continental crust and this is unusual movement. The usual movement is when the oceanic crust goes under the continental crust which is subduction.
Most of central of Oman is covered with a wide desert plain, and with mountain ranges over north (Jebel Akhdar) and southeast. The peninsula of Musandam has a strategic position on the strain of Hormuz, is segregated from the rest of the Sultanate of Oman by the United Arabs Emirates and is therefore exclave. In Oman there is another exclave which is known as Wadi-e-Madhah. It belongs to Musandam governorate. It is situated in the middle of the way between the Musandam peninsula and the rest of Oman.
Geology of Oman through the time from Precambrian to the current era.
Pre-Cambrian: During this age, which go back to the beginning of geological time, when the life began on earth, there were bacteria and algae. At the end of the pre-Cambrian, worms, jellyfish and spongs appeared.
Cambrian: In this age, animals with shells or other hard covering start to appear in the seas as, trilobites developed into a large and different group of crawlers and swimmers that controlled the sea for next 100 million years.
Ordovician: In this period, many new animals appeared for the first time. For example, coral, sea urchins and colonial animals known as bryozoan. A new fish also appeared, but it didn’t has any fins or jaws in its first appearance.
Silurian: In this period, different groups of fishes swim in the sea. Also, the first appearance of plants were in this period. The land was controlled at first by colonies of seedless plants, then by scorpion. In fresh water, there were small fish and large scorpion.
Devonian: In his age, sharks appeared with other kinds of fish. Insects and the first amphibians, evolving from scaly fish, crawled out on the land. On land, simple plants were appeared, followed by mosses, horsetails and ferns.
Carboniferous: Giant ferns grew in steamy swamps, and large amphibians hunted giant dragonflies. Much of the coal used as fuel around the world began to form at this time. The amphibians because a large and important group, they eventually gave rise to the reptiles, for the first time on land, animals with back-bones (vertebrates) appeared.
Permian: the reptiles of the carboniferous period developed into different groups and start to control the land. Large amphibians were rare. In the sea, trilobites were extinct, while squid-like cephalopods and other molluscs continued to grow.
Triassic: In this period, reptiles start to appear. Many kinds evolved, like dinosaurs. Some of reptiles lived in the land and others lived in air. Also mammals appeared in that period. Mosses and ferns start to extinct whereas, conifer trees appeared.
Jurassic: The dinosaurs, which was the biggest animal in that time, ruled the land. There were many types of dinosaurs. For example, marine dinosaurs which hunted the oceans and flying dinosaurs which swooped through the air. The oldest bird and the famous one called (Archaeopteryx).
Cretaceous: For the first time flowering plants appeared on land. While the dinosaurs (squid- like cephalopods) which were found in the sea. At the end of cretaceous, ammonites, belemnites and dinosaurs suddenly died.
Tertiary: Mammals quickly appeared like, whales, bats, lemur, deer, horses, rhinos and elephants. Also in this period huge birds can’t fly, reptiles and invertebrates appeared. Shallow was covering Oman in tertiary times. There were found a deposition of limestone in warm seas. All these evidence of marine conditions were found near Rusayl.
Rocks and fossils in Oman:
There are many types of rocks and fossils in Oman. First let’s start with fossils.” Fossils are the remains and traces of life from the past. Normally fossils originate from the hard parts of animals and plants, such as shells, teeth, bones and wood, which are buried in sediments. The soft part decay quickly and are not preserved.” (From natural history museum). Some example of fossils in Oman, stromatolites. Stromatolites are the oldest fossils known in Oman. They are dome-shaped or pillar-like structures built by primitive, single-celled algae that secret calcite and trap sedimentary particles. Another example, flint. Flints are caused by the growth of the mineral silica within limestone. Sometimes a fossil may be found within the flint nodule but usually there is none. Flint can be used to make arrow-heads and tools.
Most of rocks in Oman are limestone. There are also other types of rocks in Oman like geodes. They are found in the south of Oman. Geodes are formed when crystals of the mineral gypsum grow as a solid sphere in soft sediments. Waters have later removed the gypsum and quartz crystals begin to grow into the hollow sphere.
The geological features in Oman illustrates a history of 800 million years ago. During this period, we get a lot of information about the tectonic events and climatic condition. Also we know more about continental and oceanic crust. In addition, knowing about geology helps everyone to know about Moho which separate between the crust and the mantle.
Bawshar sand dunes:
What is dunes?
A mound of sand crested by the wind, especially found near oceans and lakes or in deserts.
Formation of dunes:
Sand dunes form in several areas. However, for sand dunes to form there are some conditions have to be met. The first important requirement is a source of dry sand, the second requirement is a means to arrange and transfer the sand. (For example, wind or water), and the third requirement is a ground district on which to deposit the sand. In fact, the wind erosion is the initial responsible of the formation of dunes. Dunes form when the wind fluxes through and around an impediment, resulting the deposition of sand grains which gather together and build up a deposit of sand. “Dunes migrate by sand moving up and over the gentle windward slope by saltation and accumulating and sliding down the lead ward side.” (From the handouts).