Zagros Range

Overview

The Zagros Mountains (Persian: رشته كوه زاگرس), (Kurdish: Çîyayên Zagrosê), make up Iran and Iraq's largest mountain range. They have a total length of 1500 km from western Iran, specifically the Kurdistan region on the border with Iraq to the southern parts of the Persian Gulf. The range ends at the Straits of Hormuz. The highest point in the Zagros range is Mt. Dena at 4550m .

Formed by collision of the Eurasian and Arabian tectonic plates, the range extends for hundreds of kilometers. Stresses induced in the Earth's crust by the collision caused extensive folding of the preexisting layered sedimentary rocks. Subsequent erosion removed softer rocks, such as mudstone (rock formed by consolidated mud) and siltstone (a slightly coarser-grained mudstone) while leaving harder rocks, such as limestone (calcium-rich rock consisting of the remains of marine organisms) and dolomite (rocks similar to limestone containing calcium and magnesium). This differential erosion formed the linear ridges of the Zagros Mountains. The depositional environment and tectonic history of the rocks were conducive to the formation and trapping of petroleum, and the Zagros region is an important part of Persian Gulf production.

Salt domes and salt glaciers are a common feature of the Zagros Mountains. Salt domes are an important target for oil exploration, as the impermeable salt frequently traps petroleum beneath other rock layers. Since the northern part of Zagros encompasses much of the historic Kurdish regions of Middle East, it has also been referred to as Kurdish Mountains or Kurdistan Mountains
The Zagros Mountains in southwestern Iran present an impressive landscape of long linear ridges and valleys. Formed by collision of the Eurasian and Arabian tectonic plates, the ridges and valleys extend hundreds of kilometers. Stresses induced in the Earth’s crust by the collision caused extensive folding of the preexisting layered sedimentary rocks. Subsequent erosion removed softer rocks, such as mudstone (rock formed by consolidated mud) and siltstone (a slightly coarser-grained mudstone) while leaving harder rocks, such as limestone (calcium-rich rock consisting of the remains of marine organisms) and dolomite (rocks similar to limestone containing calcium and magnesium). This differential erosion formed the linear ridges of the Zagros Mountains. The depositional environment and tectonic history of the rocks were conducive to the formation and trapping of petroleum, and the Zagros region is an important part of Persian Gulf production.

This astronaut photograph of the southwestern edge of the Zagros mountain belt includes another common feature of the region—a salt dome (Kuh-e-Namak or “mountain of salt” in Farsi). Thick layers of minerals such as halite (common table salt) typically accumulate in closed basins during alternating wet and dry climatic conditions. Over geologic time, these layers of salt are buried under younger layers of rock. The pressure from overlying rock layers causes the lower-density salt to flow upwards, bending the overlying rock layers and creating a dome-like structure. Erosion has spectacularly revealed the uplifted tan and brown rock layers surrounding the white Kuh-e-Namak to the northwest and southeast (center of image). Radial drainage patterns indicate another salt dome is located to the southwest (image left center). If the rising plug of salt (called a salt diapir) breaches the surface, it can become a flowing salt glacier. Salt domes are an important target for oil exploration, as the impermeable salt frequently traps petroleum beneath other rock layers.

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The name Zagros is derived from the Zagarthians/Sagarthians--and Indo-European, Iranic immigrants from Europe who once inhabited the mountains, from the shores of Lake Van to the coasts of Makran. The Zangana and Chigini tribes of the Kurds are the remnants of these ancient Sagarthians. Other explanations deriving the name from Greek Zagreus, meaning stormy, or the name Za-G'R' means 'great mountain' in the Avestan language, are invalid.

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The mountains are divided into many parallel sub-ranges (up to 10, or 250 km wide), and have the same age and orogenesis as the Alps. Iran's main oilfields lie in the western central foothills of the Zagros mountain range. The highest point of the range is Zard Kuh (4548 metres). The southern ranges of the Fars Province have only somewhat lower summits of up to 4000 m. They contain some limestone rocks showing abundant fossils. Special surveyor expeditions sometimes come across fossil snails of 2 kilograms at altitudes of 3000 metres. It is now hard to imagine that these high summits were indeed part of the deep ocean some 50 million years ago. The second highest peak is named Dena

The Kuhrud Mountains form one of the parallel ranges at a distance of approx. 300 km to the east. The area between these two impressive mountain chains is home to a dense human population that lives in the intermediate valleys which are quite high in altitude with a temperate climate. Their rivers, which eventually reach salt lakes, create fertile environments for agriculture and commerce

Links

https://www.summitpost.org/mountain/rock/235231/dena-massif.html

Zagros in history

Signs of early agriculture date back as far as 9000 BCE to the foothils of the Zagros Mountains, in cities later named Anshan and Susa . Jarmo is one archaelogical site in this area. Shanidar , where the skeletal remains of Neanderthals have been found, is another.

Some of the earliest evidence of wine production has been discovered in the Zagros Mountains; both the settlements of Hajji Firuz and Godin Tepe have given evidence of wine storage dating between 3500 and 5400 BC.[2]

During early ancient times, the Zagros was the home of "barbarian" peoples such as the Kassites, Guti, and Mitanni, who periodically invaded the Sumerian and/or Akkadian cities of Mesopotamia. The mountains form a geographic barrier between the flatlands of Mesopotamia (Iraq) and the Iranian plateauThe Zagros Mountains in the southwest, representing the contact between the Arabian craton, and the Kopeh Dagh Mountains in the northeast, representing the contact with the stable Turonian (Eurasian) craton, are two active fold-thrust belts forming the borders of Iran. As you may have guessed from the title, this project focuses on the southwestern Zagros Mountains. The Zagros belt is about 200 km wide in the northwest, and widens to roughly 350-400 km in the southeast, and is nearly 1500 km long. The highest peaks are about 4.5 km, though average elevation is closer to 2.5-3 km. The deformation intensifies toward the interior of Iran, manifested by anticlines of larger amplitudes (Snyder and Barazangi, 1986). Rates of convergence between the Arabian and Eurasian plates are estimated at 47-51 mm/yr. Deformation in the way of folding and reverse faulting principally accommodates this movement (Berberian, 1981).

The Zagros are often touted as being in a Pre-Himalayan collisional stage, the idea being that both mountain ranges are the result of continent-continent collision. If this is the case, we should be able to look to the Zagros to help us answer questions about the earlier development of the Himalaya, and simalarly we can look to the Himalayas to predict the future development of the Zagros.

Link

Text and Photo = Wikipedia

Images

View Zagros Range Image Gallery - 21 Images