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Mila Formation in Central Alborz

The Mila Formation is one of the Cambrian formations in Alborz.  The Mila Formation has 5 measurable members in type section (Mila Kuh, Damghan City). This formation overlies conformably the Early Cambrian Lalun Formation and underlies disconformably the Early Devonian red conglomerates. But on the Chalus road in Central Alborz, four members of this formation are visible and measurable.

The first member is a white base quartzite (BQ), which in the past was a member of the lower formation (Lalun), but according to detailed studies, the boundary of this unit with underlying sandstone layers is considered to be discontinuous.

The Second member consist of Dolomite with interbedded of yellow Shale and Marl. Third member is well bedded Limestone with a few shale. Forth member is course grained glauconitic limestone. Fifth member consist of Siltstone, Sandstone, Glauconitic limestone and Marl.

In the Image, Mila formation outcrops in Chaloos road, near Hasanakdar Village. Because of the tectonic forces, the rocky layers are cut, broken, and displaced by faults.

The lower boundary of this formation with the Lalun Formation is para unconformity and indicated with the white quartzite layers. The upper boundary of this formation in this area is determined by the Hassanakdar fault and the outcrop of lava in the Geirud Formation. All the thickness of the Mila Formation (without quartzite) in the Karaj valley is 395 meters (Lorenz, 1964). In this region without the quartzite member, only three members of the Mila Formation have been identified.

In the photo, the formations of Lalun (La), Mila (Mi), Ruteh (Ru), Jeyrud (Je), Elika (El) and quartzite member of the Mila Formation (BQ) are seen.

Keywords: Iran , Central Alborz , Geology , Geotourism , formation , Mila , ruteh , jeyrud , elika , chaloos road , limestone , sandstone , siltstone , dolomite , shale , marl , zamingasht

Star Valley

The Star Valley, which is called “Estareh Kafteh” in local dialect, is one of the most important erosional phenomena in Iran. this valley is located in south east of Qeshm Island in Persian Gulf. In this valley there is variety of geomorphological phenomena which shaped several interconnected branches of small valleys.

Besides the mechanical erosion of water which is the main factor of shaping this area, there are many other factors such as different types of rocks with different resistance, the intercalation of gypsum and the different regional tectonic activities.

The walls of the valley are formed by two types of layer: the thick and soft layer in bottom and the thin and hard layer on top. As the top layer has calcareous cement, is more resistance than the loose lower one; so it acts as the protector. Therefor where ever the top layer was destroyed or has some joints, erosion effects quickly and it causes the small valley’s forming.

Referring to the mentioned causes; the layers of this valley are so brittle, so even the weight of just one person can be dangerous and causes collapsing. Although the upper layer may seems to be strong, but the lower layers may has been destroyed due to erosion.

The Mishan formation is the main formation of the Star Valley. In Qeshm Island this formation includes the alternation of marl and silty marl in olive green to grey color with some lenses of intra formation conglomerate which intercalates with sandstones.

The age of formation in star valley back to Middle or late Miocene (5 to 10 million years ago), but the phenomena relates to several thousand years ago.

In sedimentary sequences of Mishan formation, there is variety of structures such as thin – middle – thick and massive layering, fossiliferous limestone and sandstone in the channel shapes, graded bedding, plane lamination, lens form lamination and other structures can be found.

From the structural geology point of view, the layers in the Star Valley have low dip or they are horizontal. Due to tectonic activites in Mishan formation, the systematic joints have been created in this area. The gravity force and weathering and erosional phenomena are the main reason of joints opening.

In local ancient’s belief, this valley has been formed by impact a meteorite and rising up of stones and soils and freezing there. On the other hand, they believed this valley was the resort goblins and the voice of howling the wind was because of their movements.

Keywords: Erosion , Geo site , Geology , Geotourism , Iran , Limestone , Marl , Mishan formation , Persian gulf , Qeshm Island , Sandstone , Star Valley

Sarvak formation in Zagros

The Sarvak Formation (Albian to Cenomanian), forming part of the Bangestan Group, comprises a thick succession of carbonate rocks in the Zagros Basin of Southern Iran. The type section of the Sarvak Formation is situated in the Teng-e-Sarvak area, Khuzestan, and is overlain by the Kazhdumi Formation and underlain by the Ilam Formation. The boundary between Sarvak and Ilam Formation is a disconformity that determined in some area by breccia or conglomerates.

The Sarvak Formation consists of alternation of limestone, shale and marl. Limestone layers of this formation are full of microorganisms known as orbitolina. and Because of more than 60% calcium carbonate in their composition, they have a lot of talent for karstification.

The above image shows outcrop of Sarvak formation at the core of the Chenareh anticline near Pa-alam in Khuzestan province. alternation of well-bedded limestone and thin layers of shale and marl is seen in the picture. Due to the presence of thin layers of marl and shale in its sedimentary sequence, The Sarvak Formation has been eroded very soon and the land is hilly shape.

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In the picture above, outcrop of Sarvak Formation is seen in the core of Chenareh anticline in bright color.

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Geological map of Chenareh anticline (Part of the geological map Balarood)