carbonate ramp

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1 - Age, microfacies and sedimentary environments of the Sirenia-bearing deposits of the Qom Formation in Central Iran
Fatemeh Morovati Majid Mirzaie Ataabadi Mehran Arian Afshin Zohdi Mohsen Al-e Ali

10.30495/ijes.2021.681579

Sea cows are exceptional fossil vertebrates recently discovered in the deposits of the Qom Formation. Yet, the Sirenia-bearing limestones are still poorly understood in terms of detail paleoenvironmental and micropaleontological investigations. In order to distinguish t أکثر

Sea cows are exceptional fossil vertebrates recently discovered in the deposits of the Qom Formation. Yet, the Sirenia-bearing limestones are still poorly understood in terms of detail paleoenvironmental and micropaleontological investigations. In order to distinguish the temporal and paleoenvironmental context of the Sirenia (sea cow) bearing deposits of the Qom Formation in central Iran, three stratigraphic sections were studied in Hamedan (Ivak and Shirinsu) and Isfahan (Chahriseh) provinces. A total number of 47 thin sections were studied for micropaleontology, biozonation and carbonate microfacies analysis, as well as sedimentary environment recounstruction. Biostratigraphical investigations suggest that the Sirenia-bearing deposits are Aquitanian/Burdigalian in age, which implies restriction of sea cows remains to the Lower Miocene. We recognized nine microfacies (n=8 correspond to carbonate; n=1 correspond to siliciclastic) in the study areas. They are systematically grouped into two microfacies settings, representing inner and middle ramp environments. This is based on the facies associations and the distribution of skeletal components and rock textures. The Sirenia-bearing limestone consists of peloid/algae bearing wackstone/packstone/floatstone. A carbonate (inner) ramp system under shallow water conditions is interpreted as the habitats of the Sirenian mammals during the Aquitanian/Burdigalian in Central Iran. This paleoenvironmental setting could be utilized for further exploration of Qom Formation deposits for discovering sea cows. تفاصيل المقالة

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2 - Paleoecology of Early to Middle Miocene Deposits (Guri Member) and Sedimentary Environment, SE Zagros Zone, Roydar, Iran
Roya Fanati Rashidi Seyed Hamid Vaziri Keyvan Khaksar Hossein Gholamalian

This research focusses on the facies distribution, paleoenvironment and paleoecology of the foraminifera of the Guri Member in the northern Bandar Abbas Hinterland located in the Roydar area of southern Iran. The Guri Member is 570 meters thick and composed of limestone أکثر

This research focusses on the facies distribution, paleoenvironment and paleoecology of the foraminifera of the Guri Member in the northern Bandar Abbas Hinterland located in the Roydar area of southern Iran. The Guri Member is 570 meters thick and composed of limestone, argillaceous limestone and marl. The distribution of the foraminifera in the study area indicates the existence of three biozones ranging from early to middle Miocene in age. Based on petrographical studies, depositional textures and fauna, eight microfacies were identified. The paleoecology, lithology and environmental interpretations were characterized by an open marine environment with an upward, gradually shallowing trend. Additionally, three distinct depositional settings were identified: tidal flat, inner ramp and middle ramp. Microfacies (MF) 1, representing a distal middle ramp setting, was characterized by the occurrence of hyaline, benthic and planktonic foraminifera. MF2 and MF3 were characterized by the occurrence of Miogypsina, Elphidium and red algae. They represent a deeper low energy in the wave base of a middle ramp setting. MF4 was characterized by an abundance of rotaliids and red algae representing a proximal middle ramp environment. MF5 and MF6 were identified by the occurrence of large and small porcelaneous benthic foraminifera representing a shallow-water inner ramp setting. MF7 and MF8 were characterized by the occurrence of gastropods and bivalves in a shallow-water setting of tidal flats influenced by both wave and tidal processes. Palaeolatitudinal reconstructions based on skeletal grains suggest that the Guri Member existed in tropical waters within a carbonate ramp. تفاصيل المقالة

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3 - Ichnotaxonomic analysis and depositional controls on the carbonate ramp ichnological characteristics of the Deh-Sufiyan Formation (Middle Cambrian), Central Alborz, Iran
Aram Bayet-Goll Reza Moussavi-Harami Asadollah Mahboubi

The trace fossil assemblages from the Unit 2 of Deh-Sufiyan Formation are described for the first time from The Central Alborz Range of northern Iran, improving the record of the assemblages in the Cambrian of the Middle East. Twenty-one ichnogenera have been identiﬁed أکثر

The trace fossil assemblages from the Unit 2 of Deh-Sufiyan Formation are described for the first time from The Central Alborz Range of northern Iran, improving the record of the assemblages in the Cambrian of the Middle East. Twenty-one ichnogenera have been identiﬁed in the Deh-Sufiyan Formation, namely Arenicolites, Bergaueria, Chondrites, Circulichnus, Cruziana, Diplichnites, Didymaulichnus, Diplocraterion, Halopoa, Helminthopsis, Gordia, Gyrophyllites, Lockeia, Monomorphichnus, Palaeophycus, Phycosiphon, Planolites, Rosselia, Rusophycus, Skolithos, and Treptichnus. Characteristics of the facies, lateral and vertical relations between these facies, associational types of the facies and the depositional profile of the shelf transect examined show deposition on a wave-dominated carbonate ramp. Integration of ichnologic data with sedimentologic information supports a firm interpretation of the depositional systems and their evolution. Ethological grouping of the trace fossils resulted from the physico-chemical depositional constraints which defines the proximal-distal ichnofacies gradient pattern of the wave-dominated successions of the Deh-Sufiyan ramp. Considering the obvious deepening of the shallow marine depositional systems of wave-dominated parts of the carbonate ramp, the succession of archetypal ichnofacies can display a bathymetric trend from deeper to shallower parts, and from lower-to-higher hydrodynamic conditions, from the bottom to the top of the Unit 2 of the Deh-Sufiyan Formation. The identification and interpretation of the archetypal ichnofacies are employed to further refine the sedimentary interpretations of parameters such as wave energy, substrate properties, nature of available food supply, salinity, dissolved oxygen content, and variability in sedimentation rates. تفاصيل المقالة

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4 - ریز رخساره ها و محیط رسوبی سازند آسماری میدان نفتی رگ سفید در جنوب غرب خوزستان
نبی اله بیداروند نادر کهنسال قدیم وند داوود جهانی

سازند آسماری به سن الیگومیوسن مهم ترین سنگ مخزن میادین نفتی جنوب غرب ایران است.میدان نفتی رگ سفید نیز یکی از میادین نفتی است که در فرو افتادگی دزفول قرار دارد.با وجود مطالعات متعدد،هنوز اطلاعات جامعی از ریز رخساره های رسوبی و شرایط حاکم بر محیط ته نشست سازند آسماری می أکثر

سازند آسماری به سن الیگومیوسن مهم ترین سنگ مخزن میادین نفتی جنوب غرب ایران است.میدان نفتی رگ سفید نیز یکی از میادین نفتی است که در فرو افتادگی دزفول قرار دارد.با وجود مطالعات متعدد،هنوز اطلاعات جامعی از ریز رخساره های رسوبی و شرایط حاکم بر محیط ته نشست سازند آسماری میدان نفتی رگ سفید در دسترس نمی باشد.بنابراین بر اساس مطالعات پتروگرافی مقاطع نازک میکروسکوپی تهیه شده از مغزه هاو خرده های حفاری (2138 مقطع میکروسکوپی در 7 چاه)و مقایسه میکروفاسیس های استاندارد رمپ کربناته فلوگل(2004)و کمربند رخساره ای باکستون و پدلی(1989)،13 میکروفاسیس کربناته و 2 میکروفاسیس غیر کربناته در سازند آسماری میدان نفتی رگ سفید شناسایی گردید.این میکروفاسیس ها ،در 5 گروه رخساره ای(زیر محیط رسوبی)قرار دارند که شامل زیر محیط دریای باز(o)،زیر محیط سد یا بار (گروه B)،زیر محیط لاگون(گروهL)،زیر محیط پهنه های بین جزر و مدی (گروهI) و زیر محیط پهنه های بالای جزر و مدی (گروهS) می باشند.این زیر محیط ها به محیط رسوبی رمپ کربناته نسبت داده می شوند. تفاصيل المقالة

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5 - Investigation of microfacies and sedimentary environments of Qom Formation in the south of Saveh
Somayeh Zare Mir reza Mosavi Mohssen Al-Ali

Qom Formation with Oligo-Miocene age is the most important known hydrocarbon formation in Central Iran. The deposits of this formation in Band-Amir section in the northwest of Saveh have been studied in order to study stratigraphy, facies analysis and interpretation of أکثر

Qom Formation with Oligo-Miocene age is the most important known hydrocarbon formation in Central Iran. The deposits of this formation in Band-Amir section in the northwest of Saveh have been studied in order to study stratigraphy, facies analysis and interpretation of sedimentary environments. The study area is located in the structural-sedimentary zone of Central Iran. The facies changes of the Qom Formation are so great that gypsum and gypsum-bearing marls are deposited when the sea level goes down and limestone and marl are left when the sea level rises. Thus, in many areas, the Qom Formation can be considered as a periodicity of marl and limestone along with gypsum and gypsum marl layers. This formation is located with a discontinuity on the lower red formation and also in a slope below the upper red formation. Due to the sedimentary environment of Qom Formation, the sequences of sediments in this formation have a significant diversity in terms of lithology and are of great importance in terms of reservoir rock, source rock and rock cover. The section of Qom Formation in the northwest of Saveh has a thickness of 198 meters. Extensive and detailed microscopic studies in Band-Amir section have led to the identification of various facies in the form of three facies groups related to the marine environments of the lagoon, dam and open sea. Wetland facies are made of rocks with Paxtonian and Waxtonian texture. Reef facies are of the coral bandstone type and have formed dam deposits. Offshore facies have the characteristics of turbidite facies and basin deposits. Absence of tidal facies and abundance of facies due to reef debris and turbidite deposits are the characteristics of Qom Formation in the study area. Investigation of lateral and vertical changes of facies shows that the deposits of Qom Formation in the studied section are deposited in a carbonate platform of marginal shelf type. تفاصيل المقالة

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