Stratigraphy and Palaeontology
Manizhe Famarini Bozchalouei; Nasrollah Abbassi; Armin Salsani; Afshin Zohdi
Abstract
Soltanieh Formation comprises seven informal submembers as alternation of dolomites and shales, more than 1110 meters in thickness, was surveyed in the Seyedkandi section, 32 km southwest of Zanjan, northwest Iran. These submembers were subdivided as lower dolomite, lower shale, second dolomite, second ...
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Soltanieh Formation comprises seven informal submembers as alternation of dolomites and shales, more than 1110 meters in thickness, was surveyed in the Seyedkandi section, 32 km southwest of Zanjan, northwest Iran. These submembers were subdivided as lower dolomite, lower shale, second dolomite, second shale, third dolomite, upper shale and upper dolomite, respectively. Based on ichnological data from 109 specimens, 23 ichnogenera and 42 ichnospecies have been recognised. The abundance of trace fossils is very high in the second shale submember, so that 99 specimens were collected from this rock unit. Ichnofossil data from the studied section showsthat the Neoproterozoic-Cambrian boundary is located in the 8 m above the base of second dolomite submember in the studied section, where the first occurrence of Treptichnus pedum was been recorded.
Stratigraphy and Palaeontology
Zahra Hosseini Asgarabadi; Nasrollah Abbassi; Hassan Mohseni; Saeed Khodabakhsh
Abstract
The Pabdeh Formation (Paleocene to Oligocene in age) comprises alternation of marl and limestone with the Purple Shale at the base is well exposed on the flanks of the Kabir-Kuh. Thalassinoides, Rhizocorallium, Planolites, Chondrites, cf. Rosselia, Spirophyton and Zoophycos were found in the limestone ...
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The Pabdeh Formation (Paleocene to Oligocene in age) comprises alternation of marl and limestone with the Purple Shale at the base is well exposed on the flanks of the Kabir-Kuh. Thalassinoides, Rhizocorallium, Planolites, Chondrites, cf. Rosselia, Spirophyton and Zoophycos were found in the limestone beds, among which trace fossils of Zoophycos group (Spirophyton and Zoophycos) are the most abundant. Structural variations of trace fossils of Zoophycos group were utiliized for recognition of five morphotypes including Rhizocorallium-shaped, branched Zoophycos, Spirophyton, short and fan-shaped lobate Zoophycos and long lobate Zoophycos morphotypes. Occurrence of these morphotypes in the studied sections implies an evolutionary trend, i.e. Rhizocorallium-shaped and branched Zoophycos morphotypes are developed in the lower parts of studied sections, whereas Spirophyton morphotype, is arranged in the mid-part of the Pabdeh Formation. Finally, short and fan-shaped lobate and long lobate Zoophycos morphotypes are abundant in the upper part of the formation. Seemingly, these morphotypes variation were adopted with switch of stable and calm water to unstable and relatively high energy environments.
N Abbassi; M Parvanehnezhad Shirazi; M.A Hosseinzadeh
Abstract
Albian–Cenomanian siliciclastic-carbonate sediments of northwest Rayen in south Kerman, southeast Iran (526 m) are classifiable to three informal units. Unit one includes conglomerates, sandstones and siltstones with limestone and marl intercalations. Unit two is composed of Orbitolina bearing ...
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Albian–Cenomanian siliciclastic-carbonate sediments of northwest Rayen in south Kerman, southeast Iran (526 m) are classifiable to three informal units. Unit one includes conglomerates, sandstones and siltstones with limestone and marl intercalations. Unit two is composed of Orbitolina bearing limestones with rudists, belemnoid and ammonite bioclasts. Alternations of pelagic limestones and sandstones formed the third unit. Assemblage of continental to marine trace fossils have been found in the first and third units of the studied section, that include Koilosoma isp., Ophiomorpha isp., Palaeophycus isp., Planolites isp., Skolithos isp., Taenidium isp., and Thalassinoides suevicus. These trace fossils belongs to Scoyenia, Skolithos and Cruziana ichnofacies. Abundant Thalassinoides-Phycodes compound trace fossil, however have been found in the third unit. Box-worked Thalassinoides burrow system ends to multi- branched Phycodes borrows. This compound trace fossil is interpreted as feeding-domicile biogenic structure, so that Thalassinoides domichnium ends to Phycodes excavated feeding burrows. Compound Thalassinoides-Phycodes trace fossil extended in the deeper parts of offshore shelf sediments in the studied section. Based on ichnological data, it seems that Albian–Cenomanian sediments of northwest Rayen deposited in a deepening upward sequence.
