Rock beds containing plant macrofossils of Norian in Alborz region belong to two stratigraphic units of Lalehband and Shahmirzad. The same beds in Kopeh-Dagh area belong to Mian-Kuhi Formation and in Central Iran belong to Qadir submember in Tabas region and Dehroud member in Kerman region. In general, plant diversity and vegetative cover during the Norian stage is less than Rhaetian especially Jurassic (Shemshak group) and the highest plant diversity of Norian in the Alborz basin is related to the phyllum of Pteridospermophytes (seed ferns) and in the Central Iran basin is related to the phyllum of Pteridophyta (ferns) indicating the higher humidity of the mentioned time in Central Iran basin and the drier climate in Alborz basin. The highest diversity of vegetation in Norian sediments throughout Iran belongs to the seed ferns (Pteridospermophyta) and the lowest diversity belongs to Ginkgophytes so that they comprise 32% (one third of the vegetation) and 6. 5% of the total vegetation, respectively. Plant-covered areas throughout Alborz were interconnected during the Norian period and there was no extensive separation between them. The plant macrofossils assemblage in both Alborz and Central Iran basins confirms the relatively humid subtropical to tropical climate for the Norian but less humidity compared to the Rhaetian. Also, the vegetation of Norian in Alborz was less dense and scattered than Central Iran during Norian.

Introduction: The thickness of Bidestan member in Nayband Formation type section has been measured equal to 636.7 meters. It's contact (Norian) with Gelkan member (Lower Norian) has the same slope, and usually is determined by a one meter thick layer of gray Oolitic sandy limestone, with dark gray fresh broken surface.Aim: Nayband Formation usually shows a submarine, and continental facies, in this member which is indicative of Nayband formation sedimentary basin deepening in Norian stage.Material and Method: In systematic studies accomplished on 350 thin sections from Bidestan member.Results: In this paper we obtain 78 Species and Genus of Foraminifera, 27 Species and Genus of Bivalves and 3 Species and Genus of Gastropoda where recognized, and their periodic development in Nayband Formation were exactly determined.Conclusion: This paper considered our findings are compatible with Norian to Upper Norian age for this member.

Basal part of the Shemshak group in Galandrud area, in north Alborz about 16km south of Ruian city (Alam- Deh) was investigated palynologicaly. The studied section attains a thickness of 590 meters and, consists of limestone, shale, sandstone and siltstone beds. A total of 29 samples were selected and treated in the palynological laboratory of the geological survey of Iran. Eighty one palynomorph taxa were encountered. The recorded dinoflagellate species were arranged in four local bioassemblage biozones and a superbiozone (Rhaetogonyaulax).Biozone I; Heibergella asymmertrica, occurs in a thickness of 60 m, suggesting an Early Norian age.Biozone II; Heibergella aculeata, occurs within 50m, representing a Middle Norian age.Biozone III; Hebecysta balmei, which occurs in a thickness of 40 m, indicating the Middle to Late Norian age.Biozone IV; Rhaetogonyaulax rhaetica, occurs in a thickness of 330 m, indicating a Late Norian to Rhaetianage.Statistical studies on the recorded palynomorph assemblages show that lower parts of the section have been deposited in an open marine environment. In Late Norian a regression of the sea caused sediment of the Rhaetian to be deposited in a deltaic environment. The Early Kimmerian and the following orogenic phases have had the least effccted on the sedimentation processes during Late Triassic age in this area and the carbonaceous Elika Formation turned into Shemshak group gradually and without any disruption.

The Nayband Formation was sampled at Chal-Sefid and Zard mountains in central Iran, for palynology and palynostratigraphy in order to take the advantage of dinoflagellate cysts to locate the Triassic and so called Jurassic boundary. The Chal-Sefid section is located about 45 km southwest of Kashan city and Zard Mountain some 70 km northeast of Esfahan. The studied strata attain a thickness of 1750 meters in Chal-Sefid and 1820 meters in Zard Mountain. They consists sandstone and shale beds. Totally 75 samples from Chal-Sefid and 22 samples from Zard Mountain were collected and treated in the Palynology laboratory of the Geological Survey of Iran. The recorded dinoflagellate cyst species were differentiated in four palynozones in Chal-Sefid and two palynozones in Zard Mountain as follows: Chal-Sefid section: Palynozone 1: Rhaetogonyaulax wigginsii, encompasses 160 meters of the section, suggesting an early to middle Norian age. Palynozone 2: Suessia listeri with a thickness of 140 meters, suggesting a middle Norian age. Palynozone 3: Hebecysta balmei encompasses 550 meters of the section, suggesting middle to late Norian age. Palynozone 4: Rhaetogonyaulax rhaetica with a thickneses of 900 meters suggests an early to middle Rhaetian age. Zard Mountain section: Palynozone 1: Hebecysta balmei, encompasses 442 meters of the section, suggesting a middle to late Norian age. Palynozone 2: Raetogonyaulax rhaetica, encompasses 491 meters of the section, suggesting an early to middle Rhaetian age. It is revealed that all the rock units investigated here are of late Triassic age and no evidence of Jurassic ages was identified.

The Shemshak Group is well-exposed in Ramsar coal-bearing region and consists of four formations,Ekrasar, Laleband, Kalariz and Javaherdeh. The Laleband Formation lies conformably and gradationally on top of Ekrasar formation and its upper contact is conformable and sharp under Kalariz formation. It contains scattered plant macrofossils of Norian-Rhaetian age. The studied section contains well-preserved and scattered plant macrofossils belonging to three orders as Equisetales, Filicales and Pinales. Based on the occurrence of Neocalamites sp. cf. N. carcinoides, Dictyophyllum sp. cf. D. exile, Clathropteris meniscoides and Cycadocarpidium erdmani and stratigraphic position of fossil bearing layers, Late Norian –,Early Rhaetian age is suggested for the studied beds.

Two sections in north Alborz mountain were selected and palynologically studied. The first one, Paland section, is located approximately 30 km in the south of Zirab city. This sequence is 200 m thick and consists mainly of limestone and shale beds and assigned to the Upper Triass. This study resulted in the identification of a relatively rich assemblage of palynomorphs. The age of Late Triassic (Late Norian- Rhaetian) is attributed to the formation by. The known Dinoflagellates taxa.The second section, Galandrud section is located about 16 km in the south of Ruian city (Alam - Deh). This section attains a thickness of 590m and consists of limestone, shale, sandstone and siltstone beds. Eighty one palynomorph taxa were encountered form a total of 30 samples from the base of the Shemshak Group which were selected and treated in the palynological laboratory of the geological survey of Iran. The known species were arranged in the following three local bioassemblage zones:Biozone I, Enzonalasporites vigens: occurs in a thickness of 125m, suggesting the Early - Middle Norian age. Biozone II, Vitreisporites pallidus: with 335m thickness represents the Late Norian age. Lastly, Biozone III, Concavisporites kermanense: occurs in a thickness of l30m indicating the Early Rhaetian age. Statistical study of the recorded palynornorphs indicate an open marine environment for the Upper Triassic sedirnents for this area.

The Mashhad ophiolitic and metamorphic complex was intruded by Mashhad granitoids in three different episodes of magmatisms. Dehnow pluton with diorite-granodiorite composition was intruded in earliest stage of magmatism in late Triassic (Norian, 215±4My).This pluton is cut across by the NW-SE trending ductile shear zones which are dominated by an intense ductile deformation. The rocks of the Dehnow pluton along the shear zones are converted into protomylonite, mylonite and ultra-mylonite with steeply dipping mylonitic foliation and gently plunging stretch lineation on it. Kinematic analysis of shear sense indicators such as S-C fabrics, asymmetric folds, asymmetric porphyroclasts, mica fish and domino-type fragmented porphyroclasts reveal that the ductile deformation is related to right lateral reverse slip that may describe by a transpressional deformation regime. the minerals in the mylonitic rocks shows variable microstructures such as patchy to crosshatch undulose extinction, shear fracture, deformation lamellae, subgrains formation, bulging  dynamic recrystalization (BLG) and subgrain rotation recrystalization (SGR) in quartz grains, also subgrain formation , deformation twins, flame-shaped prethities , dynamic recrystalization (BLG) in feldspars , all indicated that the ductile deformation have occured in 300-500oC (upper green schist and lower amphibolites facies conditions). Age and cross cutting relations between various lithological units in the study area revealed that the ductile shear zones were formed during Cimmerian orogeny between Norian to Early Jurassic age.

In order to survey the extensional forces dominated in central Alborz since Late Triassic (Norian) to Middle Jurassic (Early-Bajocian), synsedimentary normal and strike-slip fault systems in Balladeh valley which contains significant distribution of Shemshak Group have been studied. Analysis of σ orientation for 404 fault planes in 35 normal fault systems, show two major extension directions at NNE (020o) and NE (070o) trends during sedimentation of Shemshak Group. Also, the presence of a minor extension direction trending WNW (300o) which is coincident with extension direction of synsedimentary strike-slip fault systems implies the existence of transtentional basins in the Shemshak basin at that time. The southward movement of southern edge of Eurasia (from latitude of 30° to 15o) and its clockwise rotation for some 40o-50o during Triassic-Jurassic periods led to domination of N-S extension in early times of Shemshak Group sedimentation, and as soon as the Eurasian plate rotated, the extension direction was changed into a NE-SW trend. These separated records of paleostress axis trends are also due to the high sedimentation rates and subsidence in Norian-Rhaetian and Toarcian-Aalenian during Shemshak Group sedimentation. The minor extension trending WNW-ESE (278o-307o) is due to σ2/σ3 permutation between N-S σ2 direction of stress tensor and its σ2 axis. Low values of Φ (less than 0.4) generally correspond to situation characterized by σ2/σ3 permutation; therefor it causes multidirectional extension in extensional stress regimes. About 80 percent of sites which show WNW-ESE paleostress extension trend have low Φ values. This issue explains σ2/σ3 permutation of N-S major extension trend. The areas of mentioned stations and also those ones with strike-slip fault systems σ3 directions of which are directed WNW-ESE had high basin crustal anisotropy.

The Nayband Formation was measured and sampled in Parvadeh area, southern Tabas city. In this area, this formation has a thickness of 1410 m, dividing into four members, namely Gelkan, Bidestan, Howz-e-sheikh and Howz-e-khan. A total 573 samples were treated for Palynological analysis, and only 120 samples were productive. A total of 57 miospore taxa and 11 plant macrofossil were encountered. Based on stratigraphic distribution of macrofossil and miospore taxa ten assemblage zones were established throughout the Nayband Formation. The encountered miospore taxa and plant macrofossil suggest Upper Triassic (Norian-Rhaetian) for the Nayband Formation. Rock-Eval data shows the presence of organic matter-rich shales with Type III kerogen. The Nayband Formation in the studied section has experienced high temperature which is confirmed by vitrinite reflectance measurements of 0. 9-1. 2 %VRr. At this thermal maturity stage, organic-rich shales in the formation have generated liquid hydrocarbons as evidenced by the occurrence of solid bitumen in the respective samples.