Miocene miospores in the Upper Red Formation, Zanjan, northwestern IranAbstractThe Upper Red Formation has extensive outcrops in the southern and western parts of the Zanjan province, northwestern Iran. Here, we studied a sequence of lowermost part of this formation near Mehr-Abad village, northwestern Zanjan. Lithostratigraphy, sedimentology and ichnology of the URF have been studied in recent decades but palynology of this formation has not been investigated. This article is a preliminary report of miospores. The palynofloras comprise thirty species including three algae spores (in three genera), seven fern species (in seven genera), various type of gymnosperm (thirteen species designated to nine genera), and angiosperm pollen species (seven species designated to six genera); for example, Botryococcus sp., Closteritetrapidites magnus, and Diagonalites diagonalis of algal spores; Echinatisporis muelleri, Magnastriatites sp. cf. M. grandiosus, and Polyapodiaceoisporites potoniei of fern; Cathayapollis scheuringii, Cedripites sp., Ephedripites tertiarius, Pinuspollenites lobatus, P. minimus, Cupressacites spp., Tsugapollenites spp. of gymnosperm, and Acidanthera brevicollis, Calliandra spp., Fagopsis longifolia, Monoporopollenites sp., and Retitricolporites sp. of angiosperm evidenced herein. Moreover, botanical affinity of miospores considered. Therefore, Botryococcaceae/ Dictyosphaeriaceae, Closteriaceae, Zygnemataceae (algae); Marattiaceae, Pteridaceae, Polypodiaceae (fern); Cupressaceae, Ephedraceae, Pinaceae (gymnosperm), and Fagaceae, Fabaceae, Iridaceae, and Poaceae (angiosperm) identified.Keywords: Miocene, Upper Red Formation, spore, pollen, Zanjan, NW Iran.

This paper deals with the effect of lamination on the failure strength and fracture pattern of Upper Red Formation sandstones in southwest of Qom, Iran using Brazilian and point load tests. For this purpose, six blocks were taken from a part of this formation and have been drilled at different directions of lamination planes such as 0°, 30°, 45°, 60° and 90°.Although, the selected sandstones are seems similar but, the carried out test results and their failure patternsare different. The tensile strength, point load index and failure patterns in different inclination angles were determined for this group of sandstones. Also, the transitional angle of failurehas been determined for Brazilian and point load tests. The test results clearly indicated that failure strength and fractures pattern of laminated sandstones is a function of lamination inclination angle. Also, the results show there is a good correlation between strength and failure pattern of this group of sandstones under Brazilian and point load test conditions.

This study attempts to investigate the origin of red pigments, time of reddening, and processes responsible for red colouring of the Upper Miocene age Upper Red Formation, the most important clastic unit in central Iran. Mineralogical composition and textural properties of the studied sequences show that the Upper Red Formation sequences were not red when deposited, although some parts of red pigments were derived from the source region. This study clearly shows that both detrital and diagenetic pigments contributed in red colouring of the formation but diagenetic forms were more significant.

Numerous Proboscidean footprints have been discovered in the outcrop (135 m) of lower rock unit of the Upper Red Formation (Middle-Late Miocene) in the north Avaj (Qazvin province), central Iran. These footprints are preserved as circular concave epi-relief in the upper bedding planes with smooth or levee rims or with sediment accumulation in the front of the footprints. Five digit imprints present in some of the footprints. The frequency of footprints is considerable the most of the upper surface of layers which was resulted by movement of proboscis herds. Ichnotaxonomically these footprints identified as Proboscipedaen igmatica. The footprints are classified as two sizes as small (15 cm) and large (25 cm) categories, and based on the geometric relationships, the height of shoulder was estimated as 140-170 cm for adult and 76-106 cm immature individuals. According to reports of Miocene Proboscidean body fossils from Iran, and based on the distributions of the Proboscidean in this time, it seems that the Choerolophodon (Gomphotheriidae) is candidate as track-maker of the Avaj footprints. Among the Proboscidean footprints, there are crocodile and fish swimming imprints which were left in the shallow pools.

Upper Red Formation (Miocene) in Sharabian area (South-West of Sarab) comprises about 1600 meters of detrital and evaporatic facies. Accurate field and laboratory studies upon detrital layer of Upper Red Formation lead to break up four groups of facies, that showing alluvial fan, braided and Meandring Rivers and playa condition. Lower part of formation the demonstrates braided and meandring rivers settings. Narrow thickness in midle part of formation showing alluvial fan depositional environment and upper part of formation is incorporation of meandring rivers depositional environmental and playa conditions.

Numerous vertebrates footprints have been found in the Miocene Upper Red Formation sandstone and siltstone layers in the 3 km west of Mushampa village, west Zanjan province. Most of the footprints were preserved as hypichnia, include bird's webbed footprints Culcitapeda tridens and Culcitapeda isp.; tetradactyle footprint Antarctichnus isp. and digitigrad footprints Avipeda isp. A and Avipeda isp.B. Carnivora footprints are Bestiopeda isp. and Credontipes isp. ichnogenuses. It seems that sedimentary environment was a shallow-water pan of a marginal marine environment, and footprints formed on the exposed sediments.

The combination of petrography and geochemistry data of sedimentary rocks can reveal the nature of source regions, the tectonic setting of sedimentary basins, and paleo-climate conditions. With this goal, the Oligocene Upper Red Formation clastic rocks with a thickness of 220 m outcrop in the southern region of Hasan Abad- Tehran were studied. Using thin sections and point counting of minerals and components and geochemical analysis of major and minor elements, the sequence were carefully investigated. This section is composed of repeating sequence of bright color Marl and Litharenite sandstone. Grain counts and geochemical evidence proved that most of these sandstones are volcanic-arenite. Maturity and sedimentary cycle index of these rock is equal to 1.722, which indicates the formation of deposits in the first cycle of sedimentation in active tectonic setting with relatively low maturity. Also, based on the results of the interpretation of geochemical data, felsic to intermediate source rock with a composition similar to continental crust is suggested for sandstone.

The Upper Red Formation (URF) was chosen to review due to tectonic and stratigraphic complication of the Avaj area and the extent of the URF in this area. The URF was investigated through sedimentological and tectonic aspects. The URF deposits in the Avaj area were divided into two members (M1 and M2). Based on sedimentological investigations (mineralogy, lithology and sedimentary structures), the URF two members are different in lithology (e. g., quartz, feldspars, volcanic rock fragments and carbonate cementation differences in sandstones and clay mineral composition difference in mudrocks). The paleocurrent direction changed from SE to NW in the lower member to NNW to SSE in the upper member. Field observations revealed an unconformity between these two members. The Shurab salt dome deformed the lower member but deformation did not reach the upper member. According to the mentioned evidence, two previously known members of the URF (M1 or the Avaj Red Beds and M2 or the Bi-Ab conglomerate) did not belong to the same formation, and the upper member (Bi-Ab conglomerate) should be considered as a new lithostratigraphic unit. Based on tectonic evidence, the late Alpine movements (<20 Ma. ) triggered the inversion of Avaj Fault and deposition of the URF. The Atikan orogeny (5 Ma. ) caused the deformation of the URF and the unconformity at the base of the Bi-Ab conglomerate. The Atikan movements also reactivated the Hassan Abad Fault, causing the creation of the Khar Rud shortcut. The uplift of the Khar Rud block provided the Bi-Ab conglomerate sediment supply. The Bi-Ab conglomerate might be deposited during Pliocene and deformed by the Pasadanian movements (2-1. 8 Ma. ).

The Mahneshan Basin is one of the syntectonic Neogene sub-basins of the Central Iran. The basin is filled by about 4 km of the Miocene Upper Red Formation deposits, showing a combination of halokinetic and growth strata patterns. To assess the provenance evolution of sediments in north of the Mahneshan basin named the Hesar section, we conducted remote sensing mapping, field survey, as well as petrographical and modal analyses of sandstones. Our results reveal that the sandstones are fine to medium-grained sedarenites (Q46F10Rf44) and mainly derived from fine-grained siliciclastics, metamorphic, carbonate, chert and andesitic volcanic rocks, which were exposed in an orogenic tectonic setting (Qm34F10Lt56 and Qt49F10L41). The combination of provenance data and northeastward paleocurrent direction, reflect that the sediments mainly supplied from basement rocks of the Takab Complex and Qom Formation in southwest of Mahneshan Basin. The unchanged provenance of sediments along the studied succession, indicate that regional shortening and uplift of parent rocks has begun before deposition of the Upper Red Formation (Miocene) and continued during deposition of these sediments. This is in agreement with previous age assumption for exhumation of Takab Complex during Oligocene time.

Kuh-e-Sorkh is located in Southwestern Semnan, Iran. The bedrock of this region is formed from upper red formation and includes fine and evaporative grain. Due to water erosion, various erosion shapes have been developed. One of the most interesting and rarest erosions is tunneling erosion or piping. Among these, pseudokarsts have a simple structure with V-shaped holes in various dimensions. In addition, there is an underground drainage network that is connected to the surface drainage network. Although the appearance of these structures is simple, their formation mechanism seems to be complex. Factors influencing their formation are as follows. Bed rock: lithology, aggregation (compounds) diagnosis, concentration and salts, clay types and mechanical attributes of the bed rock as follows. Soil: texture, structure, amount of salts, leaching, pH, electrical conductivity (EC), sodium absorption ratio (SAR) and exchangeable sodium percentage (ESP). Physiography: slope, aspect, elevation and hydraulic gradient slope. Climate: precipitation, temperature, precipitation and climatic changes. Biotic: human impact, livestock trampling and vegetation destruction. The effects of the above factors are not identical in formation of pseudokarsts, rather the two most effective ones are soil texture and chemical properties such as pH, EC, ESP, SAR that were subject of this investigation. In addition, field observations were taken into account in studying pseudokarst formation. The results showed that development of pseudokarsts is primarily affected by soil texture where percentage of silt particle is greater than clay and sand particles and pseudokarsts are more expanded. Thus, salts and chemical formation were considered secondary to pseudokarst formation. Further, there was a relationship between EC and SAR. Field samples revealed higher SAR content and variable amounts of EC. This indicates the important role of SAR in pseudokarst expansion without considering EC.