Biostratigraphy,sequence stratigraphy,and paleoecology of the Lower–Middle Miocene of Northern Bandar Abbas,Southeast Zagros basin in south of Iran

The Guri Member is a limestone interval at the base of the calcareous marls of the Mishan Formation. It is the youngest hydrocarbon reservoir of the southeast part of the Zagros sedimentary basin. This Member overlaid siliciclastic rocks of Razak Formation and is overlain by green and gray marls of the Mishan Formation. In order to consider the paleoecology and paleoenvironments of the Lower–Middle Miocene (Guri Member), we have studied biostratigraphy and sequence stratigraphy of the Guri Member based on foraminifer and microfacies in two stratigraphic sections including Dorahi–Homag and Chahestan. A total of 33 genera and 56 species of benthic and planktonic foraminifera were identified in two studied stratigraphic sections. Benthic and planktonic foraminifera demonstrate Aquitanian to Langhian age (Early–Middle Miocene) for this Member at the study area. Studied interval has deposited in four facies association including supratidal, lagoon, coral reef, and open sea on a carbonate ramp. Carbonate rocks of the Guri Member have precipitated in two and three depositional sequences at Chahestan and Dorahi–Homag sections, respectively. Sedimentation of marine carbonates of the Guri Member on siliciclastic deposits reflects a major transgression of sea level at Lower to Middle Miocene that led to creating a new sea in the Zagros basin at that age. Increasing siliciclastic influx along with a sea level fall finally caused burying of the carbonate ramp. Except for the beginning of sedimentation of carbonate at the base of both stratigraphic sections (depositional sequence 1), most of the system tracts are not matched to global sea level curve that reflect local effects of the basin. Distribution of foraminifera suggests precipitation in tropical to subtropical in mesotrophic to oligotrophic and eutrophic to oligotrophic conditions. Based on large benthic foraminifera (porcelaneous large benthic foraminifera and hyaline larger benthic foraminifera), water temperature average was determined between 25 and 30 °C that was confirmed by analyzing oxygen and carbon stable isotopes. Finally, we have utilized achieved data to reconstruction and modeling of paleoecology, paleoenvironments, and sea level changes in the southeast part of the Zagros basin.     

Biostratigraphy of a Paleocene–Eocene Foreland Basin boundary in southern Tibet

This study of the Paleocene–Eocene boundary within a foreland basin of southern Tibet, which was dominated by a carbonate ramp depositional environment, documents more complex environmental conditions than can be derived from studies of the deep oceanic environment. Extinction rates for larger foraminiferal species in the Zongpu-1 Section apply to up to 46% of the larger foraminiferal taxa. The extinction rate in southern Tibet is similar to rates elsewhere in the world, but it shows that the Paleocene fauna disappeared stepwise through the Late Paleocene, with Eocene taxa appearing abruptly above the boundary. A foraminifera turnover was identified between Members 3 and 4 of the Zongpu Formation—from the Miscellanea–Daviesina assemblage to an Orbitolites–Alveolina assemblage. The Paleocene and Eocene boundary is between the SBZ 4 and SBZ 5, where it is marked by the extinction of Miscellanea miscella and the first appearance of Alveolina ellipsodalis and a large number of Orbitolites. Chemostratigraphically, the δ13C values from both the Zongpu-1 and Zongpu-2 Sections show three negative excursions in the transitional strata, one in Late Paleocene, one at the boundary, and one in the early Eocene. The second negative excursion of δ13C, which is located at the P–E boundary, coincides with larger foraminifera overturn. These faunal changes and the observed δ13C negative excursions provide new evidence on environmental changes across the Paleocene–Eocene boundary in Tibet.     

History of the geological evolution of the Tsil’ma River basin (midle Timan) in the Devonian

The results of bio- and lithostratigraphic studies of the Givetian-Frasnian rocks in the Tsil’ma River basin are reported. They suggest regularities in sedimentation: distinct rhythmicity and similar succession in the structure of formations. We have identified five palynocomplexes that characterize the formations and make it possible to accomplish a confident biostratigraphic subdivision of sections. Their correlation with coeval complexes in the adjacent areas has been accomplished. The results made it possible to unravel specific features of miospore assemblages formed in the continental and coastal-marine facies.     

Plant fossil remains from the Bajocian–Bathonian of Hojedk Formation,Babhutk area,Kerman, Iran

Abundant and well-preserved assemblages of plant macrofossils occur from the Hojedk Formation at Babhutk, Kerman, Iran. This new locality is the first in the Jurassic of Kerman where the plant material is shown preserved. Eight species of seven genera were identified representing five different gymnosperm groups: Nilssonia cf. undulata, Nilssonia cf. orientalis, Elatides sp., Podozamites sp., and Williamsonia asseretoii and two pteridophyt groups: Equisetites laterale and Coniopteris sp. The collected flora suggests subtropical conditions at the time of deposition of the Hojedk Formation. Based on stratigraphical distributions of the encountered macrofossils, Bajocian–Bathonian age is suggested for the lower and middle unit of the Hojedk Formation. These plant fossils help confirm conclusions from recent geological studies that place the Kerman Basin of Iran during the Jurassic.     

Change in carbon flux (1960–2015) of the Red River (Vietnam)

Global riverine carbon concentrations and fluxes have been impacted by climate and human-induced changes for many decades. This paper aims to reconstruct the longterm carbon concentrations and carbon fluxes of the Red River, a system under the coupled pressures of environmental change and human activity. Based on (1) the relationships between particulate and dissolved organic carbon (POC, DOC) or dissolved inorganic carbon (DIC), and suspended sediments (TSS) or river water discharge and on (2) the available detailed historical records of river discharge and TSS concentration, the variations of the Red River carbon concentration and flux were estimated for the period 1960–2015. The results show that total carbon flux of the Red River averaged 2555?±?639 kton C year^?1. DIC fluxes dominated total carbon fluxes, representing 64% of total, reflecting a strong weathering process from carbonate rocks in the upstream basin. Total carbon fluxes significantly decreased from 2816 kton C year^?1 during the 1960s to 1372 kton C year^?1 during the 2010s and showed clear seasonal and spatial variations. Organic carbon flux decreased in both quantity and proportion of the total carbon flux from 40.9% in 1960s to 14.9% in 2010s, reflecting the important impact of dam impoundment. DIC flux was also reduced over this period potentially as a consequence of carbonate precipitation in the irrigated, agricultural land and the reduction of the Red River water discharge toward the sea. These decreases in TSS and carbon fluxes are probably partially responsible for different negatives impacts observed in the coastal zone.     

Late triassic flora of the Partizanskaya River basin (Southern Primor’e)

Flora from the lower Norian deposits of the Upper Triassic, which are exposed in the Partizanskaya River basin, has been studied in detail. A new Imalinovo floral assemblage is distinguished. As is established, its taxonomic composition is represented by abundant cycadophytes and conifers occurring in association with insignificant ferns and czekanowskialeans, rare horsetails, pteridosperms, and ginkgoaleans. The studied floral assemblage is compared with several floras of East Asia: the Mongugai flora of Primor’e, the Tianqiaoling flora of northeastern China, the Yamanoi and Nariwa floras of Japan.     

A controversial natural border: The making of the Spanish-Portuguese boundary along the Minho River (1855–1866)

The paper intends to consider how territorial, political and legal culture dominant within mid-19th century Iberian Peninsula influenced boundary-making state practices, and to what extent a complex understanding of natural border areas -and particularly of river boundaries- emerged during this demarcation process. We draw on recent insights about, on the one hand, the important link between territory, nature and law within territorialization processes and state-making and, on the other, intrinsic problems of modern legal categories and juridical practices concerning river boundaries which are argued to be part of territorial ideologies associated with modern states.Within this framework, the paper initially addresses main practices and discourses about territory in this particular Iberian context, regarding both the enduring relevance of theory of natural boundaries within European history of modern state-making and legal codification of river boundaries delimitation by Spanish and Portuguese law internationalists. The following part of the paper presents main historical problems and territorial border disputes along the Minho River which the 1864 Spanish-Portuguese Boundary Treaty attempted to settle. Discussions and negotiations taking place within the Joint Boundary Commissions in charge of examining, delimiting and demarcating this stretch of the border are analysed as to consider how diverging interest and competing discourses about this fluvial space were displayed and related eventually to the solutions adopted by the Boundary Treaty. In that sense, state-driven boundary-making proved to be an important tool for territorial management of this border space.     

Anoxia in the Domanik basin of the Timan–Pechora region

Analysis of the carbon isotopic composition in aryl carotenoid derivatives, including isorenieratene, in bitumen from domanikoid rocks of the sections cropping out along the Chut River revealed that they contain anomalously heavy carbon, which is determined by the formation of these compounds from green sulfur bacteria of the family Chlorobiaceae. These bacteria use the peculiar process of carbon fixing as HCO₃^? in the reversed tricarboxilic acid cycle. The fact of hydrosulfuric contamination of the photic water layer in the Domanik basin is confirmed by the plurality of data. Anoxity in shelf water of the middle Frasnian Timan–Pechora basin is evident from lithological features such as, for example, lamination of some rocks and mass death of the fauna.     

Some regional indicators of the Tertiary–Quaternary geodynamics in the paleocoastal part of the Bengal basin (India)

Sedimentary processes in the paleocoastal part of the Bengal basin that occured in the Tertiary and Quaternary have been addressed. Three indicators were used: sedimentary bedding forms, microstructure of the sediment, and trace fossils. Various forms of sedimentary structures developed under the influence of dynamic geomorphic processes in the study area in the Quaternary. The microstructure analysis of the sedimentary materials was made by two methods: microphotography and Digital Color Analysis (DCA). The microstructure analysis shows that the geomorphic process remained very dynamic in the Quaternary, influencing the form, thickness, and mineral composition of the sediment strata. The enrichment of the sediments in heavy minerals evidences either oscillating or combined flow sedimentation, while under stable conditions light-mineral deposition took place. The digital data of microfabric study by the DCA method also show that larger particles deposited in the oscillating or high-flow environment and evidence a greater amount of heavy minerals like ferruginous materials. Trace fossils found in the sediments of this area also strongly support the concept that the environment remained dynamic during the Tertiary and Quaternary. The Late Tertiary deposition shows that, during these periods, the sediments were transported from tide-dominated marine coast with low flow energy, which is typical of hot and humid conditions. From Late Tertiary to Early Quaternary, the macrotidal coast became mesotidal (wave-dominated). The second phase is the Middle Pleistocene, when the environment was stable, favoring the continuous deposition of finer particles under low- to medium-flow energy conditions. The third phase, the Recent, is marked by the shoreline shift and modification of the environment. In the Early–Middle Holocene, the shoreline started to shift, which modified the geomorphic conditions of this place from coastal to estuarine and, finally, inland fluvial.     

Sr isotope composition in belemnites from the Jurassic–Cretaceous boundary section (Maurynya River,Western Siberia)

The belemnite Sr isotope characteristics obtained over an interval from the Upper Volgian Regional Substage to the lower part of the Ryazanian Regional Stage in the section on the Maurynya River (Western Siberia) fills a gap in the ⁸⁷Sr/⁸⁶Sr ocean water variation curve over the Jurassic–Cretaceous boundary. The increase in the ⁸⁷Sr/⁸⁶Sr values from 0.707172 to 0.707242 revealed in the section coincides with a general rise in this ratio in the Late Jurassic–Early Cretaceous ocean.     

Middle Triassic pteridosperms (Pinophyta) of the Timan–Pechora basin

The collection of fossil plants sampled by geologists from VNIGRI at the end of the 20th century from Triassic continental sections drilled by many wells and cropping out in several natural localities and stored at the Museum of Petroleum Geology and Paleontology of the same institute was critically revised. The use of the epidermal method for the study of plant remains with consideration of recent publications dedicated to continental sections of Central Europe made it possible to substantially broaden the taxonomic composition of the Triassic flora and first specify the composition of its pteridosperm representatives. Unlike the Triassic floras of Western Europe, the pteridosperms the Pechora region appeared to be relatively diverse. They number 37 species of 11 genera, which are confined to the upper part of the Triassic sequence: Anguran and Naryan-Mar formations and their analogs. The Middle Triassic, mainly, Ladinian, age of these formations is reliably substantiated both by paleontological (vertebrate and palynological) data and by results of the comparative analysis of the Anguran–Naryan-Mar taphofloras and coeval European type floras dated back to the Anisian–Ladinian by marine faunal remains. The stratigraphic significance of pteridospermous plant remains becomes undoubted for continental sections of the Timan–Pechora basin, while the genera Scytophyllum, Kalantarium, and Kirjamkenia may be considered with respect to their diversity and abundance as representing orthostratigraphic taxa.     

The Bajocian–Bathonian plant fossil from the Hojedk formation,Lenjan section,Kerman, Iran

The Jurassic successions represent a wide distribution in North of the Kerman province. These successions include Ab-Haji, Badamu, and Hojedk formations. The Hojedk Formation contains the plant fossils. The Lenjan section is one of the suitable areas for paleontological studies on the Hojedk Formation. The study section is mostly composed of green sandstone and shale with several interbedded coal veins with different thicknesses. The thickness of the Hojedk Formation is about 200 m in the Lenjan section. In this study, seven genera and 13 species of macro plant fossils were identified and described, including Nilssonia undulata, Nilssonia bozorga, Nilssonia berriesi, Nilssonia sp., Klukia cf. exilis, Klukia exilis, Cladophlebis antarctica, Coniopteris lobata, Coniopteris murrayana, Elatocladus confertus, Podozamites sp., Equisetites sp., and Coniopteris sp. The Bajocian–Bathonian can be attributed to the Lenjan section based on the recognized flora.     

The uranium content in Dictyonema shale of the Kaibolovo–Gostilitsy Area in the Baltic basin (Leningrad Region)

This paper reports the data on the uranium content in Dictyonema shale and phosphate rock in the Kaibolovo–Gostilitsy Area of the Baltic Basin (Leningrad Region). Specific features of the uranium ore in the studied area and stratigraphic rock sequence of the Early Ordovician Pakerort horizon are considered. A high uranium concentration in the Dictyonema shale layer has been determined, the correlation of uranium with other elements was defined, probable conditions of uranium ore genesis are described, and predicted uranium resources within the studied area are estimated.     

Isotopic Composition (δ13C, δ18O) of Carbonate Concretions from Terrigenous Deposits in the Northern Caucasus

The isotopic composition of carbon and oxygen was studied in carbonate concentrations with different compositions (calcite, dolomite, and siderite) from Jurassic, Cretaceous, and Tertiary terrigenous deposits of the Northern Caucasus. Wide variations in the isotopic composition (from 41.4 to 18.1 for ¹³C and from 11.7 to 33.5 for ¹⁸O) point to different formation conditions in the early diagenesis zone and the later catagenesis zone.     

Climate changing characteristics of Zhangye City in Heihe River basin during 1968–2005

At present, researches on climate change of the Heihe River basin mainly focus on the relationship between basin climate change and regional water resources, regional desertification and dynamic climatic seasons of sandstorm, but less on climate change of oasis region, where there are more intense and frequent human activities. Based on data of precipitation, temperature, strong wind and dust events frequencies obtained from the six meteorological stations of Zhangye region in Heihe River basin, the features of climate change during 1968–2005 were carefully studied. Results show that the regional temperature rise rate exceeded the average level of China. The annual precipitation changed a little, but the precipitation had a slowly increasing trend in spring and winter. Frequencies of strong wind and sandstorm days show obviously descending trends, which had a close correlation with the regional temperature rise and the precipitation increase in spring and winter. Meanwhile, further human economic activities and exploitations to the oasis in the inland valley of arid regions also affected the climate change of this region, which has a sensitive and fragile eco-environment. __________ Translated from Journal of Desert Research, 2007, 27(6): 1048–1054 [译自: 中国沙漠]     

New Data on Diamond–Graphite Relationships in the Gneisses of the Kokchetav Massif (Northern Kazakhstan)

The results of studying an aggregate of graphite-and-diamond crystal in tourmaline 5 μm of the Kokchetav massif by the method of transmission electron microscopy are presented. The detail studies of the interface between the crystals of graphite and diamond have revealed the absence of disordered graphite that is detail partially graphitized diamond. Intense deformation changes in the graphite crystal occurred after it was captured by tourmaline at the regression stage, which led to considerable kinking of the graphite crystal along the a-axis. Thus, the coexistence of graphite and diamond crystals cannot be unambiguously interpreted as a product of partial diamond graphitization. Graphite could have crystallized syngenetic with a diamond crystal or at the retrograde stage in the graphite stability field.