Pedogeomorphology, geochronology and paleobotany of soil profiles obtained in the Kyichu River catchment, sourthern Tibet

Results of pedogeomorphological, geochronological and paleobotanical investigations are presented covering the last ca. 4,000 years. The study sites are located in the heavily degraded Kyichu River catchment around Lhasa at 3,600-4,600 m a.s.l. Repeatedly, colluvial sediments have been recorded overlying paleosols. These deposits can be divided into i) coarse-grained sediments with a high proportion of stones and boulders originating from alluvial fans and debris flows, ii) matrix supported sediments with some stones and boulders originating from mudflows or combined colluvial processes such as hillwash plus rock fall, and iii) fine-grained sediments originating from hill wash. The IRSL multi-level dating of profile QUG 1 points to a short-time colluvial sedimentation between 1.0 ± 0.1 and 0.8 ± 0.1 ka. In contrast, dated paleosols of profile GAR 1 (7,908 ± 99 and 3,668 ± 57 BP) encompass a first colluvial episode. Here, the upper colluvial sedimentation took place during several periods between 2.6 ± 0.3 and 0.4 ± 0.1 ka. For the first time in Tibet, a systematic extraction, determination and dating of charcoals from buried paleosols was conducted. The charcoals confirm the Late Holocene presence of juniper forests or woodlands in a now treeless, barren environment. A pollen diagram from Lhasa shows a distinct decline of pollen of the Jumperus-type around 4,140 ± 50 BP, which is interpreted as indicating a clearing of forests on the adjacent slopes. It is assumed that the environmental changes from forests to desertic rangelands since ca. 4,000 BP have been at least reinforced by humans.

Some hydrophysical and hydrochemical parameters of the upper part of the hydrogen sulfide zone in the Black Sea, September 11-22, 1994

Features of spatial variability of hydrogen sulfide in the northeastern part of the Black Sea are estimated. Some technical aspects of H2S concentration determination in the anoxic zone are discussed: in its upper part at H2S concentration <30 µmol/l, the photometric method is recommended, while for deeper layers the iodometric method should be used. With linearity of vertical distribution of hydrogen sulfide and ammonium taken into account their vertical gradients are estimated as 0.49+/-0.04 µmol/m and 0.19+/-0.06 µmol/m respectively. It is shown that the upper boundary of the H2S layer corresponds to the isopycnal surface with Sigma_t = 16.19+/-0.05 arbitrary units. Special attention is paid to relationship of hydrogen sulfide distribution with hydrophysical features in the region under study, in particular in the coastal zone. It is shown that hydrodynamic conditions control spatial distribution of hydrogen sulfide. On the basis of isopycnal treatment of the H2S field existence of a coastal convergence zone is proved, and peculiarities are recognized of vertical circulation in the main Black Sea gyre and coastal anticyclonic eddies; here hydrogen sulfide serves as a tracer of hydrophysical mixing processes.

Composition and age of volcanic rocks from the Sinii Utes Depression, Southern Primoye

New data are reported on structure of sections, chemical composition, and age of volcano-sedimentary and volcanic rocks from the Sinii Utes Depression in the Southern Primorye region. The Sinii Utes Depression is filled with two sequences: the lower sequence composed of sedimentary-volcanogenic coaliferous rocks (the stratotype of the Sinii Utes Formation) and the upper sequence consisting of tephroid with overlying basalts. This work considers chemical composition and problems of K-Ar dating of basalts. The uppermost basaltic flow has K-Ar age 22.0±1.0 Ma. The dates obtained for the middle and upper parts of lava flows are underestimated. It is explained by their heating due to combustion of brown coals of the Sinii Utes Formation underlying the lava flow. Calculations show that argon could only partly have been removed from the basalts owing to conductive heat transfer and was lost largely due to infiltration of hot gases in heterogeneous fissured medium. Basaltic volcanism on continental margins of the southern Primorye region and the adjacent Korean and Chinese areas at the Oligocene-Miocene boundary preceded Early-Middle Miocene spreading and formation of the Sea of Japan basin. Undifferentiated moderately alkaline basalts of intraplate affinity developed in the Amba Depression and some other structures of the southern Primorye region and intraplate alkali basalts of the Phohang Graben in the Korean Peninsula serve as indicators of incipient spreading regime in the Sea of Japan. Potassic basalt-trachybasalt eruptions occurred locally in riftogenic depressions and shield volcanoes. In some structures this volcanism was terminated by eruptions of intermediate and acid lavas. Such evolution of volcanism is explained by selective contamination of basaltic melts during their interaction with crustal acid material and generation of acid anatectic melts.

Composition of swamp waters from the lower Tom' River Basin

New data on chemical and trace component compositions of acidic and low acidic swamp waters and other types of low mineralized waters are reported in the paper. Special attention is paid to dissolved organic compounds: fulvic and humic acids, bitumen, and hydrocarbons. For the first time detailed data on organic trace components (alkanes, pentacyclic terpenoids, steranes, alkylbenzenes, naphthalenes, phenanthrenes, tetraarenes, etc.) in the swamp waters of the Western Siberia: are reported.

Oxygen contents, sulfate concentrations, and changes of IPLs under different storage conditions of samples from ODP Leg 204 and IODP Expedition 311

We have studied the effects of slow infiltration of oxygen on microbial communities in refrigerated legacy samples from ocean drilling expeditions. Storage was in heat-sealed, laminated foil bags with a N2 headspace for geomicrobiological studies. Analysis of microbial lipids suggests that Bacteria were barely detectable in situ but increased remarkably during storage. Detailed molecular examination of a methane-rich sediment horizon showed that refrigeration triggered selective growth of ANME-2 archaea and a drastic change in the bacterial community. Subsequent enrichment targeting methanogens yielded exclusively methylotrophs, which were probably selected for by high sulfate levels caused by oxidation of reduced sulfur species. We provide recommendations for sample storage in future ocean drilling expeditions.