A Record of Humidity Changes in Sections of a Valley Peatbog in the Southern Part of the Far East

Doklady Earth Sciences - Comprehensive study of sections of mares in the Bolshaya Ussurka River basin has allowed highlighting climate changes over the past 2900 years. Reconstructions are based on...     

Reconstruction of Holocene Environmental Changes in North-Western Pacific in Relation to Paleorecord from Shikotan Island

Doklady Earth Sciences - Results of a paleolimnological investigation of a well-dated lake sediment section from Shikotan Island (Southern Kurils) showed that from ca 8.0 to 5.8 cal ka BP a warm...     

Noble metals in graphite-bearing rocks of the Liumao deposit (China)

Native gold, platinum, nickel, and other ore minerals have been discovered in graphite-bearing rocks of the Liumao deposit (Heilongjiang province, China). The results obtained are similar to the previously published materials on the mineralogy of carbon-rich formations of the Tamga and Turgenevo deposits (Primorye, Russian Far East) located in the same region of graphitization in the Khankai terrane as the Chinese object. The defined similarities are most likely explained by participation of deep reduced fluids in the process of ore genesis.     

Development of lacustrine-boggy sedimentary environments in the ancient Rasshua Island caldera (Central Kuril Islands) in the Holocene

The evolution stages of the lacustrine-boggy sedimentary environments and the role of the climatic and volcanic factors were reconstructed on the basis of complex stratigraphic (botanical, palynological, and diatom analyses and tephrostratigraphy) and radiocarbon studies of the peat lands on Rasshua Island during the middle-late Holocene. The stages of the landscape evolution and the time of their reorganization were determined.     

Lacustrine transgressions in the late Cenozoic Ussuri-Khanka depression (Primor’e)

In the Ussuri-Khanka depression of Primorye, the Quaternary alluvial-lacustrine and lacustrine sedimentogenesis progressed under conditions of transgressive accumulation in response to the depression tectonic subsidence and recurrent climatic fluctuations. The alluvial dams and irregular accumulation are proved to have been the leading factors of lakes’ formation within the depression. As is shown, fluctuations of the water level in limnic reservoirs depended on the climatic changes. New data considered in this work confirm the lacustrine genesis of a greater part of the Middle Pleistocene-Holocene sedimentary succession in the Khanka depression. Two transgressive phases, when the water level in the lakes rose by 1.5–2.0 m above the present one, are established for the Subboreal. The general conclusion is that the mesorhythmic structure of the sedimentary succession in the Ussuri-Khanka depression reflects the influence of climatic fluctuations in the Late Cenozoic.     

The peat bog of Ketoi Island: The Middle-Upper Holocene reference section of the Central Kuriles

The results of the complex study of a Holocene peat bog in the southern part of Ketoi Island, which is proposed to serve as a reference section for the Central Kuriles, are discussed. The peat bog’s stratigraphy is based on botanic, palynological, and diatom data, 16 radiocarbon age determinations, and the composition of the volcanic ashes. The peat accumulation initiated approximately 6500 years ago. The successive changes of the island’s vegetation are traced through the Middle-Late Holocene with defining of the phases of its development and dating the paleolandscape transformations related to the climatic oscillations and volcanic eruptions.     

Natural-environment dynamics within the Amur basin during the Neoglacial

We examine the natural-environment development dynamics within the Amur basin during the Neoglacial. The study revealed the opposing directedness in climate humidity changes for different parts of the basin. In the maritime and inland parts, a cooling was accompanied by an increase and decrease in humidity, respectively. It is established that a cooling in the maritime part of the basin led to a shift of the boundaries of vegetation zones, an enhancement in waterlogging of bog systems, and to a change of biogeocenoses. In the inland part of the basin, an enhancement in aridization was conducive to a retrogression of the lakes’ level, and to an intensification of aeolian processes.     

Coastal Sedimentation Associated with the Tohoku Tsunami of 11 March 2011 in South Kuril Islands, NW Pacific Ocean

Sediment deposited by the Tohoku tsunami of March 11, 2011 in the Southern Kurils (Kunashir, Shikotan, Zeleniy, Yuri, Tanfiliev islands) was radically different from sedimentation during local strong storms and from tsunamis with larger runup at the same location. Sediments from the 2011 Tohoku tsunami were surveyed in the field, immediately and 6 months after the event, and analyzed in the laboratory for sediment granulometry, benthos Foraminifa assemblages, and diatom algae. Run-up elevation and inundation distance were calculated from the wrackline (accumulations of driftwood, woody debris, grass, and seaweed) marking the distal edge of tsunami inundation. Run-up of the tsunami was 5 m at maximum, and 3–4 m on average. Maximum distance of inundation was recorded in river mouths (up to 630 m), but was generally in the range of 50–80 m. Although similar to the local strong storms in runup height, the tsunami generally did not erode the coast, nor leave a deposit. However, deposits uncharacteristic of tsunami, described as brown aleuropelitic (silty and clayey) mud rich in organic matter, were found in closed bays facing the South Kuril Strait. These closed bays were covered with sea ice at the time of tsunami. As the tsunami waves broke the ice, the ice floes enhanced the bottom erosion on shoals and destruction of low-lying coastal peatland even at modest ranges of runup. In the muddy tsunami deposits, silt comprised up to 64 % and clay up to 41.5 %. The Foraminifera assemblages displayed features characteristic of benthic microfauna in the near-shore zone. Deep-sea diatoms recovered from tsunami deposits in two closely situated bays, namely Krabovaya and Otradnaya bays, had different requirements for environmental temperature, suggesting these different diatoms were brought to the bays by the tsunami wave entraining various water masses when skirting the island from the north and from the south.     

Response of Landscapes of the Sikhote-Alin Western Slopes to the Middle–Late Holocene Climatic Changes

The response of landscape biotic components of the western slope of the Sikhote-Alin Mountains (Bikin River middle flow) to the Middle–Late Holocene climate changes is discussed. The paleoreconstruction object was the Krasny Yar mari, which developed under the control of multidirectional short-term climatic changes. The last millennium was marked by particularly rapid and frequent changes in the local landscapes. The closely spaced orographic barrier strongly affected the development of biotic components and changes in the swamp hydrological regime. The moisture dynamics within the river catchment considerably controlled the development and change of the peat-forming plants. Several stages of the mari development were reconstructed; each began from the accumulation of eutrophic peat. It was followed by the transitional eutrophic–mesotrophic stage, with a higher role of atmospheric supply. The larch forests appeared in this part of the valley within the Atlantic–Subboreal cooling period. Korean pine developed in the forest vegetation in the low mountain relief at the beginning of the Subboreal and became one of the leading trees ~2.6–2.3 ka BP. The lower role of the Korean pine and birch forest expansion in the first half of the Subatlantic could be related to the fires. The broadleaf–Korean pine forests became widespread in the Medieval Warm Period. Local swamp landscapes changed dramatically in the Little Ice Age, while the slope vegetation was not subject to any major changes. The landscapes were also affected by the fires, which became more frequent. The derivative communities with birch appeared on the mari. Moreover, this part of the valley was occasionally subject to heavy flooding.