Description: High-resolution records of ice-rafted debris (IRD) and oxygen isotope records spanning an E–W-trending transect across the Okhotsk Sea unravel the marine and terrestrial cryogenic history of NE-Siberia over the last 350 kyr. IRD, predominantly dispersed basin-wide by sea-ice, shows lowest fluxes during interglacial periods implying a reduced and seasonal sea-ice coverage. Highest IRD accumulation rates are observed during glacial and deglacial periods with a more extended, but highly dynamic ice cover. Although being rather synchronous, IRD fluxes are on average higher in the western Okhotsk Sea than in the eastern part, pointing to a persistent but mobile, particle-supplying sea-ice cover even during full glacial conditions, presumably less dense in the eastern parts. MIS 6 is exceptional in this respect: Asynchronous fluxes of IRD, which vary spatially, reflect rapid paleoclimatic and paleo-glaciomarine changes. IRD accumulation rates were by factor 2–3 higher during MIS 6 as compared to the last glacial maximum, and the IRD depositional center shifted from the western Okhotsk Sea (early MIS 6) toward Kamchatka (late MIS 6), synchronous to a distinct change in the IRD mineral composition. Both, the characteristic composition of late MIS 6 IRD originating from the Sredinny Mountain Range of Kamchatka and their significantly enhanced accumulation rates refer to intensified iceberg dispersal across the eastern part of the Okhotsk Sea at ~138 ka, ~135 ka, ~129 ka, and ~128 ka BP. This scenario affords the presence of extended mountain glaciers protruding down to sea level on the western side of Kamchatka. Anomalously light planktonic stable oxygen isotopes during MIS 6.3, Termination II and MIS 5.5–5.4 suggest significant freshwater supply related to the westward drainage of Kamchatka glaciers. The intensified Kamchatka glaciation observed during late MIS 6 was repeated during MIS 3. Iceberg discharges into the eastern Okhotsk Sea are observed at ~60 ka, ~51 ka, ~42 ka, ~38 ka, ~36 ka, and ~31 ka, and may partly correspond to N-Atlantic Heinrich Events.

Description: The fullest summary on composition, age and distribution of 23 tephra layers detected and investigated in the Okhotsk Sea Pleistocene-Holocene deposits is presented. Seven tephra layers are surely identified with powerful explosive eruptions of volcanoes of Kamchatka, Kurile and Japanese Islands. For them, the areas of ash falls including which weren't revealed earlier on the land are specified and established. It is estimated that explosive eruptions of volcanoes of the Kamchatka Sredinny Range were the sources for three tephra layers. Complex investigations of morphological, mineralogical and chemical composition of tephras including composition of rare and earth-rare elements (electron microprobe analysis and laser ablation method - LA ICP MS) have been made for all studied layers. They were a basis for tephrostratigraphic correlation of the regional deposits promoting to specification of stages of volcanic explosive activity in this region.

Description: This paper presents the first detailed study of a late Pleistocene marine tephra sequence from the NW Pacific, downwind from the Kamchatka volcanic arc. Sediment core SO201-2-40, located on the Meiji Rise similar to 400 km offshore the peninsula, includes 25 tephras deposited within the last 215 ka. Volcanic glass from the tephras was characterized using single-shard electron microprobe analysis and laser ablation inductively coupled mass spectrometry. The age of tephras was derived from a new age model based on paleomagnetic and paleoclimate studies. Geochemical correlation of distal tephras to Kamchatkan pyroclastic deposits allowed the identification of tephras from the Karymsky, Gorely, Opala and Shiveluch eruptive centers. Three of these tephras were also correlated to other marine and terrestrial sites and hence are identified as the best markers for the north-west Pacific region. These are an early Holocene tephra from the Karymsky caldera (similar to 8.7 ka) and two tephras falling into the Marine Isotope Stage (MIS) 6 glacial time: an MIS 6.4 tephra from Shiveluch (similar to 141 ka) and the MIS 6.5 Rauchua tephra (similar to 175 ka) from Karymsky. The data presented in this study can be used in paleovolcanological and paleoceanographic reconstructions.

Description: Physical properties (water content, bulk density, magnetic susceptibility, natural remanent magnetization, nature of magnetization, and composition of ferromagnetic fraction), chemical, and (optionally) mineral composition of bottom sediments from the north-west Sea of Japan have been studied. Their stratigraphic subdivision based on composition of diatoms has been carried out. Obtained data have allowed to find out some aspects of influence of paleogeographic conditions and diagenetic processes on change of physical properties of the sediments, as well as on their composition in Holocene and Late Pleistocene.

Description: The long-chain diol index (LDI) is a new organic sea surface temperature (SST) proxy based on the distribution of long-chain diols. It has been applied in several environments but not yet in subpolar regions. Here, we tested the LDI on surface sediments and a sediment core from the Sea of Okhotsk, which is the southernmost seasonal sea ice covered region in the Northern Hemisphere, and compared it with other organic temperature proxies, i.e. Uk'37 and TEXL86. In the surface sediments, the LDI is correlated with autumn sea surface temperature, similar to the Uk'37 but different from the TEXL86 that correlates best with summer sea subsurface temperature. Remarkably, the obtained local LDI calibration was significantly different from the global core-top calibration. We used the local LDI calibration to reconstruct past SST changes in the central Sea of Okhotsk. The LDI-SST record shows low glacial (Marine Isotope Stage, MIS 2, 4, 6) and high interglacial (MIS 1 and MIS 5) temperatures and follows the same pattern as the Uk'37-SST and a previously published TEXL86 temperature record. Similar to the modern situation, the reconstructed temperatures during the interglacials likely reflect different seasons, i.e. summer for the TEXL86 and autumn for Uk'37 and LDI. During glacials, the reconstructed temperatures of all three proxies are similar to each other, likely reflecting summer temperatures as this was the only season free of sea ice. Our results suggest that the LDI is a suitable proxy to reconstruct subpolar sea water temperatures.

Description: Sediment core LV53-27 (41° 54′ N, 132° 33′ E) was retrieved in the northwestern Sea of Japan (Pervenets Seamount) at 1698 m depth during a joint Russian-Chinese expedition LV53 on RV “Akademik M.A. Lavrentyev” in 2010-11-10T23:39:00. The 757-cm long core was characterized by clay/silty clay sediments with alternating dark and light layers. in order to investigate millenial-scale climate changes with ultra-high resolution digital image of this sediment core was processed. Sediment core LV53-27 recovered about 120 kyr according to age model (Gorbarenko et al., submitted to Global and Planetary Changes). Age model was based on correlation of magnetic susceptibility, chlorin content and lightness records with similar records of well-dated sediment core MD01-2407. The magnetic susceptibility (MS) of the sediments was measured in cube samples throughout the core at 2-cm intervals using an AGICO Kappabridge MFK1-FA. These measurements were performed at the Laboratory of Cenozoic Geology and Paleomagnetism of the North-East Interdisciplinary Scientific Research Institute in Magadan, Russia. Data presented as natural logarithm of units SI (International System of Units) Chlorin content was measured with pretreatment procedures and analytical reagents, as proposed by Harris et al. (1996), using a Shimadzu UV-1650PC spectrophotometer at 1 cm resolution. Color lightness (CL) of the sediments was measured using the original photocolorimeter based on a Canon 50D digital camera. One-meter core sections with 14 cm diameter were split into two halves, while performing surface smoothing. Two flash units with soft boxes were used for creating an even and diffused illumination of the sediment surface. Camera shooting was performed with the following settings: ISO 100, 1/100'' exposure, and 8.0 focal ratio. Every image covered approximately 40 cm of the core section with approximately 11 pixels per 1 mm stratigraphic resolution. The X-rite Color Checker was used for calibrating the white balance of each image. Digital images were processed with the RTImageProc software for calculating the CL data from black (0) to white (255) with 1-pixel resolution and averaged with 1 mm step. Need to note that the width of the analyzed window of each image (80 mm) in the studied core allow to significantly reduce the possible effect of the sediment bioturbation by organisms several millimeters in diameter.