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Takayoshi Kawai - One of the best experts on this subject based on the ideXlab platform.
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centennial to millennial scale climate shifts in Continental Interior asia repeated between warm dry and cool wet conditions during the last three interglacial states evidence from uranium and biogenic silica in the sediment of lake baikal southeast siberia
Quaternary Science Reviews, 2012Co-Authors: Takuma Murakami, Takejiro Takamatsu, Nagayoshi Katsuta, Masao Takano, Koshi Yamamoto, Yoshio Takahashi, Toshio Nakamura, Takayoshi KawaiAbstract:Abstract We observed timescale-dependent changes in the correlations between biogenic silica (bioSi) and uranium concentrations of bulk sediment from the Buguldeika Saddle, Lake Baikal. There was a positive correlation for the glacial–interglacial (100 kyr) scales over the 180 kyr, with inverse correlations for centennial- to-millennial scales during the last three interglacial states (MIS 5, 3, and 1). The distinction of these correlations between the time scales suggests that the sedimentation processes of bioSi and U differ from each other. The Baikal bioSi concentration record is generally regarded as a paleotemperature proxy, reflecting the diatom production of the lake. On the other hand, we concluded that the temporal variation of the U concentration in the sediment reflected the weathering intensity in the south of Lake Baikal watershed associated with changes in the rainfall/moisture levels. Based on the paleoclimate proxies from Lake Baikal, climates in Continental Interior Asia are identified as having dry and wet conditions during the glacial and interglacial periods, respectively. This accounts for the rhythms in growth and retreat of ice sheets in Eurasia on glacial–interglacial scales. In the interglacial periods (MIS 5, 3, and 1), the Continental Interior is, contrary to the glacial–interglacial climate changes, characterized by alternating warm–dry and cool–wet climates with periods in tens of thousands years. In particular, such shifts in the climate stand out prominently at the beginning of MIS 5d. The detrended U record for the last 5.2 kyr shows wet events at 4.3–3.7, 3.2–2.3, 1.8–1.2, and 0.8–0.3 kyr. These events coincide with the timing of the North Atlantic ice-rafted debris events, which were possibly related to solar activity. All this evidence suggests that climate in the Continental Interior followed significantly different fluctuation patterns in the glacial–interglacial and shorter time scales.
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paleoenvironmental changes during the last 12 million years in the eurasian Continental Interior estimated by chemical elements in sediment cores bdp 96 and bdp 98 from lake baikal
Pages, 2003Co-Authors: Nobuki Takamatsu, Genki I Matsumoto, Naoyuki Kato, Takayoshi KawaiAbstract:The content of 29 chemical elements (Na, K, Mg, Ca, Al, Fe, Li, Be, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Ge, As, Rb, Sr, Mo, Cs, Ba, W, Pb, Th, and U) in 589 subsamples of BD-P96 cores and 703 subsamples of BDP-98 cores from the Academician Ridge of Lake Baikal were determined using inductively coupled plasma-mass spectromety (ICP-MS) in order to estimate paleoenvironmental changes during the last 12 million years in the Eurasian Continental Interior. The content of terrigenous elements (Na, K, Mg, Ca, Al, Ti, etc.) increased gradually from about 6 Ma BP to the present, with repeated major fluctuations after 3.6 Ma BP, indicating a significant climate change at 3.6Ma BP in the Eurasian Continental Interior. The abrupt change may be mainly associated with the uplift of the Tibetan plateau and Himalayas. This result corresponds with the rapid increase in the eolian dust accumulation rate in the central north Pacific sediment core (Rea et al. 1998). The data from BDP98 cores indicated that some big changes in the sources of chemical elements occurred at about 7 Ma BP, when the sedimentation rate in the core suddenly increased. We also estimated from the chemical index of alteration (CIA) that the variation in the climate from 8 to 12 Ma BP was small, and the rapid climate change started at 3.6 Ma BP.
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paleoenvironmental changes in the eurasian Continental Interior during the last 12 million years derived from organic components in sediment cores bdp 96 and bdp 98 from lake baikal
2003Co-Authors: Genki I Matsumoto, Nobuki Takamatsu, Chizu Fujimura, Koji Minoura, Tetsuo Takemura, Susumu Hayashi, Koji Shichi, Takayoshi KawaiAbstract:Organic components in combined sediment cores (BDP-96 and BDP-98) of BDP-96-1 and -2 (200 m) and BDP-98-1 and -2 (600 m) from Academician Ridge in Lake Baikal, in south-central Siberia, were studied to clarify the biological production, sources of organic matter, and paleoenvironmental changes during the last 12 million years (Myr) in the Eurasian Continental Interior as well as in the world. Total organic carbon (TOC) contents ranging from 0.13% to 2.8%, with an average of 0.93% (n = 7710), were fairly low, and were similar to those found in some oligotrophic lakes. TOC and total nitrogen (TN) contents had decreased by about half from 12 Myr ago to the present as a result of global climate cooling. Higher biological production periods are mainly attributed to the contribution of vascular plants.
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orbit related long term climate cycles revealed in a 12 myr Continental record from lake baikal
Nature, 2001Co-Authors: Kenji Kashiwaya, Shinya Ochiai, Hideo Sakai, Takayoshi KawaiAbstract:Quaternary records of climate change from terrestrial sources, such as lake sediments1,2 and aeolian sediments3,4, in general agree well with marine records5,6. But continuous records that cover more than the past one million years were essentially unavailable until recently, when the high-sedimentation-rate site of Lake Baikal was exploited1,2,7,8. Because of its location in the middle latitudes, Lake Baikal is highly sensitive to insolation changes9 and the entire lake remained uncovered by ice sheets throughout the Pleistocene epoch, making it a valuable archive for past climate. Here we examine long sediment cores from Lake Baikal that cover the past 12 million years. Our record reveals a gradual cooling of the Asian Continental Interior, with some fluctuations. Spectral analyses reveal periods of about 400 kyr, 600 kyr and 1,000 kyr, which may correspond to Milankovitch periods (reflecting orbital cycles). Our results indicate that changes in insolation were closely related to long-term environmental variations in the deep Continental Interior, over the past 12 million years.
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estimation of paleoenvironmental changes in the eurasian Continental Interior during the past 5 million years inferred from organic components in the bdp96 1
Lake Baikal#R##N#A Mirror in Time and Space for Understanding Global Change Processes, 2000Co-Authors: Genki I Matsumoto, Takayoshi Kawai, S Kosaku, N Takamatsu, T Akagi, Y AmbeAbstract:Publisher Summary This chapter presents a study on the total organic carbon (TOC), total nitrogen (TN), hydrocarbons, fatty acids, and sterols in a BDP96/1 sediment core from the Academician Ridge in Lake Baikal in relation to BDP, and compares the results with marine d18O records, to estimate paleoenvironmental changes in the Interior of the Eurasian continent during the past 5.2 million years. Low TOC content indicates low primary productivity in the drainage basin of the lake throughout the sedimentation. The TOC values fluctuates largely within a short period of time (less than 20 kilo years) reflecting short-term climate changes. The similarity of the TOC profile and marine records reveals that the climate changes in the Interior of the continent occurred simultaneously with changes in the marine environment. The TOC profile is a useful proxy for global climate change. TOC and allocthonous organic matter data indicates a fairly warm climate from 4.3 to 2.8 Ma and from 2.0 to 1.5 Ma, and a cool climate from 2.8 to 2.2 Ma and from 1.5 Ma to the present. Allochthonous organic matter was mainly supplied by inflow of fiver water in warm periods. The decrease in relative abundance of n-C27 alkane and n-C26 alkanoic acid from about 4 Ma to the present, suggests a decrease in the contribution of Populas spp. and Salix spp. In the drainage basin of the lake, the increase in relative abundance of n-C31 alkane from about 4 Ma to the present probably reflects an increase in herbaceous plants due to aridification of the climate.
Alexander A. Prokopenko - One of the best experts on this subject based on the ideXlab platform.
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climate in Continental Interior asia during the longest interglacial of the past 500 000 years the new mis 11 records from lake baikal se siberia
Climate of The Past, 2010Co-Authors: Alexander A. Prokopenko, M I Kuzmin, E V Bezrukova, G K Khursevich, E P Solotchina, Pavel E TarasovAbstract:Abstract. A synthesis of paleoclimate responses from Lake Baikal during the MIS 11 interglacial is presented based on proxy records from two drill sites 245 km apart. BDP-99 is located in vicinity of the delta of the major Baikal tributary, whereas the BDP-96 site represents hemipelagic setting distant from riverine influence. The comparison of thicknesses of interglacial intervals in these contrasting depositional settings confirms the extended ca. 33-kyr duration of the MIS 11 interglacial. The new BDP-99 diatom biostratigraphic record matches that of the BDP-96-2 holostratotype and thus allows establishing establishes robust correlation between the records on the same orbitally-tuned timescale. The first detailed MIS 11 palynological record from the BDP-99 drill core indicates the dominance of boreal conifer (taiga) forest vegetation in the Baikal region throughout the MIS 11 interglacial, since at least 424 ka till ca. 396 ka. The interval ca. 420–405 ka stands out as a "conifer optimum" with abundant Abies sibirica, indicative of climate significantly warmer and less Continental than today. The closest Baikal analog to this type of vegetation in the history of the current Holocene interglacial is at ca. 9–7 ka. The warm conifer phase lasted for ca. 15 kyr during MIS 11 interrupted by two millennial-scale cooling episodes at ca. 411–410 and 405–404 ka. Reconstructed annual precipitation of 450–550 mm/yr during the MIS 11 interglacial is by ca. 100 mm higher than during the Holocene; regional climate was less Continental with warmer mean temperatures both in summer and in winter. At both drill sites, the two-peak structure of the MIS 11 diatom abundance profiles reflects the orbital signature of precession in the interglacial paleoclimate record of Continental Eurasia. MIS 11 interglacial was characterized by the sustained high level of primary production and accumulation of autochthonous organic matter at both study sites. The responses of paleoclimate-sensitive indices in the mineralogy of the MIS 11 sediments in BDP-96-2 are consistent with those during the Holocene. Illitization of secondary clay minerals in the Baikal watershed was an important process, but it appears to have been subdued during the first half of the MIS 11, apparently due to elevated humidity and muted seasonality of regional climate.
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Lake Hovsgol basin as a new study site for long Continental paleoclimate records in Continental Interior Asia: General context and current status
Quaternary International, 2009Co-Authors: Alexander A. Prokopenko, Mikhail I. Kuzmin, Kyung-sik Woo, Norm CattoAbstract:Abstract Lacustrine sedimentary strata in the Lake Hovsgol rift basin, NW Mongolia, preserved an important regional archive with new powerful proxies for climate change in Continental Interior Asia. Two scientific drilling campaigns of the Hovsgol Drilling Project (HDP) recovered the most complete and best resolved mid-late Pleistocene paleoclimate archive in Mongolia. With the basal age of ca. 1 Ma, Lake Hovsgol drill core section complements those obtained previously in the neighboring Lake Baikal, and contains regional paleoclimate proxy records on a timescale comparable to that of marine sedimentary records and the longest Antarctic ice core record. Works in this volume discuss changes in lake chemistry, biota and environment, closely linked with drill core lithology and depositional trends apparent from sediment facies. The current collection of works illustrates the potential of proxy signals in the Hovsgol record and highlights new important constraints on their interpretation. Because of a nearly continuous record of endogenic carbonate accumulation in Lake Hovsgol, a wealth of paleoclimate proxy data is preserved in carbonate mineralogy, elemental geochemistry and stable isotope composition; such a unique long record was not previously available in this part of the world. The repetitive pattern of changes in the lake's water budget in response to the climatic cycles of the Pleistocene is established and constrained by absolute dating and the robust paleomagnetic event/reversal timescale. The new proxy records from the HDP sediment sections are both relevant and timely contributions to the discussion of the nature of paleoclimate changes in Continental Interior Asia during prior glacial and interglacial intervals of the Pleistocene. These records help establish the early timing of the post-glacial changes in atmospheric circulation and effective moisture budget in the region and resolve the previously proposed scenarios of extreme precipitation gradients during glacial periods. The key primary data presented in this volume make a compelling case for further in-depth studies of the available records and for future deeper drilling into the early Pleistocene and the Pliocene strata in this basin.
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lake baikal record of Continental climate response to orbital insolation during the past 5 million years
Science, 1997Co-Authors: Douglas F Williams, Alexander A. Prokopenko, John A Peck, Eugene B Karabanov, Vadim A Kravchinsky, John W King, M I KuzminAbstract:The sedimentary record of biogenic silica from Lake Baikal in south-central Siberia suggests that this region of central Asia was impacted by two major cooling episodes at 2.8 to 2.6 and 1.8 to 1.6 million years ago. The spectral evolution of this Continental Interior site parallels the evolutionary frequency spectra for various marine oxygen isotope records. In the Baikal record, the 41,000-year obliquity cycle is particularly strong from 1.8 to 0.8 million years ago; variance in the 100,000-year eccentricity band increases during the past 0.8 million years. The expected precession frequency of 23,000 years is highest during the past 400,000 years. The modulation of the predicted 23,000- and 41,000-year insolation forcing by the 100,000- and 400,000-year eccentricity bands indicates that the transfer of variance from the precession and obliquity frequencies to the eccentricity part of the spectrum occurred in the Eurasian Continental Interior, as well as in tropical and high-latitude ocean sites.
Pavel E Tarasov - One of the best experts on this subject based on the ideXlab platform.
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climate in Continental Interior asia during the longest interglacial of the past 500 000 years the new mis 11 records from lake baikal se siberia
Climate of The Past, 2010Co-Authors: Alexander A. Prokopenko, M I Kuzmin, E V Bezrukova, G K Khursevich, E P Solotchina, Pavel E TarasovAbstract:Abstract. A synthesis of paleoclimate responses from Lake Baikal during the MIS 11 interglacial is presented based on proxy records from two drill sites 245 km apart. BDP-99 is located in vicinity of the delta of the major Baikal tributary, whereas the BDP-96 site represents hemipelagic setting distant from riverine influence. The comparison of thicknesses of interglacial intervals in these contrasting depositional settings confirms the extended ca. 33-kyr duration of the MIS 11 interglacial. The new BDP-99 diatom biostratigraphic record matches that of the BDP-96-2 holostratotype and thus allows establishing establishes robust correlation between the records on the same orbitally-tuned timescale. The first detailed MIS 11 palynological record from the BDP-99 drill core indicates the dominance of boreal conifer (taiga) forest vegetation in the Baikal region throughout the MIS 11 interglacial, since at least 424 ka till ca. 396 ka. The interval ca. 420–405 ka stands out as a "conifer optimum" with abundant Abies sibirica, indicative of climate significantly warmer and less Continental than today. The closest Baikal analog to this type of vegetation in the history of the current Holocene interglacial is at ca. 9–7 ka. The warm conifer phase lasted for ca. 15 kyr during MIS 11 interrupted by two millennial-scale cooling episodes at ca. 411–410 and 405–404 ka. Reconstructed annual precipitation of 450–550 mm/yr during the MIS 11 interglacial is by ca. 100 mm higher than during the Holocene; regional climate was less Continental with warmer mean temperatures both in summer and in winter. At both drill sites, the two-peak structure of the MIS 11 diatom abundance profiles reflects the orbital signature of precession in the interglacial paleoclimate record of Continental Eurasia. MIS 11 interglacial was characterized by the sustained high level of primary production and accumulation of autochthonous organic matter at both study sites. The responses of paleoclimate-sensitive indices in the mineralogy of the MIS 11 sediments in BDP-96-2 are consistent with those during the Holocene. Illitization of secondary clay minerals in the Baikal watershed was an important process, but it appears to have been subdued during the first half of the MIS 11, apparently due to elevated humidity and muted seasonality of regional climate.
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present day and mid holocene biomes reconstructed from pollen and plant macrofossil data from the former soviet union and mongolia
Journal of Biogeography, 1998Co-Authors: Thompson Webb, Pavel E Tarasov, Andrei Andreev, N B Afanaseva, N Berezina, Ludmila G Bezusko, Tatyana A Blyakharchuk, N S Bolikhovskaya, Rachid CheddadiAbstract:Fossil pollen data supplemented by tree macrofossil records were used to reconstruct the vegetation of the Former Soviet Union and Mongolia at 6000 years. Pollen spectra were assigned to biomes using the plant-functional-type method developed by Prentice et al. (1996). Surface pollen data and a modern vegetation map provided a test of the method. This is the first time such a broad-scale vegetation reconstruction for the greater part of northern Eurasia has been attempted with objective techniques. The new results confirm previous regional palaeoenvironmental studies of the mid-Holocene while providing a comprehensive synopsis and firmer conclusions. West of the Ural Mountains temperate deciduous forest extended both northward and southward from its modern range. The northern limits of cool mixed and cool conifer forests were also further north than present. Taiga was reduced in European Russia, but was extended into Yakutia where now there is cold deciduous forest. The northern limit of taiga was extended (as shown by increased Picea pollen percentages, and by tree macrofossil records north of the present-day forest limit) but tundra was still present in north-eastern Siberia. The boundary between forest and steppe in the Continental Interior did not shift substantially, and dry conditions similar to present existed in western Mongolia and north of the Aral Sea.
M I Kuzmin - One of the best experts on this subject based on the ideXlab platform.
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climate in Continental Interior asia during the longest interglacial of the past 500 000 years the new mis 11 records from lake baikal se siberia
Climate of The Past, 2010Co-Authors: Alexander A. Prokopenko, M I Kuzmin, E V Bezrukova, G K Khursevich, E P Solotchina, Pavel E TarasovAbstract:Abstract. A synthesis of paleoclimate responses from Lake Baikal during the MIS 11 interglacial is presented based on proxy records from two drill sites 245 km apart. BDP-99 is located in vicinity of the delta of the major Baikal tributary, whereas the BDP-96 site represents hemipelagic setting distant from riverine influence. The comparison of thicknesses of interglacial intervals in these contrasting depositional settings confirms the extended ca. 33-kyr duration of the MIS 11 interglacial. The new BDP-99 diatom biostratigraphic record matches that of the BDP-96-2 holostratotype and thus allows establishing establishes robust correlation between the records on the same orbitally-tuned timescale. The first detailed MIS 11 palynological record from the BDP-99 drill core indicates the dominance of boreal conifer (taiga) forest vegetation in the Baikal region throughout the MIS 11 interglacial, since at least 424 ka till ca. 396 ka. The interval ca. 420–405 ka stands out as a "conifer optimum" with abundant Abies sibirica, indicative of climate significantly warmer and less Continental than today. The closest Baikal analog to this type of vegetation in the history of the current Holocene interglacial is at ca. 9–7 ka. The warm conifer phase lasted for ca. 15 kyr during MIS 11 interrupted by two millennial-scale cooling episodes at ca. 411–410 and 405–404 ka. Reconstructed annual precipitation of 450–550 mm/yr during the MIS 11 interglacial is by ca. 100 mm higher than during the Holocene; regional climate was less Continental with warmer mean temperatures both in summer and in winter. At both drill sites, the two-peak structure of the MIS 11 diatom abundance profiles reflects the orbital signature of precession in the interglacial paleoclimate record of Continental Eurasia. MIS 11 interglacial was characterized by the sustained high level of primary production and accumulation of autochthonous organic matter at both study sites. The responses of paleoclimate-sensitive indices in the mineralogy of the MIS 11 sediments in BDP-96-2 are consistent with those during the Holocene. Illitization of secondary clay minerals in the Baikal watershed was an important process, but it appears to have been subdued during the first half of the MIS 11, apparently due to elevated humidity and muted seasonality of regional climate.
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lake baikal record of Continental climate response to orbital insolation during the past 5 million years
Science, 1997Co-Authors: Douglas F Williams, Alexander A. Prokopenko, John A Peck, Eugene B Karabanov, Vadim A Kravchinsky, John W King, M I KuzminAbstract:The sedimentary record of biogenic silica from Lake Baikal in south-central Siberia suggests that this region of central Asia was impacted by two major cooling episodes at 2.8 to 2.6 and 1.8 to 1.6 million years ago. The spectral evolution of this Continental Interior site parallels the evolutionary frequency spectra for various marine oxygen isotope records. In the Baikal record, the 41,000-year obliquity cycle is particularly strong from 1.8 to 0.8 million years ago; variance in the 100,000-year eccentricity band increases during the past 0.8 million years. The expected precession frequency of 23,000 years is highest during the past 400,000 years. The modulation of the predicted 23,000- and 41,000-year insolation forcing by the 100,000- and 400,000-year eccentricity bands indicates that the transfer of variance from the precession and obliquity frequencies to the eccentricity part of the spectrum occurred in the Eurasian Continental Interior, as well as in tropical and high-latitude ocean sites.
Claire A Currie - One of the best experts on this subject based on the ideXlab platform.
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are diamond bearing cretaceous kimberlites related to low angle subduction beneath western north america
Earth and Planetary Science Letters, 2011Co-Authors: Claire A Currie, Christopher BeaumontAbstract:Abstract Diamond-bearing Cretaceous kimberlites of western North America were emplaced 1000–1500 km inboard of the Farallon plate subduction margin and overlap with the development of the Western Interior Seaway, shut-down of the Sierra Nevada arc, and the Laramide orogeny. These events are consistent with a decrease in subduction angle along much of the margin, which placed the subducted Farallon plate in close proximity to the Continental Interior at the time of kimberlite magmatism. Our numerical models demonstrate that low-angle subduction can result from high plate convergence velocities and enhanced westward motion of North America. Further, rapid subduction allows hydrous minerals to remain stable within the cool Interior of the subducting plate to more than 1200 km from the trench. Destabilization of these minerals provides a fluid source that can infiltrate the overlying material, potentially triggering partial melting and kimberlite/lamproite magmatism.
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subduction erosion modes comparing finite element numerical models with the geological record
Earth and Planetary Science Letters, 2009Co-Authors: Duncan Fraser Keppie, Claire A Currie, Clare J. WarrenAbstract:article i nfo During subduction erosion, the upper plate is tectonically eroded by the subducting plate and carried into the mantle. The geological record suggests that subduction erosion is a fundamental process at subduction margins; however the underlying causes are not well constrained. Finite-element numerical models of ocean-continent subduction are used to investigate the roles of crustal frictional strength, subduction angle, and convergence rate in subduction erosion processes. Subduction erosion occurs in models in which the plate boundary zone is moderately strong, due to either high frictional strength or shallow angle of subduction. The models exhibit two distinct modes of subduction erosion: (1) steady, with slow trench migration rates (<4 km Ma −1 ), subsidence in the remaining forearc, and a decrease in the angle of subduction, in which the edge of the Continental plate is eroded in small blocks, and (2) unsteady, with fast trench migration rates (⋙15 km Ma −1 ), subsidence at the end of the process, and an increase in the angle of subduction, in which a large block of Continental forearc is removed. The unsteady mode is compatible with the sudden migration of the volcanic arc into the Continental Interior, a concurrent hiatus in arc volcanic production, and geochemical signatures showing crustal (forearc) contamination in the magma source region when arc volcanism renews in its new location. Both modes are inhibited by the presence of a thick sediment layer within the subduction zone, and neither mode requires the presence of topographic asperities on the lower plate. In natural subduction zones, subduction erosion may initially occur through steady erosion at the edge of the Continental plate. As material is removed, the subduction angle may gradually decrease, increasing the strength of the plate boundary zone. The increased strength may lead to failure in the Continental Interior, unsteady removal of a large forearc block and relocation of the subduction zone into the upper plate where the cycle may repeat. The proposed cycle may explain observed patterns in the Andean margin, including steady and unsteady erosion recorded in the geological record and along-strike variation in present-day subduction angles.