All ICDP Publications with Abstracts
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1369.
Authigenic, detrital and diagenetic minerals in the Laguna Potrok Aike sediment sequence
Quaternary Science Reviews,
71109 – 118
2013
Keywords:▾
Argentina; Laguna Potrok Aike; Santa Cruz [Argentina]; Clay; Crystallography; Glacial geology; Lakes; Mineralogy; Sedimentology; Sediments; Uranium; X ray diffraction analysis; Argentina; ICDP-PASADO; Late quaternary; Paleoclimates; Vivianite; XRD; authigenesis; calcite; carbon flux; geochronology; Holocene; Last Glacial Maximum; mineral; mineralogy; primary production; radiocarbon dating; redox potential; vivianite; X-ray diffraction; Phosphate minerals
Abstract: ▾ The ~100m-long Laguna Potrok Aike sediment sequence yielded a record spanning the Last Glacial period to the Holocene. This paper presents and discusses two aspects of the mineralogy of the lake. The first aspect is based on a semi-quantitative X-ray diffraction analysis of bulk and clay mineralogical assemblages. Minor mineralogical changes are observed throughout the glacial section suggesting relatively uniform sediment sources. The transition into the Holocene is characterized by increasing fluxes of endogenic calcite thought to relate to lower lake levels. The second aspect is based on analysis of uranium-series disequilibria in diagenetic vivianite from the glacial section. U-series ages were expected to yield minimum ages for the host-sediment. Unfortunately, very little authigenic U is present in vivianite grains. The low primary productivity of the lake and thus low organic carbon fluxes might have prevented the development of strong redox gradients at the water-sediment interface and thus reduced diagenetic U-uptake into the sediment. One vivianite sample, at a 56.9m composite depth, yielded enough authigenic uranium to calculate a 230Th-age of 29.4±5.9ka (±2σ). This age is younger than the one indicated by the radiocarbon chronology. It is thus concluded that a relatively late diagenetic evolution of the U-Th system characterizes the recovered vivianite minerals. The authigenic U displays a very high excess in 234U (over 238U) with an activity ratio of 4.58±0.58 (±2σ). It suggests that it originates from the transfer of highly fractionated U from surrounding detrital minerals through very low U-content pore waters. © 2012 Elsevier Ltd.
1368.
Branched and isoprenoid tetraether (BIT) index traces water content along two marsh-soil transects surrounding Lake Qinghai: Implications for paleo-humidity variation
Organic Geochemistry,
5975 – 81
2013
ISSN: 01466380Keywords:▾
China; Qinghai; Qinghai Lake; Qinghai-Xizang Plateau; Aerobic bacteria; Glycerol; Lipids; Soil moisture; Wetlands; Aerobic ammonia oxidations; Chemolithoautotrophic; Lake Qinghai; Positive correlations; Qinghai-Tibetan plateau; Relative abundance; Soil water content; Upland soil; bacterium; biomarker; humidity; isoprenoid; loess; marsh; open ocean; paleolimnology; peat soil; relative abundance; shore (nonmarine); soil water; upland region; water content; Lakes
Abstract: ▾ The BIT index represents the relative abundances of branched glycerol dialkyl glycerol tetraethers (bGDGTs) and the isoprenoid GDGT, crenarchaeol. While bGDGTs are produced mainly by soil (anaerobic) bacteria, crenarchaeol is known to be a biomarker for aerobic ammonia oxidation by chemolithoautotrophic Thaumarchaeota, particularly in the open ocean or lakes. Thus, the index in marine and lacustrine settings has been widely used as a proxy for soil input. Here, we have investigated GDGT distribution along two transects extending from the lake shore marsh to upland soils on the NE Qinghai-Tibetan plateau. The results show that soil water content (SWC) correlates positively with concentration of bGDGTs and negatively with concentration of crenarchaeol; consequently, there is a significant positive correlation between SWC and the BIT index. Our study highlights a new potential application of BIT as a humidity proxy in loess/soil and peat deposits. © 2013 Elsevier Ltd.
1367.
Carbon isotopic composition of isoprenoid tetraether in surface sediments of Lake Qinghai and surrounding soils
Organic Geochemistry,
6054 – 61
2013
ISSN: 01466380Keywords:▾
China; Qinghai; Qinghai Lake; Isotopes; Lakes; Lipids; Microorganisms; Organic carbon; Sedimentology; Soils; Surficial sediments; Carbon assimilation; Carbon isotopic composition; Depositional environment; Dissolved inorganic carbon; Isotopic fractionations; Lacustrine systems; Sensitive indicator; Total Organic Carbon; biomarker; biomass; carbon isotope; depositional environment; eukaryote; isoprenoid; isotopic composition; lacustrine deposit; sediment pollution; soil pollution; Carbon
Abstract: ▾ Isoprenoid GDGTs (iGDGTs), along with their constituent biphytanyl moieties, are biomarkers for archaea. In order to obtain more information on identifying the carbon source and potential carbon assimilation pathway of archaea in surface sediments of Lake Qinghai and the surrounding soils, the stable carbon isotopic composition of iGDGT-derived biphytanes as well as its relationship with δ13C values of total organic carbon (TOC) and dissolved inorganic carbon (DIC) was investigated. The δ13C values of iGDGT-derived biphytanes ranged from -42.7‰ to -20.3‰. For example, the values for acyclic biphytanes (BP-0), the most abundant, varied from -25.0‰ to -22.1‰ in offshore sediments, -30.5‰ to -25.4‰ in surrounding soils and -42.7‰ to -32.0‰ in nearshore sediments. The wider variation than that of δ13CTOC (-26.9‰ to -25.1‰) in offshore sediments and that in surrounding soils indicated that δ13C values of BP-0 may be a sensitive indicator for examining the depositional environments between terrestrial and lacustrine systems. With average δ13C values of -23.6‰, crenarchaeol-derived biphytanes (BP-cren) in offshore sediments were enriched in 13C (ca. 3.6‰) relative to TOC. In addition, the carbon isotopic fractionation between BP-cren and DIC was -21.3‰, consistent with that reported for marine Thaumarchaeota. The enrichment in 13C relative to TOC and the similar carbon isotopic fractionation indicated that Thaumarchaeota in offshore sediments of Qinghai Lake are autotrophic. With average δ13C values of -29.2‰, BP-cren in surrounding soils was depleted by 0.9‰ to 12.8‰ in 13C relative to DIC. The quite large scatter in carbon isotopic fractionation between BP-cren and DIC indicated that the biomass of soil Thaumarchaeota originated from inorganic and organic carbon sources, suggesting a mixotrophic lifestyle. © 2013 Elsevier Ltd.
1366.
Dynamic diatom response to changing climate 0-1.2Ma at Lake El'gygytgyn, Far East Russian Arctic
Climate of the Past,
9
(3)
1309-1319
2013
ISSN: 18149324Keywords:▾
climate variation; diatom; dominance; interglacial; nutrient cycling; paleoclimate; paleoenvironment; physiological response; primary production; regional climate; species diversity, Chukchi; Elgygytgyn Lake; Russian Federation
Abstract: ▾ The Lake El'gygytgyn sediment record contains an abundant diatom flora through most intervals of the lake's history, providing a means to create and test hypotheses concerning the lake's response to changing climates. The 0-1.2 Ma core interval is characterized by shifts in the dominant planktonic genera and events of exceptional concentration and diversity. Warm interglacial intervals have enhanced concentration and diversity of the plankton. This response is most extreme during exceptional events corresponding to marine isotope stages (MIS) 11 and 31. Diatom concentration and diversity also increase during some cold intervals (e.g., MIS 2), suggesting conditions of lake circulation and nutrient cycling promoting diatom production during these events. Short intervals of low plankton concentration accompanied by shifts in the dominant genus of the lake suggest conditions during certain cold events generate a severe impact on plankton production. The absence of these events during extended intervals of low summer insolation variability suggests a muted cold-event response of the lake system linked to regional climate. © Author(s) 2013.
1365.
Can alteration experiments on impact melts from El'gygytgyn and volcanic glasses shed new light on the formation of the Martian surface?
Meteoritics and Planetary Science,
48
(7)
1287-1295
2013
ISSN: 10869379Abstract: ▾ This investigation involved three specimens: an altered felsic sample of impactite from the ICDP El'gygytgyn drill core D1c, and two reference volcanics from Iceland, namely a rhyolitic glass and a basaltic glass. The goal of this work was to better understand the alteration of impact melt and volcanic glass, and to apply the results to an investigation of alteration processes below the surface of Mars. Hydrothermal batch alteration experiments with the El'gygytgyn sample showed formation of various silica phases such as cristobalite, opal, and quartz. According to geochemical modeling, zeolites were also expected, but zeolite minerals already present in the impactite prior to the experiment may have masked possible experimental zeolite growth. Basaltic glass was altered to smectite, talc, and opal. The accompanying numerical modeling gave results that were similar or comparable to the laboratory experiments. Rhyolitic glass was kinetically more stable than basaltic glass, and showed only minor formation of calcite and feldspar during the 3-week experiment. The study showed that closed-system isochemical alteration of both siliceous and mafic glasses and melts results in the formation of smectites and zeolites. Therefore, to link alteration features on Mars to specific physical conditions, the exact identity of the mineral phases present in surface rocks must be known. Moreover, our simulations on closed-system isochemical alteration showed that the fraction of zeolites and silica formed relative to smectite depends on the source mineral altered. Therefore, fractions of these mineral groups present in the Martian soil may be used to better predict source rock characteristics. © The Meteoritical Society, 2013.
1364.
Earth's earliest global glaciation? Carbonate geochemistry and geochronology of the Polisarka Sedimentary Formation, Kola Peninsula, Russia
Precambrian Research,
235278--294
2013
ISSN: 03019268
Publisher: Elsevier
Keywords:▾
aragonite; carbon isotope; carbonate rock; deposition; diamictite; dolostone; geochemistry; geochronology; glaciation; inorganic carbon; methane; outcrop; oxidation; Proterozoic; sedimentology; tuff; volcanic ash, Kola Peninsula; Murmansk [Russian Federation]; Russian Federation
Abstract: ▾ As part of the International Continental Scientific Drilling Program's Fennoscandian Arctic Russia-Drilling Early Earth Project (ICDP FAR-DEEP), Palaeoproterozoic diamictic and associated rocks were targeted and recovered in Hole 3A on the Kola Peninsula of NW Russia. In addition to the diamictites, carbonate sedimentary rocks and volcanic ash layers (all metamorphosed to greenschist grade) were encountered. Sedimentology and geochemistry suggest deposition of the diamictites in an open-marine aragonite-precipitating environment. Sampling of the core and of outcrops from the same geographical area yielded a number of zircons for analyses, the majority of which were inherited. However a tuff at 20.01m core depth yielded zircons dated at 2434±1.2Ma (±6.6Myr including decay constant uncertainties) that we interpret as a magmatic age. These data, combined with dates from underlying intrusions, indicate deposition of the Polisarka Sedimentary Formation diamictites and underlying carbonates during an interval of time from ca. 2430 to 2440Ma. The carbonate rocks, which likely originally included aragonitic limestones, were deposited mostly in a deep-water setting (i.e. at least below storm wave base) and occur below the diamictite. They record two inorganic carbon δ13C excursions, from values of ca. 0‰ to minima of ca. -5.4‰, as the contact with the overlying diamictite is approached. The older (stratigraphically lower) excursion occurs about 9m below the base of the diamictic units and the younger one at 1m below. Throughout that interval, Mg/Ca ratios correlate strongly with δ13C (n=38, r=0.85), and combined with petrographic observations, this indicates that the first (stratigraphically lower) excursion was modified by secondary alteration and the second is recorded in resedimented dolostone clasts. It is tempting to speculate that these dolostone clasts were deposited in penecontemporaneous shallow-marine waters, and that their low δ13C values might reflect input of oxidised atmospheric methane to the ocean surface (and therefore the cause of the glaciation); the dolostones were subsequently resedimented into the deeper marine settings. However this must be left as a hypothesis to be tested when further age-constrained contemporaneous pre-glacial carbonate sections are found. © 2013 Elsevier B.V.
1363.
Lithology, radiocarbon chronology and sedimentological interpretation of the lacustrine record from Laguna Potrok Aike, southern Patagonia
Quaternary Science Reviews,
7154 – 69
2013
Keywords:▾
Argentina; Laguna Potrok Aike; Patagonia; Santa Cruz [Argentina]; Deposits; Geomagnetism; Salinity measurement; Sedimentology; Sediments; Argentina; Holocenes; ICDP-project PASADO; Lake level fluctuations; Late Pleistocene; Mass movement; Mixed-effect regression; Patagonia; climate variation; data set; geochronology; glacial environment; Holocene; lacustrine deposit; Last Glacial; lithology; mass movement; numerical model; radiocarbon dating; sedimentation; tephrochronology; Lithology
Abstract: ▾ The 106m long composite profile from site 2 of ICDP expedition 5022 (PASADO) at Laguna Potrok Aike documents a distinct change in sedimentation patterns from pelagic sediments at the top to dominating mass movement deposits at its base. The main lithological units correspond to the Holocene, to the Lateglacial and to the last glacial period and can be interpreted as the result of distinct environmental variations. Overflow conditions might have been achieved during the last glacial period, while signs of desiccation are absent in the studied sediment record. Altogether, 58 radiocarbon dates were used to establish a consistent age-depth model by applying the mixed-effect regression procedure which results in a basal age of 51.2cal.kaBP. Radiocarbon dates show a considerable increase in scatter with depth which is related to the high amount of reworking. Validation of the obtained chronology was achieved with geomagnetic relative paleointensity data and tephra correlation. © 2012 Elsevier Ltd.
1362.
Insights into early Earth from Barberton komatiites: Evidence from lithophile isotope and trace element systematics
Geochimica et Cosmochimica Acta,
10863 – 90
2013
1361.
Interactions between rhyolitic and basaltic melts unraveled by chaotic mixing experiments
Chemical Geology,
346119-212
2013
ISSN: 00092541Keywords:▾
Chemical diffusion; Chemical gradients; Element mobility; Hybrid melts; Major and trace elements; Methodological approach; Mixing experiments; Snake river plains, Chemical analysis; Diffusion in solids; Experiments; Silicates, Mixing, basalt; concentration (composition); diffusion; experimental study; fluid dynamics; mixing; mobility; physicochemical property; rhyolite; silicate melt, Idaho; Snake River Plain; United States
Abstract: ▾ Magma mixing may operate at any stage in the evolution of a magmatic system. The development of mixing is strongly controlled by fluid dynamics and its understanding requires a comprehensive physico-chemical approach in order to identify and interpret its occurrence in nature. Here, we experimentally study the physical and chemical interplays during the mixing of basaltic and rhyolitic natural melts from the Snake River Plains, USA. In particular, we present the results of the first high-temperature mixing experiments performed under controlled chaotic dynamic conditions, providing a new methodological approach to constrain the complexities of the mixing process between natural silicate melts.The mixing process is initially governed by the dynamics of stretching and folding of the melts, producing alternating flow bands. These bands increase the contact area between the end-members, which subsequently enhance chemical exchanges and thus contribute to the generation of regions with variable degrees of hybridization. We quantified the mobility of major and trace elements across contact areas, and analyzed the concentration variance decay induced by chemical diffusion. The analysis shows that elements diffuse with different efficiencies as the chemical gradient evolves and therefore, the achievement of hybrid compositions contrasts between elements. The approach introduced in this study can, in principle, be applied to mixing trends observed in nature in order to estimate the time-scales and degree of magma mixing evidenced across volcanic rocks/deposits. © 2012 Elsevier B.V.
1360.
Isotopic systematics of the early Mauna Kea shield phase and insight into the deep mantle beneath the Pacific Ocean
Geochemistry, Geophysics, Geosystems,
14
(3)
659 – 676
2013
ISSN: 15252027
Publisher: Blackwell Publishing Ltd
Keywords:▾
Hawaii [(ISL) Hawaiian Islands]; Hawaii [United States]; Hawaiian Islands; Mauna Kea; Pacific Ocean; United States; Basalt; Core samples; Lead; Silicates; Strontium; Thermal plumes; Volcanoes; HSDP2; Mantle heterogeneity; Mantle plume; Mauna keas; Ocean island basalts; Pb-Sr-Nd isotope systematics; isotopic composition; mantle chemistry; mantle plume; mantle source; Ocean Drilling Program; ocean island basalt; volcanism; Isotopes
Abstract: ▾ The 3500 m deep Hawai'i Scientific Drilling Project core provides a ~680 kyr record of the magmatic history and source components of Mauna Kea volcano. We report high-precision Pb-Sr-Nd isotopic compositions of 40 basalts from the last 408 m of the final drilling phase (HSDP2-B and HSDP2-C) and show that these lowermost basalts represent the early shield stage of Mauna Kea's growth history. Two sample groups are distinguished based on their isotopic variability compared to the rest of the core. Over a depth interval of 210 m (3098.2-3308.2 mbsl), the basalts show very restricted isotopic variation and represent sampling of a relatively homogeneous source. Samples from the bottom 192 m record the largest range of 206Pb/204Pb and 208Pb/204Pb in the core, reflecting the greater isotopic variability of the earlier stages of volcanism compared to subsequent stages. The heterogeneity of Mauna Kea lavas is explained by mixing variable proportions of four distinct components intrinsic to the Hawaiian mantle plume. One of these components, Kea, is a prevalent and long-lived composition within the Hawaiian plume, whereas the other three components are involved at different stages of the volcano's history and contribute to the short-term isotopic variability of Mauna Kea. The compositional similarity of the Kea component to "C" and to the super-chondritic bulk-silicate Earth suggests that Kea may be part of the primitive mantle of a non-chondritic Earth. Other Pacific oceanic island basalts share Kea-like compositions, indicating that the Kea component is a common, widespread composition within the Pacific deep mantle. ©2013. American Geophysical Union. All Rights Reserved.
1359.
Kolosjoki Sedimentary Formation: A record in the aftermath of the Paleoproterozoic global positive $\delta$13C excursion in sedimentary carbonates
Chemical Geology,
362165--180
2013
1358.
Kolosjoki Sedimentary Formation: A record in the aftermath of the Paleoproterozoic global positive δ13C excursion in sedimentary carbonates
Chemical Geology,
362165 – 180
2013
1357.
Late Cretaceous (Campanian) provenance change in the Songliao Basin, NE China: Evidence from detrital zircon U-Pb ages from the Yaojia and Nenjiang Formations
Palaeogeography, Palaeoclimatology, Palaeoecology,
38583-94
2013
ISSN: 00310182Keywords:▾
Campanian; detrital deposit; provenance; seismic stratigraphy; tectonic evolution; unconformity; uranium-lead dating; zircon, China; Da Hinggan Mountains; Heilongjiang; Nen Basin; Songliao Basin; Xiao Hinggan Mountains, Coniacian
Abstract: ▾ In order to define the provenance change across the nonconformable boundary between the second and the third members of the Upper Cretaceous Nenjiang Formation (Campanian) in the north-central area of the Songliao Basin, two sandstone samples above (sample a-1 from the fourth member of the Nenjiang) and below (sample z-1 from the first member of the Yaojia Formation) the nonconformity were collected from core holes. U-Pb dating was performed on detrital zircons separated from the three sandstone samples. Detrital zircons from sample a-1 have dominant age populations of 100-110. Ma, 190-220. Ma, and ~. 1800. Ma, and sample z-1 has dominant ages of 130-150. Ma and ~. 350. Ma. This paper demonstrates that the provenance of the fourth member of the Nenjiang Formation is significantly different from the first member of the Coniacian Yaojia Formation. The provenance above the nonconformity became much more complex and the eastern source increased significantly, while the western source sharply declined. The main source areas of the fourth member of the Nenjiang Formation are mainly the Zhangguangcai Range, the eastern Lesser Xiang'an Range and the southeast of Songliao Basin. The dominant provenance of the first member of the Yaojia Formation is the northern, the central and the southern Great Xing'an Range. According to the depositional ages and combining the latest seismic stratigraphic profiles in the Songliao Basin, the tectonic inversion of the eastern Songliao Basin began between 73. Ma and 87. Ma, which differs from the previous age of 73. Ma. © 2012 Elsevier B.V.
1356.
Late Cretaceous climate changes recorded in Eastern Asian lacustrine deposits and North American Epieric sea strata
Earth-Science Reviews,
126275-299
2013
ISSN: 00128252Keywords:▾
Albian; carbon sink; Cenomanian; climate variation; Cretaceous; deposition; eccentricity; global climate; greenhouse effect; lacustrine deposit; Maastrichtian; organic carbon; oxygen isotope; paleoclimate; runoff; sediment core; stratabound deposit; stratigraphy; Turonian; water level, China; Songliao Basin
Abstract: ▾ Cretaceous climate data of the long-lived Cretaceous Songliao Basin (SB) in eastern Asia is correlated and compared with the Western Interior Seaway (WIS) on the northern American plate, in order to understand better the dynamics of the Earth's past 'greenhouse' climates. Nearly continuous Late Cretaceous terrestrial deposition in the Songliao Basin is represented by two cores totaling 2431m in length. The Turonian-Maastrichtian age of the section is based on integrated stratigraphy, and is comparable in age with Upper Cretaceous strata in the WIS. Being consistent with global trends, the dynamic Late Cretaceous climates of both the SB and WIS gradually cooled from the warmest Albian-Cenomanian time to the end of the Maastrichtian with several intervening warm periods as did the global climate. However regional differences existed, the Songliao Basin climate was humid to semi-humid, warm temperate-subtropical and the Western Interior Seaway was in the humid, warm temperate zone and experienced only moderate climatic changes. The shifts of oxygen isotope data in the Songliao Basin were frequent and abrupt, whereas WIS records more gradual change affected mainly by fresh-water runoff mixing with southern Tethyan and northern Arctic waters. Sedimentary cycles of eccentricity, obliquity and precession bands are recorded in both the SB and WIS basins. The sedimentary cycles in the WIS and SB are interpreted to be related to variations of the wet/dry runoff cycles, which indicate that orbital forcing played an important role in global climate change in Late Cretaceous. The most favorable condition for organic carbon burial in both the SB and WIS basin was bottom water anoxia regardless of the cause of the anoxia. But the organic carbon burial rate was usually much higher in the Songliao Lake than in the WI epeiric sea suggesting that giant lakes may serve as important sinks of atmospheric CO2. In both basins organic-rich deposits formed during a rise in water level and incursion of saline waters. The integration of paleoclimate data from Cretaceous marine deposits and terrestrial sedimentary record will promote our understanding of the Cretaceous 'greenhouse' climate change and may provide insights for a future greenhouse world. © 2013 Elsevier B.V.
1355.
Late Cretaceous stratigraphy, Songliao Basin, NE China: SK1 cores
Palaeogeography, Palaeoclimatology, Palaeoecology,
38531-43
2013
ISSN: 00310182Keywords:▾
biostratigraphy; biozonation; Campanian; charophyte; chronostratigraphy; Coniacian; core analysis; Cretaceous-Tertiary boundary; foraminifera; gas production; hydrocarbon reserve; hydrocarbon reservoir; lacustrine deposit; Maastrichtian; magnetostratigraphy; marine environment; microfossil; micropaleontology; mudstone; oil production; oil shale; ostracod; palynology; phytoplankton; sandstone; Santonian; stratigraphic correlation; timescale; Turonian; uranium-lead dating, China; Songliao Basin, Charales; Coniacian; Foraminifera; Ostracoda
Abstract: ▾ The Songliao Basin is the largest Cretaceous oil and gas-producing lacustrine basin in China, with its greatest aerial extent in the middle Cretaceous. A coring program (SK1) has to date yielded 2485.89m of continuous core (96.46% recovery) and provides significant material for Cretaceous research. The sequence of the core consists mainly of lacustrine sandstone, dark grey mudstone, shale and oil-shale. The Upper Cretaceous stratigraphic section has been subdivided into the Quantou, Qingshankou, Yaojia, Nenjiang, Sifangtai and Mingshui formations in ascending order. Late Cretaceous microfossils are diverse and abundant. A detailed biostratigraphic study has subdivided the sequence into high precision biozones: 21 ostracode assemblages, 10 phytoplankton assemblages, 7 palynological zones and 4 charophyta assemblages, respectively. In addition, marine foraminifera were first discovered from the basin. Three 206Pb/238U ages and one 40Ar/39Ar age were analysed. Ten local magnetozones have been recognised in the SK1 (North), and two magnetozones have been indicated in the SK1 (South). Based on biostratigraphy, high-resolution magnetostratigraphy and SIMS U-Pb zircon analyses, the SK1 stratigraphy is correlated with Upper Cretaceous stages in the International Geologic Time Scale. The upper part of the Quantou Formation is the lower Turonian; the Qingshankou Formation is the upper Turonian-lower Coniacian; the Yaojia Formation is from the upper Coniacian to middle Santonian; the Nenjiang Formation is the upper Santonian to middle Campanian; the Sifangtai Formation is limited to the upper Campanian; and the Mingshui Formation is the uppermost Campanian to Maastrichtian. It is likely that the upper part of the Mingshui Formation belongs to the Paleocene, and the K/Pg boundary is within the Member 2 of the Mingshui Formation around the depth of 328m by new micropalaeontologic and magnetostratigraphic data. © 2012 Elsevier B.V.
1354.
Late Cretaceous--early Paleogene charophytes from Songliao Basin, North China: SK1 (N) Core
Acta Micropalaeontologica Sinica,
30
(1)
1-16
2013
1353.
Lithostratigraphy of the impactite and bedrock section of ICDP drill core D1c from the El'gygytgyn impact crater, Russia
Meteoritics and Planetary Science,
48
(7)
1143-1159
2013
ISSN: 10869379Abstract: ▾ In 2008/2009, the International Continental Scientific Drilling Program (ICDP) obtained drill cores from the El'gygytgyn impact structure located on the Chukotka Peninsula (Russia). These cores provide the most complete geological section ever obtained from an impact structure in siliceous volcanic rock. The lithostratigraphy comprises a thick sequence of lacustrine sediments overlying impact breccias and deformed target rock. The interval from 316 m (below lake floor-blf) to the end of the core at 517 m depth can be subdivided into four lithological sequences. At 316 m depth, the first mesoscopic clasts of shocked target rock occur in lacustrine sediments. The growing abundance of target rock clasts with increasing depth and corresponding decrease of lacustrine sediment components indicate the extent of this transition zone to 328 m depth. It constitutes a zone of mixed reworked impact breccia and lacustrine sediments. Volcanic clasts in this reworked suevite section show all stages of shock metamorphism, up to melting. The underlying unit (328-390 m depth) represents a suevite package, a polymict impact breccia, with considerable evidence of shock deformation in a wide variety of volcanic clasts. This includes fragments with quartz that exhibit planar fractures and planar deformation features (PDF). In addition, at three depths, several centimeter-sized clasts with shatter cones were detected. Due to microanalytical identification of relatively rare, microscopic impact melt particles in the matrix of this breccia, this material can be confidently labeled a suevite. Also in this sequence, three unshocked, <1 m thick intersections of volcanic blocks occur at 333.83, 351.52, and 383.00 m depths. The upper bedrock unit begins at 390.74 m depth, has a thickness of 30.15 m, and represents a sequence of different volcanic rocks-an upper part with basaltic composition from 390.74 to 391.79 m depth overlying a lower, rhyodacitic part from 391.79 to 420.27 m depth. This (parautochthonous) basement unit is only very weakly affected by the impact: only one shocked quartz grain with two sets of PDF was recorded at 391.33 m depth. The lower bedrock unit (420.89-517.09 m depth [end of core]) is a brittly deformed, rather homogeneous welded ignimbrite that in part can be considered a cataclasite. The top three meters of this section are sheared, which could represent pre-impact tectonic deformation. A 54 cm thick injection of polymict impact breccia occurs at 471.42-471.96 m depth. © The Meteoritical Society, 2013.
1352.
Impact of volcanism on the evolution of Lake Van II: Temporal evolution of explosive volcanism of Nemrut Volcano (eastern Anatolia) during the past ca. 0.4Ma
Journal of Volcanology and Geothermal Research,
25315-34
2013
ISSN: 03770273
Publisher: Elsevier B.V.
Keywords:▾
Alkalinity; Climate change; Deposits; Erosion; Explosives; Fallout; Feldspar; Feldspar deposits; Lakes; Melting; Reservoirs (water); Single crystals; Stratigraphy; Submarine geophysics; Trace elements; Unloading, Chemical compositions; Compositional characteristics; Compositional evolution; Compositional zoning; East Anatolian Tephra Province; Explosive volcanism; Lake vans; Trace element concentrations, Volcanoes, argon-argon dating; explosive volcanism; ignimbrite; marine isotope stage; pyroclastic flow; temporal evolution; tephra; volcanic eruption, Bitlis; Lake Van; Nemrut; Turkey
Abstract: ▾ Thirty-two new single crystal ages document 400. 000. years of widespread explosive volcanism of historically active Nemrut Volcano towering over huge alkaline Lake Van (Eastern Anatolia). The dated deposits were selected to monitor the volcanic and compositional evolution of Nemrut Volcano through time and thus to provide a rigorous temporal framework for the tephra record of the PaleoVan Drilling Project. Tephra samples were taken from large-volume deposits or those that occur in medial to distal localities, well-exposed stratigraphic sections or from the initial phase of an eruptive sequence. Mainly fallout deposits were chosen because most ignimbrites show more complex and corroded feldspar populations owing to compositional zoning and magma mixing. Moreover, fallout deposits held the promise to be more clearly identifiable with-and correlatable to->. 300 tephra layers in the PaleoVan drill cores, even though commonly in amounts marginal or insufficient in thickness to allow well-supported single crystal dating. The crystals dated are dominantly anorthoclase, the main phenocryst phase in the trachytic to rhyolitic, slightly to strongly peralkaline Nemrut magmas. Ages obtained so far range from ca. 400. ka to ca. 30. ka for Nemrut Volcano. The causes of significant changes in the frequency, volume and composition of tephra layers per unit time are discussed in terms of external (erosion, climate changes, geodynamic factors) and internal forcing (changes in magma supply and composition and incubation periods preceding large volume rhyolitic eruptions). For example, the low frequency of tephra layers deposited prior to ca. 200. ka may be due to low explosive activity, severe erosion between MIS 9 and MIS 11, or both. Nevertheless, the overall frequency of explosive eruptions appears to have increased during the past ca. 200. ka. We also recognize a slight peak in explosive eruptions during warm periods (e.g. MIS 5 and MIS 7) and speculate on lithospheric unloading triggering increased partial melting or magma reservoir unloading following massive glacier melting. The ages of 5 dated ignimbrites span ca. 250. 000. years suggesting that Nemrut Volcano went through a polycyclic evolution with multiple caldera collapses and major pyroclastic flow eruptions, the oldest dated so far as 265. ka. The widely held view of the impressive Nemrut Caldera now dated to have formed at ca. 30. ka, as the main paroxysmal event during the evolution of the volcano is no longer tenable. Distinct and coherent compositional characteristics, especially in trace element concentrations, characterize several groups of trachytic tephras. We speculate that the growth of Nemrut Volcano caused the isolation of the Lake Van basin. On account of their mineralogical (anorthoclase, hedenbergite, fayalite, aenigmatite) and alkalic chemical compositions and large volume, dated Nemrut fallout tephras are likely to represent excellent markers in lakes and other sites of paleoclimatological or archeological interest in neighboring countries to the northeast of Lake Van as far as the Caspian Sea in what may be called the East Anatolian Tephra Province. © 2012 Elsevier B.V.
1351.
Luminescence dating of the PASADO core 5022-1D from Laguna Potrok Aike (Argentina) using IRSL signals from feldspar
Quaternary Science Reviews,
7170 – 80
2013
Keywords:▾
Argentina; Laguna Potrok Aike; Santa Cruz [Argentina]; Bleaching; Cleaning; Feldspar; Lakes; Quartz; Stratigraphy; ICDP-project PASADO; Independent age control; K-feldspar; Laguna potrok aike; Luminescence dating; Measurement protocol; Post-IR IRSL; Signal instabilities; bleaching; chronology; feldspar; luminescence dating; signal; volcanic ash; Luminescence
Abstract: ▾ We have measured and tested a luminescence chronology for the PASADO core 5022-1D from the maar lake of Laguna Potrok Aike. Because of unsuitable quartz OSL characteristics, sand-sized K-feldspar extracts were chosen as a dosimeter and the dose was measured using a post-IR IRSL (pIRIR290) measurement protocol. Using this approach we were able to access a stable signal and thus avoid the ubiquitous problem of feldspar signal instability. Extensive laboratory tests show that the chosen pIRIR290 protocol is applicable to these samples. We also developed a new criterion based on known relative bleaching rates of the conventional IRSL signal (IR50) and the pIRIR290 signal and the relationship between resulting equivalent doses; this is used to identify and reject poorly bleached samples. Eighteen samples out of 47 were rejected based on this criterion, without reference to absolute doses or stratigraphy; the resulting age-depth profile is self-consistent, increases smoothly with depth and is in agreement with independent age control based on volcanic ash layers (Reclús, Mt Burney and Hudson tephras) at the top and middle of the core. Our new luminescence chronology suggests that the 5022-1D core reaches back to ~65ka at ~96m below lake floor. © 2013 Elsevier Ltd.
1350.
Magnetopolarity zone and geological age of the Nenjiang Formation at the CCSD-SK-1 drill core in the Songliao Basin
Journal of Stratigraphy,
37
(2)
139-143
2013
1349.
Magnetostratigraphic determination of the age of ancient Lake Qinghai, and record of the East Asian monsoon since 4.63 Ma
Geology,
41
(8)
875 – 878
2013
ISSN: 19432682DOI:10.1130/G34418.1
Keywords:▾
China; Qinghai; Qinghai Lake; Qinghai-Xizang Plateau; Climate change; Geochronology; Lithology; Sediments; Tectonics; Depositional environment; East Asian monsoon; Global environmental change; High resolution; Long-term trend; Magnetostratigraphy; Mean-grain size; Tibetan Plateau; age determination; Cenozoic; chronology; climate variation; depositional environment; environmental change; grain size; lithofacies; lithology; loess; magnetostratigraphy; monsoon; paleoclimate; sediment core; Lakes
Abstract: ▾ Lake Qinghai, in North China, is the largest interior plateau lake in Central Asia, and is sensitive to climate change and the environmental effects of Tibetan Plateau uplift. We have obtained an almost continuous 626 m long sediment core from an in-filled part of the southern lake basin, which documents both the age of the origin of the lake and the evolution of the East Asian monsoon during the Late Cenozoic. High-resolution magnetostratigraphy provides a chronology back to ca. 5.1 Ma. Analysis of lithofacies and depositional environments reveal that the change from eolian to lacustrine facies occurred at ca. 4.63 Ma, corresponding to a shift from an arid or semi-arid to a more humid climate, which resulted in the origin of Lake Qinghai. Changes in sediment lithology and mean grain size indicate that the lake level fluctuated considerably, superimposed on a long-term trend from higher to lower levels in response to variations in the East Asian Monsoon. This archive is a significant additional source of information on regional and global environmental change, complementing the existing records from north China, which are mainly based on analysis of loess deposits. © 2013 Geological Society of America.
1348.
Magnitude, geomorphologic response and climate links of lake level oscillations at Laguna Potrok Aike, Patagonian steppe (Argentina)
Quaternary Science Reviews,
71131 – 146
2013
Keywords:▾
Argentina; Laguna Potrok Aike; Patagonia; Santa Cruz [Argentina]; Catchments; Curve fitting; Deposits; Glacial geology; Groundwater; Permafrost; Rain; Runoff; Salinity measurement; Sedimentary rocks; Soils; Glacial; Holocenes; ICDP-project PASADO; Lacustrine sediments; Lake level fluctuations; Regional water balance; Southern Hemispheric Westerlies; Surrounding soft rock; catchment; data set; geomorphology; groundwater; Last Glacial Maximum; Little Ice Age; luminescence; maar; magnitude; mass movement; Miocene; oscillation; permafrost; precipitation (climatology); semiarid region; Southern Hemisphere; steppe; tephrochronology; transgression; Lakes
Abstract: ▾ Laguna Potrok Aike is a large maar lake located in the semiarid steppe of southern Patagonia known for its Lateglacial and Holocene lake level fluctuations. Based on sedimentary, seismic and geomorphological evidences, the lake level curve is updated and extended into the Last Glacial period and the geomorphological development of the lake basin and its catchment area is interpreted.Abrasion and lake level oscillations since at least ~50ka caused concentric erosion of the surrounding soft rocks of the Miocene Santa Cruz Formation and expanded the basin diameter by approximately 1km. A high lake level and overflow conditions of the lake were dated by luminescence methods and tephra correlation to the early Lateglacial as well as to ~45ka. The lowest lake level of record occurred during the mid-Holocene. A further lake level drop was probably prevented by groundwater supply. This low lake level eroded a distinct terrace into lacustrine sediments. Collapse of these terraces probably caused mass movement deposits in the profundal zone of the lake. After the mid-Holocene lake level low stand a general and successive transgression occurred until the Little Ice Age maximum; i.e. ca 40m above the local groundwater table. Frequent lake level oscillations caused deflation of emerged terraces only along the eastern shoreline due to prevailing westerly winds. Preservation of eolian deposits might be linked to relatively moist climate conditions during the past 2.5ka.Precisely dated lake level reconstructions in the rain-shadow of the Andes document high Last Glacial and low Holocene lake levels that could suggest increased precipitation during the Last Glacial period. As permafrost in semiarid Patagonia is documented and dated to the Last Glacial period we argue that the frozen ground might have increased surficial runoff from the catchment and thus influenced the water balance of the lake. This is important for investigating the glacial to Holocene latitudinal shift and/or strengthening of the Southern Hemispheric Westerlies by using lake level reconstructions as a means to assess the regional water balance. Our interpretation explains the contradiction with investigations based on pollen data indicating drier climatic conditions for the Last Glacial period. © 2012 Elsevier Ltd.
1347.
Marine incursion events in the Late Cretaceous Songliao Basin: Constraints from sulfur geochemistry records
Palaeogeography, Palaeoclimatology, Palaeoecology,
385152-161
2013
ISSN: 00310182Keywords:▾
Cretaceous; geochemistry; lake level; oil field; organic carbon; paleolimnology; paleontology; source rock; sulfate; sulfur isotope, China; Nen Basin; Songliao Basin
Abstract: ▾ Songliao Basin in NE China developed the most productive oilfield in the world sourced from terrestrial rocks. The main source rock of the basin includes member 1 of the Qingshankou (K2qn1) and members 1 and 2 of the Nenjiang Formation (K2nj1-2). However the exact reasons for the formation of the source rock, especially the K2qn1 are still controversial. Former paleontological and organic geochemical research suggested that organic matter was deposited during marine incursion events of K2qn1 but further geochemical evidence is needed. This paper explores the distinct sulfate levels that distinguish marine from fresh waters of the Songliao paleo-lake. We undertook a systematic investigation the sulfur geochemistry of the sediments from top of member 4 of the Quantou Formation (K1q4) to top of member 1 of the Qingshankou (K2qn1). The ratio of organic carbon to the pyrite sulfur (TOC/PYS) proved the previously suggested saline conditions during the deposition of K2qn1; and the pyrite sulfur isotope indicated that marine incursion may not only have occurred for K2qn1, but also for top of K1q4. The exact time for the beginning of marine incursion is to be determined. The marine incursion within K2qn1 is not strong and partially controlled by the fluctuation of paleo-lake level. The present study will be helpful for understanding the contribution of marine incursion events to the burial of organic carbon in the Songliao paleo-lake, although further studies are still needed. © 2013 Elsevier B.V.
1346.
Mass movement deposits in the 3.6 Ma sediment record of Lake El'gygytgyn, Far East Russian Arctic
Climate of the Past,
9
(4)
1949-1967
2013
ISSN: 18149324Keywords:▾
debris flow; depositional environment; facies; lacustrine deposit; mass movement; Pliocene; Quaternary; slope failure; turbidite; turbidity, Arctic; Chukchi; Elgygytgyn Lake; Russian Federation
Abstract: ▾ This paper focuses on the characterization and genesis of mass movement deposits (MMDs) in the Quaternary and Pliocene sediments of Lake El'gygytgyn, Far East Russian Arctic. Three partly overlapping holes were drilled into the 320 m long sediment record at International Continental Scientific Drilling Program (ICDP) Site 5011-1 in the lake basin, recovering the Quaternary almost completely, and the Pliocene down to 3.6 Ma with 52% recovery. Mass movement deposits were investigated in all three cores, based on macroscopical core descriptions, radiographic images, high-resolution magnetic susceptibility and gamma-ray density. Five different types of MMDs were identified: turbidites, grain-flow deposits, debrites, slumps and slides. These are formed by transitional mass movement processes, and thus can be co-generic. An initial slope failure is thought to transform into a debris flow that deforms frontal sediments, partly disintegrates and dilutes into a turbidity flow. Turbidites are by far the most frequent MMD type in the lake center. They occur throughout the record in all pelagic sedimentary facies, but they are thinner in facies formed during cold climate conditions. All other MMDs, by contrast, incise exclusively the pelagic facies deposited during warm climates. In the 123 m thick Quaternary composite sediment record 230 mass movement events are identified, comprising 33% of the sediment length. Turbidites contribute 93% of the number of Quaternary MMDs, but only 35% of their thickness. In the Pliocene sediments between 123 and 320 m, 181 additional mass movement deposits are identified, which constitute ∼33% of the recovered sediments. The mean recurrence interval for MMDs is 11 and 5 ka in the Quaternary and Pliocene, respectively. © Author(s) 2013.
1345.
Mechanisms of lake-level change at Laguna Potrok Aike (Argentina) - insights from hydrological balance calculations
Quaternary Science Reviews,
7127 – 45
2013
Keywords:▾
Argentina; Laguna Potrok Aike; Santa Cruz [Argentina]; Atmospheric pressure; Carbonation; Catchments; Climatology; Digital storage; Groundwater; Lasers; Monitoring; Runoff; Sediment traps; Sedimentology; Authigenic carbonates; Carbonate precipitation; Coupled general circulation models; ICDP-project PASADO; Meteorological parameters; Southern Hemisphere; Southern hemisphere annular modes; Southern south america; carbonate; energy budget; environmental monitoring; evaporation; general circulation model; hydrochemistry; hydrological change; lacustrine environment; mathematical analysis; permafrost; precipitation (chemistry); sediment chemistry; sediment trap; Southern Hemisphere; timescale; volume; wind velocity; Lakes
Abstract: ▾ Laguna Potrok Aike is an exceptional site in the southern hemisphere's mid-latitudes because it records changes in the hydrological regime through lake-level variations in a continuous, high-resolution sediment record back into the late Pleistocene. In this study, driving forces of lake-level changes at Laguna Potrok Aike are evaluated by means of process studies using data from an extensive multi-year monitoring in and around the lake. Lake-volume changes were calculated with an energy-budget/bulk-transfer approach and translated into lake-level variations, which were then compared to pressure sensor data. Calculated lake levels are in broad agreement with measured data. We hypothesize that on short time scales, lake-level fluctuations are mainly driven by the precipitation-to-evaporation ratio. Apart from changing catchment conditions, relative humidity, precipitation, temperature, wind strength and wind direction have the most important influence on the hydrological balance of the lake. Lake level decreases during periods of persistently high wind speeds from westerly directions, whereas, during periods with more frequent occurrences of easterly winds, it increases. These situations are linked to a strengthening of the Southern Hemispheric Westerlies in the first and more frequent blocking situations in the latter case. Although lake-level changes at Laguna Potrok Aike show some degree of similarity to variations of the El Niño Southern Oscillation (ENSO) and the Southern Hemisphere Annular Mode (SAM), a persistent correspondence remains to be documented.Water chemistry and sediment-trap data suggest that lake-internal carbonate precipitation is highly sensitive to short-term changes in the lake water volume and, thus, to lake-level variations. However, it becomes obvious that the sedimentary carbonate record, representing changes on longer time scales, is not linearly linked to lake-level changes, hence complicating quantitative lake-level reconstructions back in time. We suggest that short-term changes in authigenic carbonate production are mainly driven by changing precipitation/evaporation ratios probably superimposed on longer-term changes in groundwater input that represent a buffered climate signal.Scenario calculations for a period of 60 years show that changes of the controlling meteorological parameters in the range of 15-17% can lead to lake-level changes with a magnitude comparable to the reconstructed Holocene and Lateglacial extreme situations. In addition, modifications in the water-retaining capacity of the lake can also produce large lake-level changes. It is hypothesized that the development or disappearance of permafrost in the catchment of Laguna Potrok Aike during the Last Glacial/Interglacial transition may have changed the water-retaining capacity tremendously. The lake-level reconstructions for Laguna Potrok Aike might express some of the meridional climate variability observed in coupled general circulation model (CGCM) simulations for southern South America for the Last Glacial Maximum (LGM) and the mid Holocene. © 2012 Elsevier Ltd.