All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
1419.
The 14 April 2012 Koyna Earthquake of Mw 4.8: Insights into active tectonics of the Koyna region
Journal of Seismology,
17
(4)
1345-1353
2013
ISSN: 13834649Keywords:▾
active fault; aftershock; earthquake event; fault zone; focal mechanism; moment tensor; reservoir-induced seismicity; seismotectonics, India; Koyna; Maharashtra; Warna
Abstract: ▾ The 14 April 2012 earthquake of Mw 4.8 is the best monitored event in the Koyna region, a globally significant site of reservoir triggered seismicity in western India. Hence, investigation of this event assumes great importance, also considering its epicentral location close to that of the 1967 Koyna earthquake of M 6.3, the world's largest reservoir triggered earthquake. Inversion of P-wave amplitude data along with the first motion polarities at 30 digital seismic stations provides a well-constrained strike-slip type focal mechanism solution, similar to that of the 1967 earthquake. The mechanism is further confirmed by moment tensor inversion of 3-component waveform data recorded at the three nearest broadband stations. The depth distribution of the aftershocks clearly delineates a NNE-SSW trending fault plane dipping about 78° to the WNW and coinciding with the trend of the Donachiwada fault, as well as the left-lateral fault plane of the focal mechanism solution obtained. The precise location, focal mechanism and the seismicity distribution from our dense network indicate that the activity in the Koyna region is mainly controlled by the NNE-SSW trending Donachiwada (D) fault zone rather than the Koyna River Fault Zone (KRFZ) on the west as suggested previously. © 2013 Springer Science+Business Media Dordrecht.
1418.
The exploratory study of the colorimetry index reflect the paleoclimate—As the Late Cretaceous Turonian of the Songliao Basin for example (in Chinese with English abstract);[色度学指标反映古气候的探索研究——以松辽盆地晚白垩世土伦阶(Turonian)为例]
Jilin Geology,
32
(04)
1-6
2013
1417.
The last Glacial-Interglacial transition in Patagonia, Argentina: The stable isotope record of bulk sedimentary organic matter from Laguna Potrok Aike
Quaternary Science Reviews,
71205 – 218
2013
Keywords:▾
Argentina; Laguna Potrok Aike; Patagonia; Santa Cruz [Argentina]; Biogeochemistry; Biological materials; Cluster analysis; Isotopes; Lakes; Nitrates; Nutrients; Organic compounds; Photosynthesis; Sedimentology; ICDP; Lake sediments; Last deglaciation; PASADO; Primary productivity; South America; Stable carbon and nitrogen isotopes; carbon isotope; cluster analysis; deglaciation; environmental conditions; glacial-interglacial cycle; growing season; Last Glacial Maximum; macrophyte; nitrogen isotope; organic matter; phytoplankton; primary production; proxy climate record; sediment chemistry; sediment core; stable isotope; Phytoplankton
Abstract: ▾ An investigation of stable isotope (δ13CTOC and δ15NTN) and elemental parameters (TOC, TN contents and TOC/TN ratios) of bulk organic matter (<200μm) from sediment cores recovered from the Patagonian lake Laguna Potrok Aike (Argentina) in the framework of the ICDP deep drilling project PASADO provided insights into past changes in lake primary productivity and environmental conditions in South Patagonia throughout the last Glacial-Interglacial transition. Stratigraphically constrained cluster analyses of all proxy parameters suggest four main phases. From ca 26,100 to 17,300cal.yearsBP, lacustrine phytoplankton was presumably the predominant organic matter source in an aquatic environment with low primary productivity rates. At around 17,300cal.years BP, abrupt and distinct shifts of isotopic and elemental values indicate that the lacustrine system underwent a rapid reorganization. Lake primary productivity (phytoplankton and aquatic macrophytes) shows higher levels albeit with large variations during most of the deglaciation until 13,000cal.yearsBP. The main causes for this development can be seen in improved growing conditions for primary producers because of deglacial warming in combination with expedient availability of nutrients and likely calm wind conditions. After 13,000cal.yearsBP, decreased δ13CTOC values, TOC, TN contents and TOC/TN ratios indicate that the lake approached a new state with reduced primary productivity probably induced by unfavourable growing conditions for primary producers like strengthened winds and reduced nutrient availability. The steady increase in δ15NTN values presumably suggests limitation of nitrate supply for growth of primary producers resulting from a nutrient shortage after the preceding phase with high productivity. Nitrate limitation and consequent decreased lacustrine primary productivity continued into the early Holocene (10,970-8400cal.yearsBP) as reflected by isotopic and elemental values. © 2012 Elsevier Ltd.
1416.
The motion decoupled delivery system: A new deployment system for downhole tools is tested at the New Jersey margin
Scientific Drilling
(15)
51-56
2013
ISSN: 18168957
Publisher: Copernicus GmbH
1415.
Three-dimensional magnetotelluric inversion in practice-the electrical conductivity structure of the San Andreas fault in central California
Geophysical Journal International,
195
(1)
130-147
2013
ISSN: 0956540XKeywords:▾
Continental margins: transforms; Crustal structure; Geomagnetic induction; Inverse theory; Magnetotelluric; North America, Data processing; Electric conductivity; Geomagnetism; Magnetotellurics; Recovery; Strike-slip faults; Structural geology; Tensors, Three dimensional, continental margin; crustal structure; data inversion; electrical conductivity; fault zone; geomagnetic field; magnetotelluric method; three-dimensional modeling, California; San Andreas; United States
Abstract: ▾ 3-D inversion techniques have become a widely used tool in magnetotelluric (MT) data interpretation. However, with real data sets, many of the controlling factors for the outcome of 3-D inversion are little explored, such as alignment of the coordinate system, handling and influence of data errors and model regularization. Here we present 3-D inversion results of 169 MT sites from the central San Andreas Fault in California. Previous extensive 2-D inversion and 3-D forward modelling of the data set revealed significant along-strike variation of the electrical conductivity structure. 3-D inversion can recover these features but only if the inversion parameters are tuned in accordance with the particularities of the data set. Based on synthetic 3-D data we explore the model space and test the impacts of a wide range of inversion settings. The tests showed that the recovery of a pronounced regional 2-D structure in inversion of the complete impedance tensor depends on the coordinate system. As interdependencies between data components are not considered in standard 3-D MT inversion codes, 2-D subsurface structures can vanish if data are not aligned with the regional strike direction. A priori models and data weighting, that is, how strongly individual components of the impedance tensor and/or vertical magnetic field transfer functions dominate the solution, are crucial controls for the outcome of 3-D inversion. If deviations from a prior model are heavily penalized, regularization is prone to result in erroneous and misleading 3-D inversion models, particularly in the presence of strong conductivity contrasts. A 'good' overall rms misfit is often meaningless or misleading as a huge range of 3-D inversion results exist, all with similarly 'acceptable' misfits but producing significantly differing images of the conductivity structures. Reliable and meaningful 3-D inversion models can only be recovered if data misfit is assessed systematically in the frequency-space domain. © The Authors 2013 Published by Oxford University Press on behalf of The Royal Astronomical Society.
1414.
Modern isotope hydrology and controls on δD of plant leaf waxes at Lake El'gygytgyn, NE Russia
Climate of the Past,
9
(1)
335-352
2013
ISSN: 18149324Keywords:▾
biomarker; calibration; diatom; hydrogen isotope; ice cover; isotopic analysis; isotopic composition; isotopic ratio; lacustrine deposit; lipid; paleoclimate; paleohydrology; precipitation (climatology); reconstruction; sediment core; silica; wax, Chukchi; Elgygytgyn Lake; Russian Federation
Abstract: ▾ Stable isotope data from lipid biomarkers and diatom silica recovered from lake sediment cores hold great promise for paleoclimate and paleohydrological reconstructions. However, these records rely on accurate calibration with modern precipitation and hydrologic processes and only limited data exist on the controls on the -D values for nalkanoic acids from plant leaf waxes. Here we investigate the stable isotopic composition of modern precipitation, streams, lake water and ice cover, and use these data to constrain isotope systematics of the Lake El'gygytgyn Basin hydrology. Compound-specific hydrogen isotope ratios determined from n-alkanoic acids from modern vegetation are compared with modern precipitation and lake core top sediments. Multispecies net (apparent) fractionation values between source water (precipitation) and modern vegetation (e.g., quot;wax/precip mean value is ?107±12 ) agree with previous results and suggest a consistent offset between source waters and the -D values of alkanoic acids. We conclude that although there may be some bias towards a winter precipitation signal, overall -D values from leaf wax n-alkanoic acids record annual average precipitation within the El'gygytgyn Basin. A net fractionation calculated for 200-yr-integrated lake sediments yields quot;30/precip = ?968and can provide robust net "apparent" fractionation to be used in future paleohydrological reconstructions. © Author(s) 2013. CC Attribution 3.0 License.
1413.
Amplified bioproductivity during Transition IV (332 000–342 000 yr ago): evidence from the geochemical record of Lake El'gygytgyn
Climate of the Past,
9
(2)
679-686
2013
1412.
Modeling East Asian climate and impacts of atmospheric CO2 concentration during the Late Cretaceous (66Ma)
Palaeogeography, Palaeoclimatology, Palaeoecology,
385190-201
2013
ISSN: 00310182Keywords:▾
air temperature; carbon dioxide; climate effect; climate modeling; climate variation; concentration (composition); Cretaceous; greenhouse gas; monsoon; paleogeography; precipitation (climatology); seasonal variation; water budget; wind direction, Far East
Abstract: ▾ Utilizing the Community Climate System Model version 2 from the National Center for Atmospheric Research (NCAR) and the reconstructed paleogeographic data, we simulate East Asian climate in the Late Cretaceous (66Ma) and investigate the impacts of atmospheric CO2 concentration on climate. The simulations show that the large-scale pressure systems and prevailing wind directions showed a remarkable seasonal variation over East Asia at 66Ma, which indicates a monsoon feature over East Asia. The East Asian winter and summer monsoons showed a synchronous variation, that is, a strong (weak) winter monsoon accompanied a strong summer (weak) monsoon. At 66Ma, there was more precipitation over the eastern coasts of Asia and less precipitation in the mid-latitudes of the inland areas, but there was no meiyu rainy belt in the subtropics of the East Asian land like the present climate. Moreover, the simulated Cretaceous climate over East Asia was warmer relative to the present day. Annual mean surface air temperature was higher over Asia at that time and close to the estimation from the geological evidence. In the Late Cretaceous, when atmospheric CO2 concentration is reduced, the East Asia climate has a significant change, with weaker winter and summer monsoons over East Asia. Annual mean surface air temperature and annual total precipitation reduce in most of land and ocean. Negative difference of surface water budget appeared mainly in the eastern part of East Asia, indicating a drier soil surface, while positive differences appeared in the mid-latitudes of central-western Asia, indicating a wetter soil surface. © 2012 Elsevier B.V.
1411.
Controls on seasonal variations of silicate weathering and CO2 consumption in two river catchments on the NE Tibetan Plateau
Journal of Asian Earth Sciences,
62547 – 560
2013
ISSN: 13679120Keywords:▾
Buha River; China; Qinghai; Qinghai-Xizang Plateau; Shaliu River; carbon dioxide; climate effect; erosion; ionic composition; lithology; river water; seasonal variation; silicate; suspended particulate matter; weathering
Abstract: ▾ Water samples from the Buha and Shaliu Rivers, located on the semi-arid northeastern Tibetan Plateau, were collected weekly over a one year period. The major ionic compositions of water samples were measured and the daily contents of suspended particulate material (SPM) were monitored in both rivers in order to investigate the influence of lithology, climate and physical erosion on seasonal silicate weathering. In the Shaliu River, weathering of trace amounts of calcite contributes more than 50% of the Ca2+ and HCO3- to the river water. Through high-resolution variations of Ca2+ concentrations and elemental ratios, the signal of carbonate precipitation is captured at the end of monsoon in this river. The measured physical erosion rate is only 8.7-16.0mm/kyr in this semi-arid region, which is 2-3 orders of magnitude lower than that in the Himalaya and nearby regions.In contrast with several orders of magnitude in seasonal variations of silicate weathering rates in both catchments, the distinct lithology between the catchments only leads to a 15 times difference of annual net CO2 consumption. The correlation analysis shows that seasonal silicate weathering is strongly dependent on water discharge in the semi-arid area. The most important observation is that, unrecognized by the previous studies, both physical erosion rate and air temperature exhibit two distinct trends with silicate weathering rates (and net CO2 consumption) during the years. The two trends might suggest that temperature plays a more important role on the CO2 consumption rate before the mid-monsoon under a condition of low water discharge than that after the monsoon with a high water discharge. During the period before the mid-monsoon, the relationship between temperature and silicate weathering rate exhibits higher activation energy than after the mid-monsoon, suggesting a greater dissolution of uneasily weatherable minerals from groundwater, frozen soil, and/or dust input. The relationship between erosion and weathering during the period before the mid-monsoon indicates a faster increase of silicate weathering rate, because freezing erosion produces large amount of high surface area minerals. © 2012 Elsevier Ltd.
1410.
Chronology of the terrestrial Upper Cretaceous in the Songliao Basin, northeast Asia
Palaeogeography, Palaeoclimatology, Palaeoecology,
38544-54
2013
ISSN: 00310182Keywords:▾
borehole; Cretaceous-Tertiary boundary; drilling; geochronology; geodynamics; geological record; geomagnetic field; lithostratigraphy; Maastrichtian; magnetostratigraphy; sedimentary sequence; stratigraphic correlation; Turonian; uranium-lead dating, China; Songliao Basin
Abstract: ▾ The Cretaceous was a period of great environmental, biological and geodynamical change, but a paucity of an accurate time frame for continental strata has prevented our understanding of the terrestrial processes and the integration of marine and terrestrial records. Here we present an integrated chronology for the terrestrial Upper Cretaceous in East Asia based on new high-resolution magnetostratigraphic results and previously published SIMS U-Pb zircon analyses of the Cretaceous Continental Scientific Drilling borehole sequence from the Songliao Basin in northeast China (hereafter termed CCSD-SK-I), which consists of a sedimentary sequence from the upper Quantou Formation (K2q) to the Mingshui Formation (K2m). Correlation to the geomagnetic polarity timescale was achieved by combining magnetostratigraphic and SIMS U-Pb zircon geochronologic data, and lithostratigraphy. Our correlation suggests that the CCSD-SK-I sedimentary sequence spans from the upper chron C34n to chron C29r. The age of the sedimentary sequence from the upper Quantou Formation (K2q) to the Mingshui Formation (K2m) in the Songliao Basin can thus be constrained to an interval from the Turonian to the Maastrichtian ages. In addition, our correlation puts the Cretaceous-Paleogene boundary in the upper part of Member 2 of the Mingshui Formation (K2m2). The constructed comprehensive chronology allows the precise correlation of the terrestrial Upper Cretaceous of the Songliao Basin to marine strata as well as other continental sequences. © 2012 Elsevier B.V.
1409.
Clay mineralogy of the middle Mingshui Formation (upper Campanian to lower Maastrichtian) from the SKIn borehole in the Songliao Basin, NE China: Implications for palaeoclimate and provenance
Palaeogeography, Palaeoclimatology, Palaeoecology,
385162-170
2013
ISSN: 00310182Keywords:▾
Campanian; diagenesis; hydrolysis; illite; kaolinite; lacustrine deposit; Maastrichtian; mudstone; paleoclimate; provenance; siltstone; smectite, China; Heilongjiang; Xiao Hinggan Mountains
Abstract: ▾ Clay mineralogy of a 60. m thick section of the middle Mingshui Formation (upper Campanian to lower Maastrichtian) from the SKIn borehole (Songliao Basin in NE China) has been studied to assess the palaeoclimate and provenance. The sedimentary succession is composed of shore to shallow lacustrine mudstones and siltstones in the lower part, and meandering fluvial sandstone-mudstone sequences in the upper part. The clay mineral assemblage is characterized by the predominance of smectitic minerals, with some exceptions of illite-rich layers, and trace amounts of kaolinite and chlorite. The high smectite content (>. 90% on average) in lacustrine sediments could source from erosion of smetitic soils and volcanic materials in source areas. The Lesser Xing'an-Zhangguangcai Range was the potential provenance area for the sediments, with volcanic activity occurring at ~. 70. Ma, when the temperate semi-humid palaeoclimate was favorable for the clay formation. Smectite presented in meandering fluvial sandstones is of early diagenetic origin, formed by hydrolysis and alteration of primary minerals after deposition. Illite in overbank deposits is interpreted as a result of erosion of granitic rocks and sorting in sedimentation processes. The clay mineralogy of the studied strata contains information on palaeoclimate and provenance, although early diagenetic processes may have influenced the mineralogical composition in some intervals of sandstones. © 2012 Elsevier B.V.
1408.
Climate induced changes as registered in inorganic and organic sediment components from Laguna Potrok Aike (Argentina) during the past 51ka
Quaternary Science Reviews,
71154–s166
2013
Keywords:▾
Argentina; Laguna Potrok Aike; Patagonia; Santa Cruz [Argentina]; algae; Bacillariophyta; Bryophyta; Cyanobacteria; Biogeochemistry; Biological materials; Carbonates; Fourier transform infrared spectroscopy; Glacial geology; Lakes; Nitrogen; Permafrost; Phytoplankton; Sediments; Silica; Argentina; Biogenic silica; Diffuse reflectance fourier transform infrared; ICDP project PASADO; Lake levels; Patagonia; Primary productivity; algal bloom; allochthon; carbon; carbonate; climate change; climate conditions; FTIR spectroscopy; global warming; growth rate; infiltration; latitude; moss; paleoenvironment; permafrost; primary production; proxy climate record; reconstruction; sediment analysis; silica; Southern Hemisphere; surface water; temperature effect; Organic carbon
Abstract: ▾ Total organic carbon, total inorganic carbon, biogenic silica content and total organic carbon/total nitrogen ratios of the Laguna Potrok Aike lacustrine sediment record are used to reconstruct the environmental history of south-east Patagonia during the past 51ka in high resolution. High lake level conditions are assumed to have prevailed during the Last Glacial, as sediments are carbonate-free. Increased runoff linked to permafrost and reduced evaporation due to colder temperatures and reduced influence of Southern Hemispheric Westerlies (SHW) may have caused these high lake levels with lake productivity being low and organic matter mainly of algal or cyanobacterial origin. Aquatic moss growth and diatom blooms occurred synchronously with southern hemispheric glacial warming events such as the Antarctic A-events, the postglacial warming following the LGM and the Younger Dryas chronozone. During these times, a combination of warmer climatic conditions with related thawing permafrost could have increased the allochthonous input of nutrients and in combination with warmer surface waters increased aquatic moss growth and diatom production. The SHW were not observed to affect southern Patagonia during the Last Glacial. The Holocene presents a completely different lacustrine system because (a) permafrost no longer inhibits infiltration nor emits meltwater pulses and (b) the positioning of the SHW over the investigated area gives rise to strong and dry winds. Under these conditions total organic carbon, total organic carbon/total nitrogen ratios and biogenic silica cease to be first order productivity indicators. On the one hand, the biogenic silica is influenced by dissolution of diatoms due to higher salinity and pH of the lake water under evaporative stress characterizing low lake levels. On the other hand, total organic carbon and total organic carbon/total nitrogen profiles are influenced by reworked macrophytes from freshly exposed lake level terraces during lowstands. Total inorganic carbon remains the most reliable proxy for climatic variations during the Holocene as high precipitation of carbonates can be linked to low lake levels and high autochthonous production. The onset of inorganic carbon precipitation has been associated with the southward shift of the SHW over the latitudes of Laguna Potrok Aike. The refined age-depth model of this record suggests that this shift occurred around 9.4cal.kaBP. © 2012 Elsevier Ltd.
1407.
Climatic variability during the last interglacial inferred from geochemical proxies in the Lake El'gygytgyn sediment record
Palaeogeography, Palaeoclimatology, Palaeoecology,
386408-414
2013
ISSN: 00310182Keywords:▾
climate variation; geochemical method; global warming; Last Interglacial; marine record; paleoenvironment; paleolimnology; primary production; reconstruction; sediment core; sedimentation rate, Chukchi; Elgygytgyn Lake; Russian Federation
Abstract: ▾ The Last Interglacial Period (LIP) is often regarded as a good analogue for potential climatic conditions under predicted global warming scenarios. Despite this, there is still debate over the nature, duration and frequency of climatic changes during this period. One particularly contentious issue has been the apparent evidence of climatic instability identified in many marine cores but seemingly lacking from many terrestrial archives, especially within the Arctic, a key region for global climate change research. In this paper, geochemical records from Lake El'gygytgyn, north-eastern Russia, are used to infer past climatic changes during the LIP from within the high Arctic. With a sampling resolution of ~. 20-~. 90. years, these records offer the potential for detailed, high-resolution palaeoclimate reconstruction. This study shows that the LIP commenced in central Chukotka ~. 129. thousand years ago (ka), with the warmest climatic conditions occurring between ~. 128 and 127. ka before being interrupted by a short-lived cold reversal. Mild climatic conditions then persisted until ~. 122. ka when a marked reduction in the sedimentation rate suggests a decrease in precipitation. A further climatic deterioration at ~. 118. ka marks the return to glacial conditions. This study highlights the value of incorporating several geochemical proxies when inferring past climatic conditions, thus providing the potential to identify signals related to environmental change within the catchment. We also demonstrate the importance of considering how changes in sedimentation rate influence proxy records, in order to develop robust palaeoenvironmental reconstructions. © 2013 Elsevier B.V.
1406.
CO2 discharge in an active, non-volcanic continental rift area (Czech Republic): Characterisation (δ13C, 3He/4He) and quantification of diffuse and vent CO2 emissions
Chemical Geology,
33971 – 83
2013
ISSN: 00092541Keywords:▾
Czech Republic; Degassing; Gas emissions; Geologic models; Helium; Isotopes; Particulate emissions; Radium; Soils; C values; Continental rift; Czech Republic; Diffuse degassing; Eger Rift; Emission rates; Fault zone; Fluid injections; Gas compositions; Gas emission rates; Gas releasing; Grid-spacings; Ground mapping; Helium isotopes; Isotope ratio; ; Measurements of; Soil CO; Soil flux; Soil gas; Soil gas concentration; Subcontinental mantle; Total CO; carbon dioxide; carbon emission; carbon flux; degassing; diffusion; fluid injection; helium isotope; isotopic analysis; isotopic composition; isotopic ratio; rifting; soil gas; Carbon dioxide
Abstract: ▾ In the western Eger Rift (ER) area along the Počatky-Plesná fault zone (PPZ) CO2 degassing occurs predominantly within two mofette fields Bublák and Hartoušov. We studied 27 wet mofettes belonging to these mofette fields for gas emission rates repeatedly between 2007 and 2009 and selected mofettes for gas composition and isotope ratios (δ13C, 3He/4He). Detailed ground mapping along the PPZ provided further two separated diffuse degassing structures (DDS) within the mofette fields Hartoušov and Bublák. The DDS Hartoušov was studied in detail by measurements of 682 CO2 soil gas concentrations, 762 CO2 soil gas fluxes (max. 10 grid spacing) and partly by analyses of isotope ratios (13C/12C, 3He/4He) of soil gas. At the DDS Hartoušov the total CO2 soil flux yielded 1.559tm-2d-1 in spring 2009 and the CO2 emission rate at the wet mofettes of Hartoušov mofette field yielded 0.62td-1. The total CO2 discharge of the 27 wet mofettes was 3.75t d-1.At sites with high CO2 soil flux, the portion of mantle-derived helium is in the same range as the releasing at wet mofettes; both cover the signature of the subcontinental mantle. Also, the δ13C values analysed in the gas releasing from wet mofettes and those analysed in soil gas are nearly the same. Taking in account a biogenic soil CO2 flux of 25gm-2d-1 as background, the mantle-derived CO2 flux yielded approximately 1566tm-2d-1. As a result of the CO2 flux mapping of the DDS Hartoušov, it could be proved that 97.4% of the released soil CO2 (1.518tm-2d-1) stems from sites with CO2 fluxes higher than 500gm-2d-1-pointing to dominantly fault-related CO2 release.At the central mofette Bublák (B2), the gas emission rate was determined for the first time in 1993. Measurements repeated between 2007 and 2009 showed a clear increase in the gas emission rate of more than 40%, correlating well with the increase of the 3He/4He ratios from 5Ra to approximately 6Ra between 1993 and 2008 at this location (Bräuer et al., 2009).The Bublák mofette field is characterised by the highest CO2 emission rate along the PPZ, and in combination with the helium isotope signature of the European subcontinental mantle, this area was identified as a deep-reaching fluid injection zone. © 2012 Elsevier B.V.
1405.
Composition and origin of rhyolite melt intersected by drilling in the Krafla geothermal field, Iceland
Contributions to Mineralogy and Petrology,
165
(2)
327-347
2013
ISSN: 00107999
Publisher: Springer Verlag
Keywords:▾
augite; basalt; chemical composition; deep drilling; emplacement; geothermal system; hydrogen isotope; hydrothermal fluid; partial melting; phenocryst; pigeonite; plagioclase; rare earth element; rhyolite; stable isotope; strontium isotope; titanomagnetite; zoning, Iceland; Krafla
Abstract: ▾ The Iceland Deep Drilling Project Well 1 was designed as a 4- to 5-km-deep exploration well with the goal of intercepting supercritical hydrothermal fluids in the Krafla geothermal field, Iceland. The well unexpectedly drilled into a high-silica (76.5 % SiO2) rhyolite melt at approximately 2.1 km. Some of the melt vesiculated while extruding into the drill hole, but most of the recovered cuttings are quenched sparsely phyric, vesicle-poor glass. The phenocryst assemblage is comprised of titanomagnetite, plagioclase, augite, and pigeonite. Compositional zoning in plagioclase and exsolution lamellae in augite and pigeonite record changing crystallization conditions as the melt migrated to its present depth of emplacement. The in situ temperature of the melt is estimated to be between 850 and 920 °C based on two-pyroxene geothermometry and modeling of the crystallization sequence. Volatile content of the glass indicated partial degassing at an in situ pressure that is above hydrostatic (~16 MPa) and below lithostatic (~55 MPa). The major element and minor element composition of the melt are consistent with an origin by partial melting of hydrothermally altered basaltic crust at depth, similar to rhyolite erupted within the Krafla Caldera. Chondrite-normalized REE concentrations show strong light REE enrichment and relative flat patterns with negative Eu anomaly. Strontium isotope values (0.70328) are consistent with mantle-derived melt, but oxygen and hydrogen isotope values are depleted (3.1 and -118 ‰, respectively) relative to mantle values. The hydrogen isotope values overlap those of hydrothermal epidote from rocks altered by the meteoric-water-recharged Krafla geothermal system. The rhyolite melt was emplaced into and has reacted with a felsic intrusive suite that has nearly identical composition. The felsite is composed of quartz, alkali feldspar, plagioclase, titanomagnetite, and augite. Emplacement of the rhyolite magma has resulted in partial melting of the felsite, accompanied locally by partial assimilation. The interstitial melt in the felsite has similar normalized SiO2 content as the rhyolite melt but is distinguished by higher K2O and lower CaO and plots near the minimum melt composition in the granite system. Augite in the partially melted felsite has re-equilibrated to more calcic metamorphic compositions. Rare quenched glass fragments containing glomeroporphyritic crystals derived from the felsite show textural evidence for resorption of alkali feldspar and quartz. The glass in these fragments is enriched in SiO2 relative to the rhyolite melt or the interstitial felsite melt, consistent with the textural evidence for quartz dissolution. The quenching of these melts by drilling fluids at in situ conditions preserves details of the melt-wall rock interaction that would not be readily observed in rocks that had completely crystallized. However, these processes may be recognizable by a combination of textural analysis and in situ analytical techniques that document compositional heterogeneity due to partial melting and local assimilation. © 2012 Springer-Verlag.
1404.
Constraining clay hydration state and its role in active fault systems
Geochemistry, Geophysics, Geosystems,
14
(4)
1039-1052
2013
ISSN: 15252027
Publisher: Blackwell Publishing Ltd
Keywords:▾
Clay minerals; Ethylene; Ethylene glycol; Particle size analysis; Strike-slip faults; Tectonics, clay-hydration; Humidity chambers; NanTroSEIZE; SAFOD; Smectites, Hydration, active fault; adsorption; crystal structure; displacement; experimental mineralogy; humidity; hydration; San Andreas Fault; smectite; swelling; temperature effect; water; water content, Japan; Nankai Trough; Pacific Ocean; United States
Abstract: ▾ To understand the role of hydrated clay minerals in active fault systems, a humidity chamber connected to an X-ray diffractometer was used to determine the adsorption of water onto and/or into the crystal structure of smectite. This new type of analysis was carried out under specific temperature and humidity conditions, using powdered clay size fractions (< 2 μm) of rock samples from the San Andreas Fault (USA) and the Nankai Trough (Japan). Pressure cannot be controlled, but does not significantly affect clay swelling at shallow conditions. Air-dried samples show a discrete smectite phase that swells after traditional ethylene glycolation to an interlayer distance of 1.5 and 1.7 nm. Using the humidity chamber, however, the samples show a shorter interlayer distance, between 1.09 and 1.54 nm. Based on our analysis, we show that (i) ethylene glycol overestimates the size of the interlayer space, and therefore water content, so is a crude maximum only; (ii) interlayer swelling occurs in smectite clay minerals at all temperatures between 25 and 95°C; and (iii) particle orientation increases with increasing humidity, indicating a higher mobility of smectite from interlayer hydration. Detailed characterization of the hydration state of smectite under original conditions is critical for understanding of clay-fluid interaction, the mechanical behavior during fault displacements, and fluid budgets at depth. We propose that humidity chamber experiments should be the new standard procedure to constrain swelling characteristics of natural and synthetic clay minerals. © 2013. American Geophysical Union. All Rights Reserved.
1403.
Continental Scientific Drilling Project of Cretaceous Songliao Basin: Scientific objectives and drilling technology
Palaeogeography, Palaeoclimatology, Palaeoecology,
3856-16
2013
ISSN: 00310182Keywords:▾
carbon cycle; climate variation; Cretaceous; drilling; geological record; proxy climate record; sedimentary basin; sedimentary sequence; source rock; stratigraphic boundary; stratigraphic correlation; timescale, China; Songliao Basin
Abstract: ▾ The Continental Scientific Drilling Project at the Cretaceous-age Songliao Basin is a drilling initiative under the framework of the International Continental Scientific Drilling Program, to recover a nearly complete Cretaceous terrestrial sedimentary record in the Songliao Basin, northeastern China. The recovered cores will provide unique opportunities for the geosciences community to advance the understanding of climate change in the Cretaceous greenhouse world, and provide a documentation of geological events relevant to the carbon cycle during this time period.This drilling project will address significant geological questions, such as the identification of important stratigraphic boundaries and the marine-terrestrial correlations of stratigraphy, the reasons for the biotic response to the terrestrial environmental changes, the terrestrial response to the Cretaceous oceanic anoxic events, the formation of terrestrial petroleum source rocks, and the mechanisms for the Cretaceous magnetic Normal Superchron (CNS).In the first stage of this drilling project, the SKI drilling, rock cores of 2485.89. m in total length were recovered and the recovery ratio reached 96.46%. A series of drilling and coring technologies including regular, confined, directional, and sealed coring, were utilized to ensure a higher recovery ratio for the core, and will be described at the end of this paper. Well loggings were conducted right after coring. Core handling and storage were arranged in such a way that the scientific research was conducted on half of each core, whereas the other half of each core was preserved for long-term storage. The upcoming second stage, the SKII drilling, will combine with data from the existing SKI to provide complete high-resolution climate records of the terrestrial environment for the whole Cretaceous time period. © 2012 Elsevier B.V.
1402.
Contrast experiment about dissolution of feldspar in different freshwater diagenetic systems
Geoscience,
27
(4)
925
2013
1401.
Corrigendum to “Impact of volcanism on the evolution of Lake Van II: Temporal evolution of explosive volcanism of Nemrut Volcano (eastern Anatolia) during the past ca. 0.4 Ma” [J. Volcanol. Geotherm. Res. 253 (2013), 15–34] (S0377027312003587) (10.1016/j.jvolgeores.2012.12.009))
Journal of Volcanology and Geothermal Research,
253131-133
2013
ISSN: 03770273
Publisher: Elsevier B.V.
Abstract: ▾ 1 Corrections in Table 1 and Fig. 10 The attached Table 2 and Fig. 10 should replace the original Table 1 and Fig. 10. 1.1 Correction details in Table 2 1.2 Correction details in Fig. 10 2 Corrections in the text body The corrections in Table 2 necessitate the following slight changes in the text body (pages 22–29) 4.1.8. (page 23): Replace “Pantelleritic rhyolite” with “Comenditic rhyolite”. 4.1.20. (page 27): Replace “Trachyte” with “Comenditic rhyolite”. 4.1.21. (page 28): Replace “Pantelleritic rhyolite” with “Comenditic rhyolite”. 4.2.3. (page 28): Replace “Comenditic rhyolite” with “Comenditic rhyolite to trachyte”. 4.2.4. (page 28): Replace “Pantelleritic rhyolite” with “Comenditic rhyolite”. 4.2.6. (page 29): Replace “Trachyte” with “Comenditic rhyolite”. © 2013 Elsevier B.V.
1400.
Chronology of Lake El'gygytgyn sediments – a combined magnetostratigraphic, palaeoclimatic and orbital tuning study based on multi-parameter analyses
Climate of the Past,
9
(6)
2413-2432
2013
1399.
Coupled molybdenum, iron and uranium stable isotopes as oceanic paleoredox proxies during the Paleoproterozoic Shunga Event
Chemical Geology,
362193--210
2013
1398.
Cretaceous paleogeography and paleoclimate and the setting of SKI borehole sites in Songliao Basin, northeast China
Palaeogeography, Palaeoclimatology, Palaeoecology,
38517-30
2013
ISSN: 00310182Keywords:▾
Albian; Aptian; Berriasian; borehole; cooling; geological record; glaciation; lacustrine deposit; literature review; oxygen isotope; paleoclimate; paleogeography; paleontology; sedimentary basin; subsidence; timescale; Valanginian, China; Songliao Basin
Abstract: ▾ As a paradigm of greenhouse climate in Earth's history, the Cretaceous provides significant rock records of global climate changes under conditions of greenhouse climate. The Songliao Basin, among the longest duration (85-90m.y.) of continental sedimentary basins, provides an excellent opportunity to recover a nearly complete Cretaceous terrestrial sedimentary record. Extensive lake deposits, ten-kilometers deep and covering an area of 260,000km2 of the Songliao Basin, provide unique, detailed records that can be tied to the global stratigraphic time scale, thereby improving our understanding of the continental paleoclimate and ecological system. The two coreholes at SKIs and SKIn sites were drilled into this basin and completed with a total length of 2485.89m of recovered core that spanned the complete middle-to-Upper Cretaceous strata in the basin. The unique geological setting of long-term continuous subsidence within the largest Cretaceous landmass in the world - makes the Cretaceous Songliao Basin of northeastern China an ideal place to study Cretaceous climate change on the continent. This paper reviews the literature on the paleogeography and paleoclimate of the northern East Asia and the Songliao Basin during the Cretaceous. Based on the climatologically sensitive deposits, oxygen isotope studies, and paleontology, the climate during the Cretaceous in the Songliao Basin was temperate and humid with relatively abundant rainfall. During the period, significant changes - four cooling, three warming, and three semiarid events - are generally consistent with the oxygen isotope data from East Asia, and the four cooling events, in Berriasian-Valanginian, Aptian-Albian, early Santonian, and Campanian-Maastrichtian, may be related to potential glaciations in Cretaceous. © 2012 Elsevier B.V.
1397.
Crustal anisotropy in the eastern Sea of Marmara region in Northwestern Turkey
Bulletin of the Seismological Society of America,
103
(2 A)
911-924
2013
ISSN: 00371106Keywords:▾
Angular deviations; Crustal anisotropy; Hypocentral depth; Northwestern Turkey; Polarization direction; Second order effect; Seismic anisotropy; Shear wave splitting, Shear waves; Strike-slip faults, Anisotropy, anisotropy; crustal structure; fault zone; North Anatolian Fault; plate boundary; San Andreas Fault; seismicity; wave splitting, Istanbul [Istanbul (PRV)]; Istanbul [Turkey]; Sea of Marmara; Turkey
Abstract: ▾ The North Anatolia Fault Zone (NAFZ) is a transform zone 1600 km in length representing the plate boundary between the westward moving Anatolian Plate and stable Eurasia. Almost the entire fault zone has failed during the last century except for the Sea of Marmara section, which is located in direct vicinity to the city of Istanbul. In this study, we investigate the crustal anisotropy along the eastern Marmara section of the NAFZ based on shear-wave splitting. We measure seismic anisotropy parameters, namely, the fast polarization direction (PD) and time delay (TD), by analyzing local seismicity recorded at selected seismographs operated throughout the eastern Sea of Marmara region. Our shear-wave splitting (SWS) observations indicate a predominant northwest-southeast-oriented PD, which is subparallel to both the orientation of the regional SHmax in northwest Turkey and the local NAFZ strike along the Princes' Islands segment. Toward the south, at the Armutlu Peninsula, we find a different PD pattern reflecting local fault strikes, SHmax as well as strain asymmetry between different crustal blocks across the fault zone. Applying strict quality criteria enables us to identify robust, preferred fast PDs, which suggests that initially observed PD heterogeneities are sometimes caused by second-order effects in the data rather than by varying PDs. Comparing TD and hypocentral depth distribution, we find the depth extent of the anisotropy is confined to the uppermost 10-km depth of crust. We combine our SWS results with those from previous studies conducted along the San Andreas fault (SAF) and NAFZ in order to investigate the relation of angular deviations of the PDs from regional SHmax and local fault strikes with fault-zone distance. We find that fast PDs are mainly controlled by the local fault structure in close proximity to a fault zone (5 and 10 km) while they are controlled by crustal stress at off-fault locations (5 and 10 km).
1396.
Cymbella gravida sp. nov. A new lacustrine taxon from Santa Cruz, Argentina
Diatom Research,
28
(4)
467 – 472
2013
1395.
Dating the termination of the Palaeoproterozoic Lomagundi-Jatuli carbon isotopic event in the North Transfennoscandian Greenstone Belt
Precambrian Research,
224160--168
2013
ISSN: 03019268
Publisher: Elsevier
Keywords:▾
carbon isotope; carbonate rock; deposition; geochronology; greenstone belt; Proterozoic; radionuclide; sedimentation; uranium-lead dating; zircon, Fennoscandia; Finland; Kola Peninsula; Murmansk [Russian Federation]; Norway; Russian Federation; South Africa; Transvaal
Abstract: ▾ Existing radio-isotopic age constraints indicate that the global Palaeoproterozoic Lomagundi-Jatuli large, positive carbonate carbon isotopic excursion, with δ13C values >+5‰, occurred between 2.2 and 2.06Ga. In the North Transfennoscandian Greenstone Belt of the Kola Peninsula, NW Russia, northern Norway and Finland, the Lomagundi-Jatuli Event is recorded in the carbonate rocks of the Umba and Kuetsjärvi Sedimentary Formations in the Imandra-Varzuga and Pechenga greenstone belts. In both areas, thick mafic volcanic units (Umba and Kuetsjärvi Volcanic Formations) overlie the carbon isotopic excursion-bearing sedimentary units. Overlying and younger sedimentary units contain carbonate rocks with δ13C values typically ranging between c. -1 and +3‰, signalling the termination of the Lomagundi-Jatuli excursion.Two new U-Pb ID-TIMS (isotope-dilution thermal ionisation mass spectrometry) zircon dates constrain this termination in both successions. The lower unit of the Il'mozero Sedimentary Formation is a cross- and parallel-bedded volcaniclastic greywacke derived largely from erosion of the underlying Umba Volcanic Formation. It has yielded detrital zircons with 207Pb/206Pb dates as young as 2055.5±2.3Ma, which is a maximum age for deposition and is inferred to date part of the underlying Umba volcanics. In Pechenga, the Kolosjoki Sedimentary Formation was intersected by a drill hole obtained by the ICDP (International Continental Scientific Drilling Program)-supported FAR-DEEP (Fennoscandian Arctic Russia-Drilling Early Earth Project) drilling programme. Zircons from a mafic fine tuff in this drill core have yielded a 207Pb/206Pb age of 2056.6±0.8Ma. This age is interpreted as an eruption age contemporaneous with sedimentation. The new age determinations overlap each other within uncertainty, and is within error of previously published detrital zircon ages of 2058±2Ma from the Kolosjoki Sedimentary Formation and 2049±28Ma from the Kuetsjärvi Volcanic Formation. Combined, these indicate that the Lomagundi-Jatuli excursion terminated across Fennoscandia by 2056.6±0.8Ma and may correlate with similar termination ages in Fennoscandia and the Transvaal, South Africa. © 2012.