All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
1169.
Origin of a rhyolite that intruded a geothermal well while drilling at the Krafla volcano, Iceland
Geology,
39
(3)
231-234
2011
ISSN: 00917613DOI:10.1130/G31393.1
Keywords:▾
Anhydrous mantle; Geothermometry; Hydrothermal alterations; Hydrothermally; Icelands; In-situ; Oxygen isotopic; Saturation pressure, Geothermal wells; Glass; Granite; Oxygen; Volcanoes, Well drilling, basalt; geothermal system; hydrogen isotope; hydrothermal alteration; magma assimilation; magma chamber; mantle source; oxygen isotope ratio; rhyolite; volcanology, Iceland; Krafla
Abstract: ▾ Magma flowed into an exploratory geothermal well at 2.1 km depth being drilled in the Krafla central volcano in Iceland, creating a unique opportunity to study rhyolite magma in situ in a basaltic environment. The quenched magma is a partly vesicular, sparsely phyric, glass containing ~1.8% of dissolved volatiles. Based on calculated H2O-CO2 saturation pressures, it degassed at a pressure intermediate between hydrostatic and lithostatic, and geothermometry indicates that the crystals in the melt formed at ~900 °C. The glass shows no signs of hydrothermal alteration, but its hydrogen and oxygen isotopic ratios are much lower than those of typical mantle-derived magmas, indicating that this rhyolite originated by anhydrous mantle-derived magma assimilating partially melted hydrothermally altered basalts. © 2011 Geological Society of America.
1168.
P- And S-wave velocities and velocity anisotropy of core samples from the Outokumpu 2500 m crustal section: Implications for the nature of seismic reflections
Special Paper of the Geological Survey of Finland,
2011
(51)
83 – 94
2011
ISSN: 07828535ISBN:
978-952217152-8
Abstract: ▾ Laboratory measurements as well as modelling of the physical properties of rock materials are important for the understanding and interpretation of both downhole (logging) and geophysical (surface) observations. On 29 core samples of the Outokumpu scientific drill hole, covering the depth range of 198-2491 m, we calculated the average (isotropic) intrinsic P- and S-wave velocities (V p,Vs) and densities from their modal composition, based on bulk rock (XRF) and mineral chemistry (microprobe), using least squares fitting. For 13 cube-shaped samples representing the main lithologies, we measured P- and S-wave velocities in 3 orthogonal directions at pressures of up to 600 MPa in order to determine their directional dependence and crack sensitivity. Comparison of the calculated velocities with the experimentally derived in situ velocities gave evidence for microcracks that are not completely closed. Microcracks may have an important bearing on the in situ velocities, in addition to the lithological control. Velocity measurements as well as 3D velocity calculations based on neutron diffraction texture measurements revealed that velocity anisotropy and shear wave splitting are important properties of the biotite gneisses that dominate about 70% of the drilled crustal section. Reflection coefficients (Rc) for the various lithological contacts based on modelled and measured velocities provide evidence that the different lithologies of the ophiolite-related assemblage have the potential to cause the marked reflections at 1300-1500 m depth, as revealed by the high-resolution seismic reflection line (OKU-1).
1167.
Scientific collaboration on past speciation conditions in ohrid (SCOPSCO): Recent and fossil Ostracods from Lake ohrid as indicators of past environments: A coupled ecological and molecular genetic approach with deep-time perspective
Joannea - Geologie und Palaontologie
(11)
113-115
2011
ISSN: 156294491166.
[English]
Fracture distribution in slimholes drilled for project hotspot: The Snake River Geothermal Drilling Project and the implications for fluid flow
Volume 35 1
,
Page 839-842
2011
Department of Geology, Utah State University, Logan, UT, United StatesISBN:
9781618394828
1165.
Scientific drilling into the San Andreas fault zone - An overview of SAFOD's first five years
Scientific Drilling
(1)
14-28
2011
ISSN: 18168957Keywords:▾
Active fault; Bounding faults; California; Casing deformation; Chemical process; Deformation mechanism; Deforming zone; Downhole measurements; Earthquake nucleation; Fault creep; Fault gouge; Fault model; Geophysical logs; Horizontal stress; Low resistivity; Measured depths; Micro-earthquakes; Pilot holes; Rheological behaviors; S-wave velocity; San Andreas Fault; Scale-up; Scientific drilling; Seismic instrumentation; Seismic velocities; Stress state, Deformation; Earthquakes; Parks; Rheology; Structural geology, Tectonics
Abstract: ▾ The San Andreas Fault Observatory at Depth (SAFOD) was drilled to study the physical and chemical processes controlling faulting and earthquake generation along an active, plate-bounding fault at depth. SAFOD is located near Parkfield, California and penetrates a section of the fault that is moving due to a combination of repeating microearthquakes and fault creep. Geophysical logs define the San Andreas Fault Zone to be relatively broad (~200 m), containing several discrete zones only 2-3 m wide that exhibit very low P- and S-wave velocities and low resistivity. Two of these zones have progressively deformed the cemented casing at measured depths of 3192 m and 3302 m. Cores from both deforming zones contain a pervasively sheared, cohesionless, foliated fault gouge that coincides with casing deformation and explains the observed extremely low seismic velocities and resistivity. These cores are being now extensively tested in laboratories around the world, and their composition, deformation mechanisms, physical properties, and rheological behavior are studied. Downhole measurements show that within 200 m (maximum) of the active fault trace, the direction of maximum horizontal stress remains at a high angle to the San Andreas Fault, consistent with other measurements. The results from the SAFOD Main Hole, together with the stress state determined in the Pilot Hole, are consistent with a strong crust/weak fault model of the San Andreas. Seismic instrumentation has been deployed to study physics of faulting-earthquake nucleation, propagation, and arrest-in order to test how laboratory-derived concepts scale up to earthquakes occurring in nature.
1164.
Outokumpu Deep Drilling Project 2003 - 2010
from Geological Survey of Finland
Publisher
Geological Survey of Finland
2011
ISBN:
9789522171511
1163.
Three-component magnetic logging in the Outokumpu Deep Drill Hole
Special Paper of the Geological Survey of Finland,
2011
(51)
119 – 132
2011
ISSN: 07828535ISBN:
978-952217152-8
Abstract: ▾ In September 2008, the magnetic field in the Outokumpu Deep Drill Hole (OKU R2500) was measured with the Göttinger Bohrloch Magnetometer (GBM). Unlike previous total field measurements with other tools, the three components of the magnetic field and the tool attitude were measured continuously with a resolution of up to 5 cm. This became possible by utilizing a unique orientation system consisting of three fibre optic gyros. After extensive data processing, the magnetic anomalies along the borehole were obtained in the geographic coordinates North, East and Vertical (WGS-84). Two intervals with significant magnetic anomalies were detected. While the disturbances in the first interval (70-300 m) are either manmade or caused by thin layers of black schist, the second interval (1328-1440 m) is dominated by magnetized rocks of the Outokumpu assemblage. The combined interpretation of core data and in-situ measurements indicates less carbonated serpentinite as the host for magnetic minerals. Furthermore, statistical studies of the magnetisation direction, derived from the GBM measurements, suggest a different geological evolution of the host rocks of the upper and lower section of the Outokumpu assemblage.
1162.
Transmission electron microscopy of omphacite and other minerals in eclogites from the CCSD borehole, China: Indications for their deformation and temperature history
European Journal of Mineralogy,
23
(4)
645 – 659
2011
ISSN: 09351221
Publisher: Gebruder Borntraeger Verlagsbuchhandlung
Keywords:▾
China; Boreholes; Burgers vector; Crystal defects; Deformation; Feldspar; Garnets; Grain boundaries; High resolution transmission electron microscopy; Metamorphic rocks; Quartz; Titanium dioxide; Transmission electron microscopy; Twinning; Zeolites; Amphibole; Analcime; CCSD; Eclogites; Omphacite; Rutile; Chinese Continental Scientific Drilling Project; crystal structure; deformation mechanism; eclogite; jadeite; microstructure; omphacite; P-T conditions; P-T-t path; phase transition; recrystallization; temperature gradient; transmission electron microscopy; twinning; ultrahigh pressure metamorphism; Transmissions
Abstract: ▾ Seven eclogite samples from 223 to 584 m depths in the Chinese Continental Scientific Drilling main borehole (CCSDMH) in the Sulu ultrahigh-pressure metamorphic (UHPM) terrane, Eastern China, were studied by transmission electron microscopy (TEM), in order to characterise their microstructures. We observed, among others, omphacite, jadeitic diopside, garnet, amphibole, rutile, Na-rich plagioclase, quartz, K-feldspar, analcime, and diamond (contamination). Omphacite shows a well-known diffusioncontrolled disorder-order phase transition which gives rise to antiphase domains (APDs). In our samples we observed a variation of the APDs' size between ∼5 nm and 2 mm which is correlated with the content in jadeite (Jd) component. The broad maximum of ∼1-2 mm APDs' size is centred on Jd50. This size drops to ∼5-10 nm for Jd37 and Jd66. The size variation can be explained with the T-path of the respective omphacites. While the large APDs of the omphacites formed and coarsened during subduction and exhumation, the smallest APDs formed and grew during exhumation. In contrast to other eclogite occurrences, deformational defects in omphacites from the CCSD-eclogites are mostly very rare. Occasionally, stacking faults parallel to (010), free dislocations with the Burgers vector [001] and those with 1/2[110] connected with antiphase domain boundaries (APBs), deformation twins on (100) and small-angle grain boundaries were observed. The explanation is that most CCSD-omphacites were strongly affected by recrystallisation, which took place above 600 °C during subduction up to its maximum temperature of ∼750 °C and continued during exhumation above 600 °C into the regime of amphibolite facies for several tens of Ma. Garnet shows very rarely crystal defects, while amphiboles usually displayed dislocations and chain multiplicity faults. Rutile of one sample, which contained a few percent Fe, showed fully coherent, nano-sized platelets (Guinier-Preston zones) parallel to (100) and (010). The existence of fluids during retrogression is documented by K-feldspar and analcime in quartz. © 2011 E. Schweizerbart'sche Verlagsbuchhandlung.
1161.
Tropical East African climate change and its relation to global climate: A record from Lake Tanganyika, Tropical East Africa, over the past 90+kyr
Palaeogeography, Palaeoclimatology, Palaeoecology,
303
(1-4)
155-167
2011
ISSN: 00310182Keywords:▾
biogenic deposit; climate change; intertropical convergence zone; lake level; Last Glacial Maximum; paleolimnology; proxy climate record; sediment core; tropical region; X-ray fluorescence, East Africa; East African Lakes; Lake Malawi; Lake Tanganyika
Abstract: ▾ Forcing mechanisms of tropical climate in continental areas remain poorly understood, due in large part to a lack of continuous, long-term, high-fidelity records. Sediment core T97-52V from Lake Tanganyika provides new insight into the timing and mechanisms behind East African climate change over the past 90+. kyr. This record is particularly important, because, other than a recently recovered scientific drill core from Lake Malawi, there are no other continuous, well-dated records from East Africa prior to 60. ka. The high resolution age model presented here provides a large degree of age certainty for the past 45+. kyr, and our suite of proxies allows a thorough examination of Lake Tanganyika's dynamics. From core stratigraphy and chemical analyses, we present evidence of a lake level drop greater than 400. m sometime prior to ~. 90. ka, much greater than that inferred for the LGM, suggesting a period of intense aridity sometime around 100. ka. Additionally, core T97-52. V preserves evidence of worm burrows detected by X-radiographic imagery as indicated by burrow-shaped deposits of iron oxide, indicating a shallow lake at the time of deposition of that material. Intermittently high lake levels between ~. 78. ka and ~. 72. ka developed at the same time as a weakened Asian monsoon and a pluvial phase in Northeast Brazil, suggesting a global reorganization of climate, possibly forced by a reduction in orbital eccentricity. Over the past 60. ka this core preserves the same events recorded in a core collected ~. 100. km away in the southern basin of Lake Tanganyika, including an unexplained increase in biogenic silica at ~. 37. ka, suggesting that this vast lake is responding coherently across both major bathymetric basins to regional and global climate forcing. © 2010 Elsevier B.V.
1160.
U-Pb ages of shocked zircon grains link distal K-Pg boundary sites in Spain and Italy with the Chicxulub impact
Earth and Planetary Science Letters,
310
(3-4)
401-408
2011
Abstract: ▾ The U-Pb ages of shocked zircon crystals from the Chicxulub impact crater and Cretaceous-Paleogene (K-Pg) boundary sites in Haiti, the USA, and Canada, and the pattern of decreasing particle size with paleodistance from the crater, have been used as evidence of a genetic link between Chicxulub and the K-Pg boundary. Despite this, the inference that the K-Pg boundary layer formed as a direct consequence of the Chicxulub impact has been repeatedly questioned. Here we present U-Pb (ID-TIMS) ages and textural evidence of shock metamorphosed zircon grains from the K-Pg boundary at Caravaca, Spain, and Petriccio, Italy, that establish a causal connection between the impact and formation of the K-Pg boundary layer. The shocked zircon grains give data that produce a characteristic age pattern, which indicates a primary source age of 549.5 ± 5.7 Ma and a secondary event at the approximate time of impact at 66. Ma. The intensity of the shock features is proportional to the degree of isotopic resetting, and all textural features and ages are analytically identical to those of previously analyzed zircon from Chicxulub and K-Pg boundary sites in North America. Caravaca and Petriccio were > 8000 km from Chicxulub at the time of impact, and are therefore the farthest K-Pg sites identified that can be linked to Chicxulub through the dating of individual shocked zircon grains. We conclude that the combined age data and textural observations provide unambiguous evidence that ejecta from the Chicxulub impact formed the global K-Pg boundary layer. These data cannot be explained by the alternative scenario that the Chicxulub impact occurred ~. 300. ka prior to the K-Pg boundary. © 2011 Elsevier B.V..
1159.
Upper Cretaceous Ostracod biostratigraphy of the CCSD SK-1(south) borehole, Songliao Basin (in Chinese with English abstract); [松辽盆地松科1井南孔晚白垩世介形类生物地层]
Acta Palaeontolgica Sinica,
50
(3)
330-343
2011
1158.
Vesiculation and microlite crystallization induced by decompression: A case study of the 1991-1995 Mt Unzen eruption (Japan)
Journal of Petrology,
52
(7-8)
1469-1492
2011
ISSN: 00223530
Publisher: Oxford University Press
Keywords:▾
amphibole; chemical composition; decompression; glass; magma; nucleation; oxide; plagioclase; pressure; pyroxene; volcanic rock, Japan; Kyushu; Nagasaki [Kyushu]; Unzen Volcano
Abstract: ▾ Isothermal decompression experiments were performed to simulate magma ascent at Unzen volcano from the depths of magma storage to shallow crustal levels, corresponding to pressure decrease from 300 to 50 MPa. A partially crystallized synthetic rhyodacitic magma (representing equilibrium conditions at 850°C and 300 MPa) was used as a starting material; this has a composition identical to the groundmass of Unzen rocks erupted in 1991-1995. Decompression rates were varied from 0·0002 to 20 MPa s-1. Experiments conducted with decompression rates ≥0·1 MPa s-1 were decompressed continuously; a multi-step decompression approach was used at decompression rates ≤0·1 MPa s-1. The experiments were fluid-saturated, either containing only water as a fluid component (H2O-bearing) or containing a water and carbon dioxide mixture (H2O + CO2; initial mole fraction of H2O in the fluid ~0·6). The experimental products of the H2O-bearing experiments consist of amphibole, pyroxenes, oxides and glass. Plagioclase microlites nucleated and grew only in experiments with the two lowest decompression rates of 0·0005 and 0·0002 MPa s-1. The length of those plagioclases is up to 200-250 μm, which is consistent with the size of plagioclase microlites observed in the natural samples. The experimental products of the H2O + CO2-bearing system are composed of pyroxenes, oxides, glass and plagioclase. Plagioclase microlites in the H2O + CO2-system were already present in the starting assemblage and grew to a maximum size of ~80 μm. Equilibrium concentrations of water in the residual glasses at the final pressure of 50 MPa are reached at decompression rates ≤1 MPa s-1 for the H2O + CO2-bearing system and ≤0·1 MPa s-1 for the H2O-bearing system. The bubble number density (BND) values range from 103·7 to 105·6 mm-3 in the H2O-bearing system and from 104·6 to 106·4 mm-3 in the H2O + CO2-bearing systems. In both systems, BND values decrease with decreasing decompression rate from 20 to 0·01 MPa s-1, and increase with decreasing decompression rates < 0·01 MPa s-1, which is interpreted to reflect predominant bubble growth and bubble nucleation, respectively. The onset of crystallization, observed from changes in the chemical composition of the residual melt, occurs at decompression rates < 0·1 MPa s-1. At the lowest decompression rate (0·0002 MPa s-1) the chemical composition of the residual melt in the H2O + CO2-bearing system becomes similar to the natural matrix glass composition. There is no significant variation of the microlite number density (MND) value as a function of the decompression rate. The MND values for plagioclases-only range from 105·4 to 105·7 mm-3, whereas the MND values for the other phases range from 105·3 to 105·9 mm-3. Our experimental MNDPl values are in the range of those from natural samples (105-106 mm-3). We show that the size of microlites nucleating and crystallizing during decompression (plagioclase in our experimental dataset) is useful to constrain magma ascent rates at the onset of the crystallization of the corresponding phase. Based on the size of plagioclase microlites and on the composition of the residual melts, the average magma ascent rates of Unzen magmas in the pressure range 200 to 50 MPa is estimated to be 10-50 m h-1. © The Author 2010. Published by Oxford University Press. All rights reserved.
1157.
[English]
Effect of relative permeability characteristics and gas/water flow on gas-hydrate saturation distribution
Volume 5
,
Page 3797-3810
Publisher
Society of Petroleum Engineers (SPE)
2011
University of Texas at Austin, United StatesKeywords:▾
Flow of water; Gas permeability; Gases; Grain size and shape; Hydration; Methane; Sediments, Capillary entry pressure; Gas hydrate saturations; Gas hydrate stability zones; Grain size distribution; Hydrate bearing sediments; Relative permeability; Relative permeability curves; Residual gas saturation, Gas hydrates
ISBN:
9781618392657
1156.
Theoretical Basis, Research Advancement and Prospects of Cyclostratigraphy (in Chinese with English abstract);[旋回地层学理论基础、研究进展和展望]
Earth Science-Journal of China University of Geosciences,
36
(03)
409-428
2011
1155.
[English]
Hotspot: The Snake River geothermal drilling project - An overview
Volume 35 2
,
Page 995-1003
2011
Department of Geology, Utah State University, Logan, UT, United States; Department of Geological Sciences, Brigham Young University, Provo, UT, United States; Department of Physics, University of Alberta, Edmonton, AB, Canada; Center for Geophysical Investigation of the Shallow Subsurface, Boise State University, Boise, ID, United States; Roy Huffington Department of Earth Sciences, Southern Methodist University, Dallas, TX, United States; US Geological Survey, Menlo Park, CA, United StatesISBN:
9781618394828
1154.
[English]
Observations of fault damage zones at reservoir depths
2011
Stanford University, Stanford, CA, United States; Conoco Phillips, Houston, TX, United States1153.
[English]
Project hotspot: Insight into the subsurface stratigraphy and geothermal potential of the snake river plain
Volume 35 2
,
Page 967 – 971
2011
ISBN:
978-161839482-8
1152.
[English]
The Iceland Deep Drilling Project (IDDP): Planning for the second deep well at Reykjanes
Volume 35 1
,
Page 347-354
2011
HS Orka hf, Reykjanesbaer, Iceland; Department of Earth Sciences, University of California, Riverside, CA, United States; ISOR, Iceland GeoSurvey, Reykjavík, Iceland; Landsvirkjun, Reykjavik, IcelandISBN:
9781618394828
1151.
High resolution reflection seismic investigations for defining ICDP drilling sites in the Scandinavian Caledonides
Publisher
AGH University of Science and Technology
,
Krakow, Poland
2011
1150.
Multicellular algae from lower Proterozoic (2.45 Ga) weathering crusts of the Kola Peninsula
,
Instruments, Methods, and Missions for Astrobiology XIV
Volume8152
,
Page 50--59
SPIE
2011
1149.
Melt in the impact breccias from the Eyreville drill cores, Chesapeake Bay impact structure, USA
Meteoritics and Planetary Science,
46
(3)
396-430
2011
Abstract: ▾ The center of the 35.3Ma Chesapeake Bay impact structure (85km diameter) was drilled during 2005/2006 in an ICDP-USGS drilling project. The Eyreville drill cores include polymict impact breccias and associated rocks (1397-1551m depth). Tens of melt particles from these impactites were studied by optical and electron microscopy, electron microprobe, and microRaman spectroscopy, and classified into six groups: m1-clear or brownish melt, m2-brownish melt altered to phyllosilicates, m3-colorless silica melt, m4-melt with pyroxene and plagioclase crystallites, m5-dark brown melt, and m6-melt with globular texture. These melt types have partly overlapping major element abundances, and large compositional variations due to the presence of schlieren, poorly mixed melt phases, partly digested clasts, and variable crystallization and alteration. The different melt types also vary in their abundance with depth in the drill core. Based on the chemical data, mixing calculations were performed to determine possible precursors of these melt particles. The calculations suggest that most melt types formed mainly from the thick sedimentary section of the target sequence (mainly the Potomac Formation), but an additional crystalline basement (schist/gneiss) precursor is likely for the most abundant melt types m2 and m5. Sedimentary rocks with compositions similar to those of the melt particles are present among the Eyreville core samples. Therefore, sedimentary target rocks were the main precursor of the Eyreville melt particles. However, the composition of the melt particles is not only the result of the precursor composition but also the result of changes during melting and solidification, as well as postimpact alteration, which must also be considered. The variability of the melt particle compositions reflects the variety of target rocks and indicates that there was no uniform melt source. Original heterogeneities, resulting from melting of different target rocks, may be preserved in impactites of some large impact structures that formed in volatile-rich targets, because no large melt body exists, in which homogenization would have taken place. © The Meteoritical Society, 2011.
1148.
Thermal properties of rocks of the borehole Yaxcopoil-1 (Impact Crater Chicxulub, Mexico)
Geophysical Journal International,
184
(2)
729-745
2011
Abstract: ▾ The results of thermal property measurements on cores from the scientific well Yaxcopoil-1 (1511 m in depth) drilled in the Chicxulub impact structure (Mexico) are described. The thermal conductivity, thermal diffusivity, volumetric heat capacity, thermal anisotropy coefficient, thermal heterogeneity factor, and, in addition, porosity and density were measured on 451 dry and water-saturated cores from the depth interval of 404-1511 m. The acoustic velocities were determined on a subgroup of representative samples. Significant vertical short- and long-scale variations of physical properties related to the grade of shock-thermal metamorphism and correlations between thermal and other physical properties are established. Rocks of the post-impact and impact complexes differ significantly in heterogeneity demonstrating that the impact complex has larger micro- heterogeneity on sample scale. The pre-impact rocks differ essentially from the impact and post-impact rocks in the thermal conductivity, thermal diffusivity, density and porosity. The thermal anisotropy of rocks of all structural-lithological complexes is very low (K = 1.02 ... 1.08), which is similar to the situation in the Puchezh-Katunk and Ries impact structures. Correlations are established between the thermal conductivity and elastic wave velocities measured in laboratory. For limestone-calcarenites, the thermal conductivity (λ) can be calculated from the compressional wave velocity (Vp) using the formula λ= 0.346 Vp + 0.844, and for dolomite-anhydrites this relation has the form λ= 0.998 Vp + 1.163 [for λ in W (m K)-1 and Vp in km s-1]. These correlations are used for downscaling of the sonic velocities to the decimetre scale. The effective medium theory is applied to invert the matrix thermal conductivity and pore/crack geometry from the thermal conductivity measured on the studied samples. Representative experimental data on the thermal properties for all lithological groups encountered by the Yaxcopoil-1 well essentially extend an existing database on the thermal properties of rocks of impact structures and can be used for determination of the heat flow density, interpretation of temperature logging data, theoretical modelling of heat and mass transfer processes and constructing thermal models of the Chicxulub impact structure as well as for the lithological interpretation. The research results confirm the necessity of dense sampling for the thermal property measurements to obtain reliable results in petrophysical and geothermal investigations of impact structure formations. © 2010 The Authors Geophysical Journal International © 2010 RAS.
1147.
The PASADO core processing strategy - A proposed new protocol for sediment core treatment in multidisciplinary lake drilling projects
Sedimentary Geology,
239
(1-2)
104 – 115
2011
Keywords:▾
Argentina; Patagonia; Information retrieval systems; Lakes; Sedimentology; Well drilling; Argentina; Core processing; Core sampling; Core slicing; Drilling projects; Inner surfaces; Liner material; Multidisciplinary projects; New devices; New protocol; Off-the-shelf components; Patagonia; Research groups; Sampling campaigns; Sampling plans; Sampling procedures; Sampling process; Scanning data; Scientific drilling; Sediment classification; Sediment core; core logging; deep drilling; lake; partitioning; sampling; sediment core; Anoxic sediments
Abstract: ▾ Using the ICDP (International Continental Scientific Drilling Program) deep lake drilling expedition no. 5022 as an example, we describe core processing and sampling procedures as well as new tools developed for subsampling. A manual core splitter is presented that is (1) mobile, (2) able to cut plastic core liners lengthwise without producing swarf of liner material and (3) consists of off-the-shelf components. In order to improve the sampling of sediment cores, a new device, the core sampling assembly (CSA), was developed that meets the following targets: (1) the partitioning of the sediment into discs of equal thickness is fast and precise, (2) disturbed sediment at the inner surface of the liner is discarded during this sampling process, (3) usage of the available sediment is optimised, (4) subsamples are volumetric and oriented, and (5) identical subsamples are taken. The CSA can be applied to D-shaped split sediment cores of any diameter and consists of a divider and a D-shaped scoop. The sampling plan applied for ICDP expedition 5022 is illustrated and may be used as a guideline for planning the efficient partitioning of sediment amongst different lake research groups involved in multidisciplinary projects. For every subsample, the use of quality flags is suggested (1) to document the sample condition, (2) to give a first sediment classification and (3) to guarantee a precise adjustment of logging and scanning data with data determined on individual samples. Based on this, we propose a protocol that might be applied across lake drilling projects in order to facilitate planning and documentation of sampling campaigns and to ensure a better comparability of results. © 2011 Elsevier B.V.
1146.
Seasonal contributions of catchment weathering and eolian dust to river water chemistry, northeastern Tibetan Plateau: Chemical and Sr isotopic constraints
Journal of Geophysical Research: Earth Surface,
116
(4)
2011
ISSN: 21699011
Publisher: Blackwell Publishing Ltd
Keywords:▾
Buha River; China; Qinghai; Qinghai-Xizang Plateau; carbonate; catchment; groundwater; high temperature; monsoon; rainfall; river water; seasonal variation; strontium isotope; water chemistry; weathering
Abstract: ▾ River waters collected weekly over the whole year of 2007 from the Buha River draining to Lake Qinghai on the northeastern Tibetan Plateau were analyzed for major ions and Sr isotopes. Dissolved loads in the river exhibit distinct seasonal variability in major cation ratios and Sr isotopes over the 1 year period, reflecting seasonal differences in relative inputs from various sources and weathering reactions in the catchment. Distinct geochemical signatures suggest that eolian dust may affect river water chemistry significantly, resulting in a twofold increase influx of dissolved loads during spring relative to winter. It is noticeable that both the lowest and the highest 87Sr/86Sr values of the Buha River waters occurred in the monsoon season, indicating a sensitive response of carbonate versus silicate weathering sources to hydrological forcing on a seasonal basis. A significant decrease in Na/cation, together with lower Sr isotope ratios, is consistent with a greater proportion f carbonate weathering relative to silicate weathering in the early monsoon season. High temperature and increased rainfall during the peak of the monsoon facilitate an increased proportion of ions derived from silicates, partly from groundwaters, to river water. In other seasons, elemental and 87Sr/86Sr ratios vary much less, indicating a constant ratio of silicate to carbonate weathering, consistent with limited variation in discharge. Our results highlight that in a semiarid region where climatic conditions vary seasonally, in addition to silicate and carbonate contributions, supply from eolian dust may also play a significant role in controlling seasonal variations in chemistry of river waters. Copyright 2011 by the American Geophysical Union.
1145.
Southern hemisphere tropical climate over the past 145ka: Results of the Lake Malawi Scientific Drilling Project, East Africa
Palaeogeography, Palaeoclimatology, Palaeoecology,
303
(1-4)
1-2
2011
ISSN: 00310182