All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
1269.
The Towuti drilling project: Paleoenvironments, biological evolution, and geomicrobiology of a tropical pacific lake
Scientific Drilling,
21
(14)
68 – 71
2012
ISSN: 18163459
Publisher: Copernicus GmbH
Keywords:▾
Biology; Climate change; Drilling; Microbiology; Tectonics; Biological evolution; Climate variability; Continental scientific drillings; Environmental change; International researches; Limnological system; Scientific drilling; Tropical Western Pacific; Lakes
Abstract: ▾ The Towuti Drilling Project (TDP) is an international research program, whose goal is to understand long-term environmental and climatic change in the tropical western Pacific, the impacts of geological and environmental changes on the biological evolution of aquatic taxa, and the geomicrobiology and biogeochemistry of metal-rich, ultramafic-hosted lake sediments through the scientific drilling of Lake Towuti, southern Sulawesi, Indonesia. Lake Towuti is a large tectonic lake at the downstream end of the Malili lake system, a chain of five highly biodiverse lakes that are among the oldest lakes in Southeast Asia. In 2015 we carried out a scientific drilling program on Lake Towuti using the International Continental Scientific Drilling Program (ICDP) Deep Lakes Drilling System (DLDS). We recovered a total of ~ 1018m of core from 11 drilling sites with water depths ranging from 156 to 200 m. Recovery averaged 91.7 %, and the maximum drilling depth was 175m below the lake floor, penetrating the entire sedimentary infill of the basin. Initial data from core and borehole logging indicate that these cores record the evolution of a highly dynamic tectonic and limnological system, with clear indications of orbital-scale climate variability during the mid- to late Pleistocene. © Author(s) 2016.
1268.
The space and time complexity of chaotic mixing of silicate melts: Implications for igneous petrology
Lithos,
155326-340
2012
ISSN: 00244937Keywords:▾
computer simulation; experimental study; felsic rock; fluid dynamics; fractionation; high temperature; igneous intrusion; laminar flow; mafic rock; mixing; petrology; Reynolds number; silicate melt
Abstract: ▾ We present new experimental results on the study of the space and time modulation of compositional fields during chaotic mixing between mafic and felsic silicate melts. The experimental strategy was planned using numerical simulations performed using the experimental geometry. These mixing experiments were performed using a recently developed experimental apparatus, which is capable of mixing high-viscosity silicate melts at high temperatures and under precisely controlled conditions of fluid-dynamics and strain. The compositional variability produced by the mixing process was investigated both along linear analytical transects and on high-resolution 2D X-ray maps, covering the mixing patterns.Our results indicate that chaotic flow fields represent very powerful dynamics to blend silicate melts, even under laminar fluid dynamic conditions (Reynolds number ca. 10-7) and for dissimilar melts with high viscosity ratios (on the order of 103). The repetition of stretching and folding processes between the two melts induced a strong increase of contact interfaces thus favoring efficient chemical exchanges. As a result the initial mafic composition is no longer detectable in the mixing system after ca. 2h (i.e. the duration of the experiment). A further important result is the observation of highly non-linear patterns in inter-elemental plots produced by the onset of diffusive fractionation processes. This is contrary to common thinking that magma mixing should always produce linear trends between pairs of chemical elements.A new measure, the "concentration variance", is proposed to quantify chemical element mobility during the mixing process. This measure is statistically robust and can be quantitatively used to measure chemical element mobility independently of the geometry in which the compositional variation (i.e. transects, areas, etc.) is embedded or the local strain history of the mingling.Our results highlight concentration variance as a robust probe of the as yet poorly-understood processes involved in the common petrological process of magma mixing. © 2012 Elsevier B.V.
1267.
The role of barriers and gradients in differentiation processes of pyrgulinid microgastropods of Lake Ohrid
Hydrobiologia,
682
(1)
61 – 73
2012
ISSN: 15735117Keywords:▾
Lake Ohrid; algae; Caenogastropoda; Chara; Gastropoda; Hydrobiidae; Invertebrata; Lonchocarpus glaucifolius; alga; allopatry; barrier (equipment); bathymetric survey; benthos; gastropod; genetic analysis; genetic structure; morphometry; parapatry; phenotypic plasticity; phylogeography; speciation (biology)
Abstract: ▾ Ancient Lake Ohrid is characterized by vertical (bathymetrical) zones within the lake, presumably promoting allopatric speciation due to barriers or parapatric speciation along gradients. Examples within the lake include the belt of Chara algae as well as the shell zone, both presumably impeding migrations of benthic invertebrates. Three potential cases of vertical differentiation leading to distinct depth forms have been reported for the gastropod subfamily Pyrgulinae (Caenogastropoda: Hydrobiidae): Ginaia munda ssp., Macedopyrgula spp. and Ochridopyrgulamacedonica ssp. Based on DNA data of the COI gene from a total of 145 specimens, this article aims at investigating the vertical differentiation within these depth forms and thus patterns of speciation in Lake Ohrid. An initial morphometric analysis showed a clear correlation of shell shape and collecting depth for Ginaia munda ssp. and Macedopyrgula spp. This morphological trend is largely reflected in the genetic structure of the respective taxa. The data presented here indicate the existence of strong gradients of abiotic and biotic factors in Lake Ohrid rather than distinct barriers. Therefore, parapatric speciation may be the predominant form of differentiation of benthic invertebrates in the lake. Incomplete lineage sorting, hybridization and phenotypic plasticity possibly caused by epigenetic mechanisms are discussed as possible reasons for the incongruence between geno- and phenotype observed in few specimens of Ginaia munda ssp. and Macedopyrgula spp. For the third taxon, Ochridopyrgulamacedonica ssp., morphometric and genetic analyses revealed only weak support for the previously proposed depth forms. However, a horizontal differentiation of lake and spring populations was revealed instead, and parapatric and allopatric differentiations are discussed in this taxon. © 2011 Springer Science+Business Media B.V.
1266.
The ICDP Snake River Geothermal Drilling Project: Preliminary overview of borehole geophysics
Transactions - Geothermal Resources Council,
36 21017-1022
2012
ISSN: 01935933ISBN:
9781622764341
Abstract: ▾ Hotspot: The Snake River Geothermal Drilling Project was undertaken to better understand the geothermal systems in three locations across the Snake River Plain with varying geological and hydrological structure. An extensive series of standard and specialized geophysical logs were obtained in each of the wells. Hydrogen-index neutron and γ-γ density logs employing active sources were deployed through the drill string, and although not fully calibrated for such a situation do provide semi-quantitative information related to the 'stratigraphy' of the basalt flows and on the existence of alteration minerals. Electrical resistivity logs highlight the existence of some fracture and mineralized zones. Magnetic susceptibility together with the vector magnetic field measurements display substantial variations that, in combination with laboratory measurements, may provide a tool for tracking magnetic field reversals along the borehole. Full waveform sonic logs highlight the variations in compressional and shear velocity along the borehole. These, together with the high resolution borehole seismic measurements display changes with depth that are not yet understood. The borehole seismic measurements indicate that seismic arrivals are obtained at depth in the formations and that strong seismic reflections are produced at lithological contacts seen in the corresponding core logging. Finally, oriented ultrasonic borehole televiewer images were obtained over most of the wells and these correlate well with the nearly 6 km of core obtained. This good image log to core correlations, particularly with regards to drilling induced breakouts and tensile borehole and core fractures will allow for confident estimates of stress directions and or placing constraints on stress magnitudes. Such correlations will be used to orient in core orientation giving information useful in hydrological assessments, paleomagnetic dating, and structural volcanology.
1265.
The effects of direct current and alternating current on the magnetization rate of shale (in Chinese); 直流场和交变场对泥岩磁化率的影响
Quaternary Sciences,
32
(4)
635-640
2012
1264.
The annual particle cycle in Lake Van (Turkey)
Palaeogeography, Palaeoclimatology, Palaeoecology,
333-334148-159
2012
ISSN: 00310182Keywords:▾
calcium carbonate; concentration (composition); continental shelf; decadal variation; lacustrine deposit; oxygen; paleoenvironment; precipitation (climatology); remote sensing; river discharge; runoff; satellite data; sediment chemistry; sediment core; sediment trap; snowmelt; suspended particulate matter; time series; turbidity; water column; water temperature, Lake Van; Turkey
Abstract: ▾ The varved sediments of Lake Van provide a high-quality continental archive of seasonal to decadal-scale climate variability. In order to read the natural record, modern varve formation was studied on the basis of (1) remotely-sensed total suspended-matter (TSM rs) concentrations; (2) time-series of particle flux and water temperatures; and (3) turbidity, temperature, and oxygen profiles. TSM rs, validated by contemporaneous water-column sampling, shows great temporal and lateral variations (whitings and turbidity plumes). From 2006 to 2009, sequential sediment traps recorded high particle fluxes during spring and fall, medium fluxes during summer, and almost zero flux during winter. The mean total mass flux of 403mgm -2day -1 comprised 33% (seasonally up to 67%) calcium carbonate, 7% aquatic organic matter, 6% biogenic opal, and 54% detrital minerals. The CaCO 3 fluxes are controlled by river discharge (precipitation and snowmelt) during spring, by high productivity during summer, and by river discharge (precipitation before snowfall starts) and mixing during fall. In November 2007, an anomalously high CaCO 3 flux occurred as a result of a warm water surface supersaturated with calcite coinciding with an anomalous runoff event. The results demonstrate that the couplets of light and dark laminae in the short sediment cores are true varves representing spring-summer-fall and winter conditions, respectively. Consequently, varve formation can be linked to the seasonal climate pattern, providing a calibration that can be used to interpret the partially varved paleo-record of Lake Van and related environmental processes. © 2012 Elsevier B.V.
1263.
Temporal and spatial corridors of Homo sapiens sapiens population dynamics during the Late Pleistocene and early Holocene
Quaternary International,
2741 – 4
2012
ISSN: 10406182Keywords:▾
Homo sapiens
1262.
Study on meter-scale cycles of the Lower Cretaceous Quantou Formation in SK-1 well (in Chinese with English abstract);[SK-1井下白垩统泉头组米级旋回研究]
Lithologic Reservoirs,
24
(06)
38-42
2012
1261.
Mineral-templated growth of natural graphite films
Geochimica et Cosmochimica Acta,
83252--262
2012
1260.
Interplay between the Westerlies and Asian monsoon recorded in Lake Qinghai sediments since 32 ka
Scientific Reports,
2
2012
ISSN: 20452322Abstract: ▾ Two atmospheric circulation systems, the mid-latitude Westerlies and the Asian summer monsoon (ASM), play key roles in northern-hemisphere climatic changes. However, the variability of the Westerlies in Asia and their relationship to the ASM remain unclear. Here, we present the longest and highest-resolution drill core from Lake Qinghai on the northeastern Tibetan Plateau (TP), which uniquely records the variability of both the Westerlies and the ASM since 32ĝ€...ka, reflecting the interplay of these two systems. These records document the anti-phase relationship of the Westerlies and the ASM for both glacial-interglacial and glacial millennial timescales. During the last glaciation, the influence of the Westerlies dominated; prominent dust-rich intervals, correlated with Heinrich events, reflect intensified Westerlies linked to northern high-latitude climate. During the Holocene, the dominant ASM circulation, punctuated by weak events, indicates linkages of the ASM to orbital forcing, North Atlantic abrupt events, and perhaps solar activity changes.
1259.
Major ion geochemistry of shallow groundwater in the Qinghai Lake catchment, NE Qinghai-Tibet Plateau
Environmental Earth Sciences,
67
(5)
1331 – 1344
2012
ISSN: 18666299Keywords:▾
China; Qinghai; Qinghai Lake; Carbonate minerals; Carbonation; Catchments; Chlorine compounds; Dissolution; Groundwater; Groundwater pollution; Gypsum; Hydrochemistry; Lakes; Runoff; Weathering; Carbonate weathering; Evaporite dissolution; Fresh Water; Ground water table; Groundwater consumption; Hydrochemical process; Hydrochemicals; Hydrogeochemical process; Ion concentrations; Ion exchange reactions; Low water; Qinghai Lake; Qinghai Tibet plateau; Shallow groundwater; Silicate weathering; Total dissolved solids; hydrogeochemistry; ion exchange; sampling; shallow water; solute; water table; water temperature; Groundwater geochemistry
Abstract: ▾ Conventional hydrochemical techniques and statistical analyses were applied to better understand the solute geochemistry and the hydrochemical process of shallow groundwater in the Qinghai Lake catchment. Shallow groundwater in the Qinghai Lake catchment is slightly alkaline, and is characterized by a high ion concentrations and low water temperature. The total dissolved solids (TDS) in most of the samples are <1,000 mg/L, i. e. fresh water and depend mainly on the concentration of SO 4 2-, Cl - and Na +. Groundwater table is influenced directly by the residents' groundwater consumption. Most of the groundwaters in the Qinghai Lake catchment belong to the Ca 2+(Na +) -HCO 3 - type, while the Qinghai Lake, part of the Buha (BHR) and the Lake Side (LS) samples belong to the Na +-Cl - type. The groundwater is oversaturated with respect to aragonite, calcite and dolomite, but not to magnesite and gypsum. Solutes are mainly derived from strong evaporite dissolution in Daotang, BHR and LS samples and from strong carbonate weathering in Hargai and Shaliu samples. Carbonate weathering is stronger than evaporite dissolution with weak silicate weathering in the Qinghai Lake catchment. Carbonate weathering, ion exchange reaction and precipitation are the major hydrogeochemical processes responsible for the solutes in the groundwater in the Qinghai Lake catchment. Most of the shallow groundwaters are suitable for drinking. More attention should be paid to the potential pollution of nitrate, chloride and sulfide in shallow groundwater in the future. © 2012 Springer-Verlag.
1258.
Assessment of purification and contamination correction methods for analysing the oxygen isotope composition from biogenic silica
Chemical Geology,
300-301185-199
2012
ISSN: 00092541Keywords:▾
Diatoms; El'gygytgyn; ICP-OES; Species-effect; XRF, Aluminum; Emission spectroscopy; Energy dispersive spectroscopy; Inductively coupled plasma; Isotopes; Lakes; Oxygen; Phytoplankton; Rating; Silica, Contamination, assessment method; biogenic material; biomonitoring; error correction; inductively coupled plasma method; isotopic composition; lake pollution; mass balance; oxygen isotope; pollutant transport; purification; silica; X-ray spectroscopy, Chukchi; Elgygytgyn Lake; Russian Federation, Bacillariophyta; Cyclotella ocellata; Pliocaenicus
Abstract: ▾ Mineral particles and other contaminants cause a serious and undesirable shift in δ 18O values of biogenic silica and should be removed prior to isotope analysis. This problem is particularly significant in the fraction containing clay particles and therefore the fraction <10μm is generally avoided. Here, we present an updated preparation protocol for the <10μm fraction based on known methods, developed using test material from short cores of Lake El'gygytgyn, NE Russia. New contamination assessment and correction techniques are discussed. Best results (low initial weight/high precision and throughput rate) for the <10μm fraction were achieved using geochemical mass-balancing and determining the "percentage of contamination" by analysing the sample's and end-member's Al 2O 3 with improved Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and Energy-Dispersive X-ray Spectroscopy (EDS) protocols or by determining the factor for calculating the percentage of contamination from the Al 2O 3 percentage of clay assemblages. Despite using small initial weights for ICP-OES (10mg) and EDS analysis (<0.5mg) a sufficiently high precision (for low Al 2O 3 percentages between 0.1 and 1.5%) could be achieved.For the >10μm fraction, point-counting under the light microscope was the preferred option. The different size-fractions from Lake El'gygytgyn samples show a distinct and significantly different species composition (average counts: <10μm: >90% Cyclotella ocellata complex; >10μm: >60% Pliocaenicus seczkinae). Differences in the oxygen isotope composition of these different size fractions could be explained by a species-effect on the δ 18O values. However, this species-effect disappeared after the correction (avg δ 18O <10μm: 19.8±0.6‰; >10μm: 19.8±0.4‰). By comparing these δ 18O values with additional recent water samples, an average 1000 ln α of 39.6‰ for Lake El'gygytgyn sub-recent diatoms was calculated. This "tool-kit" provides support for the presented improved contamination assessment and corrections and allows utilising smaller initial weight (app. 10mg) and small fractions (<10μm) for gaining corrected, higher resolution δ 18O records. © 2012 Elsevier B.V..
1257.
Correlation of clayey gouge in a surface exposure of serpentinite in the San Andreas Fault with gouge from the San Andreas Fault Observatory at Depth (SAFOD)
Journal of Structural Geology,
3851-60
2012
ISSN: 01918141Keywords:▾
Coast range ophiolites; Metasomatic reactions; SAFOD; San Andreas fault; Serpentinite; Smectite clays, Buildings; Clay minerals; Core drilling; Magnesium; Observatories, Strike-slip faults, correlation; creep; fault gouge; fault zone; metasomatism; ophiolite; outcrop; San Andreas Fault; sedimentary rock; serpentinite; smectite; tectonic setting
Abstract: ▾ Magnesium-rich clayey gouge similar to that comprising the two actively creeping strands of the San Andreas Fault in drill core from the San Andreas Fault Observatory at Depth (SAFOD) has been identified in a nearby outcrop of serpentinite within the fault zone at Nelson Creek. Each occurrence of the gouge consists of porphyroclasts of serpentinite and sedimentary rocks dispersed in a fine-grained, foliated matrix of Mg-rich smectitic clays. The clay minerals in all three gouges are interpreted to be the product of fluid-assisted, shear-enhanced reactions between quartzofeldspathic wall rocks and serpentinite that was tectonically entrained in the fault from a source in the Coast Range Ophiolite. We infer that the gouge at Nelson Creek connects to one or both of the gouge zones in the SAFOD core, and that similar gouge may occur at depths in between. The special significance of the outcrop is that it preserves the early stages of mineral reactions that are greatly advanced at depth, and it confirms the involvement of serpentinite and the Mg-rich phyllosilicate minerals that replace it in promoting creep along the central San Andreas Fault. © 2011.
1256.
Contributions of gamma-ray spectrometry to terrestrial impact crater studies: The example of Serra da Cangalha, northeastern Brazil
Geophysical Research Letters,
39
(4)
2012
Abstract: ▾ Several geophysical methods have been used for decades for the identification and exploration of impact craters. Most of them are based on seismic, potential fields and electrical data, focusing on exploration of anomalies caused by changes in physical properties or by structures associated with the formation of the crater. Gamma-ray spectrometry is usually not mentioned among the geophysical methods employed in crater studies, although it is known that impact cratering processes cause a number of physical/chemical changes in the country rocks. These changes include the remobilization of hydrothermal fluids which directly modify the composition of target rocks and, subsidiarily, of soils related to these rocks. Therefore, the distribution of radioactive elements K, Th and U has the potential to map such modifications. We present the analysis of gamma-ray signatures at the Serra da Cangalha impact structure, located in northeastern Brazil, using methods for enhancing K anomalies and also the overall gamma-ray signatures. These results provide valuable information on the distinct zones within the crater and might contribute to the understanding of hydrothermal enrichment processes produced as a result of the impact event. Copyright 2012 by the American Geophysical Union.
1255.
Compositional diversity of Mauna Kea shield lavas recovered by the Hawaii Scientific Drilling Project: Inferences on source lithology, magma supply, and the role of multiple volcanoes
Geochemistry, Geophysics, Geosystems,
13
(3)
2012
ISSN: 15252027
Publisher: Blackwell Publishing Ltd
Keywords:▾
Hawaii [(ISL) Hawaiian Islands]; Hawaii [United States]; Hawaiian Islands; Mauna Kea; United States; Glass; Lead; Lithology; Olivine; Hawaiian volcanism; Hyaloclastites; Incompatible element; Isotopic ratios; Major and trace elements; Mantle plume; Mantle source; Mauna Kea; Ni content; Scientific drilling; geochemistry; isotopic ratio; lava; lead isotope; lithology; magma; mantle plume; mantle source; olivine; partitioning; peridotite; shield volcano; trace element; volcanism; Volcanoes
Abstract: ▾ [1] The final Stage (Phase-2) of the Hawaii Scientific Drilling Project (HSDP) recovered 408 m of basaltic core (3098-3506 mbsl) attributed to Mauna Kea volcano. We determined the major and trace element composition of 40 samples from this core. Our results show that the incompatible element ratios, such as Zr/Nb, which are correlated with Pb isotopic ratios, are more variable in the lower 408 m of Mauna Kea shield lavas than in the overlying 2855 m (~450 ka). We argue that this geochemical diversity was present in the mantle source of Mauna Kea shield lavas and does not require the inter-fingering of lavas from adjacent volcanoes. Because of uncertainties in Ni partitioning between olivine and melt and the wide range of Ni contents in peridotites, we show that all Mauna Kea lavas may have been derived from a peridotite source. We also obtained major and trace element compositions for 24 whole-rock clasts and hyaloclastites and 7 glasses from HSDP Phase-1 core between 1767 and 1808 mbs. These enigmatic lavas, previously recognized by the distinctive high CaO and K2O contents of their glasses, are also relatively enriched in highly incompatible trace elements. We show that this group of lavas have affinities with post-shield lavas and argue that they are a consequence of lower degrees of melting (~a factor of two) than other Mauna Kea shield lavas, thereby providing evidence that magma supply varied significantly during the growth of the Mauna Kea shield. Copyright 2012 by the American Geophysical Union.
1254.
Climatic change recorded in the sediments of the Chew Bahir basin, southern Ethiopia, during the last 45,000 years
Quaternary International,
27425-37
2012
ISSN: 10406182Keywords:▾
climate variation; lacustrine deposit; Last Glacial Maximum; paleoclimate; paleoenvironment; Younger Dryas, Ethiopia, Homo sapiens
Abstract: ▾ East African paleoenvironments are highly variable, marked by extreme fluctuations in moisture availability, which has far-reaching implications for the origin, evolution and dispersal of Homo sapiens in and beyond the region. This paper presents results from a pilot core from the Chew Bahir basin in southern Ethiopia that records the climatic history of the past 45 ka, with emphasis on the African Humid Period (AHP, ∼15-5 ka calBP). Geochemical, physical and biological indicators show that Chew Bahir responded to climatic fluctuations on millennial to centennial timescales, and to the precessional cycle, since the Last Glacial Maximum. Potassium content of the sediment appears to be a reliable proxy for aridity, showing that Chew Bahir reacted to the insolation-controlled humidity increase of the AHP with a remarkably abrupt onset and a gradual termination, framing a sharply defined arid phase (∼12.8-11.6 ka calBP) corresponding to the Younger Dryas chronozone. The Chew Bahir record correlates well with low- and high-latitude paleoclimate records, demonstrating that the site responded to regional and global climate changes. © 2012 Elsevier Ltd and INQUA.
1253.
Climate and environmental change in the Balkans over the last 17 ka recorded in sediments from Lake Prespa (Albania/F.Y.R. of Macedonia/Greece)
Quaternary International,
274122 – 135
2012
ISSN: 10406182Keywords:▾
Albania; Balkan; Greece; Lake Mikri Prespa; Macedonia [Greece]; Turkmenistan; climate conditions; climate variation; environmental change; geochemistry; Holocene; human activity; ice cap; lacustrine deposit; limnology; paleoclimate; paleoenvironment; sediment core; sedimentology; warming; water column; Younger Dryas
Abstract: ▾ This paper presents sedimentological, geochemical, and biological data from Lake Prespa (Albania/Former Yugoslav Republic of Macedonia/Greece). The 320 cm core sequence (Co1215) covers the last 17 ka calBP and reveals significant change in climate and environmental conditions on a local and regional scale. The sediment record suggests typical stadial conditions from 17.1 to 15.7 ka calBP, documented through low lake productivity, well-mixed conditions, and cold-resistant steppe catchment vegetation. Warming is indicated from 15.7 ka calBP with slightly increased in-lake productivity, gradual expansion of trees, and decreasing erosion through disappearance of local ice caps. Between 14.5 and 11.5 ka calBP relatively stable hydrological conditions are documented. The maximum in tree taxa percentages during the Bølling/Allerød interstadial (14.5-13.2 ka calBP) indicates increased temperatures and moisture availability, whereas the increase of cold-resistant open steppe vegetation taxa percentages during the Younger Dryas (13.2-11.5 ka calBP) is coupled with distinct colder and drier conditions. The Holocene sequence from 11.5 ka calBP indicates ice-free winters, stratification of the water column, a relatively high lake trophic level and dense vegetation cover over the catchment. A strong climate related impact on the limnology and physical parameters in Lake Prespa is documented around 8.2 ka through a significant decrease in productivity, enhanced mixing, strong decomposition and soil erosion, and a coeval expansion of herbs implying cool and dry climate conditions. Intensive human activity in the catchment is indicated from around 1.9 ka calBP. This multiproxy approach improves our understanding of short- and long-term climate fluctuations in this area and their impact on catchment dynamics, limnology, hydrology, and vegetation. © 2012 Elsevier Ltd and INQUA.
1252.
Clay fabrics in SAFOD core samples
Journal of Structural Geology,
43118-127
2012
ISSN: 01918141Keywords:▾
Clay fabrics; Clay particles; Fault rock; Fluid pressures; Intergranular pores; Micro fabric; Optical microscopes; Oriented matrix; Phyllosilicate; SAFOD; San Andreas fault; SEM observation; Synchrotron x ray diffraction; Synchrotron x rays; Transmission electron microscopy tem, Clay minerals; Optical microscopy; Scanning electron microscopy; Silicates; Strike-slip faults; Tectonics; Textures; Transmission electron microscopy; X ray diffraction, Core samples, clay mineral; core (planetary); fault gouge; fluid flow; petrofabric; phyllosilicate; porosity; San Andreas Fault; scanning electron microscopy; texture; transmission electron microscopy; X-ray diffraction
Abstract: ▾ With optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and synchrotron X-ray diffraction measurements, we analyzed clay microfabrics in ultracataclastic/gouge and cataclastic core samples obtained from the main bore hole of the San Andreas Fault observatory at depth (SAFOD). The analysis reveals a significant contrast between weak clay fabrics observed in the core samples with synchrotron X-ray fabric measurements and strong degree of preferred alignment for clay particles documented with the optical microscope. TEM and SEM observations also show distinct zones of locally aligned and randomly oriented clay minerals. The lack of a strong fabric may be attributed to randomly oriented matrix sheet silicates dominating the fault rocks. The presence of weak fabrics in intensely strained ultracataclasites/fault gouges is attributed to 1) newly formed clay minerals that grew in many orientations, 2) folded and kinked clay minerals, and 3) clay particles that are wrapped around grains. In addition, the locally aligned clay particles may act as barriers to fluid flow, which in turn decrease porosity, expel intergranular pore fluids, and consequently, may increase fluid pressure. © 2012 Elsevier Ltd.
1251.
Chlorite-smectite clay minerals and fault behavior: New evidence from the San Andreas Fault Observatory at Depth (SAFOD) core
Lithosphere,
4
(3)
209-220
2012
ISSN: 19418264
Publisher: Geological Society of America
DOI:10.1130/L158.1
Keywords:▾
Creep; Friction; High resolution transmission electron microscopy; Observatories; Serpentine; Silicate minerals; Strike-slip faults; Structural geology; X ray diffraction, Brittle ductile transitions; Deformation zone; Effective normal stress; Frictional properties; Frictional strength; Mineral formation; Pore fluid pressure; San Andreas fault, Clay minerals, brittle deformation; chlorite; creep; fault displacement; fluid pressure; infiltration; mudstone; precipitation (chemistry); smectite, California; Parkfield; United States
Abstract: ▾ Segments of the modern San Andreas fault experience creep behavior, which is attributed to various factors, including (1) low values of effective normal stress, (2) elevated pore-fluid pressure, and (3) low frictional strength. The San Andreas Fault Observatory at Depth (SAFOD) drill hole in Parkfield, California, provides new insights into frictional properties by recognizing the importance of smectitic clay minerals, as demonstrated by analysis of mudrock and fault gouge samples from zones between 3186 and 3199 m and 3295 and 3313 m measured depths. X-ray diffraction (XRD) results show illite, chlorite, and mixed-layered illite-smectite and chlorite-smectite minerals in the faulted mudrock, whereas serpentine, Mg-rich smectite, and chlorite-smectite minerals are concentrated in the southwest deformation zone and the central deformation zone of the two actively creeping sections in the San Andreas fault. These rocks are abundantly coated by shiny clay mineral layers in some cases, reflecting mineral formation during creep. Secondary- and transmission-electron microscopy (SEM/TEM) and XRD studies of these slip surface coatings reveal thin films of neoformed chlorite-smectite phases, similar to previously described illite-smectite microscale precipitations. The abundance of chlorite-smectite minerals within fault rock of the SAFOD borehole significantly extends the potential role of mineralogic processes to depths up to 10 km, with cataclasis and fluid infiltration creating nucleation sites for neomineralization on displacement surfaces. We propose that localization of illitic to chloritic smectite clay minerals on slip surfaces from near the surface to the brittle-ductile transition promotes creep behavior of faults. © 2012 Geological Society of America.
1250.
Chemistry and thermometry of geothermal water from Mountain Home test well MH-2B S: Preliminary results
Transactions - Geothermal Resources Council,
36 1689-692
2012
ISSN: 01935933ISBN:
9781622764341
Abstract: ▾ A geothermal test well at Mountain Home AFB in southwestern Idaho encountered artesian flow of geothermal water from a depth of 1,745 m. Samples taken from the well head after 12 hours of flow had a pH of 9.59, and an electrical conductivity of 870 μS. The high pH suggests that the water is at equilibrium with weathered basalt at the measured temperature. The water is high in sulfate relative to chloride and bicarbonate, and high in sodium relative to calcium and magnesium, but has a TDS content of only 1,120 mg/L. Pyrite is probably the source of the sulfate. Deuterium and oxygen-18 levels are -88 and -3.2 per mil, respectively, suggesting that the water is old, not meteoric, and/or has undergone significant fractionation. Calculated equilibrium temperatures vary from ∼134°C to ∼154°C. The calculated temperatures are similar to those measured in the test well. The data suggest a potential electric-grade resource. Further work is in progress.
1249.
Characteristics and petroleum geologic significances of clay rims in sandstones of Mingshui Formation, well Songke 1, Songliao Basin
石油实验地质,
34
(6)
585-593
2012
1248.
Carbon isotopes in surface-sediment carbonates of modern Lake Qinghai (Qinghai-Tibet Plateau): Implications for lake evolution in arid areas
Chemical Geology,
300-30188 – 96
2012
ISSN: 00092541Keywords:▾
China; Qinghai; Qinghai Lake; Ostracoda; Animals; Anoxic sediments; Arid regions; Carbon; Carbon dioxide; Carbonates; Carbonation; Isotopes; Sedimentology; Arid area; Authigenic carbonates; Carbon isotopes; Carbon isotopic composition; Dissolved inorganic carbon; High altitude; Isotopic composition; Lake Qinghai; Lake waters; Ostracods; Qinghai Tibet plateau; Sediment water interface; Study areas; Water salinity; arid region; carbon isotope; carbonate sediment; dissolved inorganic carbon; isotopic composition; isotopic ratio; lacustrine deposit; ostracod; Lakes
Abstract: ▾ To further investigate the significance of carbon isotopes of lake carbonates in arid areas, we examined the carbon isotopic composition of ostracods, bulk carbonate, fine-grained carbonates, and associated water DIC (dissolved inorganic carbon) from Lake Qinghai and several small lakes and ponds surrounding Lake Qinghai. We obtained three major results. 1) The carbon isotopic compositions of ostracods, bulk carbonate, and fine-grained carbonates in the lakes and ponds are clearly correlated with water δ 13C DIC values, which vary with water salinity in the Lake Qinghai area. 2) The variation in the δ 13C DIC values of lake water is mainly controlled by CO 2 exchanges between the atmosphere and lake waters in the Lake Qinghai area. 3) Ostracods, bulk carbonate and fine-grained carbonates show consistent trends of isotopic composition in the study area, and the differences in carbon isotopic composition between authigenic carbonates and ostracods may be explained by the differences in carbon isotopic composition between the DIC of surface water and that of the water near to the sediment-water interface as well as the 'vital offsets' of ostracods.Our results suggest that variations in the δ 13C values of carbonates in Lake Qinghai and other lakes in this arid, high-altitude area are primarily controlled by the carbon-isotope ratios of the lake water DIC, which in turn are related to water salinity. Therefore, changes in carbonate δ 13C values may be used to indirectly indicate changes in water salinity in the Lake Qinghai area. © 2012 Elsevier B.V..
1247.
Carbon chain length distribution in n-alkyl lipids: A process for evaluating source inputs to Lake Qinghai
Organic Geochemistry,
5036 – 43
2012
ISSN: 01466380Keywords:▾
China; Qinghai; Qinghai Lake; Carbon; Hydrogen; Isotopes; Paraffins; Sedimentology; Sediments; Aquatic plants; Average length; Carbon chains; Carbon-chain length; Geochemical proxies; Hydrogen isotope; Isotopic information; Lake Qinghai; Lake sediments; Lake waters; n-Alkanes; Paleo-environment; Paleoclimate research; Surface sediments; alkane; carbon; fatty acid; geological record; hydrogen isotope; lacustrine deposit; lake water; paleoclimate; paleoenvironment; sediment chemistry; Lakes
Abstract: ▾ Lake sediments generally contain a mixture of terrestrial and aquatic source inputs, and determining the major inputs is important for understanding geological records in paleoenvironment and paleoclimate research. In this study we describe the distribution of n-alkanes and n-fatty acids (FAs) in representative modern plants from around Lake Qinghai. We found a significant difference in the average length of n-FA carbon chains (ACL Fa 16-32) in terrestrial (23.3) and aquatic plants (18.6). The results reveal that ACL Fa 16-32 may essentially serve as a proxy for evaluating the major source inputs to lake sediments. Assessment of surface sediments from the lake showed that the FAs originated from a mixture of inputs, with the aquatic source input predominant at most sites.Additionally, the δD values of sediment mid-chain n-acids (C 22) showed a relationship with the ACL Fa 16-32 proxy: an increased Fa ACL corresponded to more negative hydrogen isotope ratio values. We suggest that different sources should be considered and ACL Fa 16-32 could be a potential calibration proxy before using δD values to extract reliable isotopic information from lake water. More attention should be paid to source inputs and their relationship to other geochemical proxies in future studies of lake sediments. © 2012 Elsevier Ltd.
1246.
Boundary stratotype of the Cretaceous Qingshankouan stage in the Songliao Basin
Journal of Stratigraphy,
36
(3)
569-578
2012
1245.
Anti-collapse drilling fluids for the Cretaceous scientific drilling in Songliao basin, China: A case study
Applied Mechanics and Materials,
170-1731196-1201
2012
ISSN: 16609336Keywords:▾
Drilling contractors; Managed Pressure Drilling; Northeast China; Open process; Openhole; Scientific drilling; Shale formation; Songliao basin; Stuck pipe; Technical barriers; Technical challenges; Water invasion; Water sensitive; Wellbore; Wellbore stability, Building materials; Civil engineering; Core drilling; Oil field equipment; Oil fields; Shale, Drilling fluids
ISBN:
9783037854228
Abstract: ▾ CCSD-SK1 well was the first Cretaceous scientific drilling well in the world, locating in Songliao basin, Northeast China. It included main well (also called north well) and south well. This paper introduced the anti-collapse drilling fluid technology in main well where the desired continuous coring section was from 164.77 m to 1792.00 m. Continuous technical barriers challenged the intelligence of drilling engineers of this project. First, preserving the wellbore stability was the most critical aspect of continuous core drilling. From top to bottom, the unconsolidated sandstone in the Quaternary super stratum, the water sensitive shale in the Sifangtai group and upper stratum of the Nenjiang group, and the brittle shale of under stratum of the Nenjiang group increased the difficulty of anti-collapse drilling fluid technology. Water invasion into the shale formation often weakens the wellbore and causes problems such as wellbore collapse, shale destabilization and stuck pipe. Fluids should be designed to mitigate these shale problems. Secondly, the openhole strategy imposed the difficulty of maintaining wellbore stability in the second open process (from 245.00 m to the bottom). Finally, the total expense of the well was only one fifth ofsouth well, which was drilled by an oilfield drilling contractor. To overcome these technical challenges, not only different drilling fluid systems such as PAM drilling fluid, DFD-LG-CMC drilling fluid and DFD-NH4HPAN-SAKH drilling fluid were adopted separately, but also technology of feasible viscosity and managed pressure drilling were used. A total of 395 trips had been run in this Cretaceous scientific drilling well and no accidents even dangerous cases occurred. The experience of CCSD-SK1 (main well) explored a successful way of employing economic drilling fluid to preceding similar scientific drilling projects in similar shale formations. © (2012) Trans Tech Publications, Switzerland.