All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
994.
Native Dreissena freshwater mussels in the Balkans: In and out of ancient lakes
Biogeosciences,
7
(10)
3051 – 3065
2010
ISSN: 17264189Keywords:▾
Balkans; Lake Mikri Prespa; Lake Ohrid; Dreissena; Dreissena polymorpha; Dreissena stankovici; bivalve; extinction; freshwater environment; genetic analysis; historical perspective; native species; paleoecology; reconstruction; species diversity; sympatry; zoogeography
Abstract: ▾ The Balkans is a biogeographically highly diverse region and a worldwide hotspot of endemic freshwater diversity. A substantial part of this diversity is attributed to well recognized and potential ancient lakes in its southwestern part. However, despite considerable research efforts, faunal relationships among those lakes are not well understood. Therefore, genetic information from native representatives of the mussel genus Dreissena is here used to test the biogeographical zonation of the southwestern Balkans, to relate demographic changes to environmental changes, to assess the degree of eco-insularity, to reconstruct their evolutionary history, and to explore the potential of native taxa for becoming invasive. Phylogeographical and population genetic analyses indicate that most studied populations belong to two native species: D. presbensis (including the distinct genetic subgroup from Lake Ohrid, "D. stankoviciquot;) and D. blanci. In addition, the first confirmed record of invasive D. polymorpha in the southwestern Balkan is presented. The distribution of native Dreissena spp. generally coincides with the biogeographical zonations previously suggested based on fish data. However, there is disagreement on the assignment of the ancient lakes in the area to respective biogeographical regions. The data for Lake Ohrid are not conclusive. A closer biogeographical connection to lakes of the Vardar region and possibly the northern Ionian region is, however, suggested for Lake Prespa. The reconstruction of the evolutionary history of Dreissena spp. suggests that populations underwent demographic and spatial expansions in the recent past. Expansions started around 320 000-300 000 years ago in "D. stankovici", 160 000-140 000 years ago in D. blanci, and 110 000-70 000 years ago in D. presbensis. These time frames are discussed within the context of available paleogeological data for lakes Ohrid and Prespa. It is suggested that regional environmental changes may have had pronounced effects on the population histories of native Dreissena spp., though the high buffer capacity of Lake Ohrid may have lessened these effects in "D. stankovici". In addition, local events influencing individual lakes had very likely considerable effects on the demographic histories of Dreissena spp. as well. The observed patterns of immigration and emigration in and out of ancient lakes may suggest that limited gene flow enabled the survival of few isolated subpopulations and that later on eco-insularity (selective advantages of locally adopted groups) may have prevented excessive hybridization and sympatry of closely related taxa. As for the potential invasiveness of native Dreissena spp., the inferred spatial expansions are not human-mediated and all taxa still appear to be restricted to their native ranges. A concern, however, is that today D. presbensis and D. blanci also occur in artificial water bodies, and that invasive D. polymorpha has reached the area. © Author(s) 2010.
993.
New integrated data analyses software components
Scientific Drilling
(9)
30-31
2010
ISSN: 18168957
Publisher: Integrated Ocean Drilling Program
992.
Mudstone lithofacies in the Cretaceous Qingshankou Formation of Well Sk I, Songliao Basin, Northeastern China
China Mining Magazine,
19161-165
2010
991.
Amorphous material in SAFOD core samples (San Andreas Fault): Evidence for crush-origin pseudotachylytes?
Geophysical Research Letters,
37
(1)
2010
ISSN: 00948276Keywords:▾
Adjacent matrix; Amorphous phasis; matrix; Pseudotachylytes; San Andreas Fault; Silica content, Core samples; Grinding (comminution); Oxide minerals; Quartz; Scanning electron microscopy; Silica; Silicate minerals; Transmission electron microscopy, Amorphous materials, amorphous medium; borehole; chemical analysis; clast; feldspar; melting; San Andreas Fault; silica; slickenside; transmission electron microscopy
Abstract: ▾ Several types of amorphous material in ultracataclastic core samples recovered from 3194 m and 3294 m depth of the main bore hole of the San Andreas Fault Observatory at Depth are identified and described with transmission electron microscopy and scanning electron microscopy. We observed (1) amorphous material on a slickenside surface, (2) glassy bands contained in an ultracataclastic matrix and (3) amorphous rims surrounding quartz or feldspar clasts. Chemical analyses of the amorphous material reveal that silica content is slightly enriched or similar as in the adjacent matrix. We suggest that all amorphous material was formed by comminution of clasts (crush-origin pseudotachylytes) rather than by melting (melt-origin pseudotachylytes). The observed amorphous phases may act as lubricating layers that reduce friction in the San Andreas Fault. Copyright 2010 by the American Geophysical Union.
990.
Distribution, diversity and ecology of modern freshwater ostracodes (crustacea), and hydrochemical characteristics of Lago Petén Itzá, Guatemala
Journal of Limnology,
69
(1)
146 – 159
2010
ISSN: 11295767Abstract: ▾ We analyzed modern ostracode species assemblages and water column physico-chemical characteristics in Lago Péten Itzá, Guatemala. Lake waters are dominated by sulfate, bicarbonate, calcium and magnesium and display a total ion concentration of ~11 meq L-1. Eleven extant ostracode species were identified. We found higher abundances of living ostracodes, as well as relatively higher species richness (eight species) and biodiversity (H of 1.6) between the littoral zone and a water depth of <20 m. At water depths >40 m, these variables all decreased. The thermocline is located at a water depth of ~20-40 m. Cluster analysis revealed three water depth ranges in the lake of importance to ostracode distribution: 1) littoral zone (0.1-3 m), 2) water depths from the base of the littoral zone to the base of the thermocline (3-40 m), and 3) water depths below the thermocline (40-160 m). The assemblage Darwinula-Heterocypris-Pseudocandona-Strandesia is characteristic of waters <15 m. The Cypridopsis-Cytheridella-Limnocythere assemblage characterizes waters <40 m and Physocypria indicates waters >40 m. Ostracode taxa from Lago Petén Itzá show specific ecological preferences related to water depth and associated physico-chemical characteristics, thus illustrating the potential of ostracodes as indicators of lake level changes and hydrodynamics.
989.
Distribution of seismicity across strike-slip faults in California
Journal of Geophysical Research: Solid Earth,
115
(5)
2010
ISSN: 21699313
Publisher: Blackwell Publishing Ltd
Keywords:▾
earthquake trigger; normal fault; roughness; seismicity; strike-slip fault; earthquake damage; power law, California; United States; Parkfield
Abstract: ▾ The distribution of seismicity about strike-slip faults provides measurements of fault roughness and damage zone width. In California, seismicity decays with distance from strike-slip faults according to a power law -(1 + ×2/d2)-g/2. This scaling relation holds out to a fault-normal distance × of 3?6 km and is compatible with a ?rough fault loading? model in which the inner scale d measures the half width of a volumetric damage zone and the roll-off rate g is governed by stress variations due to fault roughness. According to Dieterich and Smith?s 2-D simulations, g approximates the fractal dimension of alongstrike roughness. Near-fault seismicity is more localized on faults in northern California (NoCal, d = 60 ± 20 m, g = 1.65 ± .05) than in southern California (SoCal, d = 220 ± 40 m, g = 1.16 ± .05). The Parkfield region has a damage zone half width (d = 120 ± 30 m) consistent with the SAFOD drilling estimate; its high roll-off rate (g = 2.30 ± .25) indicates a relatively flat roughness spectrum: k-1 versus k-2 for NoCal, k-3 for SoCal. Our damage zone widths (the first direct estimates averaged over the seismogenic layer) can be interpreted in terms of an across-strike ?fault core multiplicity? that is 1 in NoCal, 2 at Parkfield, and 3 in SoCal. The localization of seismicity near individual faults correlates with cumulative offset, seismic productivity, and aseismic slip, consistent with a model in which faults originate as branched networks with broad, multicore damage zones and evolve toward more localized, lineated features with low fault core multiplicity, thinner damage zones, and less seismic coupling. Our results suggest how earthquake triggering statistics might be modified by the presence of faults. Copyright 2010 by the American Geophysical Union.
988.
Distribution of Recent ostracod species in the Lake Qinghai area in northwestern China and its ecological significance
Ecological Indicators,
10
(4)
880 – 890
2010
ISSN: 1470160XKeywords:▾
China; Qinghai; Qinghai Lake; Caudata; Crustacea; Eucypris; Eurycypris pubera; Fabaeformiscandona; Herpetocypris reptans; Ilyocypris; Ostracoda; Paralimnocythere; Potamocypris smaragdina; Potamocypris villosa; Prionocypris; Animals; Climate change; Core drilling; Ecology; Salinity measurement; Stream flow; Associations; Cold regions; Crustacea; Drill core; Ecological characteristics; Ecological information; Northwestern China; Ostracoda; Paleolimnology; Species diversity; Water environments; Water salinity; abundance; climate change; community composition; Holarctic Region; lake water; ostracod; population distribution; salinity; species diversity; Lakes
Abstract: ▾ In order to interpret the climate-change data using the ecological characteristics of the ostracods from the drill cores in Lake Qinghai, the distribution of Recent ostracods was studied in Lake Qinghai area. A total of 34 species belonging to the Ostracoda class of Crustacea were collected from different bodies of water in the Lake Qinghai area, and the ecological information for Recent ostracod species was studied. Among these 34 species, Cypris pubera, Eucypris dulcifons, Ilyocypris sp. 1, Ilyocypris sp. 2, Fabaeformiscandona caudata, Fabaeformiscandona hyalina, Herpetocypris reptans, Prionocypris gansenensis, Potamocypris villosa, Potamocypris smaragdina, Paralimnocythere compressa and Subulacypris sp. were first reported by us in the Lake Qinghai area. Some of the species identified exhibited cosmopolitan distributions, at least in the Holarctic region, but P. gansenensis and Ilyocypris echinata appeared to be restricted to the cold regions in northwestern China. The ecological significance of the primary ostracod species in the Lake Qinghai area was described according to the observations made during our time in the field and according to data from a number of reports. Our results indicate that the species diversity and abundance of ostracods may be related to water salinity in the Lake Qinghai area. The ecological information for ostracods can be used to distinguish different water environments and types based on the characteristics of one species or of an assemblage of several species. © 2010 Elsevier Ltd. All rights reserved.
987.
Discussion on "Integrating borehole-breakout dimensions, strength criteria, and leak-off test results, to constrain the state of stress across the Chelungpu Fault, Taiwan"
Tectonophysics,
492
(1-4)
295-298
2010
ISSN: 00401951Abstract: ▾ The in-situ stress computations presented by Haimson et al. (2010) overestimated the maximum horizontal stress in the vicinity of the Chelungpu Fault, Taiwan. Our analyses from extended leak-off tests, drilling-induced tensile fractures, and Anderson's faulting theory show considerable lower values for the maximum horizontal stress. Our results suggest that closer to the ruptured fault, more SH is released, implying a strong earth crest in the shallower section, which is far away from the ruptured fault. However, it would require more detailed and intensive work in order to achieve an accurate interpretation of the in-situ stress in this region. © 2010 Elsevier B.V.
986.
Developments in gas hydrates
Oilfield Review,
22
(1)
18-33
2010
ISSN: 09231730Abstract: ▾ International efforts and advanced techniques are being used to characterize properties and distributions of gas hydrates, which are crystalline solids that resemble ice. The Minerals Management Service (MMS) of the US Department of the Interior has used seismic data, along with wellbore, geologic, geochemical and paleontological information, to assess large areas of the Gulf of Mexico, where pressure and temperature conditions are suitable for hydrate-stability conditions. The team members acquired and analyzed seismic data, selected drilling locations and conducted a 35-day drilling, coring and logging expedition covering several sites. A new program was initiated in 2002 from the Mallik field to conduct production testing of gas hydrates. The USGS has studied gas hydrate accumulations in the Alaska North Slope and estimates that they contain between 25.2 and 157.8 Tcf of undiscovered recoverable natural gas.
985.
Design, manufacture, and operation of a core barrel for the Iceland Deep Drilling Project (IDDP)
Scientific Drilling
(10)
40-45
2010
ISSN: 18168957Keywords:▾
Core barrel; Core tube data logger; Deep drilling; Design characteristics; Drill pipe connection; Formation temperature; Hydrothermally; Icelands; Inner Barrel; Production wells; Running-in; Science programs; Short periods; Spot coring; Super-critical; Transition zones, Design, Drill pipe
Abstract: ▾ The science program of the Iceland Deep Drilling Project (IDDP) requires as much core as possible in the transition zone to supercritical and inside the supercritical zone (>374°C), in the depth interval 2400-4500 m. The spot coring system selected has a 7 1/4″ (184.15 mm) OD at 10 m length and collects a 4″ (101.6 mm) diameter core using an 8 1/2″ (215.9 mm) OD core bit. It incorporates design characteristics, materials, clearances and bearings compatible with operation of the core barrel at temperatures as high as 600°C. Special attention was given to the volume of flushing which could be applied to the core barrel and through the bit while running in and out of the borehole and while coring. In November 2008 a successful spot coring test using the new core barrel was performed at 2800 m depth in the production well RN-17 B at Reykjanes, Iceland, where the formation temperature is 322°C. A 9.3-m hydrothermally altered hyaloclastite breccia was cored with 100% core recovery, in spite of it being highly fractured. A core tube data logger was also designed and placed inside the inner barrel to monitor the effectiveness of cooling. The temperature could be maintained at 100°C while coring, but it reached 170°C for a very short period while tripping in. The effective cooling is attributed to the high flush design and a top drive being employed, which allows circulation while tripping in or out, except for the very short time when a new drill pipe connection is being made.
984.
Cretaceous calcareous paleosols, pedogenetic characteristics and paleoenvironmental implications (in Chinese with English abstract);[白垩纪钙质古土壤的发生学特征及古环境意义]
Acta Pedologica Sinca,
47
(06)
1029-1038
2010
983.
Coniacian seismites: Structure, sequence and volcanogenic origin of Qingshankou Formation in the Cretaceous Songliao Basin
Acta Petrologica Sinica,
26
(1)
121-129
2010
ISSN: 10000569
Publisher: Science Press
Abstract: ▾ Drilling core from Chinese Continental Scientific Drilling-SK-I(s) presents four sets of deep lake seismite from the lower part of the second member to the bottom of the third member of Qingshankou Formation. Typical structures of the seismites include step micro-fault, seismic fissure bed, autoclastic brecciated structure, load structure, ball-and-pillow structure (pseudonodule), vibration-induced liquefaction structure, enterolithic structure, liquefaction sand dyke and pseudo-mud crack. All of these synsedimentary-penecontemporaneous soft-sediment deformation and absence of seismo-turbidite indicate that the seismites in Qingshankou Formation are previous soft sediment reconstruction related to earthquake. Seismites of Qingshankou Formation exhibit typical developmental pattern and sedimentary sequence of seismite. This seismic sequence consists of the lower unit of liquefaction deformation corresponding to strong earthquake and the upper unit of plastic deformation corresponding to earthquake attenuation. Mudstone with few altered glass shards and volcanic ash interlayers simultaneously developed in Qingshankou Formation from SK-I(s). Mugearite and volcanic breccia developed in well Jin6 and Jin65 and basalt developed in well Qian124 and Qian 109 during corresponding geological time of volcanic ash in SK-I(s). These four wells containing volcanic rock in Qingshankou Formation distribute along the Sunwu-Shuangliao transcrustal fault, which indicates that tectonic-volcanic activities occurred during Qingshankou period in Songliao Basin and seismites recorded earthquake activities induced by tectonic-volcanic event in deep water. Existence of tectonic-volcanic event in Qingshankou Formation suggests that fault activities and volcano eruptions should be normal phenomena during the sag stage in Songliao Basin.
982.
Collisional Orogeny in the Scandinavian Caledonides (COSC)
GFF,
132
(1)
29 -- 44
2010
ISSN: 1103-5897Abstract: ▾ The COSC project is focused on the mid Paleozoic Caledonide Orogen in Scandinavia in order to better understand orogenic processes, both in the past and in today's active mountain belts. It relates to two of ICDP's main themes – the fundamental physics of plate tectonics and heat, mass and fluid transfer through Earth's crust, and on improving interpretation of geophysical data used to determine the structure and properties of the Earth's crust. Lateral transport of Caledonian allochthons over distances of several hundreds of kilometers in the Scandes, by a combination of thrusting and ductile extrusion, is comparable to that recognized in the Himalayas. The Caledonides in Scandinavia provide special opportunities for understanding Himalayan-type orogeny and the Himalayan Orogen itself, thanks to the deep level of erosion and the paucity of superimposed post-Paleozoic deformation. The surface geology in combination with the seismic, magnetotelluric, magnetic and gravity data provide control of the geometry of the Caledonian structure, both of the allochthon and the underlying parautochthon-autochthon, and define the locations for drilling. The latter will investigate both the high-grade, ductile Caledonian nappes and the underlying allochthons and basement, with two c. 2.5 km deep boreholes, located near Åre and Järpen in western Jämtland. The two boreholes will also provide unique information about other important aspects of the Scandinavian bedrock, including the heat flow and potential for geothermal energy, mineralization in the Seve nappes and alum shales, the uplift history of the Scandes, the Holocene paleoclimatological changes and the deep biosphere.
981.
Climate in continental interior Asia during the longest interglacial of the past 500 000 years: The new MIS 11 records from Lake Baikal, SE Siberia
Climate of the Past,
6
(1)
31 – 48
2010
ISSN: 18149324
Publisher: Copernicus GmbH
Keywords:▾
Lake Baikal; Russian Federation; Siberia; Abies; Abies sibirica; Bacillariophyta; Coniferophyta; biostratigraphy; boreal forest; coniferous tree; correlation; diatom; dominance; interglacial; paleoclimate; palynology; proxy climate record; regional climate; timescale; vegetation history
Abstract: ▾ A synthesis of paleoclimate responses from Lake Baikal during the MIS 11 interglacial is presented based on proxy records from two drill sites 245 km apart. BDP-99 is located in vicinity of the delta of the major Baikal tributary, whereas the BDP-96 site represents hemipelagic setting distant from riverine influence. The comparison of thicknesses of interglacial intervals in these contrasting depositional settings confirms the extended ca. 33-kyr duration of the MIS 11 interglacial. The new BDP-99 diatom biostratigraphic record matches that of the BDP-96-2 holostratotype and thus allows establishing establishes robust correlation between the records on the same orbitally-tuned timescale. The first detailed MIS 11 palynological record from the BDP-99 drill core indicates the dominance of boreal conifer (taiga) forest vegetation in the Baikal region throughout the MIS 11 interglacial, since at least 424 ka till ca. 396 ka. The interval ca. 420-405 ka stands out as a "conifer optimum" with abundant Abies sibirica, indicative of climate significantly warmer and less continental than today. The closest Baikal analog to this type of vegetation in the history of the current Holocene interglacial is at ca. 9-7 ka. The warm conifer phase lasted for ca. 15 kyr during MIS 11 interrupted by two millennial-scale cooling episodes at ca. 411-410 and 405-404 ka. Reconstructed annual precipitation of 450- 550 mm/yr during the MIS 11 interglacial is by ca. 100mm higher than during the Holocene; regional climate was less continental with warmer mean temperatures both in summer and in winter. © Author(s) 2010.
980.
Carbonate sedimentation and effects of eutrophication observed at the Kališta subaquatic springs in Lake Ohrid (Macedonia)
Biogeosciences,
7
(11)
3755 – 3767
2010
ISSN: 17264189Keywords:▾
Lake Ohrid; Bacillariophyta; carbonate; chronology; diatom; eutrophication; lacustrine deposit; littoral environment; precipitation (chemistry); radiocarbon dating; sediment core; sediment trap; sedimentation; silt; sonar; stratigraphy; water column
Abstract: ▾ To date, little is known about the role of spring waters with respect to authigenic carbonate precipitation in a shallow lacustrine setting. Lake Ohrid, located in Southeastern Europe, is a large lake fed to over 50% by karstic springs of which half enter subaquatically and influence significantly its ecology and species distribution. In order to evaluate how sedimentological processes are influenced by such shallow-water springs, the Kališta subaquatic spring area in the north west of Lake Ohrid was investigated by a sidescan sonar survey and with sediment traps and three transects of gravity short cores. Results indicate that sedimentation in the spring area is dominated by authigenic carbonate precipitation. High sedimentation rates and evidences for bio-induced precipitation processes were observed in the water column and in the sediments. Two distinct stratigraphic units characterize the shallow subsurface, both composed of carbonate silts with high carbonate contents of up to 96%, but differing in color, carbonate content and diatom content. A chronological correlation of the cores by radiocarbon dates and 137Cs activities places the transition between the two stratigraphic units after ∼1955 AD. At that time, coastal sedimentation changed drastically to significantly darker sediments with higher contents of organic matter and more abundant diatoms. This change coincides with the recent human impact of littoral eutrophication. © 2010 Author(s).
979.
Calibration of the Late Triassic time scale: U-Pb zircon ages from the Chinle Formation
Geochimica et Cosmochimica Acta,
74
(12)
A738--A738
2010
978.
Astrochronology of the late Jurassic Kimmeridge Clay (Dorset, England) and implications for Earth system processes
Earth and Planetary Science Letters,
289
(1-2)
242 – 255
2010
ISSN: 0012821XKeywords:▾
Dorset [England]; England; United Kingdom; Ammonoidea; Astrophysics; Boreholes; Clay minerals; Offshore oil wells; Organic carbon; Tuning; Absolute calibration; Accumulation history; Borehole records; Borehole wall; Cyclicity; Cyclostratigraphy; Data sets; Dolostones; Drilling projects; Earth systems; Eccentricity cycle; Elegans; England; Geological process; High resolution; Jurassic; Kimmeridge clay formation; M sequence; Microscanner; Orbital eccentricity; Organic-rich source rock; Power-spectra; Relative sea level; Rock types; Seafloor spreading; Sequence stratigraphy; Time-scales; Total organic carbon; accumulation; astrophysics; coccolith; cyclostratigraphy; data set; dolostone; drilling; eccentricity; geochronology; Jurassic; Kimmeridgian; lamination; limestone; marl; Oxfordian; parameterization; sea level change; seafloor spreading; sequence stratigraphy; shale; source rock; timescale; Tithonian; total organic carbon; wavelength; Stratigraphy
Abstract: ▾ The Late Jurassic Kimmeridge Clay Formation (KCF) is an economically important, organic-rich source rock of Kimmeridgian-Early Tithonian age. The main rock types of the KCF in Dorset, UK, include grey to black laminated shale, marl, coccolithic limestone, and dolostone, which occur with an obvious cyclicity at astronomical timescales. In this study, we examine two high-resolution borehole records (Swanworth Quarry 1 and Metherhills 1) obtained as part of a Rapid Global Geological Events (RGGE) sediment drilling project. Datasets examined were total organic carbon (TOC), and borehole wall microconductivity by Formation Microscanner (FMS). Our intent is to assess the rhythmicity of the KCF with respect to the astronomical timescale, and to discuss the results with respect to other key Late Jurassic geological processes. Power spectra of the untuned data reveal a hierarchy of cycles throughout the KCF with ∼ 167 m, ∼ 40 m, 9.1 m, 3.8 m and 1.6 m wavelengths. Tuning the ∼ 40 m cycles to the 405-kyr eccentricity cycle shows the presence of all the astronomical parameters: eccentricity, obliquity, and precession index. In particular, ∼ 100-kyr and 405-kyr eccentricity cycles are strongly expressed in both records. The 405-kyr eccentricity cycle corresponds to relative sea-level changes inferred from sequence stratigraphy. Intervals with elevated TOC are associated with strong obliquity forcing. The 405-kyr-tuned duration of the lower KCF (Kimmeridgian Stage) is 3.47 Myr, and the upper KCF (early part of the Tithonian Stage, elegans to fittoni ammonite zones) is 3.32 Myr. Two other chronologies test the consistency of this age model by tuning ∼ 8-10 m cycles to 100-kyr (short eccentricity), and ∼ 3-5 m cycles to 36-kyr (Jurassic obliquity). The 'obliquity-tuned' chronology resolves an accumulation history for the KCF with a variation that strongly resembles that of Earth's orbital eccentricity predicted for 147.2 Ma to 153.8 Ma. There is evidence for significant non-deposition (up to 1 million years) in the lowermost KCF (baylei-mutabilis zones), which would indicate a Kimmeridgian/Oxfordian boundary age of 154.8 Ma. This absolute calibration allows assignment of precise numerical ages to zonal boundaries, sequence surfaces, and polarity chrons of the lower M-sequence. © 2009 Elsevier B.V. All rights reserved.
977.
Aeromagnetic anomaly modeling of central zone structure and magnetic sources in the Chicxulub crater
Physics of the Earth and Planetary Interiors,
179
(3-4)
127-138
2010
Abstract: ▾ The analytic signal method and forward modeling in three dimensions are applied to magnetic field data over the Chicxulub crater in order to determine and document the main magnetic anomaly sources and crater structure in the central zone. Aeromagnetic data over the structure reveal three strong, well-defined concentric patterns, with a central 40-km diameter zone of high amplitude anomalies. Magnetic anomalies are interpreted to be associated with the melt sheet, upper breccias and central uplift, which present three to four orders of magnitude contrasts with the surrounding carbonate units. The limited number of magnetic property measurements, apparent wide range in the remanent intensity and susceptibility in the upper breccias and possible yet unconstrained zones of hydrothermal systems have restricted our ability to determine the characteristics and distribution of major structural elements of the Chicxulub crater. The amplitude of the analytic signal produces maxima over magnetization contrasts, independent of the direction of magnetization. Interpretation of maxima location and depth distribution is used, in a second stage, as a priori information in the construction of an input prism assemblage magnetic configuration and its properties for three-dimensional forward modeling. Results indicate that magnetic sources extend to a radial distance of ∼45. km from the center of the structure with average depths ranging between 2 and 4. km. The magnetic anomaly sources in the central structural uplift zone are located in the range from 3.5 to 8. km depth, with dominant contributions from an apparent large body forming the basement uplift. © 2010 Elsevier B.V.
976.
Dynamics and internal structure of the Hawaiian plume
Earth and Planetary Science Letters,
295
(1-2)
231 – 240
2010
ISSN: 0012821XKeywords:▾
Hawaii [United States]; United States; Computer simulation; Filaments (lamp); Conduit structure; Dynamical model; Fluid dynamic simulation; Geochemical heterogeneity; Internal structure; Isotopic record; Kilauea; Long lasting; Mantle heterogeneity; Oceanic plate; Phase samples; Plume dynamics; Plume structure; Scientific drilling; Source region; Thermal boundary layer; Three-dimensional numerical simulations; Time-scales; Topdown; fluid dynamics; igneous geochemistry; isotopic composition; lava; mantle plume; simulation; volcano; Volcanoes
Abstract: ▾ A thorough understanding of the internal structure of the Hawaiian plume conduit requires to link geochemical observations of surface lavas to fluid dynamic simulations able to quantify the flow trajectories of upwelling geochemical heterogeneities and their sampling by volcanoes. With the present work we fill a gap between the numerous geochemical studies of Hawaiian lavas and the paucity of dynamical models that relate the observed geochemical record to the internal plume structure. Our three-dimensional numerical simulation of a vigorous plume sheared by a fast moving oceanic plate shows that the dominant deformation in the conduit is vertical stretching, while horizontal spreading and vertical shortening prevail in the sublithospheric part of the plume (hereafter referred to as plume head). Flow trajectories indicate that a young volcano like Loihi samples the 'upstream' side of the plume, not its center, whereas volcanoes in the post-shield phase sample deep melts from the 'downstream' side of the plume. To constrain the internal conduit structure we focus on two geochemical observations: old (>350 kyr) Mauna Kea lavas from the Hawaii Scientific Drilling Project are isotopically distinct from recent Mauna Kea lavas, but they are isotopically identical to present-day Kilauea lavas. By modelling a plume conduit with several long-lasting filaments of 10. km radius, we find that the isotopic record of a volcano (e.g., Mauna Kea) is expected to change over time-scales of ~400. kyr. Furthermore, by requiring that two age progressive volcanoes (e.g., Mauna Kea and Kilauea) sample the same filament, we constrain the minimum filament length to be ~600. km. In this paper we adopt a 'top-down' approach: from geochemical observations of surface lavas, to dynamical models of the conduit structure, and further down to the 'geochemical architecture' of the thermal boundary layer feeding the plume. A conduit structure with filaments maps back into heterogeneous volumes with azimuthal and radial extents of several hundred kilometers in the source region of plumes. © 2010 Elsevier B.V.
975.
Advances of international continental scientific drilling program
Acta Geologica Sinica (English Edition),
84
(6)
873-886
2010
ISSN: 10009515Abstract: ▾ It has long been a dream for mankind to enter the deep Earth to sample and investigate the structures and inner geological progresses. Until now, scientific drilling has been the unique method in our understanding of the processes and structures of the Earth. This paper try to give a brief introduction of the history, the development, the mission, the structure and management, the membership, the project development scheme of International Continental Drilling Program (ICDP). Great advances have been brought about in many fields of earth sciences by continental scientific drilling in recent years. Based on the recent publications and website materials of ICDP, this paper summarize the main developments in Climate Dynamics and Global Environments, in the Study of Impact Craters, in the GeoBiospherc, in Active Volcanic Systems, in Active Faults, in Hotspot Volcanoes, in Convergent Plate Boundaries and Collision Zones, and in Natural Resources. Special introduction on the scientific results of ICDP drilling at Mt. Unzen, Japan and the Hawaii Scientific Drilling Project (HSDP) is introduced in this paper. Fascinating discoveries such as the gouge layer of San Andreas Fault and the finding of talc in cuttings of SAFOD project are also introduced in this paper. As one of the three founding members of ICDP, China has also gained a lot of developments in continental scientific drilling; typical examples are the achievements of Chinese Continental Scientific Drilling (CCSD) and the progress of Lake Qinghai Scientific Drilling Project. The preliminary progresses . of the third approved ICDP project of China -the Chinese Cretaceous Continental Scientific Drilling Project and the development of ICDP-China are also summarized in this paper.
974.
Advances of international continental scientific drilling program
Acta Geologica Sinica (English Edition),
84
(6)
873-886
2010
ISSN: 10009515Abstract: ▾ It has long been a dream for mankind to enter the deep Earth to sample and investigate the structures and inner geological progresses. Until now, scientific drilling has been the unique method in our understanding of the processes and structures of the Earth. This paper try to give a brief introduction of the history, the development, the mission, the structure and management, the membership, the project development scheme of International Continental Drilling Program (ICDP). Great advances have been brought about in many fields of earth sciences by continental scientific drilling in recent years. Based on the recent publications and website materials of ICDP, this paper summarize the main developments in Climate Dynamics and Global Environments, in the Study of Impact Craters, in the GeoBiospherc, in Active Volcanic Systems, in Active Faults, in Hotspot Volcanoes, in Convergent Plate Boundaries and Collision Zones, and in Natural Resources. Special introduction on the scientific results of ICDP drilling at Mt. Unzen, Japan and the Hawaii Scientific Drilling Project (HSDP) is introduced in this paper. Fascinating discoveries such as the gouge layer of San Andreas Fault and the finding of talc in cuttings of SAFOD project are also introduced in this paper. As one of the three founding members of ICDP, China has also gained a lot of developments in continental scientific drilling; typical examples are the achievements of Chinese Continental Scientific Drilling (CCSD) and the progress of Lake Qinghai Scientific Drilling Project. The preliminary progresses . of the third approved ICDP project of China -the Chinese Cretaceous Continental Scientific Drilling Project and the development of ICDP-China are also summarized in this paper.
973.
Advances of international continental scientific drilling program
Acta Geologica Sinica (English Edition),
84
(6)
873-886
2010
ISSN: 10009515Abstract: ▾ It has long been a dream for mankind to enter the deep Earth to sample and investigate the structures and inner geological progresses. Until now, scientific drilling has been the unique method in our understanding of the processes and structures of the Earth. This paper try to give a brief introduction of the history, the development, the mission, the structure and management, the membership, the project development scheme of International Continental Drilling Program (ICDP). Great advances have been brought about in many fields of earth sciences by continental scientific drilling in recent years. Based on the recent publications and website materials of ICDP, this paper summarize the main developments in Climate Dynamics and Global Environments, in the Study of Impact Craters, in the GeoBiospherc, in Active Volcanic Systems, in Active Faults, in Hotspot Volcanoes, in Convergent Plate Boundaries and Collision Zones, and in Natural Resources. Special introduction on the scientific results of ICDP drilling at Mt. Unzen, Japan and the Hawaii Scientific Drilling Project (HSDP) is introduced in this paper. Fascinating discoveries such as the gouge layer of San Andreas Fault and the finding of talc in cuttings of SAFOD project are also introduced in this paper. As one of the three founding members of ICDP, China has also gained a lot of developments in continental scientific drilling; typical examples are the achievements of Chinese Continental Scientific Drilling (CCSD) and the progress of Lake Qinghai Scientific Drilling Project. The preliminary progresses . of the third approved ICDP project of China -the Chinese Cretaceous Continental Scientific Drilling Project and the development of ICDP-China are also summarized in this paper.
972.
Advances of international continental scientific drilling program
Acta Geologica Sinica (English Edition),
84
(6)
873 – 886
2010
ISSN: 10009515Abstract: ▾ It has long been a dream for mankind to enter the deep Earth to sample and investigate the structures and inner geological progresses. Until now, scientific drilling has been the unique method in our understanding of the processes and structures of the Earth. This paper try to give a brief introduction of the history, the development, the mission, the structure and management, the membership, the project development scheme of International Continental Drilling Program (ICDP). Great advances have been brought about in many fields of earth sciences by continental scientific drilling in recent years. Based on the recent publications and website materials of ICDP, this paper summarize the main developments in Climate Dynamics and Global Environments, in the Study of Impact Craters, in the GeoBiospherc, in Active Volcanic Systems, in Active Faults, in Hotspot Volcanoes, in Convergent Plate Boundaries and Collision Zones, and in Natural Resources. Special introduction on the scientific results of ICDP drilling at Mt. Unzen, Japan and the Hawaii Scientific Drilling Project (HSDP) is introduced in this paper. Fascinating discoveries such as the gouge layer of San Andreas Fault and the finding of talc in cuttings of SAFOD project are also introduced in this paper. As one of the three founding members of ICDP, China has also gained a lot of developments in continental scientific drilling; typical examples are the achievements of Chinese Continental Scientific Drilling (CCSD) and the progress of Lake Qinghai Scientific Drilling Project. The preliminary progresses . of the third approved ICDP project of China -the Chinese Cretaceous Continental Scientific Drilling Project and the development of ICDP-China are also summarized in this paper.
971.
A theoretical model of the explosive fragmentation of vesicular magma
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences,
466
(2115)
731-752
2010
ISSN: 13645021
Publisher: Royal Society
Keywords:▾
Brittle fracture; Explosions; Nitration; Submarine geophysics; Yield stress, Brittle fragmentation; Catastrophic explosion; Confining pressures; Excess pore pressure; Explosive fragmentation; Explosive volcanism; Horizontal fractures; Internal fracture; Magma fragmentation; Magmatic explosion; Porous flow; Primary sequences; Rock permeability; Silicic magmas; Theoretical models; Topdown; Vertical columns, Explosives
Abstract: ▾ Recent experimental work has shown that, when a vertical column of rock under large pressure is suddenly depressurized, the column can 'explode' in a structured and repeatable way. The observations show that a sequence of horizontal fractures forms from the top down, and the resulting blocks are lifted off and ejected. The blocks can suffer secondary internal fractures. This experiment provides a framework for understanding the way in which catastrophic explosion can occur, and is motivated by the corresponding phenomenon of magmatic explosion during Vulcanian eruptions. We build a theoretical model to describe these results, and show that it is capable of describing both the primary sequence of fracturing and the secondary intrablock fracturing. The model allows us to suggest a practical criterion for when such explosions occur: firstly, the initial confining pressure must exceed the yield stress of the rock, and, secondly, the diffusion of the gas by porous flow must be sufficiently slow that a large excess pore pressure is built up. This will be the case if the rock permeability is small enough. © 2010 The Royal Society.
970.
A theoretical exercise in the modeling of ground-level ozone resulting from the K-T asteroid impact: Its possible link with the extinction selectivity of terrestrial vertebrates
Palaeogeography, Palaeoclimatology, Palaeoecology,
288
(1-4)
14-23
2010
Abstract: ▾ The extinction pattern of the Maastrichtian indicates that long-term and short-term events contributed to the Cretaceous-Tertiary (K-T) mass extinction at 65 Ma. However, it is not clear how the impact events are linked with the extinction selectivity; e.g. non-avian dinosaurs became extinct, whereas birds survived. The post-impact air quality is discussed, and attention is focused on the then land vertebrates. Although ground-level (tropospheric) O3 is a powerful irritant on the order of 0.1 ppm toxicity, the presence of ground-level O3 has hardly been considered since the K-T impact theory was reported about 30 years ago. Under the post-impact conditions reconstructed by simulating the carbon cycle (including isotope balance) and impact chemistry, a trajectory model suggests that the then photochemical reactions formed ground-level O3 whose concentration was apparently low at ∼ 1.0 ppm, but it is much greater than the current level of ∼ 0.04 ppm: that is, an O3 concentration above the health-threatening level persisted on the ground after the K-T impact. All land vertebrates must have suffered from respiratory O3 irritation at the time. However, analysis suggests that variables of O3 characteristics - hourly variation, short half-life in water and decomposition due to catalytic effects in soil - were randomly combined with variables of lifestyle features such as habitat, torpor, etc. to form new variables (i.e. survival rates): a high survival probability for amphibians; middle/high probabilities for semi-aquatic reptiles, mammals and birds; low/middle probabilities for marsupials and terrestrial reptiles; and a zero probability for non-avian dinosaurs. © 2010 Elsevier B.V. All rights reserved.