All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
894.
On the origin of mixed-layered clay minerals from the San Andreas Fault at 2.5-3 km vertical depth (SAFOD drillhole at Parkfield, California)
Contributions to Mineralogy and Petrology,
157
(2)
173-187
2009
ISSN: 00107999Keywords:▾
chlorite; crystallization; deformation mechanism; diagenesis; illite; mudstone; San Andreas Fault; smectite; thermal structure, California; North America; Parkfield; United States
Abstract: ▾ A detailed mineralogical study is presented of the matrix of mudrocks sampled from spot coring at three key locations along the San Andreas Fault Observatory at depth (SAFOD) drill hole. The characteristics of authigenic illite-smectite (I-S) and chlorite-smectite (C-S) mixed-layer mineral clays indicate a deep diagenetic origin. A randomly ordered I-S mineral with ca. 20-25% smectite layers is one of the dominant authigenic clay species across the San Andreas Fault zone (sampled at 3,066 and 3,436 m measured depths/MD), whereas an authigenic illite with ca. 2-5% smectite layers is the dominant phase beneath the fault (sampled at 3,992 m MD). The most smectite-rich mixed-layered assemblage with the highest water content occurs in the actively deforming creep zone at ca. 3,300-3,353 m (true vertical depth of ca. 2.7 km), with I-S (70:30) and C-S (50:50). The matrix of all mudrock samples show extensive quartz and feldspar (both plagioclase and K-feldspar) dissolution associated with the crystallization of pore-filling clay minerals. However, the effect of rock deformation in the matrix appears only minor, with weak flattening fabrics defined largely by kinked and fractured mica grains. Adopting available kinetic models for the crystallization of I-S in burial sedimentary environments and the current borehole depths and thermal structure, the conditions and timing of I-S growth can be evaluated. Assuming a typical K+ concentration of 100-200 ppm for sedimentary brines, a present-day geothermal gradient of 35°C/km and a borehole temperature of ca. 112°C for the sampled depths, most of the I-S minerals can be predicted to have formed over the last 4-11 Ma and are probably still in equilibrium with circulating fluids. The exception to this simple burial pattern is the occurrence of the mixed layered phases with higher smectite content than predicted by the burial model. These minerals, which characterize the actively creeping section of the fault and local thin film clay coating on polished brittle slip surfaces, can be explained by the influence of either cooler fluids circulating along this segment of the fault or the flow of K+-depleted brines. © Springer-Verlag 2008.
893.
Organic geochemical characteristics of anoxic levels in the Cretaceous Qingshankou Formation of Songliao Basin.
Earth Science Frontiers,
16
(6)
96
2009
892.
Postimpact deposition in the Chesapeake Bay impact structure: Variations in eustasy, compaction, sediment supply, and passive-aggressive tectonism
Special Paper of the Geological Society of America,
458811-837
2009
ISSN: 00721077
Publisher: Geological Society of America
Keywords:▾
Compaction; Concurrency control; Infill drilling; Offshore oil well production; Sediments; Stratigraphy, Basement structures; Chesapeake bay impact structures; Depositional sequences; Regional tectonics; Regional variation; Sediment starvation; Sequence boundary; Sequence-stratigraphic interpretation, Deposition, deposition; depositional sequence; Eocene; geochronology; glacioeustacy; impact structure; Miocene; Oligocene; Pliocene; sedimentation rate; sequence boundary; sequence stratigraphy; subsidence, Chesapeake Bay; Delmarva Peninsula; New Jersey; United States; Virginia
Abstract: ▾ The Eyreville and Exmore, Virginia, core holes were drilled in the inner basin and annular trough, respectively, of the Chesapeake Bay impact structure, and they allow us to evaluate sequence deposition in an impact crater. We provide new high-resolution geochronologic (<1 Ma) and sequence-stratigraphic interpretations of the Exmore core, identify 12 definite (and four possible) postimpact depositional sequences, and present comparisons with similar results from Eyreville and other mid- Atlantic core holes. The concurrence of increases in δ 18 O with Chesapeake Bay impact structure sequence boundaries indicates a primary glacioeustatic control on deposition. However, regional comparisons show the differential preservation of sequences across the mid-Atlantic margin. We explain this distribution by the compaction of impactites, regional sediment-supply changes, and the differential movement of basement structures. Upper Eocene strata are thin or missing updip and around the crater, but they thicken into the inner basin (and offshore to the southeast) due to rapid crater infilling and concurrent impactite compaction. Oligocene sequences are generally thin and highly dissected throughout the mid-Atlantic region due to sediment starvation and tectonism, except in southeastern New Jersey. Regional tectonic uplift of the Norfolk Arch coupled with a southward decrease in sediment supply resulted in: (1) largely absent Lower Miocene sections around the Chesapeake Bay impact structure compared to thick sections in New Jersey and Delaware; (2) thick Middle Miocene sequences across the Delmarva Peninsula that thin south of the Chesapeake Bay impact structure; and (3) upper Middle Miocene sections that pinch out just north of the Chesapeake Bay impact structure. Conversely, the Upper Miocene-Pliocene section is thick across Virginia, but it is poorly represented in New Jersey because of regional variations in relative subsidence. © 2009 The Geological Society of America.
891.
Understanding paleoclimate and human evolution through the hominin sites and paleolakes drilling project
Scientific Drilling
(8)
60 – 65
2009
ISSN: 18168957
Publisher: Integrated Ocean Drilling Program
890.
Pre-impact tectonothermal evolution of the crystalline basement-derived rocks in the ICDP-USGS Eyreville B core, Chesapeake Bay impact structure
Special Paper of the Geological Society of America,
458235-254
2009
ISSN: 00721077
Publisher: Geological Society of America
Keywords:▾
Calcite; Core drilling; Crystalline materials; Fault slips; Feldspar; Garnets; Granite; Infill drilling; Mica; Shear deformation; Silicate minerals; Strike-slip faults; Structural geology; Temperature, Amphibolite facies; Brittle deformation; Cataclastic deformation; Chesapeake bay impact structures; Crystalline basement; Metamorphic conditions; Metavolcanic rocks; Strike slip faulting, Crystalline rocks, amphibolite; brittle deformation; crystalline rock; faulting; impact structure; metagreywacke; metamorphism; metavolcanic rock; schist; tectonic evolution; thermal evolution, Chesapeake Bay; United States
Abstract: ▾ Pre-impact crystalline rocks of the lowermost 215 m of the Eyreville B drill core from the Chesapeake Bay impact structure consist of a sequence of pelitic mica schists with subsidiary metagraywackes or felsic metavolcanic rocks, amphibolite, and calc-silicate rock that is intruded by muscovite (±biotite, garnet) granite and granite pegmatite. The schists are commonly graphitic and pyritic and locally contain plagioclase porphyroblasts, fi brolitic sillimanite, and garnet that indicate middle- to upper-amphibolite-facies peak metamorphic conditions estimated at ̃0.4-0.5 GPa and 600-670 °C. The schists display an intense, shallowly dipping, S1 composite shear foliation with local micrometer- to decimeter-scale recumbent folds and S-C' shear band structures that formed at high temperatures. Zones of chaotically oriented foliation, resembling breccias but showing no signs of retrogression, are developed locally and are interpreted as shear-disrupted fold hinges. Mineral textural relations in the mica schists indicate that the metamorphic peak was attained during D1. Fabric analysis indicates, however, that subhorizontal shear deformation continued during retrograde cooling, forming mylonite zones in which high-temperature shear fabrics (S-C and S-C') are overprinted by progressively lower- temperature fabrics. Cataclasites and carbonate-cemented breccias in more competent lithologies such as the calc-silicate unit and in the felsic gneiss found as boulders in the overlying impactite succession may refl ect a fi nal pulse of low-temperature cataclastic deformation during D1. These breccias and the shear and mylonitic foliations are cut by smaller, steeply inclined anastomosing fractures with chlorite and calcite infill (interpreted as D2). This D2 event was accompanied by extensive chlorite-sericitecalcite ± epidote retrogression and appears to predate the impact event. Granite and granite pegmatite veins display local discordance to the S1 foliation, but elsewhere they are affected by high-temperature mylonitic shear deformation, suggesting a late-D1 intrusive timing close to the metamorphic peak. The D1 event is tentatively interpreted as a thrusting event associated with westward-verging collision between Gondwana and Laurentia before or during the Permian-Carboniferous Alleghanian orogeny. It is unclear whether subsequent brittle deformation, described here as D2, could be part of regional dextral Alleghanian strike-slip faulting or younger Mesozoic normal faulting. © 2009 The Geological Society of America.
889.
Unique coesite-bearing zircon from allanite-bearing gneisses: U-Pb, REE and Lu-Hf properties and implications for the evolution of the Sulu UHP terrane, China
European Journal of Mineralogy,
21
(6)
1225 – 1250
2009
ISSN: 09351221
Publisher: Gebruder Borntraeger Verlagsbuchhandlung
Keywords:▾
China; Dabie-Sulu Belt; Sulu Belt; Binary alloys; Exploratory geochemistry; Feldspar; Geochronology; Isotopes; Lead alloys; Levees; Metamorphic rocks; Rare earth elements; Rare earths; Silica; Trace elements; Zircon; Allanite; Coesite; Gneiss; Hf isotope; Sulu UHP terrane; U-Pb dating; allanite; cathodoluminescence; coesite; diamond; gneiss; hafnium; isotopic fractionation; lutetium; rare earth element; retrograde metamorphism; trace element; uranium-lead dating; zircon; Lutetium alloys
Abstract: ▾ Zircon from allanite-bearing para- and ortho-gneisses provides a unique insight into the geologic evolution of the Sulu ultrahigh-pressure (UHP) terrane in eastern China. Laser Raman, cathodoluminescence (CL) imaging combined with trace-element, U-Pb, and Lu-Hf isotope data indicate that zircon grains consist of three distinct zones. Inherited magmatic core records a Neoproterozoic protolith age, the coesite-bearing mantle reveals a UHP metamorphic age of 230 ± 7 Ma, and the low-P mineralbearing rim retains an age of 210 ± 3 Ma for the amphibolite-facies retrogression. Positive εHf(t) values for the inherited cores reflect involvement of juvenile materials in the protolith. Low 176Lu/177Hf ratios of coesite-bearing mantles indicate their formation during / after gamet crystallization. Their 176Hf/177Hf ratios are homogenous and more radiogenic than those of the inherited cores, implying fractionation of the Lu-Hf system during isotope equilibration within the metamorphic mineral assemblage. Moreover, coesitebearing mantles show geochemical characteristics that are distinctly different from those of previous studies: (1) The chondritenormalized pattern shows a steep slope from HREE (heavy rare earth elements) to LREE (light rare earth elements) with a moderately negative Eu anomaly (mean Eu/Eu* = 0.53). Such a pattern requires that phases enriched in LREE (e.g., allanite) and europium (e.g., K-feldspar) were stable during UHP conditions. (2) The positive Ce anomaly is very pronounced (Ce/Ce* of 612-657), e.g., about seven to eight times higher than that of the inherited core; (3) The uranium content is very low (6-25 ppm) and the Th/U ratio elevated (0.52-2.83). These data for the coesite-bearing mantle are distinctly different from those of previous studies. We interpret the data to suggest high O fugacity during the UHP and retrograde metamorphic evolution, which also played a critical role in restraining diamond growth in Sulu-Dabie UHP rocks. © 2009 E. Schweizerbart'sehe Verlagsbuchhandlung.
888.
The record of ground zero in the Chesapeake Bay impact crater-Suevites and related rocks
Special Paper of the Geological Society of America,
458349-376
2009
ISSN: 00721077
Publisher: Geological Society of America
Keywords:▾
Boreholes; Debris; Excavation; Infill drilling; Structural geology, Basement rocks; Continental scientific drillings; Continuous deposition; High-pressure polymorph; Oblique impact; Thermal-annealing; Transient cavities; U.s. geological surveys, Rocks, crater; drilling; impact structure; impactite; marine sediment; petrogenesis; suevite, Chesapeake Bay; United States
Abstract: ▾ The International Continental Scientific Drilling Program (ICDP)-U.S. Geological Survey (USGS) Eyreville boreholes through the annular moat of the Chesapeake Bay crater recovered polymict impact breccias and associated rocks from the depth range of 1397-1551 m. These rocks record cratering processes before burial beneath resurge deposits. Quantitative analyses of clast sizes, matrix contents, and distribution of impact melt reveal a shock metamorphic gradient in these impactites. The reason for the low estimated quantity of impact melt in the crater (̃10 km3) remains elusive. Possible causes may relate to increased excavation efficiency due to a high ratio of water column and sedimentary target to depth of excavation, an oblique impact, or a buried melt sheet at depth. A plausible petrogenetic scenario consists of a lower blockrich section that slumped from an outer region of the transient cavity into the annular moat ̃1.5 min after impact. This blocky debris was mixed with the remains of the excavation fl ow, which contained a pod of melt entrained in ground-surge debris on top. Subsequently, melt-rich suevites were emplaced that record interaction of the expanding ejecta plume with fallback material related to the evolving central uplift. A clast-rich impact melt rock that likely shed off the central uplift covers these suevites. Incipient collapse of the ejecta plume is recorded in the uppermost subunit, but the arrival of resurge fl ow terminated its continuous deposition ̃6-8 min after impact. Limited thermal annealing allowed preservation of glassy melt and high-pressure polymorphs. Mild hydrothermal overprint in the central crater was likely driven by the structural uplift of ̃100 °C warmer basement rocks. © 2009 The Geological Society of America.
887.
The record of ground zero in the Chesapeake Bay impact crater-Suevites and related rocks
Special Paper of the Geological Society of America,
458349-376
2009
Abstract: ▾ The International Continental Scientific Drilling Program (ICDP)-U.S. Geological Survey (USGS) Eyreville boreholes through the annular moat of the Chesapeake Bay crater recovered polymict impact breccias and associated rocks from the depth range of 1397-1551 m. These rocks record cratering processes before burial beneath resurge deposits. Quantitative analyses of clast sizes, matrix contents, and distribution of impact melt reveal a shock metamorphic gradient in these impactites. The reason for the low estimated quantity of impact melt in the crater (̃10 km3) remains elusive. Possible causes may relate to increased excavation efficiency due to a high ratio of water column and sedimentary target to depth of excavation, an oblique impact, or a buried melt sheet at depth. A plausible petrogenetic scenario consists of a lower blockrich section that slumped from an outer region of the transient cavity into the annular moat ̃1.5 min after impact. This blocky debris was mixed with the remains of the excavation fl ow, which contained a pod of melt entrained in ground-surge debris on top. Subsequently, melt-rich suevites were emplaced that record interaction of the expanding ejecta plume with fallback material related to the evolving central uplift. A clast-rich impact melt rock that likely shed off the central uplift covers these suevites. Incipient collapse of the ejecta plume is recorded in the uppermost subunit, but the arrival of resurge fl ow terminated its continuous deposition ̃6-8 min after impact. Limited thermal annealing allowed preservation of glassy melt and high-pressure polymorphs. Mild hydrothermal overprint in the central crater was likely driven by the structural uplift of ̃100 °C warmer basement rocks. © 2009 The Geological Society of America.
886.
Three-dimensional passive seismic waveform imaging around the SAFOD site, California, using the generalized Radon transform
Geophysical Research Letters,
36
(23)
2009
ISSN: 00948276Keywords:▾
2D images; Active area; California; Earthquake data; Fault zone; Generalized radon transform; Image profile; Inverse scattering; P-waves; Prestack; San Andreas Fault; Seismic migration; Seismic reflections; Seismic waveforms; Source imaging; Temporary networks; Three-dimensional (3D), Earthquakes; Radon; Reflection; Seismic waves; Surveys, Three dimensional, data inversion; earthquake event; fault zone; imaging method; P-wave; prestack migration; Radon transform; seismic migration; seismic reflection; three-dimensional modeling; wave scattering; waveform analysis, California; North America; United States
Abstract: ▾ We apply a three-dimensional (3D) generalized Radon transform (GRT) to scattered P-waves from 575 local earthquakes recorded at 68 temporary network stations for passive-source imaging of (near-vertical) structures close to the San Andreas Fault Observatory at Depth (SAFOD) site. The GRT image profiles through or close by the SAFOD site reveal near-vertical reflectors close to the fault zone as well as in the granite to the southwest and the Franciscan mélange to the northeast of the main fault. Although slightly lower in resolution, these structures are generally similar to features in 2D images produced with steep-dip prestack seismic migration of data from active source seismic reflection and refraction surveys. Our GRT images, however, also reveal several vertical reflectors to the northeast of the SAF that do not appear in the migration images but which are consistent with local geology. These results suggest that in a seismically active area, inverse scattering of earthquake data (for instance with the GRT) can be a viable and, in 3D, economic alternative to an active source survey. Copyright 2009 by the American Geophysical Union.
885.
Tidal modulation of temperature oscillations monitored in borehole Yaxcopoil-1 (Yucatán, Mexico)
Earth and Planetary Science Letters,
282
(1-4)
131-139
2009
Abstract: ▾ For better understanding of temperature state in the subsurface, temperature-depth logs can be suitably completed by high-resolution long-run temperature-time monitoring at selected depths. The results of temperature monitoring at three depth levels in borehole Yaxcopoil-1, Chicxulub impact structure, Mexico (April/May 2006) proved that even when a borehole is in "fully" stabilized conditions, temperature may exhibit certain unrest resembling irregular oscillations in the order of hundredths or (in the extreme case) even first tenths of degree. Two novel methods for detection of the weak fingerprints of stable periodic components in long noisy records, namely the RQI (Recurrence Quantification Interval) analysis and the HiCum (Histograms Cumulation) were used to isolate the constituents with tidal periodicities from temperature oscillations measured in borehole Yaxcopoil-1. Both analyses revealed that temperature series contain perceptible tidal component. The field data were correlated with the simulated synthetic tides. The comparison of staked HiCum records for the theoretical gravity tide and monitored temperature shows significant positive linear correlation between both variables. There is a small lag between two signals corresponding to ~ 25 min phase difference. © 2009 Elsevier B.V. All rights reserved.
884.
Toward a geochemical mass balance of major elements in Lake Qinghai, NE Tibetan Plateau: A significant role of atmospheric deposition
Applied Geochemistry,
24
(10)
1901 – 1907
2009
ISSN: 08832927Keywords:▾
Asia; China; Eurasia; Far East; Qinghai; Qinghai Lake; Qinghai-Xizang Plateau; Atmospheric chemistry; Atmospherics; Budget control; Calcium; Catchments; Deposition; Meteorological problems; Patient monitoring; Runoff; Sedimentology; Annual budget; Atmospheric depositions; Desert area; Environmental change; Input-output; Lake sediments; Lake waters; Loess Plateau; Major elements; Mass accumulation rates; Mass balance; Realistic model; Riverine flux; Tibetan Plateau; Wet deposition; atmospheric deposition; environmental change; geochemistry; lacustrine deposit; mass balance; Lakes
Abstract: ▾ Sediments in Lake Qinghai archive important information about past environmental changes. In order to faithfully interpret the sediment records and constrain the elemental cycles, it is critical to trace various sources of sediments in the lake. The results show that the elemental input-output budgets are imbalanced for most major elements between riverine fluxes and mass accumulation rate (MAR) of Lake Qinghai sediments. A realistic model must include contributions of dry/wet atmospheric deposition that allow the major element mass balance for the lake to be defined. The budget estimation is based on mass balances of Si and Al, which are relatively immobile and carried to the lake via particulate forms. Estimated annual budget of dry atmospheric deposition is ∼1.3 ± 0.3 × 103 kt/a (accounting for ∼65% of the total inputs) to the lake sediments, assuming local loess within the catchment as a candidate for dry atmospheric deposition to the lake. The resultant flux of 300 ± 45 g/m2/a falls within the flux average of the desert area (400 g/m2/a) and the loess plateau (250 g/m2/a), consistent with the geographical setting of Lake Qinghai. The role of atmospheric deposition would be more significant if wet deposition via rainfall and snow were taken into account. This highlights the potential importance of dust as a significant source for sediment preservation flux for other catchments worldwide. The results also indicate that nearly all Ca input was preserved in the lake sediments under modern conditions, consistent with Ca2+ supersaturation of the lake water. © 2009 Elsevier Ltd. All rights reserved.
883.
Trends, rhythms and events in Plio-Pleistocene African climate
Quaternary Science Reviews,
28
(5-6)
399 – 411
2009
ISSN: 02773791Keywords:▾
Africa; Sub-Saharan Africa; West Africa; Mammalia; Climatology; Mammals; Salinity measurement; Submarine geology; climate variation; dust; marine sediment; Mediterranean Water; Pleistocene; statistical analysis; subtropical region; terrigenous deposit; trend analysis; Arabian seas; Climate variabilities; Dust fluxes; East africa; Eastern mediterraneans; Environmental significances; Marine sediments; West-Africa; Dust
Abstract: ▾ We analyzed published records of terrigenous dust flux from marine sediments off subtropical West Africa, the eastern Mediterranean Sea, and the Arabian Sea, and lake records from East Africa using statistical methods to detect trends, rhythms and events in Plio-Pleistocene African climate. The critical reassessment of the environmental significance of dust flux and lake records removes the apparent inconsistencies between marine vs. terrestrial records of African climate variability. Based on these results, major steps in mammalian and hominin evolution occurred during episodes of a wetter, but highly variable climate largely controlled by orbitally induced insolation changes in the low latitudes. © 2008 Elsevier Ltd. All rights reserved.
882.
Ultrahigh-pressure texture inheritance during retrogression: Evidence from magnetofabrics in eclogites and ultramafic rocks (Chinese Continental Scientific Drilling project)
Tectonophysics,
475
(2)
267 – 278
2009
ISSN: 00401951Keywords:▾
Asia; China; Eurasia; Far East; Sulu Belt; Deformation; Drilling; Fabrics; Garnets; Magnetite; Olivine; Oxide minerals; Rocks; Silicate minerals; Textures; CCSD; Exhumation; Magnetofabrics; Sulu; Ultrahigh-pressure; amphibole; Chinese Continental Scientific Drilling Project; eclogite; exhumation; magnetic fabric; magnetite; retrograde metamorphism; texture; ultrahigh pressure metamorphism; ultramafic rock; Metamorphic rocks
Abstract: ▾ In order to contribute to a better understanding of exhumation related retrogression processes ultrahigh-pressure (UHP) mafic and ultramafic rocks from the Chinese Continental Scientific Drilling (CCSD) in the Maobei eclogite body of the Sulu ultrahigh-pressure metamorphic belt in eastern China were studied for their magnetofabrics. Variably retrogressed eclogites and serpentinized ultramafic rocks were retrieved from the depth interval of 100 to 1000 m of the borehole. A vein network of irregular shaped veins with a retrograde metamorphic assemblage cuts across the eclogite foliation at both low and high angles. SEM imaging of the eclogites documents that magnetite associated with retrograde pargasitic amphiboles developed around shape-preferred garnet. SEM imaging of the serpentinized ultramafic rocks documents that magnetite rims grew around shape-preferred garnet and that magnetite formed within a mesh texture related to serpentinization. Syn-serpentinization magnetite growth increased bulk susceptibilities, but reduced anisotropy. Maximum susceptibility axes from both eclogites and serpentinized garnet-peridotites trend N-S, i.e. parallel with the stretching lineation as defined by olivine and omphacite grains. This implies that the magnetic fabric mimics the UHP fabric and survived retrogression and that the fabric is inherited from the UHP stage. As a consequence, retrogression was not associated with substantial ductile deformation and the mafic-ultramafic Maobei body behaved as a rigid body within a ductile deforming quartzo-feldspathic matrix during exhumation. Internal strain is restricted to brittle fracturing, associated fluid circulation and vein formation facilitating retrograde reactions in the mafic-ultramafic rocks. © 2008 Elsevier B.V. All rights reserved.
881.
Unlocking a cretaceous geologic and geophysical puzzle: Scientific drilling of Songliao Basin in northeast China
The Leading Edge,
28
(3)
340-344
2009
ISSN: 1070485X
Publisher: Society of Exploration Geophysicists
Keywords:▾
Earth (planet); Volcanoes, Geologic history; Geological events; Mass extinction; Mountain ranges; Northeast China; Scientific drilling; Volcanic eruptions; Western United States, Sea level, anoxic conditions; Cretaceous; drilling; mass extinction; mountain region; sea level; seawater; volcanic eruption; water temperature, Alps; Andes; California; China; Rocky Mountains; Sierra Nevada [California]; Songliao Basin; South America; United States
Abstract: ▾ Our Earth is a dynamic planet, changing on temporal scales ranging from millions of years required to complete a solid Earth cycle, or to form mountain ranges, to the few seconds required for a devastating earthquake or explosive volcanic eruptions. The Cretaceous was a period of great unrest in geologic history. It included a series of extraordinary global geological events - a significant increase of marine water temperature and the deposition of black shales; oceanic anoxia events (OAEs); biotic turnovers and mass extinctions; and the formation of many mountain ranges (California's Sierra Nevada and the Rockies in the western United States, the Andes in South America, and the Alps). Sea level rose during the mid-Cretaceous, covering about a third of the land area. Sea level was up to 250 m higher than at present. © 2009 Society of Exploration Geophysicists.
880.
The laguna potrok aike scientiic drilling project PASADO (ICDP expedition 5022)
Scientific Drilling
(8)
29 – 34
2009
879.
Uppermost Cretaceous sediments: Sedimentary microfacies and sedimentary environment evolution of Sifangtai Formation and Mingshui Formation in SK-Ⅰ (n).
Earth Science Frontiers,
16
(6)
85
2009
878.
Well site selecting, core section characteristics and distribution of the special lithological layers in CCSD-SK-In borehole, Songliao Basin.
Earth Science Frontiers,
16
(6)
104
2009
877.
876.
[English]
Active seismic imaging using microseismic events
Volume 5
,
Page 3266-3270
Publisher
Society of Petroleum Engineers
2009
Free University Berlin, GermanyKeywords:▾
Boreholes; Strike-slip faults, Directional migration; High resolution image; Internal structure; Microseismic events; San Andreas fault; Seismic imaging; Seismic reflections; Spatial characterization, Seismology
ISBN:
9781615672363
875.
[English]
Multi-dimensional, multi-variable, and multi-scale modeling of reservoir heterogeneities
Volume 2
,
Page 1039-1043
Publisher
Society of Petroleum Engineers
2009
University of Toronto, Canada; Geological Survey of Canada, CanadaISBN:
9781615672363
874.
[English]
Overview of energy-related studies of gas hydrates in Canada
2009
Geological Survey of Canada, P.O. Box 5000, Sidney, BC V8L 5S1, CanadaISBN:
9780841224414
873.
Impact cratering on volatile-rich targets: Some remarks related to the deep impact experiment
ESO Astrophysics Symposia,
2009201-211
2009
Abstract: ▾ The NASA Deep Impact experiment has important implications to better understand cratering processes on planetary bodies and the production and evolution of ejecta. This man-made impact of a solid Cu body on the nucleus of a comet fills the large gap existing between data derived from small-scale cratering experiments and large-scale field or remote sensing observations of craters. DI thus complements hydrocode modeling of cratering processes. The majority of cratering studies focus on solid silicate-rich targets rather than on porous, poorly consolidated and/or volatile-rich materials. However, volatile targets are common in the Solar System. The lessons learned from the DI collision with comet 9P/Tempel not only clarify the composition and physical properties of the cometary nucleus, but also can shed light on cratering mechanisms and evolution of plume and ejecta. © 2009 Springer-Verlag Berlin Heidelberg.
872.
The mineralogy of the Exmore beds- Chickahominy Formation boundary section of the Chesapeake Bay impact structure revealed in the Eyreville core
Special Paper of the Geological Society of America,
458723-746
2009
ISSN: 00721077
Publisher: Geological Society of America
Keywords:▾
Calcite; Crystalline materials; Diffraction; Feldspar; Glass; Grain size and shape; Kaolinite; Mica; Pyrites; Quartz; Sandstone; Sediments; Serpentine; Silicate minerals; X ray powder diffraction; Zeolites, Chesapeake bay impact structures; Clay-sized fractions; Diffraction bands; Disordered silicas; Glass alteration; Layered clay minerals; Least-squares matching; Quantifi cations, Core samples, clay mineral; depositional sequence; facies; glauconite; grain size; illite; impact structure; least squares method; mineral alteration; mineralogy; qualitative analysis; sedimentology; X-ray diffraction, Chesapeake Bay; United States
Abstract: ▾ Core descriptions, thin-section analyses, and X-ray powder diffraction analyses of whole-rock samples and clay-sized fractions were employed to interpret the sedimentology and mineralogy of synimpact Exmore beds and the overlying Chickahominy Formation. This study attempts to explain the origin and postdepositional alteration of materials in the Eyreville core from the central zone of the Chesapeake Bay impact crater. Samples were obtained from eight zones extending from core depths of 435 to 1471 m, with emphasis on the interval from 435 to 455 m, representing the upper Exmore beds and the lower Chickahominy Formation. Qualitative clay mineral determinations were aided by peak decomposition procedures to unravel overlapping diffraction bands, and quantifi cation was accomplished by least squares matching of actual and computed patterns. The major facies in approximate ascending order are suevite breccias, poorly sorted conglomerate and sandstone, and upward-fi ning glauconitic sandstone within the Exmore beds followed by parallel laminated sandy siltstone and claystone in the Chickahominy Formation. They all contain clay minerals (mica, smectites, and some serpentine, kaolinite, and chlorite) plus quartz and feldspar. Heulandite, pyrite, calcite, and disordered silica (partly representing nanofossils and microfossils) are present in the Chickahominy Formation. The boundary beds (upper 7 m) of the Exmore beds have higher clay contents but fewer varieties of expandable clay minerals than in the Chickahominy Formation. The Exmore beds are enriched in reworked glauconite, but there are no indications of heulandite, calcite, disordered silica, or pyrite, except in the very top of the 7-m-thick boundary bed interval. The clay fractions of the Eyreville materials are dominated by different species of expanding clay minerals (smectite, fi ne and coarsely crystalline nontronite, and fi ne and coarsely crystalline smectite-illite mixed-layered clay minerals), but dioctahedral mica and illite are also present. Amorphous material and minor amounts of quartz,chlorite, and mixed-layered smectite (0.95)/iron-rich illite (0.05) are common. The abundance of the clays in most intervals is highly variable due to the chaotic assemblage of sediments and crystalline materials from diverse sources. The boundary beds are dominated by a single smectitic mineral, nontronite, which is assumed to be the principal product of melt glass alteration. Amorphous material (melt glass) and nontronite are calculated to represent 13 vol% and 13-19 vol% of the sediments in this interval, respectively. Grain size, or clast size, has a major infl uence on mineralogical variability, i.e., when grain size (clast size) is large, the mineral content of adjacent samples is highly variable. © 2009 The Geological Society of America.
871.
The floating astronomical time scale for the terrestrial Late Cretaceous Qingshankou Formation from the Songliao Basin of Northeast China and its stratigraphic and paleoclimate implications
Earth and Planetary Science Letters,
278
(3-4)
308-323
2009
ISSN: 0012821XKeywords:▾
astronomical time scale (ATS); lacustrine anoxic event 1 (LAE1); Late Cretaceous; Milankovitch cycles; Songliao Basin, Astrophysics; Climate change; Fire hazards; Gamma rays; Oil fields; Oil shale; Organic carbon; Photosynthesis; Radioactivity logging; Shale oil; Stratigraphy; Weathering, Oil well logging, climate change; Cretaceous; cyclostratigraphy; Milankovitch cycle; mudstone; organic carbon; paleoclimate; source rock, Asia; China; Eurasia; Far East; Songliao Basin, Coniacian
Abstract: ▾ The Upper Cretaceous Qingshankou Formation (K2qn) in the Songliao Basin (SLB) of Northeast China consists of up to 550 m thick, lacustrine mudstone and shale that constitute one of the most important source rocks of the Daqing oil field. A high-resolution cyclostratigraphic analysis of the natural gamma-ray logging from 10 wells of the Qingshankou Formation (K2qn) reveals orbital cycles of precession (20 ka), obliquity (40 ka) and eccentricity (100 ka and 405 ka), providing strong evidence for astronomically driven climate changes in the Late Cretaceous terrestrial environments. Floating astronomical time scales (ATS) are established for all sections, which demonstrate variable durations of K2qn across the basin (1.09 Ma-5.20 Ma) and strong diachroneity of the lacustrine strata. Four periods of high depositional rates can be identified in the central parts of the basin, possibly recording deposition during times of sustained wet climate and high chemical weathering. An ATS established from well M206 in the central depression zone of the basin, where the most complete and stable Milankovitch cycles are present, suggests that the maximum duration of the K2qn is 5.20 Ma (from 94.27 Ma to 89.07 Ma; Late Cenomanian to Early Coniacian). The lacustrine anoxic event 1 (LAE1) at the Cenomanian-Turonian boundary lasted ~ 210-310 ka, during which the most prolific petroleum source rocks in SLB were deposited. The onset (~ 94.21-94.18 Ma) and duration (~ 210-310 Ka) of LAE1 in SLB are comparable to those of the oceanic anoxic event 2 (OAE2; onset at 94.21 Ma and duration of ~ 320-900 ka), suggesting that the same trigger mechanism, such as increased atmospheric CO2 from large-scale igneous activity, may have initiated high primary productivity and organic carbon burial in both marine and terrestrial systems. © 2008 Elsevier B.V. All rights reserved.
870.
Productivity cycles in Lake Hovsgol, NW Mongolia, during the last 1 Ma and the age model of the HDP-04 drill core record
Quaternary International,
205
(1-2)
111 – 125
2009
ISSN: 10406182Keywords:▾
Asia; Eurasia; Far East; Hvsgol Aymag; Lake Baikal; Mongolia; Russian Federation; Bacillariophyta; biostratigraphy; climate change; diatom; Holocene; interglacial; isotopic composition; lacustrine deposit; nitrogen; paleoclimate; paleoenvironment; Pleistocene; sediment core; total organic carbon
Abstract: ▾ Repetitive patterns in the records of total organic carbon (TOC), total nitrogen (TN) and δ13Corg observed in the Lake Hovsgol sediment section from HDP-04 drill core reflect past changes in productivity of Lake Hovsgol and in the isotopic composition of the lake's carbon pool. Lake Hovsgol productivity proxy signals are interpreted to represent the response of the Hovsgol lacustrine system to glacial-interglacial cycles of the Pleistocene. This interpretation is supported by the apparent orbitally-forced pattern in the TOC, TN and δ13Corg records of the past 250 ka in the BDP-96-2 drill core from neighboring Lake Baikal. The intervals with independent age control, such as the radiocarbon-dated last glacial-interglacial transition and the paleomagnetic reversals, make it evident that productivity proxy signals are reliable indicators of past cold-to-warm and warm-to-cold climate transitions, as seen from the agreement with the pattern of global climate change in marine δ18O records. The Brunhes/Matuyama reversal during the MIS 19 interglacial coincides with a distinct peak of TOC and TN in the Hovsgol record, similar to the signal during the Holocene interglacial. By contrast, the upper Jaramillo reversal in the Lake Hovsgol record occurs in a diatom-free calcareous interval characterized by minima in TOC, TN and by a 'glacial'-type range of δ13Corg values. In both Lake Baikal and Lake Hovsgol records, peaks in TOC and TN contents help distinguishing past interglacials and interstadials, and isotopically-heaviest δ13Corg values help identify past glacial intervals. An age model for the HDP-04 drill core section is proposed based on recognizing the repetitive patterns in Lake Hovsgol productivity and lithologic records as regional paleoclimate cycles of middle to late Pleistocene. Absolute dates and diatom biostratigraphic correlation ties to the Lake Baikal record are used as key controls. In the proposed age model, the interval 81-24 m in the HDP-04 sediment section below the major unconformity is correlated to MIS 27 through late MIS 13, whereas the upper 24 m of the HDP-04 section is suggested to have recovered the sedimentary record of late MIS 7 to MIS 1.