All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
2119.
Scientific Results of Geophysical Logging in the Upper Cretaceous Strata, CCSD SK-2 East Borehole in the Songliao Basin of Northeast China [松辽盆地科学钻探工程松科二井东孔上白垩统地球物理测井科学成果]
Acta Geoscientica Sinica,
39
(6)
679-690
2018
ISSN: 10063021
Publisher: Science Press
Abstract: ▾ The Continental Scientific Drilling Project in the Songliao Basin, a major scientific project, was aimed at solving a variety of scientific problems involved in resources on deep strata, paleoclimate and paleoenvironment. As the main borehole of this project, the SK-2 East Borehole was designed to reach a depth of 6 400 m to penetrate the Cretaceous strata until reaching the base of the basin. Geophysical logs played an important role in the subsequent geoscience researches because very few core samples were recovered over the Upper Cretaceous intervals (i.e., Spud 1 and Spud 2). After the borehole was officially drilled, 4 uncased and cased hole logging operations were carried out in the Upper Cretaceous intervals using advanced imaging logging tools. Comprehensive log evaluation was implemented systematically. The preliminary scientific results were summarized as follows: (1) Abundant logs including conventional logs special logs and CBL logs (more than 20 parameters) were obtained in situ, and continuous and standard petrophysical parameters profiles of the Upper Cretaceous interval were established; (2) Stratigraphic division, lithological identification and fine interpretation of sediments and structures were completed; (3) Hydrocarbon reservoirs in the Quantou Formation, source rocks in the Nenjiang and Qingshankou Formation, abnormally high radioactivity interval in the Nenjiang Formation, and potential geothermal development layers over the Upper Cretaceous strata were identified; (4) Favorable geophysical log indexes for paleoclimate analysis in the Qingshankou Formation were studied; (5) The key drilling engineering information including accurate temperature, caliper, borehole trajectory and cementing quality was provided in time. The scientific results are crucial for establishing the scientific scale of geophysical exploration in the Songliao Basin, investigating paleoclimate and paleoenvironment, and implementing drilling engineering, which have established good foundations for achieving the whole scientific goals of this drilling project. © 2018, Science Press. All right reserved.
2118.
Sample-scale carbon isotopic variability and diverse biomass in the Paleoproterozoic Zaonega Formation, Russia
Precambrian Research,
315222--231
2018
2117.
Salt precipitation and dissolution in the late Quaternary Dead Sea: Evidence from chemical and δ37Cl composition of pore fluids and halites
Earth and Planetary Science Letters,
487127-137
2018
ISSN: 0012821X
Publisher: Elsevier B.V.
Keywords:▾
Curve fitting; Dissolution; Distillation; Glacial geology; Lakes; Precipitation (chemical); Reservoirs (water); Salt tectonics; Sodium chloride, Chemical compositions; Dead sea; Fractionation factors; ICDP; Rayleigh distillation; Residual solutions; Salt diapirs; Salt precipitation, Chloride minerals, chemical composition; chlorine isotope; dissolution; fluid composition; fractionation; halite; hydrochemistry; precipitation (chemistry); Quaternary; reservoir; salt dome, Dead Sea; Israel; Mount Sedom; Southern District
Abstract: ▾ The chemical composition and δ37Cl of pore fluids from the ICDP core drilled in the deepest floor of the terminal and hypersaline Dead Sea, and halites from the adjacent Mount Sedom salt diapir, are used to establish the dynamics of halite precipitation and dissolution during the last interglacial and glacial periods. Between ∼132 and 116 thousand years ago (ka) halites precipitated in the lake resulting in the expulsion of Na+ and Cl− from the residual solution. Over 50% of the Cl− reservoir was removed, resulting in a decrease in the Na/Cl ratio from 0.57 to 0.19. This process was accompanied by a decrease in δ37Cl values in the precipitating halites and the associated residual Cl− in the lake. The observed decrease fits a Rayleigh distillation curve with a fractionation factor of Δ(NaCl–Dead Sea solution) = +0.32‰ (±0.12) determined in the present study. This behavior implies negligible contribution of external sources of Cl− to the lake during the main peak of the last interglacial, MIS5e. Subsequently, during the last glacial (ca. 117 to 17 ka) dissolution of halite took place, the Na+ and Cl− inventory were replenished, accompanied by an increase in Na/Cl from 0.21 to 0.55 and in the δ37Cl values from −0.46‰ to −0.12‰. While the lake underwent significant dilution during that time, the decrease in salinity was somewhat suppressed by the dissolution of the halite which was mostly derived from Mount Sedom salt diapir. © 2018 Elsevier B.V.
2116.
Integrative taxonomy of freshwater ostracodes (Crustacea: Ostracoda) of the Yucatán Peninsula, implications for paleoenvironmental reconstructions in the northern Neotropical region
Zoologischer Anzeiger,
27520 – 36
2018
ISSN: 00445231
Publisher: Elsevier GmbH
Keywords:▾
Yucatan Peninsula; Alicenula; Crustacea; Cypretta; Cyprididae; Cypridopsis; Darwinulidae; Ostracoda; crustacean; DNA; fossil assemblage; gene expression; Neotropical Region; paleoecology; paleoenvironment; reconstruction; taxonomy
Abstract: ▾ A three-step integrative taxonomy approach combining molecular, morphological and ecological methods was successfully used to delimit species boundaries within three freshwater ostracode taxa of the Yucatán Peninsula (Mexico): Darwinulidae, Cypretta and Cypridopsis. These species groups were selected because they are well-suited paleobioindicators for late Pleistocene-early Holocene climatic reconstructions in the region, but their high inter-population morphological variability in recent communities represents a challenge for accurate transfer of information to fossil assemblages. As a first step, we analyzed the congruence of two genes of different inheritance, the mitochondrial COI (cytochrome c-oxidase subunit 1), and the nuclear 18S rDNA (small-subunit rDNA). Second, we tested the lineages discriminated for concordant differentiation in morphology, using morphometry of the carapace and typological analysis of the appendages. The third step assessed the association of occurrences and abundances of lineages to environmental variables. The integration of these methods revealed six hidden species within clades previously considered as a single widely distributed nominal species. Of these, Cypretta elongata sp. nov. and Alicenula yucatanensis sp. nov. are herein formally named and described given their morphological distinctness. Three species of Cypridopsis: Cypridopsis sp. [Ca1 ECO-CH-Z-09396], Cypridopsis sp. [Ca2 ECO-CH-Z-09398], Cypridopsis sp. [Ca3 ECO-CH-Z-09401] and a species that may represent a new genus, Cyprididae sp. [Ca1 ECO-CH-Z-09402], are allocated to a confirmed candidate full species status. Cypretta maya and Cypretta sp., considered a priori as separate species, are recognized as a single species with phenotypic plasticity, attributed to its broad ecological tolerances. For paleoenvironmental reconstructions these results have relevance because the particular carapace morphology of the new species can be correlated with specific ecological traits, thus constituting a potential tool for refining interpretations of fossil assemblages. © 2018 Elsevier GmbH
2115.
Influence of CO2 degassing on the microbial community in a dry mofette field in Hartoušov, Czech Republic (Western Eger Rift)
Frontiers in Microbiology,
9
(NOV)
2018
ISSN: 1664302X
Publisher: Frontiers Media S.A.
Keywords:▾
carbon dioxide; RNA 16S; Acidithiobacillus; amplicon; Article; bioinformatics; DNA extraction; DNA purification; dsrB gene; gasification; gene; gene amplification; geochemical analysis; microbial community; nonhuman; pH; population abundance; real time polymerase chain reaction; stratigraphy
Abstract: ▾ The Cheb Basin (CZ) is a shallow Neogene intracontinental basin filled with fluvial and lacustrine sediments that is located in the western part of the Eger Rift. The basin is situated in a seismically active area and is characterized by diffuse degassing of mantle-derived CO2 in mofette fields. The Hartoušov mofette field shows a daily CO2 flux of 23-97 tons of CO2 released over an area of 0.35 km2 and a soil gas concentration of up to 100% CO2. The present study aims to explore the geo-bio interactions provoked by the influence of elevated CO2 concentrations on the geochemistry and microbial community of soils and sediments. To sample the strata, two 3-m cores were recovered. One core stems from the center of the degassing structure, whereas the other core was taken 8 m from the ENE and served as an undisturbed reference site. The sites were compared regarding their geochemical features, microbial abundances, and microbial community structures. The mofette site is characterized by a low pH and high TOC/sulfate contents. Striking differences in the microbial community highlight the substantial impact of elevated CO2 concentrations and their associated side effects on microbial processes. The abundance of microbes did not show a typical decrease with depth, indicating that the uprising CO2-rich fluid provides sufficient substrate for chemolithoautotrophic anaerobic microorganisms. Illumina MiSeq sequencing of the 16S rRNA genes and multivariate statistics reveals that the pH strongly influences microbial composition and explains around 38.7% of the variance at the mofette site and 22.4% of the variance between the mofette site and the undisturbed reference site. Accordingly, acidophilic microorganisms (e.g., OTUs assigned to Acidobacteriaceae and Acidithiobacillus) displayed a much higher relative abundance at the mofette site than at the reference site. The microbial community at the mofette site is characterized by a high relative abundance of methanogens and taxa involved in sulfur cycling. The present study provides intriguing insights into microbial life and geo-bio interactions in an active seismic region dominated by emanating mantle-derived CO2-rich fluids, and thereby builds the basis for further studies, e.g., focusing on the functional repertoire of the communities. However, it remains open if the observed patterns can be generalized for different time-points or sites. © 2018 Frontiers Media S.A. All Rights Reserved.
2114.
Centennial-scale vegetation dynamics and climate variability in SE Europe during Marine Isotope Stage 11 based on a pollen record from Lake Ohrid
Quaternary Science Reviews,
19020 – 38
2018
ISSN: 02773791
Publisher: Elsevier Ltd
Keywords:▾
Atlantic Ocean; Atlantic Ocean (North); Balkans; Europe; Italy; Lake Ohrid; Lazio; Mediterranean Sea; Mediterranean Sea (East); Vico; Forestry; Glacial geology; Isotopes; Lakes; Repair; Vegetation; Abrupt climate change; Balkan peninsulas; Climate reconstruction; Eastern Mediterranean; Lake Ohrid; Marine isotope stages; Southern Europe; Tephrostratigraphy; Terrestrial ecosystems; Vico tephra; chronology; climate change; climate variation; global climate; ice-rafted debris; interglacial; marine isotope stage; paleoclimate; palynology; pollen; precipitation (climatology); reconstruction; sediment core; tephra; vegetation dynamics; Climate change
Abstract: ▾ To better understand climate variability during Marine Isotope Stage (MIS) 11, we here present a new, centennial-scale-resolution pollen record from Lake Ohrid (Balkan Peninsula) derived from sediment cores retrieved during an International Continental Scientific Drilling Program (ICDP) campaign. Our palynological data, augmented by quantitative pollen-based climate reconstructions, provide insight into the vegetation dynamics and thus also climate variability in SE Europe during one of the best orbital analogues for the Holocene. Comparison of our palynological results with other proxy data from Lake Ohrid as well as with regional and global climate records shows that the vegetation in SE Europe responded sensitively both to long- and short-term climate change during MIS 11. The chronology of our palynological record is based on orbital tuning, and is further supported by the detection of a new tephra from the Vico volcano, central Italy, dated to 410 ± 2 ka. Our study indicates that MIS 11c (∼424–398 ka) was the warmest interval of MIS 11. The younger part of the interglacial (i.e., MIS 11b–11a; ∼398–367 ka) exhibits a gradual cooling trend passing over into MIS 10. It is characterized by considerable millennial-scale variability as inferred by six abrupt forest-contraction events. Interestingly, the first forest contraction occurred during full interglacial conditions of MIS 11c; this event lasted for ∼1.7 kyrs (406.2–404.5 ka) and was characterized by substantial reductions in winter temperature and annual precipitation. Most notably, it occurred ∼7 ka before the end of MIS 11c and ∼15 ka before the first strong ice-rafted debris event in the North Atlantic. Our findings suggest that millennial-scale climate variability during MIS 11 was established in Southern Europe already during MIS 11c, which is earlier than in the North Atlantic where it is registered only from MIS 11b onwards. © 2018 Elsevier Ltd
2113.
Cementing technology for ultra-high temperature well Songke-2
钻井液与完井液,
35
(2)
92-97
2018
ISSN: 10015620
Publisher: 钻井液与完井液
Abstract: ▾ A cement slurry used to deal with difficulties cementing the exploratory well Songke-2 in main land China, has been formulated with a quadripolymer filter loss reducer and a terpolymer phosphonate retarding agent to improve its thermal stability and avoid the risks of “thermal thinning” of the cement slurry. The filter loss and thickening time of the cement slurry were controlled to satisfy the needs of cementing ultra-high temperature wells by adjusting the concentrations of the two additives. Meanwhile, based on particle sizing and the close-packing principle, the particle sizes and concentration of silica sand were optimized, adjusting the ratio of silicon over calcium closing to 1, thereby preventing the decaying of the late-stage strength of set cement at ultra-high temperatures. Furthermore, an elastic tough material developed with particles and fibers was used to enhance the elasticity and toughness of the cement slurry. By optimizing the ratio of these additives, a cement slurry able to tolerate 260 ℃ well temperature was designed. This cement slurry has good stability, density difference between the upper and the lower parts of the cement slurry less than 0.03 g/cm3, thickening time between 200 min and 420 min, filter loss less than 100 mL, 48 h compressive strength greater than 20 MPa, and 7 d compressive strength greater than 38 MPa. The late-stage strength of the set cement is not declining. By optimizing the liner hanging and cementing techniques, and strictly controlling cement slurry density, the integrity of the formations penetrated by the well was maintained, without being fractured during cementing operations. Using high temperature high efficiency flushing spacers, the displacing efficacy was increased, and job safety and cementing job quality were ensured. Well cementing has been performed successfully with high job quality on the Well Songke-2, whose static bottom hole temperature is 260 ℃, and circulating bottom hole temperature 210 ℃. © 2018, The Editorial Board of Drilling Fluid & Completion Fluid. All right reserved.
2112.
Deep Continental Scientific Drilling Engineering Project in Songliao Basin: progress in Earth Science research
China Geology,
1
(2)
173-186
2018
ISSN: 20965192
Publisher: KeAi Communications Co.
Abstract: ▾ The Songke No.2 well (eastern hole) (referred to as Well SK-2), one of the “two wells and four holes” of the Deep Continental Scientific Drilling Engineering Project in the Songliao Basin, is in Anda City, Heilongjiang Province, and was officially completed on May 26, 2018. The scientific goals of Well SK-2 cover four aspects: paleoclimate research, resource and energy exploration, primary geological research, and development of deep earth exploration techniques. Since the official commencement of drilling in 2014, the Well SK-2 scientific drilling engineering team has organized and implemented drilling for coring, in situ logging, chemical analysis of core elements, and deep structural exploration around the well. Currently, the following preliminary scientific research progress has been made: 4334.81 m in situ core data has been obtained; the centimeter-level high-resolution characterization of the most complete and continuous Cretaceous continental strata ever unearthed has been completed, and the standard profile of continental strata has been initially established; the unconventional natural gas resources and basin-type hot dry rocks in the deep Songliao Basin were found to have good prospects for exploration and development; the climatic evolutionary history of the Cretaceous continental strata was rebuilt for the first time, covering hundreds of thousands to millions of years, and the major events of Cretaceous climate fluctuations have been discovered; all these reveal strong evidence for the subduction and aggregation of paleo-ocean plates, providing a theoretical basis for the re-recognition of the genesis of the Songliao Basin and for deep earth oil and gas exploration. The implementation of the Deep Continental Scientific Drilling Engineering Project in the Songliao Basin is of great significance for exploring the mysteries of the Earth and solving major problems such as those related to the deep energy environment. It is a solid step along the road of “going deep into the Earth”. © 2019 Elsevier B.V.
2111.
Deep continental scientific drilling engineering in Songliao Basin: Progress in earth science research
Geology in China,
45
(4)
641-657
2018
ISSN: 10003657
Publisher: Editorial Board of Geology in China
Keywords:▾
Cretaceous; drilling; Earth science; energy resource; geographical research; hydrocarbon exploration; Pacific plate; paleoclimate, China; Heilongjiang; Songliao Basin
Abstract: ▾ The eastern borehole of Well SK-2, among the "two wells and four boreholes" of the deep continental scientific drilling engineering in Songliao Basin, is situated in Anda of Heilongjiang Province and was finished officially on May 26th, 2018. Well SK- 2 mainly focused on four scientific objections, i.e., paleoclimate research, resource and energy exploration, basic geological research and development of deep exploration technology. During the process if drilling which began in 2014, drilling, coring, logging, analysis of chemical element and structural exploration of surrounding areas were carried out during the SK-2 drilling engineering, and some preliminary progresses were made in scientific research: 4134.8 m-long in-situ core data were acquired, and the most complete and continuous continental strata of the cretaceous were described with high resolution of centimeter-level, thus building the standard continental stratigraphic profile. Besides, evolution history of the continental facies in the Cretaceous period from scale of one million to one hundred thousand years was reconstructed for the first time, and an important climatic event of the Cretaceous was found. Apart from these achievements, evidence of Paleo- Pacific plate subduction and convergence in the deep was found, which contributes to genetic re- recognition and deep hydrocarbon exploration in Songliao basin. The implementation of deep continental scientific drilling engineering in Songliao Basin is of great significance in exploring the earth's mystery, seeking for deep energy and solving environmental problems. It is considered to be a solid step in the way of heading deep of the earth. © 2018 Editorial Board of Geology in China. All rights reserved.
2110.
Deccan volcanism caused coupled pCO2 and terrestrial temperature rises, and pre-impact extinctions in northern China
Geology,
46
(3)
271-274
2018
ISSN: 00917613
Publisher: Geological Society of America
DOI:10.1130/G39992.1
Keywords:▾
Chicxulub impact; Climate history; Climate record; Climatic fluctuations; Clumped isotopes; K-pg boundaries; Mass extinction; Temperature rise, Geology, carbon dioxide; Cretaceous-Paleogene boundary; mass extinction; paleosol; volcanism, China; Songliao Basin, algae; Characeae; Ostracoda
Abstract: ▾ Evaluating the terrestrial climate record provides a critical test of the roles of Chicxulub impact and Deccan Traps volcanism during the Cretaceous-Paleogene (K-Pg) mass extinction. Most evidence came from marine records, but our new clumped isotopes data from paleosol carbonates in the Songliao Basin provide a terrestrial climate history from northern China. This reveals there was a pre-impact warming caused by the onset of Deccan Traps volcanism, whereas the following short-term cooling then another warming episode were likely caused by Chicxulub impact and post-boundary volcanism. Our study suggests that the pCO2 levels were probably the main control on the latest Cretaceous cooling and the climatic fluctuations across the K-Pg boundary interval in northern China. In the Songliao Basin, the pre-impact Deccan Traps volcanism links to losses of half of the lacustrine algae species (charophytes) and almost all of the lacustrine ostracodes; this suggests that the Deccan Traps volcanism had already destabilized the ecosystem and caused extinctions prior to the Chicxulub impact. © 2018 Geological Society of America.
2109.
Dead Sea pollen provides new insights into the paleoenvironment of the southern Levant during MIS 6–5
Quaternary Science Reviews,
18815-27
2018
ISSN: 02773791
Publisher: Elsevier Ltd
Keywords:▾
Chloride minerals; Fertilizers; Glacial geology; Landforms; Moisture; Sodium chloride; Vegetation, Eastern Mediterranean; Human migration; Lake levels; Last interglacial; Paleovegetation, Lakes, deciduous tree; deep drilling; desert; dicotyledon; grass; interglacial; lake level; Last Glacial; marine isotope stage; migration; paleobotany; paleoclimate; paleoenvironment; pollen; sediment analysis; steppe; warming, Dead Sea; Levant; Mediterranean Region; Mediterranean Sea; Mediterranean Sea (East), Pistacia vera; Quercus
Abstract: ▾ The paleoclimate of the southern Levant, especially during the last interglacial (LIG), is still under debate. Reliable paleovegetation information for this period, as independent evidence to the paleoenvironment, was still missing. In this study, we present a high-resolution pollen record encompassing 147–89 ka from the Dead Sea deep drilling core 5017-1A. The sediment profile is marked by alternations of laminated marl deposits and thick massive halite, indicating lake-level fluctuations. The pollen record suggests that steppe and desert components predominated in the Dead Sea surroundings during the whole investigated interval. The late penultimate glacial (147.3–130.9 ka) and early last glacial (115.5–89.1 ka) were cool and relatively dry, with sub-humid conditions confined to the mountains that sustained moderate amounts of deciduous oaks. Prior to the LIG optimum, a prevalence of desert components and a concomitant increase in frost-sensitive pistachio trees demonstrate the occurrence of an arid initial warming phase (130.9–124.2 ka). The LIG optimum (124.2 ka–115.5 ka) was initiated by an abrupt grass expansion that was followed by a rapid spread of woodlands in the mountains due to increased moisture availability. The remarkable sclerophyllous expansion points to a strong seasonal moisture deficit. These results contradict previous Dead Sea lake-level investigations that suggested pluvial glacials and a warm, dry LIG in the southern Levant. Prominent discrepancies between vegetation and Dead Sea lake stands are also registered at 128–115 ka, and the potential causes are discussed. In particular, while the pollen spectra mirror increased effective moisture during the LIG optimum, the massive halite deposition is indicative of an extremely low lake level. Given that the climate amelioration triggered the migration of early modern humans to the southern Levant, we speculate that the diverse ecosystems in the region provided great potential for their residence. Across the eastern Mediterranean region, an analogous vegetation succession pattern is observed. © 2018 Elsevier Ltd
2108.
Coupled δ18O-δ17O and 87Sr/86Sr isotope compositions suggest a radiogenic and 18O-enriched magma source for Neapolitan volcanoes (Southern Italy)
Lithos,
316-317199 – 211
2018
ISSN: 00244937
Publisher: Elsevier B.V.
Keywords:▾
Campania [Italy]; Campi Flegrei; Italy; Napoli [Campania]; Somma Vesuviana; crustal structure; isotopic composition; magma; mantle structure; oxygen isotope; stable isotope; strontium isotope; volcano
Abstract: ▾ The origin of large variations in stable and radiogenic isotope compositions of magmas erupted from the Neapolitan volcanoes, including Somma-Vesuvius and Campi Flegrei (Southern Italy), has always been contentious. Indeed, the role and relative importance of sediment subduction versus crustal assimilation to explain the chemical and isotopic variations of the erupted magmas remain unclear. Isotopic disequilibrium between minerals and their host indicate that bulk rock analyses are incapable of constraining the isotopic composition of the source. Therefore, we use isotopic (87Sr/86Sr, 18O/16O and 17O/16O) data on separated minerals (feldspar, clinopyroxene and olivine phenocrysts) from pyroclastic successions and lava flows of the Neapolitan volcanic area (Phlegrean Volcanic District and Somma-Vesuvius complex) to better constrain magmatic oxygen and strontium isotope ratios. Magmatic values recalculated from δ18O of olivine and clinopyroxene phenocrysts range from typical mantle values of 5.2‰ to almost 9‰ relative to SMOW. These compositions are very different from those of typical mantle sources. In order to assess the degree of magma evolution from which these minerals formed, the Mg# of clinopyroxene and olivine were converted into host melt Mg#, resulting in the range 44 to 76. Simple assimilation of silicic crustal rocks is difficult to reconcile with the mafic nature of these estimated host magma compositions. This indicates that some mafic, mantle-derived magmas, having unusually heavy oxygen isotope (up to ~9‰) and high Sr isotope compositions (0.7050 to 0.7085), must exist. Crustal assimilation of carbonates can be excluded by the lack of a link between isotopes and major and trace element signatures. Assimilation of either Hercynian-like crust or altered pyroclastic rocks, however, cannot be ruled out completely. However, assimilation of partial melts from a Hercynian-like crust would have to be ~12% and ~21% to explain the heavy oxygen isotope values of Campi Flegrei and Somma-Vesuvius, respectively. Such degrees of assimilation are unlikely since the magmas are either too mafic or too alkaline to be consistent with such high proportion of crustal components. Other, less mafic Campi Flegrei, Somma-Vesuvius and Ischia magmas with more typical mantle oxygen isotopes, have been possibly generated in a mantle source affected by minor contamination by pelagic and carbonate sediments and subsequent assimilation of Hercynian-like crust. Sr-O mixing models indicate that such magmas were derived from a mantle source that was contaminated by up to 10% of a 1:1 mixture of pelagic and carbonate sediments. These findings together demonstrate the highly complex and varied magma sources in the Campania volcanic district. Triple oxygen isotope variations (Δ17O), based on measurements of both 18O/16O and 17O/16O ratios in potential assimilants are in agreement with these conclusions. © 2018 Elsevier B.V.
2107.
Corrigendum to Effect of methane hydrate morphology on compressional wave velocity of sandy sediments: Analysis of pressure cores obtained in the Eastern Nankai Trough (Marine and Petroleum Geology (2015) 66(Part 2) (425–433) (S0264817215000537) (10.1016/j.marpetgeo.2015.02.021))
Marine and Petroleum Geology,
91662-663
2018
ISSN: 02648172
Publisher: Elsevier Ltd
Abstract: ▾ The authors would like to replace the section 1. 1ntroduction (pp. 425) with the following: Introduction Methane hydrate, which is a crystalline compound formed from methane and water, is found in arctic and marine continental margin sediments worldwide (Sloan and Koh, 2008). The P-wave velocity of hydrate-bearing sediments is higher than that of hydrate-free unconsolidated sediments (e.g., Yuan et al., 1996), and laboratory experiments have shown that there is a strong relationship between the P-wave velocity and hydrate saturation (e.g., Berge et al., 1999). Through the comparison with model predictions such as those of Dvorkin et al. (2000), it was found that this relationship depends on the hydrate morphology, such as grain coating, cementing, pore-filling, and sediment frame component (or load-bearing) within the pore space (M. Lee et al., 1996; Berge et al., 1999; Reister, 2003; Yun et al., 2005; Priest et al., 2009; J. Lee et al., 2010; Hu et al., 2010, Li et al., 2011; Best et al., 2013; Kim et al., 2013a). This suggests that the P-wave velocity obtained from logging and seismic surveys can be used to estimate the in situ hydrate saturation if the hydrate morphology in actual reservoirs is revealed. P-wave velocity changes during CH4eCO2 replacement in hydrates have also been studied to estimate the sediment stiffness (Espinoza and Santamarina, 2011; Liu et al., 2013). It is therefore important to understand the relationship between the P-wave velocity, hydrate saturation, and hydrate morphology because these properties are deeply linked to the physical properties of hydrate-bearing sediments, such as their permeability, thermal properties, electrical conductivity, and shear strength (Waite et al., 2009; Santamarina and Ruppel, 2010). Quantitative detection of methane hydrate in natural sediments has been attempted over the years. Wood et al. (1994) analyzed seismic interval velocities at the Blake Ridge for quantitative detection of methane hydrate. Chand et al. (2004) compared P- wave velocities predicted by four models and field data from the Mallik field in the Mackenzie Delta and the Blake Ridge. At the Mallik field, Carcione and Gei (2004) estimated hydrate saturation from well logging data and vertical seismic profiles by assuming that the hydrate filled pore space (pore-filling). Dash and Spence (2011) estimated hydrate saturation at the northern Cascadia margin using P-wave and S-wave velocities. They concluded that the hydrate is distributed as part of the load-bearing matrix. For other areas, such as the Nankai Trough, Mount Elbert, the KrishnaeGodavari basin, the Tsushima Basin, and the Shenhu area of the South China Sea, estimations of hydrate saturation have also been conducted (Inamori et al., 2010; Lee and Collett, 2011; Kim et al., 2013b; Shankar and Riedel, 2011; Lee and Collett, 2013; Wang et al., 2014). Hydrate morphology was estimated as load-bearing at the Nankai Trough, Mount Elbert, and the KrishnaeGodavari basin, whereas it was estimated to be pore-filling at the Tsushima Basin. Winters et al. (2004) reported that the mildly-disturbed samples recovered from the 2L-38 well at the Mallik field are best modeled as part of the sediment frame (load-bearing). Laboratory experiments using artificial cores have also provided insight into the relationship between P-wave velocity and hydrate saturation; however, there are some limitations to the use of artificial cores in estimating hydrate saturation in natural sediments. One of the reasons is that it is difficult to control hydrate morphology in such a way as to mimic natural features in artificial cores. Hydrate formed in a gas-rich environment, which is a conventional method used in laboratory studies, generally shows a cementing morphology (Winters et al., 2004; Priest et al., 2005, 2006). In contrast, hydrate formed from methane dissolved in the pore fluid, which is considered as common in natural environments, may not show a cementing morphology (Spangenberg et al., 2005, 2008; Winters et al., 2007). Using a non-methane hydrate former, Yun et al. (2005) and Lee et al. (2010) documented a transition between pore-filling and load-bearing hydrates at saturation of ~40%e50% of pore space. Gas hydrate morphology in natural sediments is depends on the hydrate occurrence mechanism; however, it is difficult to know the occurrence mechanism for each reservoir. Analysis of logging data seems to be effective in estimating the actual relationship between P-wave velocity, hydrate saturation, and hydrate morphology in natural sediments. However, the spatial resolution of P-wave velocity data and hydrate saturation data, as estimated from resistivity logging, is larger than that of core data, and the various datasets are not usually entirely coincident. Thus, cross-plots of P- wave velocity and hydrate saturation are often so scattered that it is difficult to accurately constrain the hydrate morphology. In addition, the frequency used for in situ exploration is much lower than that used in laboratory experiments, which results in differences in the depth and spatial resolution of measurements. In situ exploration data are spatially-averaged and appropriate for the determination of the hydrate distribution in bulk sediments. However, such data are difficult to apply to the investigation of local properties, such as the pore space hydrate morphology. Consequently, high frequency laboratory experiments using natural sediments are more favorable for the analysis of pore space hydrate morphology. Pressure core analysis technologies now enable the study of relatively undisturbed samples recovered from hydrate-bearing natural sediments, and pressure core analyses of P-wave veloc ities have been conducted for hydrate-bearing natural sediments (Yun et al., 2006, 2010, 2011; Schultheiss et al., 2011). Lee et al. (2013) successfully determined the relationship between P-wave velocity and hydrate saturation from pressure cores recovered from the Tsuhima Basin. They concluded that the hydrate morphology is pore-filling at low hydrate saturations, but gradually deviates from pore-filling toward cementation as hydrate saturation increases, in accordance with studies of Yun et al. (2005) and Lee et al. (2010). They used the Pressure Core Analysis and Transfer System (PCATS) developed by Geotek Ltd. (Schultheiss et al., 2011) to measure P- wave velocity through the core liner at high resolution. However, the study noted that the data resolving hydrate saturation was much lower than that of P-wave velocity because hydrate saturation was calculated based on a dissociation experiment conducted on the whole core including both high and low P-wave velocity sections (Lee et al., 2013). In this study, a newly developed pressure core cutting, manipulating, and analyzing system was used to overcome the discrepancy of data resolution between P-wave velocity and hydrate saturation. P-wave velocity was measured by the PCATS at a high resolution using pressure cores recovered from the Eastern Nankai Trough offshore Japan. After the P-wave velocity measurements, the cores were cut into pieces under pressure for separate P-wave velocity intervals on the basis of visual observation enabled by our pressure core system. To obtain high resolution hydrate-saturation data, each sub-sampled core was depressurized and the gas volume was measured. By comparing experimental data with physical model predictions, hydrate morphology in pore space was studied in detail. The authors would like to apologise for any inconvenience caused. DOI of original article: dx.doi.org/10.1016/j.marpetgeo.2015.02.021 © 2018
2106.
Controls on fault zone structure and brittle fracturing in the foliated hanging wall of the Alpine Fault
Solid Earth,
9
(2)
469--489
2018
ISSN: 18699510
Publisher: Copernicus GmbH
Keywords:▾
Anisotropy; Core drilling; Damage detection; Drills; Fracture; Guided electromagnetic wave propagation; Hierarchical systems; Rock pressure, Fault zone structures; High confining pressure; Large displacements; Low confining pressure; Low velocity zones; Mechanical anisotropy; Parallel fractures; X-ray computed tomography, Computerized tomography, brittle fracture; data set; fault zone; foliation; fracture orientation; hanging wall; permeability; seismic velocity, Alpine Fault Zone; New Zealand; South Island
Abstract: ▾ Three datasets are used to quantify fracture density, orientation, and fill in the foliated hanging wall of the Alpine Fault: (1) X-ray computed tomography (CT) images of drill core collected within 25gm of its principal slip zones (PSZs) during the first phase of the Deep Fault Drilling Project that were reoriented with respect to borehole televiewer images, (2) field measurements from creek sections up to 500gm from the PSZs, and (3) CT images of oriented drill core collected during the Amethyst Hydro Project at distances of ĝ1/4 g0.7-2gkm from the PSZs. Results show that within 160gm of the PSZs in foliated cataclasites and ultramylonites, gouge-filled fractures exhibit a wide range of orientations. At these distances, fractures are interpreted to have formed at relatively high confining pressures and/or in rocks that had a weak mechanical anisotropy. Conversely, at distances greater than 160gm from the PSZs, fractures are typically open and subparallel to the mylonitic or schistose foliation, implying that fracturing occurred at low confining pressures and/or in rocks that were mechanically anisotropic. Fracture density is similar across the g1/4 g500gm width of the field transects. By combining our datasets with measurements of permeability and seismic velocity around the Alpine Fault, we further develop the hierarchical model for hanging-wall damage structure that was proposed by Townend et al. (2017). The wider zone of foliation-parallel fractures represents an outer damage zone that forms at shallow depths. The distinct g160gm wide interval of widely oriented gouge-filled fractures constitutes an inner damage zone. This zone is interpreted to extend towards the base of the seismogenic crust given that its width is comparable to (1) the Alpine Fault low-velocity zone detected by fault zone guided waves and (2) damage zones reported from other exhumed large-displacement faults. In summary, a narrow zone of fracturing at the base of the Alpine Fault's hanging-wall seismogenic crust is anticipated to widen at shallow depths, which is consistent with fault zone flower structure models. © Author(s) 2018.
2105.
Comment on “The Campi Flegrei Deep Drilling Project (CFDDP): New Insight on Caldera Structure, Evolution and Hazard Implications for the Naples Area (Southern Italy)” by G. De Natale et al.
Geochemistry, Geophysics, Geosystems,
19
(7)
2283 – 2288
2018
ISSN: 15252027
Publisher: Blackwell Publishing Ltd
Keywords:▾
Geochronology; Stratigraphy; Caldera; Campi Flegrei; Deep drilling; Fault model; Geological evolution; Southern Italy; Stratigraphic data; Volcanic areas; Faulting
Abstract: ▾ The paper by De Natale et al. (2016, https://doi.org/10.1002/2015GC006183) reported new stratigraphic and geochronological data for a borehole located at Campi Flegrei volcanic area. The authors failed to mention several significant articles on the geological evolution of the region and proposed an interpretation of their data according to the caldera model. Herein, we provide tectonic and stratigraphic data to support a fault model of ignimbrite emission. This comment will also show the inconsistency of the proposed Campi Flegrei caldera. ©2018. American Geophysical Union. All Rights Reserved.
2104.
Colorado Plateau Coring Project, Phase I (CPCP-I): A continuously cored, globally exportable chronology of Triassic continental environmental change from western North America
Scientific Drilling,
2415-40
2018
ISSN: 18168957
Publisher: Copernicus GmbH
Keywords:▾
Computerized tomography; Exploratory geochemistry; Forestry; Lead alloys; Recovery; Sedimentology; Silicate minerals; Stratigraphy; Thallium alloys; Zircon, Additional sampling; Azimuthal orientation; Environmental change; Federal governments; Global environmental change; Rutgers University; Sedimentary structure; University of Texas, Magnetic polarity
Abstract: ▾ Phase 1 of the Colorado Plateau Coring Project (CPCP-I) recovered a total of over 850m of stratigraphically overlapping core from three coreholes at two sites in the Early to Middle and Late Triassic age largely fluvial Moenkopi and Chinle formations in Petrified Forest National Park (PFNP), northeastern Arizona, USA. Coring took place during November and December of 2013 and the project is now in its post-drilling science phase. The CPCP cores have abundant detrital zircon-producing layers (with survey LA-ICP-MS dates selectively resampled for CA-ID-TIMS U-Pb ages ranging in age from at least 210 to 241 Ma), which together with their magnetic polarity stratigraphy demonstrate that a globally exportable timescale can be produced from these continental sequences and in the process show that a prominent gap in the calibrated Phanerozoic record can be filled. The portion of core CPCP-PFNP13-1A for which the polarity stratigraphy has been completed thus far spans ~ 215 to 209Ma of the Late Triassic age, and strongly validates the longer Newark-Hartford Astrochronostratigraphic-calibrated magnetic Polarity Time-Scale (APTS) based on cores recovered in the 1990s during the Newark Basin Coring Project (NBCP). Core recovery was ~ 100% in all holes (Table 1). The coreholes were inclined ~ 60-75° approximately to the south to ensure azimuthal orientation in the nearly flat-lying bedding, critical to the interpretation of paleomagentic polarity stratigraphy. The two longest of the cores (CPCP-PFNP13-1A and 2B) were CT-scanned in their entirety at the University of Texas High Resolution X-ray CT Facility in Austin, TX, and subsequently along with 2A, all cores were split and processed at the CSDCO/LacCore Facility, in Minneapolis, MN, where they were scanned for physical property logs and imaging. While remaining the property of the Federal Government, the archive half of each core is curated at the NSF-sponsored LacCore Core Repository and the working half is stored at the Rutgers University Core Repository in Piscataway, NJ, where the initial sampling party was held in 2015 with several additional sampling events following. Additional planned study will recover the rest of the polarity stratigraphy of the cores as additional zircon ages, sedimentary structure and paleosol facies analysis, stable isotope geochemistry, and calibrated XRF core scanning are accomplished. Together with strategic outcrop studies in Petrified Forest National Park and environs, these cores will allow the vast amount of surface paleontological and paleoenvironmental information recorded in the continental Triassic of western North America to be confidently placed in a secure context along with important events such as the giant Manicouagan impact at ~ 215:5 Ma (Ramezani et al., 2005) and long wavelength astronomical cycles pacing global environmental change and trends in atmospheric gas composition during the dawn of the dinosaurs. © Author(s) 2018.
2103.
Clay mineralogy of the first and second members of the Nenjiang Formation, Songliao Basin: Implications for paleoenvironment in the Late Cretaceous
Science China Earth Sciences,
61
(3)
327-338
2018
ISSN: 16747313
Publisher: Science in China Press
Keywords:▾
Clay alteration; Kaolinite; Lithology; Minerals; Sedimentary rocks; Volcanic rocks; Weathering, Clay mineral assemblages; Clay mineral compositions; Late cretaceous; Nenjiang Formation; Paleo-environment; Paleoenvironmental change; Paleoenvironmental reconstruction; Songliao basin, Clay minerals, clay mineral; Cretaceous; illite; lithology; mudstone; paleoenvironment; parent body; smectite; weathering, China; Songliao Basin
Abstract: ▾ The first and second members of the Nenjiang Formation (K2n1+2) in the Songliao Basin, northeast China, are an interval of dark-colored mudstone. Paleoenvironmental studies of these strata are useful for understanding the terrestrial environment under a greenhouse climate and hydrocarbon accumulation in lake basins. In this study, clay mineralogy of the K2n1+2 from four borehole or outcrop sections is investigated to understand terrestrial paleoenvironment during the depositional period in the Late Cretaceous. In the mudstone samples, smectite and illite are the predominant clay minerals, and were derived from weathering of parent rocks in a temperate, sub-humid to sub-arid climate; kaolinite and chlorite are minor clay species. The difference in the clay-mineral assemblages between the eastern and western margins of the basin was primarily controlled by provenance lithology, and the high smectite content in the western basin resulted from alteration of volcanic rocks exposed in the Greater Xing’an Range area. The increasing illite content and ratio of illite/smectite percentages in the upper part of the first member of the Nenjiang Formation indicate paleoenvironmental change. This temporal change in the clay-mineral composition was primarily caused by a regionally cooler and drier paleoclimate, consistent with previous paleoenvironmental reconstructions. © 2017, Science China Press and Springer-Verlag GmbH Germany, part of Springer Nature.
2102.
Chronological evolution of some morphological, tectonic and volcanic features in Lake Van, based on correlation of seismic and core data
Quaternary International,
48629-43
2018
ISSN: 10406182
Publisher: Elsevier Ltd
Keywords:▾
active fault; chronology; climate variation; correlation; geomorphology; Holocene; paleoclimate; seismic data; seismic reflection; seismogram; tectonic setting, Lake Van; Turkey
Abstract: ▾ The Lake Van is the largest Lake in Turkey and the fourth largest soda lake in the World. High resolution (HR) seismic data acquired during 2012 reveals sub-lacustrine terraces, delta clinoforms, channel-networks, active faults and volcanic edifices. The seismic data were correlated with the cores recovered during the 2008 coring and 2010 ICDP PaleoVan drilling campaigns, using synthetic seismograms produced from the MSCL data of the age-modelled cores, thus allowing to date seismic reflector surfaces and to discuss the temporal evolution of the some of the morphological features and structures. Sub-lacustrine channel-network systems are well developed on the shelf areas connect with the river drainage systems on land and extend to water depths of more than 100 m. These drainage systems developed during the major low-stand periods of Lake Van, the last two of which occurred during 15 ka BP and the Younger Dryas with water levels at −200 m and −70 m, respectively. High lake levels similar to today during the early Holocene were followed by lake level oscillations with some low-stands during the Late Holocene. The low stands are characterized by terraces and berms located at 15 m below lake surface (mbls), 25 mbls, 35 mbls and 60 mbls, 70 mbls and 105 mbls. They were most likely related to the rapid climate change (RCC) events such as the 4.2 ka aridity event, Dark Age Cold Period, Medieval Warm Period and Little Ice. The volcanic features are located along the Southern Boundary Fault (SBF). A significant NW-SE trending active fault in the eastern shelf left-laterally offsets a channel by about 500 m and has a small reverse component in the HR seismic profiles. This fault is considered to be the source of Mw = 5.7 Edremit Earthquake of 9 November 2011. NW-SE trending normal faults with a right-lateral strike slip component north of the Northern Basin provides extension in the area. Normal faults are also dominant in the Erciş Strait. Using ages of reflector surfaces we estimate a vertical slip rate of 0.40 mm/yr to ∼0.5 mm/yr on the normal faults in the shelf areas over the last 2–3 ka. © 2017 Elsevier Ltd and INQUA
2101.
Characteristics of top boundary of Shahezi Formation in Xujiaweizi fault depression, northern Songliao Basin: Illustrated by continental scientific drilling borehole SK2
Global Geology,
37
(3)
838-849
2018
2100.
Changing flood frequencies under opposing late Pleistocene eastern Mediterranean climates
Scientific Reports,
8
(1)
2018
ISSN: 20452322
Publisher: Nature Publishing Group
Keywords:▾
article; budget; climate change; flooding; human; hurricane; latitude; precipitation; sediment; time series analysis; Upper Pleistocene; watershed; Dead Sea
Abstract: ▾ Floods comprise a dominant hydroclimatic phenomenon in aridlands with significant implications for humans, infrastructure, and landscape evolution worldwide. The study of short-term hydroclimatic variability, such as floods, and its forecasting for episodes of changing climate therefore poses a dominant challenge for the scientific community, and predominantly relies on modeling. Testing the capabilities of climate models to properly describe past and forecast future short-term hydroclimatic phenomena such as floods requires verification against suitable geological archives. However, determining flood frequency during changing climate is rarely achieved, because modern and paleoflood records, especially in arid regions, are often too short or discontinuous. Thus, coeval independent climate reconstructions and paleoflood records are required to further understand the impact of climate change on flood generation. Dead Sea lake levels reflect the mean centennial-millennial hydrological budget in the eastern Mediterranean. In contrast, floods in the large watersheds draining directly into the Dead Sea, are linked to short-term synoptic circulation patterns reflecting hydroclimatic variability. These two very different records are combined in this study to resolve flood frequency during opposing mean climates. Two 700-year-long, seasonally-resolved flood time series constructed from late Pleistocene Dead Sea varved sediments, coeval with significant Dead Sea lake level variations are reported. These series demonstrate that episodes of rising lake levels are characterized by higher frequency of floods, shorter intervals between years of multiple floods, and asignificantly larger number of years that experienced multiple floods. In addition, floods cluster into intervals of intense flooding, characterized by 75% and 20% increased frequency above their respective background frequencies during rising and falling lake-levels, respectively. Mean centennial precipitation in the eastern Mediterranean is therefore coupled with drastic changes in flood frequencies. These drastic changes in flood frequencies are linked to changes in the track, depth, and frequency of mid-latitude eastern Mediterranean cyclones, determining mean climatology resulting in wetter and drier regional climatic episodes. © 2018 The Author(s).
2099.
Carbon dioxide generation and drawdown during active orogenesis of siliciclastic rocks in the Southern Alps, New Zealand
Earth and Planetary Science Letters,
481305-315
2018
ISSN: 0012821X
Publisher: Elsevier B.V.
Keywords:▾
Atmospheric chemistry; Budget control; Calcite; Carbonation; Dissolution; Geochemistry; Graphite; Hot springs; Isotopes; Landforms; Metamorphic rocks; Weathering, Carbon cycles; Carbon isotopes; Chemical weathering; metamorphism; Mountain building, Carbon dioxide, carbon budget; carbon cycle; carbon dioxide; carbon isotope; chemical weathering; host rock; metamorphism; orogeny; siliciclastic deposit; thermal spring; vein (geology), New Zealand; South Island; Southern Alps
Abstract: ▾ Collisional mountain building influences the global carbon cycle through release of CO2 liberated by metamorphic reactions and promoting mechanical erosion that in turn increases chemical weathering and drawdown of atmospheric CO2. The Southern Alps is a carbonate-poor, siliciclastic mountain belt associated with the active Australian Pacific plate boundary. On-going, rapid tectonic uplift, metamorphism and hydrothermal activity are mobilising carbon. Here we use carbon isotope measurements of hot spring fluids and gases, metamorphic host rocks, and carbonate veins to establish a metamorphic carbon budget. We identify three major sources for CO2 within the Southern Alps: (1) the oxidation of graphite; (2) consumption of calcite by metamorphic reactions at the greenschist–amphibolite facies boundary, and (3) the dissolution of groundmass and vein-hosted calcite. There is only a minor component of mantle CO2 arising on the Alpine Fault. Hot springs have molar HCO3 −/Ca2+ ∼9, which is substantially higher than produced by the dissolution of calcite indicating that deeper metamorphic processes must dominate. The total CO2 flux to the near surface environment in the high uplift region of the Southern Alps is estimated to be ∼6.4 × 108 mol/yr. Approximately 87% of this CO2 is sourced from coupled graphite oxidation (25%) and disseminated calcite decarbonation (62%) reactions during prograde metamorphism. Dissolution of calcite and mantle-derived CO2 contribute ∼10% and ∼3% respectively. In carbonate-rich orogens CO2 production is dominated by metamorphic decarbonation of limestones. The CO2 flux to the atmosphere from degassing of hot springs in the Southern Alps is 1.9 to 3.2 × 108 mol/yr, which is 30–50% of the flux to the near surface environment. By contrast, the drawdown of CO2 through surficial chemical weathering ranges between 2.7 and 20 × 109 mol/yr, at least an order of magnitude greater than the CO2 flux to the atmosphere from this orogenic belt. Thus, siliciclastic mountain belts like the Southern Alps are net sinks for atmospheric CO2, in contrast to orogens involving abundant carbonate rocks, such as the Himalaya, that are net CO2 sources. © 2017 The Author(s)
2098.
Depositional processes of impactites from the YAX-1 drill core in the Chicxulub impact structure inferred from vertical profiles of PDF orientations and grain size distributions of shocked quartz
Meteoritics and Planetary Science,
53
(7)
1323-1340
2018
Abstract: ▾ Core samples from the Chicxulub impact structure provide insights into the formation processes of a shallow-marine-target, complex crater. Although previous studies investigated the impactites (generally suevitic and polymict breccias) of the Yaxcopoil-1 (YAX-1) drill core in the Chicxulub impact structure, the interpretation of its deposition remains controversial. Here, we analyze planar deformation features (PDFs), grain size, and abundance of shocked quartz throughout the YAX-1 impactite sequence (794–895 m in depth). PDF orientations of most quartz grains in YAX-1 impactites show a distribution of both low angles ({10 (Formula presented.) 4}, {10 (Formula presented.) 3}, {10 (Formula presented.) 2}) and high angles (orientations higher than 55° to c-axis), while the lower part of the impactite sequence contains quartz showing only PDF orientations of low angles. High-abundance, coarse-grained shocked quartz is found from the lower to middle parts of the impactites, whereas it abruptly changes to low-abundance, fine-grained shocked quartz within the upper part. In the uppermost part of the impactites, repeated oscillations in contents of these two components are observed. PDF orientation pattern suggests most of the shocked quartz grains experienced a range of shock pressure, except two samples in the lower part of impactites, which experienced only a high level of shock. We suggest that the base and lower part of the impactite sequence were formed by ejecta curtain and melt surge deposits, respectively. Our results are also consistent with the interpretation that the middle part of the impactite sequence is fallback ejecta from the impact plume. Additionally, we support the contention that massive seawater resurges into the crater occurred during the deposition of the upper and uppermost part of the impactites. © The Meteoritical Society, 2018.
2097.
Asteroids and associated mineral systems: By Franco Pirajno
Modern Approaches in Solid Earth Sciences,
14173-205
2018
Abstract: ▾ In this chapter we discuss hydrothermal and metasomatic processes that have taken place in impact structures, subsequent to the collapse of the transient cavity and the cooling of the melt sheet and melt rocks. Most of what follows is drawn from Pirajno et al. (Aust J Earth Sci 50:775–796, 2003), Pirajno (Aust J Earth Sci 52:587–620, 2005) and Pirajno and Van Kranendonk (Aust J Earth Sci 52:329–352, 2005), particularly for the Australian examples. The flow of hot aqueous solutions commonly results in the formation of mineral deposits. Therefore, knowledge of post-impact hydrothermal activity is important because it may have resulted in economic mineral deposits. The world-class and widely known Sudbury mineral deposits (Ni, Cu, PGE, Pb, Zn, Au) are perhaps the best and most celebrated expression of mineralization directly related to a meteorite impact (Lightfoot, Nickel sulfide ores and impact melts – origin of the Sudbury Igneous Complex. Elsevier, Amsterdam, 662pp, 2016). Several lines of evidence suggest that the giant gold deposits of the Witwatersrand in South Africa may have been reworked or even enhanced by the effects of the large Vredefort impact structure. These cases will be examined briefly in the sections that follow. Hydrothermal circulation systems associated with impact events have been reported from the Ries (Germany), Puchezh-Katunki (Russia), Jämtland (Sweden), Roter Kamm (Namibia), Manson (USA), the above-mentioned Vredefort, Kärdla (Estonia), Sudbury and Haughton (Canada) structures (Newsom et al., J Geophys Res 91:E239–E251, 1986; Koeberl et al., Geoch Cosmo Acta 53:2113–2118, 1989; Naumov, Meteoritics 28:408–409, 1993; Sturkel et al., Eur J Miner 10: 589–609, 1998; Ames et al., Geology 26: 447–450, 1998; McCarville and Crossey, Geol Soc Am Sp Pap 302:347–379, 1996); Grieve and Thierriault, Annu Rev Earth Planet Sci 28: 305–338, 2000; Osinski et al., Meteor Planet Sci 36:731–745, 2001; Molnár et al., Econ Geol 96:1645–1670, 2001; Puura et al., Impact-induced replacement of plagioclase by K-feldspar in granitoids and amphibolites at the Kärdla crater, Estonia. In: Gilmour I, Koeberl C (eds) Impacts and the early earth. Springer-Verlag, Berlin, pp 417–445, 2000 and Geochemistry of K-enriched impactites, based on drillings into the Kärdla Crater, Estonia. Geol Soc Am Abs with Programs, Denver, Oct. 2002, p 341, 2002). Recently, aspects of hydrothermal alteration in the Chicxulub impact structure have been published in Meteoritic and Space Science (Lüders and Rickers, Meteor Planet Sci 39:1187–1198, 2004; Zürcher and Kring, Meteor Planet Sci 39:1199–1222, 2004; Goto et al., Meteor Planet Sci 39:1233–1247, 2004). © 2018, Springer International Publishing AG.
2096.
Archie's Saturation Exponent for Natural Gas Hydrate in Coarse-Grained Reservoirs
Journal of Geophysical Research: Solid Earth,
123
(3)
2069-2089
2018
ISSN: 21699313
Publisher: Blackwell Publishing Ltd
Keywords:▾
carbon cycle; electrical resistivity; gas hydrate; hydrocarbon reservoir; marine environment; natural gas; permafrost; saturation; wave velocity, Atlantic Ocean; Gulf of Mexico
Abstract: ▾ Accurately quantifying the amount of naturally occurring gas hydrate in marine and permafrost environments is important for assessing its resource potential and understanding the role of gas hydrate in the global carbon cycle. Electrical resistivity well logs are often used to calculate gas hydrate saturations, Sh, using Archie's equation. Archie's equation, in turn, relies on an empirical saturation parameter, n. Though n = 1.9 has been measured for ice-bearing sands and is widely used within the hydrate community, it is highly questionable if this n value is appropriate for hydrate-bearing sands. In this work, we calibrate n for hydrate-bearing sands from the Canadian permafrost gas hydrate research well, Mallik 5L-38, by establishing an independent downhole Sh profile based on compressional-wave velocity log data. Using the independently determined Sh profile and colocated electrical resistivity and bulk density logs, Archie's saturation equation is solved for n, and uncertainty is tracked throughout the iterative process. In addition to the Mallik 5L-38 well, we also apply this method to two marine, coarse-grained reservoirs from the northern Gulf of Mexico Gas Hydrate Joint Industry Project: Walker Ridge 313-H and Green Canyon 955-H. All locations yield similar results, each suggesting n ≈ 2.5 ± 0.5. Thus, for the coarse-grained hydrate bearing (Sh > 0.4) of greatest interest as potential energy resources, we suggest that n = 2.5 ± 0.5 should be applied in Archie's equation for either marine or permafrost gas hydrate settings if independent estimates of n are not available. ©2018. American Geophysical Union. All Rights Reserved.
2095.
Analysis of a fragmentary diatom record from Lake Van (Turkey) reveals substantial lake-level variability during previous interglacials MIS7 and MIS5e
Journal of Paleolimnology,
59
(1)
119-133
2018
ISSN: 09212728
Publisher: Springer Netherlands
Keywords:▾
biostratigraphy; chemical environmental conditions; deposition; depositional environment; diatom; dissolution; fossil record; Holocene; interglacial; lacustrine deposit; lake ecosystem; lake level; marine isotope stage; paleohydrology; paleolimnology; project assessment; salinity; sedimentary sequence; water depth, Anatolia; Lake Van; Turkey, Bacillariophyta
Abstract: ▾ Ancient lake sediments provide opportunities to reconstruct aquatic ecosystems during previous interglacials. In the summer of 2010, the ICDP project PALEOVAN drilled a complete succession of the lacustrine sedimentary sequence deposited during the last ~600,000 years in Lake Van, eastern Anatolia (Turkey). Previous palaeolimnological analysis of the Lake Van sediment record has shown diatoms to be absent over most of the sequence apart from a short interval during the Holocene. Here, we demonstrate the preservation of additional fragmentary diatom records during Marine Isotope Stage (MIS) 7 (243,000–191,000 years ago; Lisiecki and Raymo in Paleoceanography 20:PA1003, 2005; Jouzel et al. in Science 317:793–796, 2007) and MIS5e (130,000–116,000 years ago; Lisiecki and Raymo 2005; Jouzel et al. 2007), each spanning no more than a few thousand years. Although brief, the presence of contrasting diatom assemblages between these two interglacials provide a snapshot of varying water depth and, by inference, climate. Analysis of MIS7e samples suggests that lake water levels were low after a period when the lake was open (i.e., high lake levels with the presence of an outflow present), resulting in higher salinities and possibly less stable bottom waters, which switched between anoxic and oxic states more frequently. By contrast, the diatom assemblages during MIS5e are characteristic of fresh, relatively nutrient rich waters. This suggests that lake levels were high, that the lake was hydrologically open with an outlet, and that the bottom waters were anoxic for long periods of time. Furthermore, our palaeoconductivity estimates and modelling of the past lake volumes with respect to its salt content support the presence of an outflow. © 2017, The Author(s).