All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
2794.
The Chicxulub impact structure reveals the first in-situ Jurassic magmatic intrusions of the Yucatán Peninsula, Mexico
Lithos,
436-437
2023
Abstract: ▾ Impact events that create complex craters excavate mid- to lower-crustal rocks, offering a unique perspective on the interior composition and internal dynamics of planetary bodies. On the Yucatán Peninsula, Mexico, the surface geology mainly consists of ∼3 km thick sedimentary rocks, with a lack of exposure of crystalline basement in many areas. Consequently, current understanding of the Yucatán subsurface is largely based on impact ejecta and drill cores recovered from the 180–200-km-diameter Chicxulub impact structure. In this study, we present the first apatite and titanite U–Pb ages for pre-impact dacitic, doleritic, and felsitic magmatic dikes preserved in Chicxulub's peak ring sampled during the 2016 IODP-ICDP Expedition 364. Dating yielded two age groups, with Carboniferous dacites (328–318 Ma) and a felsite (330± 9 Ma) overlapping in age with most of the granitoid basement sampled in the Expedition 364 drill core, as well as Jurassic dolerites (169–159 Ma) and a felsite (158 ± 19 Ma) that represent the first in situ sampling of Jurassic-age magmatic intrusions for the Yucatán Peninsula. Further investigation of the Nd, Sr, and Hf isotopic compositions of these pre-impact lithologies and impact melt rocks from the peak ring structure suggest that dolerites generally contributed up to ∼10 vol% of the Chicxulub impact melt rock sampled in the peak ring. This percentage implies that the dolerites comprised a large part of the Yucatán subsurface by volume, representing a hitherto unsampled pervasive Jurassic magmatic phase. We interpret this magmatic phase to be related to the opening of the Gulf of Mexico, representing the first physical sampling of lithologies associated with the southern extension of the opening of the Gulf of Mexico and likely constraining its onset to the Late Middle Jurassic. © 2022 Elsevier B.V.
2793.
The Brécy depocenter as part of a new northern Massif Central Carboniferous–Permian Basin (France)
Comptes Rendus - Geoscience,
355163 – 190
2023
2792.
Terrestrial dominance of organic carbon in an Early Cretaceous syn-rift lake and its correlation with depositional sequences and paleoclimate
Sedimentary Geology,
455
2023
Keywords:▾
China; Songliao Basin; Alumina; Aluminum oxide; Deposition; Kerogen; Lakes; Oil shale; Stratigraphy; Weathering; Carbon concentrations; Carbon source; Chemical weathering; Littorals; Lower Cretaceous; Mudstone; Organic carbon burial; Paleoclimates; Rift basin; Syn-rift; chemical weathering; climate variation; correlation; Cretaceous; depositional sequence; lacustrine deposit; lake evolution; mudstone; organic carbon; paleoclimate; sequence stratigraphy; Organic carbon
Abstract: ▾ Organic carbon (OC) burial in lakes has been identified as an efficient sink in the global carbon cycle. Abundant input of terrestrial-derived OC leads to high variability in OC origin and type, but its role in determining organic-rich sediments has been overlooked in prior studies. Here, we investigated the OC source and concentration of the Lower Cretaceous (Middle Aptian to Lower Albian) Shahezi Formation (Songliao Basin, NE Asia) to reveal the burial of terrestrial OC in relation to syn-rift lake evolution and paleoclimate change. The sequence stratigraphic framework of fan-deltaic and lacustrine successions was established by identifying depositional facies and sequence boundaries. The lacustrine-dominated interval was further subdivided into four facies associations (i.e., lake shore to littoral siltstones, shallow-littoral mudstones, sublittoral, and profundal) and a few cyclic, parasequence-order packages, using 90 m of continuous cores and high sampling frequency of RoqSCAN SEM-EDS. Multiple independent proxies (macerals identified using correlative light and electron microscopy, pyrolysis indices, Ro, TOC/TN, and δ13Corg) suggest that the organic fraction of the highly mature mudstones was predominantly contributed by terrestrial-derived OC (gas-prone type III/IV kerogen). A direct correlation between depositional facies, chemical weathering proxies (CIA, CIAcorr, and Ln(Al2O3/Na2O)), and OC burial (TOC and HI) has been established. A steep syn-rift slope, a warm–humid climate, abundant vegetation, and the subaqueous transport of OC-bearing sediments (e.g., massive mud-rich conglomerates and sand- to pebble-bearing mudstones), may have jointly promoted the high input of terrestrial OC. A comparison between two Lower Cretaceous terrestrial records from high and low paleolatitudes suggests that the shift from the syn-rift to post-rift phase was accompanied by an increase in TOC concentration and a change toward Type I kerogen of aquatic origin. The tectonically-controlled evolution of rift basins might be an important forcing function for the change of OC sources and concentrations, which is responsible for long-term OC burial in hinterland environments. © 2023
2791.
On the occurrence of rare nannoliths (calcareous nannofossils) in the Early Jurassic and their implications for the end-Triassic mass extinction
Papers in Palaeontology,
9
(2)
2023
2790.
Pervasive carbonation of peridotite to listvenite (Semail Ophiolite, Sultanate of Oman): clues from iron partitioning and chemical zoning
European Journal of Mineralogy,
35
(2)
171 – 187
2023
Keywords:▾
Oman; Semail Ophiolite; Iron oxides; Magnesite; Quartz; Serpentine; Textures; Zoning; Chemical zoning; Convergent plate boundaries; Last stage; Mantle rocks; matrix; Mid-ocean-ridge; Quartz rocks; Reaction zones; Serpentinized peridotites; Sultanate of Oman; carbonate; iron; manganese; metasomatism; mid-ocean ridge; peridotite; quartz vein; ultramafic rock; Carbonation
Abstract: ▾ Earth's long-term cycling of carbon is regulated from mid-ocean ridges to convergent plate boundaries by mass transfers involving mantle rocks. Here we examine the conversion of peridotite to listvenite (magnesite + quartz rock) during CO2 metasomatism along the basal thrust of the Semail Ophiolite (Fanja, Sultanate of Oman). At the outcrop scale, this transformation defines reaction zones, from serpentinized peridotites to carbonated serpentinites and listvenites. Based on a detailed petrological and chemical study, we show that carbonation progressed through three main stages involving the development of replacive textures ascribed to early stages, whilst carbonate (± quartz) veining becomes predominant in the last stage. The pervasive replacement of serpentine by magnesite is characterized by the formation of spheroids, among which two types are identified based on the composition of their core regions: Fe-core and Mg-core spheroids. Fe zoning is a type feature of matrix and vein magnesite formed during the onset carbonation (Stage 1). While Fe-rich magnesite is predicted to form at low fluid XCO2 from a poorly to moderately oxidized protolith, our study evidences that the local non-redox destabilization of Fe oxides into Fe-rich magnesite is essential to the development of Fe-core spheroids. The formation of Fe-core spheroids is followed by the pervasive (over-)growth of Mg-rich spheroids and aggregates (Stage 2) at near-equilibrium conditions in response to increasing fluid XCO2. Furthermore, the compositions of carbonates indicate that most siderophile transition elements released by the dissolution of primary minerals are locally trapped in carbonate and oxides during matrix carbonation, while elements with a chalcophile affinity are the most likely to be leached out of reaction zones. © 2023 Thierry Decrausaz et al.
2789.
Multiple S-isotopic evidence for seawater incursions during the deposition of the upper Cretaceous source rocks in the Songliao Basin, northeastern China
Chemical Geology,
642
2023
2788.
Climate-controlled sensitivity of lake sediments to record earthquake-related mass wasting in tropical Lake Towuti during the past 40 kyr
Quaternary Science Reviews,
305
2023
ISSN: 02773791
Publisher: Elsevier Ltd
Keywords:▾
Catchments; Earth system models; Earthquakes; Fault slips; Sediments; Stratigraphy; Strike-slip faults; Tropics; Indonesia; Lake level changes; Lake sediments; Late Pleistocene; Mass transport deposit; Mass wasting; Paleoclimates; Paleoseismology; Seismic stratigraphy; Sulawesi/indonesia; Lakes
Abstract: ▾ Located at the triple junction of the Pacific, Eurasian and Sunda plates, the Island of Sulawesi in Indonesia is one of the most tectonically active places on Earth. This is highlighted by the recurrence of devastating earthquakes such as the 2018 Mw 7.5 earthquake that damaged the city of Palu and caused several thousand fatalities in central Sulawesi. The majority of large-magnitude earthquakes on Sulawesi are related to stress release along major strike-slip faults such as the Palu-Koro Fault and its southern extensions, the Matano and Lawanopo Faults. To date, information on the frequency and magnitude of past major events on these faults is limited to instrumental records and historical sources restricted to the last century, whereas information from natural archives is completely lacking. Lake-sediment records can fill this gap, but a detailed assessment of the various factors that influence the sensitivity of sediment successions to past earthquakes is required to evaluate their suitability. Lake Towuti, situated in Eastern Sulawesi, is known for its paleoclimate record and also promises to be a key site to generate a paleoseismology record for Sulawesi. The lake lies close to the highly active Matano and Lawanopo strike-slip faults and thereby is an ideal archive for past earthquakes that have occurred in the surrounding area. Here we combine high-resolution chirp seismic data with lithostratigraphic and petrophysical data of sediment piston cores to assess the recurrence of seismically generated mass-transport and turbidite deposits. Three major seismic-stratigraphic units are distinguished in the upper ∼10 m of the sediment succession and linked to differences in the frequency of mass-wasting during the past 60 kyrs. The evidence of a more turbidite-prone period between 12 and 40 ka is roughly coincident with a dry phase and associated lake-level lowstand during the last glacial period at Lake Towuti. Hence, we suggest that climate strongly influences the sensitivity of slopes to fail during seismic shaking in this tropical setting as a consequence of lowstand-forced sediment redeposition from the shelves onto the slopes and into the basins. As climate significantly impacts the sensitivity of the lacustrine sediments to record earthquake-related mass wasting deposits, we suggest that the frequency of mass-transport deposits can additionally be employed as a quantitative indicator for past changes in hydroclimate in these tropical settings. © 2023 The Authors
2787.
Drilling into a deep buried valley (ICDP DOVE): a 252\,m long sediment
succession from a glacial overdeepening in northwestern Switzerland
Scientific Drilling,
3227-42
2023
2786.
Development of the Chinese Continental Scientific Deep Drilling: Perspectives and Suggestions; [中国大陆科学深钻发展的若干思考与建议]
Geoscience,
37
(1)
1 – 14
2023
2785.
Development of Songliao Basin by Palaeo-Pacific slab rollback: Evidence from Early Cretaceous rhyolites in SK2 Borehole, NE China
Geological Journal,
58
(4)
1342 – 1365
2023
ISSN: 00721050
Publisher: John Wiley and Sons Ltd
DOI:10.1002/gj.4662
Keywords:▾
China; Songliao Basin; borehole; Cretaceous; geodynamics; hafnium; isotopic composition; neodymium isotope; petrogenesis; rhyolite; strontium isotope; uranium-lead dating; volcanic rock
Abstract: ▾ As the largest petroliferous basin in northeast (NE) China, Songliao Basin preserves continuous Cretaceous sedimentary-volcanic records, providing an excellent opportunity to recover the palaeo-environment. The Yingcheng Formation in the Songliao Basin contains ample gas reservoirs that attract widespread attention. Whereas the timing, petrogenesis and geodynamic mechanism of the volcanic rocks in the Yingcheng Formation are still controversial, which largely constrain our understanding of the formation and evolution of the Songliao Basin. Here, we present an integrated investigation of zircon U–Pb ages and Hf isotope, as well as whole-rock elements and Sr-Nd isotopes data for a suite of rhyolites of Yingcheng Formation from the SK2 Borehole of NE China. Zircon U–Pb age dating results of nine samples have yielded a concentrated age of ~110 Ma. These Yingcheng rhyolites are characterized by high SiO2 (66–78 wt%) and alkali (Na2O + K2O = 7.80–11.70 wt%) content, high 10000*Ga/Al (1.26–3.82, mostly >2.6) and FeOT/(FeOT + MgO) ratios (0.81–0.95), which show geochemical affinities with A-type rhyolites. They have relatively low Y/Nb (0.69–1.78, average 1.19) and Rb/Nb (1.58–6.52, average 4.34) ratios, suggesting that the Yingcheng volcanic samples belong to A1-type rhyolites which formed in an intraplate environment. These Yingcheng rhyolites show depleted Nd-Hf isotopic compositions (εNd(t) = 2.43–4.87 and zircon εHf(t) = 4.22–9.88) comparable with the Early Cretaceous A-type and I-type rhyolites in the Songliao Basin, suggesting that they were originated from a juvenile continental crust. They were most likely derived from the partial melting of anhydrous lower crust instead of differentiation of mantle-derived or mixing with alkaline basaltic magma, due to their low Mg# and absence of the coeval mafic rocks. Combined with the previous studies, A-type rhyolites in the Yingcheng Formation erupted lasting at least 10 Myr and were widely distributed in the rifts of the Songliao Basin. We propose that the Yingcheng rhyolites were most likely generated from the rollback of the Palaeo-Pacific Plate in the Early Cretaceous, thus highlighting the significance of the subduction of the Palaeo-Pacific Plate during the secular evolution of the Songliao Basin. © 2022 John Wiley & Sons Ltd.
2784.
Deciphering the tectonometamorphic history of subducted metapelites using quartz-in-garnet and Ti-in-quartz (QuiG-TiQ) geothermobarometry—A key for understanding burial in the Scandinavian Caledonides
Journal of Metamorphic Geology,
n/a
(n/a)
2023
ISSN: 1525-1314Keywords:▾
40Ar/39Ar dating, Scandinavian Caledonides, P–T–D–t evolution, quartz-in-garnet, Ti-in-quartz thermobarometry
Abstract: ▾ The Seve Nappe Complex is a subduction-related high-grade metamorphic unit that was emplaced onto the margin of Baltica during Caledonian orogenesis. In this paper, the tectonometamorphic evolution of the Lower Seve Nappe in the Scandinavian Caledonides was characterized with the help of the continuous Collisional Orogeny in the Scandinavian Caledonides (COSC-1) drill core, using a combination of various P–T estimation techniques based on garnet–quartz mineral pairs (quartz-in-garnet and Ti-in-quartz [QuiG–TiQ]), conventional thermobarometry and thermodynamic modelling of phase equilibria. This multi-method approach yields complementary results and delivers critical data to constrain a comprehensive pressure–temperature–deformation–time (P–T–D–t) evolutionary path for the metasedimentary rocks of the Lower Seve Nappe. In the garnetiferous metasedimentary rocks, quartz inclusions in garnet preserve the P–T conditions of three distinct garnet growth stages corresponding to three metamorphic stages Ms1 to Ms3, including prograde and peak metamorphic conditions. Ms1 and Ms2 stages were constrained via quartz inclusions in garnet core and mantle. They are relatively close in the P–T space and could be considered as one single continuous prograde event occurring at epidote–amphibolite facies conditions of 460–520°C and 0.6–0.85 GPa. The growth of the garnet outermost rim defines the Ms3 stage at amphibolite facies conditions of 590–610°C and 1.13–1.18 GPa and corresponds to the peak metamorphic conditions. The microstructural analysis shows that the finite ductile strain pattern of the Lower Seve Nappe results from the superposition of four deformation phases. The initial phase D1 is defined by the S1 foliation that is still preserved as a curved inclusion trail in the garnet core. The D2 phase initiated contemporaneously with garnet core growth and the development of muscovite–biotite–plagioclase S2 foliation. Garnet outermost rim growth marks the end of the prograde path and peak metamorphic conditions. This stage is overprinted by the D3 phase and Ms4 stage associated with the development of the main regional metamorphic and mylonitic fabric S3 associated with C′-type shear bands along the retrograde path. Ms4 stage, which was constrained using traditional thermobarometric techniques, corresponds to the chemical re-equilibration of the metasedimentary minerals and occurred under amphibolite facies conditions at 570–610°C and 0.78–1.00 GPa. The D3 phase is then generally weakly to strongly overprinted by later lower grade deformation D4 phase at greenschist facies conditions (Ms5). 40Ar/39Ar ages of syn-kinematic white mica and biotite indicate that the final stage of the thrusting of the Lower Seve Nappe and thus the timing of its emplacement onto the Offerdal Nappe occurred at c. 423 Ma. Collectively, these results are consistent with previous estimates of the timing and conditions of metamorphism derived from the Lower Seve Nappe especially in west-central Jämtland. However, application of QuiG–TiQ thermobarometry demonstrated that quartz inclusions in garnet can preserve different aspects of garnet growth, which are not accessible by traditional methods especially in complex terranes, and therefore provided new significant insights into the Lower Seve prograde evolution.
2783.
Cross-Property Relationship Between Electrical Resistivity and Elastic
Wave Velocity of Crustal Rocks From the Oman Drilling Project Hole GT3A:
Implications for in Situ Geophysical Properties of Oceanic Crust
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH,
128
(6)
2023
Keywords:▾
electrical resistivity; elastic wave velocity; oceanic crust; crack;
Oman drilling Project; IODP hole 1256D
2782.
Country-wide exploration for graphite- and sulphide-rich black shales with airborne geophysics and petrophysical and geochemical studies
Journal of Geochemical Exploration,
244
2023
ISSN: 03756742
Publisher: Elsevier B.V.
Keywords:▾
Core drilling; Deposits; Electric conductivity; Geological surveys; Geophysics; Graphite; Infill drilling; Magnetic susceptibility; Oil shale; Sampling; Stratigraphy; Airborne geophysics; Black shales; Ferrimagnetics; Finland; Geophysical measurements; Greenschist; Monoclinics; Sample sets; Sulphide; Sulphide deposits; graphite; host rock; hydrocarbon exploration; hydrocarbon generation; petrography; shale; sulfide; Sulfur compounds
Abstract: ▾ Black shales host critical raw materials such as graphite and cobalt and occur in the vicinity of many types of sulphide deposits. We report the procedure for country-wide mapping of graphite- and sulphide-rich rocks and the chemical and petrophysical data of 319 samples we selected from sulphide occurrences and mines in Finland. Even though black shales are rarely outcropped in glaciated and deeply weathered terrains, they can be traced with geophysical surveys. In the Precambrian of Finland, where the metamorphic grade varies from greenschist to granulite facies, systematic airborne geophysical surveys revealed stratigraphy-related, coupled magnetic and electrically conductive patterns. Electrical conductivity was related to the graphite and sulphide contents, producing continuous and bending electromagnetic anomaly patterns. The magnetic anomalies, if present, resulted from ferrimagnetic monoclinic pyrrhotite. The petrophysical properties of black shales varied in our sample set. The densities were mainly between 2700 and 3000 kg/m3, with the mean density ~ 2800 kg/m3, where the amount of graphite had a reducing effect on density whereas sulphides increased it. The average magnetic susceptibilities were about 6000·10−6 (SI), but they showed wide variation, depending on the abundance of ferrimagnetic monoclinic pyrrhotite. The electrical conductivity of black shales appeared to be positively related to the abundance of monoclinic pyrrhotite. Conductivity variation, 1–105 1/Ωm was based on laboratory determinations of apparent resistivities. We correlated an airborne magnetic and electromagnetic survey with petrophysical and chemical data from altogether 319 drill core samples containing >1 % graphitic C and >1 % S. The samples were selected during 2009–2011 from 102 drill cores all over Finland except for the Talvivaara–Outokumpu region, which was studied during previous projects. The black-shale-hosted Talvivaara Ni–Zn–Co–Cu deposit is currently being mined. The maximum graphite concentration in the country-wide sample set was 34.3 %, and the median value was 5.7 %, a lower value than reported from the Talvivaara black-shale-hosted sulphide deposit (7.6 %). S, Co, Cu, Fe and Ni concentrations were also lower in our sample set on average than in the Talvivaara ore. However, the maximum concentration in our sample set was 397 mg/kg for Co, 0.36 % for Cu, 40.8 % for Fe and 0.28 % for Ni. The developed black shale mapping procedure can be directly applied in other parts of the world in terrains with greenschist to granulite facies regional metamorphism. Information on basic petrophysical properties, i.e., density, magnetic and electric properties, are needed to explain geophysical anomalies. If the metamorphic grade is lower than greenschist facies and there is no graphite, sulphides will increase the electromagnetic properties. If ferrimagnetic pyrrhotite exists, susceptibility increases, as well as remanence. The black shale database covering the whole of Finland is used not only in exploration and bedrock mapping, but also in regional planning and for environmental risk analyses, because sulphide-rich black shales may cause acid rock drainage when exposed to weathering and the quality of surface water and groundwater may suffer from black shale bedrock and glacial till. The scale limitations given by airborne geophysics may request detailed studies in selected sites. © 2022 The Author(s)
2781.
Continental geological evidence for Solar System chaotic behavior in the Late Cretaceous
Bulletin of the Geological Society of America,
135
(3-4)
712 – 724
2023
ISSN: 00167606
Publisher: Geological Society of America
DOI:10.1130/B36340.1
Keywords:▾
China; Songliao Basin; Binary alloys; Earth (planet); Lead alloys; Orbits; Uranium alloys; Chaotic behaviour; High resolution; Lacustrine sequence; Late cretaceous; Magnetic reversal; Milankovitch cycle; Orbital parameters; Songliao basin; System solution; U-Pb ages; age determination; chaotic dynamics; Cretaceous; Earth; Mars; reconstruction; solar cycle; solar system; stratigraphy; uranium-lead dating; Stratigraphy
Abstract: ▾ The Earth’s geologic record of Milankovitch cycles closely tracks Solar System solutions for the past 50 million years. Prior to 50 million years ago (Ma), however, the solutions lose accuracy rapidly due to chaotic behavior of the Solar System. Here we reconstruct a 10.173 million year-long record from 82.358 Ma to 92.531 Ma of Earth’s orbital parameters from a continental lacustrine sequence in the Songliao Basin, China, constrained by four in situ high-resolution radioisotopic U-Pb ages and magnetic reversal stratigraphy. Analysis of thorium and ostracode shell abundance records from the Songliao Basin reveal evidence for two chaotic secular resonance transitions in the orbital motions of Earth and Mars from 85.2 Ma to 91.55 Ma. The evidence validates similar observations in western North American marine stratigraphy. A unique phasing between the observed orbital eccentricity and obliquity modulations may explain the anoxic events that occurred in both marine and continental environments during this time. Taken together, the continental and marine stratigraphic evidence demonstrates a strong global reach of Late Cretaceous Milankovitch cycles, and provides an important constraint on Solar System chaoticity and the calculation of accurate orbital solutions prior to 50 Ma. © 2022 Geological Society of America
2780.
Constraints on the Nd-isotopic composition and nature of the last major influx of magma into the Bushveld Complex
Contributions to Mineralogy and Petrology,
178
(3)
14
2023
2779.
Boron geochemistry reveals the evolution of Dead Sea brines
Earth and Planetary Science Letters,
622
2023
Keywords:▾
Budget control; Glacial geology; Infill drilling; Isotopes; Lakes; Seawater; Authigenic; Boron cycle; Boron isotope budget; Boron isotopes; Lacustrine authigenic aragonite; Pleistocene; Pleistocene lake lisan; Pliocene; Pliocene sedom lagoon; Seawater evolution; aragonite; authigenic mineral; boron; brine; concentration (composition); geochemistry; lacustrine environment; seawater; Boron
Abstract: ▾ Well-known for their geological and natural singularity, the Dead Sea brines evolved from a marine ingression of the Mediterranean during the Pliocene. Dead Sea brines are currently almost ten times more concentrated than seawater and have a unique chemical composition with high boron isotope values (δ11Bbrine = ∼57‰). However, little is known on how these values were attained and their underlaying driving processes. Here we use boron isotopes (δ11B) combined with B/Ca and B/Li of lacustrine authigenic aragonites from the deep basin drill-core ICDP 5017-1, and Ein Gedi and Masada profiles to reconstruct past brine conditions. Comparing reconstructed δ11Bbrine from two key periods of contrasting hydro-climatic regimes we find that the brines of the late Holocene Dead Sea were enriched in 11B (δ11Bbrine = ∼60‰) relative to its glacial precursor Lake Lisan (∼57‰). With the aid of boron cycle modelling, we quantify the main boron fluxes in the basin. We show that the post-glacial δ11Bbrine enrichment is best explained by overall reduction of freshwater inflow to the lake and coeval increase in 10B sink through boron co-precipitation in evaporitic deposits and boron loss in atmospheric water vapour, consistent with the onset of warmer and drier climate in the Eastern Mediterranean during the Holocene. On geological time scales, adsorption of 10B on clastic sediments has acted as an important 10B sink and can explain the evolution of the high δ11Bbrine values. © 2023 The Author(s)
2778.
Eastward extension of the Solonker Suture beneath the central Songliao Basin, NE China: Evidence from a deep seismic reflection profile
Gondwana Research,
119164 – 171
2023
2777.
Bayesian seismic travel-time cross-hole tomography in vertically transversely isotropic media
Journal of Applied Geophysics,
209
2023
ISSN: 09269851
Publisher: Elsevier B.V.
Keywords:▾
Gas hydrates; Markov processes; Monte Carlo methods; Recovery; Seismology; Uncertainty analysis, Algorithm approaches; Bayesian; Cross hole; Finite difference; Markov chain monte carlo samplings; Monte carlo; Monte carlo sampling algorithms; Seismic; Transversal isotropy; Transversely isotropic medias, Anisotropy, algorithm; Bayesian analysis; data inversion; data set; finite difference method; gas hydrate; Markov chain; model test; Monte Carlo analysis; seismic tomography; seismic velocity; seismic wave; transverse isotropy; travel time
Abstract: ▾ We apply a transdimensional, hierarchical Markov chain Monte Carlo sampling algorithm (McMC) for 2-D cross-hole travel-time tomography in transversely isotropic media with vertical symmetry axis. The McMC approach has several advantages compared to classical inversion approaches: It is a global search, the high number of tested models allows the statistical analysis including the calculation of a reference model as well as uncertainty estimation, no initial models or regularization parameters are needed, the amount of data noise is automatically determined, and the model parametrization is data dependent and self-adjusting. For the forward solution a FD Fast Marching method utilizing second-order Godunov schemes is used. The performance of the approach is first tested on synthetic datasets to evaluate the potential and possible limitation to recover anisotropic models. We have shown that the recovery of models described by 2 anisotropic parameters (Thomsen parameters) and the vertical velocity is possible for observation scenarios with good distribution of sources and receivers. For more realistic observational geometries (i.e. cross-hole experiments), the recovery of the 3 parameters is limited, but still possible for example for the elliptical anisotropic case (ε = δ) or regarding the horizontal velocity. Finally we applied the McMC approach to a well-studied real cross-hole data set from the MALLIK 2002 research program and compared the results with previous conventional inversions. © 2022
2776.
Authigenic minerals reflect microbial control on pore waters in a
ferruginous analogue
GEOCHEMICAL PERSPECTIVES LETTERS,
2820-26
2023
2775.
Authigenic mineralization in Surtsey basaltic tuff deposits at 50 years
after eruption
SCIENTIFIC REPORTS,
13
(1)
2023
2774.
Application of improved support vector machine in geochemical lithology identification
Earth Science Informatics,
16
(1)
205 – 220
2023
ISSN: 18650473
Publisher: Springer Science and Business Media Deutschland GmbH
Keywords:▾
China; Songliao Basin; geochemical method; identification method; lithology; logging (geophysics); machine learning; support vector machine; weight
Abstract: ▾ Lithology identification is an important task in oil and gas exploration. In recent years, machine learning methods have become a powerful tool for intelligent lithology identification. To address the redundancy of conventional logging data and unbalanced distribution among formation lithology classes due to the complexity of depositional environment and inhomogeneity of subsurface space, this paper investigates the affiliation-weighted one-to-one support vector machine (WOVOSVM) lithology identification method based on geochemical logging data. This method uses geochemical logging data, which can directly reflect the formation lithology information, as input, and achieves intelligent and accurate lithology classification under the calculation of WOVOSVM. In this study, Shahezi Formation of Songke 2 Well in Songliao Basin, China is taken as the experimental object, and two data sets with different distribution characteristics are selected as the input. Use WOVOSVM, Adaboost, random forest (RF) and traditional support vector machine (SVM) to identify lithology, and compare and analyze the results. The results are as follows: (1) Accuracy metrics of most of the four classification models were above 60%, indicating the geochemical logging data can effectively reflect the formation lithology information, which is a reliable indicator for the intelligent identification of logging lithology. (2) When the data set has a strong imbalance, the lithology recognition performance of WOVOSVM is better than other methods, the average value of accuracy metrics is more than 72%, F1 value is 8.77% to 14.56% higher than other models, especially in the small sample lithology category recognition, 70% of the samples are correctly classified. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
2773.
A one-million-year isotope record from siderites formed in modern ferruginous sediments
Bulletin of the Geological Society of America,
135
(1-2)
504 – 522
2023
ISSN: 00167606
Publisher: Geological Society of America
DOI:10.1130/B36211.1
Keywords:▾
Greater Sunda Islands; Lake Towuti; Malili Lakes; South Sulawesi; Sulawesi; Sunda Isles; Biogeochemistry; Deposition; Geology; Iron; Iron ores; Isotopes; Organic compounds; Oxygen; Sediments; Water; Biogenics; Bottom water; Diagenetics; Geological timescales; Iron isotopes; Isotope record; Isotope signatures; Pore waters; Water columns; δ13C; carbon isotope; depositional environment; iron; isotopic composition; oxygen; oxygenation; Precambrian; sediment chemistry; sediment-water interface; siderite; Lakes
Abstract: ▾ Ancient iron formations hold important records of environmental conditions during the Precambrian eons. Reconstructions of past oceanic systems require investigation of modern ferruginous analogs to disentangle water column and diagenetic signals recorded in iron-bearing minerals. We analyzed oxygen, iron, and carbon isotopes in siderite, a ferrous carbonate phase commonly used as an environmental proxy, from a 100-m-long record spanning a 1 Ma depositional history in ferruginous Lake Towuti, Indonesia. Combining bulk sediment and pore water geochemistry, we traced processes controlling siderite isotope signatures. We show that siderite oxygen isotope compositions (δ18O) reflect in-lake hydrological and depositional conditions. Low iron isotope values (δ56Fe) record water column oxygenation events over geological timescales, with minor diagenetic partitioning of Fe isotopes by microbial iron reduction after deposition. The carbon isotope compositions (δ13C) reflect the incorporation of biogenic HCO3 –, which is consistent with sediment organic matter remineralization lasting over ca. 200 ka after burial. Positive δ13C excursions indicate an increased production of biogenic methane that escaped the sediment during low lake levels. Diffusion across the sediment–water interface during initial formation of siderites tends to align the isotope signatures of bottom waters to those of pore waters. As microbial reduction of ferric iron and oxidation of organic matter proceed and saturate pore water conditions with respect to siderite, overgrowth on nuclei partially mutes the environmental signal inherited from past bottom waters over ca. 1 Ma. Because high depositional fluxes of ferric iron and organic matter in early oceans would have promoted similar microbial processes in ferruginous deposits prior to lithification, the environmental record contained in siderite grains can successively integrate depositional and early diagenetic signals over short geological timescales. © 2022 Geological Society of America
2772.
A neotropical perspective on the uniqueness of the Holocene among interglacials
Nature Communications,
14
(1)
2023
2771.
3-D imaging of the Balmuccia peridotite body (Ivrea-Verbano zone,
NW-Italy) using controlled source seismic data
GEOPHYSICAL JOURNAL INTERNATIONAL,
234
(3)
1985-1998
2023
Keywords:▾
Europe; Controlled source seismology; Seismic tomography; Continental
tectonics: compressional; Crustal structure
2770.
Millennial hydrological variability in the continental northern Neotropics during Marine Isotope Stages (MISs) 3-2 (59-15 cal ka BP) inferred from sediments of Lake Petén Itzá, Guatemala
Climate of the Past,
19
(7)
1409 – 1434
2023
Keywords:▾
Atlantic Ocean; Atlantic Ocean (Tropical); Guatemala [Central America]; Lake Peten Itza; Pacific Ocean; Pacific Ocean (Equatorial); Peten; Atlantic Multidecadal Oscillation; atmospheric convection; climate conditions; climate variation; hydrological change; intertropical convergence zone; lacustrine deposit; marine isotope stage; Neotropical Region; overturn; paleoclimate; primary production; redox conditions; sediment core
Abstract: ▾ Lake Petén Itzá (Guatemala) possesses one of the longest lacustrine sediment records in the northern Neotropics, which enabled study of paleoclimate variability in the region during the last ∼400000 years. We used geochemical (Ti, Ca/(Ti+Fe) and Mn/Fe) and mineralogical (carbonates, gypsum, quartz, clay) data from sediment core PI-2 to infer past changes in runoff, lake evaporation, organic matter sources and redox conditions in the water column, caused by hydrological changes in the northern Neotropics during Marine Isotope Stages (MISs) 3-2. From 59 to 39 cal ka BP climate conditions were relatively wet, and the lake was marked by higher primary productivity and anoxic bottom waters. This wet environment was interrupted for two periods of possible low water level at 52 and 46 cal ka BP, when our data suggest higher evaporation, high terrestrial organic matter input and persistent oxic conditions. Between 39 and 23 cal ka BP, evaporation and input of terrestrial organic matter increased considerably, lake level declined, and lake bottom waters generally became oxic. These conditions reversed during the Last Glacial Maximum (23.5-18.0 cal ka BP), when runoff and lake productivity increased, and rising lake level caused bottom waters to again become anoxic. Comparison of our hydrologic proxy data with sea surface temperature anomalies between the eastern Pacific and the Caribbean suggests that changes in the intensity of the Caribbean Low-Level Jet (CLLJ) may have influenced long-term changes in runoff during MISs 3-2. Higher intensity of the CLLJ during the onset of MIS 3 and the LGM might have led to greater runoff into the lake, whereas the MIS 3-2 transition experienced a weaker CLLJ and consequently less runoff. A refined, high-resolution age-depth model for the PI-2 sediment core enabled us to identify millennial-scale Greenland interstadials (GIs) 14-2, Greenland stadials (GSs) 14-2 and Heinrich stadials (HSs) 5-1. In general, HSs and GSs were characterized by drier conditions. In contrast to GSs and HSs, GIs were characterized by greater runoff and overall wetter conditions, with the most pronounced GI peaks between 40 and 30 cal ka BP. Whereas GSs 9, 8, 7 and 6 began with abrupt increases in evaporation and ended with gradual increases in humidity, GSs 11 and 10 showed reversed patterns. The Lake Petén Itzá paleohydrology record, along with other regional paleoclimate records, led us to conclude that shifts in the position of the Intertropical Convergence Zone (ITCZ) altered moisture delivery to the lake on millennial timescales. During GSs and HSs, high evaporation from Petén Itzá (dry climate conditions) was associated with a more southerly position of the ITCZ, whereas wetter GIs prevailed during a more northerly ITCZ position. Although abrupt millennial-scale shifts in ITCZ and hydroclimate between GSs/HSs and GIs can be linked to instabilities in the Atlantic Meridional Overturning Circulation (AMOC), longer-term changes were additionally influenced by changes in atmospheric convection linked to modulations of the CLLJ in response to ΔSST between the equatorial Pacific and tropical Atlantic. © 2023 Rodrigo Martínez-Abarca et al.