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  • 1
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    (Table T1) Paleomagnetic characterization of ODP Hole 198-1213B basalts (2005)
    PANGAEA
    In:  Supplement to: Tominaga, Masako; Sager, William W; Channell, James E T (2005): Paleomagnetism of the igneous section, Hole 1213B, Shatsky Rise. In: Bralower, TJ; Premoli Silva, I; Malone, MJ (eds.) Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 198, 1-15, https://doi.org/10.2973/odp.proc.sr.198.113.2005
    Details
    Publication Date: 2024-01-09
    Description: Paleomagnetic measurements were made on 52 samples from the igneous section of Ocean Drilling Program Hole 1213B for the purpose of determining paleoinclination and polarity and giving insight about volcanic emplacement. Samples were taken at approximately even intervals from the three basaltic sills that make up the section, and all samples were demagnetized using an alternating field or thermal methods in an effort to determine the characteristic magnetization direction. Half of the samples gave inconsistent results. Furthermore, natural remanent magnetization values were strong and median destructive field values were low, implying that the basalts are prone to acquiring an overprint from the drill string. In addition, hysteresis results show low coercivities and lie in the pseudosingle-domain field of a Day plot (Mr/Ms vs. Bcr/Bc). All of these observations suggest that the samples are characterized by a low-coercivity magnetic mineral, such as titanomagnetite, that may not always preserve a stable characteristic remanence. Nevertheless, 26 samples produced consistent inclinations, giving shallow, negative values that are considered the likely characteristic direction. There is no statistical difference between mean inclinations for the three units, implying they erupted within a short time. Measurements from all reliable samples were averaged to give a paleoinclination of -9.3° with 95% confidence limits from -41.8° to 27.5°, the large uncertainty resulting from the fact that paleosecular variation is not averaged. Although the large uncertainty makes a unique assignment of polarity difficult, the interpretation that is most consistent with other Pacific paleomagnetic data is that the magnetization has a reversed polarity acquired slightly north of the equator.
    Keywords: 198-1213B; ChRM, Inclination; Demagnetization level; Demag Type; DEPTH, sediment/rock; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Hysteresis, coercive field; Hysteresis, remanent coercive field; Hysteresis, saturation magnetization; Hysteresis, saturation remanence; Joides Resolution; Leg198; Lithologic unit/sequence; MAG; Magnetic susceptibility; Magnetometer; Magnetometer, PMC N2900 alternating-gradient force; Maximum angular deviation; Method comment; North Pacific Ocean; NRM, Intensity; NRM, median destructive field of natural remanent magnetization, alternating field; Ocean Drilling Program; ODP; Sample amount, subset; Sample code/label; Sample comment; Single sample demagnetization
    Type: Dataset
    Format: text/tab-separated-values, 568 data points
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    DATA PANGAEA
  • 2
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    Drilling constraints on lithospheric accretion and evolution at Atlantis Massif, Mid-Atlantic Ridge 30°N (2011)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 116 (2011): B07103, doi:10.1029/2010JB007931.
    Description: Expeditions 304 and 305 of the Integrated Ocean Drilling Program cored and logged a 1.4 km section of the domal core of Atlantis Massif. Postdrilling research results summarized here constrain the structure and lithology of the Central Dome of this oceanic core complex. The dominantly gabbroic sequence recovered contrasts with predrilling predictions; application of the ground truth in subsequent geophysical processing has produced self-consistent models for the Central Dome. The presence of many thin interfingered petrologic units indicates that the intrusions forming the domal core were emplaced over a minimum of 100–220 kyr, and not as a single magma pulse. Isotopic and mineralogical alteration is intense in the upper 100 m but decreases in intensity with depth. Below 800 m, alteration is restricted to narrow zones surrounding faults, veins, igneous contacts, and to an interval of locally intense serpentinization in olivine-rich troctolite. Hydration of the lithosphere occurred over the complete range of temperature conditions from granulite to zeolite facies, but was predominantly in the amphibolite and greenschist range. Deformation of the sequence was remarkably localized, despite paleomagnetic indications that the dome has undergone at least 45° rotation, presumably during unroofing via detachment faulting. Both the deformation pattern and the lithology contrast with what is known from seafloor studies on the adjacent Southern Ridge of the massif. There, the detachment capping the domal core deformed a 100 m thick zone and serpentinized peridotite comprises ∼70% of recovered samples. We develop a working model of the evolution of Atlantis Massif over the past 2 Myr, outlining several stages that could explain the observed similarities and differences between the Central Dome and the Southern Ridge.
    Keywords: Atlantis Massif ; Integrated Ocean Drilling Program ; Oceanic Core Complex
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
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    Nature of the Jurassic Magnetic Quiet Zone (2015)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 42 (2015): 8367–8372, doi:10.1002/2015GL065394.
    Description: The nature of the Jurassic Quiet Zone (JQZ), a region of low-amplitude oceanic magnetic anomalies, has been a long-standing debate with implications for the history and behavior of the Earth's geomagnetic field and plate tectonics. To understand the origin of the JQZ, we studied high-resolution sea surface magnetic anomalies from the Hawaiian magnetic lineations and correlated them with the Japanese magnetic lineations. The comparison shows the following: (i) excellent correlation of anomaly shapes from M29 to M42; (ii) remarkable similarity of anomaly amplitude envelope, which decreases back in time from M19 to M38, with a minimum at M41, then increases back in time from M42; and (iii) refined locations of pre-M25 lineations in the Hawaiian lineation set. Based on these correlations, our study presents evidence of regionally and possibly globally coherent pre-M29 magnetic anomalies in the JQZ and a robust extension of Hawaiian isochrons back to M42 in the Pacific crust.
    Description: National Science Foundation Grant Numbers: OCE-1029965, OCE-1233000, OCE-1029573
    Description: 2016-04-24
    Keywords: Jurassic Quiet Zone ; Magnetic anomaly ; Plate tectonics
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
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    Revised Pacific M-anomaly geomagnetic polarity timescale (2010)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Authors, 2010. This article is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 182 (2010): 203-232, doi:10.1111/j.1365-246X.2010.04619.x.
    Description: The current M-anomaly geomagnetic polarity timescale (GPTS) is mainly based on the Hawaiian magnetic lineations in the Pacific Ocean. M-anomaly GPTS studies to date have relied on a small number of magnetic profiles, a situation that is not ideal because any one profile contains an uncertain amount of geologic 'noise' that perturbs the magnetic field signal. Compiling a polarity sequence from a larger array of magnetic profiles is desirable to provide greater consistency and repeatability. We present a new compilation of the M-anomaly GPTS constructed from polarity models derived from magnetic profiles crossing the three lineation sets (Hawaiian, Japanese and Phoenix) in the western Pacific. Polarity reversal boundary locations were estimated with a combination of inverse and forward modelling of the magnetic profiles. Separate GPTS were established for each of the three Pacific lineation sets, to allow examination of variability among the different lineation sets, and these were also combined to give a composite timescale. Owing to a paucity of reliable direct dates of the M-anomalies on ocean crust, the composite model was time calibrated with only two ages; one at each end of the sequence. These two dates are 125.0 Ma for the base of M0r and 155.7 Ma for the base of M26r. Relative polarity block widths from the three lineation sets are similar, indicating a consistent Pacific-wide spreading regime. The new GPTS model shows slightly different spacings of polarity blocks, as compared with previous GPTS, with less variation in block width. It appears that the greater polarity chron irregularity in older models is mostly an artifact of modelling a small number of magnetic profiles. The greater averaging of polarity chron boundaries in our model gives a GPTS that is statistically more robust than prior GPTS models and a superior foundation for Late Jurassic–Early Cretaceous geomagnetic and chronologic studies.
    Description: This work was supported by the Jane & R. Ken Williams'45 Chair of Ocean Drilling Science and Technology.
    Keywords: Magnetic anomalies: modelling and interpretation ; Reversals: process, time scale, magnetostratigraphy ; Marine magnetics and palaeomagnetics
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 5
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    Characterization of the in situ magnetic architecture of oceanic crust (Hess Deep) using near-source vector magnetic data (2016)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Geophysical Research: Solid Earth 121 (2016): 4130–4146, doi:10.1002/2015JB012783.
    Description: Marine magnetic anomalies are a powerful tool for detecting geomagnetic polarity reversals, lithological boundaries, topographic contrasts, and alteration fronts in the oceanic lithosphere. Our aim here is to detect lithological contacts in fast-spreading lower crust and shallow mantle by characterizing magnetic anomalies and investigating their origins. We conducted a high-resolution, near-bottom, vector magnetic survey of crust exposed in the Hess Deep “tectonic window” using the remotely operated vehicle (ROV) Isis during RRS James Cook cruise JC21 in 2008. Hess Deep is located at the western tip of the propagating rift of the Cocos-Nazca plate boundary near the East Pacific Rise (EPR) (2°15′N, 101°30′W). ROV Isis collected high-resolution bathymetry and near-bottom magnetic data as well as seafloor samples to determine the in situ lithostratigraphy and internal structure of a section of EPR lower crust and mantle exposed on the steep (~20°dipping) south facing slope just north of the Hess Deep nadir. Ten magnetic profiles were collected up the slope using a three-axis fluxgate magnetometer mounted on ROV Isis. We develop and extend the vertical magnetic profile (VMP) approach of Tivey (1996) by incorporating, for the first time, a three-dimensional vector analysis, leading to what we here termed as “vector vertical magnetic profiling” approach. We calculate the source magnetization distribution, the deviation from two dimensionality, and the strike of magnetic boundaries using both the total field Fourier-transform inversion approach and a modified differential vector magnetic analysis. Overall, coherent, long-wavelength total field anomalies are present with a strong magnetization contrast between the upper and lower parts of the slope. The total field anomalies indicate a coherently magnetized source at depth. The upper part of the slope is weakly magnetized and magnetic structure follows the underlying slope morphology, including a “bench” and lobe-shaped steps, imaged by microbathymetry. The lower part of the slope is strongly magnetized, with a gradual reduction in amplitude from east to west across the slope. Surface morphology and recent drilling results indicate that the slope has been affected by mass wasting, but the observation of internally coherent magnetization distributions within the upper and lower slopes suggest that the disturbance is surficial. We attribute the spatial differences in magnetization distribution to the combination of changes in in situ lithology and depth to the source. These survey lines document the first magnetic profiles that capture the gabbro-ultramafic and possibly dike-gabbro boundaries in fast-spreading lower crust.
    Description: NERC Grant Number: NERC509023/1; IODP-USSSP; Woods Hole Oceanographic Institution Postdoctoral Scholarship
    Keywords: Marine magnetics ; Lower crust ; Upper mantle
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 6
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    Velocity structure of upper ocean crust at Ocean Drilling Program Site 1256 (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 9 (2008): Q10O13, doi:10.1029/2008GC002188.
    Description: We examine shipboard physical property measurements, wireline logs, and vertical seismic profiles (VSP) from Ocean Drilling Program/Integrated Ocean Drilling Program Hole 1256D in 15 Ma ocean crust formed at superfast spreading rates to investigate lateral and vertical variations in compressional velocity. In general, velocities from all methods agree. Porosity is inversely related to velocity in both the logging and laboratory data. We infer that microfracturing during drilling is minor in the upper 1 km of basement, probably due to connected pores and, thus, low effective stress. The closure of porosity to very low values coincides with the depth below which laboratory velocities diverge from logging velocities. We infer that porosity controls velocity in layer 2, lithostatic pressure controls the thickness of seismic layer 2, and the distribution of flow types determines seismic velocity in the upper 200 m of basement. In the sheeted dikes, changes in physical properties, mineralogy, and chemistry define clusters of dikes.
    Description: Funding for this research was provided by Joint Oceanographic Institutions (JOI) Task Order T312A26 and NSF grant OCE-0424633.
    Keywords: Upper ocean crust ; Seismic structure ; Integrated Ocean Drilling Program ; D/V JOIDES Resolution ; Expedition 309/312 ; Site 1256
    Repository Name: Woods Hole Open Access Server
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  • 7
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    Deep-tow magnetic anomaly study of the Pacific Jurassic Quiet Zone and implications for the geomagnetic polarity reversal timescale and geomagnetic field behavior (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 113 (2008): B07110, doi:10.1029/2007JB005527.
    Description: The Jurassic Quiet Zone (JQZ) is a region of low-amplitude magnetic anomalies whose distinctive character may be related to geomagnetic field behavior. We collected deep-tow magnetic profiles in Pigafetta Basin (western Pacific) where previous deep-tow data partially covered the JQZ sequence. Our goals were to extend the survey through the JQZ, examine anomaly correlations, and refine a preliminary geomagnetic polarity timescale (GPTS) model. We collected a series of closely spaced profiles over anomaly M34 and Ocean Drilling Program Hole 801C to examine anomaly correlation in detail, one profile in between previous profiles, and two long profiles extending the survey deeper into the JQZ. Anomaly features can be readily correlated except in a region of low-amplitude, short-wavelength anomalies in the middle of the survey area (“low-amplitude zone” or LAZ). The small multiprofile surveys demonstrate anomaly linearity, implying that surrounding anomalies are also linear and likely result from crustal recording of geomagnetic field changes. We constructed a GPTS model assuming that most anomalies result from polarity reversals. The polarity timescale is similar to the polarity sequences from previous studies, but its global significance is uncertain because of problems correlating anomalies in the LAZ and the ambiguous nature of the small JQZ anomalies. Overall anomaly amplitude decreases with age into the LAZ and then increases again, implying low geomagnetic field strength, perhaps related to a rapidly reversing field. Other factors that may contribute to the LAZ are interference of anomalies over narrow, crustal polarity zones and poorly understood local tectonic complexities.
    Description: This research was supported by the National Science Foundation grants OCE-0099161 and OCE-0099237. Tominaga was partly supported by funds from the Jane and R. Ken Williams ’45 Chair in Ocean Drilling Science, Education, and Technology.
    Keywords: Magnetic anomalies ; Pacific Jurassic Quiet Zone ; Geomagnetic polarity ; Timescales
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/postscript
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  • 8
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    M-sequence geomagnetic polarity time scale (MHTC12) that steadies global spreading rates and incorporates astrochronology constraints (2012)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 117 (2012): B06104, doi:10.1029/2012JB009260.
    Description: Geomagnetic polarity time scales (GPTSs) have been constructed by interpolating between dated marine magnetic anomalies assuming uniformly varying spreading rates. A strategy to obtain an optimal GPTS is to minimize spreading rate fluctuations in many ridge systems; however, this has been possible only for a few spreading centers. We describe here a Monte Carlo sampling method that overcomes this limitation and improves GPTS accuracy by incorporating information on polarity chron durations estimated from astrochronology. The sampling generates a large ensemble of GPTSs that simultaneously agree with radiometric age constraints, minimize the global variation in spreading rates, and fit polarity chron durations estimated by astrochronology. A key feature is the inclusion and propagation of data uncertainties, which weigh how each piece of information affects the resulting time scale. The average of the sampled ensemble gives a reference GPTS, and the variance of the ensemble measures the time scale uncertainty. We apply the method to construct MHTC12, an improved version of the M-sequence GPTS (Late Jurassic-Early Cretaceous, ~160–120 Ma). This GPTS minimizes the variation in spreading rates in a global data set of magnetic lineations from the Western Pacific, North Atlantic, and Indian Ocean NW of Australia, and it also accounts for the duration of five polarity chrons established from astrochronology (CM0r through CM3r). This GPTS can be updated by repeating the Monte Carlo sampling with additional data that may become available in the future.
    Description: A.M. and J.H. were supported by NSF grant OCE 09–26306, M.T. was supported by a Woods Hole Oceanographic Institution postdoctoral scholarship, and J.E.T.C. was supported by NSF grant OCE 09–60999.
    Description: 2012-12-30
    Keywords: Monte Carlo simulation ; Geomagnetic polarity time scale ; Marine magnetic anomalies
    Repository Name: Woods Hole Open Access Server
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  • 9
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    Lava deposition history in ODP Hole 1256D : insights from log-based volcanostratigraphy (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2010. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 11 (2010): Q05003, doi:10.1029/2009GC002933.
    Description: A log-based volcanic stratigraphy of Ocean Drilling Program Hole 1256D provides a vertical cross-section view of in situ upper crust formed at the East Pacific Rise (EPR) with unprecedented resolution. This stratigraphy model comprises ten electrofacies, principally identified from formation microscanner images. In this study, we build a lava flow stratigraphy model for the extrusive section in Hole 1256D by correlating these electrofacies with observations of flow types from the modern EPR, such as sheet flows and breccias, and pillow lavas and their distribution. The resulting flow stratigraphy model for the Hole 1256D extrusive section represents the first realization of detailed in situ EPR upper oceanic crust construction processes that have been detected only indirectly from remote geophysical data. We correlated the flow stratigraphy model with surface geology observed from the southern EPR (14°S) by Shinkai 6500 dives in order to obtain the relationship between lava flow types and ridge axis-ridge slope morphology. This dive information was also used to give a spatial-time reference frame for modeling lava deposition history in Hole 1256D. In reconstructing the lava deposition history, we interpreted that the origins of the ∼100 m thick intervals with abundant pillow lavas in Hole 1256D are within the axial slope where pillow lavas were observed during the Shinkai 6500 dives and previous EPR surveys. This correlation could constrain the lava deposition history in Hole 1256D crust. Using the lateral scale of ridge axis–ridge slope topography from the Shinkai 6500 observations and assuming the paleospreading rate was constant, 50% of the extrusive rocks in Hole 1256D crust were formed within ∼2000 m of the ridge axis, whereas nearly all of the remaining extrusive section was formed within ∼3000 m of the ridge axis. These results are consistent with the upper crustal construction model previously suggested by seismic studies.
    Description: S.U. was supported by the Center of Deep Earth Exploration (CDEX) for travel fares and by Monbusho grant-in-aid for research 18540472.
    Keywords: Ocean Drilling Program ; Hole 1256D ; Volcanostratigraphy ; East Pacific Rise ; Wireline logging
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 10
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    “Equator Crossing” of Shatsky Rise?: New insights on Shatsky Rise tectonic motion from the downhole magnetic architecture of the uppermost lava sequences at Tamu Massif (2012)
    American Geophysical Union
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 39 (2012): L21301, doi:10.1029/2012GL052967.
    Description: Shatsky Rise is a Large Igneous Province (LIP) currently located in the northwestern Pacific. New downhole magnetic logging data from Integrated Ocean Drilling Program (IODP) Hole U1347A at Tamu Massif of Shatsky Rise captured the magnetic architecture in the uppermost lava sequence, providing a rare opportunity to investigate a time series of the intra-plate volcanism in conjunction with the Pacific plate construction history centered at the triple junction. Logging data results indicate that Tamu Massif was formed during normal polarity periods south of the paleoequator and crossed the equator at some point in the M19–M17 period. Combining these new observations with previous interpretations of the massif's tectonic history, a time series of the latitudinal tectonic motion of a LIP and the underlying Pacific plate during the plateau formation is postulated.
    Description: This project was supported by the IODP-US Science Support Program (Consortium for Ocean Leadership) Expedition 324 Post Expedition Award.
    Description: 2013-05-03
    Keywords: Integrated Ocean Drilling Program ; Downhole logging ; Large igneous province ; Magnetic architecture
    Repository Name: Woods Hole Open Access Server
    Type: Article
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