Geology & Geophysics Data Sets

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  • Dataset
    Images of cellular ultrastructure of benthic foraminifera from Arctic seeps
    (Woods Hole Oceanographic Institution, 2021-11-01) Bernhard, Joan M. ; Le Roux, Véronique ; Martin, Jonathan B.
    Dissociation of methane hydrates due to ocean warming releases methane, a powerful greenhouse gas, to the atmosphere. Dissociation of gas hydrates may have led to rapid and dramatic environmental changes in the past. Thus, understanding the impact of those events requires information about their timing and magnitudes. While the foraminiferal fossil record provides a powerful tool to understand past environmental conditions, seep-endemic foraminifera are unknown, which limits evaluation of seep-specific information. However, geographically widespread benthic foraminifera do inhabit seep sites, as documented widely in the literature, and may provide information useful to the understanding of past methane releases. In an effort to better understand how benthic foraminifera inhabit this chemosynthesis-based ecosystem, and if they faithfully record the methane emissions, we conducted a multipronged analysis of foraminifera associated with a gas hydrate emission site in the Arctic. Our goal was to simultaneously assess, in single representative calcareous benthic foraminiferal individuals, the cell biology, test stable carbon isotope ratio, and carbonate microstructure (e.g., wall thickness, survey for authigenic overgrowths), from samples collected south of Svalbard, or on Vestnesa Ridge, west of Svalbard). Serially, each specimen was scanned with microCT (computerized tomography) to assess test characteristics, then the test dissolved by acidification while capturing gas to measure stable carbon isotope ratio via continuous-flow mass spectrometry, and finally the remaining soft parts embedded and examined for cell ultrastructure with a Transmission Electron Microscope (TEM). TEM). Data from isotopic analyses, microCT scans and TEM imaging are presented here.
  • Dataset
    The rheological behavior of CO2 ice: application to glacial flow on Mars
    (Woods Hole Oceanographic Institution, 2020-10-13) Cross, Andrew J. ; Goldsby, David L. ; Hager, Travis F. ; Smith, Isaac B.
    Vast amounts of solid CO2 reside in topographic basins of the south polar layered deposits (SPLD) on Mars and exhibit morphological features indicative of glacial flow. Previous experimental studies showed that coarse-grained CO2 ice is 1–2 orders of magnitude weaker than water ice under Martian polar conditions. Here we present data from a series of deformation experiments on high-purity, fine-grained CO2 ice over a broader range of temperatures than previously explored (158–213 K). The experiments confirm previous observations of highly non-linear power-law creep at larger stresses, but also show a transition to a previously-unseen linear-viscous creep regime at lower stresses. We examine the viscosity of CO2 within the SPLD and predict that the CO2-rich layers may be stronger than previously thought. We also predict that CO2 ice flows much more readily than H2O ice on steep flanks of SPLD topographic basins, allowing the CO2 to pond as observed.
  • Dataset
    Sea-level rise will drive divergent sediment transport patterns on fore reefs and reef flats, potentially causing erosion on Atoll Islands
    ( 2019-11-12) Bramante, James F. ; Ashton, Andrew D. ; Storlazzi, Curt D. ; Cheriton, Olivia M. ; Donnelly, Jeffrey P.
    Atoll reef islands primarily consist of unconsolidated sediment, and their ocean-facing shorelines are maintained by sediment produced and transported across their reefs. Changes in incident waves can alter cross-shore sediment exchange and thus affect the sediment budget and morphology of atoll reef islands. Here we investigate the influence of sea-level rise and projected wave climate change on wave characteristics and cross-shore sediment transport across an atoll reef at Kwajalein Island, Republic of the Marshall Islands. Using a phase-resolving model, we quantify the influence on sediment transport of quantities not well-captured by wave-averaged models, namely wave asymmetry and skewness and flow acceleration. Model results suggest that for current reef geometry, sea level, and wave climate, potential bedload transport is directed onshore, decreases from the fore reef to the beach, and is sensitive to the influence of flow acceleration. We find that a projected 12% decrease in annual wave energy by 2100 CE has negligible influence on reef flat hydrodynamics. However, 0.5-2.0 m of sea-level rise increases wave heights, skewness, and shear stress on the reef flat, and decreases wave skewness and shear stress on the fore reef. These hydrodynamic changes decrease potential sediment inputs onshore from the fore reef where coral production is greatest, but increase potential cross-reef sediment transport from the outer reef flat to the beach. Assuming sediment production on the fore reef remains constant or decreases due to increasing ocean temperatures and acidification, these processes have the potential to decrease net sediment delivery to atoll islands, causing erosion.
  • Dataset
    Increased typhoon activity in the Pacific deep tropics driven by Little Ice Age circulation changes
    (Woods Hole Oceanographic Institution, 2020-09-02) Bramante, James F. ; Ford, Murray R. ; Kench, Paul S. ; Ashton, Andrew D. ; Toomey, Michael R. ; Sullivan, Richard M. ; Karnauskas, Kristopher B. ; Ummenhofer, Caroline C. ; Donnelly, Jeffrey P.
    The instrumental record reveals that tropical cyclone activity is sensitive to oceanic and atmospheric variability on inter-annual and decadal scales. However, our understanding of climate’s influence on tropical cyclone behavior is restricted by the short historical record and sparse prehistorical reconstructions, particularly in the western North Pacific where coastal communities suffer loss of life and livelihood from typhoons annually. Here we reconstruct three millennia of deep tropical North Pacific cyclogenesis and compare with other records to explore past regional typhoon dynamics. These records demonstrate low baseline activity prior to 1350 C.E. followed by a rapid culmination in activity during the Little Ice Age. This pattern is concurrent with hydroclimate proxy variability, suggesting a centennial-scale link between Pacific hydroclimate and tropical cyclone climatology. Using an ensemble of global climate models, we demonstrate that migration of the Pacific Walker circulation and variability in two Pacific climate modes during the Little Ice Age contributed to enhanced tropical cyclone activity in the tropical western North Pacific. Changes to Walker Circulation and expansion of the tropics projected for the next century invert Little Ice Age hydroclimate trends, potentially reducing typhoon activity in the deep tropical Pacific.
  • Dataset
    How does viscosity contrast influence phase mixing and strain localization?
    (Woods Hole Oceanographic Institution, 2020-07-07) Cross, Andrew J. ; Skemer, Philip ; Couvy, Hélène ; Olree, Elizabeth
    Ultramylonites—intensely deformed rocks with fine grain sizes and well‐mixed mineral phases—are thought to be a key component of Earth‐like plate tectonics, because coupled phase mixing and grain boundary pinning enable rocks to deform by grain‐size‐sensitive, self‐softening creep mechanisms over long geologic timescales. In isoviscous two‐phase composites, “geometric” phase mixing occurs via the sequential formation, attenuation (stretching), and disaggregation of compositional layering. However, the effects of viscosity contrast on the mechanisms and timescales for geometric mixing are poorly understood. Here, we describe a series of high‐strain torsion experiments on nonisoviscous calcite‐fluorite composites (viscosity contrast, ηca/ηfl ≈ 200) at 500°C, 0.75 GPa confining pressure, and 10−6–10−4 s−1 shear strain rate. At low to intermediate shear strains (γ ≤ 10), polycrystalline domains of the individual phases become sheared and form compositional layering. As layering develops, strain localizes into the weaker phase, fluorite. Strain partitioning impedes mixing by reducing the rate at which the stronger (calcite) layers deform, attenuate, and disaggregate. Even at very large shear strains (γ ≥ 50), grain‐scale mixing is limited, and thick compositional layers are preserved. Our experiments (1) demonstrate that viscosity contrasts impede mechanical phase mixing and (2) highlight the relative inefficiency of mechanical mixing. Nevertheless, by employing laboratory flow laws, we show that “ideal” conditions for mechanical phase mixing may be found in the wet middle to lower continental crust and in the dry mantle lithosphere, where quartz‐feldspar and olivine‐pyroxene viscosity contrasts are minimized, respectively.
  • Dataset
    Hunting Bubbles Falkor Cruise 2019
    (Woods Hole Oceanographic Institution, 2019-12-23) Michel, Anna P. M. ; Wankel, Scott D. ; Nicholson, David P. ; Fauria, Kristen ; Preston, Victoria Lynn
    The Hunting Bubbles Cruise took place in August-September 2018 on the R/V Falkor (cruise ID 180824). Ship time was provided by the Schmidt Ocean Institute. This cruise investigated transport of methane from seeps located on the Cascadia Margin. Data archived at the WHOAS repository supplements additional data from this cruise available at the R2R rolling deck to repository and at MGDS: Marine Geoscience Data System.
  • Dataset
    Causes of oceanic crustal thickness oscillations along a 74-Myr Mid-Atlantic Ridge flow line
    ( 2019-11-12) Shinevar, William J. ; Mark, Hannah F. ; Clerc, Fiona ; Codillo, Emmanuel A. ; Gong, Jianhua ; Olive, Jean-Arthur ; Brown, Stephanie M. ; Smalls, Paris T. ; Liao, Yang ; Le Roux, Véronique ; Behn, Mark D.
    Gravity, magnetic, and bathymetry data collected along a continuous 1400-km-long spreading-parallel flow line across the Mid-Atlantic Ridge indicate significant tectonic and magmatic fluctuations in the formation of oceanic crust over a range of timescales. The transect spans from 28 Ma on the African Plate to 74 Ma on the North American plate, crossing the Mid-Atlantic Ridge at 35.8 ºN. Gravity-derived crustal thicknesses vary from 3–9 km with a standard deviation of 1 km. Spectral analysis of bathymetry and residual mantle Bouguer anomaly (RMBA) show diffuse power at >1 Myr and concurrent peaks at 390, 550, and 950 kyr. Large-scale (>10-km) mantle thermal and compositional heterogeneities, variations in upper mantle flow, and detachment faulting likely generate the >1 Myr diffuse power. The 550- and 950-kyr peaks may reflect the presence of magma solitons and/or regularly spaced ~7.7 and 13.3 km short-wavelength mantle compositional heterogeneities. The 390-kyr spectral peak corresponds to the characteristic spacing of faults along the flow line. Fault spacing also varies over longer periods (>10 Myr), which we interpret as reflecting long-lived changes in the fraction of tectonically- vs. magmatically- accommodated extensional strain. A newly discovered off-axis oceanic core complex (Kafka Dome) found at 8 Ma on the African plate further suggests extended time periods of tectonically dominated plate separation. Fault spacing negatively correlates with gravity-derived crustal thickness, supporting a strong link between magma input and fault style at mid-ocean ridges.
  • Dataset
    Long-Term evolution of non-transform discontinuities at the Mid-Atlantic Ridge, 24°N - 27°30′N
    ( 2018-12) Zheng, Tingting ; Tucholke, Brian E. ; Lin, Jian
    We studied long-term evolution of non-transform discontinuities (NTDs) on the Mid-Atlantic Ridge from 0 to ~20-25 Ma crust using plate reconstructions of multibeam bathymetry, long-range HMR1 sidescan sonar, residual mantle Bouguer gravity anomaly, and gravity-derived crustal thickness. NTDs have propagated north and south with respect to flowlines of relative plate motion and both rapidly and slowly compared to the half spreading rate, and at times they have been quasi-stable. Fast, short-term (<2 m.y.) propagation is driven by reduced magma supply (increased extension) in the propagating ridge tip when NTD ridge-axis offsets are small (<~ 5 km). Slow propagation can be much longer term. Some NTDs show classic structures of rift propagation including inner and outer pseudofaults and crustal blocks transferred between ridge flanks by discontinuous jumps of the propagating ridge tip. In all cases crustal transfer occurs within the NTD valley. Aside from ridge-axis offset, the evolution of NTDs appears to be controlled by three factors: (1) Gross volume and distribution of magma supplied to ridge segments as controlled by 3D heterogeneities in mantle fertility and/or dynamic upwelling; this controls fundamental ridge segmentation. (2) The lithospheric plumbing system through which magma is delivered to the crust. (3) The consequent focusing of tectonic extension in magma-poor parts of spreading segments, typically at segment ends, which can drive propagation. We also observe long-wavelength (5-10 m.y.) RMBA asymmetry between the conjugate ridge flanks, and we attribute this to asymmetric distribution of density anomalies in the upper mantle.
  • Dataset
    Supplemental files from “Metazoans of redoxcline sediments in Mediterranean deep-sea hypersaline anoxic basins” (Bernhard et al., submitted, BMC Biology).
    ( 2015-10-05) Bernhard, Joan M. ; Morrison, Colin R. ; Pape, Ellen ; Beaudoin, David J. ; Todaro, M. Antonio ; Pachiadaki, Maria G. ; Kormas, Konstantinos Ar. ; Edgcomb, Virginia P.
    Link provides access to supplemental tables and figures to our manuscript regarding metazoans of redoxcline sediments in Mediterranean deep-sea hypersaline anoxic basins (DHABs). Specimens shown in supplemental figures are loriciferans collected from control and lower halocline sediments of L'Atalante Basin and Discovery Basin. Further details appear in Bernhard et al. (submitted).
  • Dataset
    Global viewport to deep-sea vents : dataset for spherical display systems
    ( 2014-09-11) Beaulieu, Stace E. ; Brickley, Annette ; Spargo, Abbey ; Joyce, Katherine ; Silva, Tim ; Patterson, Kathleen ; Madin, Katherine ; Emery, Meredith
    Spherical display systems, including digital globes, are new technologies increasingly used in both informal and formal education to display global datasets. By creating a narrative using multiple datasets, inter‐disciplinary concepts and linkages between Earth systems ‐ lithosphere, hydrosphere, atmosphere, and biosphere ‐ can be conveyed. The Woods Hole Oceanographic Institution, in collaboration with New Bedford Ocean Explorium, invites you to explore the deep sea with the Global Viewport to Deep‐Sea Vents: Dataset for Spherical Display Systems. Our content was developed for public audiences by a team of scientists, educators, and graphic artists. We created new content for digital globes that interweaves imagery obtained by deep‐diving vehicles with global datasets, including a new dataset locating the world's known hydrothermal vents and an animation showing where these vents were discovered every year since the first discovery in 1977. We provide site‐specific movies to show the diversity of geological settings and life at deep‐sea vents. Our two narratives, "Life Without Sunlight" and "Smoke and Fire Underwater,” are provided as compilation movies matched to interactive playlists for docent‐led presentations. Each narrative focuses on a set of Earth Science and Ocean Literacy Principles to educate and excite the public about dynamic geophysical and biological processes and exploration in the deep ocean. In Version 1, we provide datasets, movies, and educational materials prepared for NOAA’s Science on a Sphere® (SOS; http://sos.noaa.gov/), with our two compilation movies also formatted for Magic Planet (http://globalimagination.com).
  • Dataset
    Shipboard ADCP profiles, central equatorial Pacific Ocean, 2003-2012
    ( 2014-07-17) Karnauskas, Kristopher B. ; Witting, Jan H.
    This data set contains 23 individual NetCDF files, each containing subsurface zonal and meridional velocity profiles (along with time/space coordinates) measured by shipboard ADCP.
  • Dataset
    CTD data from coring cruise R/V Cape Hatteras CH1605 on the continental margin of the South Atlantic Bight and the Bahamas
    ( 2005-06) Bernhard, Joan M. ; McCorkle, Daniel C.
    These CTD data were collected during a nine-day cruise in early June 2005 on the R/V Cape Hatteras (CH09-05; Beaufort, NC – Beaufort, NC). The principal goal of the cruise was to collect foraminiferal “livestock” for multiple-carbonate-chemistry culture experiments. The main purpose of the CTD casts was to collect bottom water, which was used for shipboard sieving of the sediment samples. We also sampled bottom water for comparison with the shell chemistry of benthic foraminiferal field specimens. This included samples for oxygen, Dissolved Inorganic Carbon and Alkalinity to define bottom water carbonate chemistry and calcite saturation state, the d13C of DIC, and the d18O of water; the University of South Carolina group sampled for minor and trace elements, too. We also collected two CTD-rosette profiles to provide samples to Ms. Angie Knapp at Princeton University, for use in isotopic studies of the marine N cycle. The CTD data archived here were not processed or subjected to any quality control evaluation.
  • Dataset
    CTD data from coring cruise R/V Oceanus OC424-1 on the continental margin of the South Atlantic Bight and the Bahamas
    ( 2006-05) Bernhard, Joan M. ; McCorkle, Daniel C.
    These CTD data were collected during a twelve-day cruise in May 2006 on the R/V Oceanus (OC-424-1; Woods Hole, MA – Charleston, SC). The principal goal of the cruise was to collect foraminiferal “livestock” for multiple-carbonate-chemistry culturing experiments. The main purpose of the CTD casts was to collect bottom water, which was used for shipboard sieving of the sediment samples. We also sampled bottom water for comparison with the shell chemistry of benthic foraminiferal field specimens. This included samples for oxygen, Dissolved Inorganic Carbon and Alkalinity to define bottom water carbonate chemistry and calcite saturation state, the d13C of DIC, and the d18O of water; the University of South Carolina group sampled for minor and trace elements, too. The CTD data archived here were not processed or subjected to any quality control evaluation.