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1. Diverse gas composition controls the Moby-Dick gas hydrate system in the Gulf of Mexico

   https://doi.org/10.1130/G49310.1  

   Portnov, Alexey; Cook, A.E.; Vadakkepuliyambatta, S. (August 2021, Geology)

   Abstract In marine basins, gas hydrate systems are usually identified by a bottom simulating reflection (BSR) that parallels the seafloor and coincides with the base of the gas hydrate stability zone (GHSZ). We present a newly discovered gas hydrate system, Moby-Dick, located in the Ship Basin in the northern Gulf of Mexico. In the seismic data, we observe a channel-levee complex with a consistent phase reversal and a BSR extending over an area of ∼14.2 km2, strongly suggesting the presence of gas hydrate. In contrast to classical observations, the Moby-Dick BSR abnormally shoals 150 m toward the seafloor from west to east, which contradicts the northward-shallowing seafloor. We argue that the likely cause of the shoaling BSR is a gradually changing gas mix across the basin, with gas containing heavier hydrocarbons in the west transitioning to methane gas in the east. Our study indicates that such abnormal BSRs can be controlled by gradual changes in the gas mix influencing the shape of the GHSZ over kilometers on a basin scale. 

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2. Creeping Gas Hydrate Slides

   https://doi.org/10.14379/iodp.proc.372A.2019  

   Pecher, I.A.; Barnes, P.M.; LeVay, L.J. (May 2019, Proceedings of the International Ocean Discovery Program)

   null (Ed.)

   International Ocean Discovery Program (IODP) Expedition 372 combined two research topics: actively deforming gas hydrate–bearing landslides (IODP Proposal 841-APL) and slow slip events on subduction faults (IODP Proposal 781A-Full). This expedition included a coring and logging-while-drilling (LWD) program for Proposal 841-APL and a LWD program for Proposal 781A-Full. The coring and observatory placement for Proposal 781A-Full were completed during Expedition 375. The Expedition 372A Proceedings volume focuses only on the results related to Proposal 841-APL. The results of the Hikurangi margin drilling are found in the Expedition 372B/375 Proceedings volume. Gas hydrates have long been suspected of being involved in seafloor failure. Not much evidence, however, has been found to date for gas hydrate–related submarine landslides. Solid, ice-like gas hydrate in sediment pores is generally thought to increase seafloor strength, which is confirmed by a number of laboratory measurements. Dissociation of gas hydrate to water and overpressured gas, on the other hand, may weaken and destabilize sediments, potentially causing submarine landslides. The Tuaheni Landslide Complex (TLC) on the Hikurangi margin shows evidence for active, creeping deformation. Intriguingly, the landward edge of creeping coincides with the pinch-out of the base of gas hydrate stability on the seafloor. We therefore proposed that gas hydrate may be involved in creep-like deformation and presented several hypotheses that may link gas hydrates to slow deformation. Alternatively, creeping may not be related to gas hydrates but instead be caused by repeated pressure pulses or linked to earthquake-related liquefaction. Plans for Expedition 372A included a coring and LWD program to test our landslide hypotheses. Because of weather-related downtime, the gas hydrate–related program was reduced and we focused on a set of experiments at Site U1517 in the creeping part of the TLC. We conducted a LWD and coring program to 205 m below the seafloor through the TLC and the gas hydrate stability zone, followed by temperature and pressure tool deployments. 

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3. Data report: gas hydrate assessment in Baffin Bay at IODP Expedition 400 drill sites

   https://doi.org/10.14379/iodp.proc.400.201.2025  

   Naim, F; Cook, AE; Knutz, PC; Jennings, AE; Childress, LB; Bryant, R; Cargill, SK; Coxall, HK; Frank, TD; Grant, GR; et al (July 2025, International Ocean Discovery Program)

   A gas hydrate assessment at International Ocean Discovery Program Expedition 400 drill sites was conducted using downhole logging and core data. Here, we calculate and present the base of gas hydrate stability zone at Expedition 400 drill sites in Baffin Bay, northwest Greenland. We used data from downhole logs and sediment cores from Sites U1603, U1604, U1607, and U1608 to assess hydrate and did not find evidence for the presence of hydrate. At Site U1606, only core data were acquired that showed a decrease in pore water salinity, potentially indicating the presence of hydrate; however, further confirmation was not possible due to the unavailability of downhole logging data. Because of the limitation of the acquired data at the drill sites, a further assessment to confirm the presence of hydrate was not possible. Although hydrate was not identified at any drill sites, hydrate might still be present in the region. 

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4. Physical Properties and Gas Hydrate at a Near‐Seafloor Thrust Fault, Hikurangi Margin, New Zealand

   https://doi.org/10.1029/2020GL088474  

   Cook, Ann E.; Paganoni, Matteo; Clennell, Michael Benedict; McNamara, David D.; Nole, Michael; Wang, Xiujuan; Han, Shuoshuo; Bell, Rebecca E.; Solomon, Evan A.; Saffer, Demian M.; et al (August 2020, Geophysical Research Letters)

   Abstract The Pāpaku Fault Zone, drilled at International Ocean Discovery Program (IODP) Site U1518, is an active splay fault in the frontal accretionary wedge of the Hikurangi Margin. In logging‐while‐drilling data, the 33‐m‐thick fault zone exhibits mixed modes of deformation associated with a trend of downward decreasing density,P‐wave velocity, and resistivity. Methane hydrate is observed from ~30 to 585 m below seafloor (mbsf), including within and surrounding the fault zone. Hydrate accumulations are vertically discontinuous and occur throughout the entire logged section at low to moderate saturation in silty and sandy centimeter‐thick layers. We argue that the hydrate distribution implies that the methane is not sourced from fluid flow along the fault but instead by local diffusion. This, combined with geophysical observations and geochemical measurements from Site U1518, suggests that the fault is not a focused migration pathway for deeply sourced fluids and that the near‐seafloor Pāpaku Fault Zone has little to no active fluid flow. 

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5. Hydrate‐filled Fracture Formation at Keathley Canyon 151, Gulf of Mexico, and Implications for Non‐vent Sites

   https://doi.org/10.1029/2019GC008637  

   Oti, Emma A.; Cook, Ann E.; Welch, Susan A.; Sheets, Julia M.; Crandall, Dustin; Rose, Kelly; Daigle, Hugh (November 2019, Geochemistry, Geophysics, Geosystems)

   Abstract Near‐vertical hydrate‐filled fractures are found in subseafloor marine muds, at both advective methane vent sites and at sites without obvious methane and fluid advection (non‐vent sites). At non‐vent sites, the mechanisms that transport methane to the fractures and control how hydrate‐filled fractures form are not well understood. However, these mechanisms are important to establish, as most of Earth's natural gas hydrate is likely bound in marine mud systems. Herein, we focus on understanding the origin of hydrate and how fracture form at non‐vent sites by examining previously hydrate‐bearing fractures in conventional cores taken from Keathley Canyon 151, U.S. northern Gulf of Mexico, drilled by the Gas Hydrate Joint Industry Project in 2005. We combine information from well logs, sediment cores, and science party results and add new X‐ray computed tomography of archival sections and scanning electron microcopy of core samples to develop a conceptual model. We propose that locally generated microbial methane is transported via diffusion from small pores in marine mud into biomineralized burrows with larger pore size in a process called short‐range migration. Hydrate forms in burrows once the methane diffuses into them and the dissolved methane concentration exceeds the solubility threshold. When hydrate fills a burrow, heave from additional hydrate growth places stress on the burrow edges, expands the fracture, and creates additional void space in which methane can diffuse and continue forming hydrate. Fractures slowly propagate in the direction of maximum principal stress. 

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