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Past Projects Archive

IODP Exp. 376

Expedition 376 will investigate the fundamental, interrelated processes governing subseafloor hydrothermal activity at Brothers volcano, southern Kermadec arc (IODP proposal 818-Full2). The primary objectives are to (1) Characterize the subsurface, magma-derived volatile phase for testing models predicting the existence of either a single-phase gas or a two-phase brine-vapor; (2) Explore the distribution of base and precious metals and metalloids at depth as well as the reactions that have taken place during their precipitation along fluid migration pathways to the seafloor; (3) Quantify the mechanisms and extent of fluid-rock interaction, and what this implies for the mass flux of metals and metalloids to the ocean as well as the role of magma-derived carbon and sulfur species in acting as agents for those fluxes; and (4) Assess the diversity, extent, and metabolic pathways of microbial life in an extreme, acidic, and metal-toxic (sub)volcanic environment.

IODP Exp. 375

Expedition 375 will investigate slow slip events (SSE) along the northern Hikurangi subduction margin (IODP proposals 781A-Full and 781A-Add). Hikurangi SSE recur every ~2 years so we can monitor changes in deformation rate and associated chemical and physical properties surrounding the SSE source area throughout an entire slow slip cycle. Sampling material from the sedimentary section and oceanic basement of the subducting plate and from primary active thrusts in the outer accretionary wedge, in combination with LWD data, will reveal the rock properties, composition, and lithological and structural character of the active faults involved in the SSE, as well as material that is transported downdip to the SSE source region. Coring and downhole measurements from four sites will be integrated with the LWD data collected during Expedition 372 (see above). In addition, borehole observatories will be installed at the thrust fault site and a site in the upper plate to monitor hydrologic, chemical, and physical processes during the SSE cycle.

IODP Exp. 374

The Ross Sea West Antarctic Ice Sheet (WAIS) History Expedition (based on IODP Proposals 751 Full2, 751 Add, & 751 Add2) will investigate the relationship between climatic/oceanic change and WAIS evolution through the Neogene and Quaternary. Numerical models indicate that this region is highly sensitive to changes in ocean heat flux and sea level, making it a key target to understand past ice sheet variability under a range of climatic forcings. The proposed drilling is designed to optimize data-model integration for improved understanding of Antarctic Ice Sheet mass balance during climates warmer than present. Core and log data from a transect of six sites from the outer continental shelf to rise in the eastern Ross Sea will be used to: (1) evaluate WAIS contribution to far-field ice volume and sea level estimates; (2) reconstruct ice proximal atmospheric and oceanic temperatures to identify periods of past polar amplification and assess forcings/feedbacks; (3) assess the role of oceanic forcing (e.g., sea level, temperature) on WAIS instability; (4) document WAIS sensitivity to Earth’s orbital configuration under varying climate boundary conditions; and (5) reconstruct eastern Ross Sea bathymetry to examine relationships among seafloor geometry, ice sheet instability, and global climate.

IODP Exp. 372

Expedition 372 has two primary objectives. These are (1) to investigate the relationship between gas hydrate and underwater landslides (IODP proposals 841-APL2 & 841-Add); and (2) to characterize sediment and fault zone structures and physical properties associated with recurring shallow slow slip events along the Hikurangi subduction interface (IODP proposals 781A-Full & 781A-Add). Submarine slides are thought to occur as catastrophic events, and as such pose a significant geohazard potentially causing tsunamis and damaging seafloor installations. Dissociation of gas hydrate has been proposed as a driver of seafloor destabilization, but there is evidence that gas hydrate itself may lead to seafloor weakening through creeping seafloor deformation. We will test the hypothesis that interstitial gas hydrate, like ice, may exhibit viscous behavior leading to slow deformation as observed in terrestrial rock glaciers. Alternatively, permeability reduction from gas hydrates may lead to overpressure, hydrofracturing, and seafloor weakening. To elucidate how gas hydrates promote creeping behavior, we will collect logging-while-drilling (LWD) data at three sites as well as APC cores, pressurized cores, and penetrometer data at one of the LWD sites.

IODP Exp. 381

This expedition will drill within the active Corinth Rift, Greece, where deformation rates are high, the syn-rift succession is preserved and accessible, and a dense, seismic database provides a high resolution fault network and seismic stratigraphy for the recent rift history but with limited chronology. In the Gulf of Corinth, the expedition can achieve an unprecedented precision of timing and spatial complexity of rift-fault system development and rift-controlled drainage system evolution in the first 1-2 Myr of rift history.

The expedition aims to resolve at a high temporal and spatial resolution how faults evolve, how strain is (re-)distributed, and how the landscape responds within the first few Myrs in a non-volcanic continental rift, as modulated by Quaternary changes in sea level and climate. High horizontal spatial resolution (~1-3 km) is provided by a dense grid of seismic profiles offshore that have been recently fully integrated, complemented by extensive outcrops and fault analysis onshore. High temporal resolution (~20-50ka) will be provided by seismic stratigraphy tied to core and log data from three carefully located boreholes to sample the recent syn-rift sequence.

IODP Exp. 371

The Tasman Frontier expedition (based on IODP Proposals 832 Full2 and 832 Add) will investigate the Eocene Tonga-Kermadec (TK) subduction initiation (SI) and evaluate whether a period of high-amplitude long-wavelength compression led to initiation of TK subduction or determine if alternative geodynamic models were involved. Core and log data from boreholes in the Norfolk Ridge, New Caledonia Trough, Lord Howe Rise and Tasman abyssal plain will provide constraints on seismic stratigraphic interpretations and the timing and length scale of deformation and uplift associated with the largest known global SI event and change in plate motion. The Paleogene and Neogene sediments will also constrain paleoceanographic changes caused by SI as well as tropical and polar climatic teleconnections and the transition from greenhouse to icehouse climate states in a region with large meridional variations in surface water properties in a strategic "Southern Ocean Gateway" setting.

IODP Exp. 367/368

The two South China Sea (SCS) Rifted Margin Expeditions (based on IODP Proposals 878-CPP and 878-Add) aim to understand the mechanisms of lithosphere extension during continental breakup at a non-volcanic rifted margin.

The SCS margin shows similarities to the hyper-extended Iberia-Newfoundland margins, possibly including exhumed and serpentinized mantle within the Continent-Ocean-Transition (COT). However, modeling studies suggest that there can be mechanisms of plate weakening other than serpentinization of sub-continental lithospheric mantle. Two competing models for plate rupture (in the absence of excessively hot asthenospheric mantle) have widely different predictions for development of the SCS margin.

To discriminate between these models, a series of deep-penetration sites will be drilled across a 150–200 km wide zone of highly extended seaward-thinning crust with a well-imaged COT zone. Coring and logging deep/basal sediments and the underlying basement is the primary objective.

The proposed drill sites determine the nature of crust within the COT and constrain (a) post-breakup crustal subsidence, (b) how soon after breakup igneous crust started to form, (c) timing of rifting, and (d) rate of extension. The science objectives can be effectively addressed at these drill sites because of the existing constraints on SCS formation and stratigraphy that include industry drilling, ODP Leg 184 and IODP Expedition 349 drilling, as well as due to the young (Paleogene) rifting of the margin and absence of excessively thick post-rift sediments.

IODP Exp. 366

The IODP Mariana Convergent Margin Expedition (based on IODP proposals 505-Full5 and 693-APL) will investigate geochemical, tectonic, and biological processes at intermediate depths of an active subduction zone. This expedition will core the summits and flanks of serpentinite mud volcanoes on the forearc of the Mariana system, a non-accretionary convergent plate margin in the western Pacific. In addition, a reentry cone and casing system will be installed at three of these sites to provide the infrastructure for post-cruise installation of long-term monitoring; the existing Hole 1200C borehole observatory (CORK) will also be removed.

Sediments, rocks, and fluids recovered during this expedition will be used to (1) to understand mass transport and geochemical cycling in subduction zones of non-accretionary forearcs at convergent margins; (2) to ascertain spatial and temporal variability of slab-relate fluids in the forearc environment to trace dehydration, carbonate dissolution, and water/rock reactions in the subduction zone; (3) to understand physical properties of the subduction zone as controls over dehydration reactions and seismicity; (4) to study spatial and temporal variability in metamorphic and tectonic processes and the history of these processes in non-accretionary forearc regions; and (5) to investigate controls over biological activity associated with these mud volcano processes.

IODP Exp. 363

The Western Pacific Warm Pool (WPWP) Expedition aims to understand the interaction between climate and the WPWP from the middle Miocene to Holocene. A series of sites will be drilled in the western equatorial Pacific and eastern Indian Ocean to investigate (1) the role and response of the WPWP to millennial climate variability during the late Quaternary, (2) changes in the WPWP and relation to monsoon activity on orbital timescales during the Pliocene-Pleistocene, (3) changes in the Indonesian Throughflow during the Pliocene-Pleistocene, and (4) the long-term evolution of WPWP sea surface (SST) and intermediate water temperatures (IWT) and water chemistry since the middle Miocene. 
Sediments obtained from these sites will investigate the relationships between millennial-scale variability in the tropical Pacific and in the northern Atlantic; the controls on tropical Pacific SST patterns on various time scales; the response of the hydrologic cycle and the mechanisms controlling these variations; the evolution of the WPWP from the mid-Miocene Climate Optimum to the present; and the relationships between changes in the equatorial Pacific mean climate state and dynamical processes and how they relate to the Pliocene-Pleistocene transitions.

IODP Exp. 370

Biomass of subseafloor microbial life is at least comparable to that in the oceans. The massive buried biosphere plays an important role on a global scale in carbon sequestration, element cycles, and Earth's evolution. In 2012, IODP Expedition 337 unveiled the presence of microbial life at almost 2.5 km below the sea floor (Inagaki et al. 2015). But a central question of deep biosphere community remained unsolved; what is the vertical extent of the habitable zone on Earth, and by inference, the factors that limit life’s maximum depths?

IODP Expedition 370, T-Limit of the Deep Biosphere off Muroto, will tackle this question by drilling through the sediments in the central Nankai Trough off Japan. Anomalously high heat flow regimes in this area result in temperatures of about 130°C at the sediment/basement interface (1210 mbsf), and make the site an ideal target for in-depth examination of subseafloor microbial life close its upper temperature limit.