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The cruise track follows the Great-Cirlce along:
Passing through these points takes the ship north of the San Diego to Majuro Great Circle, on a route that is would be about 30 n.m. longer if no "surveying" deviations (zigzags, backtracks,etc) were made. Of course as many such deviations as time allows will be made, especially in the region between longitudes 132W and 142W. To be able to do this most effectively, while still having a good chance of staying on the fracture zone as far W as 156W before running out of time.
http://www.sio.ucsd.edu/supp_groups/shipsked/1999/allships99/99MV/Lonsdale/Lonsdale.html
Oceanic hot spots, leave trails of volcanoes that can be interpreted in terms of the motion of plates. The motion of the Pacific Plate is most prominently reflected in the Hawaiian/Emperor Island and Seamount Chains with a characteristic bend at about 42 Ma. The current estimate of the timing of this bend is almost ten million years later than what other models propose, and it has been suggested that the Hawaiian hot spot may have moved with respect to other hot spots. The Gilbert Ridge and the Tokelau seamount chain display a similar bend at their southern terminations and offer an opportunity to improve our accuracy of absolute Pacific Plate motion and to test for the validity of the fixed hot spot concept. This project will dredge rocks from these seamount chains and date samples by 40Ar/39Ar isotopic methods. The ultimate goal of this research project is to determine Pacific Plate motion between 70- 40 Ma, including the time when plate motion and/or moving hot spots caused the bend in the Hawaiian Emperor seamount chain. Determination of absolute plate motion has major implications for the forces that form ocean basins or mountains. Understanding the stability of hot spots helps us explain magma generation processes at intraplate volcanoes and constrain the underlying forces in the earth's interior. Here are the locations: Target Lat long
http://www.sio.ucsd.edu/supp_groups/shipsked/1999/allships99/99MV/Staudigel/Staudigel.html
http://www.sio.ucsd.edu/supp_groups/shipsked/1999/allships99/99MV/Hart/Hart.html
The scientific objectives of this research cruise are:
(1) To learn the age and origin of the oceanic crust that is entering the Tonga-Kermadec Trench. This will be done by mapping the crust's structure with multibeam bathymetry and magnetic profiling, and by radiometric dating of rock samples recovered by dredging
(2) To determine how the oceanic crust is tectonically deformed as it enters the trench, including how it is fractured by earthquake-producing faults. This will be done by multibeam bathymetry and single-channel seismic reflection profiling.
(3) To determine the chemical composition of the very old oceanic crust that is freshly exposed by the faulting in the trench. We plan to collect 20-30 rock samples by dredging scarps on the seabed, and to analyze the rocks back in San Diego.
The plan is to divide the time at sea, about equally, between (1) surveying with the multibeam echo-sounder, magnetometer, and seismic reflection profiler installed on R/V Melville, and (2) dredging rock samples (using a chain-bag dredge capable of recovering ~100kg of rock) from 5000m &endash; 7000m-deep seafloor. The surveying and dredging will be within a strip extending 100-200km seaward (east) of the axis of the trench, within the Exclusive Economic Zones of Samoa, Tonga, Niue and New Zealand. Participation by citizens of those countries is invited.
http://www.sio.ucsd.edu/supp_groups/shipsked/1999/allships99/99MV/Lonsdale2/Lonsdale2.html
The turning point 0 deg North, 164 deg 30 min. West. The actual track shall be a slight modification of just two straight-line legs with this point in the middle of them, but it will only be a few hours longer than these two legs. Sea Beam 12 kHz Echosounder, 3.5 kHz Echosounder and Magnetometer , will be collected.
http://www.sio.ucsd.edu/supp_groups/shipsked/1999/allships99/99MV/Larson/Larson.html
http://www.sio.ucsd.edu/supp_groups/shipsked/1999/allships99/99MV/Wilkes/Wilkes.html
The goal of our cruise is to obtain detailed chemical and isotopic information about the water column and sediments at a single site in the North Central Pacific. We (Druffel and Bauer) are studying the sources and cycling of organic carbon (both dissolved and particulate) between the surface and deep ocean, and will be comparing our radiocarbon results with those obtained during a previous occupation aboard Eve-1 in June of 1987.
We will collect water samples using 12- and 30-liter Go-flo bottles from 23 depths of the water column at a single site - 31°N, 159°W. We also plan to deploy in situ pumps on the trawl wire to collect suspended particulate matter at the same 23 depths. Sediment will be collected using 2-meter long gravity corers. Physical properties of the water column will be quantified using a Seabird CTD. Other samples to be collected will be: 1) large volume seawater samples using a 30-liter rosette, for radiocarbon measurement of sugars in the dissolved organic carbon (Repeta); large volume seawater samples for radiocarbon measurement of bacterial nucleic acids in the dissolved organic carbon.
ABSTRACT
The organic carbon generated biologically and distributed in the world ocean is intimately related to the functioning of the entire global carbon cycle as well to the ecology of the seas. The investigators on this project, who are established leaders in the study of the marine carbon cycle, will continue their research into the cycling of organic carbon in both its dissolved and particulate forms. The overall objective is to use natural and bomb-produced radiocarbon (14C) in dissolved and particulate organic matter to estimate turnover times and reservoir sizes in the ocean. They will examine the penetration of the bomb 14C signal into the carbon reservoirs since the last measurements were made one decade ago in the North Atlantic and North Pacific basins. They will also attempt to constrain the residence time of upper ocean refractory dissolved organic carbon by surveying the 14C composition of dissolved and particulate organic matter in specific organic classes such as protein, carbohydrate, and lipids.
Finally, they propose to measure 14C in bacterial nucleic acids to investigate bacterial utilization of old dissolved organic matter. The investigators anticipate that this work would lead to major new insights into the biogeochemical role played by these non-living forms of carbon in the world ocean.
http://www.sio.ucsd.edu/supp_groups/shipsked/1999/allships99/99MV/Bauer/Bauer.html
Two purposes to this cruise: 1) recover two moorings with temperature, seacat, and adcps, and 2) XBT/CTD/ADCP section between the ATOC acoustic source on Pioneer Seamount (off Half Moon Bay) and the source off the north side of Kauai.
http://www.sio.ucsd.edu/supp_groups/shipsked/1999/allships99/99MV/Howe/Howe.html
Project Summary
Adams (1990) has established a recurrence interval of about 590+/- 170 years for late Holocene turbidite events in selected basin-floor channels of the Washington and Oregon segments of the Juan de Fuca plate. He postulated that these 13 post-Mazama turbidites (Nelson et al., 1968) are generated by subduction zone earthquakes affecting the entire Juan de Fuca plate margin. We have been testing his hypothesis by using a similar approach to study turbidite events in different channel systems that monitor Washington, Oregon and California segments of the Cascadia Subduction Zone. If the same sequence and timing of events can be correlated in all major turbidite channel pathways, then it may be possible to verify Adams' hypothesis that there is a one-to-one correspondence between post-Mazama turbidites and great megathrust earthquakes involving the entire subduction zone. It also may be possible to establish a lack of correlation and thereby demonstrate segmentation of the margin. Furthermore, the turbidite event record offers the possibility of establishing an earthquake record as long as ~20 Ka, but certainly through the Holocene, for the entire margin. With such a record, the spatial and temporal history of seismicity in Cascadia can be examined un unprecedented detail over a meaningful time scale for understanding of clustering, earthquake sequences, and the behavior of adjacent segments (if any). Verification of the turbidite event paleoseismicity technique in Cascadia Basin will help develop fundamental methods that can be applied in any continental margin system with earthquake hazards and turbidite systems.
New large diameter cores and swath mapping are required to verify segmentation of the turbidite record and determine if: (1) the turbidite event record is disrupted by blocked channel pathways, (2) the younger event record is synchronous with the coastal record, (3) earthquake magnitude represented by turbidite events is > 7, and (4) earthquakes occur in clusters.
Our primary objective is to determine the late Quaternary turbidite event recurrence intervals in Cascadia basin-floor channel systems and evaluate implications of this event record for the paleoseismic history of the Cascadia subduction zone. We propose high-resolution AMS radiocarbon dating of planktonic forams from new cores to determine synchroneity and recurrence intervals of turbidite events in different segments of the basin. To define segment sources for the turbidite events, our objective is to carefully analyze channel pathways through swath mapping analysis, sidescan sonar and mineral composition of turbidites (Vallier et al., 1973; Sarna-Wojcicki et al., 1983). Our starting premise is that Adams' arguments for seimic triggering of regional turbidites are correct. In order to establish that the basin-floor turbidite event record is not biased by Late Quaternary events such as slumping or deformation of the channel, we propose to analyse swath bathymetric data in all channel systems of the margin to determine whether they have been influenced by such events. Off Oregon, Vancouver Island, and Northern California, suitable swath bathymetry data are available (California data just completed as of 10/97 by NOAA). Off Washington, we will collect selected swath bathymetry data in all channel pathways not previously surveyed.
The need for new cores stems from three problems with the available cores (these cores still exist and are stored at the Oregon state University Core Repository, containing all cores collected by west coast Institutions). First, the spatial coverage is not sufficient to consider the entire plate boundary system. New cores are needed to complete the spatial coverage. Second, There is some uncertainty in the location of the original cores, which were navigated with Loran A and Precision Depth Recorder. Third, and most important, the older small diameter cores contain few of the planktonic forams needed for dating. While cores outside the channels contain abundant planktonic and benthic forams (e.g. Ortiz et al., 1997, Lund and Mix submitted) Channel cores do not. The abundance is such that large (4") diameter cores will largely alleviate this sampling problem, and reduce the thickness of the stratigraphic interval needed to extract enough forams for dating, thus increasing the dating resolution.
Further details can be found at:
http://pandora.oce.orst.edu/turbidites.html
Other schedule constraints:
http://www.sio.ucsd.edu/supp_groups/shipsked/1999/allships99/99MV/Goldfinger/Goldfinger.html
http://www.sio.ucsd.edu/supp_groups/shipsked/1999/allships99/99MV/Worcester/Worcester.html
The main scientific objectives are to:
identify and examine the boundary of gas hydrate/free gas in this tectonic setting; recover cores with gas hydrate and possibly of newly located surface exposures of hydrate; link the distribution and chemistry of the hydrates to water column (including venting gas) and pore water chemistries, and to faults distribution; evaluate the susceptibility of this hydrate field to global change.
The Eel River basin north of Mendocino Fracture Zone (40o 50'N and 130o 35'W) is one of the select locations where gas hydrates have been identified in near-surface sediments. Sea-surface hydrates may be susceptible to contemporary change, and the northern California margin may become a prime site for future studies on the probability of global change perturbations from near-surface gas hydrate decomposition.
The rationale for the request for a two ship operation stems from our recent independent unsuccessful attempts to recover gas hydrates from the Eel River area. In the past 5-6 years, on two ONR funded cruises on the biogeochemistry and physical properties of slope sediments, I have tried to recover gas hydrates from this area by gravity coring but have failed. Hydrate formation reflects specific aspects of the environmental geochemistry and alters its physical and thermal properties. A Bottom Simulating Reflector (BSR) exists in the region and Brooks et al. (Marine Geology, 1991) after many attempts have recovered gas hydrate in several shallow cores (<6 m). My 30 to 40 gravity coring attempts in the area between 550-750 m water depth have failed. The extended gravity corer persistently bounced off the seafloor, and a high speed coring attempt returned bent. I thus concluded that the aerially widespread hard surface most likely consists of authigenic carbonate and/or methane hydrate, making a one ship coring operation chancy, expensive, hence difficult to justify. Dr. Brewer in the summer of 1997, in two dives has observed abundant massive carbonate slabs in the are, and located and sampled gas, mostly methane, from gas venting sites. Although methane bubbling was widespread he has not recovered gas hydrate; post cruise analyses indicated that the dives should have deeper. Clearly, methane advection is widespread in the area, some of its captured in gas hydrate, the rest escapes to the seafloor and is partially or fully oxidized. This is the CO2 source for the carbonates.
The most important advantage of operating with two ships is that sites of gas venting and/or hydrate exposure, and with no carbonate crust, would be precisely located with the MBARI submersible for surface controlled sampling (i.e. coring and hydrocasts) from the UC/Revelle. Dr. Brewer will also request from MBARI local microwave links between the two ships for greater monitoring of the dives and RHIB transfer of personnel ship to ship if weather permits. Other important advantages include: recovery of longer cores (~10 M), a larger scientific party, laboratory space, increased sample handling and analytical capabilities which allow a more comprehensive analytical program for the recovered hydrates. In addition to the two teams from SIO and MBARI we anticipate involving and interdisciplinary team of colleagues from the USGS in Menlo Park, UC Irvine, and probably Stanford. From the SIO team will include technicians, a post doctorate fellow, and a graduate student from my group and a number of interested graduate students. On this cruise the students will have the opportunity to learn and participate in a spectrum of ship operations, and sample preparation and analytical techniques.
The tentative cruise plan is to use the MBARI and NOAA acoustic survey data to establish a transect up-slope from 1000 to 400 m depth, across the oxygen minimum zone. A series of Tiburon dives along the identified transect will be carried out with visual survey and push cores for hydrate identification and pore water geochemistry (on UC/Revelle ) and to make key sited with an acoustic transponder. These sites will then be sampled with long cores and multi cores for gas hydrate and pore water chemistry and with hydrocasts for water chemistry, from UC/Revelle.
http://www.sio.ucsd.edu/supp_groups/shipsked/1999/allships99/99MV/Kastner/Kastner.html