Boomerang Expedition
Boomerang Expedition
R/V MELVILLE
Leg 1
John Orcutt (619) 534-2887
Scripps Institution of Oceanography email:jorcutt@ucsd
MELT: OBS deployments
San Diego-Papeete
15 October - 24 November, 1995
Leg 2
Peter F. Lonsdale (619) 534-2855
Scripps Institution of Oceanography email: lonsdale@gdcmp1.ucsd.edu
SEA BEAM
James Hawkins (619) 534-2161
Scripps Institution of Oceanography email: jhawkins@ucsd
Rock Dredging
Paterno Castillo (619) 534-0383
Scripps Institution of Oceanography email: pcastillo@ucsd
Rock Dredging
Papeete -Chatham Is.
28 November - 10 December 1995
Leg 3
Ellen Druffel (714) 824-2116
University of California, Irvine email:edruffel@uci.edu
Radiocarbon Investigations
Chatham - Dunedin
11 December - 6 January 1996
Leg 4
transit from Dunedin to Hobart
9 - 13 January, 1996
Leg 5
Jean-C Sempere (619) 534-2855
Universitiy of Washington email: sempere@ocean.washington.edu
David Christie (503) 737-2296
Oregon State email: dave_christie@OCE.ORST.EDU
SEA BEAM
Hobart to Fremantle
16 January - 17 February, 1996
Leg 6
Kevin Johnson (808) 848-4124
Bishop Museum email: kevinj@soest.hawaii.edu
SEA BEAM, dredging, wax coring, gravity, magnetics
Fremantle - Port Hedland
23 February - 15 April 1996
Preface
Boomerang expedition is a return for Melville to Tahiti, New Zealand,
and Australia, visited not long ago during the Westward Expedition (1993-1995).
Webster's definition of Boomerang: boo.mer.ang n [Dharuk (Australian aboriginal
language of the Port Jackson area) bumariny] (1825) 1: a bent or angular throwing
club typically flat on one side and rounded on the other so that it soars or curves
in flight; esp: one designed to return near the thrower 2: an act or utterance that
backfires on its originator -- boomerang vi .
The research emphases of the expedition will be water column chemistry and marine
geology and geophysics. Melville will first work in the eastern South Pacific on
the MELT experiment with a multi-investigator team led by Dr. John Orcutt of SIO,
deploying some 47 ocean bottom seismometers (a record for deployment of OBS's by
one ship). These OBS's will remain at 17oS on the East Pacific Rise for nearly
six months, to be recovered later by R/V Thomas Thompson. This cruise ends in
Papeete, Tahiti.
During the transit from Tahiti to New Zealand, Dr. Peter Lonsdale of SIO will
conduct a Sea Beam bathymetric survey along a portion of Louisville Ridge, one of
the most active geologic regions in the south Pacific. He will be accompanied by
Drs. James Hawkins and Pat Castillo of Scripps to perform rock dredges along the
axis on the ridge. The work is funded in part by the University of California, and
makes use of a transit paid for by the National Science Foundation to get the ship to
the remote region of 55oS 180o for the following leg.
The work south of Chatham Island is an investigation of the organic carbon pools in
the cold waters of the southern Pacific Ocean at 55oS. Dr. Ellen Druffel of UC
Irvine will lead this leg to gather information regarding the global cycling of
organic and inorganic carbon.
Melville returns to the Indian Ocean via the Tasman Sea to work again at the
Australian-Antarctic Discordance, a sharp boundary between the Pacific Ocean and
Indian Ocean mantle isotopic provinces. Dr. Jean-C. Sempere of the University of
Washington plans to conduct a Sea Beam survey and marine geplogical/geochemical
sampling. Dr. Sempere has been waiting for use of Melville during the austral summer
to use the wide swath of Melville's Sea Beam 2000 system. This leg ends in Western
Australia.
Dr. Kevin Johnson, of The Bishop Museum in Honolulu, plans to conduct an extensive
geological survey of the western portion of the Southeast Indian Ridge, in the middle
of the southern Indian Ocean. This cruise will combine a Sea Beam survey, dredging,
and wax coring. The end port is still under discussion with the National Science
Foundation, but is tentatively planned for Port Hedland, Australia.
What follows are brief descriptions of each leg of this portion of Boomerang
expedition.
Leg 1
John Orcutt
Scripps Institution of Oceanography
San Diego-Papeete
15 October - 24 November, 1995
The Mantle ELectromagnetic and Tomography (MELT) Experiment is designed
to provide direct observational constraints on the distribution of melt
and the pattern of upwelling beneath a mid-ocean ridge. Seismic velocity
and attenuation and electrical conductivity are sensitive to temperature,
the presence of melt, and the orientation of crystal fabric within the upwelling
system. Studies of electromagnetic and seismic wave propagation in the mantle
with arrays of ocean-bottom instruments will furnish measurements that can be
inverted to find horizontal and vertical variations in velocity and conductivity
structure, which can be used to test models of flow. The needed measurements
cannot be gathered with remote methods or with adequate resolution using only a
small number of instruments. We propose to deploy a large array of 47 ocean-
bottom seismometers (OBS), for a six month period on the East Pacific Rise at about
17o25'S to record teleseismic and regional earthquake data. A major experiment with
this large number of instruments recording simultaneously for 6 months is required
to obtain the needed data.
A journey from San Diego Bar to MELT
* San Diego Bar to MELT area 1
*Start ÐÐ032 40.0' N 117 14.0' W
C 181.0 T 167.7 M ÐÐ016 00.0' S 118 00.0' W 2920.4 nm
Great circle distance= 2920.4 nm
Rhumbline course 180.9 T
Distance 2920.3 nm
great circle miles for journey= 2920
rhumbline miles for journey= 2920
A journey from MELTs Area to Papeete
* MELT area 2 to Papeete
*Start ÐÐ017 00.0' S 118 00.0' W
C 264.2 T 253.7 M ÐÐ017 11.1' S 120 00.0' W 115.2 nm
C 264.8 T 253.8 M ÐÐ017 48.4' S 130 00.0' W 573.4 nm
C 267.8 T 256.3 M ÐÐ017 55.2' S 140 00.0' W 571 nm
C 270.9 T 258.9 M ÐÐ017 33.0' S 149 34.0' W 547.1 nm
Great circle distance= 1806.8 nm
Rhumbline course 269 T
Distance 1808.9 nm
great circle miles for journey= 1807
rhumbline miles for journey= 1809
Total great circle miles for journey= 4727
Total rhumbline miles for journey= 4729
Total Sea Days 40
Total N-Miles 4727
Knots 12
Miles/day 288
Transit Days 16.41
Extra days (science) 23.58
Total days charged 43
Leg 2
Peter F. Lonsdale,
James Hawkins,
and
Paterno Castillo,
Scripps Institution of Oceanography
Papeete -Chatham
28 November - 10 December 1995
Dr. P. Lonsdale plans to use the ship during a NSF transit from Papeete
to Chatham Is. to collect Sea Beam/magnetic data. The track crosses several
major scarps which are known from previous surveys. These scarps offer the
opportunity to sample old Pacific Basin crust and possible exposures of the
upper mantle. Essentially nothing is known about the geology of the crust and
upper mantle that may be exposed on these scarps as they have not been sampled.
Hawkins and Castillo plan to make 8-10 dredge hauls along the scarps. The underway
data that will be acquired will give the necessary information about the sampling
sites. The add-on time will be used to make a local survey and to do the dredging.
Four to six hours is estimated for each dredge. The samples collected will be
brought back to SIO.
Survey Track:
A journey from Papeete to Chatham Island NZ
* Papeete to waypoint 1
*Start ÐÐ017 33.0' S 149 34.0' W
C 239.4 T 226.9 M ÐÐ017 47.6' S 150 00.0' W 28.7 nm
C 239.5 T 227.8 M ÐÐ022 57.0' S 160 00.0' W 641.6 nm
C 243.0 T 232.2 M ÐÐ026 00.0' S 167 00.0' W 423.7 nm
Great circle distance= 1094.1 nm
Rhumbline course 242.4 T
Distance 1095.7 nm
* waypoint 1 to waypoint 2
*Start ÐÐ026 00.0' S 167 00.0' W
C 156.6 T 146.6 M ÐÐ030 00.0' S 165 00.0' W 262.3 nm
Great circle distance= 262.3 nm
Rhumbline course 156.2 T
Distance 262.3 nm
* waypoint 2 to waypoint 3
*Start ÐÐ030 00.0' S 165 00.0' W
C 197.0 T 187.0 M ÐÐ040 00.0' S 169 00.0' W 631.2 nm
Great circle distance= 631.2 nm
Rhumbline course 198.1 T
Distance 631.4 nm
* waypoint 3 to Chatham Island NZ
*Start ÐÐÈ 040 00.0' S 169 00.0' W
C 232.3 T 222.3 M ÐÐ040 35.0' S 170 00.0' W 57.6 nm
C 232.9 T 217.9 M ÐÐ043 57.0' S 176 31.0' W 352.7 nm
Great circle distance= 410.3 nm
Rhumbline course 234.7 T
Distance 410.6 nm
Total great circle miles for journey= 2398
Total rhumbline miles for journey= 2400
Total Sea Days 11.5
Total N-Miles 2398
Knots 11
Miles/day 264
Survey Days 9
Extra days (dredging & survey) 2.5
Total days charged 13
Ellen Druffel, University of California, Irvine
Co-PI: James Bauer (VIMS)
Chatham - Dunedin
10 December - 6 January 1996
On R/V Melville in December 95, this cruise will investigate the organic
carbon pools in the water column and in surface sediment at an open ocean
site in the Southern Ocean (55oS, 180o). Collection of seawater using 12-
and 30-L Go-flo bottles will be done to enable carbon isotopic measurements
and concentrations of dissolved and colloidal organic carbon (DOC, COC) and
dissolved inorganic carbon (DIC). In situ Yentsch pumps will be used to
collect samples from 18 depths in the water column for particulate organic
carbon (POC) concentration and isotope analyses. A gravity corer will be
used to collect surface sediment. In the laboratories at UCI, SIO and VIMS,
they will measure concentrations and carbon isotope ratios (Æ14C, d13C) in
the following pools: ultra-violet and high-temperature catalytically-oxidizable
fractions of DOC (DOCuv and DOChtc), suspended POC (POCsusp), COC, specific
organic constituents (total hydrolyzable amino acids, total carbohydrates,
total lipids) of suspended POC and COC, surface sediment, marine snow, and
dissolved inorganic carbon (DIC). These data will be compared with those
available for the North Atlantic and North Pacific, and will reflect potential
differences in carbon cycling and transformations in polar and temperate regions.
The following questions will be addressed: 1) Do the Æ14C profiles in
Southern Ocean DOC, POCsusp , and COC support our hypothesis that deep DOC
is transported quasi-conservatively through the world's deep ocean?
2) From what depths do specific organic constituents of the COC, and
POCsusp originate and how are they recycled? 3) What are the sources of
carbon to marine snow, and are the labile, surface-derived compounds utilized
exclusively during remineralization? 4) What is the overall labile and
refractory nature of DOC with respect to its heterotrophic utilization, and
what does the Æ14C signature of micro-heterotrophic biomass reveal about the
assimilation of DOC/COC/POC in the deep ocean?
The proposed field and laboratory investigations will help us to understand
some of the important cycling rates of and transformation pathways between
DOC and POC in open ocean waters. This reflects the first study of 14C in DOC
and POCsusp in a polar ocean, and will help to reveal information regarding the
global cycling of organic and inorganic carbon.
A journey from Chatham Island NZ to Dunedin NZ planned 7/20/95
¥ Chatham Island NZ to Druffel's Waypoint
¥Start ÐÐ043 57.0' S 176 31.0' W
C 190.3 T 170.3 M ÐÐ055 00.0' S 180 00.0' W 676.5 nm
C 359.8 T 351.3 M ÐÐ055 00.0' S 180 00.0' W 000.0 nm
Great circle distance= 676.5 nm
Rhumbline course 191.6 T
Distance 676.8 nm
¥ Druffel's Waypoint to Dunedin NZ
¥Start ÐÐÈ 055 00.0' S 180 00.0' W
C 322.7 T 325.7 M ÐÐ045 53.0' S 170 31.0' E 654.9 nm
Great circle distance= 654.9 nm
Rhumbline course 326.5 T
Distance 656.2 nm
Total great circle miles for journey= 1331
Total rhumbline miles for journey= 1333
Total Sea Days 26
Total N-Miles 1331
Knots 11
Miles/day 264
Transit Days 5
Extra days (station) 21
Total days charged 29
Leg 4
transit from Dunedin to Hobart
9 - 13 January, 1996
The only science to be conducted on this transit will be the collection of
unprocessed Sea Beam data.
A journey from Dunedin NZ to Hobart AUS
* Dunedin NZ to Hobart Aus
*Start ÐÐ045 53.0' S 170 31.0' E
C 272.0 T 275.0 M ÐÐ045 52.2' S 170 00.0' E 21.6 nm
C 272.3 T 272.0 M ÐÐ045 08.5' S 160 00.0' E 422.5 nm
C 279.5 T 276.0 M ÐÐ043 29.3' S 150 00.0' E 440.3 nm
C 286.5 T 279.8 M ÐÐ042 53.0' S 147 21.0' E 121.5 nm
Great circle distance= 1005.9 nm
Rhumbline course 280.3 T
Distance 1009.6 nm
Total great circle miles for journey= 1006
Total rhumbline miles for journey= 1010
Total Sea Days 3.666
Total N-Miles 1006
Knots 11.5
Miles/day 276
Transit Days 3.64
Extra days 0
Total days charged 5
Leg 5
Jean-C Sempere, Universitiy of Washington
David Christie, Oregon Station
Hobart to Fremantle
16 January - 17 February, 1996
The sharp boundary between the distinctive Pacific Ocean and Indian Ocean
mantle isotopic provinces, presently located within the Australian-Antarctic
Discordance (AAD), has been migrating westward for at least the last 3-5 Ma,
but the geometry and long-term history of this migration are not known. This
leg of the R/V Melville is an ODP site survey that will focus our drilling
objectives by constraining the younger (<10 Ma) history of the migration through
dredge sampling and geochemical analysis. This study will also contribute to a
better understanding of the physical and chemical processes underlying both the
isotopic boundary and the Australian-Antarctic Discordance.
This investigation will determine the geometry of the isotopic boundary over the
last 10 Ma by geochemical sampling along isochrons and possibly by identification
of crustal thickness variations and discordant morphotectonic traces in seafloor
topography. In particular the investigators propose to determine whether the isotopic
boundary has been associated with the AAD and/or its depth anomaly since rifting
began, or whether it represents long-term westward migration of Pacific mantle into
the widening gap between the Australian and Antarctic continents. These geophysical
studies will address the spatial and temporal relationships between the isotopic
boundary and the residual depth anomaly associated with the AAD, focusing on the
nature and extent of crustal thickness variations and their implications for mantle
flow and mantle temperature variations beneath this region.
This investigation will be done by performing 35 dredges, a single channel seismic
survey using 80 cu. in. water guns, and a SEA BEAM 2000 survey in the basic mode
operation. In addition, gravity and magnetics data will be collected through-out
this cruise.
A journey from Hobart AUS to Fremantle AUS
* Hobart AUS to Sempere1 area
*Start ÐÐ042 53.0' S 147 21.0' E
C 268.0 T 258.0 M ÐÐ042¡ 49.9' S 140 00.0' E 323.2 nm
C 273.0 T 262.8 M ÐÐ042¡ 00.0' S 130 00.0' E 445.5 nm
Great circle distance= 768.7 nm
Rhumbline course 273.9 T
Distance 770 nm
* Sempere 2 area to Fremantle AUS
*Start ÐÐ050 00.0' S 128¡ 00.0' E
C 328.5 T 318.0 M ÐÐ039 35.3' S 120 00.0' E 710.6 nm
C 334.2 T 330.4 M ÐÐ032 03.0' S 115 45.0' E 497.1 nm
Great circle distance= 1207.7 nm
Rhumbline course 332.8 T
Distance 1211.4 nm
Total great circle miles for journey= 1976.4
Total rhumbline miles for journey= 1981.4
Total Sea Days 31.666
Total N-Miles 1976.4
Knots 11
Miles/day 264
Transit Days 7.48
Extra days (dredging) 24.17
Total days charged 37
Leg 6
Kevin Johnson, Bishop Museum
Fremantle - Port Hedland
23 February - 15 April 1996
Our 50+/ -day cruise plan, outlined below, involves ~38.5 days of station time with
slightly more time for surveying than for sampling. With 10 km-spaced lines crossing
the axis, we will obtain nearly complete bathymetry coverage from 32oS, 77oE, about
500 km north of the northern edge of the ASP Platform, to about 41.5oS, 79oE which is
about 200 km southeast of the southeastern edge of the platform. This "100%-coverage"
part of the survey will cover 720 km of ridge length and the intervening fracture
zones. Continuing to the southeast, we will survey the rest of that ridge segment to
about 42oS, 82oE at ~50% coverage (20 km line-spacing).
For the 720 km long "100%" portion of the survey, we will have 72 sampling stations,
yielding an average along-axis spacing of 10 km; for the 210 km long "50%" portion of
the survey, we will have 11 rock sample stations (every ~20 km). Both the survey and
sampling portions of the program are adjustable should we become short of time or
encounter bad weather.
While at sea, we plan to survey for 2-3 days (depending on the length of individual
segments), 100-150 km along-axis, then double-back to the axis at the start of the
prior survey, dredge and wax-core for 1.5-2.5 days, then continue to the next survey
segment. This interleaving of work will provide good base maps prior to dredging,
geophysical tie-lines, gap-filling opportunities, extra coverage of shallow features
that will have less than 100% coverage, time to work on winches, time to "catch up"
for the sampling team, and variety in the cruise routine. Tie lines are essential for
estimating and improving the reliability of geophysical data, particularly the gravity
data which may be degraded in heavy seas.
Although this strategy requires somewhat more steaming than mapping the whole area,
then returning back along the ridge axis sampling the entire length, the flexibility
it provides for adjusting the schedule between mapping and sampling activities will
be necessary for accommodating changing weather conditions.
The ~14.5 days of transit include 3.8 days to follow and coarsely sample the plate
boundary from the eastern edge of our survey to 91.5o W, so we can connect to the
western edge of the Christie/Sempere/Cochran surveys. This transit and sampling adds
only 2.5 days to the direct transit to Fremantle, while providing a good view of this
remote and unexplored portion of the ridge axis.
Our detailed cruise plan follows, based on assuming a steaming speed of 10 kts and an
average of 4.5 dredges per day and a two hour turnaround for wax core samples.
¥ "100%" survey along 110 km of seg F, all of segs G, H, I, J1, J2, and J3, with
10km line spacing (720km along-ridge), including doglegs, FZ offsets, and ten
80km-addons to make extra-long lines: 7440 km 17.2 days
¥ "50%" survey of J4 and 60km of seg K (210km along-axis), including doglegs and
FZ offset: 1100 km 2.5 days
¥ Collect 72 rock sample stations from "100%" survey: (10km along-axis spacing)
37 dredges = 8.2 days 35 wax cores = 2.9 days driving the length of axis = 1.7 days :
12.8 days
¥ Collect 11 samples from "50%" survey: (20km along-axis spacing) 6 dredges = 1.3 days
5 wax cores = 0.4 days driving the length of the axis = 0.5 days : 2.2 days
¥ Follow SEIR to E. end of seg. M (91.5 deg E) (2.5 days) and collect 6 dredges
(2 dredges per segment (1.3 days) : 3.8 days
Contingency plans if we fall behind in our schedule, we will first cut out some of
the extra length lines, saving those on the ASP platform itself given the lack of
data there; this will save 1 day. Next, we could eliminate all or part of the ridge
transit to 91oE, which will save up to 2.5 days. If we find weather makes dredging or
even mapping impossible in the southern part, we can go back farther north and sample
fracture zones, map more of the ASP platform looking perhaps for evidence of microplate
geometry (which is likely given the distortion of fracture zones), map more off-axis
features farther north, or map and sample the ASP hotspot trace farther north along
the St. Paul FZ.
Geochemical sampling As indicated above in the cruise plan, rock sampling will be
split ~50-50 between dredging and wax coring. Experience has shown that we can expect
to average 5-6 hours per dredge in the conditions likely within the study area, and
under ideal conditions, times could decrease to 3.5-5 hours per dredge. Samples recoveries
in axial dredges are typically large (50-200ækg). Wax coring recovers much smaller
samples sizes than dredging (5-50 g of volcanic glass), but this is offset by much
faster station times, generally 1-2 hours per site, and more precise sample location.
Johnson and Graham have extensive dredging experience, and they are joined by Scheirer
in having wax coring experience. Because of the alternating survey-sampling nature of
the program, two dredging shifts will generally be manageable. Depending on the conditions
of the sea and of the equipment, the balance of dredges to cores may be adjusted.
We plan to make preliminary petrologic descriptions based on lava morphologies,
weathering characteristics, and phenocryst abundances of rock samples while at sea.
We will separate, catalogue, and curate lithologic types for each dredge for shore-based
analysis. Samples will be loaded into lidded plastic buckets and stored in a van on
Melville during the cruise, and shipped to Hawaii from the port of disembarkation.
There, the collection will be completely described and catalogued, then subsampled by Johnson
and Graham for analytical work.
Fremantle - Port Hedland
Feb. 23 - April 14, 1996
*Fremantle AUS to Johnson Waypoint
*Start ÐÐ032 03.0' S 115 45.0' E
C 235.8 T 238.8 M ÐÐ035 06.7' S 110 00.0' E 341 nm
C 239.0 T 244.3 M ÐÐ039 20.8' S 100 00.0' E 540.6 nm
C 245.1 T 252.8 M ÐÐ042 05.0' S 091 05.0' E 437.2 nm
Great circle distance= 1318.9 nm
Rhumbline course 243 T
Distance 1325.5 nm
From Johnson2 Waypoint to Port Hedland AUS
*Start ÐÐ032 05.0' S 077 00.0' E
C 082.8 T 092.8 M ÐÐ031 43.4' S 080 00.0' E 154.3 nm
C 081.2 T 087.1 M ÐÐ029 59.4' S 090 00.0' E 525.3 nm
C 076.0 T 077.8 M ÐÐ027 24.4' S 100 00.0' E 548.4 nm
C 071.2 T 068.9 M ÐÐ023 56.8' S 110 00.0' E 579 nm
C 066.9 T 060.5 M ÐÐ020 17.0' S 118 34.0' E 524.3 nm
Great circle distance= 2331.3 nm
Rhumbline course 72.4 T
Distance 2347.4 nm
Total great circle miles for journey= 3650.20
Total rhumbline miles for journey= 3672.9
Total Sea Days 51.66
Total N-Miles
Transit Speed/Knots 11.5
Miles/day
Transit Days 13.22
Suvery days (SeaBeam @ 10kts and Dredging) 38.44
Total days charged 59
Internet: shipsked@ucsd.edu
WWW: http://sio.ucsd.edu/
shipsked@ucsd.edu