/V Melville 3/4/05

The R/V Melville is currently at 43 deg 20 min S, 136 deg 38 min W, heading
northwest.  We are surveying potential drillsites for an IOD P drilling leg to
study the Southern Ocean during Eocene extreme warmth conditions, and during the
Eocene/Oligocene transition to contin ental ice sheets on Antarctica.  We have
surveyed 6 of the 12 potential drill sites, mostly near 50 degrees S. These
sites were arrayed between 65 degrees S and 55 degrees S in the Eocene.  Today
we will survey the 7th site (SP-5A) on 56 million year old crust, and will a lso
piston core it tomorrow.  Surveys consist of seismic reflection, seabeam, and
magnetics data acquisition.  We are taking 50 foot pis ton cores, after having
lost one piston core last week after the wire parted while it was stuck in the
bottom.

Mitch Lyle


Report for R/V Melville, 20 March 2005 (21 March 05)

The R/V Melville returns to Papeete  on Monday March 21, after a successful site
survey for an IODP drilling program.  The objectives of the cruise were to
identify drill sites to study high latitude South Pacific oceanography during
the period of Eocene extreme warmth. I n addition, we collected sediments to
study Quaternary frontal movement and biogeochemical cycles.

The site-survey cruise was conducted February 9 to March 21, 2005 aboard the R/V
Melville, a cruise that described a southerly loop from Tahiti to the working
areas along 50 S and back. The region thus surveyed covered the eastern half of
the Southwest Pacific Basin, a ve ry poorly known part of the world's ocean.
During the course of our two weeks of work along 50 south we experienced some of
the weather the region is famous for but were able to complete all the surveys
(one was slightly smaller in area because of the arrival of Cyclone O laf) and
raise the best new cores from the region in the past 30 years.

Highlights of the cruise include 7500 nautical miles (13,900 km) of swath-map
trackline, resulting in a surveyed area of 167,000 sq km. For over half this
trackline we also acquired seismic reflection to study sedimentation in the
South Pacific. We surveyed 12 areas as po tential sites for drilling. Of these,
four between 31 and 39 S between 133 and 143 W had no discernable sediment. This
discovery of at l east a million square kilometers of Paleogene-aged bare sea
floor is new and exciting, but not conducive to eventual scientific ocean dr
illing. Our best results occurred along the southern extent of the cruise, and
will provide a foundation for our revised drilling propos al.

The piston cores we recovered from high southern latitudes indicate that we will
be able to address three important scientific questions in addition to those
posed in our drilling proposal. We are able to demonstrate that the modern CCD
at 50 S is at about 4750 meters, so for much of its history the crust in the
region has been above the CCD permitting paleoceanographic reconstructions based
on both calca reous and siliceous microfossils. Two of our cores recovered
calcareous sediment both above and below pelagic clay, suggesting that the CCD
has changed dramatically, and the changes will be recorded in the sediments.  At
Site SP 1-A we raised a core of siliceous ooze and silt. As this site at 51.5 S
is well south of the modern ice-berg limit, we assume the silt, and the basalt
pebble found on the surface of sediment recovered at 46S, represents ice rafting
from Antarctica. Thus we anticipate a complete Antarctic ice rafting record
might b e available in these sediments. Since the more southerly sites backtrack
to 59 to 66 S, the exact latitude of the Drake Passage, the iss ues concerning
the development of this critical gateway should be approachable with the results
of drilling at those locations.

Regards, Mitch Lyle and Dave Rea co-chief scientists


R/V Melville Weekly Science Report 3/4/05 - The R/V Melville is 
>currently at 43 deg 20 min S, 136 deg 38 min W, heading northwest. We are
>surveying potential drillsites for an IODP drilling leg to study the Southern
>Ocean during Eocene extreme warmth conditions, and during the Eocene/Oligocene
>transition to continental ice sheets on Antarctica.  We have surveyed 6 of the
>12 potential drill sites, mostly near 50 degrees S. These sites were arrayed
>between 65 degrees S and 55 degrees S in the Eocene.  Today we will survey the
>7th site (SP-5A) on 56 million year old crust, and will also piston core it
>tomorrow.  Surveys consist of seismic reflection, seabeam, and magnetics data
>acquisition.  We are taking 50 foot piston cores, after having lost one piston
>core last week after the wire parted while it was stuck in the bottom.

R/V Melville - Mitch Lyle - Final Report - The R/V Melville returns to Papeete 
on Monday March 21, after a successful site survey for an IODP drilling program.
 The objectives of the cruise were to identify drill sites to study high
latitude South Pacific oceanography during the period of Eocene extreme warmth.
In addition, we collected sediments to study Quaternary frontal movement and
biogeochemical cycles. The site-survey cruise was conducted February 9 to March
21, 2005 aboard the R/V Melville, a cruise that described a southerly loop from
Tahiti to the working areas along 50°S and back. The region thus surveyed
covered the eastern half of the Southwest Pacific Basin, a very poorly known
part of the world's ocean. During the course of our two weeks of work along 50°
south we experienced some of the weather the region is famous for but were able
to complete all the surveys (one was slightly smaller in area because of the
arrival of Cyclone Olaf) and raise the best new cores from the region in the
past 30 years. Highlights of the cruise include 7500 nautical miles (13,900 km)
of swath-map trackline, resulting in a surveyed area of 167,000 sq km. For over
half this trackline we also acquired seismic reflection to study sedimentation
in the South Pacific. We surveyed 12 areas as potential sites for drilling. Of
these, four between 31° and 39°S between 133 and 143° W had no discernable
sediment. This discovery of at least a million square kilometers of
Paleogene-aged bare sea floor is new and exciting, but not conducive to eventual
scientific ocean drilling. Our best results occurred along the southern extent
of the cruise, and will provide a foundation for our revised drilling proposal.
The piston cores we recovered from high southern latitudes indicate that we will
be able to address three important scientific questions in addition to those
posed in our drilling proposal. We are able to demonstrate that the modern CCD
at 50°S is at about 4750 meters, so for much of its history the crust in the
region has been above the CCD permitting paleoceanographic reconstructions based
on both calcareous and siliceous microfossils. Two of our cores recovered
calcareous sediment both above and below pelagic clay, suggesting that the CCD
has changed dramatically, and the changes will be recorded in the sediments.  At
Site SP 1-A we raised a core of siliceous ooze and silt. As this site at 51.5°S
is well south of the modern ice-berg limit, we assume the silt, and the basalt
pebble found on the surface of sediment recovered at 46°S, represents ice
rafting from Antarctica. Thus we anticipate a complete Antarctic ice rafting
record might be available in these sediments. Since the more southerly sites
backtrack to 59 to 66°S, the exact latitude of the Drake Passage, the issues
concerning the development of this critical gateway should be approachable with
the results of drilling at those locations.   (Mitch Lyle and Dave Rea, co chief
scientists)