Voyage Plans and Summaries

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Franklin Voyage Plan No. FR07/2001

Title

The palaeoclimatic history of the New Caledonia region - closing the gap between the deep-sea and the coral records

Itinerary

Depart Brisbane 1000 hrs, Wednesday 29 August 2001
Arrive Noumea 1000 hrs, Tuesday 4 September 2001

Principal Investigator

Dr Patrick De Deckker (Chief Scientist)
The Australian National University
Dept. of Geology, Australian National University, Canberra ACT 0200
Phone: 02- 6125 2070/2056; Fax: 02- 6125 5544
e-mail: patrick.dedeckker@anu.edu.au

Scientific Objectives

1. To obtain a number of sediment cores from offshore Amedee Island and another adjacent site to document a continuous record of oceanic changes, both at the surface and on the sea floor at different water depths. We anticipate that, with the coring equipment we propose to use, we will obtain a continuous record of environmental change spanning at least the last 150,000 years, thus covering two periods of sea-level high and two glacials.

2. To carry out intensive analyses on horizons in the cores that correspond to the periods of sea-level highs when the corals recovered in the Amedee Island core would have been growing. Chemical analyses on open-ocean organisms such as foraminifers would provide an ideal comparison against the chemical signals obtained from the Amedee corals. Such calibration has rarely been achieved anywhere in the world!

3. To carry out a great variety of analyses on the oceanic cores to determine environmental conditions through time. We want to analyse pollen from the cores to determine vegetational changes on New Caledonia. In addition, we would want to study the supply of terrigenous material such as clays from New Caledonia to determine periods of erosion and land stabilisation in New Caledonia and link those to climatic change. This is to be paralleled with the vegetation record. Finally, those data would then be compared with conditions at sea through the study of marine microfossils such as formainifers, nanoplankton and benthic ostracods. The chemical signals in some of those microfossils would be used to further determine conditions in the oceans such as temperature and salinity.

Cruise Objectives

It has been agreed that the Franklin would leave Brisbane with only the 4 Australian scientist contingent and that the vessel would directly head for Noumea to get customs clearance and also pick up the French scientific contingent. During the transit between Brisbane and Noumea, surface water samples and plankton tows would be made as anticipated in the original cruise proposal.

Once the customs formalities are completed and the 4 French scientists are collected, we will proceed to the first site and CTD and coring operations are to proceed. Originally, we had planned 2 coring and CTD transects, but upon accessibility of the recently made bathymetric maps [provided through the courtesy of S.M.A.I., Noumea], we decided to conduct only one transect in an area slightly further south where we now anticipate recovering a suitable set of cores. This area apparently does not yield any underwater canyons as seen in the vicinity of the Boulari and Dumbea palaeochannels originally illustrated in the cruise proposal.

Nine coring sites are proposed along one transect going from 3,700 m to 550 m. One alternate site is proposed some 20 NM further south [see Figure 2].

One additional site is also proposed and is located at 35 m water depth inside the "Lagon". This site was not mentioned in the original cruise proposal, but during discussions held in Noumea, we discovered that this shallow-water site has the potential to recover sediments deposited during the period of low sea level preceding 10,000 years ago. This site has the potential to yield a record of the vegetation history of the Main Island.

Cruise Track

1. Brisbane to Noumea: estimated travel time 80 hours. See Figure 1.

We would wish to collect water samples and take surface plankton tows [over a 10 minute period at each location] every 100 km during the transit between Brisbane and Noumea.

2. Arrival in Noumea: to obtain customs clearance for cruise FR7/2001 and FR8/2001 and for French scientific personnel to board the ship. Time anticipated: unknown at this stage. However we assume that we will have to arrive during daytime. If we are to reach New Caledonian coastal waters during night time, I propose to proceed directly to coring site 1 [23° S, 165° 13’E], take a CTD down to 3,700 m, and if this allowed by French authorities and also if time permits, also take a gravity core at that site before going into harbour in Noumea for customs clearance. The reason for going to the first coring site during the night is explained below.

At present, we are unaware of the location of the oxygen minimum zone [OMZ] in the vicinity of New Caledonia and to identify this horizon is vital to identify the exact depth of some of the cores. As indicated in our original cruise proposal, we would wish to target coring sites above, at and below the OMZ as we believe that it is in this region of the sea floor that laminated sediments are likely to be recovered. It will take some time for the CSIRO chemist to confirm through proper chemical analyses the position of the OMZ, to be detected with the oxygen probe on the CTD.

The most suitable location to enter the ‘Lagon’ is through the Boulari Pass, and this explains the apparent detour in the transit between stations 9 and 10.

3. Gravity coring and CTD profiles offshore New Caledonia but in the French EEZ:

Nine sites have been chosen and these are located on the attached Figure 2. The location of these sites, water depth and respective time to take the core and perform the CTD profiling are also listed in Table 1. Note that little transit travel time will exist between each site. We anticipate that the commencement of the coring at any site, except for the first one, will be determined by the time spent to extrude the core from the corer and to reload it for the next coring procedure. It is more than likely that the CTD profiling at each site will precede the coring to allow sufficient time to reload the corer.

Note that one additional coring and CTD station has been selected in case any of the other sites does not return a suitable core. This station is located at 23° 20’S, 166° 13’E.

4. One gravity core to be taken inside ‘Le Lagon’ in a 35 m deep depression NW of the Ile Ouen in close vicinity of Noumea [see Figure 2; 22° 24'S, 160° 43'E]. This operation is likely to be very rapid because of the shallow water depth. If this site is proving unsuccessful, an alternate site at 23 m water depth has been chosen [see Figure 2; 22° 27'S, 160° 39'E]. No CTD is to be taken at this site.

Time Estimates:

See Table 1.

Piggy-back Projects: None

Franklin Equipment

We require the 24 bottle rosette, and access to the winch to deploy the gravity corer.

We require access to the container laboratory to prepare coring equipment, cut cores etc. We also intend using this laboratory space for filtering our own water samples and to process plankton tow samples.

It is primordial that the oxygen sensor attached to the CTD is functional and calibrated as we will need to determine correct oxygen profiles in the New Caledonia sector. [On previous cruises led by De Deckker, this sensor was faulty].

We require the gravity core trolley to deploy the gravity corer.

User Equipment

We will bring all the necessary equipment to perform gravity coring. All this material will be on loan from the Australian Geological Survey Organisation. The corer will also be insured in case of loss or damage.

We will also bring a plankton net and the necessary filtering equipment to filter water.

Participants

Patrick De Deckker, Chief Scientist, ANU
Franz Gingele, Visiting Fellow, ANU
Elsie Gretton, Honours student, Geology, ANU
TBA, Student, ANU
TBA, Student, ANU
Thierry Correge, Deputy cruise leader, Noumea
Guy Cabioch, Deputy cruise leader, Noumea
Anne-Marie Semah, Bondy, France
Denis Wirrmann, Bondy, France
Bob Beattie, Cruise Manager/Computing, CSIRO ORV
Gary Critchley, Hydrochemistry, CSIRO ORV
Lindsay MacDonald, Electronics, CSIRO ORV

This cruise plan is in accordance with the directions of the National Facility Steering Committee for the Research Vessel Franklin.

John Wallace
Ships Manager

Figure 2: FR07/2001 Gravity core and CTD Sites.

Table 1: Estimated station and transit times.

Updated: 31/01/03