Voyage Plans and Summaries

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Franklin Voyage Plan No. FR03/2001

Title

Geoscience studies on the Southeast Australian continental slope and shelf: rift and drift sedimentation, and palaeo-oceanography.

Itinerary

Leg 1:
Depart: Hobart 1000hrs, Wednesday 21 March 2001 for seismic survey
Arrive: Hobart 0900hrs, Tuesday 27 March to change equipment and scientific contingent

Leg 2:
Depart: Hobart 1700hrs, Tuesday 27 March for sampling program
Arrive: Hobart 1000hrs, Tuesday 10 April 2001

Principal Investigators

Dr Neville Exon (Chief Scientist)
Senior Principal Research Scientist
AGSO
PO Box 378
Canberra 2601
Tel: (wk) 02 6249 9347, (h) 02 6288 2034. Fax: 02 6249 9920
Neville.Exon@agso.gov.au

Mr Peter Hill, AGSO

Professor Jock Keene, Division of Geology and Geophysics, University of Sydney

Dr Stephen Gallagher, School of Earth Science, University of Melbourne*

Dr William Howard, Antarctic Cooperative Research Centre, Hobart*

* will not be aboard ship

Scientific objectives

The aim of the study is to increase our knowledge of what happened to the region geologically over the last 100 million years, with special emphasis on sedimentation and oceanographic changes during 1) Cretaceous rifting, and 2) Gondwanan drifting apart in the Cretaceous and Cainozoic. The four major activities are designed to fill important gaps in the geoscience knowledge of southeastern Australia by:

a) helping to characterise the pre-breakup Late Jurassic and Cretaceous strata (160-65 million years ago) off eastern Tasmania (Exon and Hill);

b) documenting the sedimentary history of Late Cretaceous and Early Tertiary continental breakup (95-45 m.y. ago) in deep water off eastern Tasmania and in the Otway Basin (Exon and Hill);

c) elucidating the changes through time in carbonate deposition in the eastern Otway Basin from Oligocene times to the present day (Gallagher); and

d) studying Late Quaternary palaeo-environments off eastern Tasmania and in the Bass Basin (last 500,000 years) (Keene, Howard, Harris).

Cruise objectives

The methods employed will be seismic profiling, coring and dredging from the towing winch, and grab sampling from the hydrowinch, with seabed sampling predominant. The seabed of much of the area has been mapped in detail by AGSO, largely using multibeam sonar surveying and allowing precise definition of sampling targets. We plan to take piston cores, and some short gravity cores of harder outcrops. We will also dredge older outcrops and grab sample surface sediments as appropriate.

An overview map of our plans is given in Figure 1, with more detailed maps being provided for the east Tasmanian margin (Figure 2), the Bass Basin (Figure 3) and the Otway Basin (Figure 4). Some 1320 km of airgun seismic profiling is planned. We aim to take about 45 grabs, 35 gravity and piston cores, and 15 dredge hauls during the program. The cruise time of 20 days will include 2 straight transit days (off King Island to Hobart).

The cruise will be split into five parts

• 21-27 March, seismic survey off east Tasmania
• 27 March to 2 April, coring, dredging and grabs off east Tasmania
• 3-4 April, current meter deployment, grabs and coring in Bass Strait
• 4-8 April, coring, dredging and grabs in Otway Basin off Portland
• 8-10 April, transit to Hobart and retrieve current meter

Figures 1-4 show an indicative cruise track and sampling stations.

Dredge and grab material will be described, sampled and packed aboard ship. An AGSO saw will be used to cut rock slabs, and a binocular microscope will be used for examination. The cores in their liners will be cut to 1 m lengths, will be run through a device designed to measure magnetic susceptibility if time allows, and stored undisturbed in a small hired cool facility on deck.

Cruise Track

See Figures 1-4; Tables 1-4

Seismic survey: The vessel will depart Hobart on 21 March for the first phase of the work, the seismic survey off eastern Tasmania which will involve 1320 km (725 nm) of seismic reflection profiling, to be run at 6 knots, and to take approximately 6 days (Figure 2, Table 1). The AGSO system used includes 2 GI airguns, a compressor requiring approximately 500 litres of diesel per day, and a seismic cable 600 m long with 24 channels, recorded digitally. In addition a magnetometer will be towed. The seismic profiling will start 80 km southeast of Hobart and end off St Helens. On part of the transit of about 20 hours back to Hobart at 10 knots, depressors will be added to the airguns and we will experiment with running the seismic system at high speed, as a test for FR09/2001.

East Tasmanian sampling: Using pre-determined locations (Figure 2, Table 2) and new locations defined by the new seismic data, sampling will be carried out at about 12 dredge stations, 19 core stations and 8 grab stations. The core stations will be in water as deep as 4000 m, and dredge stations as deep as 3500 m, whereas the grabs will be on the outer continental shelf (<300 m) on transits or near other inboard stations. The sampling will be done in a zig-zag pattern, starting southeast of Hobart and finishing east of Banks Strait.

Bass Strait stations: Initially a current meter will be moored north of Flinders Island (Figure 3, Table 3). Then 10 grab samples will be taken south of the mooring, before retrieving the current meter. Finally two 9m-long piston corers will be deployed in central Bass Strait. Water depths will not exceed 100 m.

Otway Basin sampling: 26 grabs will be taken on the shelf and upper slope in water depths of less than 1000 m, up to 13 piston cores in water depths of 500-3300 m, and two dredges in water shallower than 2500 m (Figure 4, Table 4).

Time estimates

* Note: these sampling times include transits within the areas

Equipment

User equipment

• Seismic system: compressor in container, 2 GI airguns, winch, streamer, recorders
• Plotters for seismic profiles and sampling locations
• Magnetometer and towing winch
• Magnetic susceptibility measuring device
• Seismic processing work station
• Piston and gravity corers
• Dredges
• Smith-McIntyre grab
• Current meter
• Microscopes
• Rock saw
• Small cool container for cores
• Scientific PCs

Franklin equipment

• All winches, deck crane and deck machinery
• Coring cradle
• All laboratories
• GPS
• Scientific echosounder (12 kHz)
• Smith-McIntyre grab
• 12 kHz pinger
• TrackPlot software
• Fridge and freezers

Special Requests

• Room for standard size compressor container on rear deck
• Room for mini-container with sampling gear
• Room for large seismic winch on rear deck
• Room for smaller magnetometer winch at suitable location
• Room for small cool container on upper deck
• 240 volt power to rear deck
• Diesel fuel line for AGSO compressor, for seismic system.
• 3000 litres of diesel fuel to run compressor
• Prior checking and calibration of winch wire-out and tension meter
• Space in dry lab to set up seismic recorders
• Biological container on rear deck as sedimentology lab
• Room for rock saw in wet lab
• Room for microscopes in chemical lab
• Video monitor of stern block giving side view of wire (AGSO to install)
• Franklin data sets
• Navigation, with digital acquisition
• Bathymetry, with digital acquisition (12 kHz)
• Plots of ship tracks at various scales if possible

Personnel list

Geophysical — Leg 1

Neville Exon, AGSO, Chief Scientist, Geology
Peter Hill, AGSO, Geophysics
Steve Thomas , AGSO, Electronics technician
Ken Elphick, AGSO, Mechanical technician
Craig Wintle, AGSO, Mechanical technician
Jon Stratton, AGSO, Geological technician
Lyndon O’Grady, AGSO, Geological technician
Rick Smith, AGSO, GIS expert
Ron Plaschke, CSIRO Marine Research, Cruise Manager
Lindsay MacDonald, CSIRO Marine Research, Electronics
Bernadette Heaney, CSIRO Marine Research, Computing

Geological — Leg 2

Neville Exon, AGSO, Chief Scientist, Geology
Jock Keene, Sydney University, Sedimentologist
Peter Hill, AGSO, Geophysics
Peter Harris, AGSO, Sedimentologist
Andrew Heap, AGSO, Sedimentologist
Andrea Leach, Melbourne University, Foraminiferal micropalaeontologist
Jon Stratton, AGSO, Geological technician
Lyndon O’Grady, AGSO, Geological technician
Dave Mitchell, Sydney University, Geological technician
Ron Plaschke, CSIRO Marine Research, Cruise Manager
Lindsay MacDonald, CSIRO Marine Research, Electronics
Bernadette Heaney, CSIRO Marine Research, Computing

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

Ron Plaschke
Acting Ships Manager
CSIRO Marine Research

Figure 1. Overview plan of cruise FR03/2001. A 6-day seismic survey (thick lines) off eastern Tasmania will be followed by a geological sampling program (dotted lines) off eastern Tasmania, in Bass Strait and on the Otway margin. The primary sampling sites are shown (cores = solid circles, dredges = triangles, grabs = diamonds).

Figure 2. Detail of the proposed seismic and sampling program off eastern Tasmania (symbols as in Figure 1). 

Figure 3. Detail of the proposed sampling program in Bass Strait (symbols as in Figure 1).

Figure 4. Detail of the proposed geological sampling program on the Otway margin (symbols as in Figure 1).

Table 1. Details of proposed seismic lines off east Tasmania

Total length = 1321 km (713 nm)

@ 6 kts, survey time on line = 4 days 22.8 hrs

Time in turns between lines = 4 hrs

@10 kts, Hobart to start of first line = 4 hrs

@10 kts, end of last line to Hobart = 16 hrs

(i.e. total transit time = 20 hrs)

Total time Hobart to Hobart = 6 days 0 hrs (assuming seismic gear fully operational at startup).

Table 2. Geological sampling sites (cores and dredges) off east Tasmania

D = dredge
Cs = short core
Cl = long core

Table 3. Bass Strait sampling stations

CM = current meter
G = grab
Cl = 9m corer

Table 4. Deep-water geological sampling sites on the Otway margin

D = dredge
Cs = short core

Updated: 31/01/03