Voyage Plans and Summaries

[back to voyage document index]

Franklin Voyage Plan No. FR01/2002

Title

Cross-shelf sediment transport in the Torres Strait, Gulf of Papua region.

Itinerary - Note changed departure port and changed arrival date

Depart Brisbane 1000 hrs, Thursday 17 January 2002
Arrive Cairns 1000 hrs, Saturday, 9 February 2002

Principal Investigators

Dr Peter Harris (Chief Scientist)
Principal Research Scientist
Australian Geological Survey Organisation (AGSO) – Geoscience Australia
University of Tasmania
PO Box 252-80
Hobart, TAS 7001
Tel: (03) 6226-2504 (wk); (03) 6223-3989 (hm); Fax: (03) 6226-2973

Dr Michael Hughes
University of Sydney

Scientific Objectives

A zone of high tidal current energy across the northern margin of the Great Barrier Reef is hypothesised to be a cross-shelf corridor of sediment movement. It is proposed to conduct high resolution seabed mapping at strategic locations in conjunction with seabed sampling and photography to identify mobile bed sediments and depositional end-members of the transport system. Key goals are to collect sufficient data to verify whether such cross-shelf transport is occurring, to document benthic biological communities associated with different substrate types and to collect sediment cores to extract a time series of cross-shelf terrigenous flux. The research is of relevance to environmental managers who require knowledge of the processes governing sediment dispersal and the distribution of biota in this environmentaly sensitive and economically important geographic location.

Cruise Objectives

The methods employed will be swath mapping, shallow high-resolution seismic surveying, suspended sediment sampling, current metering, coring and grab sampling. Three areas will be mapped using a high-resolution swath mapper and Chirp shallow seismic system. We plan to take shallow gravity cores and surface sediment grab samples, deploy the Franklin’s CTD-turbidity meter, collect water samples, and deploy and underwater camera. One current meter instrument frame will be deployed to measure sediment flux in Area "A".

Area "A" is located adjacent to the seaward margin of the Fly River Delta. It is a fairly flat seabed, but previous sonar surveys have indicated the presence of subtidal bedforms in the area. Hence it is an area of active bedload transport. Area "B" is located amongst the northernmost reefs of the Great Barrier, where a 100m deep submarine valley crosses the shelf. This valley is the low sea level river channel of the Fly River and it is of interest to determine whether it remains an active sediment transport conduit at the present time. Area "C" is located at the seaward terminus of the palaeo Fly River channel, and should be the locus of low sea level sediment deposition. Sonar data show this area is characterised by low sea level (drowned) reefs, Halimeda biostromes and possible gas escape features (pockmarks) on the seabed.

Cruise Track

Time Estimates

The general region of the proposed survey is the northern margin of the Great Barrier Reef and Fly River Delta. A current meter mooring will be deployed in area "A" at the start of the survey. The proposed tracks (not shown) are about 10km in length, and their spacing will vary depending on the water depth. Track orientation is illustrated by the position of the survey boxes in the location map (above). Allowing for some ~50% maximum overlap of the swath bathymetry, and assuming a swath range of 7.4 times the water depth, the line spacing will need to be about 75m for area "A" where the depth range is 20 to 30 m. Given a survey speed of 5 knots we can run about 66 x 10km length lines in about 3 days. Area "A" is thus 10 km by ~5 km, and centred on the position:9° 7.4’S, 143° 43’E

On completion of the survey, we will select 20 stations based on the survey results for the collection of grab sediment samples, seabed photography and CTD deployment. At ~10 of these stations a piston core will also be taken. Allowing for 2.4 hours per station, we will complete work in area "A" in 5 days.

For area "B" the water depth is 40 to 70 m and hence the required line spacing is 250m. We propose to run 66 x 10 km length lines in about 3 days. Area "B" is thus about 10 km by 10 km, and centred on the position:9° 27.5’S, 143° 59’E. A further 20 stations will be occupied, with the same sampling procedure as above.

For area "C" the water depth is 60 to 100 m and hence the required line spacing is 250m. We propose to run 66 x 10 km length lines in about 3 days. Area "C" is thus about 10 km by 10 km, and centred on the position:9° 30’S, 144° 22.5’E. A further 20 stations will be occupied, with the same sampling procedure as above.

On completion of work in area "C" we will return to area "A" to collect our current meter.

Franklin Equipment

• All winches, deck crane and deck machinery

• Coring cradle

• All laboratories

• GPS, scientific echosounder (12 kHz), Smith-McIntyre grab,12 kHz pinger

• Track Plot Software, fridge and freezers

• CTD, 12 Niskin bottles with transmissometer

User Equipment

• RESON swath mapping system and associated computing equipment (JCU)

• CHIRP shallow seismic system and associated computing equipment (JCU)

• Piston and gravity corers, dredges, Smith-McIntyre grab

• Current meter frame, underwater camera, microscopes

• Small cool container for cores

• Scientific PC’s

Special Requests

• Room for small cool container on upper deck for cores

• 240 volt power to rear deck

• Prior checking and calibration of winch wire-out and tension meter

• Space in dry lab to set up seismic recorders and PC’s

• Shipping container on rear deck as sedimentology lab

• Room for microscopes in chemical lab

Franklin Data Sets

• Navigation, with digital acquisition

• Bathymetry, with digital acquisition (12 kHz)

• Plots of ship tracks at various scales

Personnel List

Peter Harris, AGSO, Chief Scientist, Sedimentology
Michael Hughes, Sydney University, Sedimentologist
Andrew Heap, AGSO, Sedimentologist
Vicki Passlow, AGSO, Sedimentologist/Palaeontologist
Rick Smith, AGSO, GIS technician
Kevin Hooper, JCU, Electrical/scientific technician
Robin Beaman, Uni. of Tasmania, PhD Student
Mark Hemer, Uni. of Tasmania, PhD Student
Jon Stratton, AGSO, Geological technician
Lyndon O’Grady, AGSO, Geological technician
TBA, CMR, Electronics
TBA, CMR, Computing

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

John Wallace
Ships Manager

Updated: 31/01/03