UNESCO-IOC TTR-9 Cruise
in the Alboran sea

R/V Professor Logachev, 17 July – 27 July 1999

This short report is about the 3rd Leg of the 9th Training-Through-Research Cruise.
By: R. Koelewijn, this page is optimized for 800x600 resolution.

Chief staff scientist Alexey Krotov

Co-Chief scientist Menchu Comas (Granada university, Spain)

Co-chief scientist Michael Ivanov (Moscow University, Russia)

This is the Professor Logachev in the Spanish harbor city of Cadiz one day before departure. It's a russian ship and has a length of 105 meters. It is specially designed for research at sea and has been used before in earlier TTR cruises (go to: Ship specifications page).
We left the harbor at the end of the day and the weather was excellent and stayed this way the whole cruise. Our first location was off the coast of Marroco where mud diapirs where discovered during an earlier cruise. The objectives were planned to be met by the following successive surveys:
- reconnaissance based on OKEAN long range side scan sonar records and high resolution seismic.
- more detailed investigation by OREtech deep towed side scan sonar. Under water t.v. recording and photographing.
sampling of the ocean floor by :
- dredging and grabbing hard rock outcrops
- coring overlaying soft sediments

The area was surveyed with the OKEAN long-range sidescan sonar accompanied by high resolution seismic reflection profiling. The spacing of the seismic profiling was taken in a way that provided overlapping of the OKEAN sonographs. The OKEAN records are most useful when used with the seismic records and 3,5 kHz echo-sounder records because the observed backscatter variations make most sense in this context. The area surveyed was not particularly deep, with a gentle slope towards the north-northeast, and most of the area was draped with a uniform sedimentation that provides a relatively uniform backscatter. The deviations from this background level of backscatter are important.
Artifacts on two of the short connecting lines (track-parallel striping on the starboard side of line PS-171, similar problems on the port side of PS-173) limit the usefulness of these lines but the rest of the data  compensated for this.

Features of the OKEAN:

swath width  : 30.000 m.
working depth : 1000-8000 m.
towing depth  : 50-100 m.
towing speed  : 2 - 8 kts
working frequency : 9 - 10 kHz
tape recording
digital processing
weight in air  : 1200 kg. (fish)
  : 700 kg. (depressor)
length  : 5.6 m. (fish)
  : 1.4 m. (depressor)
input power  : 10 kWh
 
 

Also the OREtech medium/short range deep-towed sidescan sonar was used accompanied by a hull mounted acoustic sub-bottom profiler.

Features of system used for seismic acquisition

Source : 1.5 l airgun
 pressure  : 120 atm.
 towing depth  : 1.5 m.
 shotpoint interval : 10 s.

Receiver : Hydrophone streamer
 offset  : 150 meter
 working depth : 1.5 meter
 used channels : 1

Processing : Minimal
 spherical divergence
 exponential gain : 5
 B.P.F.  : 30, 70, 150, 200

The picture to the right shows the airgun on the deck The velocity of the ship during seismic acquisition was 5.5 knt.  One knt = 1.8 km. So 5.5 knt  = 9.9 km/hour = 2.75 m/s this means that the shotpoint interval = 10s.= 27.5 m. (distance between shots).
 
 

At selected sites, some gravity cores were taken. Also very important was the use of a camera guided grab. The grab had a camera that looked downward from between the grabbers. In this way you can see exactly what you grabbed. This particular grab was capable of taking 2 tons of samples up to the surface. Unfortunately the first time we used the grab was the last time...
This was really a dramatic part of the cruise since a lot of work was based on the use of this grab. The whole thing was recorded on video:
 

At this moment the grab comes safely out of the water and nothing strange was happening.	It splashed back in the water a couple of times because of the movement of the ship.
Then suddenly the cable snapped at the point where it was fixed to the grab.	And the (rather expensive) instrument was forever lost to the sea.

This unfortunately event was not only a big blow to the spanish Basacalb team but also for the people of the following leg. They had planned to use the grab even more.
The importance of this device and the cost of it made the russian captain decide to spend a day searching for the instrument with the use of a custom made dredge, and when found try to recover it. The dredge had no camera and the grab was lost at a location where the sea was about 800 meters depth. So chances where very little of even finding the grab. Surprisingly though, the grab was found! But it seemed to have impacted the bottom with quite a velocity cause it was totally buried in the sediment. This meant that there was little chance of pulling it loose, the weight would simply be too large.

Three of these welded hooks where attached to the yellow frame by cables. The frame was attached to a weight (visible on the left of the photograph) to keep it on the bottom. This whole construction was then towed behind the ship hoping it would hook up with the grab.

Luckily the gravity coring went well and even showed some interesting information, some of the diapirs turned out to be mud volcanoes. This method of sampling takes little time. A long pipe is lowered into the water and is then dropped to the sea floor. Its speed together with some weights added on top, drives the pipe into the sediment. The pipe is then pulled back onboard and has to be emptied, which is done by hand and takes quite a few hands to get the job done. The picture below shows how much effort is needed to push the core out of the pipe (the core was in this case  only 1.3 meter long!).

Push!! Nine people are pushing here, sometimes it took even more!!

Here the first gravity core is back on board. Scientists are gathering around to sniff the smell of the mud and bury their hands in it. The man with the white beard is John Woodside from Canada, the man in front of him with the same blue T-shirt is Dr. Ivanov from Russia. Both of them have been very active with all the earlier TTR cruises organizing them and taking part in them. The woman with the coffee mug standing in front of them  is Joan Gardner from the U.S Naval research Lab. She had been on the leg before this one in the Gulf of Cadiz. The five persons standing behind Woodside and Ivanov are all Russian students from the Moscow state university. They were all very actively involved in all the parts of the cruise and deserve a thank you.
Part of the gravity core is visible in this picture, the pipe is lying on its side and the person bending over is looking at the lower end of it.
 
 
 
 

After spending too much time at the mud diapir provence Menchu Comas decided to skip the planned survey along the Algerian coast where we wanted to look at the Habibas escarpment. The most important objective of this cruise was seismic acquisition along the Southeastern Spanish coast. Here the sea bottom is crosscut by Miocene structures for example the Palomares fault and the Cartagena escarpment. On the way to this location though we used a dredge to collect metamorphic rock samples from some selected hardrock outcrops.

This is a picture of the interpretation room. From front to back these are Juan Manuel Fernandez Soler from the Grenada university, Irene Zeldenrust from the free university of Amsterdam and Guillermo Booth also from the university of Grenada. As you can see things are going well or they are having fun, cause they have big smiles on their faces!