MARINE SCIENTIFIC REPORTS
No. 5
Institut fiir Ostseeforschun g Warnemiinde
1993
"Meereswissenschaftliche Berichte" ermoglichen Mitarbeitern des Institutes fii r Ostseeforschung Warnemunde und verwandter Einrichtungen, in breiterem Umfang ihre Ergebnisse z u
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"MARINE SCIENTIFIC REPORTS" enables scientist s of the Institute of Baltic Se a Research Warnemunde and cognat e institutions to publish results in more detailed versions.
Volumes are published at irregular interval s and numbered consecutively.
Das diesem Bericht zugrund e liegend e Vorhaben wurde mit Mitteln des Bundesministers fiir Forschung und Technologi e unter dem Forderkennzeichen 03 R 423 A gefordert. Die
Verantwortung fii r den Inhalt dieser Veroffentlichung liegt bei den Autoren
The project, this report i s related to , was supported by the
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Meereswissenschaftliche Berichte
MARINE SCIENTIFI C REPORT S
No. 5 , * " •1994
o_ VraL-^ / 5 .
C r u i s e Repor t %'>< * ^/
RV "SONNE " C r u i s e S08 2 1992
S082A:
Geophysical investigations along the Reykjanes Ridge, North Atlantic
Balboa - Reykjavik, 29.09.-16.10.1992
S082B:
Sedimentation pattern of the Reykjanes Ridge, North Atlantic Reykjavik - Bremerhaven, 17.10.-31.10.1992
Edited by
R. Endler
1' and K.S. Lackschewitz
2' with contribution s of the cruise member s
^Institute of Baltic Sea Research Warnemiinde at the University of Rostock
2)
GEOMAR Research Cente r for Marine Geoscience s Christian Albrechts University at Kiel
1993
Cruise Report S082
Content
1. Introduction 2 2. Part I (S082A ) 3
2.1. Research program and cruise track 3 2.2. Participants 5
2.3. Cruise narrative - S082 A 6 2.4. Methods 9
2.5. First results 1 1
2.5.1. Subbottom profiling with the Parasoun d
System 1 1
2.5.2. Test of the sediment penetratin g
echosounder SEL 9 0 2 1
2.5.3. Episodic spreadin g at the Reykjanes
Ridge 2 5
3. Part II . (S082B ) 3 2
3.1. Research program and working are a 3 2
3.2. Participants 3 5
3.3. Cruise narrativ e S082 B 3 7
3.4. Methods 4 1
3.5. First results 4 3
3.5.1. Morphology an d sediment distribution . . 4 3
3.5.2. Sedimentology 4 7
3.5.3. Physica l properties of the sediments . . 5 2
3.5.4. Benthic studie s 5 6
4. Summary 5 8
5. Acknowledgements 5 9
6. References 5 9
1. Introduction
(R. Endler, K.S.Lackschewitz)
Since October 01 , 1991, the GEOMAR Marine Research Center Kiel, th e Institute o f Baltic Se a Research Warnemuende and the geological departmen t o f the University o f Greifswald perfor m investigations o f sedimentation processes o f i n the Mid
Atlantic Ridg e (MAR) , with special emphasis on the central part of the Reykjanes Ridge. This joint research project i s
supported by the "Federa l Minister fo r Research and
Technology". I t is closely connected t o the international Mid Ocean Ridge - research programs "Ridge " - USA, "Bridge " - UK and the new European "InterRidge " activity.
At th e beginning o f 1992 the possibility cam e up of using the research vessel "Sonne " for marine geological an d
geophysical investigation s within the framework of the MAR - project. RV "Sonne" , which i s one of the most advanced Germa n research vessels, offers good working conditions especiall y for the investigation o f the unregular se a bottom structure s and the small sedimen t ponds of the MOR regions.
The research cruise "Sonn e - 82" (S082 ) was planned t o start i n Balboa (Panama ) on September 29 , and to finish in Bremerhaven (Germany ) on October 31 , 1992. Because of the long transfer fro m Balboa t o the area of interest th e cruise was divided i n two parts.
The task of the firs t part (S082 A - transfer fro m Balboa, Panama, September, 29 to Reykjavik, Iceland , October, 16) was to carry out a methodic - geophysical progra m with the aim to adapt advanced acousti c subbotto m profiling system s of very high resolution t o the acoustically difficul t condition s i n the MAR area. In order to solve this task a new joint researc h project "Sedimentatio n i n the Reykjanes ridge : sediment -
echosounding" was established under the leadership of the
University o f Rostock (Prof . Wendt). Thi s program i s supported by the "Federa l Minister fo r Research and Technology". As a result o f this program th e advanced acoustic system s require d
for the complicated task s to be solved during part S082B would become available. Furthermore, using the multibeam echosounde r Hydrosweep, th e central part of the Mid Atlantic Ridge (MAR ) between 53° N and 61° N was planned t o be mapped i n order to
achieve informatio n on its tectonic histor y an d subdivision i n area of different developments.
The second part (S082B ) was to be focused on the
investigation o f sedimentation processes an d its spatial and temporal variability i n the central part of the Reykjanes Ridge near 59°N . The methods used includ e acoustic profiling, sediment samplin g and complex (sedimentological , geochemical, physical, biological) investigation s o f recovered samples . The results will be used to build a model of the genesis of the distributive province "Reykjane s Ridge".
Cruise Report S082
2. Par t I (S082A )
2.1. Research program and cruise trac k
(R.Endler, K.S.Lackschewitz )
The task of the first part of the cruise (S082A ) was to use the transfer fro m Balboa to Reykjavik fo r a small
methodical and geophysical program with the main aim to install and prepare the required acoustic equipmen t fo r the investigations durin g the second part of the cruise (S082B) . The program was divided int o two parts.
The firs t part was a survey of the central part of the MAR between 53° N and 61°N (see Fig. 2.1.-1) using the multi beam echosounder HYDROSWEEP. In close cooperation with the University of Hamburg, Institut e of Geophysics, (Prof . Weigel
7(fod
8Cf00' 70°QQ ' 60°00 ' ^OO ' 4tf00 ' 3CP00 ' ^OO ' IcTot f 0°00 ' 10°00 '
6000
50° 00'
S082-08
7(f00'
60°00'
50°00'
80°00' 70°00 ' e0°00 ' 50°00 ' 40°00 ' 30°00 ' 20°00 ' 1 0°00' 0°00 ' ^o t i
Fig.2.1.-1 Tracks and study area of cruise No. S082 (P i - 13 seismoacoustic lines , S082-8 samplin g statio n out of working area S082B)
this data will be used for the first interpretatio n of the tectonic history of the northern MAR.
The second part was to install and to test high resolution acoustic profiling system s required fo r the
investigation of the complicated morphology and sediment cove r of the Reykjanes Ridge during part B. The narrow beam
echosounder Parasoun d ofte n fail s to work properly i n regions with rough morphology of the sea bottom (MOR ) or at
continental margins. As the slope angle of the seafloor
exceeds th e acoustic beam angle of the echosounder, th e sound pulses are reflected away fro m the ship and therefore not properly receive d thu s the recordings become of poor quality.
Furthermore, the installation of the PARASOUND equipment at that time only permitted an on-line registration (black/white ) of the echo signals on a DES025 thermo-printe r omittin g th e registration of a large amount of acoustic information .
However, fo r sedimentological an d sedimentphysical studie s on the Reykjanes Ridge it was essential to record the complete information of the echo signals digitally, so that after postprocessing th e spatially smal l and strongly organize d
sedimentary structure s coul d be resolved and separated. Thes e data is meant t o be added to a complex sedimentologica l / sediment - physical model of MOR.
It was therefore decided to install and connect the
"PARAsound DIGitalisierungs und Mehrkanal Auswertung" - System (PARADIGMA) to the PARASOUND - echosounder in order to test the integrated syste m i n MOR regions. Furthermore, it was planned to integrate the PARASOUND - PARADIGMA system , developed by Dr.V. SpieS (Univ . Bremen), int o the basic research equipment of RV "Sonne" later on. The aim of this work was to get the narrow beam echoes (no n demodulated, lo w
frequency signal ) digitized an d stored on tape for
postprocessing. Thes e data would specificall y be used fo r a detailed investigatio n of small sediment-pond s with rathe r even surfaces during part S082B.
A new deep-sea version of the multi-frequency sedimen t echosounder SEL 9 0, developed by Prof. Wendt, University of Rostock, was also planned t o be installed, tested and prepared
for profiling during th e second part of the cruise S082B. This computer controlle d subbotto m profiler ca n operate with
acoustic pulses of the frequencies of 5 kHz, 10 kHz and 20 kHz, with different pulse length s and shapes of the acoustic beam. The wide range of the operating parameters offer s the possibility of adapting th e system to the demands of the
different projects. Acoustic data had to be stored on magneto - optical discs and on DAT - tapes fo r postprocessing.
The firs t ste p of the work on board was the installatio n of the acoustic transduce r array in the moonpool. Then, some basic measurements an d tests were planned in order to improve the system. New operational modes (permittin g very high pulse rates) and online data processing procedures had to be
developed an d to be tested under different conditions . At least th e system had to be prepared fo r profiling during cruise part S082B . In order to get a maximum of acoustic
information about the sea bottom both echosounders (Parasound - Paradigma and SEL9 0) and the Hydrosweep had to be used
simultaneously. Performin g th e test measurements th e operators of the different acousti c system s had to get the necessary experience fo r doing this multi-sounder profiling.
Cruise Report S082
2 . 2 . P a r t i c i p a n t s
Participating institutions
GeoB: Fachbereic h Geowissenschaften, Universitat Breme n IOW: Institu t fil r Ostseeforschung Warnemunde an der
Universitat Rostoc k
IfG-H: Institu t fu r Geophysik, Universitat Hambur g
KGS: Kansa s Geological Survey , Kansas University, US A URE: Universita t Rostock , Fachbereich Elektrotechnik ,
Institut fu r Nachrichtentechnik un d Informationselektronik
Ships crew M.Kull(Master) A.Macke(2nd Mate ) Y.Msyazhenko(Doc.)
H . - J . P r i i s s n e r (2nd Eng . ) N.Guzman(2nd E n g . )
R.Duthel(Electron.)
T.Steffenhagen(Electron. ] S.Ladage(Syst. Op.)
V.Blohm(Motorman) B.H.Bethge(Motorman) A.Penk(2nd Cook ) W.Scheller(Steward)
K. -H. L o h m i i l l e r ( B o a t s w a i n ; W.Hodl(A.B.)
W.Jahns(A.B.) P.Schober(A.B.)
S.Buhlow(Chief Mate) W.Sturm(R/0)
H.-J.Neve(Ch. Eng.) A.Rex(2nd Eng.) W.Huxol(Electr.) H.Voehrs(Electron.) A.Tank(Syst. Op.)
R.Rosemeyer(Storekeeper]
M.Hoevelmann(Motorman) H . M u l l e r ( C h . Cook) M . B o t h ( C h . S t e w a r d ) H . J . P r e c h t l ( S t e w a r d ) D.Mahlmann(A.B.) H . K r i i g e r (A.B. ) P . D e m b a ( A . B . )
Scientific crew N.Anderson,
R.Endler, T.Forster, I.Grevemeyer, W.D.Heinitz, R.Herber, G.Nickel, Th. Rose, V.SpieS, Th.Warncke, G.Wendt,
geophysicist, chief scientist , student,
student,
electronics engineer, geophysicist,
geophysics technician , student,
geophysicist,
electronics engineer , electronics engineer ,
KGS IOW IOW IfG-H URE IfG-H GeoB IOW GeoB URE URE
2.3. Cruise narrative - S082 A
(R.Endler)
The firs t part of the S082 cruise starte d in Balboa
(Panama) on September 29 , 1993, heading fo r the passage of the Panama chanal, the first part of the passage to Reykjavik. On the next day the ship passed Cristobal, entering th e Caribbean Sea. After a small lectur e about th e basic behaviour and
safety rule s on board given by the Chief Mate the scientifi c work starte d with preparation of installing th e new acoustic
systems. This was done in close cooperation with the ships crew and especially with the co-workers of the "scientifi c - technical service " of RV Sonne.
In order to get a maximum of working time for the second part of the cruise, the shortest rout e to Reykjavik had to be chosen. In accordance with the "DW D / Seewetteramt"
recommendations th e course over Windward-Passage (Octobe r 2) and the Caicos-Passage (Octobe r 3 ), south of Newfoundland towards 45°N 45°W was selecte d (Fig.2.1.-1) . Leaving th e Caribbean Island s a medium swel l of about 3 m fro m the NE direction caused stron g disturbances of both the Hydrosweep and the Parasound measurements presumably du e to air bubbles under th e acoustic transducers . The ship's spee d was 10 to 11 knots at this occasion. On October 05 , the ships course was changed to 58 degres in order to avoid a low pressure are a announced by a gale warning fro m DWD. The swell increase d to about 5 m fro m a wind of 6-8 Bft. fro m NNW heavily disturbin g the measurements. On October 06 , the transducer array of the SEL90 was installe d in the moonpool. A safety and rescu e
training of the whole crew was performed on October 08 . During the next days the wind increase d up to 9 Bft. and the swell came up to about 6 m . On October 11 , the wind changed to the east and decreased to 4-6 Bft .
On October 13 the ship arrived at the starting point of line SO82-P02 at 52°36'N 35°18' W (Fig.2.1.-1) . The course was changed to 002°, followin g th e axis of the MAR rift valley. At this line the Hydrosweep syste m operated permanently, mapping the central part of the MAR, while the installation- and
testing- work on the sediment penetrating echosounder s were continued. During th e next days the course was changed in order to follow the ridge axis. Because of the small tim e span available th e speed of the ship could not be reduced below 10- 11 knots. This resulted in a lower quality of the Hydrosweep data along severa l section s of the line. On October 15, reaching th e 200 nm border of Iceland all acoustic
measurements were finished . The total lengt h of the profiling lines amounts to about 85 0 nm. The firs t part of the cruise ended on October 16 , with the arrival at Reykjavik harbour fo r the change of the scientific cre w and embarkment of the second container containin g th e sampling equipment.
Cruise Report S082
Table 2 . 3 . - 1 Schedule of c r u i s e p a r t S082A
d a t e a c t i v i t y - time
29.09.92.
15:24 star t of S082A, Balboa harbour - Panama, passage of the Panama channel,
30.09.92
02:18 passag e Cristobal,
08:00 installatio n o f acoustic equipmen t start s (PARADIGMA, SEL9 0)
02.10.92.
1 8 : 0 0 l e a v i n g W i n d w a r d - p a s s a g e a t 2 0 ° 0 8 , 5 ' N 0 7 3 ° 2 1 , 9 ' W 03.10.92.
0 3 : 0 0 l e a v i n g C a i c o s - p a s s a g e a t 2 1 ° 4 1 , 5 ' N 0 7 2 ° 3 9 , 2 ' W 04.10.92.
1 2 : 0 0 s h i p s p o s i t i o n : 2 6 ° 2 2 , 5 ' N 0 6 8 ° 4 2 , 0 ' W 05.10.92.
0 8 : 0 0 c h a n g e o f c o u r s e t o 058° a t 2 9 ° 0 5 ' N 0 6 6 ° 0 8 ' W b e c a u s e o f g a l e w a r n i n g
1 2 : 0 0 s h i p s p o s i t i o n : 2 9 ° 2 8 , 8 ' N 0 6 5 ° 2 5 , 8 ' W 06.10.92.
1 2 : 0 0 s h i p s p o s i t i o n : 3 1 ° 5 2 , 8 ' N 0 6 0 ° 5 9 , 4 ' W 07.10.92.
1 2 : 0 0 s h i p s p o s i t i o n : 3 4 ° 3 9 , 2 ' N 0 5 7 ° 3 8 , 7 ' W 08.10.92.
1 2 : 0 0 s h i p s p o s i t i o n : 3 7 ° 3 2 , 8 ' N 0 5 4 ° 1 7 , 6 ' W 09.10.92.
1 2 : 0 0 s h i p s p o s i t i o n : 4 0 ° 2 2 , 7 ' N 0 5 0 ° 5 3 , 1 ' W 10.10.92.
1 2 : 0 0 s h i p s p o s i t i o n : 4 3 ° 2 4 , 9 ' N 0 4 7 ° 1 7 , 3 ' W 11.10.92.
1 2 : 0 0 s h i p s p o s i t i o n : 4 6 ° 3 1 , 7 ' N 0 4 3 ° 2 7 , 3 ' W 12.10.92.
1 2 : 0 0 s h i p s p o s i t i o n : 4 9 ° 2 8 , 5 ' N 0 3 9 ° 3 7 , 3 ' W
13.10.92
09:28 star t of line SO82-P02 at 52°19'N 35°42'W , course 002°, with HYDROSWEE P mapping of the MAR rift valley 19:06 a t 54°19,0'N 035°10,8'W change of course to 001°
14.10.92
0 1 : 0 7 c h a n g e o f c o u r s e t o 012° a t 5 5 ° 2 9 , 0 ' N 0 3 5 ° 1 7 , 1 ' W 0 5 : 2 8 c h a n g e o f c o u r s e t o 040° a t 5 6 ° 2 1 , 0 ' N 0 3 4 ° 4 7 , 0 ' W 1 4 : 0 2 c h a n g e o f c o u r s e t o 025° a t 5 7 ° 3 7 , 9 ' N 0 3 2 ° 4 6 , 1 ' W 15.10.92
12:06 en d of line SO82-P03 at 61°00,1'N 028°04,6'W, passage to Reykjavik
16.10.92
11:24 arriva l at Reykjavik, end of part S082A , exchange of crew, embarkation of scientific equipment .
Cruise Report S082 9
2.4. Methods
(R.Endler)
The scientific planning an d way point navigationa l
workstation was used fo r planning of the profiling tracks and the sampling stations. The system allows the creation of a trackplot of the intended line s and stations. It calculates the distances and the travel tim e at a given shi p speed. The results are printed and plotted. Furthermore, the data are stored in a file which is used by the ship's navigation syste m subsequently. The system was working very reliabl y an d
supported th e planning an d organization of the scientific wor k during th e cruise.
The positions of the ship were estimated by GPS and
processed (navigationa l filter ) by the interface processor of the ANP 2000 navigation system . All data were calculated for the WGS 84 system. Navigational dat a were store d in separate files in ASCII forma t by the ANP2000 an d the Paradigma - system.
The multibeam echosounder ATLAS HYDROSWEEP DS from Atlas - Elektronik GmbH, Bremen was used to map the morphology of the sea floor. The Hydrosweep syste m works in a similar way as an ordinary echosounde r but uses a fan of 59 acoustic beams.
This fa n is orientated perpendicularly to the ship s course.
The central beam points vertically to the sea floor . Two sets of acoustic beams are directed sideway s (lef t and right) with a maximum angle of 45 degrees. Thus, a stripe of about twic e of the water depth is covered during profiling. The soun d
velocity profile which is necessary fo r the calculation of the water depths is estimated by a special procedure. During
profiling th e acoustic fa n is rotated 90 degrees int o the direction of the ships course after a certain number of
measurements. Comparing and matching th e depth data measured by the backward pointing beams with the depth contou r
estimated by the central beam during th e forme r profiling th e sound velocity ca n be estimated and corrected. Raw data were stored on tape and sent to the Hydro Map Syste m 30 0 (HM S 300, HP 9000 / 400 workstation) fo r processing. Processe d data were stored on optical disc. On a second workstation depth - maps and 3 dimensional views were created. The maps were plotted on a HP pen plotter and stored as HPGL file s on disks. Grid data of the maps were store d on files fo r postprocessing too .
Excluding som e nonexplanable syste m faulure s th e Hydrosweep multibeam echosounde r worked properly.
The main characteristics of the Hydrosweep syste m are:
operating frequency : 15. 5 +/- 0.6 kHz angle of transmission: 2 * 45 degrees no of acoustic beams: 5 9
calibration: manual , entering a sound velocity
profile or self - calibrating using a mean sound velocity estimate d fro m measurements alon g the course
corrections: rol e (+/-2 0 deg) and pitch (+/-10deg ) max range: centra l beam - 10000 m, outer beams -
7000 m
covered range : abou t 2 * waterdepth
accuracy: abou t 1 % (at waterdepth between 10 0 - 600 0 m, role < 10 deg., pitch < 5 deg.
In order to investigate th e highly distinctiv e structur e and distribution of the sediments in the Reykjanes Ridg e
region two acoustic profiling systems, th e extended narro w beam echosounder syste m Parasound - Paradigma and the SEL9 0 sediment penetrating echosounder , were installe d and tested.
The results of the measurements were digitally store d on tape / optical disc (SEL90 ) fo r postprocessing an d recorded on a thermo-printer / colour-inkjet (SEL90) . Both profilers an d the Hydrosweep syste m were operated simultaniously . A more
detailed descriptio n of the acoustic profiling system s is given in chapter. 2.5.1. and 2.5.2. Furthermore, a
comprehensiv description of rv "Sonne" and the installe d research technique s is given by BEIERSDORF et.al . (1993) .
Cruise Report S082 1 1
2.5. First results
2.5.1. Subbottom profiling with the Parasound System
(V.SpieS, Th.Rose)
The Parasound Echosounder System on RV "Sonne"
With the installation of three Parasoun d echosounde r systems in the large German research vessels "Meteor" ,
"Polarstern" and "Sonne " high-resolution seismo-acousti c studies can be extended and improved significantly . Based on special characteristics of the parametric echosounde r as the narrow sound emission beam and a flexible signa l contro l
seismic data of high quality ca n be collected. Also the
digital data acquisition syste m Paradigma , which was develope d at the University of Bremen (SPIESS , 1992) , was installe d fo r digitization and permanent storag e in standardized dat a
formats in research vessels "Meteor " and "Polarstern" .
During the scientific cruis e S082A in transit fro m Panam a to Iceland th e Paradigma Syste m was also installe d on rv Sonne. Thereby th e acquisition of high-frequency seismi c dat a on German research vessels could be unified fo r all scientifi c users.
The operation of the Parasound System during cruise S082A
A systematically modified an d improved version of the Parasound System , based on the experience of these systems on research vessels "Meteor " and "Polarstern " fo r the last thre e years, has been installe d in rv "Sonne" recently. During th e transit of 2 1/2 weeks duration the echosounder syste m was used fo r continuous recording . Numerous feature s were teste d and a number of deficits and problems could be identifie d an d corrected or solved subsequently . Measurements on station and comparisons of different signa l parameters were not possible due to a shortage of time. In general th e Parasound syste m on rv "Sonne " provides data of a quality tha t is comparable to the other two systems on rv "Meteor" and rv "Polarstern". The modifications improved the system fo r analog as well as
digital recordings.
Due to variable se a state and weather condition s in
particular in the Caribbean Sea and near Bermuda Island , th e surface waters were mixed to a high degree with air bubbles.
These conditions probably cause d th e partial los s of signal energy and reflections, which was repeatedly observe d in parallel fo r several second s in the Parasound syste m as well as in records of the SEL-90 echosounder syste m of the
University of Rostock. In addition, shor t interval s of extremely high noise amplitudes were measured. A possible explanation were assemblages of air bubbles, which were trapped, perhaps in a rather thic k natural cover , and moved
along the keel. They may cause acoustic noise and inhibit the development of the parametric signa l due to high absorption.
At the same time the Hydrosweep syste m was not able to provide any useful data at all under thes e circumstances. Although between 10 and 40% of the seismograms did not reveal surfac e and subsurface echoes , the remaining seismogram s were of acceptable quality. The system operators coul d not report an y comparable situatio n of data losses and therefore we assign these observations to the special weather situation , sea stat e and surfac e water conditions, which were often foun d
particularly in the North Atlantic.
Towards th e end of the cruise, north of Newfoundland, the weather became calm, and the echosounder recording s of all
systems immediatel y improved . But still, the sea state in general control s the data quality as was observed also on R/V Meteor. Only on rv "Polarstern", with a draught of -11 m this relationship is not valid this strictly. Possible causes
related to the design of the keel and features , which can trap and accumulate ai r bubbles, have to be studied in greater
detail during futur e cruises.
As expected fro m the physical characteristic s of a narrow beam echosounder, in areas of rough topography coheren t echoe s from the ocean floo r could not be observed. In some cases a scattering interva l of more than 100 m in depth were foun d at steep slopes. But due to the large bandwidth of 0-10 kHz, compared to 2-6 kH z of older Parasoun d systems , the bottom echo could stil l be detected fro m scattered energy . The examples fro m the Mid Atlantic Ridge near Icelan d also sho w some intervals of sediment cover.
Installation of the Paradigma System for digital data acquisition
The development of a system fo r the routine acquisitio n of high frequenc y echosounder data was started in 1988. During the followin g years a system was designed by the marine
geophysics group at the University of Bremen specifically fo r recording digita l Parasoun d seismogram s and directly
integrating shipboar d data (SPIES , 1992). Th e hardware concep t of the Paradigma syste m (PARAsound-DIGitizin g und
Multichannel-Analysis System ) is shown in Fig.2.5.1.-1. The two major task s of 'Data Acquisition' and 'System Control' were assigned to two physically an d logicall y separate d
hardware components . A mutual interferenc e is thereby reduce d to a minimum. Severa l channels can be digitized
simultaneously. Trigge r inpu t and buffering of large data set s are handled by the HP3852A device, a programmable,
multitasking dat a acquisition unit, which is connected to an IBM compatible personal compute r via a IEEE-488 (HPIB )
interface. Transfer of data, collection and integration of navigational an d status information , data storage, graphical output an d production of tables are managed by a high
performance PC.
Cruise Report S082 1 3
The installed Paradigma version treats only one signal line which is connected to the true Parasound seismogram . The signals are digitized with a sampling frequenc y of 40 kHz
(max. 100 kHz). The oversampling is sufficient for detailed postprocessing of the complete amplitude and phase
information. Due to the autoranging featur e of the digital 13-bit voltameter a total dynamic rang e of -120 dB is
available. The data are stored on two internally buffered , industry compatibl e 1/2" , 9 track magnetic tape s with a recording density of 6250 bpi. The storage forma t is adapted from the SEGY-Standard with minor deviations.
With this concept all major tasks of data acquisition, data transfer, programming of the digitizing parameter,
internal and online control of the system can be done in parallel with extremely high data throughput and without
affecting the measurement process . On PC's with a 80386/87 or 80486 processor als o online processing can be added without reducing the overall syste m performance. The continuous dat a stream fro m Parasound and shipboard system s is integrated immediately and can be plotted on the computer screen .
The Paradigma software package
The software package Paradigm a is very simila r to those versions running on R/V Meteor and Polarstern and provides a uniform user interfac e for sediment echosounding studies on German research vessels. In addition to typical task s of a seismic digital recording unit, several feature s were include d for online control, data integration and graphical output.
These feature s are:
interactive online control of the measurement process;
data storage on hard disk or magnetic tape ;
integration of serial line s with navigation and status information;
tabular output of navigation and status information ; preprocessing and graphical outpu t of seismograms;
graphical output of depth profiles;
graphical outpu t of ship's track;
printout of colour coded seismi c sections.
Digital Parasound examples from the North Atlantic and Mid Atlantic Ridge area
The primary goal of the sediment echosoundin g studie s during cruise S082A was the installation of the Paradigma system, som e detailed test s of the Parasound echosounde r and first analyses of digital Parasoun d dat a recorded on rv
"Sonne". The five examples (Fig. s 2.5.1.-2 to 2.5.1.-6) shall prove a successful implementatio n of the Paradigma syste m on rv "Sonne".
Figures 2.5.1.-2 and 2.5.1.-3 represent consecutiv e
profiles of f the continental margin of North America at 42°N / 48°W. They sho w a high energy depositional environmen t wit h coherent subsurfac e reflector s an d interbedded mass flo w deposits. The morphology is controlled by downslope current s that cu t E-W striking , erosional channel s perpendicularly to the ship's track. Although th e data quality is affected by disturbing weather condition s and a high electronic nois e level, the post processing of the digital data provided a detailed imag e of the ocean floo r and subbottom structures.
To verify th e increased acousti c bandwidth of the signal reception part of the Parasound system , three records fro m the Mid-Atlantic Ridg e between 53° N and 61° N are shown in Figures 2.5.1.-4 to 2.5.1.-6. Sinc e the topography doe s not allo w coherent reflection s fro m a smooth surface, only diffracte d energy ca n be received fro m within the sound emission cone of 4° opening angle. Steeper slope s and a rough surface cause a scattering of energy over lon g depth interval s up to 100 meters. Besides th e obviously dominatin g magmatic surfac e rocks in Figure 2.5.1.-4 also a short interva l (a t UTC 16:30 ) is found, where higher reflection amplitudes an d a coherent bottom ech o indicat e a sedimentary coverage . In all three examples th e bottom can be tracked by the smeared interva l of higher energy, which is often not possible with the 2-6 kHz bandlimited Parasound system s on rv "Meteor" and "Polarstern" . Figure 2.5.1.-5 shows a typical sequenc e in a ridge area with some interval s of high reflection amplitude on the bottom of topographic lows . A much shorte r average wavelength of the topographic feature s is observed in Figure 2.5.1.-6 from the Reykjanes Ridge in about 80 0 m water depth.
Cruise Report S082 15
SIGNALS AND TRIGGERS
Parametric Signal 2.5-5.5 kHz
Envelope
10
Parametric Signal 2.5-5.5 kHz Sei sinogram
Sampling
kHz 4 0
Bottom Echo 18 kHz ->7 kHz
ASCII Data -Parasound -Navigation -General Data
frequency
kHz 8 0 - kHz
n :iyi!f#;:
MASS STORAGE 20 m A
:•:::: . iililt::::::":^::::!::::!;! ;:
IN;;; ;;-;;;;:';:;.;;;;- • :
Interface converter
2 Magnetic tape drives 1/2" 6250 bpi/max. 150 MB
RS 23 2
Multiplexer
Tape Controller TC1540
Fast Digitalvoltmeter 13 Bit, 100 kHz, 120 dB
DATA ACQUISITION UNIT 3852 1 MB RAM
int. Clock L
HP-IB
Interface Computer Control Data transfer
Protokoll Printer
PERS.COMPUTER 80486 33 MHz, 4 MByte RAM Hard disk 60 0 MByte Floppy-D 3.5", 5 1/4"
Super-VGA 1024x 768 Pixel
Parallel Interface
Color Monitor
GRAPHIC PERIPHERALS
Color Printer
Control Program P S (3.0) - Menu-driven parameter input - Selftest of peripherals - System initialisation - Programming of multitasking
environment of HP3852A - Keyboard driver for commands - Serial interrup t driver
Parasound/Navi gat i on - Controlle der recording via
data acquisition unit - Data transfer of Seismograms - Sei sinogram plot on screen - Plot of ship's track - Plot of depth profile - Data storage on hard disk/
magnetic tape drive
- Table output Navigation/Status - Online processing of seismograms - - Printout of color coded sections -
Hardware - VGA Alphanumerics - HPIB, Serial,Parallel - HPIB, Serial,Parallel - HPIB
- Keyboar d - Serial - HPI B
- HPIB
- VGA Graphics, Printer - VGA Graphics,
- VGA Graphics, - Tape Controller/
Magnetic tape drives - Parallel Printer - Paralle l Printer
Fig. 2.5.1.-1 Hardware concept and softwar e components of the Paradigma System (PARAsoun d DIGitizing and Multichannel
Analysis System )
0£:9
swt^r
' ^ ^ f c ^ ^ j - ^ -~ -
Z6'0L-0l 0£= S
.vitUta
S/Z£
iduiv SZ££
Mldao 5/££
Fig. 2.5.1.-2 Digital Parasound profile from the North
Atlantic at 42°N/48°W showing continuous subsurface layering with interbedded mass flow deposits and deep erosional channel cutting. Vertical scal e in meters i s given fo r a sound
velocity of 1500 m/s. Horizontal scal e is slightly varyin g with ship's speed. I n general a time interva l of 1 0 minutes
represents a distance of 2 nautical miles at an average spee d of 12 knots.
Cruise Report S082 17
fdFi
"feasted
igrgBss^
oo=z
26"0r0t 0 £ = 9
S/2£
ldmv SZ££
qjdaa S/££ SJVE
Fig. 2.5.1.-3 Continuation of the digital Parasound profile in Fig. 2.5.1.-2. See Fig. 2.5.1.-2 for further explanation.
^ ^ ^ 2 « * £ 8 $ p S
•Wb*J»i*SMfe
f4
0E = 9L
02^91
01=91'
00 = 9t"
:a;;-tF-'A^s'--.Ti- v
•-^BffiilSii.
- 1 1 1 1 I L _
Z 6 " 0 r £ l 0^=SL
0002 00L2 00£2 0092
Fig.2.5.1.-4 Digital Parasound profile from the Mid Atlantic Ridge Area at 53°N/35°W. See Fig. 2.5.1.-2 for further
explanation.
Cruise Report S082 19
0S2Z
Fig.2.5.1.-5 Digital Parasound profile from the Mid Atlantic Ridge area at 57°N/33°W. See Fig.2.5.1.-2 for further
explanation.
JS*©**--
S » = l t
SV = 0l
Z 6 ' 0 r S l 0 £ = Ol'
0090
ldwy mdaa 0011
Fig.2.5.1.-6 Digital Parasound profile from the Reykjanes Ridge area at 61°N/28°W. See Fig.2.5.1.-2 for further explanation.
Cruise Report S082 21
2.5.2. Test o f th e sedimen t penetratin g echosounde r SEL90
(G. Wendt, R. Endler)
Sende-/Empfangs- Schallwandler- Array
~" 18 30 m
Elektrische Wandler- kom pen sat ion
-+-
18 32m 18 Elemente0,6 x 0,6 m2
Vbrver- starker max. 24 Kan ale Sender max. 24 Stuck
Phasen- ste lie rung Empfang.
Phasen- stelie rung Sender
Verstarker Filer Demodu- lator ADC
Akku- rechner
Steuer-
rechner Entschei- dungs- rechner
Slgnalverarbeltungselnhelt
SEL90
Urwersitst Rostoc k
DAT-Recorder Farb-
Dmcker MO-DrK/e PC-AT
486 - 3 3
To investigate i n detail sedimen t sequence s i n regions like the MOR, with a rough morphology o f the seabottom is a very complicated tas k and a challenge fo r the development o f highly sophisticate d seismoacousti c systems . Good results have been obtained with parametric echosounder s lik e the Parasound . Using nonlinear acoustic effect s these systems create a narrow acoustic beam of low frequency pulses. Because of the lo w
acoustic
efficiency of the
parametric effect a high technical expense is necessary t o generate the acoustic power required.
With the use of low-
frequency acoustic pulses deep penetration can be
obtained i n horizontal or slightly
sloping sedimentary layers. In regions with
a strongly tilte d and rough sea bottom th e acoustic pulse s will be reflected with an angle directed awa y fro m the ship, whereby no echoes will be received by the echosounder.
Sediment penetrating echosounder s lik e 3.5 kH z profilers operates i n the linear range and have wider acoustic beams. A larger area of the seafloor i s acoustically "illuminated "
during profiling. This lead s to a markable decrease i n
vertical and horizontal resolution , specificall y i n regions with a rough morphology o f the sea bottom. Narrow beam pulses which gives a higher resolution can be generated by
transducers of small dimensions only i n the high frequenc y field. Using high frequenc y acousti c pulses se a bottom echoe s can be received also i n regions with a rough and strongl y tilted morphology because of backscattering effects . But, the high attenuation of the high-frequency signal s i n the water column and in the sediments has prevented thei r use in
sediment profiling system s up to now.
Fig. 2.5.2-1 Configuration of the sediment penetrating echosounder SEL90
The SEL9 0 echosounder was designed t o compensate thes e losses by increasin g th e transmitted acousti c energ y and
applying adapted onlin e signa l processing procedures. This was obtained by followin g arrangements:
high shooting rate , adapted to the observed / displayed time window of the acoustic recordin g
stacking of several acoustic trace s i n order to improve the signal vs. noise ratio
short pulse lengt h fo r high resolutio n
selecting th e frequency o f the acoustic pulses with respect t o high penetration an d resolutio n
use of specia l processing procedures fo r detection and resolution of scattering center s at sea bottom slope s
Fig. 2.5.2-2 SEL90 recording (amplitude display, 20 kHz) of a rough sea bottom with slopes up to 60°, depth range 1000 - 1500m, horizontal extensio n about 1 2 km
Fig. 2.5.2.-1 shows the configuration of the sediment echosounder SEL9 0 modified fo r deep-sea application. The
Cruise Report S082 23 echosounder i s designed fo r mobile use. The transducer arra y consist o f 1 8 magneto-strictive element s which were mounted i n the front moonpool of rv "Sonne" . The noise caused by
hydrodynamic turbulences was reduced by an acoustic windo w closing th e lower end of the moonpool. At th e end of the cruise on the way t o Bremerhaven th e acoustic damping o f the window was measured. The results indicate d a bad quality of
Fig. 2.5.2.-3 SEL90 recording (high resolution mode, 10 kHz) of rough sea bottom, hyperbolic echoes indicating lifted out (back scattering) features, depth range 850-1180m , horizonta l extension about 5 km
the used material causing high losses of acoustic energy . Nevertheless, very good records were obtained proving th e outstanding performance o f the system. The equipmen t
electronic o f the SEL90 was installe d i n the seismi c la b on the main deck. The electronics were housed i n a portable rack.
Simultaneously with the online processing an d display o f the received signals , the raw data were store d on DAT - tape (ful l waveform) and on optical disc (envelope ) fo r post-processing.
After installatio n of the program includin g test s of the units and of different operat i results confir m the efficiency examples fro m the central part operational modes are shown in Operating both the echosounde r simultaneously, disturbance s o especially when the 2 0 kHz mod primary frequencie s of about 1 times higher tha n that of the pulses.
equipment a n extensive working several hardware and softwar e ng modes was performed. Th e
of the system. Som e record of the MAR using differen t
Fig. 2.5.2.-2 to Fig. 2.5.2.-4.
Parasound an d SEL9 0
ccurred i n the SEL90 recording s e was used. This i s due to
8 kHz and the huge power (10 0 SEL90 signals) of the Parasoun d
The measurements an d tests suggest tha t furthe r improvements o f the SEL 9 0 system can be obtained by:
increasing th e acoustic energ y by higher transmittin g power and special form s of the acoustic pulses (coded) ,
improved filter s (notc h filters) ,
multifrequency soundin g (alternating) ,
electronically controlle d beam stabilizin g an d steerin g (perpendicular t o the surface) ,
optimizing processing an d decision processes.
Fig. 2.5.2.-4 SEL90 recording (high resolution mode, 5 kHz) a sediment pond with a penetration of more than 2 0 m, dept h range 1310-143 0 m, horizontal extensio n about 3. 8 k m
of
Taking i SEL90 syste m project was s penetrating e about th e sea regions char a The data obta for the selec Further devel frame of join
nto account tha t this was the f in the deep sea , it can be stat uccessful. The combination of t chosounders provides very usefu bottom relief and the sediment cterized by a rough morphology ined during regular profiling f tive sampling of sediments duri opment of the system will be pe t research projects.
irst test of the ed that th e
wo sedimen t 1 informatio n
structure i n and steep slopes ormed the basis ng part S082B.
rformed i n the
Cruise Report S082 2 5
2 . 5 . 3 . E p i s o d i c s p r e a d i n g a t t h e Reykjanes Ridge
(I.Grevemeyer, R.Herber, W.Weigel) A b s t r a c t
During th e rv "Sonne " cruise S082A a single Hydroswee p profile over the Reykjanes Ridge crest was carried out. The recorded bathymetric strip e allows a classification of two main segments . The southern segment between the Charles Gibbs Fracture Zon e and the Bight Discontinuity i s a typical part of the northern Mid Atlantic Ridg e with rift mountains bounding a median valley. The Bight Discontinuity seem s to be a
transition zon e between the influenced an d non-influenced region of the Iceland hotspot. From this transition zon e the second segmen t trend s 3 6° northeastward towar d Iceland . Obliqu e spreading and en echelon ridges are typical, striking sout h of 61°N perpendicularly t o the spreading direction of 103° . The overall structur e of the Reykjanes Ridge supports a mainly amagmatic-tectonic evolutio n as it is typical of episodi c spreading models.
Introduction
In autumn 199 2 the German rv "Sonne " carried out a single Hydrosweep profile over the central part o f the Reykjanes
Ridge (S082A) . This structure i s part of the Mid Ocean Ridge (MOR) System. Since the acceptance of plat tectonic s a s a
unifying model fo r the development an d rejuvenation of oceanic crust, the prominent Mid Ocean Ridges have been attributed t o these processes. Distinctive feature s of Mid Ocean Ridges include their bilateral morphology aroun d a central axis , th e generation of Mid Ocean Ridge basalts and the intermitten t volcanism which i s related t o the spreading rat e and the magma
supply. Thus the large scale ruggedness of the seafloo r topography decrease s with increasin g spreadin g velocity i n combination with increasin g magma production.
The volcanism o f fast-spreadin g ridges i s restricted t o an axial volcanic ridge , whereas at slow-spreading ridge s
seamount-volcanism is common in addition t o axial doming (e.g . BALLARD & ANDEL, 1977 ; SMITH & CANN, 1992) . Detaile d
investigations o f the MOR indicat e phases of volcanic inactivity, i.e . the rift i s characterized by an axial
tectonic graben. These observations suppor t th e development o f an episodic morphotectonic accretion model (e.g . LEWIS, 1979;
KAPPEL & RYAN, 1986 ; GENTE, 1987) , splittin g th e spreading i n an active-volcanic an d an amagmatic-tectonic phase.
65° N />0°W
50'
20 ISLAND 65° N
CHA R L I E
40° W 30c 20 50l
Q
Fig. 2.5.3.-1 Course over the Reykjanes Ridge crest of the rv
"Sonne" cruise S082A
Cruise Report S082 2 7
Results of the Hydrosweep - profile
According to the morphotectonic feature s we divided th e Reykjanes Ridge int o two main segments. The southern segmen t is bordered to the south by the Charles Gibbs Fracture Zon e and to the north by the Bight Fracture Zon e (Fig . 2.4.3.-1) . From the Bight Discontinuity th e northern segmen t extend s to Iceland.
The southern segment show s the typical morphology of the North Atlantic MOR, i.e . an axial graben and flankin g rif t
mountains (Fig.2.5.3. - 2A). As typical fo r the tectonic phas e of the episodic spreadin g model, the rift is characterized by a tectonic graben and depressed areas , rather tha n by an axial volcanic ridg e and an abundances of volcanoes, as commonly
found along th e active section s of the Mid Atlantic Ridg e (BALLARD & ANDEL, 1977; SMITH & CANN, 1992) . Th e axial zon e strikes 3-4° between Gibbs Fracture Zon e and 55°14.8'N .
At 55°14.8'N , we observed an unforseen change in the strike of the axis. Here the rv "Sonne" left the axial zone.
Near the Bight Fracture Zon e the rift valley was reentered . Today th e Bight Fracture Zon e seems to be a transition zone between the influenced an d the non-influenced regions in relation to the Iceland hotspot, rather than a first orde r discontinuity with a transform valley (MACDONAL D & FOX, 1990) .
The northern segmen t of the Reykjanes Ridge, north of the Bight Discontinuity strike s northeastwards in the
direction of Iceland. The general strik e of the axis along this segment is 36°, although the plate motion is 103°
(FLEISCHER, 1974) . Therefore , unlike most spreadin g centers, the Reykjanes Ridge axis is not oriented to its spreadin g direction perpendicularly, th e spreading is oblique of about 23°. Th e rough topography contain s a series of 10° trending en echelon ridges, which are oriented to the spreading directio n perpendicularly (Fig.2.5.3. - 2B).
The northern segmen t of the Reykjanes Ridge form s a slow- spreading ridge with a spreading rate of 1 cm y r1 (TALWAN I et al. , 1971). Near Icelan d a hilly- or horst-like profile is typical fo r the axis of the Reykjanes Ridge , however, and this is more consistent with the features of a fast-spreading ridge
(JOHNSON & JAKOBSON, 1985 ) . This horst-like featur e reduce s steadily in amplitude southward s fro m 61° N and changes int o a median valley at about 59°N .
Apart fro m the en echelon ridges, the Hydroswee p recordings reveale d a number of volcanoes. Frequently the summit of these seamounts has a crater or a depressed are a like a caldera. Deep depressions, interpreted a s collapse d lava ponds were observed, too (Fig.2.5.3.-3).
54°10'N
54°00'N
35°10'W
(A) (B)
Fig. 2.5.3.-2 Hydrosweep stripes of the Reykjanes Ridge crest, 20 m contour intervall . (A ) The southern segment i s
characterized by a median valley and bounding rif t mountains, the valley i s dominated by a tectonic graben. (B ) En echelon ridges, trending perpendicularly t o the spreading direction, but are oblique to the strike of the axis of spreading are
located i n the rift valley floo r of the northern segment.
Cruise Report S082 29
(A!
58 53.2'N |31°03.1'W
500 m
:B)
500 m
Fig. 2.5.3.-3 Bathymetric charts of depression areas at the Reykjanes Ridge, 2 0 m contour interval . (A ) Volcano with a caldera lik e summit crater . (B ) Small collapsed lav a ponds.
Discussion
The structure of the southern segment of the Reykjanes Ridge is typical of the amagmatic-tectonic phase of episodic spreading models (e.g . GENTE, 1987) , i.e . the valley is dominated by a tectonic grabe n and only a limited number of volcanoes. Depressional area s are present.
We assume that the change in ridge crest topograph y in the the Bight Discontinuity area , i.e. th e transformation of the median valley to a horstlike or hilly structure , th e oblique spreading an d the en echelon ridges are due to the proximity of the Iceland hotspot. The axial high near Icelan d possibly th e result of larger magma chambers, heated by the hotspot (LAUGHTO N et al., 1979) . Alternatively th e axial high
is due to the amount of a lateral flo w away fro m Icelan d (JACOBY & GIRARDIN, 1980 ) i n which case the hight of the structure is dependent on the distance to the hotspot.
Possibly, the lateral flo w away fro m Iceland and the global plate motion could be the origin of oblique spreading , i.e . an
interaction between the flo w and the upwelling under th e Reykjanes Ridge could lea d to the oblique strike of the axis versus th e flow direction. Stretching forces , due to the global plate motion may have caused th e crust to fail,
initiating th e intrusive and extrusive volcanism which built the en echelon ridges perpendicularly to the spreadin g
direction.
Considering th e influence of the Iceland hotspot, th e overall structur e of the northern segmen t i s proposed a s due to a mainly amagmatic-tectoni c evolutio n which is also the case fo r the southern segment . Decisive feature s along the northern segmen t are the depression of the rift valley towar d the Bight Discontinuity, th e collapsed lav a ponds, th e
calderas and, compared to the MAR (SMIT H & CANN, 1992) , the small amount of volcanoes.
This interpretatio n is also supported by the observation s of an American / Russian submersible investigatio n near
59°50'N (CRAIN E et al., 1992) . At the occation the submersibl e
"Mir" dive d in an area that was within the epicentral regio n calculated fo r a 1989 seismic swar m (NISHIMUR A et al., 1989) . Almost no extrusive volcanic activity , but about 20 - 40 cm of sediment were observed revealin g an older lav a flow . From
these results, CRAINE et al., (1992 ) concluded that the
teleseismic swar m was caused by faulting or perhaps intrusive , but not extrusive, activities along the axis.
Cruise Report S082 3 1
Conclusions
The Reykjanes Ridge is built up of two main segments. The southern segment between the Charles Gibbs Fracture Zon e and the Bight Discontinuity show s the typical structur e of the northern Mid Atlantic Ridge: a median valley and flankin g rif t mountains strikin g in axis direction.
The Bight Discontinuity is interpreted as a transition zone between the influenced an d non-influenced regions of the Iceland hotspot.
The northern segmen t extend s fro m Iceland southwestwar d toward this transiton zone . From 61° N the axial high
typical of the segment adjacen t to the hotspot - decrease s in amplitude, and fro m about 59° N a median valley is present . Additional, the segment is characterized by oblique spreadin g and echelon ridges that trend to the spreading directio n
perpendicularly.
If we consider th e interaction between the Icelan d
hotspot an d the northern segment , the overall structur e of the Reykjanes Ridge could be interpreted as a result of a mainly amagmatic-tectonic evolution, as discussed by episodic
spreading model (e.g . GENTE, 1987) . Typical ar e the axial tectonic graben in the south as well as the depression area, the calderas and the collapse lav a ponds.
3. Part II . (S082B )
3.1. Research program an d working are a
(K.S.Lackschewitz, R.Endler )
The second period of the cruise, S082B, (Reykjavi k -
Bremerhaven) was devoted t o the investigation o f sedimentatio n processes, includin g thei r spatia l and temporal variability i n the area of the
Reykjanes Ridge.
Compared with other rift systems, the
Reykjanes Ridg e is characterized by very lo w spreading rates and the
climatic change s in the high
latitudes resul t in relatively hig h sedimentation
rates fro m 5 cm/1000 years to 20 cm/1000 years.
According t o
KUPTSOV (1 9 88) the sedimentation
rates can amount to values of up to 50 cm/1000 years.
The ocean area between 55°N and 6 5°N is
characterized by complex
hydrographical conditions which can be explaine d by the area's extraordinarily complex
climatological an d morphological
conditions. This leads to short-
and longterm changes i n the sedimentation processes. Major surface water and deep water circulation pattern i n the North Atlantic i s shown in Figure 3.1-1.
A small region of about 2 0 km * 70 km crossing th e rift axis at 59°10'N was selecte d as main working area fo r the
second part of the cruise. At about 58°39' N a detailed stud y of the tectonics, magmatism and the sedimentation processes was
W^OM-ut^STi
o^
<^1 Deep water circulation ' Surfac e water circulation
NAC • Nort h Atlantic Current IC = Irmlnger Current EGC m East Greenland Current
Fig.3.1.-1 Major surface water and deep water circulation pattern in the North Atlantic
Cruise Report S082 33 carried out by Russian scientists (ALMUKHAMEDO V et. al . 1990) , so, a good possibility of comparing the results was provided.
The program for the second part include d both geophysical and sedimentological investigations . Sediment samplin g along the transect at an angle to the ridge axis and subsequent
investigations on the mineralogical and chemical compositio n as well as analyses of settling velocity and granularity wil l contribute to a model of the genesis of the distributive
province "Reykjane s Ridge".
FS SONN E S082 Track plo t
Masstab' 1 ' 35000 0 lercator Projektio n Referenzbre;te 60" N Datum 2 7 10 92
Fig.3.1.-2 Trackplot of seismoacoustic lines and sampling stations in the detailed study area, S082B
Mapping of the research area and registration of the horizontal distribution and thickness of the sediments by means of the Hydrosweep multibeam echosounder, the Parasound - Paradigma echosounder syste m and the sediment echosounde r SEL 90 from the University of Rostock were firs t carrie d out on several profiles at the beginning of the second part of the cruise.
The results gathered in the course of the acoustic mapping were meant to be the basis fo r selecting samplin g stations. Fig. 3.1.-2 shows the trackplot of the profiling lines and samplin g localitie s performed during S082 B in the detailed stud y area near 59°N . The program of each individua l station include d the following steps:
application of the large box corer fo r samplin g of
undisturbed sediment s near the surface and macro benthos, application of the giant gravity core r to extract lon g sediment cores,
application of the gravity core r to extract sedimen t
cores, especiall y fo r sediment - physical studie s at the stations selected .
First work onboard include d basic sedimen t - physical measurements (inde x properties, shear strength) ,
sedimentological investigation s and , additionally, a
lithological descriptio n of the sediments as well as sampling for lab analyses on shore was suppose d to provide a survey of the sediment composition s an d characteristics, altogether.
Cruise Report S082
3.2. Participant s
Participating institutions
GEOMAR: GEOMA R Forschungszentrum fu r marine
Geowissenschaften der Christian - Albrechts Universitat z u Kiel
35
GPI:
IOW:
KGS:
PLR:
UGG:
URE:
UIB:
Geologisch-Palaontologisches Institu t und Museum der Christian-Albrechts-Universitat z u Kiel
Institut fu r Ostseeforschung Warnemiinde an der Universitat Rostoc k
Kansas Geological Survey , Kansas University, US A Projekttrager Material- und Rohstofforschung des Bundesministers fu r Forschung und Technologi e Universitat Greifswald , Fachbereic h
Geowissenschaften
Universitat Rostock , Fachbereich Elektrotechnik , Institut fu r Nachrichtentechnik un d
Informationselektronik
University o f Iceland, Biological Institut e
Ship's crew H.Papenhagen A.Macke
Y.Msyazhenko H. - J . Priissner N.Guzman
R.Duthel
T . Steffenhagen S.Ladage
V.Blohm B.H.Bethge A.Penk W.Scheller K.-H.Lohmuller W.Hddl
W. Jahns P.Schober
(Master) (2nd Mate) (Doc.) (2nd Eng.) (2nd Eng.) (Electron.]
(Electron.]
(Syst. Op.!
(Motorman) (Motorman) (2nd Cook) (Steward) (Boatswain]
(A.B.) (A.B.) (A.B.)
S . Biihlow W.Sturm H.-J.Neve A. Rex W.Huxol H.Voehrs A.Tank
R.Rosemeyer M.Hoevelmann H.Muller M.Both
H.J.Prechtl D.Mahlmann H. Kriiger P.Demba
(Chief Mate) (R/0)
(Ch. Eng.) (2nd Eng.) (Electr.) (Electron.) (Syst. Op.) (Storekeeper) (Motorman) (Ch. Cook) (Ch. Steward) (Steward) (A.B.) (A.B.) (A.B.)
Scientific crew
A T G J R J A B J P G R K K W F M J G S J B U R
Blanz, Bliesener Bublitz Eidam Endler Ewert Frahm Gehrke Harff Heinitz Hoffmann Knapp Korich
S.Lackschewitz Lemke
Lindemann Moros Mrazek Neufeld Nickel
Steingrobe Svavarson Trebstein Werner
phys. prop, specialist electronics engineer sedimentologist
geochemist
chief scientist
electronics engineer geology technician sedimentologist geologist
electronics engineer sedimentologist
geophysicist sedimentologist 2nd. ch. scientist sedimentologist student
student
sedimentologist geology technician geophysics technician sedimentologist
biologist student petrologist
GPI
IOW
UGG IOW URE IOW GEOMAR IOW URE IOW KGS IOW GEOMAR UGG GEOMAR IOW UGG IOW GEOMAR
IOW PLR UIB UGG GEOMAR
Cruise Report S082 3 7
3.3. Cruise narrativ e S082 B
(R.Endler)
The second part of the cruise, S082B, started in Reykjavik.
The scientific crew was exchanged and new equipment fo r sediment sampling wa s take n on board. The scientific cre w visite d the University of Iceland and was invited to a geological excursio n in order to see the rift, i.e. the continuation of the Reykjanes Ridge, o n shore. RV "Sonne" was visited b y students o f th e university. The ship lef t th e harbou r of Reykjavik on October 17, 1993 , headin g to the workin g are a at 59°N. The next day , after the usual instruction s concerning behaviour and safety on board, given by the Chief Mate, the new scientific equipment was prepared fo r operation. The working program was specified based on the results of the first part of the cruise. Two shifts were selected. Durin g th e night shif t acousti c profilin g was performed. Using these recordings the positions of the samplin g
stations were selected . Sedimen t samplin g was performed durin g day time.
On Octobe r 18 , 1992 the measurements starte d wit h Hydrosweep mapping and acoustic profiling (PARASOUND-PARADIGMA , SEL90) on line SO82-P0 4 alon g th e rif t axis , paralle l to line SO82-P03. Th e working are a was approache d on i n the nigh t of October 19 , while profiling . Base d o n the recordings the positions of the firs t samplin g station s were selected . Later ,
in the morning acousti c profilin g wa s interrupte d in order to take the samples. Undisturbed sample s of the sediment surfac e were obtained by the large box corer. A first core, taken by the giant gravity corer, was supposed to study it's sedimentological composition as well as for subsampling. A second core was taken using a n ordinar y gravit y core r fo r the investigation of physical propertie s late r on . Thi s "standard " procedur e was carried ou t at all sampling localitie s excep t for the station SO82-06 (centra l part) where the thickness of the sediments was too small.
On October 21, the weather conditions became rough. A storm (up to 12 bft) interrupte d th e wor k for the next days . Heav y waves damage d th e rails and some of the plastic cor e liner s which were stored near by. No damage occurred in the labs or in context with other research equipment.
During lat e evenin g of October 23 , the wind decrease d an d the normal working program was continued with profiling of line S082-11. Th e program i n the working are a wa s completed on October 24 with lin e S082-P12 . The transfe r to Bremerhaven was used fo r profiling, lin e S082-P13. This line was interrupte d at station SO82-0 8 were th e gravity core r was used to take a core of the "Hatto n drift" sediments.
Entering the Nort h Sea the ship wa s stoppe d i n order to measure th e acoustic attenuatio n of the acoustic window of the
SEL90 transduce r array . O n October 29 , th e ship approache d Helgoland islan d an d workers fro m th e ship yar d entere d RV
" S o n n e " i n o r d e r t o p r e p a r e t h e f o l l o w i n g r e p a i r i n t h e s h i p y a r d of B r e m e r h a v e n .
Table 2 . 3 . - 1 Schedule of c r u i s e p a r t S082A
d a t e a c t i v i t y time
17.10.92
17:00 star t of cruise S082B, passage to working area 18.10.92
12:48 star t of lin e P0 4 (61°21,461' N 27°33,639'W ) 19.10.92
03:54 en d o f lin e P0 4 (59°11,957' N 30°38,914'W) 03:56 star t of lin e P0 5 (59°11,855' N 30°39,823'W) 08:16 en d o f line P0 5 (59°35,144' N 31°41,876'W) 08:34 star t o f lin e P0 6 (59°34,123' N 31°44,610'W) 09:34 brea k of lin e P06 , passage to station SO82-0 1
(59°29,117'N 31°30,868'W ) 10:35 arriva l a t station SO82-01 , w-depth: 1867 m
GKG(0,33m), KL(0,92m) , SL(4,84m) ,
(59°30,578'N 31°29,616'W) 14:36 en d of station, return to P06
(59°30,592'N 31°29,494'W) 14:52 continuatio n P0 6 (59°2 9 , 299'N 31°30 , 878'W) 16:42 break , passage t o station SO82-0 2
(59°20,236'N 31°05,866'W ) 17:04 arriva l at station SO82-02, w-depth: 1730m ,
GKG(0,40m), KL(5,75m) , SL(5,56m) ,
(59°21,437'N 31°05,179'W) end of station,return to P06
(59°21,409'N 31°05,223'W ) continuation P0 6 ( 59°20,179'N 31°05,458'W) end of lin e P0 6 (58°58,153' N 30°08,303'W ) start of lin e P0 7 (58°57,050' N 30°09,408'W) end o f lin e P0 7 (59°20,711' N 31°11,239'W ) start of line P0 8 (59°19,750' N 31°13,072'W) break, passage t o station SO82-0 3
(59°18,422'N 31°09,491'W) 09:00 arriva l at station SO82-03 , w-depth: 1774m ,
GKG(0,36m), KL(5,78m) , SL(5,57m) ,
(59°19,639'N 31°08,358'W) 13:28 en d of station, return to P08
2 1 2 1 0..
02 02 08 08 08
: 4 0 : 5 8 10.1992 : 2 0 : 3 6 : 0 0 : 1 6 : 3 4
