CRUISE REPORT MARINE GEOLOGICAL CRUISE TO ULLSFJORDEN, LYNGEN, OFOTEN AND TYSFJORDEN, NORTH NORWAY RV Jan Mayen 6. - 12.2 2006 by Jan Sverre Laberg DEPARTMENT OF GEOLOGY UNIVERSITY OF TROMSØ N-9037 TROMSØ, NORWAY 1. Introduction and scientific objectives Here we report from a cruise that was organized from the 6 th to the 12 th of February to the North Norwegian fjords Ullsfjorden, Lyngen, Ofoten and Tysfjorden (Figs. 1, 6, 7). The aim was to do multi-beam swath bathymetry surveying and gravity coring. From Ullsfjorden we acquired multi-beam data and in Lyngen gravity coring was done. Multi-beam mapping was also done in parts of Ofoten and Tysfjorden. This work is a continuation of previous work that started in 2004 and continued in 2005 (Laberg and Guidard 2004, 2006). The data will be analysed as part of the Norwegian Research Council-funded SPONCOM project (http://www.ig.uit.no/sponcom/index.htm ). SPONCOM (Sedimentary Processes and Palaeo- environment on Northern Continental Margins) is a strategic University project at the University of Tromsø. 2. Cruise participants In addition to the regular crew of the University of Tromsø research vessel Jan Mayen (http://www.nfh.uit.no/hmenyvis.aspx?id=194 ) the cruise participants were: Jan Sverre Laberg, Research Scientist, Department of Geology, University of Tromsø (cruise leader) Trine Dahl, Laboratory technician, Department of Geology, University of Tromsø Kai Flöistad, Reseach assistant, Department of Geology, University of Tromsø Steinar Iversen, Science Engineer, Department of Geology, University of Tromsø 2 3. Cruise narrative Monday 6 th of February Weather: partly cloudy, southerly breeze reaching Gail in the afternoon, then decreasing. Departure from Tromsø at 11:00 local time sailing for Ullsfjorden. At 12:25 we had to return to Tromsø due to multi-beam software problems. We got the new software and left Tromsø at about 15:00 sailing for Ullsfjorden. Arriving Ullsfjorden we finished a CTD-station (06JM0044) (Fig. 2) for sound velocity data and calibrated the Kongsberg Simrad EM300 multi-beam system. The calibration was done and at about 19:00 we started surveying the fjord running lines parallel to the fjord axis. The data was of good quality (Fig. 1). Tuesday 7 th of February Weather: cloudy, southerly breeze. We continued surveying Ullsfjorden throughout the night and morning. No software problems any more, the multi-beam system was working fine. We got nice data from the inner and eastern part of Ullsfjorden including the Skarpnes moraine crossing the inner part of the fjord (Fig. 5). Then we surveyed the innermost part, Kjosen, and identified irregular, transverse ridges (Fig. 5). In the afternoon and evening we continued data acquisition, now in the western part of the fjord. At about 19:00 we did a CTD-station (0045) in the outer, central part of the fjord (Fig. 3). Above 180 m the water masses were very homogenous; the underlying water is about 1 o warmer and more saline. During the evening we finished surveying the inner part of Ullsfjorden and took a CTD cast (0046) (Fig. 4). 3 Wednesday 8 th of February Weather: partly cloudy, breeze, nice weather. The outer, western part of the fjord was surveyed during the night. This area has a relatively shallow water depth (< 150m). From the morning we left Ullsfjorden for a gravity core transect from Spåkenes, Lyngen (Younger Dryas ice front position) and out-fjord (Fig. 6). We did 11 gravity core stations and they were completed successfully at about 19:00. The core length varied from 115 to 535 cm (Tab. 1), a very good result. After finishing the core transect we returned to Ullsfjorden and continued surveying in the outermost part to complete the survey that started in 2005 (Laberg and Giudard, 2006). Thursday 9 th of February Weather: snow, breeze. The Ullsfjorden survey was completed at about 03:30 and we returned to Tromsø. Here we picked up J. Mienert and the Marine Geophysics students for a one day student course demonstrating the geophysical equipment of RV Jan Mayen and the basic principles of data interpretation. The course was ended in Tromsø at about 16:00; we unloaded some equipment and sailed for Ofoten at 18:00. Friday 10 th of February Weather: cloudy, partly snow, breeze We arrived the outer part of Ofoten at about 04:00 and started multi-beam surveying. The first line was running into the fjord along the south side, filling the data gap left from our first survey to this area in 2005 (Laberg and Guidard 2006). Then we continued doing the innermost part of Ofoten (Herjangsfjorden) (Figs. 7, 8). At about 12:30 a CTD station was done in this area (0049) (Fig. 9). 4 In the evening we did three gravity core stations in the inner part of Ofoten, gravity core 06JM009 (370 cm length) and 06JM010 (400 cm length) (Fig. 12, Tab. 1). No cores were acquired from the third station were we also did a CTD run (CTD 0050) (Figs. 8, 10). Saturday 11 th of February Weather: cloudy, little or no wind and very nice working conditions Continued multi-beam surveying, during the night we did the Balangen – Bogen transect, then Rombaken during the morning and Skjomen during the afternoon. In Skjomen we nicely mapped the terminal (Preboreal) moraine across the outer part of the fjord as well as the basins further into the fjord. One CTD cast (0051) was done in Skjomen (Fig. 11). The next area of survey was Tysfjorden (Hellemofjorden) which we started at about 23:00. Nice weather and working conditions in Tysfjorden. Sunday 12 th of February Weather: cloudy, rain, breeze. We did one multi-beam line into Hellemobotn and returned, this survey was completed at 08:00 including CTD station 0052 in the outer, deepest part of the fjord (Figs. 13, 14). The outer part of the fjord has steep sidewalls and a flat, undisturbed sea-floor. Further into the fjord it narrows and we passed a threshold at Musken. In the innermost part an irregular sea floor was identified. After completing the survey we sailed for Tromsø. Time of arrival: 18:00. 4. Equipment (from Laberg & Guidard, 2004) 4.1. The EM 300 multibeam system 5 A Kongsberg Simrad EM 300 multibeam echo sounder runs with a nominal sonar frequency of 30 kHz, in order to obtain an optimal balance between small dimensions, narrow beams and good range capability. This results in an angular coverage of up to 150 degrees and 135 beams (which are always within the active swath) per ping as narrow as 1 degree. The beam spacing is normally equidistant, with equiangular available. The transmit fan is split in several individual sectors, with independent active steering according to vessel roll, pitch and yaw to place all soundings on a best-fit to a line perpendicular to the survey line, thus ensuring a uniform sampling of the bottom and 100% coverage. Pulse length and range sampling are variable with water depths, to obtain best resolution. The swath width, dependent on seabed sediments, in shallow waters (< 500 m) is typically 5 times the water depth. Down to 2000 m, a swath width is 4-5 km is common. The system runs on a high performance PC (dual 2.8 GHz, 2 GB RAM), displaying the data collected and logging them to hard disk. As a standard, the following parameters are logged: depth, seabed imaging, vessel position, vessel attitude, and sound speed. The operator station converts range and angle data to xyz triplets, applying all corrections required by varying vessel attitude and sound speed. Sound speeds were loaded from external data source, being CTD sound velocity through the water column, after appropriate filtering and editing. A graphical user interface provides control on the data quality and parameters used. Note that, because of the protection housing installed around the hardware to avoid damage of ice contact, the amplitudes recorded are slightly attenuated (~6 dB). See Laberg and Guidard (2004) for further details. 4.2 The gravity corer Our gravity corer has a 6 m long steel pipe and an inner PVC liner of 110 mm diameter. Onboard, the samples are cut in 1m sections, numbered, sealed and stored in a cooling room (temperature 4-6 o C). 6 5. Preliminary results 5.1 Ullsfjorden Ullsfjorden is an asymmetric N-S oriented basin with an E-W oriented tributary in its inner part (Kjosen) (Fig. 1). The fjord basin is deepest towards the East, the western outer part forms a shallow platform of 100 – 150 m water depth. The deepest part has a flat sea floor, the sides are steep and irregular but relatively few indications of mass wasting is seen. The shallow platform shows longitudinal and transverse ridges inferred to be of subglacial origin and thus formed during the last glacial maximum. In the inner part a prominent ridge, the Skarpnes moraine is crossing the fjord basin (Plassen and Vorren, 2003). In Kjosen a series of transverse ridges has been identified, they are inferred to be formed during the Younger Dryas readvance (Fig. 5). 5.2 Lyngen The coring in Lyngen (Fig. 6) had two main objectives: 1) to elucidate on the age, origin and present level of activity of a channel system that can be followed from Spåkenes and northward into the deepest part of the fjord (cores 06JM001-006), see also Jenssen (2006), and 2) improve on the deglaciation chronology for the outermost part of Lyngen and to get a minimum age estimate for the deglaciation of the outer part of the fjord (06JM007-008). 5.3 Ofotfjorden The Ofoten survey was done in order to complete previous surveys to this area (Laberg and Guidard 2004, 2006) and focused on the innermost part of Ofoten (Herjangsfjorden) as well as tributary (Rombaken and Skjomen) (Figs 8, 12).