CRUISE REPORT

MARINE GEOLOGICAL CRUISE IN THE

NORWEGIAN SEA AND BALSFJORDEN, TROMS

R.V. Jan Mayen 21. -27. 7. 2002

By

Jan Sverre Laberg

DEPARTMENT OF GEOLOGY

UNIVERSITY OF TROMSØ

N-9037 TROMSØ, NORWAY

2

Preface

Although this cruise took place several months prior to the official start of the EURO-

STRATAFORM project we have included it in our EUROSTRATAFORM activities since all

the data acquired from the Andøya Canyon and Lofoten Basin Channel will be studied as part

of the project. These data will also be utilised in the SPONCOM project.

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1. Introduction and scientific objectives

During the RV Jan Mayen cruise from the 21st to the 27th of June 2002 data was acquired on

the continental margin offshore the Vesterålen and Lofoten Islands and in Balsfjorden,

Troms. The high-resolution seismic data and gravity core samples from the former area will

be studied as part of the EU-funded EUROSTRATAFORM project and the Norwegian

Research Council-funded SPONCOM project. Our aim within the EUROSTRATAFORM

project is to study the Andøya Canyon and its continuation into the deep-sea, the Lofoten

Basin Channel and an associated terminal fan (Fig. 1). In more detail our activities will focus

on three main aspects:

1) Canyon processes. The type of sediment transport into these systems is not known.

At present they may act as a trap for sediments winnowed and transported by

alongslope flowing ocean currents and/or they could be fed from upper slope mass

wasting. During glacial periods glacigenic sediments provided additional sediment

input.

2) Canyons and channels as pathways. Here the aim is to identify the type of

sedimentary processes transporting sediments through the canyon and channel, and to

the flanks of the channel (overbank deposits) and through the distributary channels on

the deep sea fan deposited at the channel mouth.

3) Products. We will study the volume, the stratigraphy and the sediment rate/flux of the

deep sea fan. Both canyon/channel systems represent modern analogue sandy deep sea

fans systems often found as reservoir rocks in the ancient record.

Within the strategic University project SPONCOM (Sedimentary Processes and Palaeo-

environment on Northern Continental Margins) led by Prof. Tore O. Vorren the results from

the Andøya Canyon and Lofoten Basin Channel area will feed into one of the four sub-goals

of SPONCOM: processes and fluxes of fjord, continental shelf and –slope sedimentation.

4

Fig

ure 1

: Ove

rvie

w m

ap of

the s

tudi

ed ar

eas.

5

The cores recovered from Balsfjorden will also be analysed as part of the SPONCOM project.

Previous investigations based on seismic and core data have demonstrated that the

Balsfjorden part of the Fennoscandian Ice Sheet withdrew from the Tromsø-Lyngen moraine

prior to 10.4 14C ka BP. The Skjevelnes moraine, crossing Balsfjorden at Skjevelnes and that

subdivides the fjord into an inner and an outer basin was deposited in the period from about

10.3 to 10.0 14C ka BP. The transition from a glacimarine to a marine fjord paleoenvironment

occurred at about 9.7 14C ka BP. The period immediately after the ice recession and up to

about 8.4 14C ka BP is characterised by a relatively high frequency of slide activity in

Balsfjorden.

The aims of the new core analyses are to reconstruct the Balsfjorden deglaciation history

more precise than previously possible. Also the post-glacial sliding activity will be studied in

more detail focusing on slide types, source area and more precise dating of the individual

events.

2. Cruise participants

In addition to the regular crew of R/V Jan Mayen under Captain John Almestad the cruise

participants were:

Jan Sverre Laberg, cruise leader, Post. Doc., University of Tromsø

Torbjørn Dahlgren, Post. Doc., University of Tromsø

Henrik Rasmussen, student, University of Tromsø

Steinar Iversen, science engineer, University of Tromsø

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3. Cruise narrative

Sunday 21.7. Departure from Tromsø at about 09:00 (local time). Cloudy and light breeze.

Sailing for two piston-core stations in Balsfjorden. From the first station piston core JM02-

803/1 of about 10.5 m length was obtained, from the second station core JM02-804/1 of about

11 m length was recovered (Table 1). The coring was ended at about 17:00. Then we sailed

for the continental slope west of the island of Andøya passing Hekkingen on our way. We

arrived at start position of the first seismic line across the Andøya Canyon at about 23:30.

Breeze and low to moderate sea.

Monday 22.7. Continued seismic profiling throughout the night and seismic profiles 02JM-

805, -806 and –807 were done (Table 2). Then we started profiling 02JM-808 during which

we had some small technical problems with the recording PC. The problems were fixed

within the next hour. The weather was fine, cloudy and light breeze. The seismic profiles

02JM-808, -809, -810 and –811 were done during the afternoon and evening. The profiles

were of good quality.

Tuesday 23.7. Cloudy and light breeze. We continued seismic profiling during the night, the

morning and afternoon and got good quality seismic data across the Andøya Canyon and

uppermost part of the Lofoten Basin Channel. In the northeasternmost part of the Lofoten

Basin the penetration of the sleeve-guns is up to 500 ms (twt) (profile 02JM-816). Seismic

profile 02JM-816 was finished at about 14:00. The sleeve-guns and streamer were recovered

for control while sailing for the next seismic profile.

Wednesday 24.7. Cloudy and breeze. We did two gravity core stations during the night,

02JM-818/1 where we got a 2.0 m long core and 02JM-819/1 were a sample of 2.93 m length

was recovered (Table 1), both cores from channel levée deposits. Then we steamed for the

start of the next seismic profile, 02JM-820 starting at about 08:00. Seismic profiling

continued during the day. The wind grew to up to Gail, the quality of the data was still good.

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Thursday 25.7. The weather was cloudy with light breeze. Seismic line 02JM-821 was

terminated at about 08:00. Then we continued with two gravity core stations positioned on

possible levée deposits identified on the line (Table 1). Despite two attempts at each station,

no sediments were recovered. Mud on the corer showed that it had reached the sea floor and it

is not known why sediments were not recovered from gravity core stations 02JM-822 and –

823. Then we continued with seismic profile 02JM-824. The sleeve-gun record was

interrupted for half an hour due to a small air leakage.

Core station

Area

Latitude

Longitude

Equip-

ment

Pene-

tration

Core

length

Water

depth

JM02-803/1 Balsfjorden 69o18.113 19o22.185 PC >12.0 m 10.37 m 124 m

JM02-804/1 Balsfjorden 69o23.909 19o01.856 PC >12.0 m 10.98 m 191 m

JM02-818/1 Lofoten Basin

Channel 69o53.58 13o59.84 G C > 6 m 2.0 m 2585 m

JM02-819/1 Lofoten Basin

Channel 69o45.45 13o59.99 G C > 6 m 2.93 m 2604 m

JM00-822/1 Lofoten Basin

Channel 69o17.301 11o25.899 G C > 6 m 0 m 2925 m

JM02-823/1 Lofoten Basin

Channel 69o20.590 11o19.010 G C > 6 m 0 m 2932 m

Table 1: Location of gravity and piston core stations of the cruise. PC = piston corer,

GC = gravity corer.

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Friday 26.7. A cloudy day with breeze from the south. Seismic profile 02JM-824 was

finished during the night. Then we had a three-hour passage to the start position of the next

profile. At the start of the next profile we had air leakage problems that was fixed and we

could continue. The profile (02JM-825) started on the distal part of the Trænadjupet Slide

running north and crossing the Lofoten Basin Channel (Fig. 1).

Saturday 27.7. Cloudy, rain, Gail. End of line 02JM-826 at about 02:00. 3.5 kHz profile of

good quality, sleeve-gun record of moderate quality due to the weather conditions. Seismic

profile –826 was the last profile acquired on this cruise, after finishing that profile we sailed

for Tromsø. We docked in Tromsø at about 22:00.

Sunday 28.7. All the seismic and sampling equipment together with the gravity core samples

was brought on shore.

4. Geophysical and geological equipment

4.1. Airgun array

An airgun array of two 0,6 l sleeve guns was used as source for the seismic survey. The

two guns were secured in a steel frame (distance between them: ~1 m) (Figure 2). The array

was towed approximately 25-30 m behind the vessel at a water depth of about 4 m below the

sea surface. With a firing pressure of 130 - 140 bar and a shooting rate of about 10 sec (see

Table 2 for more details), both guns were triggered with a small time offset to obtain a sharp

and mostly spiked seismic source signal. Values for the trigger offset varied between 0.1 – 0.7

millisec. A Fjord Instruments single channel Mini-streamer was used for the seismic signal

aquisition (Figure 3). The seismic records revealed a penetration of up to 0.5s TWT (Two

Way Traveltime). The signal-noise ratio was very good and the overall quality of the records

was high.

9

Figure 2: The two sleeve guns in its steel frame with the floating sled behind.

Figure 3: The Fjord Instruments streamer used for seismic signal acquisition.

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4.2 3.5 Hz Echo sounder

3,5 kHz Echosounder records have been acquired simultanously to airgun profiling. The

principal aims are: (1) To image the morphology of the ocean floor and its shallow subbottom

sedimentary layers and structures and (2) to select sediment core stations. The penetration

was up to 40 millisec TWT.

4.3 Onboard analogue and digital recording

Data were recorded analogue on an EPC 9800 Recorder, the filter setting of the Geopulse

Receiver for the air gun system was 100-700 Hz and for the 3,5 kHz Echo sounder 3-3,6 kHz

(see Table 2 for more details). The raw data was stored on hard disk using a Delph2

recording/processing unit on a Windows-based PC. The sampling frequencies were 2 kHz for

the air gun system and 12 kHz for the 3,5 kHz Echo sounder.

4.4 Geological equipment

For coring a piston corer and a gravity corer were used. The piston corer was operated with a

12 m steel pipe and a 110 mm inner PVC liner (Figure 4). The total weight of this corer is

about 2200 kg. The gravity corer has a total weight of about 1950 kg. It is operated with a 6 m

steel pipe with 110 mm diameter inner PVC liner (Figure 5). The gravity corer was operated

through a trunk in the vessel.

5. Preliminary results

5.1 Balsfjorden (by Matthias Forwick)

Based on density logs acquired by Multi-Sensor-Core-Logging and X-radiographs, a

preliminary stratigraphy for the piston cores JM02-803/1 and JM02-804/1 was established

(Figs. 6 - 9). Core JM03-803/1-PC was divided into five lithological units (Fig. 8). The

uppermost unit of the core, unit I (0 – c. 330 cm), comprises relatively homogenous sediments

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Figure 4: The 12 m long piston corer.

with high fossil content. In unit II (c. 330 cm – c. 460 cm), three gravity flow

deposits,separated by homogenous sections without fossil content, can be distinguished.

Homogenous sediments with high fossil content (unit III, c. 460 cm – c. 540 cm) underlie the

gravity flow deposits. The lithological composition of units III and I appear to be very similar.

Unit IV (c. 540 cm – c. 1000 cm) comprises partly deformed laminated sediments with some

clasts. A diamictic composition characterises the lowermost unit of the core, unit V (c. 1000

cm – 1038 cm).

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Core JM02-804/1-PC can be divided into eight lithological units (Fig. 9). Unit I, ranging from

the top of the core to c. 240 cm, is composed of homogenous sediments with many fossils.

The underlying unit II (c. 240 cm – c. 280 cm) comprises most probably a gravity flow

deposit that covers a diamicton (unit III, c. 280 cm – c. 370 cm). Another gravity flow deposit

(unit IV, c. 370 cm – c. 400 cm) underlies the diamicton. Unit V (c. 400 cm – c. 520 cm) is

composed of homogenous sediments with some clasts. This unit contains very little evidence

of organic activity. A deformed layered diamicton with shells in the upper parts defines unit

VI (c. 520 cm – c. 580 cm). Within the lower half of the core, homogenous sediments with

very few coarser grains (unit VII, c. 580 cm – c. 980 cm) overly unit VIII (c. 980 cm – 1096

cm) that is characterised by a generally coarser lithology and higher amounts of clasts.

Future work on the cores will include a detailed description of the X-radiographs and open-

core sections. In addition, the lithological composition of the defined units has to be

determined and the various types of gravity flows, archived in the cores, have to be identified.

Furthermore, radiocarbon datings have to be performed, in order to establish a general

chronology for the cores, as well as to date the mass-movements events.

5.2 The Andøya Canyon and the Lofoten Basin Channel

A total of about 630 km of high-resolution sleeve gun data together with 3.5 kHz profiles

were acquired from the area of the Andøya Canyon and the Lofoten Basin Channel (Figure 1

and 10). The upper part of the canyon is characterised by a V-formed cross-section and

maximum width between its shoulders is about 8 km. In this area, where the canyon incision

is about 1100 m there is little evidence of large-scale mass wasting along the canyon walls

(Figure 11). Further downslope the canyon has a more U-shaped cross-section, it is up to 25

km wide and 900 m deep. Here sliding and slumping is evident along the canyon walls

(Figure 12).

In the Lofoten Basin the Andøya Canyon continues as the Lofoten Basin Channel (Figure 1).

Downslope from the canyon, in the area were the channel makes a 90o turn southwestward, a

13

Figure 5: The 6m long gravity corer operated through a trunk in the vessel.

thick acoustically laminated unit inferred to represent levée deposits have been identified on

the northeastern flank of the channel (Figure 13). In this area the channel is about 100 m deep

and 5 km wide (Figure 13). Further into the basin channel levée deposits were cored (Figure

14). These cores have so far not been opened and analysed. In the area immediately north of

the Trænadjupet Slide deposits the channel is about 10 m deep and 1 km wide. In this area

levée development seems to have been restricted (Figure 15).

14

15

16

17

JM02-803/1-PC

1.50 1.70 1.90 2.10 2.30 2.500

1

3

5

7

9

11

2

4

6

8

10

12

Homogenous sedimentswith high fossil content

Homogenous sedimentswith high fossil content

Mass movement deposits

Laminated sediments,partly deformed,

some clasts

Diamicton

De

pth

in c

ore

[m]

Density [g/cm3] Unit

I

II

III

IV

V

Figure 8: Density log of core 02JM803, lithological division of the core (based on density log

and X-radiographs), as well as preliminary description or interpretation of the defined units.

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JM02-804/1-PC

1.50 1.70 1.90 2.10 2.30 2.50

Dep

th in

cor

e [m

]

Density [g/cm3] Unit

Homogenous,many fossils

Mass movement deposits?

Diamicton

Mass movement deposit?

Homogenous,some clasts,

very little evidenceof organic activity

deformed (folded) layereddiamicton; shells in the

lowermost part

homogenous,very few coarser grains

higher amount ofcoarser grains,

generally coarserlithology

I

II

III

IV

V

VI

VII

VIII

Figure 9: Density log of core 02JM804, lithological division of the core (based on density log

and X-radiographs), as well as preliminary description or interpretation of the defined units.

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15°20′ 15°40′ 16°00′

15°20′ 15°40′ 16°00′

69°30′

69°40′

69°50′

815

814

813812

811

810

809

808

807

806

805

LOFOTEN BASINCHANNEL

ANDØYACANYON

Figure 10: Location of the seismic profiles acquired from the Andøya Canyon area.

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5

km 600

800

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Fig

ure

11: S

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6511

8511

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23

JM02

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JM02

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ater

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ure

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24

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