Stratigraphy and Sedimentology of Middle to Upper Pleistocene Sediments in the New Grødeland Borehole at Jæren, SW Norway

Stratigraphy and sedimentology of Middle to Upper Pleistocene sediments in the new Grødeland borehole at Jæren, SW Norway

JURAJ JANOCKO, JON Y. LANDVIK, EILIV LARSEN & HANS PETTER SEJRUP

Janocko, J., Landvik, J. Y., Larsen, E. & Sejrup, H. P.: Stratigraphy and sedimentology of Middle to Upper Pleistocene sediments in the new Grødeland borehole at Jæren, SW Norway. Norsk Geologisk Tidsskrift, Vol. 77, pp. 87-100. Oslo 1997. ISSN 0029-196X.

The new Grødeland borehole penetrates 124.5 m of Pleistocene sediments at the coast of Jæren. Amino-acid analysis suggests that the succession is of Saalian to Weichselian age. Six major units dominated by tills, glaciomarine and marine deposits were recovered: Unit l rests on crystalline bedrock and comprises 42 m of subglacial till. Unit 2 comprises silty and sandy sediments deposited in a glaciomarine environment, grading into normal marine and back to glaciomarine conditions before deposition of the overlying till (unit 3). Unit 3 is 32 m thick subglacial till. Unit 4 was deposited in a shallow glaciomarine environment. The succession is capped by the uppermost subglacial till (unit 5) of assumed Early Weichselian age, and a Holocene beach deposit. The stratigraphy is compared with the classic results fr om the Grødeland coring carried out at this site in i874.

Jura} Janocko, University of Tromsø, Department of Geology, IBG, N -9037 Tromsø, Norway; Jon Y. Landvik, The University Courses on Svalbard (UNJS), PO Box 156, N-9170 Langyearbyen, Norway; Eiliv Larsen, Geological Survey of Norway, PO Box 3006, N-3006 Trondheim, Norway; Hans Petter Sejrup, University of Bergen, Department of Geology, A/legt. 41, N-5007 Bergen, Norway.

Relatively long and complex Quaternary stratigraphic in April 1993 and presented here, was located 50 m from records are documented from many parts of western the modem beach (UTM 32VLK021045) only 20 m Norway and from the North Sea (e.g. Andersen et al. southeast of the 1874 drilling that recorded 92 m of 1981; Mangerud et al. 1981; Landvik & Hamborg 1987; sediments (Bjørlykke 1908). Larsen et al. 1987; Larsen & Mangerud 1989; Larsen & The main objective of this article is to document the Sejrup 1990; Sejrup et al. 1987, 1989, 1991, 1994). The lithostratigraphy of the thick sedimentary succession at Jæren region (Fig. l) has a thick Quaternary cover, in Grødeland and reconstruct the depositional environ contrast to the rest of mainland Norway. The region has ments. Some preliminary results of chronological and been extensively studied since the turn of the century biostratigraphical work are also presented. (Bjørlykke 1908; Grimnes 1910; Feyling-Hansen 1964, 1966, 1971, 1974; Wangen 1968; Østmo 1971; Andersen et al. 1981, 1987; Fugelli 1992; Fugelli & Riis 1992). Methods Correlation between studied sites reveals a complex stratigraphy in the area (Andersen et al. 1987). The drilling was performed using a rotary system from a The Jæren region represents a border zone between the truck-mounted rig. Sampling by a wire-line system was North Sea shelf region and the Norwegian mainland, carried out in the fine-grained sediments. A stee1 sampler extending from Stavanger in the north to Ogna in the with plastic core barrel 150 cm long and 10 cm in south (Fig. 1). The region is divided into Lågjæren diameter was fixed in the front part of the drill string and (Lower Jæren) to the west, with elevations below 100 m, pushed down without rotation during drilling. After 150 and Høgjæren (Upper Jæren) to the east (Fig. l), reach cm of penetration, the coring was stopped and the sam ing up to 250 m a.s.l. In some areas the two parts are pler recovered using a wire-line retriever. Different core separated by a morphologically conspicuous step (Fig. catchers were used to prevent samples from sliding out of 2). The area east of a line passing through Ålgård, Lake the plastic barrel. Recovery in the fine-grained sediments Storamos and Brusand is dominated by exposed bedrock was 42%. During retrieval, sorted sand and silt some (Fig. 1). This crystalline basement comprises Precam times escaped from the sampler. On most occasions, a brian gneisses and granites ( anatexites ), anorthosites, fist-sized, often disturbed sample was preserved in the phyllites, mica schists and mica gneisses (Birkeland core catcher itself. In bouldery diamictons, a rock drill 198 1). bit was used and cores were not collected. Information Several coal exploration boreholes made in the second on these units was obtained by cutting samples from drill half of the last century revealed thick Quaternary de mud collected during every 3 m run. Sudden changes in posits (Bjørlykke 1908). The Grødeland borehole, drilled drill penetration indicate lithological changes, probably 88 J. Janocko et al. NORSK GEOLOGISK TIDSSKRIFT 77 (1997)

5°30' 5°45'

,...... -----,------=------.--=-�59°00'

Norwegian Sea

NORTH

SEA

Areas covered by Quatemary sediments Areas with exposed bedrock Grødeland drilling * Old Grødeland drilling Roods O Houses

Fig. l. Map of the Jæren area showing the location of the new Grødeland borehole. The indicated boreholes at Auestad, Elgane and Habberstad were drilled in 1994-95, and will be reported in future articles. The map showing areas with predominantly Quatemary deposits and exposed bedrock is constructed after Andersen et al. ( 1987). NORSK GEOLOGISK TIDSSKRIFT 77 (1997) Pleistocene stratigraphy and sedimentology, Jæren, SW Norway 89

Fig. 2. Oblique air photograph of southem Jæren showing its typical lowland character. Lågjæren area is separated from Høgjæren by the morphological step to the east of the town of Varhaug. See Fig. l for location.

between zones with diamictic and hetter sorted sedi Lithostratigraphy and interpretation ments. The unsplit core barrels were X-rayed while moving The drilling penetrated 124.5 m of Quaternary sediments them along their lang axis and rotating them, giving a befare encountering mica schist or mica gneiss of Pre three-dimensional image of sedimentary structures and cambrian age. The sedimentary succession is divided into contained clasts. The X-ray data were recorded on video six lithological units, numbered from bottom to top (Fig. tape and computer disks. After the cores were split, 3). The borehole contains two fine-grained sediment units sediments were visually described and photographed. separated by three thick diamictons. The succession is Samples were taken for determination of water content, capped by Holocene beach sediments. The different fa preconsolidation pressure (Hernes 1995), total carbon, cies are indicated in the log (Fig. 3) using lithofacies total organic carbon and CaC03, foraminifera, molluscs, codes (Table l) slightly modified after Eyles et al. (1983). grain-size analysis and palaeomagnetism (Løvlie 1994). Selected core intervals were sliced, transferred to plexi glass trays and X-rayed for more detailed inspection. Unit l Amino acid samples were prepared after the method described by Miller et al. ( 1983) and then run on an Description. - Unit l is the lowermost 42 m thick automatic ion exchange amino acid analyser at the diamicton (D) extending from 124.5 m to 82.2 m (Fig. 3). Bergen Amino Acid Laboratory (BAL). Two samples It has not been cored, and the information about de were dated by the AMS method at the Laboratory for posits comes from cutting samples and drilling log. Radiological Dating in Trondheim. Changes in penetration speed, observed during drilling, Clast fabric, shape and roundness (25 per sample) indicated boulders 'floating' in a finer matrix. The unit were measured in the uppermost 2.2 m of the succession consists of crystalline clasts up to boulder size, supported in a shallow pit next to the drilling site. Clast fabric was by a fine-grained matrix. Cutting samples occasionally measured on rock fragments between 2 and l O cm lang, contained mollusc fragments. However, their strati having an a/b-axis ratio of at least 1.5. Clast shape was graphic position is uncertain because they may have been calculated after Zingg ( 1935, in Pettijohn 1975). Round washed out from overlying deposits by the rising drill ness was estimated visually after Folk (1951). mud. 90 J. Janocko et al. NORSK GEOLOGISK TIDSSKRIFT 77 (1997)

0.0 9.5 51.5 6 o\ Fm ,-=-=--::::--=-=--=-::1. ® o ® Sh Fl {)rm 52.0 5 _1_ 10.0 �JSm • • ' ·�Gmm 52.5 +-___;;;....__--,_..--, ..- -� 5.0 �m o J Sg l Sm 10.5 53.0 ------t t -- Fl no recovery

SI 11.0 10.0 -'l. o Gmm Sg l*51 775�5145 oaooooøo�ooo_Q_o Gcm _ 3110 _'\"'Sg "-Gcm � •O. 087 11.5 o l 54 5 13.0 Cj o � �n . EiE�� 3 c sand gr011el 42.0 D '=:f::::::K/ Fl ._Q_ <> oJ - ss.o r-"· --�----"l cloy sil sand gravet

45.0

o "' Sm © 77.0 © 50.0 •===--==/ -'l. l���FISh ---- A ----- •=�=� �Fl ------Fl J�Sm 9 i -��"'i�,._ -'l. • o. 107 77. 7 .5 ::::;;::::.i. Fl • D. 153 osJ:===�Sh lf:ll..... ;;;;., ��- � l \.. 55.0 F o � Sm no recovery Oo oooaoooooo"'i;\ · --j,). Sh Fl ._ n 9 -1----,----,-'-I Sm • o. 124 . ___, 80.5 Fm � �n �nd Fm Fl c • o. 134 Fl ------c 153 • o. o Gmm 81_5 �=====:i�"; • 148 o. Fm • O. 078,0. 051 82.0 -E§�Fl *42 635± \6�g cloy sin 65.0 1':�-'l.Fm .o.�s �------;:::::::::::::::::::::::::::::::::::::::::::::::::::� l·.·:� -'l-Fl Leg end rJI==::::r.J\ -'l.Fl, Fm �==\o\ Massive strucltre Outsized clasts 70.0 Fl. Fm l D Horizontal lamlnaflon Mud l- • o. 142 § Faint lamlnaflon Sand • o. 166 Malrlx-supported 75.0 Trough cross-straflficaflon � grave! • o. 147 �-···GmmSh �__Æ; � Shell layer Clast-supported r1 grave! l-ll��t-...... -�� .f! • •• Gmm -,l 130 -----�·:.J -'l. .o. B Gravel layer Diamicton 80.0 m • � _j© ·-···· 136 Bed rock ,Fl Gmm • O. EJ Water escape structure ·i � •0.128 Boundary: 84.0 0 � Softsediment deformaflon a) shaiP D b) eroslve o = Moffied, bloturbated c) loaded l Core l\.,\., Preconsolldafion test � Core catcher mean Alle/lie raflo • o. 102 Mollusc fragment NORSK GEOLOGISK TIDSSKRIFT 77 (1997) Pleistocene stratigraphy and sedimentology, Jæren, SW Norway 91

Table l. Facies codes, slightly modified after Eyles et al. ( 1983). Subunit 2-2 (78.6 m to 68.0 m) is generally more coarse-grained than underlying subunit 2-1. The lower Dmm Diamicton, matrix-supported D Diamicton boundary is sharp and emphasized by a bed of matrix Gmm Grave!, matrix-supported, massive supported gra vel ( facies Gmm). The subunit is typically Gcm Grave!, clast-supported, massive composed of repeated facies arranged in stacked, usually Sm Massive sand St Trough cross-bedded sand graded, sharp-based beds up to 40 cm thick. Molluscs Sh Sand, horizontally laminated, faintly laminated occur frequently, and the total carbon, organic carbon Sg Graded sand and the calcium carbonate content is lower than 0.5% Fm Massive sand Fl Silt, laminated, faintly laminated (Fig. 4). The upper part of the subunit has an upward fining trend (Fig. 3). A typical facies succession consists of five superimposed facies. Matrix-supported gravel (facies Gmm) consists of Interpretation. - Sparse information from the drill mud small, up to 2 cm diameter, crystalline, subangular clasts. and drill logs does not allow a detailed interpretation of The matrix is composed of coarse sand. The sediment the sediment. The bouldery character of the sediment, contains large amounts of crushed mollusc shells. Facies together with its stratigraphic position immediately be Sm (Figs. 3C and 6) consists of massive, coarse sand low glaciomarine sediments of unit 2, suggests a glacial occurring mostly at the base of the facies succession. The origin. However, we cannot exclude the existence of overlying facies Sh is composed of horizontal laminated, thinner hetter sorted beds within unit l. occasionally normal graded medium to fine sand. The laminae are 2-3 mm thick. The facies succession is capped by horizontal laminated (laminae 1-2 mm thick) Unit 2 coarse silt (facies Fl), sometimes strongly bioturbated

Description. - Unit 2 extends from 82.2 m to 42.5 m and homogenized to massive silt (facies Fm). Because of (Fig. 3). It contains sediments varying from fine silt to erosion, often only the lower or the middle part of the coarse sand. Matrix-supported grave! layers occur occa whole succession is preserved. Poor recovery in the sub sionally. The whole unit has a dark grey colour. Three unit does not allow complete observation of the vertical subunits are distinguished on the basis of grain size, sediment development. However, a few cores from the occurrence of outsized clasts and sedimentary structures lower part of the subunit (77 m, 75.5 m and 74 m) show (Fig. 3). the occurrence of facies Gmm, Sm and Sh arranged in stacked, erosively based beds. In the upper part of the (l) Subunit 2-1 (82.2 m to 78.6 m) is composed mainly subunit ( cores from 69.5 and 68 m, Fig. 3) facies Sh of coarse silt. The contents of calcium carbonate and passes into Fl and Fm. total and organic carbon are relatively high com In the middle to upper part of subunit 2-2 the sedi pared to overlying sediments (Fig. 4). The sediments ment recovery was low. Judging from the lowermost part contain angular to rounded clasts up to 3 cm in of the unit, two core samples, and supported by the diameter and occasionally broken fragments of experience that sorted sand tends to escape from the shells. Three facies are recognized in the subunit sampling tube, we assume that this part consists of sand (Fig. 30). and silt. The core samples from the uppermost part of (2) Facies Fm is composed of coarse-grained massive silt the subunit contain massive and laminated sandy silt, in up to 115 cm thick beds. The silt contains scat suggesting upward-fining trend of the subunit. tered clasts and rare mollusc fragments. Subunit 2-3 (68.0 to 42.5 m) is mostly composed of silt (3) Facies Fl consists of horizontally laminated, occa in the lower and middle part and sand in the uppermost sionally faintly laminated, coarse to fine silt with part (Fig. 3). The content of total carbon, total organic outsized clast occurrence. The laminae are ca. l mm carbon and calcium carbonate is slightly higher than in thick. The facies occurs either in 10-20 cm thick underlying subunit 2-2 (Fig. 4). Mollusc fragments and beds with diffuse boundaries or in sharply based, outsized clasts are found throughout the subunit, and stacked, upward-fining beds up to 40 cm thick (Fig. outsized clasts are more frequent above 55 m. Four facies 5). (Fl, Fm, Gmm and Sm) are recognized (Fig. 3). Horizontally laminated, occasionally faintly laminated Matrix-supported massive grave! (facies Gmm), con silt ( facies Fl), occurring in sharply based beds with sisting of crystalline subangular and angular clasts up to thickness from 10 cm to l m, dominates. Laminations, l 4 cm in diameter and silty matrix, occurs only in one bed to 5 mm thick, consist of alternations of fine and coarse at 81.4 m depth. It passes upward into Fl facies (Fig. 3). silt. Normal grading can be observed in the coarser

Fig. 3. Lithostratigraphical log of the new Grødeland core. Enlargements of parts of the log are also shown (A-D). Note the compressed scale in the two diamictons ( units l and 3). 50.0 50.0 50.0 50.0

55.0 55.0 55.0 55.0 l�

60.0 2 60.0 60.0 60.0

65.0 65.0 65.0 65.0

70.0 70.0 70.0 70.0 70.0

l� 75.0 75.0 75.0 75.0 75.0

80.0 "' 80.0 80.0 80.0

84.0 84.0 84.0 84.0 84.0 84.0 84.0 l .... "''U ::::L 122.0 122.0 122.0 122.0 L 125.0 125.0 125.0 125.0 MUD SAND GAAVEL 125.0 125.0

m NORSK GEOLOGISK TIDSSKRIFT 77 (1997) Pleistocene stratigraphy and sedimentology, Jæren, SW Norway 93

78,84 m 74,03

79,02 m

Fig. 5. Photograph of coarse to medium silt from the upper part of subunit 2-1. 74,23 The horizontally laminated silt fines upward.

Fig. 6. Photograph of facies Sm and Fm of subunit 2-2. Facies Fm is strongly bioturbated. laminae. Fragments of molluscs are frequent and mott ling caused by bioturbation, water escape and loading is are of crystalline origin and are angular to sub common. The deposit occasionally has an upward-fining rounded. or upward-coarsening trend. When upward tining, the Recovery in the uppermost part of subunit 2-3 is very frequency of lamination increases towards the top of the poor (Fig. 3). The core from 48.5 m and cutting samples bed. from 47, 45.5 and 44 m suggest that the sediment is Massive coarse and medium silt (facies Fm), arranged composed mainly of fine to coarse sand with outsized in cm to 1.2 m thick beds with diffuse boundaries, l O clasts. interfingers with sediments of facies Fl. Mollusc frag ments occur occasionally. The sediment is churned by bioturbation and soft sediment deformation is very com Interpretation mon. A sharply based bed consisting of massive, matrix-sup Subunit 2-1: Chaotically distributed outsized clasts ported grave! (facies Gmm) occurs at 52.5-52.3 m (Fig. within a silty matrix are interpreted as iceberg-drop 3B). Clasts of crystalline origin with maximum size 4 cm material. The presence of arctic foraminiferal species (see are subangular to subrounded. The matrix consists of a below) supports an interpretation of deposition under silt-sand rnixture. glaciomarine conditions. Upward-fining facies Fl suggest Massive, coarse sand (facies Sm) containing outsized deposition from turbidity currents, probably forming on clasts was recovered in a short core at 48.5 m. The clasts a relatively steep slope with high sedimentation rate in

Fig. 4. Lithostratigraphical column of the Grødeland drilling showing grain-size distribution, water content, calcium carbonate content (CaC03), total (TC) and organic (TOC) carbon, and number of foraminifera per gram sediment. 94 J. Janocko et al. NORSK GEOLOGISK TIDSSKRIFT 77 (I997) the proximal area of a glacier terminus (Powell 1984; graded beds of facies Fl suggest a change of process from Boulton 1990; Lønne 1995). The presence of only upper suspension to current traction. Facies Fm is the result of parts of a classical turbidite sequence (Bouma 1962; Stow suspension sedimentation and/or homogenization of Fl & Shanmugan 1980; Porebski et al. 1991) suggests depo facies by bioturbation. The matrix-supported gravel of sition from tails of turbidity currents. The gravel bed at Gmm facies is thought to have been deposited by a 81.45 m, at the base of facies Fl, may have been de debris flow. Prevailing sand in the uppermost part of the posited by a traction current during higher energy condi subunit (co re sample from 48.5 m and in the cutting tions. The uniformity of the Fm facies suggests prevailing samples) indicates the change of glacier distal to a more suspension sedimentation and a constant supply of mate glacier proximal environment. rial. Subunit 2-2: Normal graded beds comprising the com plete or only part of facies succession Gmm - Sm - Sh Unit 3 - Fl are thought to be storm-generated, deposited under waning storm generated flow. They resemble a typical Description. - Unit 3 is a ca. 30 m thick diamicton tempestite succession described from the southeastern extending from 42.5 m to 12.0 m. Cutting samples from North Sea and Washington Shelf consisting of a coarse the base of the unit (42. 5-36.0 m) revealed gravel with a layer with reworked shells above an erosive base, fol- matrix composed of a clay-silt-sand mixture. Subangu 1owed by massive, horizontal and wave rippled lamina lar gravel clasts are of crystalline origin. Some shell tion, and capped by a mud blanket (Nittrouer & fragments occur. From 36 m to 32 m the sediment Sternberg 1981; Aigner & Reineck 1982). Because of a consists of large boulders supported by silty sand which, high degree of amalgamation, the upper wave-rippled in turn, is overlain at 21 m by sorted gravel with shell division and mud blanket is often lacking in proximal fragments. The interval from 21 m to 12 m is composed tempestites (Aigner & Reineck 1982). Similar sediments of a bouldery sediment with a clay-silt-sand matrix. formed in storm-dominated environments have been de Four samples from unit 2 were tested for preconsolida scribed by Duke (1990), Duke et al. (1991) and Swift & tion (Fig. 3). The preconsolidation values were all be Thorn ( 1991). Gmm, Sm and Sh facies preferentially tween 4 and 5 MPa, suggesting that the minimum ice preserved in the lower part of the subunit record progres thickness of the largest overriding glacier was some 530 sive sorting in a proximal position when much of the m (Hernes 1993). upper, finer portion of the original bed has been re-en trained during the next flow event and deposited further Interpretation. - The diamictic character of the sediment, offshore. This is often described from the nearshore zone poorly sorted matrix, subangular shape of clasts and (Aigner & Reineck 1982; Duke 1990). The Fl and Fm character of overlying and underlying units suggests a facies, representing the uppermost part of the succession, glacia1 origin for at least part of unit 3. The changes in has probably been deposited in a lower energy environ lithology, as indicated by cutting samples and drill pene ment in the offshore-transition zone. The upward-fining tration, suggest more than one till bed and perhaps also trend in the upper part of subunit 2-2 and facies Fl, Fm other genetic types of sediments. found only in core samples from the upper part of the subunit suggest increasing depositional depth and a marine transgression during sedimentation. The recent Unit 4 mean wave height offshore the Jæren region varies from

2.5 to 1.5 m; maximum wave height is 10 to 12 m (Elde Description. - The sediments between 12.0 m and 2.3 m et al. 1986). The inferred depth for initiation of sediment are mainly composed of sand with minor silt beds. A motion by waves of this height is about 30 m (W eggel high content of outsized clasts and mollusc fragments 1972; Nittrouer & Sternberg 1981). This implies deposi prevails throughout the entire unit. The following facies tion of Fl facies, prevailing in the upper part of subunit can be indentified in unit 4 (Fig. 3). 2-2, at about 30 m depth, if the wave parameters were Massive, matrix-supported gravel (facies Gmm) con the same. sists of angular and subangular crystalline clasts up to 3 The depositional environment and the absence of cm in diameter, scattered in the sandy matrix. Massive, dropstones suggests that subunit 2-2 was deposited under clast-supported gravel (facies Gcm) occurs only in one normal marine conditions, and that sedimentation was erosional-based bed associated with facies of graded sand not directly influenced by g1aciers. (facies Sg) and massive silt (facies Fm). Gravel clasts of Subunit 2-3: The presence of outsized clasts, inter crystalline origin are subangular with an average size of preted as dropstones, suggests deposition in a glacio 2 cm. Graded, coarse to fine sand (facies Sg) reveals marine environment. Deposits of facies Fl reflect prevail normal and inverse grading. It is often associated with ing deposition from fluctuating suspension clouds. It is facies Sh and Fm, forming beds with sharp bases. Facies possible that some of the beds with upward-fining Fl Sm is represented by massive, fine to coarse sand ar facies, frequent loading and water escape structures rep ranged in 10 to 20 cm thick, sharp-based beds. Facies St resent the tail parts of fine-grained turbidites. The inverse (Fig. 7), observed in an excavation 15 m from the drilling NORSK GEOLOGISK TIDSSKRIFT 77 ( 1997) Pleistocene stratigraphy and sedimentology, Jæren, SW Norway 95

n = 47

n = 26

Fig. 7. Excavation pit showing the upper part of unit 4 sand (facies St) and overlying till (facies Drnm) of unit 5. Note the loaded lower boundary of the till in the Jower part of the picture. Two fabric diagrams are also shown. The width of the compass is 6 cm.

site, consists of trough cross-stratified medium sand 7). The diamicton, studied in the excavation 15 m from which directly underlies the diamicton of unit 5. Facies the borehole, is matrix-supported, massive, and consists Fm comprises massive, occasionally deformed coarse silt. of subangular, occasionally subrounded clasts of crys Silt beds usually form ca. 10 cm thick sharp-based inter talline origin (facies Dmm). The matrix is composed of a calations between sand facies, or comprise the upper part very poorly sorted mixture of clay, silt and sand of graded beds, associated with Sm and Sh facies (Fig. (Md = 1.8 Ø, a= 3.18) of dark grey colour. The base of 3A). the diamicton bed is loaded. Cobbles and boulders often form elongated clusters. Maximum clast diameter is 0.4 Interpretation. - The structures and lithology of unit 4 m. Many clast surfaces are striated. Clast fabric analyses suggest deposition in a high energy environment. The were performed in the lower and upper part of the unit. presence of mollusc shells, foraminifera and outsized The analysis in the lower part shows a preferred NW- SE clasts, interpreted as dropstones, strong1y suggests depo orientation and a low dip of the longest axes. Clast fabric sition in a glaciomarine environment. Graded beds com from the upper part of the diamicton has not preferred prising gra vel at the base ( Gcm), overlain by graded sand orientation (Fig. 7). (Sg) and massive silt (Fm), as well as Gmm facies, suggest deposition from traction currents. Trough cross Interpretation. - The diamictic character of the sediment, stratified sand (St) at the top of the unit indicates matrix-supported structure, poorly sorted matrix, suban deposition in a shallow marine environment above wave gular clasts and clast striations indicate a subglacial base. The coarse-grained sediment in the entire unit origin for unit 5. suggests deposition in a proximal glaciomarine environ ment.

Unit 6 5 Unit The entire sediment sequence of the Grødeland drilling is

Description. - Unit 5 is represented by the uppermost capped by a 0.8 m thick layer of Holocene cobbly to diamicton layer, extending from 2.3 to 0.8 m (Figs. 3 and bouldery beach sediments. 96 J. Janocko et al. NORSK GEOLOGISK TIDSSKRIFT 77 (1997)

F oraminifer a Comparison of the new Grødeland stratigraphy with the old Grødeland coring Core catcher samples from units 2 and unit 4 in the Grødeland coring have been analysed for foraminifera. The old Grødeland drilling, performed in 1874, is located A more detailed study of the foraminiferal stratigraphy only 20 m from the new borehole (Fig. 1). The sediments from three sediment cores is now being conducted (M. recovered by this drilling consist of a 13 m thick layer of Iversen, thesis, in prep.). The faunas are dominated by cobbly clay overlain by 32 m sand, which in turn is species like Elphidium excavatum (Terquem), Cassidulina overlain by a 44 m thick layer of grave! and sand. The reniforme Norvang and Nonion orbiculare (Brady), and whole succession is capped by a 3 m thick clayey till (Fig. resemble faunas found in shallow waters in arctic seas 8, cf. Andersen et al. 1987). Analysis of foraminifera today (Loeblich & Tappan 1953; Nagy 1965; Sejrup & from the lowermost clay indicated an age older than the Guilbault 1979). Until the exception of the regular oc Sandnes interstadial of Late Weichselian age (Feyling currence of Elphidium ustulatum Todd in unit 2, no Hanssen 1971; Andersen et al. 1987). A comparison with extinct foraminiferal species were recorded. In subunits the new core shows general agreement between the litho 2-1 and 2-4 and in unit 4 very low diversity faunas logical units in the two boreholes. However, improved with high frequencies of Elphidium excavatum were drilling methods rendered a more detailed subdivision of found. Such faunas are common in extreme environ the sediments recovered by the new drilling. On the basis ments influenced by glacial activity (Hald et al. 1994; of lithology and depth, it is possible to corre1ate sedi Nagy 1965; Osterman 1987). Subunits 2-2 and 2-3 ex ments between the boreholes (Fig. 8). hibit more diverse assemblages indicative of normal The 1o wermost cobbly clay in the old borehole, with marine conditions. Also a few species which suggest an upper boundary at 79 m, is corre1a ted with our somewhat higher temperatures (e.g. Bulimina marginata diarnicton unit l, with an upper boundary at 82 m. The d'Orbigny, Cassidulina laevigata d'Orbigny and Elphid depth to bedrock was reported at 92 m in the old ium albiumbilicatum (Weiss) are found in these parts of boreho1e (cf. Andersen et al. 1987). However, the corre the sequence. Similar faunas to those recorded so far sponding depth of 124.5 m in the new drilling suggests in the Grødeland coring have been recorded at several that the old drilling probably stopped at a large boulder other sites with Late Pleistocene sediments on Jæren in unit l till. (Feyling-Hanssen 1971, 1974; Andersen et al. 1987) and from other parts of western Norway (Mangerud et al. Old Grøde/and New Grøde/and 1981; Sejrup 1987). borehole borehole o �C:J�--o--o� 015 ----- ...... 1O o· : ...o . a. : . . ·o . 10 4 ::: Geochronology 20 o o A dating programme, including AMS dating and amino-acid geochronology, is in progress. Preliminary 30 o ...... o results of the amino-acid analyses give rough estimates . .. o . on the geochronology of the deposits. Arnino-acid ::::::: ?: : 9 o 40 . . . :":o::. analyses have been carried out on seven monospecific ...... o:::::o-- samples of the benthic foraminifera Elphidium excava 50 50 tum from 24 samples from unit 2 and one sample from unit 4 (Fig. 3). The samples from unit 2 yielded mean 60 60 alle/Ile ratio in the total fraction of 0.130 ± 0.02 and ...... the single run from unit 4 gave 0.087. If these prelimi 70 ...... 70 ...... nary analyses are compared with ratios obtained on ...... sites from the North Sea and adjacent land areas 80 ----80 o o (Knudsen & Sejrup 1988; Sejrup et al. 1995), an age C) o o o close to oxygen isotope stage 7 is suggested for unit 2 90 C) 90 o and Early Weichselian for unit 4. An Eemian or older age for unit 2 is indicated by the appearance of the 100 o gravel and sand o benthic foraminiferal species Elphidium ustulatum (see � o sand Gregory & Bridge 1979). Radiocarbon dating (AMS o 110 mud o o method) performed on two mollusc shell samples o IQJ diamicton o yielded an age 42,635 for the sample from unit 2 (63.6 120 o • recent beach sediment m depth) and an age of 51,775 for the sample from Unils unit 4 ( 11.07 m depth). Both dates are above the range Fig. 8. Correlation between the old Grødeland borehole made in 1874 and the of radiocarbon dating suggesting an even older age for new borehole. Sedimentary succession in the old borehole after Andersen et al. the samples. (1987). NORSK GEOLOGISK TIDSSKRIFT 77 ( 1997) Pleistocene stratigraphy and sedimentology, Jæren, SW Norway 97

The sandy interval, penetrated in the old borehole (e.g. Mangerud & Svendsen 1992; Lyså & Landvik from 47 to 79 m is very likely the counterpart of unit 2 1994). in the new borehole extending from 42.5 to 82 m. As the sediments in the old drilling were retrieved by a flushing technique, they probably lost the fine-grained portion of Subunit 2-2: Open marine conditions the deposits, and the sediments were reported as more coarse-grained than they really are. An abrupt shift in style of sedimentation between subunit The grave] and sand, revealed from 3 to 47 m in the 2-1 and 2-2 indicates a drop in sea level (Figs. 3 and 9). old drilling, can be correlated with units 4 ( diarnicton) Relatively fine-grained sediments in subunit 2-1 pass into and 5 ( mostly sand) in the new drilling. sediments consisting of several storm-induced cycles de The uppermost clayey till in the old well, with the base posited well above storm- wave base. The upward-fining at 3 m, is thought to be equivalent to till unit 5 in the trend in the upper part of the subunit points to a new drilling (Fig. 8). progressively increasing depositional depth in a storm dominated environment. The main sediment source was probably reworked sediment from the shore zone during a transgression. The structure and grain size of the Glacial and environmental history sediments point to deposition under normal marine con The long record from Grødeland gives considerable in ditions without glacier influence. This is in accordance sight into the environmental history of the last two or with the result of the biostratigraphical investigations more glacial cycles and is probably the longest Quater which show more normal marine assemblages with bo nary stratigraphic record retrieved so far from any area real components. of mainland Norway. The only exception may be the oldest till and waterlain units from Finnmarksvidda, northern Norway (Olsen & Selvik 1995). At Grødeland, Subunit 2-3: Glaciomarine conditions at ]east three diarnicton layers separating finer units The normal marine deposits of subunit 2-2 pass gradu demonstrate a minimum of three periods of glaciation ally into finer deposits of subunit 2-3. The lithology of with two intervening ice-free periods. The geological the younger sediments (Figs. 3 and 4) indicates a gradual history inferred from the sedimentary record is discussed change in the sedimentary environment. Dropstones can in stratigraphic order. be observed from 67.5 m upward, indicating a glacier advance into the marine environment and a transition from normal marine to glaciomarine sedimentation (Fig. Unit l: Glaciation 9). The upward-fining trend, continuing from underlying The lowermost diamictic unit resting directly on bedrock subunit 2-2, can be traced to 61 m depth and probably (Fig. 3) and interpreted as till represents the oldest reflects continuing sea-level rise. The coarsening-upward glaciation recorded in the Jæren area (Fig. 9). Owing to trend of laminated silt of facies Fl deposited during sparse information, it is not possible to determine higher energy conditions indicates increasing proximity whether this unit represents one or more glacial episodes. of a glacier. The traction currents are probably associ Amino-acid ratios from the overlying unit 2 suggest an ated with high melt-water flux from a glacier terminus age close to oxygen isotope stage 7 for unit l. causing underflow. Debris flows reflect a high sedimenta tion rate, which is typical for an ice proximal environ ment, for instance on ice-contact subaqueous fans (Lønne 1995). Increased proximity of the glacier is also Subunit 2 -l: Glaciomarine conditions suggested by the foraminiferal content, which shows an The Iowermost till is overlain by sediments deposited in extremely high occurrence of arctic species tolerant of a glaciomarine and marine environment. In the lower low salinity and turbid water masses. part (subunit 2-1), sedimentation in a glaciomarine envi ronment is shown by a high frequency of dropstones. The presence of turbidite and debris flow deposits points Unit 3: G/aciation to an unstable zone occurring probably in the glacier proximal areas (Fig. 9). The absence of wave-generated Increasing proximity of the glacier as deduced from structures suggests deposition below a wave base. The subunit 2-3 was eventually followed by glacier overriding arctic foraminiferal assemblage consists of species that and till deposition (unit 3, Fig. 9). The character of the can tolerate low salinity and turbid water masses. Sedi diamicton, consisting of layers having variable lithology ment characteristics and faunistic evidence support the and intervening zones of sorted sediments, suggests a conclusion that subunit 2-1 was deposited during a de possible complex history, perhaps with several episodes glaciation phase after deposition of the underlying till. of glacier advance and retreat. Preliminary amino-acid Similar deglacial successions with till directly overlain by analyses suggesting the deposition of unit 2 close to glaciomarine sediments are common on glaciated coasts isotope stage 7 and deposition of unit 4 during the Early 98 J. Janocko et al. NORSK GEOLOGISK TIDSSKRIFT 77 (I997)

Unit l time: Unit 3 time:

Subunit 2-1 time: Unit 4 time:

Retreat ...___

Subunit 2-2 time: Unit 5 time:

Subunit 2-3 time:

unit 1 - diamicton 2-1 subunit 2-1 sediments - mostly silt 2-2 subunit 2-2 sediments - sand and silt 2-3 subunit 2-3 sediments - silt and sand 3 unit 3 - diamicton 4 unit 4 - mostly sand 5 unit 5 - diamicton location of drilling bed rock sea glacier ice NORSK GEOLOGISK TIDSSKRIFT 77 (1997) Pleistocene stratigraphy and sedimentology, Jæren, SW Norway 99

Weichselian point to deposition of unit 3 some time continuous sedimentation history, from glacier-free (sub between the Saalian and the Early Weichselian. Accord unit 2-2) sedimentation to deposition under glacial condi ingly, the lack of marine Eemian sediments may be due tions (unit 3). Amino-acid analyses from unit 2 indicate either to non-recovery of this interval or to subsequent an age close to isotope stage 7. Unit 3 was deposited glacial erosion. during a glacier advance. The multilayer character of this unit and the large time span of sedimentation, from the Saalian to Early Weichselian, suggest several glacier ad Unit 4: Glaciomarine conditions vances and retreats during its deposition. Sedimentation under glacial conditions was succeeded by glaciomarine Diamictic unit 3 is overlain by mostly sand and gravel of sedimentation in the Early Weichselian. The sandy sedi unit 4, deposited in a glaciomarine environment (Fig. 9). ments of unit 4 were deposited in a glacier proximal The fabric and texture of the sediments indicate deposi environment, while unit 5 was deposited by a glacier tion under high-energy conditions typical for proximal advance sometime before the Late Weichselian. glaciomarine sedimentation near a glacier terminus (Powell 1984; Lønne 1993, 1995). Preliminary amino-acid Acknowledgements. - The work was financially supported by the Research analyses suggest deposition during an Early Weichselian Council of Norway (NFR) and Norsk Agip a.s. The analytical part was carried interstadial. out at the University of Tromsø, and foraminiferal analyses at the University of Bergen. Amino-acid analyses were performed at the Bergen Amino Acid Labora tory (BAL). Skilful drilling by Poul Christiansen a.s., and practical support in many ways from Jens Berg and the technical division of Hå kommune, is Unit 5: Glaciation gratefully acknowledged. Anchor Drilling Fluid provided free drill mud. The landowner, Harald Sør-Reime, and Fylkesmannen in Rogaland, permitted Unit 5 till records deposition during fully glaciated con drilling at the sile. Leif V. Jakobsen assisted during the drilling. A. Igesund ditions (Fig. 9) some time after the Early Weichselian assisted with some illustrations. Geoffrey Corner read the manuscript, made useful suggestions and corrected the English language. K. L. Knudsen, A. Lyså interstadial recorded by unit 4. Two tills (the Reime and L. Olsen critically reviewed the manuscript. To all these institutions and diamicton and the Grødeland diamicton) mapped by persons we extend our most sincere thanks. Andersen et al. (1987) in an excavation on the plateau Manuscript received December 1995 above the present day wave-cut cliffwere suggested to be of Late Weichselian and Early Weichselian age, respec tively. By extrapolation towards the coastline, Andersen et al. assumed that both tills have been removed at the References present day beach. This tentative correlation suggests an Aigner, T. & Reineck, H. E. 1982: Proxirnality trends in modem storm sands Early Weichselian age for the unit 5 till. from the Helgoland Bight (North Sea) and their implications for basin analysis. Senckenbergiana maritima 14, 183-215. Andersen, B. G., Nydal, R., Wangen, O. P. & Østmo, S. R. 1981: Weichselian before 15000 years B.P. at Jæren-Karmøy in southwestern Norway. Boreas 10, 297-314. Conclusions Andersen, B. G., Wangen, O. P. & Østmo, S. 1987: Quaternary geology of Jæren and adjacent areas, southwestern Norway. Norges geologiske undersøkelse, The Grødeland borehole recovered 124.5 m of Quater Bulletin 411, !-55. nary sediments representing the Middle and Late Pleis Birkeland, T. 1981: The geology of Jæren and adjacent districts. A contribution to the Caledonian nappe tectonics of Rogaland, southwest Norway. Norsk tocene. The great sediment thickness, combined with Geologisk Tidsskrift 61, 213-235. their stratigraphic span, is unique on land in Norway Bjørlykke, K. O. 1908: Jæderens Geologi. Norges geologiske undersøkelse 48, 160 and can be compared with corings in the North Sea pp. Boulton, G. S. 1990: Sedirnentary and sea leve! changes during glacial cycles and region (Sejrup et al. 1987, 1989, 1991, 1994). the control on glacimarine facies architecture. In Dowdeswell, J. A. & Scourse, The lowermost diamictic unit l represents the oldest J. D. (eds): Glacimarine Environments: Processes and Sediments. Geological glaciation recorded in the Jæren area, occurring around Society Special Publication 53, 15-52. Bouma, A. H. 1962: Sedimentology of Some Flysch Deposits: A Graphic Approach isotope stage 7. Unit 2 comprises relatively fine-grained to Facies lnterpretation. 168 pp. Elsevier, Amsterdam. sediments deposited in consecutively glaciomarine (sub Dreimanis, A. 1988: Tills: Their genetic terminology and classification. In Goldth unit 2-1), normal marine (subunit 2-2) and glaciomarine wait, R.P. & Matsch, C. L. (eds): Genelic C/assijication ofG/acigenic Deposils, 17-83. A. A. Balkema, Rotterdam. environments (subunit 2-3). After the shallow marine Duke, W. L. 1990: Geostrophic circulation or shallow marine turbidity currents? sedimentation, recorded in the lower part of subunit 2-2, The dilemma of paleoflow patterns in storm-influenced progradong shoreline the depositional environment progressively deepened as a systems. Journal of Sedimentary Petro/ogy 60, 870-883. Duke, W. L., Arnott, R. W. C. Cheel, R. J. 1991: Shelf sandstones and result of a marine transgression. The last subunit was & hummocky cross-stratification: new insights on a stormy debate. Geology 19, deposited during a glacier advance, thus demonstrating a 625-628.

Fig. 9. Inferred depositional environments for the entire sedimentary sequence at Grødeland. Unit l time - deposition of till; Subunit 2-1 time - glaciomarine sedimentation during glacier retreat; Subunit 2-2 time - normal marine sedimentation in a storm-dominated environment; Subunit 2-3 time - glaciomarine sedimentation of subunit 2-3 evolving from normal marine conditions; Unit 3 time - glacial conditions, sedimentation of (at !east) the lower part of unit 3; Unit 4 time - glaciomarine sedimentation of unit 4; Unit 5 time - glacial conditions, sedimentation of the uppermost till layer of unit 5. l 00 J. Janocko et al. NORSK GEOLOGISK TIDSSKRIFT 77 (1997)

Elde, L. l., Haver, S., Reistad, M. & Guddal, J. 1986: Statistisk framstilling Mangerud, J., Sønstegaard, E., Sejrup, H. P. & Haldorsen, S. 1981: A continuous av tids-serier av vind- og bølgeparametre, basert på kvalitetsdokumen Eemian-Early Weichselian sequence containing pollen and marine fossils at terte "hindcast" - beregninger for perioden 1.1.1955-31.8. 1985. Maritim Fjøsanger, western Norway. Boreas JO, 137-208. Klima Atlas for den Norske Kon tinentalsokkel og Tilgrensende Havomrader, Mangerud, J. & Svendsen, J. I. 1992: The last interglacial-glacial period on Oslo. Spitsbergen, Svalbard. Quaternary Science Review 11, 633-664. Eyles, N. 1983: Glacial Geology. An In troduction for En gineers an d Earth Scien Miller, G. H., Sejrup, H. P., Mangerud, J. & Andersen, B. G. 1983: Amino-acid tists. 409 pp. Pergamon Press, Oxford. ratios in Quaternary molluscs and foraminifera from western Norway: amino Eyles, N., Eyles, C. H. & Miall, A. D. 1983: Lithofacies types and vertical profile stratigraphy and paleotemperature estimates. Boreas 12, 107-124. models; an alternative approach to the description and environmental interpre Nagy, J. 1965: Foraminifera in some bottom samples from shallow waters in Å tation of glacial diamict and diamictite sequences. Sedimentology 30, 393-410. Vestspitsbergen. Norsk Polarinstitutt, rbok 1963, 109-128. Feyling-Hanssen, R. W. 1964: Skagerakmorenen på Jæren. Norsk Geografisk Nittrouer, C. A. & Sternberg, R. W. 1981: The formation of sedimentary strata Tidsskrift, Bind XIX, 1963-1964, Hefte 7-8, 301-317. in an allochthonous shelf environment: the Washington continental shelf. Feyling-Hanssen, R. W. 1966: Geologiske observasjoner i Sandnasområdet. Marine Geology 42, 201 -232. Norges geologiske undersøkelse 242, 26-43. Olsen, L. & Selvik, S. F. 1995: Bavtajohka Interglacial, the oldest Pleistocene Feyling-Hanssen, R. W. 1971: Weichselian Interstadial Foraminifera from the vegetational record from Norway. Norges Geologiske Un dersøkelse Bulletin 427, Sandnes-Jæren Area. In Feyling-Hanssen, R. W., Jørgensen, J. A., Knudsen, 16-18. K. L. & Andersen, A.-L. L. (eds): Late Quaternary For aminifera fr om Vendsys Osterman, L. E. 1987: Benthic foraminiferal zonation and sedimentary facies of sel, Denmark and Sandnes Norway. Bulletin of Geological Society of Denmark the last glacial/interglacial transition: a method for determining Late Wisconsin 21, 67-317. marine ice margins. Preprint. Feyling-Hanssen, R. W. 1974: The Weichselian section of Foss-Eigeland, south Pettijohn, F. J. 1975: Sedimentary Rocks, 3rd ed. Harper & Row, New York. 628 western Norway. Geologiska Forenin gens i Stockholm Forhand/ingar 96, 341- PP· 353. Porebski, S. J., Meischner, D. & Gorlich, K. 1991: Quaternary mud turbidites Folk, R. L. 1951: Stages of textural maturity. Journal of Sedimentary Petrology from the South Shetland Trench (West Antarctica): recognition and implica 21, 127-130. tions for turbidite facies modelling. Sedimentology 38, 691-715. Fugelli, E. M. F. 1992: Clay minerals in some samples from Opstad and Powell, R. D. 1984: Glacimarine processes and inductive lithofacies modelling of Høgemork on Jæren, southwest Norway. Norsk Geologisk Tidsskrift 72, 217- ice shelf and tidewater glacier sediments based on Quaternary examples. 219. Marine Geology 57, 1-52. Fugelli, E. M. G. & Riis, F. 1992: Neotectonism in the Jæren area, Southwest Sejrup, H. P. 1987: Molluscan and Foraminiferal biostratigraphy of an Eemian Norway. Norsk Geologisk Tidskrift 72, 267-270. Early Weichselian Section on Karmøy, southwestern Norway. Boreas 16, Gregory, D. & Bridge, V. A. 1979: On the Quaternary foraminiferal species 27-42. Elphidium ustulatum Todd 1957: its stratigraphic and paleoecological implica Sejrup, H. P. & Guilbault, J. P. 1979: Cassidulina reniforme and Casidu/in a obtusa tions. Journal of Foraminiferal Research 9, 70-75. (Foraminifera), taxonomy, distribution and ecology. Sarsia 65, 79-85. Grimnes. A. 1910: Jæderens Jordbund. Norges geologiske un dersøkelse 52, 104. Sejrup, P., Aarseth, I., Ellingsen, K. L., Reither, E., Jansen, E., Løvlie, R., Bent, Hald, M., Steinsund, P. l., Dokken, T., Korsun, S., Polyak, L. & Aspeli, R. 1994: A., Brigham-Grette, J., Larsen, E. & Stoker, M. 1987: Quaternary stratigraphy Recent and Late Quaternary distribution of Elphidium excavatum f. clavatum in of the Fladen area, central North Sea. A multidisciplinary study. Journal of Arctic Seas. Cushman Foundation Special Publication No. 32, 141-153. Quaternary Science 2, 35-58. Hernes, S. 1993: Bestemmelse av prekonsolideringstrykk i kvartære avsetningen. Sejrup, H. P., Nagy, J. & Brigham-Grette, J. 1989: Foraminiferal stratigraphy Unpublished thesis, University of Trondheim. 76 pp. and amino acid geochronology of Quaternary sediments in the Norwegian Knudsen, K. L. & Sejrup, H. P. 1988: Amino-acid geochronology of selected Channel, northern North Sea. Norsk Geologisk Tidsskrift 69, 111-124. interglacial sites in the North Sea area. Boreas 1 7, 347-354. Sejrup, H. P., Aarseth, I. & Haftidason, H. 1991: The Quaternary succession in Landvik, J. Y. & Hamborg, M. 1987: Weichselian glacial episodes in outer the northern North Sea. Marine Geology 101, 103- 111. Sunnmøre, western Norway. Norsk Geologisk Tidsskrift 67, 107-123. Sejrup, H. P., Haflidason, H., Aarseth, 1., King, E., Forsberg, F., Long, D. & Larsen, E., Gulliksen, S., Lauritzen, S. E., Lie, R., Løvlie, R. & Mangerud, J. Rokoengen, K. 1994: Late Weichselian glaciation history of the northern North 1987: Cave stratigraphy in western Norway; multiple Weichselian glaciations Sea. Boreas 23, 1-13. and interstadial vertebrate fauna. Boreas 16, 267-292. Sejrup, H. P., Aarseth, 1., Haftidason, H., Løvlie, R., Braten, Å., Tjøstheim, G., Larsen, E. & Mangerud, J. 1989: Marine caves: on-off signals for glaciations. Forsberg, C. F. & Ellingsen, K. L. 1995: Quaternary of the Norwegian Quaternary International 3/4, 13-19. Channel: glaciation his tory and palaeoceanography. Norsk Geologisk Tidsskrift Larsen, E. & Sejrup, H. P. 1990: Weichselian land-sea interaction: Western 75, 65-87. Norway - Norwegian Sea. Quaternary Science Reviews 9, 85-97. Stow, D. A. V. 1979: Distinguishing between fine-grained turbidites and con Loeblich, A. R. & Tappan, H. 1953: Studies on Arctic Foraminifera. Smithsonian tourites on the Nova Scotian deep water margin. Sedimentology 26, 371-387. Miscellaneous Collections, 121. !50 pp. Stow, D. A. W. & Shanmugan, G. 1980: Sequence of structures in fine-grained Lyså, A. & Landvik, J. Y. 1994: Cyclic change in the sedimentary environment turbidites: comparison of recent deep-sea and ancient flysch sediments. Sedi during the last interglacial/glacial cycle; coastal Jameson Land, East Green mentary Geology 25, 23 -42. land. Palaeogeography, Palaeoclimatology, Palaeoecology 112, 143-156. Swift, D. J. P. & Thorn, J. A. 1991: Sedimentation on continental margins, 1: A Lønne, l. 1993: Physical signatures of ice advance in a Younger Dryas ice-contact general model for shelf sedimentation. Special Publications of In ternal Associa delta, Troms, northern Norway: implications for glacier-terminus history. tion of Sedimentologists 14, 3-31. Boreas 22, 59-70. Wangen, O. P. 1968: Kvartærgeologiske Undersøkelser på Jæren, kartbladene Lønne, l. 1995: Sedimentary facies and depositional architecture of ice-contact Nærbø og Bjerkreim. Unpublished thesis. University of Oslo. 138 pp. glaciomarine systems. Sedimentary Geology 98, 13-43. Weggel, R. J. 1972: An introduction to oceanic water motions and their relation Løvlie, R. 1994: Stratigraphic boring Jæren 1993. Paleomagnetic results. Unpub to sediment transport. In Swift, D. J. P., Duane, D. B. & Pilkey, O. H. (eds): lished report, Institute of Solid Earth Physics, University of Bergen. 29 pp. ShelfSediment Transport: Process and Pattern, 1-20. Dowden, Hutchinson & Mackiewicz, N. E., Powell, R D., Carlson, P. R. & Molnia, B. F. 1984: Ross, Inc. Stroudsburg, Pennsylvania. Interlaminated ice-proximal glacimarine sediments in Muir Inlet, Alaska. Østmo, S. R. 1971: En Kvartærgeologisk undersøkelse på midtre Jæren og Marine Geology 57, 113-147 fjellområdene østenfor. Unpublished thesis, University of Oslo. 274 pp.