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Deep Sea Drilling Project Initial Reports Volume 38

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Deep Sea Drilling Project Initial Reports Volume 38 31. RADIOLARIA FROM THE NORWEGIAN SEA, LEG 38 OF THE DEEP SEA DRILLING PROJECT Kjell R. Bj^rklund, Geological Institute Department B., University of Bergen, 5014-Bergen-University, Norway INTRODUCTION North Atlantic Ocean, Benson (1972) was able to use the established radiolarian stratigraphy for an age The high latitudes of the Arctic region were first determination of the sediments. Thus, one of the main visited by D/V Glomar Challenger in 1974, on Leg 38 of objectives of this paper was to search out the radio- the Deep Sea Drilling Project, to the Norwegian Sea. larian stratigraphy, and see if the already established Seventeen sites were selected, and 17 holes were drilled zonation from lower latitudes could be used with faunal during this leg (Figure 1, see Table 1 in Chapter 1, this assemblages recovered from the Norwegian Sea. volume) Based on reports from Russian workers, Lipman For radiolarian studies, the Norwegian Sea is a virgin (1950), Kozlova and Gorbovetz (1966), and Bjprklund area, as no information is available on either radio- and Kellogg (1972), the present author recognized larian stratigraphy or biogeography from pre-Holo- similarities in the faunal assemblages from Siberia and cene sediments. The distribution of radiolarians in the the V^ring Plateau. Since these faunal assemblages are surface sediments of the Norwegian-Greenland Sea is quite different from the assemblages reported by Ben- discussed in only four papers. Stadum and Ling (1969) son (1972) and Petrushevskaya and Kozlova (1972), reported on the recent distribution of phaeodarians and DSDP Legs 12 and 14 from the northern and equatorial their state of preservation, Petrushevskaya (1969) and Atlantic, respectively, the author concludes that the Petrushevskaya and Bjyfrklund (1974) dealt with the radiolarian population in the North Atlantic and the distribution of polycystine radiolarians from surface Norwegian-Greenland Sea must have somehow been sediments. isolated. Most likely this was due to a landbridge, the Only one paper, Bj^rklund and Kellogg (1972) deals Iceland-Faeroe Ridge, present during the early phase of with the stratigraphy of Tertiary (late Eocene) the development of the Norwegian-Greenland Sea. Re- sediments, from a site located near the top of one of the cent data from the Aleutian Islands also lead to the diapiric structures on the V^ring Plateau southwest of conclusion, that during early Tertiary, the North the Lofoten Peninsula. R/V Vema of Lamont-Doherty Pacific was isolated from the Arctic Ocean by a land- Geological Observatory has made several cruises (V 23, bridge, due to an elevation of the Aleutian Islands. V27, V 28, and V 30) into the Norwegian-Greenland The foregoing suggests that the Arctic in the early Sea, taking nearly 200 piston cores. The Tertiary Tertiary was an isolated ocean, which explains why it is sediments were recovered during the two latter cruises. only in the early Tertiary that the Siberian and V^ring Tertiary continental outcrops from northern Europe Plateau faunas have common species. such as Denmark, North Germany, North Poland, and Goll and Bj^rklund (in press) show that the oc- Franz Josephs Land—Novaja Semlja discussed in currence of radiolarians in the surface sediment of the Heiberg, 1863; Hustedt (in O. Wetzel, 1935); Schulz, Norwegian-Greenland Sea is associated with the high 1927; Grundow, 1884, respectively, are all similar in an productive areas in the western Norwegian Sea and absence of radiolarians. However, from other land sec- with the areas in the eastern Norwegian Sea underlying tions on the USSR eastern territories, radiolarian the Norwegian-Atlantic Current (the continuation of assemblages of Paleocene and Eocene ages have been the Gulf Stream). The Greenland Sea is barren or very described by different Russian authors—Borisenko poor in radiolarians. This distribution pattern is not yet (1960a, b), Krasheninnikov (1960), Kozlova and Gor- fully understood, but the main conclusion must be that bovetz (1966), and Lipman (1950). the North Atlantic Current passing over the Iceland- DSDP Leg 12 went to the area south of the Faeroe Ridge, into the Norwegian Sea, greatly in- Norwegian-Greenland Sea, the Labrador Sea, Rockall fluences this distribution pattern, together with dissolu- Basin, and the Bay of Biscay. Here, Benson (1972) tion and masking effects. reported on radiolarian assemblages with good preser- The main objectives of this study were: to try to es- vation, recovered from sediments of Pliocene to tablish a radiolarian stratigraphy for the Norwegian- Oligocene age, while strongly corroded faunas were ob- Greenland Sea; to compare the radiolarian fauna tained from Eocene and Paleocene sediments. recovered in the North Atlantic during DSDP Legs 12 Generally no information is available on Tertiary and 14 with that of Leg 38, in an attempt to test the radiolarian stratigraphy in the Norwegian-Greenland hypothesis that the North Atlantic and the Nor- Sea. A well-established Quaternary-Tertiary radio- wegian-Greenland Sea were not connected in the early larian stratigraphy has been established by Riedel and Tertiary; to search for the time when the North Atlantic Sanfilippo (1970, 1971) for DSDP Legs 4 and 7, respec- Current swept over the Iceland-Faeroe Ridge, in other tively, and Moore (1971) for Leg 8 in lower Atlantic words, when did the ridge submerge. Finally, could the and Pacific latitudes. During DSDP Leg 12 to the results of Leg 38 provide information regarding 1101 o NJ Cd •— 10° 15° 20° 25° 30 25° ?0° 15° 10° 0° TO • /»c C Z σ 75* 75° 70' 70° PROFILES 65' CONTOUR DEPTHS ARE IN 65° NOMINAL FATHOMS (SOUND VELOCITY 800 fms/fcec.) DEPTH GREATER THAN IδOOfms. • EARTHQUAKE EPICENTERS •fc•DRILL SITES EDGE OF CONTINENTAL SHELF j". Base Map from Talwani β Eldholm (in prep) 60' 60° 30° 25° 20° 15° IOe 10° 15° 20° 30° Figure L Location of Leg 38 drilling sites, and bathymetry and structure of the Norwegian - Greenland Sea. (Note: Site 351 was occupied but was not drilled. Its location has not been shown on this map. The inset map shows the track of Glomar Challenger between Sites 338 and 343 on the Voring Plateau. Portions be- tween Sites 339 and 343 correspond to line of composite profile illustrated in accompanying diagram. Also shown are position of Voring Plateau Escarpment, and corrected bathymetry of the area, in hundreds of meters, constructed principally from records taken by R/V Vema of Lamont Doherty Geological Observatory, supplemented by Glomar Challenger data. RADIOLARIA climatic shifts during Pleistocene time, and did the R: Rare—one to five fragments were observed on Pleistocene coolings have any influence on the current half the slide; circulation in the North Atlantic? F: Few—more than five fragments or tests were ob- served on half the slide; MATERIAL AND METHODS C: Common—mostly complete tests. 1-30 tests per All samples used in this study were cleaned using traverse were observed using the 63 X objective; standard procedures. It is of importance to describe in A: Abundant—mostly complete tests, greater than detail how the samples were processed, because an un- 30 tests were observed using the 63 × objective. known "microfossil" was frequently found at Sites 338, These designations are only of limited value due to 344, and 349. In the literature, they are described as the fact that the faunal slides were made in a semi- Anellotubulates. Recently they have been described as quantitative way. For this study, about 700 samples being artifacts, produced by reaction of H2O2 with were processed and examined for radiolarians. pyrite (Pickett and Scheibnerova, 1974, and Richard- son et al., 1973). Perch-Nielsen (1975) reported on and BIOSTRATIGRAPHY illustrated similar "microfossils." The procedures were During Leg 38, Cenozoic sediments were cored from as follows: the Arctic region for the first time, and as similar 1) An equal amount of sediment was used for easier material never has been available, it was now possible observation of fluctuations in the radiolarians per to do a detailed study on Cenozoic radiolarian stratig- volume units of sediment. raphy and paleoecology. Due to time limitations, the 2) Water was brought to the boiling point in a major emphasis of the present contribution is to es- beaker, sample was introduced, then concentrated tablish a northern high-latitude radiolarian biostratig- H2O2 and sodium hexametaphosphate (Calgon) was raphy. It is hoped the biostratigraphic framework out- added. lined in this paper will be useful for the scheduled 3) The suspension was treated with an ultrasound I POD Leg 49. probe for about 10-15 sec, then sieved on a 44 µm The radiolarian assemblages recovered during this screen. leg had very few species in common with holes drilled 4) Residue was treated with HC1, and the ultra- further south in the Atlantic Ocean. As no key fossils, sound probe was used for 5 sec. upon which the lower latitude Atlantic and Pacific 5) The fine fraction of the residue was brought into oceans are based, could be found in sufficient numbers, suspension in the beaker and decanted.. The suspension it was necessary to develop a local Norwegian Sea was allowed to settle out in a clean beaker, and from radiolarian stratigraphy. Again, due to time limita- this fine fraction the fauna slides were made. tions, the taxonomic chapter will only deal with those 6) 0.5 ml was pipetted out and put on a 25 × 50 mm species being significant for this local biostratigraphy. coverslip. Sample was spread out with a toothpick and However, species of little or no value for the dried on a hotplate. stratigraphy, but of value for information on the faunal 7) Caedax (N = 1.56) was put on the slide, a drop or assemblages, are illustrated. two of xylene was put on the coverslip, which was No absolute or good age determination of the sedi- placed on the slide.
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