Calcareous nannofossil biostratigraphy of the central East Pacific Rise

During Leg 92 of the Deep Sea Drilling Project, sediments containing calcareous nannofossils of latest Oligocene to Holocene age were recovered from 14 holes at six sites (597 to 602) along the East Pacific Rise. The combined sections yield a virtually complete record for the region, with a compressed upper Miocene to Pleistocene interval. The nannofossil content of 14 U.S.N.S. Eltanin piston cores from the study area were also examined in order to supplement data generated during Leg 92. Two taxonomically new combinations are presented: Sphenolithus umbellus and Pontosphaera segmenta. Assemblages of calcareous nannofossils juxtaposed in reversed stratigraphic order within the upper Miocene provide strong evidence for downslope transport of sediments along the East Pacific Rise during the Messinian. Narrow bands of dark metalliferous sediment of coccolith Zone CN8b alternate with normal light-colored, in situ, pelagic sequences of Zone CN9b. This may indicate more vigorous bottom current activity between 5.40 and 6.70 Ma.

Paleocene and Eocene diatom biosttarigraphy of ODP Hole 121-752A, eastern Indian Ocean

The Paleocene/Eocene boundary was recovered for the first time in diatom-bearing sediments at Broken Ridge, Site 752. Diatom assemblages are documented throughout the 180-m-thick sequence of upper Paleocene to lower Eocene sediments. Age control available from magnetostratigraphy, calcareous nannofossils, and planktonic foraminifers allows calibration of diatom datum levels to absolute time. A partly new/partly revised diatom zonation is proposed for the Paleocene/early Eocene based on the results of Site 752 and consideration of other studies. The diatom zones are defined as follows (from the youngest to the oldest): Pyxilla gracilis Zone (first occurrence of Craspedodiscus undulatus to first occurrence Pyxilla gracilis); Hemiaulus incurvus Zone (first occurrence Pyxilla gracilis to first occurrence Hemiaulus incurvus); Hemiaulus peripterus Zone (first occurrence Hemiaulus incurvus to first occurrence Hemiaulus peripterus var. peripterus). Three new taxa are described: Anaulus fennerae n. sp., Stictodiscus bipolaris n. sp., and Hemiaulus peripterus var. longispinus n. var.

Latest Oligocene through early middle Miocene diatom biostratigraphy of the eastern tropical Pacific

Study of DSDP Sites 71, 77, and 495 has allowed the development of a refined diatom biostratigraphy for the latest Oligocene through early middle Miocene of the eastern tropical Pacific which is well correlated to the low-latitude zonations for planktonic foraminifers, coccoliths, and radiolarians. Six zones and 7 subzones are proposed, and correlation with high-latitude diatoms zonations for the North Pacific, the Norwegian Sea, and the Southern Ocean is suggested by the discovery of selected diatoms in these tropical sediments which were previously thought to be restricted to high latitudes. Six new species and one new variety of diatoms which are stratigraphically useful are proposed : Actinocyclus hajosiae, n. sp., A. radionovae, n. sp., Coscinodiscus blysmos, n. sp., C. praenodulifer, n. sp., Craspedodiscus rydei, n. sp., Thalassiosira bukryi, n. sp., and Coscinodiscus lewisianus var. robustus n. var.

Distribution of late Quaternary calcareous nannofossils in DSDP Leg 96 sites

Sediments from holes drilled at 11 sites in the northern Gulf of Mexico during Deep Sea Drilling Project Leg 96 were analyzed for calcareous nannofossil content. All sediments recovered are Holocene and late Pleistocene in age and are within the Emiliania huxleyi Zone. The datum level represented by the lowest stratigraphic occurrence of dominant E. huxleyi occurs at two sites (Sites 615 and 619) and can be dated at approximately 84,000 yr. ago at Site 619. Reworked Cretaceous nannofossils are generally common or abundant and dominate the floral assemblages of the late Wisconsin glacial sediments. When present, indigenous late Quaternary species are rare or few in abundance. Slight increases in the contemporaneous Quaternary component of the floral assemblages can be documented by the use of a calculated in s/fu/reworked ratio. This ratio, based on the relative abundances of the indigenous Quaternary taxa and reworked taxa, shows potential both for local correlations between drill sites and for correlation with glacio-eustatic fluctuations during the late Pleistocene.

Silicoflagellates of ODP Leg 119 samples

The occurrence of Quaternary and Oligocene silicoflagellates at two Ocean Drilling Program (ODP) Leg 119 Holes (736A and 744A) on the Kerguelen Plateau in the Southern Ocean was investigated to compare species distributions to Northern Hemisphere floras. This abstract gives the data determined (Tables 1 and 2) for 24 samples and few preliminary remarks. Quaternary assemblages of Hole 736A are noteworthy for the absences of key North Pacific zonal guide species such as Bachmannocena quadrangula, Dictyocha aculeata, Dictyocha subarctios, and Distephanus octangulatus (Bukry and Monechi, 1985). Other species such as Distephanus floridus, Distephanus speculum elongatus, and Mesocena octagona show limited ranges in Hole 736A and may help to subdivide the Quaternary locally. The late Oligocene assemblages of Hole 744A contain widely distributed species of Distephanus and Naviculopsis, which permit correlation to lower latitude assemblages. They also contain the high-latitude acme of Distephanus raupii which was first noted at Deep Sea Drilling Project (DSDP) Hole 278 (56°3.42'S, 160°04.29'E, water depth 3689 m) by Perch-Nielsen (1975) and Bukry (1975). Study of Hole 744A assemblages suggests that D. raupii developed from pentagonal Dictyocha deflandrei deflandrei. A final note on the Hole 744A assemblages is the brief late Oligocene acme (25%) of Dictyocha sp. aff. D. spinosa in Sample 119-744A-13H-4, 65-67 cm, which provides a direct correlation to the acme (16%) in DSDP Sample 29-278-31R-CC (Perch-Nielsen, 1975) in the Southern Ocean. Most of the taxonomy used in the tables is documented in earlier publications of the DSDP Initial Reports (see Bukry in Volumes 16, 35, 37, 40, 44, 49, 54, 67, 68, 69, 81, and 95). Also, see Loeblich et al. (1968) and Perch-Nielsen (1985) for extensive taxonomy and illustrations.

Tide amplitude at Ilulissat, and surface height and flow velocities of Jakobshavn Isbrae in August 2004

During the summer of 2004, the front area of the Jakobshavn Isbræ was monitored using a geodetic-photogrammetric survey with temporarily coincident precise observations of local ocean tides in the Disko Bay close to Ilulissat. The geodetic and photogrammetric observations were conducted at the southern margin of the glacier front. The largest observed horizontal flow velocities are in the central part of the front with values up to 45 m/d. This is a factor of 2 greater than the average velocities at the front area observed in the last century. Our new observations confirm previous estimates of an acceleration of glacier flow during the last decade. The photogrammetric survey provided flow trajectories for 4000 surface points with a time resolution of 30 min. These flow trajectories were used to compare the vertical motion of the glacier with the observed tides. The existence of a free-floating glacier tongue in 2004 was confirmed by these data. However, it occupied only a small belt, of at most a few 100 m width, in the central part of the glacier front. Horizontal motion did not appear to depend on the tidal phase, unlike some of the fast-moving ice streams of West Antarctica.

Silicoflagellates in ODP Leg 108 holes

The occurrence of Cenozoic silicoflagellates at three Ocean Drilling Program (ODP) Holes (660A, 662A, and 667A) was investigated to determine biostratigraphic and relative paleotemperature relations in the tropical Atlantic Ocean. This report presents the data obtained from a study of 37 samples and some preliminary comments on the data. The age of the single sparse assemblage at Hole 660A is late middle Eocene or late Eocene (Dictyocha hexacantha Zone); the sparse to common assemblages of Hole 667A are Oligocene and early Miocene and the common to abundant assemblages of Hole 662A are early Pliocene to Quaternary. Dissolution thinning of silicoflagellates is noted in most samples, even in Hole 662A, which is under the present productive Benguela Current.

Multibeam bathymetry of Timmiarmiut and Skjoldungen-Fjord, Southeast-Greenland

During an expedition with the topsail-schooner ACTIV in July 2014, parts of the Timmiarmiut-Fjord and nearly the entire Skjoldungen-Fjord in Southeast-Greenland have been mapped using a temporarily installed Seabeam-1050 multibeam echosounder. In addition, at 11 positions in the fjords, depth profiles of temperature, conductivity, salinity and sound velocity have been measured with a CTD.