Diatom abundance in ODP Leg 178 holes

This paper documents the biostratigraphic distribution and abundance of diatoms from sites drilled during Ocean Drilling Program Leg 178, off the Pacific margin of the Antarctic Peninsula. Drift sediments cored on the continental rise at Sites 1095, 1096, and 1101 have good recovery and a well-defined paleomagnetic record. Well-preserved diatoms are present throughout the upper Miocene to middle Pliocene and in the upper Quaternary section of these sites. The stratigraphic occurrence of diatom species through these intervals defines numerous datum levels. Diatom events are given absolute age estimates through direct correlation to the established paleomagnetic stratigraphy of Sites 1095, 1096, and 1101. Leg 178 diatom biostratigraphic results enable the development of a regional stratigraphic framework for the Pacific sector of the Southern Ocean and record the interaction of open-ocean and shelf-margin diatom floras.

Radiolarian biostratigraphy and chronology of radiolarian events of ODP Leg 199 sites and EW9709 sediment cores

A generally rich radiolarian fauna ranging in age from Quaternary to early Eocene (Zone RP7) was found at five of the eight sites drilled during Ocean Drilling Program (ODP) Leg 199. Of particular interest are the stratigraphically complete assemblages that range in age from middle Miocene (Zone RN5) to early Eocene (Zone RP7), composites of Sites 1218, 1219, and 1220. At the same sites, multisensor track (MST) data show consistent cycles in gamma ray attenuation density, color, and carbonate content that can be correlated on a submeter scale from the early Miocene to early Eocene. In addition, the magnetic reversal records from these three sites allow construction of an absolute timescale. A series of 305 radiolarian morphologic first and last occurrences and evolutionary transitions for radiolarians were determined and correlated directly with the accompanying MST and paleomagnetic data, resulting in a detailed and accurate dating of events. Since many of the bioevents are found at more than one site, it was also possible to test their reliability within the study area. Twelve new species are described: Calocycletta (Calocycletta) anekathen, Dorcadospyris anastasis, Dorcadospyris copelata, Dorcadospyris cyclacantha, Dorcadospyris ombros, Dorcadospyris scambos, Eucyrtidium mitodes, Theocyrtis careotuberosa, Theocyrtis perpumila, Theocyrtis perysinos, Theocyrtis setanios, and Thyrsocyrtis (Pentalacorys) orthotenes.

Diatoms in Paleocene sediments of the southwestern South Atlantic

The taxonomy and stratigraphy of pelagic Paleocene diatoms from ODP Sites 698, 700, and 702 and DSDP Site 524 in the South Atlantic and DSDP Site 214 in the Indian Ocean are presented, as well as paleogeographic and paleoecologic implications. Eleven new species and one new variety are described and one new combination is proposed: Coscinodiscus cruxii sp. nov. Grunowiella palaeocaenica var. alternans var. nov. Hemiaulusl beatus sp. nov. Hemiaulusl ciesielskii sp. nov. Hemiaulusl conicus sp. nov. Hemiaulus kristoffersenii sp. nov. Hemiaulus nocchiae sp. nov. Hemiaulusl oonkii sp. nov. Hemiaulusl velatus sp. nov. Triceratium gombosii sp. nov. Trochosira gracillima comb. nov. Trochosira marginata sp. nov. Trochosira radiata sp. nov. Hole 700B provides one of the most continuous diatomaceous Paleocene profiles known. Stratigraphic ranges of diatom species from this and other Southern Hemisphere sites are calibrated against calcareous microfossil zones. The first-appearance datums of Triceratium gombosii, Hemiaulus incurvus, and Triceratium mirabile in Paleocene deep-sea sediments are useful for regional stratigraphic correlations. Quantitative analysis of the biosiliceous microfossil groups (diatoms, silicoflagellates, radiolarians, and archaeomonadaceae) shows that preservation of diatoms is confined primarily to the upper Paleocene (planktonic foraminifer Zones P3 and P4 and calcareous nannofossil Zones upper NP5 to lower NP9). In the lower Paleocene only short intervals in Hole 700B are diatomaceous. A correlation between the degree of silica diagenesis and the calcium carbonate content of the sediment is not obvious. Diatom species analysis reflects changes in the paleoenvironment between island-related upwelling conditions with highly diverse and well-preserved diatom assemblages and less productive periods resulting in less wellpreserved diatom assemblages with a higher content of robust neritic diatoms.

Planktonic foraminifer stratigraphy of late Pliocene sediments from ODP Hole 167-1021C

This report is an initial investigation of the planktonic foraminifers from the late Pliocene of Ocean Drilling Program Hole 1021C. Planktonic foraminifer assemblages show fair preservation in many samples. Assemblages are quantitatively dominated by Globigerina bulloides, dextral coiling Neogloboquadrina atlantica, and Globorotalia inflata and alternate between cool temperate and subarctic conditions.

Eocene and Oligocene radiolarian biostratigraphy from the Southern Ocean

Eocene-Oligocene radiolarians from Ocean Drilling Program Sites 699, 702, and 703, Leg 114 of the Subantarctic Atlantic were examined in order to extend the tripartite zonation for the recovered cores based on results of similar analysis of Leg 120 submarine sediments from the Indian Ocean. Correlation of the two oceans is made by examining 23 biohorizons and the three zones, Eucyrtidium spinosum, Axoprunum irregularis, and Lychnocanoma conica, in ascending stratigraphic order. One new species, Eucyrtidium nishimurae, is described.

Jurassic microfossils of DSDP Hole 79-547B

The first marine incursion of the incipient North Atlantic Ocean is recorded in the uppermost Triassic to Lower Jurassic sequence of DSDP Site 547 off central Morocco. A lithologic change from continental red beds below to slope breccias and hemipelagic carbonates above indicates that a carbonate ramp was probably established by Sinemurian time along the Moroccan continental margin and that subsidence in the adjacent basin was rapid in the early phases of continental rift. Foraminifers recovered from the Liassic (Sinemurian-Pliensbachian) basinal deposits are diverse and well preserved. The faunas are compositionally similar to contemporaneous neritic assemblages of Europe and the Grand Banks of Newfoundland. The Middle Jurassic in Hole 547B is characterized by regressive deposits that are poor in foraminifers. The major Late Jurassic "Atlantic" transgression is again represented by basinal deposits consisting of limestone breccias and pelagic carbonates. Foraminifers recovered from this interval are transitional between Late Jurassic assemblages reported from deep-sea deposits in the North Atlantic and typical Late Jurassic neritic assemblages of Europe. The Late Jurassic assemblages of Hole 547B are primarily dominated by nodosariids and spirillinids with moderate abundances of simple arenaceous forms. Nonreticulate epistominids occur very rarely in the Upper Jurassic of Hole 547B. It is tentatively suggested that these represent upper bathyal assemblages.

Distribution of radiolaria in Oligocene to Pleistocene sediments of the North-West Pacific

Neogene stratigraphy of the tropical and subtropical Pacific on radiolaria is studied in the book. A detailed comparison of coeval systems from tropics and subtropics is given. A possibility of use of a uniform zonal scale in these areas is proved. Magnitude of changes of complexes on borders of Neogene zones is studied in detail. Six stages in development of radiolarians are identified in the tropics in Neogene. Stratigraphic levels, where the greatest changes of fauna occurred, are natural boundaries of these stages. 72 species of radiolarians (two of which are new) are described in the book.

Ostracoda communities from DSDP Holes 95-612 and 95-613

Ninety-three samples from DSDP Leg 95, Sites 612 and 613, were examined for ostracodes to aid in the study of paleoceanography and paleodepth. In total, more than 25 genera were recovered. The most abundant and diverse ostracode assemblages were from the middle Eocene at both sites; lower and upper Eocene and Pliocene-Pleistocene assemblages were less abundant and were dominated by only three or four species. The middle Eocene assemblages were the most diagnostic of paleoenvironment and suggest water depths of 1000 to 2000 m. These assemblages are similar to other middle Eocene assemblages known from the Caribbean and North Atlantic, and signify a relatively cosmopolitan fauna that inhabited moderately deep but relatively warm bottom waters.

Stable carbon and oxygen isotope ratios for different test sizes of live benthic foraminifera from the Arabian Sea

We determined the stable oxygen and carbon isotopic composition of live (Rose Bengal stained) tests belonging to different size classes of two benthic foraminiferal species from the Pakistan continental margin. Samples were taken at 2 sites, with water depth of about 135 and 275 m, corresponding to the upper boundary and upper part of the core region of the oxygen minimum zone (OMZ). For Uvigerina ex gr. U. semiornata and Bolivina aff. B. dilatata, delta13C and delta18O values increased significantly with increasing test size. In the case of U. ex gr. U. semiornata, delta13C increased linearly by about 0.105 per mil for each 100-µm increment in test size, whereas delta18O increased by 0.02 to 0.06 per mil per 100 µm increment. For B. aff. B. dilatata the relationship between test size and stable isotopic composition is better described by logarithmic equations. A strong positive linear correlation is observed between delta18O and delta13C values of both taxa, with a constant ratio of delta18O and delta13C values close to 2:1. This suggests that the strong ontogenetic effect is mainly caused by kinetic isotope fractionation during CO2 uptake. Our data underline the necessity to base longer delta18O and delta13C isotope records derived from benthic foraminifera on size windows of 100 µm or less. This is already common practice in down-core isotopic studies of planktonic foraminifera.

Chemistry of volcanic ash from Celebes and Sulu Sea Basins

During Leg 124, off the Philippines, volcanic material was recovered in deep-sea sediments dating from the late Oligocene in the Celebes Sea Basin, and from the early Miocene in the Sulu Sea Basin. Chemical and petrological studies of fallout ash deposits are used to characterize volcanic pulses and to determine their possible origin. All of the glass and mineral compositions belong to medium-K and high-K calc-alkaline arc-related magmatic suites including high-Al basalts, pyroxene-hornblende andesites, dacites, and rhyolites. Late Oligocene and early Miocene products may have originated from the Sunda arc or from the Sabah-Zamboanga old Sulu arc. Late early Miocene Sulu Sea tuffs originated from the Cagayan arc, whereas early late Miocene fallout ashes are attributed to the Sulu arc. A complex magmatic production is distinguished in the Plio-Quaternary with three sequences of basic to acidic lava suites. Early Pliocene strata registered an important activity in both Celebes Sea and Sulu Sea areas, from the newly born Sangihe arc (low-alumina andesite series) and from the Sulu, Zamboanga, and Negros arcs (high-alumina basalt series and high-K andesite series). In the late Pliocene and the early Pleistocene, renewal of activity affects the Sangihe-Cotobato arc as well as the Sulu and Negros arcs (same magmatic distinctions). The last volcanic pulse took place in the late Pleistocene with revival of all the present arc systems.

Middle Miocene to Quaternary diatom biostratigraphy of DSDP Site 90-594

A diatom biostratigraphy is presented for middle Miocene through Quaternary sediments recovered from the Chatham Rise east of New Zealand's South Island. The upper 590 m of the 639.5-m composite-section Site 594 represents approximately 16 m.y. and is characterized by moderately to very poorly preserved diatoms of antarctic to temperate affinity. Pliocene through Quaternary assemblages are poorly preserved and dominated by antarctic-subantarctic species which provide detailed biostratigraphic control. Recognized are 11 of 14 zones of the middle upper Miocene to Quaternary Neogene Southern Ocean diatom zonation (NSD 7-NSD 20) of Ciesielski (1983; this chapter). Four Neogene Southern Ocean diatom zones (NSD 3-NSD 6) are recognized in the lower middle Miocene to middle upper Miocene of Site 594. Assemblages of this interval have a mixed high-latitude and temperate affinity; however, poor preservation limits correlation to high- and temperate-latitude zonal schemes. Neogene North Pacific diatom zones and subzones of NNPD 3 through NNPD 5 (Barron, in press, b) are correlated to Neogene Southern Ocean diatom zones NSD 3 through NSD 7: the upper portions of the Actinocyclus ingens Zone (NNPD 3) is correlative to the upper Nitzschia maleinterpretaria Zone (NSD 3); the Denticulopsis lauta Zone (NNPD 4) and Subzones a and b are correlative to the lower Coscinodiscus lewisianus Zone (NSD 4); and the D. hustedtü-D. lauta Zone (NNPD 5) and its Subzones a through d encompass the upper C. lewisianus Zone (NSD 4), N. grossepunctata Zone (NSD 5), N. denticuloides Zone (NSD 6), and the lower D. hustedtii-D. lauta Zone (NSD 7). A major disconformity spans the late Gilbert to early Gauss Chron (3.9-2.8 Ma). A second disconformity brackets the Miocene/Pliocene boundary; the section missing covers late Chron 5 and the early Gilbert chron (5.5-4.6 Ma). The remainder of the siliceous-fossil-bearing Miocene sediments at Site 594 appear to be correlative to lower paleomagnetic Chronozone 5 through upper Chronozone 16. Uppermost lower Miocene or lowermost middle Miocene sediments in the basal 50 m of Hole 594A are barren of diatoms.

Distribution of deep-sea foraminifera in surface sediments east of New Zealand

Paleobathymetric assessments of fossil foraminiferal faunas play a significant role in the analysis of the paleogeographic, sedimentary, and tectonic histories of New Zealand's Neogene marine sedimentary basins. At depths >100 m, these assessments often have large uncertainties. This study, aimed at improving the precision of paleodepth assessments, documents the present-day distribution of deep-sea foraminifera (>63 µm) in 66 samples of seafloor sediment at 90-700 m water depth (outer shelf to mid-abyssal), east of New Zealand. One hundred and thirty-nine of the 465 recorded species of benthic foraminifera are new records for the New Zealand region. Characters of the foraminiferal faunas which appear to provide the most useful information for estimating paleobathymetry are, in decreasing order of reliability: relative abundance of common benthic species; benthic species associations; upper depth limits of key benthic species; and relative abundance of planktic foraminifera. R mode cluster analysis on the quantitative census data of the 58 most abundant species of benthic foraminifera produced six species associations within three higher level clusters: (1) calcareous species most abundant at mid-bathyal to outer shelf depths (<1000 m); (2) calcareous species most abundant at mid-bathyal and greater depths (>600 m); (3) agglutinated species mostly occurring at deep abyssal depths (>3000 m). A detrended correspondence analysis ordination plot exhibits a strong relationship between these species associations and bathymetry. This is manifest in the bathymetric ranges of the relative abundance peaks of many of the common benthic species (e.g., Abditodentrix pseudothalmanni 500-2800 m, Bolivina robusta 200-650 m, Bulimina marginata f. marginata 20-600 m, B. marginata f. aculeata 400-3000 m, Cassidulina norvangi 1000-4500 m, Epistominella exigua 1000-4700 m, and Trifarina angulosa 10-650 m), which should prove useful in paleobathymetric estimates. The upper depth limits of 28 benthic foraminiferal species (e.g., Fursenkoina complanata 200 m, Bulimina truncana 450 m, Melonis affinis 550 m, Eggerella bradyi 750 m, and Cassidulina norvangi 1000 m) have potential to improve the precision of paleobathymetric estimates based initially on the total faunal composition. The planktic percentage of foraminiferal tests increases from outer shelf to upper abyssal depths followed by a rapid decline within the foraminiferal lysocline (below c. 3600 m). A planktic percentage <50% is suggestive of shelf depths, and >50% is suggestive of bathyal or abyssal depths above the CCD. In the abyssal zone there is dramatic taphonomic loss of most agglutinated tests (except some textulariids) at burial depths of 0.1-0.2 m, which negates the potential usefulness of these taxa in paleobathymetric assessments.

Radiolarians from the Southwest Pacific

Radiolarians are very rare in all Leg 90 sites. They are relatively more frequent only in Neogene sediments from Sites 586 and 594, and in Eocene sediments at Site 592. In this chapter radiolarian abundances are recorded as comparative percentages for 92 Neogene morphotypes at Site 586B. Relative abundances only are estimated at Sites 592 and 594, where preservation is poor to moderate. A tentative correlation of radiolarian events at Hole 586B and Site 594 shows that only a few species can be found in both tropical and subantarctic areas. New evolutionary lineages are proposed. 1. Middle Miocene eucyrtids like Eucyrtidium teuscheri group evolved into a widespread species (E. teuscheri teuscheri) ranging from middle Miocene to Holocene and a temperate species (E. teuscheri orthoporus) ranging from middle Miocene to early Pleistocene. 2. Phormostichoartus pitomorphus appears to be a temperate descendant of the cosmopolitan P. fistula and disappears in early Pleistocene time. 3. The discovery of Lamprocyrtis daniellae n.sp. calls into question the lineage L. heteroporos -> L. nigriniae. 4. The evolution of Lamprocyclas maritalis from an ancestor group (L. aff. maritalis) is located in the early part of the Pterocanium prismatium Zone.