Plant species, biomass and environmental characteristics of relevés along the North America Arctic bioclimate gradient

Question: How do interactions between the physical environment and biotic properties of vegetation influence the formation of small patterned-ground features along the Arctic bioclimate gradient? Location: At 68° to 78°N: six locations along the Dalton Highway in arctic Alaska and three in Canada (Banks Island, Prince Patrick Island and Ellef Ringnes Island). Methods: We analysed floristic and structural vegetation, biomass and abiotic data (soil chemical and physical parameters, the n-factor [a soil thermal index] and spectral information [NDVI, LAI]) on 147 microhabitat releves of zonalpatterned-ground features. Using mapping, table analysis (JUICE) and ordination techniques (NMDS). Results: Table analysis using JUICE and the phi-coefficient to identify diagnostic species revealed clear groups of diagnostic plant taxa in four of the five zonal vegetation complexes. Plant communities and zonal complexes were generally well separated in the NMDS ordination. The Alaska and Canada communities were spatially separated in the ordination because of different glacial histories and location in separate floristic provinces, but there was no single controlling environmental gradient. Vegetation structure, particularly that of bryophytes and total biomass, strongly affected thermal properties of the soils. Patterned-ground complexes with the largest thermal differential between the patterned-ground features and the surrounding vegetation exhibited the clearest patterned-ground morphologies.

Dinocyst datum events of several holes in the Norwegian-Greenland Sea

The presence of abundant age-diagnostic dinoflagellate cysts in Ocean Drilling Program (ODP) Hole 913B (Leg 151), Deep Sea Drilling Project Hole 338 (Leg 38) and ODP Hole 643A (Leg 104) has enabled the development of a new biostratigraphy for the Eocene-Oligocene interval in the Norwegian-Greenland Sea. This development is important because the calcareous microfossils usually used for biostratigraphy in this age interval are generally absent in high latitude sediments as a result of dissolution. In parallel with this biostratigraphic analysis, we developed a magnetic reversal stratigraphy for these Norwegian-Greenland Sea sequences. This has allowed independent age determination and has enabled the dinocyst biostratigraphy to be firmly tied into the global geomagnetic polarity timescale (GPTS). The relatively high resolution of this study has enabled identification of dinoflagellate cyst assemblages that have affinities with those from the North Sea and the North Atlantic, which allows regional correlation. Correlation of each site with the GPTS has also allowed comparison of the stratigraphic record preserved in each drill-hole. Hole 913B is the most complete and is the best-preserved record of the Eocene and Oligocene in the Northern Hemisphere high latitudes, and can serve as a reference section for palaeoenvironmental reconstructions of this age interval.

Middle Campanian-lowermost Maastrichtian nannofossils and foraminifers of the northwestern Australian margin

The middle-late Campanian was marked by an increase in the bioprovinciality of calcareous microfossil assemblages into distinct Tethyan, Transitional, and Austral Provinces that persisted to the end of the Maastrichtian. The northwestern Australian margin belonged to the Transitional Province and the absence of key Tethyan marker species such as Radotruncana calcarata and Gansserina gansseri has led petroleum companies operating in the area to use the locally developed KCCM integrated calcareous microfossil zonation scheme. The KCCM zonation is a composite scheme comprising calcareous nannofossil (KCN), planktonic foraminiferal (KPF) and benthonic foraminiferal (KBF) zones. This paper presents the definitions and revisions of Zones KCCM8-19, from the highest occurrence (HO) of Aspidolithus parcus constrictus to the lowest occurrence (LO) of Ceratolithoides aculeus, and builds on our previous early-late Maastrichtian study. The presence of a middle-upper Campanian disconformity is confirmed by microfossil evidence from the Vulcan Sub-basin, Exmouth and Wombat plateaus, and the Southern Carnarvon Platform. In the Vulcan Sub-basin and on the Exmouth Plateau (ODP Hole 762C) the hiatus extends from slightly above the LO of common Rugoglobigerina rugosa to above the LO of Quadrum gothicum. On the Wombat Plateau (ODP Hole 761B) it spans from above the LO of Heterohelix semicostata to above the LO of Quadrum gothicum; and in the Southern Carnarvon Platform the disconformity has its longest duration from above the HO of Heterohelix semicostata to above the LO of Quadrum sissinghii. A significant revision of the events which define Zones KCCM18 and 19 was necessary owing to the observation that the LO of Ceratolithoides aculeus occurs below the HOs of Archaeoglobigerina cretacea and Stensioeina granulata incondita and the LO of common Rugoglobigerina rugosa. In the original zonation these events were considered to be coincident.

Radiolarians from ODP Leg 119, Kerguelen Plateau

Radiolarians are abundant and well preserved in the Neogene of the Kerguelen Plateau. They are common and moderately to well preserved in the Oligocene sequences of Site 738, where the Eocene/Oligocene boundary was observed for the first time in subantarctic sediments, and Site 744. Radiolarians are absent from all glacial sediments from Prydz Bay. Classical Neogene stratigraphic markers were tabulated at all sites. Correlations with paleomagnetic ages were made at Sites 745 and 746 for 26 Pliocene-Pleistocene radiolarian events. Many Miocene to Holocene species are missing from Sites 736 and 737, which were drilled in shallow water (less than 800 m). The missing species are considered to be deepliving forms. Occurrences and relative abundances of morphotypes at six sites are reported. Two new genera (Eurystomoskevos and Cymaetron) and 17 new species (Actinomma kerguelenensis, A. campilacantha, Prunopyle trypopyrena, Stylodictya tainemplekta, Lithomelissa cheni, L. dupliphysa, Lophophaena(?) thaumasia, Pseudodictyophimus galeatus, Lamprocyclas inexpectata, L. prionotocodon, Botryostrobus kerguelensis, B. rednosus, Dictyoprora physothorax, Eucyrtidium antiquum, E.(?) mariae, Eurystomoskevos petrushevskaae, and Cymaetron sinolampas) are described from the middle Eocene to Oligocene sediments at Sites 738 and 744. Twenty-seven stratigraphic events are recorded in the middle to late Eocene of Site 738, and 27 additional stratigraphic datums are recorded, and correlated to paleomagnetic stratigraphy, in the early Oligocene at Sites 738 and 744. Eight radiolarian events are recorded in the late Oligocene at Site 744. New evolutionary lineages are proposed for Calocyclas semipolita and Prunopyle trypopyrena.

Radiolarian assemblages of ODP Leg 117 sites

Significant numbers of radiolarians ranging in age from late middle Miocene to Recent were recovered from six sites drilled on the Oman margin and Owen Ridge. Sparse faunas were recovered from five additional sites on the Oman margin and one site on the Indus Fan. Detailed range charts and biozonations are presented for most sites. The radiolarian assemblages are peculiar in that numerous common tropical forms, some of which are biomarkers, are absent or very rare. In addition, some species not usually found in tropical assemblages are present. These forms, indicative of up welling conditions, fall into three categories: (1) endemic upwelling: species endemic to upwelling and not previously described from the Indian Ocean; (2) displaced temperate: temperate forms not usually found in tropical waters; and (3) enhanced tropical: tropical forms which are more abundant and/or robust in areas of upwelling. Comparison of the Oman margin/Owen Ridge fauna with that recovered from the Peru margin upwelling area (ODP Leg 112) suggests that the assemblage may be globally diagnostic of upwelling conditions. The onset of upwelling is marked by the appearance of siliceous biota at about 11.9 Ma, and there is some indication of a decrease in the strength of the upwelling signal at about 9.6 Ma. A strong pulse in, or strengthening of, the upwelling mechanism is indicated by a marked fauna change at 4.7 Ma. There is a weaker signal, implying a change in upwelling conditions, at about 1.5 Ma.

Benthic foraminiferal record from Santa Barbara basin

The oxygen minimum zone (OMZ) of the late Quaternary California margin experienced abrupt and dramatic changes in strength and depth in response to changes in intermediate water ventilation, ocean productivity, and climate at orbital through millennial time scales. Expansion and contraction of the OMZ is exhibited at high temporal resolution (107-126 year) by quantitative benthic foraminiferal assemblage changes in two piston cores forming a vertical profile in Santa Barbara Basin (569 m, basin floor; 481 m, near sill depth) to 34 and 24 ka, respectively. Variation in the OMZ is quantified by new benthic foraminiferal groupings and new dissolved oxygen index based on documented relations between species and water-mass oxygen concentrations. Foraminiferal-based paleoenvironmental assessments are integrated with principal component analysis, bioturbation, grain size, CaCO3, total organic carbon, and d13C to reconstruct basin oxygenation history. Fauna responded similarly between the two sites, although with somewhat different magnitude and taxonomic expression. During cool episodes (Younger Dryas and stadials), the water column was well oxygenated, most strongly near the end of the glacial episode (17-16 ka; Heinrich 1). In contrast, the OMZ was strong during warm episodes (Bølling/Allerød, interstadials, and Pre-Boreal). During the Bølling/Allerød, the OMZ shoaled to <360 m of contemporaneous sea level, its greatest vertical expansion of the last glacial cycle. Assemblages were then dominated by Bolivina tumida, reflecting high concentrations of dissolved methane in bottom waters. Short decadal intervals were so severely oxygen-depleted that no benthic foraminifera were present. The middle to late Holocene (6-0 ka) was less dysoxic than the early Holocene.

Distribution of diatom species as abundance estimates from vertical multinet hauls from 150 m water depth in the Indian Ocean

During the Indian Ocean Expedition of R/V METEOR phytoplankton samples were taken with a multiple closing net (Multinet) at 103 stations. In this material the diatoms were investigated. In all 247 taxa could be identified which belong to 242 species and 5 varieties of formae of 80 genera. Of these 1 variety, 15 pecies, and 3 genera are newly described. New combinations were made for 18 species, and a number of old combinations was reinstated.