Search results

Filters

  • Journals
  • Authors
  • Keywords
  • Date
  • Type

Search results

Number of results: 10
items per page: 25 50 75
Sort by:

Abstract

During the 2004 summer season, 14 sediment samples were collected in Kongsfjorden and Isfjorden, West Spitsbergen, from 6 down to 345 m water-depth (mwd). The samples yielded abundant assemblage of monothalamous foraminifera, belonging to almost 40 morphotypes. Our qualitative (>125 um) and quantitative data (125-500 um) allowed to distinguish three water-depth related assemblages in both Kongsfjorden and Adventfjorden (branch of Isfjorden), indicating that soft-walled monothalamous foraminifera show similar habitat gradation along fjord axis as calcareous and robust agglutinated taxa. Among the monothalamous foraminifera, the subtidal assemblage (6 mwd) was dominated by various unidentified allogromiids. The second, shallow-water assemblage (44-110 mwd) was dominated by Psammophaga sp. 1-3, Hippocrepinella crassa, Hippocrepinella cf. hirudinea, and large Gloiogullmia sp. 2. The deep-water (150-345 mwd) monothalamous assemblage was dominated by Psammophaga sp. 4, pear-shaped Hippocrepina sp., Hippocrepina indivisa, and long Cylindrogullmia sp. 2, as well as large agglutinated species Hyperammina subnodosa with attached Tholosina bulla, Hyperammina fragilis and Lagenammina sp.
Go to article

Abstract

Bowseria arctowskii gen. et sp. nov., a new organic-walled monothalamous (single-chamber) foraminiferan is described from samples collected in Admiralty Bay (King George Island, West Antarctica) at 100- 200 m water-depth (mwd). The species is characterized by a large (1- 2 mm) elongate theca with a single terminal aperture. Molecular phylogenetic analyses, based on partial small subunit rDNA sequences, indicate that the new species belong to a clade of single-chambered foraminifers that branch as a sister group to the multi-chambered textulariids and rotaliids. The most closely related to the new species is an undetermined allogromiid from under the Ross Ice Shelf.
Go to article

Abstract

The fusulinid foraminifers of Schellwienia arctica (Schellwien, 1908) have been investigated from Polakkfjellet Mt., south Spitsbergen, and used as biostratigraphic marker for the latest Carboniferous earliest Permian strata of the Treskelodden Formation. A series of thin sections enable to investigate the internal structure and growth pattern of individual specimens. The observed variation of growth suggests dynamic environmental conditions at the investigated location and most likely over one-year long life span of this foraminifer.
Go to article

Abstract

During the austral summer of 2002/2003 the author collected 38 marine and/or glacio-marine sediment samples from Admiralty Bay on King George Island (South Shetland Islands, West Antarctica). Recent “living” (Rose Bengal stained) and “dead” (subfossil) benthic foraminifera represented by 105 species belonging to 65 genera are recognized in samples from water depths of up to 520 m. They show large spatial variability. Four distinctive foraminiferal zones within the fjord of Admiralty Bay were recognized and analyzed in terms of environmental conditions. The zones are: restricted coves, open inlets, intermediate-, and deep-waters. The major environmental factors, which dictate foraminiferal distribution, are closely related to bathymetry and distance to open sea. Sediment composition and chlorophyll content appear to have minor influence on foraminiferal communities. Most diverse, deep-water faunas dominate water-depths below 200 m , which seems to be the lowest limit of atmospheric and meltwater influence. In waters shallower than 200 m , environmental features, affecting distribution of various benthic foraminiferal assemblages, appear to be sedimentation rate and hydrographic isolation. The results of this study gives promise to use the Admiralty Bay foraminiferal distribution pattern as a paleoenvironmental tool for shallow- to intermediate-water Quaternary marine research in fjord settings of the South Shetland Islands.
Go to article

Abstract

During the late 2007 austral summer, 20 sediment samples were collected in Admiralty Bay (King George Island, South Shetlands, West Antarctica) from 8 down to 254 m water-depth (mwd). The samples yielded abundant assemblage of monothalamous benthic foraminifera, belonging to at least 40 morphospecies. They constituted the first such collection from Antarctic Peninsula fjords and provided a new insight into this group’s diversity and distribution. Among organic-walled taxa, Psammophaga sp., Allogromia cf. crystallifera, and three morphotypes of Gloiogullmia were especially abundant. Agglutinated forms were dominated by Hippocrepinella hirudinea, Psammosphaera spp., Lagenammina spp., and various mudballs. Although, the majority of the morphotypes were known from other high-latitude locations, some were reported for the first time. Our quantitative data (>125 µm) showed the greatest differences between monothalamous foraminifera assemblages at shallowest water depths above 50 mwd. The deepest assemblages from between 179 and 254 mwd, were most similar, suggesting uniform near-bottom conditions at ~200 mwd throughout the Admiralty Bay.
Go to article

Abstract

After several years of research, the foraminiferal fauna of Admiralty Bay (King George Island, South Shetland Islands) has become themost studied fiord in West Antarctica with respect to foraminifera. As such, it provides actualistic data for better understanding of paleoenvironmental records from this dynamically changing area. Over a few years, the bay was systematically sampled down to 520 m water depth, for multi−chambered and mono− thalamous benthic foraminifera, including soft−walled allogromiids often overlooked in for− mer studies. Altogether, 138 taxa were identified, and three new taxa described. This paper aims to integrate these results, put them into a broader perspective, and supplement them with information that was not presented to date. Most notably, a record of the vertical distribution of Rose Bengal stained foraminifera below the sediment surface and the proportions of soft and robustly−testate forms at different sites are described.
Go to article

Abstract

Planktonie foraminifera of the genera Chiloguembelina Loeblich and Tappan. Globigerina d'Orbigny and Globorolalia Cushman are reported from glacio-marine sediments of the Low Head Member (Polonez Cove Formation, Oligocene) of King George Island (South Shetland Islands). West Antarctica. The foraminifer assemblage comprises two stratigraphically important species: Globigerina angiporoides Hornibrook and Chiloguembelina cubensis (Palmer), which indicate the Upper Eocene — Lower Oligocene age. Taking into account specific composition, this planktonie assemblage may tentatively be correlated with the Globigerina angiporoides Zone of New Zealand. Australia. South Pacific and South Atlantic, which belongs to the Lower Oligocene (see Jenkins 1985).
Go to article

Abstract

Recent foraminifera represented by 24 species belonging to 20 genera are recognized in marine and/or glacio-marine sediment samples collected at water depths of up to 75 m in Goulden Cove (Admiralty Bay) on King George Island, West Antarctica. The foraminifer assemblages are dominated by benthic taxa, such as Globocassidulina biora and Miliammina arenacea, the two most abundant species in the studied biocenosis.
Go to article

Abstract

Modern hydrology of a typical Arctic fjord (Hornsund, SW Spitsbergen, Sval− bard) was investigated and compared with commonly used in paleoceanography proxies: benthic foraminiferal assemblages and their stable isotope (#2;18O and #2;13C) composition. The benthic foraminifera from Hornsund comprised 45 species and 28 genera. Their spatial variations follow the zonation pattern, resulting from the influence of Atlantic water at the fjord mouth and glacial meltwaters at the fjord head. At the mouth of the fjord, the total number of species and the contribution of agglutinating species were the highest. In the in− ner part of fjord, the foraminiferal faunas were poor in species and individuals, and aggluti− nating species were absent. “Living” (stained) foraminifera were found to be common throughout the short sediment cores (~10 cm long) studied. The stable isotope values of #2;18O and #2;13C were measured on tests of four species: Elphidium excavatum forma clavata, Cassidulina reniforme, Nonionellina labradorica and Cibicides lobatulus. The results con− firmed the importance of species−specific vital effects, particularly in the case of C. loba− tulus. The variability in the isotopic composition measured on different individuals within a single sample are comparable to isotopic composition of the same species test between sam− pling stations. The temperatures and bottom water salinities calculated from #2;18O values in different foraminifera tests mirrored those recorded for bottom waters in the central and outer fjords relatively well. However, in the case of the inner fjord, where winter−cooled bottom waters were present, the calculated values from #2;18O were systematically higher by about 2#3;C. The obtained results imply that particular caution must be taken in interpretation of fjord benthic foraminifera assemblages in high resolution studies and in selection of ma− terial for isotope analyses and their interpretation in cores from inner fjords or silled fjords, where winter−cooled waters may be present.
Go to article

Abstract

Micropaleontological and palynological samples from three Cenozoic diamictites at Cape Lamb, Vega Island, James Ross Basin were analysed. Fossiliferous samples yielded reworked and autochthonous a ssemblages of Mesozoic calcareous nannofossils, impoverished Cretaceous foraminifer a together with Neogene species, as well as Late Cretaceous dinoflagellate cysts, pollen, spores and abundant Cenozoic microforaminiferal linings. The recovered nannoflora indicates Early Cretaceous (Hauterivian–Albian) and Late Cretaceous (Santonian–Early Campanian) ages, suggesting an in tensive reworking of marine sediments. The presence of the Early Cretaceous species Nannoconus circularis Deres et Acheriteguy in the diamictite represents its first record for the James Ross Basin. The scarce foraminiferal fauna includes Pullenia jarvisi Cushman, which indicates reworking from lower Maastrichtian–lower Paleocene sediments, and also the Neogene autochthonous Trochammina sp. aff. T. intermedia. The inner−organic layer observed inside this specimen appears to be identical to microforaminiferal linings recovered from the same sample. Palynomorphs found in the studied samples suggest erosion from the underlying Snow Hill Island and the López de Berto − dano Formation beds (upper Campanian–upper M aastrichtian). These recovered assemblages indicate either different periods of deposition or reworking from diverse sources during Cenozoic glaciation, originating in James Ross Island and the Antarctic Peninsula with the influence of local sediment sources.
Go to article

This page uses 'cookies'. Learn more