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Tracing the signature of various frontal systems in stable isotopes (oxygen and carbon) of the planktonic foraminiferal species Globigerina bulloides in the Southern Ocean (Indian Sector)

100%

Khare N., Chaturvedi S. K.

Oceanologia

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2012

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tom 54

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nr 2

Twenty-five surficial sediment samples, collected on board ORV Sagar Kanya during her 199th and 200th cruises along a north-south transect between latitudes 9.69◦N and 55.01◦S, and longitudes 80◦E and 40◦ E were studied for isotopic variations (values of δ18O and δ13C) of the indicator planktonic species Globigerina bulloides. The results indicate that from latitudes 9.69◦N to 15◦ S both these isotopes (δ18O and δ13C) fluctuated significantly. Between latitudes from around 15◦S to 30–35◦S δ18O values steadily increased, whereas δ13C showed a decreasing trend. However, to the south of latitudes 30–35◦S, both isotope values showed a similar response with a gradual increase up to latitude 50◦S, beyond which δ18O continued to increase while δ13C declined. The characteristic patterns of the values of both isotopes indicates that the signatures of different water masses are associated with various frontal systems and/or water masses across the transect. The signature of the Polar Front at around latitude 50◦S shows the specific response of the isotopic values (δ18O and δ13C) of G. bulloides. Such a response beyond 50◦S latitude is ascribable to the general decrease in the ambient temperature, resulting in a continuous increase in δ18O values, while δ13C values decrease as a result of reduced photosynthesis in regions approaching higher latitudes owing to low light penetration. To further corroborate our results, those of many such transects from geographically distinct regions need to be studied for isotopic variations in the calcareous shells of planktonic foraminiferal species. The results have the potential to be used as a proxy to assess the movement of frontal systems in southern high latitude regions.

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Borings formed by Late Cretaceous endobiontic foraminifers within larger benthic foraminifers

80%

Nielsen J. K.

Acta Palaeontologica Polonica

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2002

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tom 47

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nr 4

Considering the fossil record, foraminifers constitute one of the most ubiquitous groups in marine deposits due to a high preservation potential of tests. Moreover, borings appear to be widely distributed in the tests. Findings of the borings have potential usefulness as palaeoecological markers and can be significant for taphonomical studies of foraminifers. Formal naming of the borings is needed to further their usefulness, and therefore a new ichnotaxon Curvichnus semorbis igen. et isp. nov. is erected.

3

Patterns of spatio-temporal distribution as criteria for the separation of planktic foraminiferal species across the Danian-Selandian transition in Spain

51%

Arenillas I.

Acta Palaeontologica Polonica

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2012

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tom 57

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nr 2

Danian–Selandian (D–S) planktic foraminiferal taxonomy and paleoecology, including the most problematic index−species of biochronological schemes, are here revised based on qualitative and quantitative data from the Caravaca and Zumaia sections, Spain. As a first step the morphological and microtextural diagnostic characters are revised in order to achieve appropriate morphological distinctions of the investigated species. The analysis of latitudinal preferences of the planktic foraminiferal species deduced from a comparison of their relative abundances at Caravaca (western Tethyan subtropical waters) and Zumaia (central North Atlantic warm temperate waters) in suite with a statistical comparison of quantitative stratigraphic distributions of the species at Caravaca have shown several divergences in their patterns of spatio−temporal distribution (i.e., in their latitudinal preferences and quantitative stratigraphic distributions). This analysis allowed taxonomical separation of 41 species from the following genera: Eoglobigerina, Subbotina, Parasubbotina, Globanomalina, Luterbacheria, Acarinina, Igorina, Morozovella, Praemurica, Chiloguembelina, and Zeauvigerina. Morphologically convergent species pairs such as Acarinina trinidadensis and Praemurica inconstans, Acarinina praecursoria and Acarinina uncinata, Morozovella conicontruncata and Morozovella angulata, or Morozovella cf. albeari and Igorina albeari, are well differentiated using aforementioned criteria. Since some of the species are index−taxa, the taxonomic refinements are essential to clarify and compare the planktic foraminiferal zonations from the Danian–Sealandian transition. A new lower/higher (L/H) latitude taxa ratio is proposed for paleoclimatic interpretations based on the paleoecological and quantitative studies. Fluctuations in L/H ratio in the Caravaca section suggest three climate warming events during the D–S transition, one of them probably occurring at the D–S boundary.

Ograniczanie wyników

2 Acta Palaeontologica Polonica

1 Oceanologia

1 Arenillas I.

1 Chaturvedi S. K.

1 Khare N.

1 Nielsen J. K.

2 2012

1 2002

Tracing the signature of various frontal systems in stable isotopes (oxygen and carbon) of the planktonic foraminiferal species Globigerina bulloides in the Southern Ocean (Indian Sector)

Borings formed by Late Cretaceous endobiontic foraminifers within larger benthic foraminifers

Patterns of spatio-temporal distribution as criteria for the separation of planktic foraminiferal species across the Danian-Selandian transition in Spain