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Stratigraphic ranges of foraminiferal assemblages of the Miocene-Pliocene boundary sections in the Niigata oil-fields region of northeastern Japan are described, and their paleoceanographic implications are discussed on the basis of modern foraminiferal ecology and additional geochemical data from the Rock-Eval analysis.
Q-mode cluster analysis grouped five benthic foraminiferal associations named by their dominant taxa: the Guppyella miocenica-Cribrostomoides subglobosus, Karrerulina coniformis-C. subglobosus, Recurvoidella spadix-Cyclammina pseudopusilla, C. pseudopusilla-Uvigerina yabei, and Martinottiella communis associations. Paleoenvironmental implications of each association and their stratigraphic distributions show that the bottom water in the Japan Sea generally changed as follows. 1) In the Late Miocene, bottom waters were depleted in oxygen, cold, and nearly undersaturated with calcium carbonate, conditions consistent with weak communication of seawater between the Japan Sea and the Pacific Ocean. 2) In contrast, Pliocene bottom waters were oxic, occasionally warm and saturated with CaCO3, conditions consistent with enhanced communication of seawater between the Japan Sea and Pacific Ocean perhaps due to raised sea level. Late Miocene hypoxia, which is suggested by the occurrence of Spirosigmoilinella compressa and other abundant infaunal agglutinated foraminifera, may be due to water stratification induced by freshwater input from surrounding land-masses as well as slower influx of Pacific water.
Several synonym relationships are discussed to resolve taxonomic confusions that have prevented studies of biostratigraphy and paleoenvironment. A new species, Cyclammina pseudopusilla, which has been erroneously identified in previous reports, is described herein.
A planktonic foraminiferal zonal scheme is proposed for the internal basinal successions of the Monferrato and Northern Apennines (late Bartonian-early Serravallian). This scheme is based on a synthesis of quantitative analyses performed on the foraminiferal assemblages from 30 stratigraphic sections, cropping out over a distance of 300 km, between the Piedmont and the Northern Apennines. The proposed zonal scheme represents the synthesis, with minor changes, of the biozonations proposed by Novaretti et al. (1995) and Mancin and Pirini (2001) with the addition of unpublished data from some new sections, spanning a broader temporal and geographical range. With respect to the previous regional and standard biozonations, this scheme shows a better biostratigraphical resolution resulting from the replacement of missing or unreliable standard bioevents with new “reproducible” and reliable regional biohorizons. These new events are: LO of muricate species, which identifies the top of the Acarinina spp., Globigerinatheka spp. and Turborotalia cerroazulensis Assemblage Zone because Truncorotaloides rohri is very rare to absent; LO of Turborotalia cerroazulensis lineage, which marks the top of the Turborotalia cerroazulensis Interval Zone because the Hantkenina group is absent; LO of psuedohastigerinids, which marks the upper boundary of the Pseudohastigerina spp. Interval Zone because Cassigerinella chipolensis and Pseudohastigerina micra do not co-occur; the former appears later, in the Globigerina ampliapertura Zone, whereas the latter often disappears near the Eocene/Oligocene boundary; FCO of Paragloborotalia opima opima, which identifies the Paragloborotalia opima opima Subzone boundary (IFP21a/IFP21b) because the LO of Chiloguembelina cubensis is a weakly reliable event; FO of Globoquadrina dehiscens, which marks the Paragloborotalia kugleri Subzone boundary (IFN1a/IFN1b) because the FCO of the Globigerinoides group occurs later; LO of Paragloborotalia kugleri, which identifies the top of the P. kugleri Total Range Zone because the FO of Globigerinoides altiaperturus occurs later and finally, the FO of Globigerinoides trilobus, used to subdivide the interval between the LO of P. kugleri and the LO of Catapsydrax dissimilis, because Globigerinatella insueta is absent.
Other homotaxial biohorizons have also been recognized and introduced among the primary bioevents. These “secondary events” can help in better placing zonal and subzonal boundaries when the primary events cannot be used and in the refinement of the correlations among the different sections.
The validity of this proposal, in our view, consists in the general correspondence between the adopted bioevents and the standard zonal boundaries and therefore in an easy correlation with the various standard schemes. Moreover, the area of applicability of this biozonation could be extended to the surrounding basins and also to coeval Mediterranean successions.<
Charophytes are described and illustrated from the Upper Devonian of Western Australia, including five genera and nine species of which four are new species. Most belong to the Family Umbellinaceae being placed in a new Class Umbellinaphyceae of the Division Charophyta. Representatives of these genera occur in Devonian sediments of Europe, Asia, North America, and Australia. A species of Sycidium described by Karpinsky (1906) as Sycidium panderi is also identified from Western Australia.
δ18O and δ13C values for the calcareous dinoflagellate species Orthopithonella? globosa (Fütterer 1984) Lentin and Williams 1985 and Pirumella krasheninnikovii (Bolli 1974) Lentin and Williams 1993 from latest Campanian and earliest Maastrichtian of ODP Hole 690C (Weddell Sea, Antarctic Ocean) have been studied in order to evaluate the species' depth habitat in the water column and their applicability in paleoceanographic studies. The calcareous dinoflagellates show isotopic values comparable to probably shallow-dwelling planktic foraminifera from the same samples in δ18O, but have an offset of about −5‰ to −7‰ in δ13C. This suggests that calcareous dinoflagellate oxygen isotopes may provide information for paleoceanographic reconstructions of sea-surface water temperatures, whereas their extremely light carbon isotope values are probably due to photosynthetic processes.