Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: stratigraphical distribution

Sortuj według:

Ogranicz wyniki do:

Quaternary Ostracoda of the southern Baltic Sea (Poland) : taxonomy, palaeoecology and stratigraphy

Krzymińska J., Namiotko T.

Polish Geological Institute Special Papers

2013

Vol. 29

1--76

To reconstruct environmental changes in water hydrology and salinity in the Late Glacial to Holocene of the Polish part of the southern Baltic Sea, the distribution of ostracod valves was studied in 85 sediment cores collected from both the open sea and the coastal zone. The studied sequences yielded 30 species, of which six appeared new to the Quaternary Baltic deposits of Poland. The most common species were non-marine Candona neglecta (present in 52 cores), C. candida (31 cores) and Cytherissa lacustris (30 cores) as well as holeuryhaline Cyprideis torosa (52 cores). Initial Late Glacial–early Holocene palaeoassemblages dominated by inhabitants of the profundal/sub-littoral zones of modern oligo-mesotrophic lakes (C. lacustris, C. neglecta, C. candida) or species typical of the lacustrine littoral (Darwinula stevensoni, Limnocythere inopinata, Ilyocypris decipiens) were replaced in middle and late Holocene by the assemblages dominated by brackishwater species (Cyprideis torosa, Cytheromorpha fuscata). The revealed successional transitions indicate the fundamental environmental change in the history of the Baltic, when marine waters entered the Baltic Basin and caused the major hydrological shift from the freshwater system into the brackish-marine Littorina Sea. The present results consolidate inferences based on previously published ostracod data on the environmental transformation in the southern Baltic Sea.

Wcelu odtworzenia zmian środowiskowych w późnym glacjale i w holocenie na terenie polskiej części południowego Bałtyku zbadano rozmieszczenie małżoraczków w osadach 85 rdzeni pochodzących zarówno z obszarów otwartego morza, jak również ze strefy przybrzeżnej. W badanych osadach znaleziono łącznie 30 gatunków, z których sześć okazało się nowymi dla czwartorzędu polskiej części Bałtyku. Najczęstszymi były gatunki słodkowodne: Candona neglecta (występująca aż w 52 rdzeniach), C. candida (w 31 rdzeniach) i Cytherissa lacustris (w 30 rdzeniach), a także gatunek holeuryhalinowy Cyprideis torosa (w 52 rdzeniach). Pierwotne zgrupowania późnego glacjału i wczesnego holocenu, zdominowane przez gatunki strefy profundalu/ sublitoralu jezior oligo-mezotroficznych (C. lacustris, C. neglecta, C. candida) lub gatunki charakterystyczne dla litoralu jezior (Darwinula stevensoni, Limnocythere inopinata, Ilyocypris decipiens), w środkowym i późnym holocenie zostały zastąpione zgrupowaniami zdominowanymi przez gatunki słonawowodne–morskie (Cyprideis torosa, Cytheromorpha fuscata). Odnotowane prawidłowości sukcesyjne fauny małżoraczków wskazują na fundamentalne zmiany środowiskowe Morza Bałtyckiego, kiedy to wody morskie wdarły się do basenu bałtyckiego, powodując przekształcenie zbiornika słodkowodnego w słonawowodne Morze Litorynowe. Uzyskane wyniki poszerzyły wnioski zawarte w opublikowanych danych dotyczących małżoraczków i przemian środowiskowych południowego Bałtyku.

Stratigraphical distribution of Jurassic brachiopods in the Bakony Mountains (Hungary)

Voros A., Dulai A.

Volumina Jurassica

2006

Vol. 4, no. 1

247-248

The Jurassic brachiopod fauna of the Bakony Mountains (Transdanubian Central Range) is well-known: several thousands specimens were collected from the different stages. The collecting work encompassed the whole Jurassic sequence except the Callovian and Oxfordian which are mainly represented by radiolarite. Brachiopods were collected together with ammonites and this offered an exceptional possibility to record their stratigraphic distribution. The ooidal-oncoidal, shallow-water Hettangian Kardosret Limestone yielded 10 (mainly terebratulid) species. The Lower Sinemurian Pisznice Limestone and the cherty, crinoidal Isztimer Formation yielded 46 species of rhynchonellids, spiriferinids and terebratulids. The gradual diversification continued: the Upper Sinemurian Hierlatz Limestone is extremely rich in brachiopods and 66 species were found at three localities. The Pliensbachian is the best studied stage (101 species); more than a dozen sections were collected in four different lithologies: red, condensed, manganiferous limestone; Hierlatz Limestone; crinoidal cherty limestone; Ammonitico Rosso type limestone. The four brachiopod orders (Rhynchonellida, Athyridida, Spiriferinida and Terebratulida) are profusely represented but the bulk fauna is dominated by the species Linguithyris aspasia. The red limestone facies after the Early Toarcian anoxic event yielded only very few specimens of the above mentioned species. The Aalenian Ammonitico Rosso type limestone and greyish siliceous limestone are totally devoid of brachiopods. The same litologies in the Lower Bajocian yielded only a few brachiopods. The Middle and Upper Bajocian shows more diverse lithology (pelagic limestone; red, manganiferous limestone; Hierlatz-like limestone; radiolarite) with the bloom of brachiopods from the Humphriesianum Zone until the end of the Bajocian. Red, Ammonitico Rosso type limestones are widespread in the Kimmeridgian but brachiopods are extremely rare. This limestone is predominant in the Tithonian but Hierlatz-like limestone and white micritic limestone also occur. Brachiopods (mostly pygopids) are especially abundant and diverse in the Hierlatz-like limestones.