Wyniki wyszukiwania - Biblioteka Nauki

Nowa wersja platformy, zawierająca wyłącznie zasoby pełnotekstowe, jest już dostępna.
Przejdź na https://bibliotekanauki.pl

Ograniczanie wyników

Znaleziono wyników: 3

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Sedimentation of Lower Toarcian (Lower Jurassic) brackish deposits from the Częstochowa-Wieluń region (SW Poland)

100%

Leonowicz P.

Acta Geologica Polonica

2011

tom Vol. 61, no. 2

215-241

The Lower Toarcian Ciechocinek Formation from the Częstochowa-Wieluń region is composed of poorly consolidated mudstones, claystones and siltstones with subordinate sandstone intercalations. The succession is represented by twelve lithofacies grouped into seven facies associations of a shallow brackish marine basin with an embayment character. The sedimentation was dominated by clay and silt deposition from low-density suspension flows, spreading out from river mouths, and from suspension clouds whirled up during storms. Sand intercalations mark episodes of storms, removing coarser material from nearshore to more distal settings, migration of elongated sand bars, as well as sedimentation at river mouths and on sandy shoals. The deposition was affected by three main factors: (1) progradation and displacement of river mouths; (2) river discharge fluctuations;and (3) short-term weather changes.

Origin of siderites from the Lower Jurassic Ciechocinek Formation from SW Poland

100%

Leonowicz P.

2007

tom Vol. 51, No 1

67-78

Sideritic rocks, which are characteristic constituents of muddy-silty deposits of the Lower Jurassic Ciechocinek Formation, occur commonly as layers, lenses and small irregular concretions composed of siderite mudstone and siltstone as well as less common lenses of sideritic sandstones. Three types of siderite cement were observed in thin sections: fine-crystalline variety (SF), coarse-crystalline rhombohedra (SR) and fine-crystalline biogenic aggre gates (SA). In all these types BSE analysis revealed compositional zonation of crystals, with in ternal parts enriched in Mg, Mn and Ca and outer zones almost pure siderite. d13C values and chemical composition of siderites combined with the presence of early diagenetic pyrite indicate that siderite crystallized from brackish marine-derived solutions; only in the case of two samples from the lower part of the Ciechocinek Formation the fresh water origin cannotbe excluded. Mn and Fe were supplied by rivers and released by Fe- and Mn-reduction in suboxic zone, whereas Mg and Ca were derived from sea water, which infiltrated into the sediment. Crystal zonation resulted from the diagenetic evolution of pore water as the sediment was buried. Similar composition and development of siderite crystals from different parts of one layer indicate that siderite precipitated simultaneously throughout the whole horizon. Precipitation began from the formation of numerous nuclei and continued by growth of crystals onto them. It could begin already in the iron reduction subzone and continued in the sulphate reduction and methanogenesis zones.

Cysty Dinoflagellata z odsłonięć liasu w Kozłowicach i Boroszowie (Wyżyna Woźnicko-Wieluńska)

63%

Barski M. , Leonowicz P.

tom Vol. 50, nr 5

411-414

Opisanie zespołu cyst Dinoflagellata z badanych próbek przyczyniło się do sprecyzowania stratygrafii utworów ilastych w odsłonięciach w Kozłowicach i Boroszowie. Charakterystyczne taksony dinocyst wskazaly też na przeławicanie się w profilu osadów przywiązanych do środowisk sedymentacji morskiej i brakicznej. Analiza palinofacjalna wskazuje na bliskie położenie badanego fragmentu basenu sedymentacyjengo w stosunku do obszaru lądowego. Tam, gdzie w próbkach zanotowano morski gatunek Luehndea spinosa, skład palinofacji wykazał redukcję fitoklastów pochodzenia lądowego na korzyść lżejszych - bardziej lotnych i pławnych ziaren pyłku oraz spor.

The described assemblage ofDinoflagellate cysts enabled to pinpoint the stratigraphic position ofclaystones cropped out olozloivice and Boroszów. The specific taxa ofdinoflagellates indicated the presence ofinterbedding marine and brackish sediments o://! the sections studied. Thepalynofacies analysis confirmed the proximal location of these sections in sedimentary1 basin. The environmental suggestions derived from the dinocyst assemblage are supported by palynofacies indicators.