- Tytuł:
- Redox conditions in the Late Cretaceous Chalk Sea: the possible use of cerium anomalies as palaeoredox indicators in the Cenomanian and Turonian Chalk of England
- Autorzy:
-
Jeans, C. V.
Wray, D. S.
Williams, C. T. - Powiązania:
- https://bibliotekanauki.pl/articles/139095.pdf
- Data publikacji:
- 2015
- Wydawca:
- Polska Akademia Nauk. Czytelnia Czasopism PAN
- Tematy:
-
chalk environments
rare earth element (REE) anomalies
methods
palaeoredox indicators
diagenesis
history
pierwiastki ziem rzadkich
REE
anomalie
metody
diageneza
historia - Opis:
- The cerium anomalies preserved in the Chalk have been investigated as possible palaeoredox indicators of the Late Cretaceous Sea and its sediment. This has been based upon over a hundred new rare earth element analyses of selected samples and grain size fractions from the Chalk. Particular attention has been given to the methodology of differentiating between the cerium anomalies preserved in the bioclastic calcite and those in carbonate-fluorapatite preserved in the acetic acid insoluble residues of chalks. Variations in the cerium anomaly of different particle size fractions of uncemented chalks suggest that fractionation of rare earth elements between the Chalk’s seawater and the various organisms that contributed skeletal material to the bioclastic calcite of the Chalk may have occurred. Post-depositional processes of calcite cementation and late diagenetic sulphidisation have had no apparent effect on the cerium anomaly of the acetic acid insoluble residues. The cerium anomalies associated with the acetic acid insoluble residues from (1) an alternating sequence of chalks and marls from Ballard Cliff (Dorset, UK) typical of Milankovitch cyclicity show a marked diagenetic pattern, whereas those from (2) non-volcanic and volcanic marls display a pattern that is best explained by the variations in the availability of phosphorus and the timing of argillisation of volcanic glass during diagenesis. The general conclusion is drawn that the cerium anomalies preserved in the Chalk can provide an insight into the changing palaeoredox conditions in the Late Cretaceous Sea as well as in the pore fluids of its sediments.
- Źródło:
-
Acta Geologica Polonica; 2015, 65, 3; 345-366
0001-5709 - Pojawia się w:
- Acta Geologica Polonica
- Dostawca treści:
- Biblioteka Nauki
Artykuł