Record details

Title
    Factors influencing the Al2O3/Na2O ratio in Paleozoic siliceous shales
Statement of responsibility
    Jaroslav Dvořák
Author
    Dvořák, Jaroslav
Language
    anglicky
Source title - serial
    Věstník Českého geologického ústavu (Bulletin of the Czech Geological Survey)
Vol./nr.
    Vol. 72, no. 1
Pages
    p. 57-59
Year
    1997
Notes
    2 obr., 1 tab., 9 bibl.
    České resumé
    Zkr. název ser.: Věst. Čes. geol. Úst. (Bull. Czech geol. Surv.)
Subject group
    břidlice jílová
    evapority
    index zralosti
    karbon-spodní
    moravskoslezský devon a spodní karbon
    sedimentace mořská
    silur
Geographical name
    ČR-Morava
Keyword
    Al2O3/Na2O
    Factors
    Influencing
    Paleozoic
    Ratio
    Shales
    Siliceous
Abstract (in english)
   The Al2O3/Na2O ratio can be considered good evidence for the chemical maturity of clastic sediments. It represents the ration of the most and least stable oxides. The values between 12 and 15 can be taken as boundary limits between mature and immature clayey sediments (see Kukal 1985). Some difficulties might arise in the evaluation of paleozoic siliceous shales. Black siliceous graptolithic shales show an anomalously low Al2O3/Na2O ratio. Moravian Lower Carboniferous shales can be help in the explanation of this anomaly. It is supposed that they were deposited in shalow bays with warm water and intense evaporation. Chemical weathering released silica and also mobile sodium, which were washed into the basin. The sodium could have been fixed in the structure of clay minerals
Contributor
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
    U
Entered date
    21. 2. 2008
Import date
    8. 8. 2012