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| Titel: |
Dating of glauconite from the Ngalia Basin, Northern Territory, Australia |
| Auteur: |
Cooper, J. A. Wells, A. T. Nicholas, T. |
| Verschenen in: |
Australian journal of earth sciences |
| Paginering: | Jaargang 18 (1971) nr. 2 pagina's 97-106 |
| Jaar: |
1971-07 |
| Inhoud: |
Rb-Sr and K-Ar measurements have been made on five glauconite samples from the near basal Treuer Member of the Vaughan Springs Quartzite of the Ngalia Basin, Northern Territory, Australia. Comparison of results between and within the two groups of data demonstrates that variable losses of radiogenic strontium and argon have occurred, but allows a minimum age of 1280 m.y. to be calculated for the member. Sedimentation began in the Ngalia Basin shortly before the time of deposition of this member. Regional correlations suggest that this minimum age applies to the adjacent Amadeus Basin as well. Measurements were also made on glauconite from a single sample of the Lower Palaeozoic Djagamara Formation which is in the same sequence. It yields a mid-Ordovician K-Ar age which generally agrees with the broad range of post-Lower Cambrian to pre-Carboniferous age determined from fossil evidence in bounding formations. A low Rb/Sr ratio prevented calculation of a Rb-Sr age, but the combination of K-Ar age and Rb-Sr measurements allowed an accurate initial 87Sr/86Sr ratio of .739 to be determined. This is much greater than ocean water values, and it appears that such information on young samples and/or those of low Rb/Sr ratio could help define the source material for glauconite formation. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 1 van 11 gevonden artikelen
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