A probable Early Triassic age for the Miers Bluff Formation, Livingston Island, South Shetland Islands
Fifteen samples of very low-grade mudstones from two widely separated sections in the Miers Bluff Formation on Hurd Peninsula yield an Rb-Sr errorchron (MSWD=8.9) corresponding to an age of 243 ± 8 Ma. This age is interpreted as representing effective homogenization, on a kilometres scale, during tu...
Published in: | Antarctic Science |
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Main Authors: | , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Cambridge University Press (CUP)
1994
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Subjects: | |
Online Access: | http://dx.doi.org/10.1017/s095410209400060x https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S095410209400060X |
Summary: | Fifteen samples of very low-grade mudstones from two widely separated sections in the Miers Bluff Formation on Hurd Peninsula yield an Rb-Sr errorchron (MSWD=8.9) corresponding to an age of 243 ± 8 Ma. This age is interpreted as representing effective homogenization, on a kilometres scale, during turbidite deposition and diagenesis in early Triassic times. The initial 87 Sr/ 86 Sr ratio 0.7085 ± 0.0003 represents a mature crustal source and is consistent with the re-working of material comparable to that eroded from the Chilean fore-arc accretionary complex. Four further samples, collected near to a zone of quartz-carbonate veins, lie to the right of the errorchron, with two samples having unusually low Sr contents. These samples fall on a 113 Ma reference line and indicate metasomatic disturbance in Cretaceous times. Metasomatism was probably related to hydrothermal alteration accompanying widespread silicification and quartz veining on western Hurd Peninsula. A mid-to late Cretaceous age for metasomatic disturbance agrees with field relations which indicate that the hydrothermal activity preceded or was coeval with the mid- to late Cretaceous period of volcanism on Livingston Island. Hence the hydrothermal rocks are not related to the Eocene Barnard Point pluton, as previously suggested. |
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