K-Ar dating of Permian and Tertiary igneous activity in the Southeastern Sydney Basin, New South Wales
Titel:
K-Ar dating of Permian and Tertiary igneous activity in the Southeastern Sydney Basin, New South Wales
Auteur:
Facer, R. A. Carr, P. F.
Verschenen in:
Australian journal of earth sciences
Paginering:
Jaargang 26 (1979) nr. 1-2 pagina's 73-79
Jaar:
1979
Inhoud:
The southern part of the Sydney Basin of New South Wales is comprised mainly of Permian and Triassic marine to freshwater clastic sedimentary rocks. Within this sequence there are six latite extrusive units, several medium-sized monzonite intrusions and a large number of small to medium-sized basic to intermediate intrusions. Thin basaltic flows were extruded onto the Tertiary topographic surface. All of these rocks are relatively undeformed. Radiometric (K-Ar) dating has previously been carried out on Mesozoic and Tertiary intrusions and flows of the southwestern portion of the Sydney Basin. However, relatively few Permian, and no post-Permian, K-Ar dates have been published for the southeastern portion of the basin. The present investigation provides nine K-Ar dates from the latter area. Four extrusive and intrusive units have been confirmed as Permian in age (238 ± 6; 241 ± 4; 245 ± 6; and 251 ± 5 m.y.). Five post-Permian (on stratigraphic criteria) intrusions yielded Tertiary ages (26.2 ± 3.0; 47.9 ± 2.5; 49.0 ± 4.0; 49.4 ± 2.0; and 58.8 ± 3.5 m.y.). The Permian ages agree with previously published K-Ar data from the southeastern Sydney Basin, and the Tertiary ages complement and extend the data from the southwestern portion of the basin. However, no Mesozoic K-Ar dates were obtained from the southeastern Sydney Basin. The Tertiary intrusions may have been emplaced as a result of rifting between Australia and New Zealand, or between Australia and Antarctica, or both.
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