ABSTRACT

Permian Parapara Group and Triassic Topfer Formation are small clastic sedimentary outliers that rest on Cambrian to Devonian basement terranes in the Western Province of South Island, New Zealand. New detrital zircon U-Pb age datasets from three Parapara sandstones, one Topfer sandstone and four age-equivalent eastern Australian sandstones reveal age and provenance information about former Gondwana intracontinental basins. Youngest significant zircon age populations of 264 ± 6 and 261 ± 2 Ma in two Parapara Group sandstones and 215 ± 2 Ma in the Topfer sandstone match fossil ages and indicate broadly syn-depositional igneous activity. The provenance of the igneous detritus was probably the nearby Median Batholith and/or its volcanic equivalents. Zircons in a third Parapara sandstone are predominantly Cambrian and Precambrian in age and represent a separate petrofacies with a local Western Province basement terrane provenance. Intra-basin provenance switching between Gondwana margin arc and older basement sources is thus documented in Gondwana basin sequences in Zealandia, as well as those in Australia and Antarctica.

摘要

二叠纪 Parapara 组和三叠纪 Topfer 组是位于新西兰南岛西部省寒武纪至泥盆纪基底地体的小型碎屑沉积异常值。来自三个 Parapara 砂岩、一个 Topfer 砂岩和四个年龄相当的澳大利亚东部砂岩的新碎屑锆石 U-Pb 年龄数据集揭示了前冈瓦纳陆内盆地的年龄和物源信息。两个 Parapara 组砂岩中 264 ± 6 和 261 ± 2 Ma 和 Topfer 砂岩中 215 ± 2 Ma 的最年轻显着锆石年龄群与化石年龄相匹配，表明广泛的同沉积火成活动。火成岩碎屑的来源可能是附近的中位岩基和/或其火山等价物。第三个帕拉帕拉砂岩中的锆石在年龄上主要是寒武纪和前寒武纪，代表了一个单独的岩相，具有当地西部省的地下地层物源。因此，在西兰大陆以及澳大利亚和南极洲的冈瓦纳盆地序列中记录了冈瓦纳边缘弧和较老的基底源之间的盆地内物源转换。