High abundance of Archean zircons in Ordovician sandstones in Zealandia: A response to Hirnantian Glaciation?tled Item

In the Takaka Terrane of South Island, New Zealand, Wangapeka Formation (Katian to Hirnantian) quartz sandstones contain detrital zircons with strikingly high (15-25%) proportions of early Paleoproterozoic and Archean ages, levels not seen elsewhere in early Paleozoic rocks of Zealandia and southeast Australia. It is proposed that the sudden appearance of these old zircons, and their equally rapid decline in the Silurian, reflects sea-level fall during the Hirnantian Glaciation which stimulated erosion of a hitherto hidden, local ancient basement complex.

在新西兰南岛的塔卡卡地体（Takaka Terrane）中，瓦纳佩卡组（Wangapeka Formation，时代为凯迪期（Katian）至赫南特期（Hirnantian））的石英砂岩含有碎屑锆石，其中古元古代早期及太古代年龄的锆石占比高达15%~25%，该占比水平显著偏高，且在西兰大陆（Zealandia）与澳大利亚东南部的早古生代岩石中均未被观测到。有研究提出，这类古老锆石的突然出现，以及它们在志留纪（Silurian）的丰度同样快速下降，反映了赫南特冰期（Hirnantian Glaciation）期间的海平面下降——该事件曾促使此前隐蔽的本地古老基底杂岩遭受侵蚀。