High abundance of Archean zircons in Ordovician sandstones in Zealandia: a consequence of global sea‐level fall during the Hirnantian glaciation in Gondwana?

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.