Correlation of Radiometric and Biostratigraphic Timescales for the Triassic and Jurassic Murihiku Supergroup of New Zealand

中生代早期辐射测量和生物地层时间尺度的相互校准尚未建立。 三叠纪和侏罗纪部分地区的阶段边界的绝对年龄分配的不确定性可能超过 30 Ma。 该提案寻求对新西兰 Murihiku 超群保存完好的含化石地层中的玻璃质凝灰岩层进行高精度锆石 U-Pb 年龄测定的支持。 这个厚的碎屑层序主要由海洋火山岩组成，跨越了三叠纪和侏罗纪的大部分时间，并且可以根据几乎世界性的菊石和翼类双壳类在关键点与国际岩柱进行关联。 Murihiku 超群中三叠统至上三叠统部分内 13 个凝灰岩层间隔约 6 公里，初步锆石年龄范围为 232 Ma 至 204 Ma。 根据逐步溶解实验获得的高精度 Pb/Pb 年龄，Monotis 的 FAD 和 LAD 被限制在 226 Ma 至 218 Ma 内。 建议完成对 Murihiku 超群的中三叠统和上三叠统部分的详细、全面的研究，并将采样范围扩大到包括该层序的下三叠统和侏罗统部分。 这项工作连同该剖面中砾岩中花岗岩碎屑的高精度测年，将提供有关沉积速率和物质在深成-隆起-侵蚀-搬运-沉积之间的循环速率的信息，并将极大地有助于了解盆地演化的动态。

Intercalibration of radiometric and biostratigraphic time scales for the early Mesozoic is not well established. Uncertainties in absolute age assignments to stage boundaries for parts of the Triassic and Jurassic may exceed 30 Ma. This proposal seeks support for high-precision zircon U-Pb age dating of vitric tuff beds that occur within well-preserved fossiliferous strata of the Murihiku Supergroup of New Zealand. This thick clastic succession comprises mainly marine volcanogenic rocks that span most of Triassic and Jurassic time and can be correlated to the international column at key points on the basis of virtually cosmopolitan ammonoids and pteroid bivalves. Preliminary zircon ages from 13 tuff beds spaced through ~6 km of section within the Middle to Upper Triassic portion of the Murihiku Supergroup range from 232 to 204 Ma. On the basis of high-precision Pb/Pb ages from step-wise dissolution experiments, the FAD and LAD for Monotis are constrained to occur within 226 Ma to 218 Ma. It is proposed to complete detailed, comprehensive study of the Middle and Upper Triassic sections of the Murihiku Supergroup, and extending the range of our sampling to include the Lower Triassic and Jurassic portions of the sequence. This work, along with high-precision dating of granitoid clasts from conglomerates in the section, will provide information on sedimentation rates and cycling rates of material between plutonism-uplift-erosion- transport-deposition, and will contribute significantly to understanding the dynamics of basin evolution.