Reconstruction of Mesozoic Ocean Plate Stratigraphy and biogenic silica history in the high-latitude southern Panthalassa Ocean

奥克兰附近莫图塔普岛上的层状燧石剖面由黑色层状燧石和红色燧石组成。根据牙形石生物地层学，黑色硅质岩的时代为Spathian期，红色硅质岩的时代为早-中Anisian期。为了揭示层状硅质岩的沉积相和微结构，对通过该剖面收集的HF处理的硅质岩板进行了高分辨率SEM观察。研究区主要划分出3种微相：普通硅质岩相（G2）、硅质粘土相（E1/E2）和生物硅质组分相（G1）。相G2具有高生物硅质组分（10-30%），其表现为大多溶解和/或保存不良的微体化石。E1/E2相具有硅质粘土基质，生物硅质贝壳和骨针含量低（1-10%）。相G1的特点是密集，非胶结海绵骨针和球形放射虫壳。

The bedded chert section on Motutapu Island, near Auckland is comprised of black laminated chert and red chert. Based on conodont biostratigraphy, the black chert is Spathian and the red chert is early to middle Anisian in age. In order to unravel the sedimentary facies and microstructure of the bedded chert, high-resolution SEM observations were carried out on HF-treated chert slabs that were collected through the section. Three microfacies have been recognized: ordinary pelagic chert facies (G2), pelagic siliceous clay facies (E1/E2) and biogenic siliceous constituent facies (G1) comprising abundant sponge spicules and radiolarian shells. Facies G2 has a high biosiliceous component (10-30%) which appears as mostly dissolved and/or poorly preserved microfossils. Facies E1/E2 has a siliceous clay matrix with a low content (1-10%) of biosiliceous shells and spicules. Facies G1 is characterized by densely packed, non-cemented sponge spicules and spherical radiolarian shells.