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硅质岩部分由黑色叠层硅质岩和红色硅质岩组成。根据牙形刺生物地层学，黑色硅质岩的时代为斯帕西期，红色硅质岩的时代为早-中安尼西期。为了揭示层状硅质岩的沉积相和微结构，对通过该剖面采集的HF处理的硅质岩板块进行了高分辨率的扫描电子显微镜观察。已识别出三种微相：普通远洋硅质岩相(G2)、远洋硅质粘土相(E1/E2)和生物硅质组成相(G1)，其中含有丰富的海绵针状物和放射虫贝壳。G2相具有较高的生物硅质成分(10-30%)，主要表现为溶解和/或保存较差的微体化石。相E1/E2为硅质粘土基质，生物硅质壳和针状物含量较低(1-10%)。G1相以致密堆积的非胶结海绵针状物和球状放射虫壳体为特征。

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.