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

在奥克兰附近的Motutapu岛上，层状燧石部分由黑色层状燧石和红色燧石组成。根据牙形石生物地层学，黑色燧石的年龄为斯帕西亚期，红色燧石的年龄为早-中阿尼西亚期。为了揭示层状燧石的沉积相和微观结构，对通过该剖面收集的经hf处理的燧石板进行了高分辨率扫描电镜观察。识别出3种微相：普通远洋燧石相（G2）、远洋硅质粘土相（E1/E2）和含丰富海绵针状体和放射虫壳的生物硅质组分相（G1）。相G2具有较高的生物硅成分（10-30%），主要表现为溶解和/或保存较差的微化石。E1/E2相为硅质粘土基质，生物硅质贝壳和针状物含量低（1-10%）。G1相的特征是密集排列、非胶结的海绵针状体和球形放射虫壳。

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.