Analysis of the Tortonian sediments in the northeast Indian Ocean from NGHP–01–17A drilled at Andaman Basin shows 22 silicoflagellate taxa belonging to the genera Bachmannocena, Dictyocha, Distephanopsis, Paramesocena and Stephanocha. This study records the first evidence of Tortonian silicoflagellates from the offshore of northeast Indian Ocean. Two Partial Range zones namely Dictyocha varia, and Dictyocha extensa and one Subzone i.e. Bachmannocena elliptica have been proposed. In the present study, it has been observed that the transition of D. varia to D. extensa took place within the Tortonian. Fossil records of double skeletons in the silicoflagellate taxa are rare; however, we have documented double skeletons in three silicoflagellate taxa i.e. Dictyocha calida, Dictyocha fibula subspecies ausonia and Stephanocha speculum (6-sided). Ratio of Dictyocha and Stephanocha based on the combined abundance of all the taxa of the two genera reveals that there was substantial dominance of Dictyocha over Stephanocha throughout the studied sequence. The Dictyocha/Stephanocha palaeotemprature proxy indicated prevalence of warmer climate during the Tortonian (9.86 Ma to 7.39 Ma) with a cooling minimum in the Bachmannocena elliptica Subzone during 8.104 Ma – 8.088 Ma corresponding with nutrient rich condition.

在安达曼盆地钻探的 NGHP-01-17A 对印度洋东北部托尔通沉积物的分析表明，有 22 个硅鞭毛虫类群属于Bachmannocena、Dictyocha、Distephanopsis、Paramesocena和Stephanocha属。这项研究记录了东北印度洋近海托尔通硅鞭毛虫的第一个证据。已经提出了两个部分范围区域，即Dictyocha varia和Dictyocha extensa以及一个亚区域，即Bachmannocena elliptica 。在本研究中，观察到D. varia向D. extensa的转变发生在 Tortonian 内。硅鞭毛虫分类群中双骨架的化石记录很少见；然而，我们已经记录了三个硅鞭毛虫类群的双骨架，即Dictyocha calida、Dictyocha fibula亚种ausonia和Stephanocha speculum（6 面）。Dictyocha和Stephanocha的比率基于两个属的所有分类单元的组合丰度，表明在整个研究序列中Dictyocha对Stephanocha具有显着优势。Dictyocha /斯蒂芬诺查古温度代表表明在 Tortonian（9.86 Ma 至 7.39 Ma）期间普遍存在较暖的气候，而Bachmannocena elliptica亚区在 8.104 Ma - 8.088 Ma 期间的最低降温与营养丰富的条件相对应。