Abstract The enigmatic 85°E Ridge crosses the Bay of Bengal from north to south. Its strong gravity anomaly low is associated with Cretaceous hotspot volcanism. South of 5°N, the gravity low bends into a SW-NE orientation and continues as far SW as the Afanasy Nikitin Seamounts. This change has been interpreted to represent a bent hotspot track. We report new constraints on the crustal structure and genesis beneath the SW-trending gravity low based on new refraction seismic, reflection seismic, and shipborne gravity data. Our findings show that the crustal structure across the gravity low does not differ significantly from the adjacent, 4.5 to 7 km thick oceanic crust. No basement ridge, significant crustal thickening, or magmatic underplating were identified. We found no evidence for a southern prolongation of the 85°E Ridge. Instead, our P-wave velocity and density models reveal the gravity low to express a flexural basin, which is a result of widespread mid-Miocene to recent lithospheric deformation in the Indian Ocean. The ~25 mGal negative gravity anomaly is therefore not related to the passage of the Indian plate over a mantle plume, casting doubt on the possibility that volcanism at the Afanasy Nikitin Seamounts might be related to the same plume as the northern 85°E Ridge. The northern 85°E Ridge may have been generated at the northern prolongation of the 86°E Fracture Zone.

中文翻译：

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5°N 以南 85°E 海脊的弯曲延伸——事实还是虚构？

摘要 神秘的 85°E 海脊自北向南横穿孟加拉湾。其强烈的重力异常低与白垩纪热点火山活动有关。在 5°N 以南，重力低洼弯曲成 SW-NE 方向，并继续向西南延伸至 Afanasy Nikitin 海山。此更改已被解释为表示弯曲的热点轨道。基于新的折射地震、反射地震和船载重力数据，我们报告了对西南向重力低下地壳结构和成因的新限制。我们的研究结果表明，重力低点的地壳结构与相邻的 4.5 至 7 公里厚的大洋地壳没有显着差异。未发现基底脊、显着的地壳增厚或岩浆底侵作用。我们没有发现 85°E 海脊向南延伸的证据。反而，我们的 P 波速度和密度模型揭示了重力低以表示弯曲盆地，这是印度洋中中新世到最近岩石圈广泛变形的结果。因此，~25 mGal 负重力异常与印度板块通过地幔柱无关，这让人怀疑 Afanasy Nikitin Seamounts 的火山活动可能与 85°E 海脊北部的同一柱状体有关。北 85°E 海脊可能产生于 86°E 断裂带的北部延伸部分。怀疑 Afanasy Nikitin 海山的火山活动可能与 85°E 海脊北部的同一羽流有关。北 85°E 海脊可能产生于 86°E 断裂带的北部延伸部分。怀疑 Afanasy Nikitin 海山的火山活动可能与 85°E 海脊北部的同一羽流有关。北 85°E 海脊可能产生于 86°E 断裂带的北部延伸部分。