Publication Date:
2020-05-17
Description:
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.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
,
isiRev
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