Ks. Krishna et Dg. Rao, Abandoned Paleocene spreading center in the northeastern Indian Ocean: evidence from magnetic and seismic reflection data, MARINE GEOL, 162(2-4), 2000, pp. 215-224
Magnetic data from the northeastern Indian Ocean reveal east-west trending
magnetic lineations 28 through 34, an abandoned spreading center (ASC) and
part of the Cretaceous Magnetic Quiet Zone (CMQZ), which are used to recons
truct past tectonic processes involved in the evolution of the ocean. Offse
ts in the magnetic lineations outline the existence of four N-S trending fr
acture zones: 80 degrees E, Indira, 84.5 degrees E, and 86 degrees E. The 8
4.5 degrees E Fracture Zone (FZ) acts as a boundary separating oceanic crus
t with different magnetic isochron patterns. The pairs of magnetic lineatio
ns 30 through 32n.2 between the 86 degrees E FZ and the Ninetyeast Ridge re
veal an ASC of about 65 Ma age, parallel to approximate to 0.5 degrees S la
titude. The structure of the ASC is well-identified in seismic reflection d
ata as an undulating basement topographic rise covered by up to 2 km of Ben
gal Fan sediments. The spreading center might have initiated its activity a
long with other spreading centers of the Wharton Ridge and India-Antarctica
Ridge, after the first major plate reorganization of the Indian Ocean (abo
ut 95 +/- 5 Ma), but ceased shortly after formation of anomaly 30 (about 65
Ma). Then it jumped southward between anomalies 32n.2 and 33. The jump cap
tured the oceanic crust of anomalies 30 through 32n.2 that initially formed
on the Antarctica plate, but were later transferred to the Indian plate. T
he spreading centers in the vicinity of the Ninetyeast Ridge jumped several
times southward, to maintain a close proximity to the Kerguelen hotspot. (
C) 2000 Elsevier Science B.V. All rights reserved.