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This study details the Late Cretaceous and Tertiary northward movement of the Indian plate. Breaks in India's northward movement rate are identified, dated, and correlated with the evolution of the India-Asia convergence. Paleolatitudinal constraints on the origin of Ninetyeast Ridge are discussed, and limited magnetostratigraphic detail is provided.Nearly 1500 sediment and basement samples from Sites 756, 757, and 758 on Ninetyeast Ridge were studied through detailed alternating field and thermal demagnetization. Primary and various secondary magnetization components were identified. Breakpoint intervals in the primary paleolatitude pattern for common-Site 758 were identified at 2. 7, 6.7,18.5, about 53, 63.5-67, and 68-74.5 Ma. Only the breakpoint interval at about 53 Ma reliably reflects a reduction in India's northward movement rate. The onset of this probably gradual slowdown was dated at 55 Ma (minimal age) based on the intersection of weighted linear regression lines. At the location of common-Site 758, northward movement slowed from 18-19.5 cm/yr (from at least 65 to 55 Ma) to 4.5 cm/yr (from 55 to at least 20 Ma). Reanalysis of earlier DSDP/ODP paleolatitude data from the Indian plate gives a comparable date (53 Ma) for this reduction in northward velocity.Comparison of our Ninetyeast Ridge data and Himalayan paleomagnetic data indicates that the initial contact of Greater India and Asia may have already been established by Cretaceous/Tertiary boundary time. The geological record of the convergence zone and the Indian plate supports the notion that the Deccan Traps extrusion may have resulted from the ensuing deformation of the Indian plate. We interpret the breakpoint at 55+ Ma to reflect completion of the eastward progressive India-Asia suturing process.Neogene phases in the evolution of the convergence zone were correlated with significant changes in the susceptibility, NRM intensity, and lithostratigraphic profile of Site 758. These changes are interpreted to reflect and postdate tectonic phases in the evolution of the wider Himalayan and southern Tibetan region. The changes were dated and interpreted as follows: 17.5 Ma, initial uplift of the Higher Himalaya following initiation of intercontinental underthrusting; 10-10.4 Ma, increased uplift and onset of Middle Siwaliks sedimentation; 8.8 Ma, probable reduction in influx corresponding with the Nagri Formation to Dhok Pathan Formation changeover; 6.5 Ma, major tectonic phase evident throughout the wider Himalayan region and northern Indian Ocean; 5.1-5.4 Ma, onset of oroclinal bending of the Himalayan Arc, of extensional tectonism in southern Tibet, and of Upper Siwalik sedimentation; 2.5-2.7 and 1.9 Ma, major phases of uplift of the Himalayan and Tibetan region culminating in the present-day high relief.The basal ash sequence and upper flow sequence of Site 758 and the basal ash sequence of Site 757 indicate paleolatitudes at about 50°S. These support a Kerguelen hot spot origin for Ninetyeast Ridge. Consistently aberrant inclinations in the basa...

We have carried out a magnetic fabric study on deformed, clay-rich rocks from the Carboniferous Texas beds and Coifs Harbour Association in order to test the hypothesis of oroclinal bending of the Texas and Coifs Harbour blocks of the southern New England Orogen, eastern Australia. The magnetic susceptibility is dominated by paramagnetic phyllosilicates, with site-dependent contributions from the ferromagnetic minerals pyrrhotite, magnetite and hematite. Pyrrhotite is ubiquitous in the Texas block and in the central part of the Coifs Harbour block, and may be important as an indicator of the grade of lowtemperature metamorphism. The magnetic fabric results, in general, show good agreement with structural observations in the Texas and Coifs Harbour blocks. The magnetic foliation is related to the pervasive cleavage associated with accretionary deformation prior to oroclinal bending. The magnitudes of the anisotropy parameters and the plunge of the magnetic lineation indicate an increase in the intensity of deformation from east of the Coifs Harbour orocline towards the Texas orocline. An imprint from oroclinal deformation is suggested by a significant increase in the anisotropy parameter and by the development of steeply plunging magnetic lineations towards the hinges of the Texas and Coifs Harbour oroclines. The Terrica beds from the Early Permian (Allandale) Terrica inlier in the Texas orocline also show another, pre-tilt induced, tectonic imprint. Remanence data from volcanics in the Alum Rock inlier (293 Ma) and magnetic fabric data from this inlier tentatively constrain the onset of oroclinal bending as prior to extrusion of the Alum Rocks, and the completion of bending as post-Terrica beds deposition and pre-Illawarra Reversal (est. 265 Ma). et al. 2000). Such a complication has been described by Robion et al. (1995) who showed that an early structural magnetic lineation can From: