Tectonic fabric of the Atlantic and Indian oceans and continental drift

Abstract

The floor of the Indian Ocean is dominated by (1) the seismically active Mid-Oceanic Ridge, (2) scattered linear micro-continents (mostly meridional), and (3) fracture zones (some displace the axis of the Mid-Oceanic Ridge and others parallel the micro-continents). The pattern suggests that movement along the Diamantina Fracture Zone has displaced Australia to the east relative to Broken Ridge. In the Arabian Sea north-northeast trending fracture zones have displaced the axis of the Carlsberg Ridge. The complex tectonic fabric of the Indian Ocean is difficult to explain in terms of a simple pattern of convection currents. The location and origin of the Mid-Oceanic Ridge, of oceanic rises, aseismic ridges and transcurrent fault systems must be accounted for in any hypothesis of continental displacement despite unique or exotic assumptions as to strength, viscosity or composition of the oceanic crust and mantle.

Tectonics of the Indonesian region

“…The great submarine Ninetyeast Ridge trends slightly east of north, approximately along long 90° E., nearly straight for 4,800 km from the north slope of the Indian-Antarctic Midocean Ridge to the Bay of Bengal, where it is buried beneath the thick sediments of the Bengal abyssal fan (Heezen and Tharp, 1965a;Laughton and others, 1970). The ridge is about 200 km wide, and most of it has crestal depths between 1,500 and 3,000 m and stands 2,000-4,000 m above the flanking basin floors (figs.…”

Paleozoic and Precambrian rocks of Alaska and their role in its structural evolution

“…24 Siberia on trend with the Gakkel spreading center (Sykes, 1965), a plate boundary separating America from Eurasia was also drawn along the Verhoyansk Mountains (Heezen and Tharp, 1965 ;Morgan, 1968). These data were summarized and interpreted to suggest a hinge zone in the Laptev Sea (as proposed earlier by Wilson) with tension north of the zone and compression south of the zone.…”

“…The seismically and volcanically active mid-Atlantic ridge extends north from Iceland between Greenland and Spitsbergen (Vogt and others, 1970) and with apparent decreased seismicity (Sykes, 1965) continues across the Eurasia Basin as the Gakkel Ridge (Nansen Cordillera) that lies midway between the Lomonosov Ridge and the continental margin of Eurasia (Heezen and Tharp, 1965;Demenitskaya and Karasik, 1969) (fig. 2).…”

Gondwanaland Dispersal and the Early Formation of the Indian Ocean

“…Sufficient data are not available to test this requirement. Also, the north-south offset of the SWB, south of the Mozambique Ridge or Fracture Zone (see Heezen and Tharp, 1965), argues against significant right-lateral movement unless this offset is Oligocene or younger. The resolution of this question is presently ambiguous.…”

“…Cores from the Agulhas Plateau off South Africa also indicate at least a mid-Cretaceous (Cenomanian) age (Saito in Ewing et al, 1969 p. 239). Site 249 dates the Mozambique ridge (Heezen and Tharp, 1965) which evidently is an Aptian or older fracture zone indicating the past relative motion between Africa and Antarctica. The trend of this feature would be essentially parallel to the spreading direction indicated in Figure 4b.…”