18. Mesozoic Sea-Floor Spreading in the North Pacific

  1. George H. Sutton,
  2. Murli H. Manghnani,
  3. Ralph Moberly and
  4. Ethel U. Mcafee
  1. Thomas W. C. Hilde1,
  2. Nobuhiro Isezaki2 and
  3. John M. Wageman3

Published Online: 17 MAR 2013

DOI: 10.1029/GM019p0205

The Geophysics of the Pacific Ocean Basin and Its Margin

The Geophysics of the Pacific Ocean Basin and Its Margin

How to Cite

Hilde, T. W. C., Isezaki, N. and Wageman, J. M. (1976) Mesozoic Sea-Floor Spreading in the North Pacific, in The Geophysics of the Pacific Ocean Basin and Its Margin (eds G. H. Sutton, M. H. Manghnani, R. Moberly and E. U. Mcafee), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM019p0205

Author Information

  1. 1

    Committee for Co-Ordination of Joint Prospecting for Mineral Resources in Asian Offshore Areas (Ccop), United Nations, Bangkok, Thailand

  2. 2

    Meteorological College, Kashiwa 277, Japan

  3. 3

    Gulf Research and Development Company, Pittsburgh, Pennsylvania 15230

Publication History

  1. Published Online: 17 MAR 2013
  2. Published Print: 1 JAN 1976

ISBN Information

Print ISBN: 9780875900193

Online ISBN: 9781118663592

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Keywords:

  • Geophysics—Pacific area—Congresses;
  • Woollard, George Prior, 1908

Summary

Sea-floor spreading magnetic anomalies of Mesozoic age have been mapped for the entire northwest Pacific, from the mid-Mesozoic quiet zone to the Cretaceous quiet zone. There are two general lineation directions: NE-SW between Shatsky rise and Japan, and NW-SE to the east and southeast of Shatsky rise. These two patterns are joined in a magnetic bight southwest of Shatsky rise. The bight is assumed to have been produced by spreading from ridges of a former ridge-ridge-ridge (R-R-R) triple junction between the Pacific, Kula, and Farallon plates which existed at the beginning of the late Mesozoic geomagnetic reversal period (anomaly M-26, 155 m.y.B.P.). Evolution of the triple junction resulted in the formation of Shatsky rise during 142 to 116 m.y.B.P. and Hess rise during 116 to 95 m.y.B.P. Identification of the anomalies is based on a late Mesozoic reversal model constructed from four closely spaced, parallel profiles recorded across the complete late Mesozoic sequence of reversal anomalies near the Hawaiian ridge. Anomalies which are repeated in all four profiles are considered due to reversals, while those not repeated are shown to be associated with seamounts or other topographic features. It is concluded that at 155 m.y.B.P. (M-26) the Kula-Pacific, Pacific-Farallon, Pacific-Phoenix ridge system described a comparatively small triangle about the Pacific plate. Assuming that spreading existed at the same rates prior to the period of late Mesozoic reversals, and projecting it back in time, the system would have started essentially at a point in the vicinity of 15°N and 155°E at 185 to 190 ill.y.B.P. Spreading was faster on the Kula-Pacific and the Pacific-Phoenix ridges than on the Pacific-Farallon ridge during the late Mesozoic. Spreading direction of the Kula-Pacific and northern Pacific-Farallon ridges changed clockwise with time (40° from M-26 to Cenozoic anomaly 32), while spreading direction changed counterclockwise on the Pacific-Phoenix ridge. This evolution of the spreading system has persisted to the present time; thus, the Pacific plate has apparently formed from a small cell by the unfolding of the spreading ridges bordering it.