Marine Geophysical Researches

, Volume 4, Issue 2, pp 153-166

First online:

Fossil spreading center and faults within the Panama Fracture Zone

  • Allen LowrieAffiliated withSea Floor Division, Naval Ocean Research and Development Activity, NSTL Station
  • , Thomas AitkenAffiliated withLamont-Doherty Geological Observatory
  • , Paul GrimAffiliated withGeothermal Group, Data Services Division, National Geophysical and Solar-Terrestrial Data Center, NOAA
  • , Linda McRaneyAffiliated withSea Floor Division, Naval Ocean Research and Development Activity, NSTL Station

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The north/south-trending Panama Fracture Zone forms the present eastern boundary of the Cocos Plate, with the interplate motion being right-lateral strike-slip. This fracture zone is composed of at least four linear troughs some hundreds of kilometers in length. Separate active or historic faults undoubtedly coincide with each trough. The greatest sediment fill is found in the easternmost trough. Surface and basement depths of the western trough are generally greater than those of the other three; the western trough contains the least sediment, and is most continually linear. Morphology and sediments suggest that the principal locus of strike-slip movement within the fracture zone probably migrated incrementally westward from one fault-trough to another. From north to south, the fracture zone apparently narrows from the continental intersection to approximately 5°30′N, and again widens from about 5°N to at least 3°N. Residual E/W-trending magnetic anomalies are centered between two of the four troughs; sea floor spreading in a north-south direction is interpreted to have occurred between 5°30′N and 7°N from 4.5 m.y. ago to 2 m.y. ago, with the symmetric center roughly coinciding with a rift valley at 6°10′N, 82°30′W.