Evidence for two fossil spreading ridges in the southeast Pacific

Research Article| May 01, 1980 Evidence for two fossil spreading ridges in the southeast Pacific J. MAMMERICKX; J. MAMMERICKX 1Scripps Institution of Oceanography, La Jolla, California 92093 Search for other works by this author on: GSW Google Scholar E. HERRON; E. HERRON 2Lamont-Doherty Geological Observatory of Columbia University, Palisades, New York 10964 Search for other works by this author on: GSW Google Scholar L. DORMAN L. DORMAN 3Scripps Institution of Oceanography, La Jolla, California 92093 Search for other works by this author on: GSW Google Scholar Author and Article Information J. MAMMERICKX 1Scripps Institution of Oceanography, La Jolla, California 92093 E. HERRON 2Lamont-Doherty Geological Observatory of Columbia University, Palisades, New York 10964 L. DORMAN 3Scripps Institution of Oceanography, La Jolla, California 92093 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1980) 91 (5): 263–271. https://doi.org/10.1130/0016-7606(1980)91<263:EFTFSR>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation J. MAMMERICKX, E. HERRON, L. DORMAN; Evidence for two fossil spreading ridges in the southeast Pacific. GSA Bulletin 1980;; 91 (5): 263–271. doi: https://doi.org/10.1130/0016-7606(1980)91<263:EFTFSR>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Two different sets of extinct spreading ridge segments (Pacific-Farallon and Pacific-Nazca) are identified from bathymetric and magnetic data in the southeast Pacific. The older set is composed of several topographically subdued segments of a fossil ridge (Pacific-Farallon) that trends northwest, parallel to and about 175 to 550 km distant from the younger side of anomaly 7 (26 m.y. B.P.) The younger set trends north-northeast subparallel to the present East Pacific Rise (EPR), at an angle of about 45° to the older fossil ridge. The younger ridge forms the Galapagos Rise and includes a set of west-northwest–trending fracture zones. This was the original site of the EPR before it jumped westward to its present position. Oligocene magnetic anomalies (7–12) were generated at the older northwest-trending ridge rather than from the younger northeast-trending Galapagos Rise. The change in ridge orientation from the older Pacific-Farallon to the younger Pacific-Nazca direction is likely to be associated with the birth of the Cocos-Nacza spreading ridge system, about 20 to 25 m.y. ago. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.