|Ocean:||Pacific, Panama Basin|
|Spreading center type:||Back-arc basin spreading ridge|
|Time of cessation:||Ca. 9 Ma, after chron C5n (Lonsdale, 2005)|
|Subsequent active spreading center:||Present-day Cocos-Nazca plate boundary|
|Cessation style:||Spreading rate gradually decreased to a half of its former rate over a period of 3 m.y. (Lonsdale and Klitgord, 1978)|
|Later deformation or volcanism:||None evident|
The Malpelo extinct ridge is a well-studied extinct ridge in the Panama Basin, located offshore of Colombia. The extinct spreading axis was described in detail by Lonsdale and Klitgord (1978) and is well-constrained by identified magnetic anomalies either side of the inferred axial segments and prominent troughs at extinct segments. Seafloor spreading at the Malpelo rift was noted to have been at an oblique angle to the contemporaneous spreading on the Costa Rica rift, a segment of the Cocos-Nazca spreading center, west of 83 W (Lonsdale and Klitgord, 1978).
Lonsdale and Klitgord (1978) propose that a plate boundary reorganization led to capture of the Malpelo rift formed crust onto the Nazca plate. They note that the spreading rates of the Malpelo and (the simultaneously spreading) Costa Rica rifts were very different and that this may have led to the development of an active transform boundary to the east (Lonsdale and Klitgord, 1978). It is also noted that the formerly active subduction system in the south of the Panama Basin may have ceased at around the same time as the ridge extinction and that regional removal of the slab pull force may have been important in ridge cessation (Lonsdale and Klitgord, 1978).
A later study suggested that an earlier ridge extinction occurred at the Buenaventura ridge (Hardy, 1991) (situated to the north east of the Malpelo Rift), due to locking of the subduction zone as a 'scarp' of oceanic crust was introduced to the trench at 12 Ma. The authors propose that this contributed to the demise of the Malpelo Rift spreading center.
Hardy, N. C., 1991, Tectonic evolution of the easternmost Panama Basin, Journal of South American Earth Sciences, v. 4, no. 3, p. 261-269.
Lonsdale, P. and Klitgord, K.D., 1978, Structure and tectonic history of the eastern Panama Basin, Bulletin of the Geological Society of America, v. 89, p. 981– 999.