Revised tectonic boundaries in the Cocos Plate off Costa Rica: Implications for the segmentation of the convergent margin and for plate tectonic models
U. Barckhausen et al., Revised tectonic boundaries in the Cocos Plate off Costa Rica: Implications for the segmentation of the convergent margin and for plate tectonic models, J GEO R-SOL, 106(B9), 2001, pp. 19207-19220
The oceanic Cocos Plate subducting beneath Costa Rica has a complex plate t
ectonic history resulting in segmentation. New lines of magnetic data clear
ly define tectonic boundaries which separate lithosphere formed at the East
Pacific Rise from lithosphere formed at the Cocos-Nazca spreading center.
They also define two early phase Cocos-Nazca spreading regimes and a major
propagator. In addition to these sharply defined tectonic boundaries are ov
erprinted boundaries from volcanism during passage of Cocos Plate over the
Galapagos hot spot. The subducted segment boundaries correspond with distin
ct changes in upper plate tectonic structure and features of the subducted
slab. Newly identified seafloor-spreading anomalies show oceanic lithospher
e formed during initial breakup of the Farallon Plate at 22.7 Ma and openin
g of the Cocos-Nazca spreading center. A revised regional compilation of ma
gnetic anomalies allows refinement of plate tectonic models for the early h
istory of the Cocos-Nazca spreading center. At 19.5 Ma a major ridge jump r
eshaped its geometry, and after similar to 14.5 Ma multiple southward ridge
jumps led to a highly asymmetric accretion of lithosphere. A suspected cau
se of ridge jumps is an interaction of the Cocos-Nazca spreading center wit
h the Galapagos hot spot.