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Forearc response to subduction of the Cocos Ridge, Panama-Costa Rica

Jeff Corrigan, Paul Mann and James C. Ingle
Forearc response to subduction of the Cocos Ridge, Panama-Costa Rica
Geological Society of America Bulletin (May 1990) 102 (5): 628-652


Stratigraphic, paleontologic, and structural data from two Panama-Costa Rica forearc peninsulas located landward of the aseismic Cocos Ridge along the southernmost Middle America Trench document rapid Pliocene subsidence and basin infilling followed by Quaternary deformation and uplift. On the Burica Peninsula, an approximately 3,000-m-thick, Pliocene-Pleistocene clastic sedimentary sequence, characterized by fine-grained turbidite deposits and volumetrically minor coarser-grained channel-fill, slump, and debris-flow deposits, bears depth-diagnostic foraminifera that document rapid Pliocene subsidence and deposition on a south-dipping paleoslope. New paleobathymetric and age estimates from foraminifera in these rocks indicate shallowing of depositional paleodepths from 2,000+ to 1,200 m during the late Pliocene. Present-day exposure of these rocks indicates an average Quaternary uplift rate of approximately 1 mm/yr. The turbidite section on the Burica Peninsula is interpreted to represent a trench-slope deposit and is correlated to a similar, marine sedimentary section on the adjacent Osa Peninsula of Costa Rica.Structures developed within Pliocene-Pleistocene strata of the outer-forearc Burica and Osa Peninsulas record minor (<5%) subhorizontal, margin-perpendicular shortening and margin-perpendicular extension. Bedding orientations on the Osa and Burica Peninsulas generally record arcward tilting by 10 degrees -30 degrees of these outer-forearc blocks. On the Burica Peninsula, the Medial fault zone, a north-striking, high-angle, right-lateral strike-slip (?) fault, has truncated and reoriented the Pliocene-Pleistocene sedimentary sequence by fault-bend (forced) folding. A linear, margin-parallel fault, herein named the "Ballena-Celmira fault zone," bounds the arcward side of the Osa and Burica Peninsulas and has accommodated vertical displacements between the outer forearc (Burica-Osa area) and inner forearc (Terraba area) throughout the Tertiary. Structural and seismicity observations from the forearc region suggest that Neogene deformation of the leading edge of the arc in this area reflects the effects of isostatic uplift, and possibly increased interplate shear stresses, as a result of subduction of the Cocos Ridge beneath this part of the arc since 1 m.y. ago.

ISSN: 0016-7606
EISSN: 1943-2674
Serial Title: Geological Society of America Bulletin
Serial Volume: 102
Serial Issue: 5
Title: Forearc response to subduction of the Cocos Ridge, Panama-Costa Rica
Affiliation: Univ. Tex. at Austin, Dep. Geol. Sci., Austin, TX, United States
Pages: 628-652
Published: 199005
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 70
Accession Number: 1990-030247
Categories: StratigraphySolid-earth geophysicsSedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Univ. Tex., Inst. Geophys., Contrib. No. 734
Illustration Description: illus. incl. 2 tables, sects., strat. cols., geol. sketch maps
N07°10'00" - N09°40'00", W83°01'60" - W77°10'00"
N08°00'00" - N11°15'00", W86°00'00" - W82°30'00"
N00°00'00" - N09°00'00", W92°30'00" - W83°00'00"
Secondary Affiliation: Stanford Univ., USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 1990
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