Sedimentación y paleogeografía del Cretacico y Cenozoico del Litoral Pacifico de Costa Rica
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Peter O. Baumgartner [1] ; Claudia R. Mora [1] ; Jacques Butterlin [2] ; J. Sigal [2] ; Georgette Glacon [2] ; Jacques Azéma [2] ; Jacques Bourgois [2]
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[1] Universidad de Costa Rica
Universidad de Costa Rica
Hospital, Costa Rica
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[2] Pierre and Marie Curie University
Pierre and Marie Curie University
París, Francia
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- Localización: Revista geológica de América Central, ISSN 0256-7024, Nº. 1, 1984, págs. 57-136
- Idioma: español
- Enlaces
- Dialnet Métricas: 3 Citas
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Resumen
- español
En base a criterios genéticos se reorganiza la estratigrafía sistemática del litoral pacífico en tres supergrupos: l . Papagayo: basamentos básicos y ultrabasicos oceánicos. 2. Garza: cobertura sedimentaria oceánica. 3. Mal País: cobertura sedimentaria nerítica, subdividida en 5 épocas. Se describen 6 nuevas forma ciones.
La historia geológica queda subdividida en dos fases: l. El Complejo de Nicoya (Batoniano/Calloviano-Santoniano) y la Peridotita de Santa Elena constituyen un edificio de mantos de corrimiento del Santoniano superior con vergencia de nor- te a sur. 2. Desde el Campaniano esta estructura forma parte de la corteza estable ístmica, afectada únicamente por plegamiento abierto y fallamiento normal . No se han observado estructuras de acreción relacionadas con la fosa mesoamericana, establecida desde el Senoniano terminal.
Aparte de las calizas con rudístides del Senoniano superior (Epoca 1), la sedimentación pelágica desde el Campaniano al Eoceno medio obedeció a cambios paleo ceanográficos conocidos del Pacffico, ocasionando los depósitos silíceos del Santo niano-Campaniano y del Paleoceno superior-Eoceno medio. Las potentes secuencias turbidíticas del Maestrichtiano-Paleoceno documentan la erosión de un arco volcánico andesítico emergido, producto de la subducción activa, rodeado de plataformas someras silicoclásticas y carbonatadas (Epoca 2).
Un evento tectónico en el límite Eoceno medio/superior causó desprendimien~ tos y deformación por gravedad en el techo de la secuencia oceánica, levantamíen to drástico y un nuevo establecimiento en grandes áreas de depositación nerítica carbonatada (Epoca 3) discordante, mientras que la sedimentación turbidítica per sistió (Santa Elena. Quepos). - Sedimentos neríticos someros se depositaron discordantemente en el sector central durante el Oligoceno- Mioceno inferior (Epoca 4) y durante el Mioceno superior- Pleistoceno (Epoca 5) , mientras que secuencias turbidíticas potentes se acumularon en el sur (Oligoceno-Mioceno: Fila Costeña, Plioceno: Osa, Burica).
- English
The systematic stratigraphy of the Pacific littoral of Costa Rica has been reorganized in three supergroups: l. Papagayo: mafic and ultramafic oceanic basements and volcanically or tectonically associated sediments . 2. Garza:
oceanic sedimentary cover including pelagics (Sabana Grande Group) and slope deposits (Sámara Group). 3. Mal País: neritic sedimentary cover, subdivided into 5 epochs.
A majar, upper Santonian tectonic event divides the geologic history into two phases: l. The Nicoya Complex with its Bathonian/Callovian - Santonian (BAUMGARTNER 1984) oceanic sedimentary cover and the Santa Elena Peridotite form together a nappe edifice with a southern vergence (BOURGOIS ··-et al. in press). 2. Since the Campanian, this structure is part of the stable isthmic crust, the substrate of the studied upper Senonian-Cenozoic sedimentary sequen ces, affected by open folding and normal faulting only. No accretionary struc tures related to subduction along the Middle-American Trench, effective since that latest Senonian, have been observed. Ocean floor continued to form during the latest Senonian-early Paleocene in a primitive island are environment (Quepos, Osa) .
Campanian-middle Eocene pelagic (and background) sedímentation followed the paleooceanographic trends observed in the Pacific, amplified by local (equatorial, eastern ocean margin) hígh fertílity . A shallow CCD is reflected by Santonian-lower Campanian and upper Paleocen-middle Eocene radiolarian-rich siliceous deposits. In the late Campanian-Maestrichtian a drastic drop of the CCD overruled subsidence and resulted in deposition of foraminifer-rich pelagic limestones. Thick Maestrichtian-Paleocene turbidite and mass flow sequences were deposited in NW-SE trending elongate basins and document the erosion of an emerged andesitic volcanic are. the product of active subduction, surrounded by narrow carbonate and siliciciastic shelves, set above steep, unstable slopes.
A tectonic event at the middle/late Eocene boundary caused mayor gravitatíve sliding and slumping of the upper part of the oceanic sequence, subsequent uplift and a regional , unconformable onset of shallow carbonate deposition, while turbiditc sedimentation persisted in sorne areas (Santa Elena, Quepas).
An interred thickened oceanic crust in isostatic equilibrium should form a sea floor at subphotic depths. However . tectonic uplift has repeatdly brought the subst rate to shallow depth and allowed the deposition of unconformable, thin, shortlived, neritic sequences, formed during five succesive epochs:
Epoch l. Campanian-Maestrichtian: The s tructurally highest parts of the upper Santonian orogen were uplifted to subaérial and shallow photic depths where rudis tid limestones developed .
Epoch 2. Paleocene- early Eocene : Volcanic activity related to subduction gave rise to an island are surrounded by shallow platforms NE of the study area, only known from reworked carbonate clasts in s l ope deposits (Sámara, Quepas).
Epoch 3. Middle-late Eocene : Tectonic uplift brought most of the area to shallow photic depth which led to the formation of the widespread larger foraminifer - red algal limestones.
Epoch 4. Oli gocene- ear ly Mioceoe: Most of the central area was emerged and ooly near the trench (Nosara-Mal País) thin shallow c l astic sequences devel oped , while turbidite basins persisted i n the NW and SE (Dept. Rivas , Nicaragua , Fila Costeña) .
Epoch S. Late Miocene- Pleistocene: Littoral deposits are concentrated a r ound the south of Nicoya , in areas of recent uplift (FISCHER 1980).
- español
