Back to Caribbean Plate Tectonics Meetings and Field Trips for IGCP-433.

Conveners: Dr. Percy Denyer and Dr. Peter Baumgartner (Escuela Centroamericana de Geología)

Contact person: P. Denyer   pdenyer@geologia.ucr.ac.cr
Escuela Centroamericana de Geología de Costa Rica.
Apdo. 214-2060 UCR
San José, Costa Rica
Tel. (506) 2257941/2075625
Fax. (506) 2342347

Dear colleagues
We are kindly inviting all members of IGCP Project 433 to join us in a field meeting about the Central American Arc and its crustal structure. IGCP Project 433 will cover the terrestrial transportation expenses, and will provide a small support to some participants upon request and possibilities depending of the amount allocated next year to our project by IUGS-UNESCO. According to our Costa Rican colleagues, you will spend about 220 dollars during the field workshop, if you use the hotels they have arranged for us and control your meals. Number of participants is restricted to 20, so we need to know you willingness to attend this meeting the sooner the better to arrange hotels and transportation. Your hotel reservation in San José is your responsability, but Dr. P. Denyer can advise of the less expensive. Hotels during the field trip will be reserved by the conveners, with double occupancy.

Please contact (iturralde@mnhnc.inf.cu) and (egl+@pitt.edu) if you need some support to attend the meeting.

General Schedule:

March 1st. Scientific meeting. Presentations only about the Geology and Plate Tectonics of Central America. If you wish to participate with an oral or poster presentation, please sent the title and abstract to Dr. Denyer (pdenyer@geologia.ucr.ac.cr).

March 2-7. Field trip. Visit to the Nicoya complex and related units.

Dr. Manuel Iturralde Vinent and Dr. Edward Lidiak (Project leaders)

The Nicoya Peninsula has been studied since the sixties, because of its outcrops of oceanic crust and its importance for the understanding of the origin and geotectonic history of the Middle American convergent margin. It consists of a Jurassic-Paleogene basaltic ophiolitic sequence, mainly composed of basalts that occur as massive and pillow flows, dykes, and hyaloclastic breccias. Subordinated rocks include komatiites, alkali-olivine basalts, gabbros, ferrogabbros, diabases, picrites and plagiogranites. The age of the igneous sequence corresponds to the Upper Cretaceous sill event.

Deep sea radiolarian cherts were deposited from the Middle Jurassic to Late Cretaceous. No Jurassic oceanic basement has been identified so far at the outcrop level in the Nicoya Peninsula, but could be buried beneath the surface. The Jurassic-Cretaceous chert sediment pile became disrupted and detached from its original basement by multiple intrusions during the formation of the Caribbean Plateau.

Hemipelagic and pelagic rocks, rich in epiclastic elements (shards, pumice, plagioclases and amphiboles) are circumstantial evidence of an paleo-magmatic arc of Albian to Late Santonian age.

In the Santa Elena peninsula, crops out a peridotitic nappe composed by diopside-bearing harzburgites and lherzolites, scarce plagioclase peridotites, dunites and orthopyroxenites. This nappe is cut by dykes of diabases, ultramafic cumulates, clinopyroxenites and pegmatitic gabbros. The relatively autochthonous series consists of radiolarites, cherts and basaltic breccias.

The Nicoya peninsula consists of different terranes, the Nicoya terrane accreted to the edge of the Caribbean plate during Cretaceous to Late Eocene, and now is cropping out of the outer part of the peninsula of Nicoya and the Santa Elena peninsula. The Chorotega terrane constitute the inner part of the Nicoya Gulf. The Osa-Caño Accretionary Complex comprises an accretionary mélange formed during Paleogene and it is part of the Golfito terrane. The Herradura Block is constituted by basalts associated to the Oceanic Caribbean Plateau and E-morb basalts (Maastrichtian- Early Eocene)

• Santa Elena nappe
• Radiolarites sequence of Nicoya peninsula
• Igneous assemblage of Nicoya Complex
• Tortugal Komatiites
• Ocotal plagiogranites
• Fossiliferous manganese nodules
• Potrero gabbros and dolerites
• Sedimentary overlying sequence (Cretaceous-Paleogene)
• Pelagic and hemipelagic epiclastic Cretaceous sediments
• Accretionary mélange at Caño island- Osa peninsula

This page last modified October 28, 2003