ZusammenfassungDer mehrere Kilometer m~ichtige, im wesentlichen aus ozeanischen Basalten aufgebaute Komplex von Nicoya, der den Sockel der zahlreichen pazifischen Halbinseln von Costa tlica und Panama bildet, wird biostratigraphiseh zum ersten Mal in sechs, altersm~Big sehr verschiedene Teilkomplexe (Subkomplexe) AbstractThe Nicoya Complex, built by thick sequences of mainly oceanic basalts and exposed on the numerous pacific peninsulas of Costa Rica and Panama (Fig. 1), is, for the first time, divided by means of biostratigraphic and facies methods. This classification is not only possible by means of biostratigraphic dating of the overlying sediments but also of occasional inclusions of sedimentary silicious and calcareous exotic blocks within the basaltic sequences. This method shows that the formation of the Nicoya Complex, contrary to the hitherto idea of a uniphase and short development, not only took up very long periods of geological time but was also very discontinuously built. The Nicoya Complex can now be divided into six subeomplexes of different age which, in part, may already be regionally differentiated (Fig. 88). These subeomplexes have to be interpreted as being submarine, abyssal to bathyal sheet flows of mainly tholeiitic basalts up to several hundred meters in thickness. During these effusions of short time duration, the sedimentary cover, in the meantime deposited on the underlying effusiva, was more or less intensively reworked by these processes and deported within the new effusion body

The Campanian rudist fauna identified from the localities Playa Panamá, Santa Rosa National Park, Colorado de Abangares, and Bolsón in Guanacaste Province, Costa Rica, is composed of the antillocaprinidsAntillocaprinasp. aff.A. suboccidentalisChubb, 1967,Antillocaprinasp. and Antillocaprinidae indet.; the multiple-fold hippuritidsBarrettia moniliferaWoodward, 1862,Parastroma trechmanniChubb, 1967, and cf.Whitfieldiella gigas(Chubb, 1955); the plagioptychidsPlagioptychus trechmanniChubb, 1956,Plagioptychussp. cf.P. zansiChubb, 1956,Mitrocaprina costaricaensisnew species,Mitrocaprina multicanaliculataChubb, 1956, and Plagioptychidae indet.; and the radiolitidsRadiolitessp. aff.R. multicostata(Adkins, 1930),Alencasteritesnew genusmooretownensis(Trechmann, 1924),Bournonia?tetrahedron(Chubb, 1967),Chiapasellasp.,Guanacastea costaricaensisnew genus new species, cf.Potositessp. aff.P. tristantorresiAlencáster and Pons in Pons et al., 2010, and aff.Thyrastylonsp. Although some differences in rudist diversity and sedimentary setting were observed among localities, most species indicate the same age for all occurrences, which correspond to the Campanian, probably mid-Campanian. Radiolitid specimens appear better preserved than those of other taxa and are thus discussed more in detail. Both the number of radiolitid genera exclusively known from the New World, and reasonable doubts about the correct attribution of some New World species to Old World genera, indicate important differences between rudist faunas at both sides of the Atlantic (Mediterranean and American Tethys, respectively) during the Late Cretaceous.

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