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This paper describes petrographically and genetically, a number of peperites, as examples of spatial and temporal coexistence of magmatism and sedimentation in Costa Rica. The cases are presented in basic igneous complexes (ophiolites), mixtures varying from incomplete (megablocks of radiolarite with diabase in the Nicoya Complex) to complete mixes in various stages of Maastrichtian-Paleocene (Golfito Formation) or Paleocene pelagic limestones with basalts (Quepos Subcomplex or Tulín Formation) to form brechoid and pillowed peperites. Within the Oligo-Miocene arc, there are examples extended along the Talamanca range and its foothills, as well as Sarapiquí's plains represented for brechoid and bulbous (fluidal) peperites in latiandesitic lavas (Pacacua Formation) or brechoid peperitic pipes in ignimbrites (Mata de Limón Member) or possible brechoid peperites in lavas in the Crucitas mining prospect (Cureña Formation), or simple brechoid peperites in andesitic flow (Pacacua Formation, in Talamanca) or as hydroclastic breccias with fragments of dacitic composition in lava flow deposits of Carbonal Guanacaste, just between the beaches Cabuyal and Naranjo. All these rocks represented proximal equivalents of the explosive, effusive and subvolcanic volcanism (endogenous domes and criptodomes) and his concomitance with the fluvial sedimentation. In Quaternary period, we have a sample in the base of Tiribí Formation in contact with Palmares Lacustrine. Also this paper included possible and potential cases. It hopes that the description and interpretation of this type of rocks helps to its identification in other regions of Costa Rica and Central America in general, as well as a potential source for the exploration of valuable metals [ABSTRACT FROM AUTHOR]

We highlight the contributions of Dr. Paul Schaufelberger, who arrived to Costa Rica in 1929, contracted by the government, to teach geology at the Liceo de Costa Rica, Colegio Superior de Señoritas and Escuela Nacional de Agricultura. He was the director of the department of Geology and Mineralogy of the Centro Nacional de Agricultura located at San Pedro de Montes de Oca in what is now Ciudad Universitaria Rodrigo Facio. In his work Schaufelberger contributed scientific and disclosure papers about geology as known in his time. He wrote many papers that served as guidance for the lessons related to the subject of Geology in Costa Rica. He left the country in 1939 hired by the Federación de Cafetaleros de Colombia with the purpose of performing geologic field studies intended for the betterment of the Colombian coffee industry. Schaufelberger died in 1976 in Colombia. [ABSTRACT FROM AUTHOR]

The aim of this paper is to describe a fragment of left mandible of a juvenile specimen of Pliometanastes. That found brings some light about the phyletic relations among Pliometanastes protistus Hirschfeld & Webb, 1968 and ?Pliometanastes galushai Hirschfeld & Webb, 1968, and strongly suggests that Pliometanastes is a monospecific genus. [ABSTRACT FROM AUTHOR]

This paper summarizes available information on soil clay mineralogy in topsoils of Costa Rica, including clay minerals described in B horizons when significantly different from predominant mineralogy in the topsoil. The soil clay suites ("predominant clay groups") emphasized are grouped as: (1) smectites and interstratified clays (Vertisols and other soils with vertic properties), and (2) oxides-hidroxides-oxihidroxides-kaolinite-gibbsite (in Alfisols, Ultisols and Oxisols). The soil clay genesis of these dominant groups is discussed when enough information is available. [ABSTRACT FROM AUTHOR]

Findings in a total of 84 research papers identifying clay minerals on 520 soil samples of Costa Rica are summarized. This review emphasizes on the clay minerals described in the topsoil samples, although clay minerals in the B horizons are also discussed when they are different to predominant mineralogy in the topsoil. Sites where soil clays information is available were geo-referenced, to observe their geographical distribution. In general most of the country possesses soil clays identified, except for the Nicoya Peninsula, the Northern Zone, and the Eastern Talamanca Range. Clay mineralogy suites ("predominant clay groups") were grouped as: (1) vitrous-amorphous-halloysitic (Andisols and other soils with andic properties; (2) smectites and interstratified clays (Vertisols and other soils with vertic properties); (3) oxides-hidroxides-oxihidroxides-kaolinite-gibbsite (Alfisols, Ultisols and Oxisols); Plus a large area of soils with mixed clay mineralogy, found in places with little or no development (Entisols and Inceptisols). The soil clay genesis of the main clay types in the country is discussed when enough information was available. [ABSTRACT FROM AUTHOR]

During the night of December 8th, 1994, along an unstable area at the northern flank of Irazú volcano, Costa Rica, a small volcanic debris avalanche and subsequent debris flows took place, followed by an "ashfall" that reached 30 km southwest from the volcano. At that time, these processes were interpreted as the result of a phreatic explosion. However, a review of the descriptions given in the technical reports and other documents of the time, together with the analysis of the geomorphology obtained from aerial photographs taken on December 20, 1994, by the Costa Rica National Geographic Institute, lead to discuss the validity of this interpretation, which although not ruled out, it seems unlikely. This paper proposes, based on the facts and information available, a new hypothesis of the occurrence of a volcanic debris avalanche resulting from a major landslide near the northern summit area. Consequently, the following "ash" fall could be interpreted as generated by the dust produced by auto-fragmentation of the debris avalanche, so subsequently called co-debris avalanche dust-cloud deposit. [ABSTRACT FROM AUTHOR]

This paper analyses the relationship between soil clay mineralogy classes and soil fertility characteristics of soils cultivated with banana in the Caribbean lowlands of Costa Rica. The results corroborate that some fertility properties are closely related to the amount and type of dominant clay of the soils; among these characteristics the most relevant are CEC, phosphate retention and exchangeable cations. Soils belonging to the esmectitic clay mineralogy class showed greater values of CEC and exchangeable bases but lower phosphorus retention than soils of the metahalloysitic clay mineralogy class. Soil dominated by vermiculite showed lower amounts of available K and larger amounts of exchangeable Mg. [ABSTRACT FROM AUTHOR]

This paper deals with the research carried out by Eng. Luis Matamoros Sandoval, who in 1902 published in Costa Rica his investigations on seismology in an article entitled "El interior de la corteza terrestre: una nueva teoría sobre el origen de los temblores" (The interior of the Earth's crust: a new theory about the origin of earthquakes). In his work, Matamoros followed the Aristotelic current and mixed it with the hypothesis developed by the Spanish friar Benito Feijoo, who proposed electricity as the physical cause of intense earthquakes perceived over large regions. Matamoros justifies his results by the use of mathematics combined with fundamental physical principles, some which he had great difficulty to explain due in part to the use of criteria and basic concepts that were not supported by the traditional physical knowledge. Despite his conceptual errors, the value of his work resides in the fact that it was the first local formal scientific attempt to explain the origin of earthquakes, a process that even in the great scientific centers of the period was the source of continuous speculation. [ABSTRACT FROM AUTHOR]

Data collection of astronomical phenomena in Costa Rica began at the end of the colonial period (1799). Most of this information reveals the social impact that they caused in the region. Scholars of that time tried to find a rational explanation for those phenomena, especially meteor showers and meteorites, in order to contrast the religious conceptions. This paper analyzes the most representative data obtained from the observations during the period 1799-1910. [ABSTRACT FROM AUTHOR]

In this paper we described fossil dunes found at the Islas Murciélago, Área de Conservación Guanacaste, south of the Santa Elena Peninsula, on the northwest part of Costa Rica. Currently, this region is exposed to strong winds during the dry season (December to May), which produce coastal dunes. This process has been active at least since the Upper Pleistocene, as we propose with the finding of the fossil dunes in the area. These dunes have a maximum corrected age, based on a 14C radiometric dating, between 15 981 and 17 132 years before the present, which coincide with the Heinrich 1 event. This finding indicates a paleoclimate of the region as very dry and with very strong winds, related to the Heinrich 1 event after the Last Glacial Maximum, which was a dry period. The direction of the wind, based on the stratigraphy, was NE to SW and from the NNW to the SSE. These directions correspond with the present day winds. [ABSTRACT FROM AUTHOR]