No. Registros Solicitud 1 5614 colombia

DE - DESCRIPTORS: acceleration-; accelerograms-; aseismic-design; Colombia-; data-processing; detection-; earthquakes-; foundations-; Fourier-analysis; ground-motion; microearthquakes-; Pereira-Colombia; risk-assessment; seismic-risk; seismicity-; soil-mechanics; South-America; strong-motion; technology-

CC - CATEGORY CODES: 30-Engineering-geology; 19-Seismology

DT - DOCUMENT TYPE: Serial; Conference-Document

BL - BIB LEVEL: Analytic

MC - MAP COORDINATES: LAT: N043000; N053000; LONG: W0750000; W0760000.

IL - ILLUSTRATION: Refs: 12; illus. incl. 4 tables, geol. sketch map.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands

IS - ISSN: 0267-7261

AN - ACCESSION NUMBER: 2002-018241

UD - UPDATE CODE: 200207

Registro 610 de 5614 - GeoRef : 2002-2004/12

TI - TITLE: How to improve reservoir characterization models using intelligent systems.

AU - AUTHORS: Soto-B-Rodolfo; Torres-Fredy; Arango-Sandro; Cobaleda-Gloria; Holditch-Stephen; Wu-Ching

AF - AUTHOR AFFILIATION: Ecopetrol-Instituto Colombiano del Petroleo, Bucaramanga, Colombia

BK - BOOK TITLE: In: Soft computing for reservoir characterization and modeling.

BA - BOOK AUTHORS: Wong-Patrick-M (editor); Aminzadeh-Fred (editor); Nikravesh-Masoud (editor)

SO - SOURCE: Studies in Fuzziness and Soft Computing. 80; Pages 387-417. 2002.

PB - PUBLISHER: Physica-Verlag. Heidelberg, Federal Republic of Germany. 2002.

CP - COUNTRY OF PUBLICATION: Federal-Republic-of-Germany

PY - PUBLICATION YEAR: 2002

LA - LANGUAGE: English

DE - DESCRIPTORS: fuzzy-logic; Lamar-Field; Maracaibo-Basin; mathematical-methods; models-; multivariate-analysis; neural-networks; petroleum-engineering; principal-components-analysis; reservoir-properties; soft-computing-techniques; South-America; statistical-analysis; Venezuela-

CC - CATEGORY CODES: 29A-Economic-geology,-geology-of-energy-sources

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

IL - ILLUSTRATION: Refs: 18; illus. incl. 1 table, geol. sketch map.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute.

IS - ISSN: 1434-9922

IB - ISBN: 3-7908-1421-0

AN - ACCESSION NUMBER: 2002-017401

UD - UPDATE CODE: 200207

Registro 611 de 5614 - GeoRef : 2002-2004/12

TI - TITLE: Lithium isotopes as a probe of weathering processes; Orinoco River.

AU - AUTHORS: Huh-Youngsook; Chan-Lui-Heung; Edmond-John-M

AF - AUTHOR AFFILIATION: Northwestern University, Department of Geological Sciences, Evanston, IL, United States

SO - SOURCE: Earth and Planetary Science Letters. 194; 1-2, Pages 189-199. 2001.

PB - PUBLISHER: Elsevier. Amsterdam, Netherlands. 2001.

CP - COUNTRY OF PUBLICATION: Netherlands

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: English

AB - ABSTRACT: Lithium isotopes have the potential to be effective tracers of weathering processes due to their large relative mass difference and therefore fractionation. In this study an attempt is made to fill a major gap in the knowledge of Li isotope fractionation during continental weathering and of the mechanisms involved. Finally the relationship between the suspended and dissolved material is made on a basin-wide scale. The Orinoco basin provides a clear contrast in reaction-limited and transport-limited weathering regimes that has already been documented by a comprehensive study on its fluvial geochemistry (Edmond et al., Geochim. Cosmochim. Acta 60 (1996) 2949-2976; Edmond et al., Geochim. Cosmochim. Acta 59 (1995) 3301-3325). Conspicuous in our new results is the difference in delta (super 6) Li of the dissolved load between the Andean (-30 to -22 per mil) and Shield (-22 to -7 per mil) tributaries, while the delta (super 6) Li of the suspended load is similar between the two. To a first approximation, during superficial weathering in high-relief, tectonically active terrains the dissolved load is high in Li and isotopically heavy (more negative delta (super 6) Li), whereas in stable Shield regions the concentrations are low and isotopically light in proportion to the increasing degree of weathering.

DE - DESCRIPTORS: alkali-metals; bedload-; Colombia-; dissolved-materials; drainage-basins; fluvial-environment; geochemical-indicators; geochemistry-; Guyana-Shield; hydrology-; isotope-ratios; isotopes-; Li-6; Li-7; Li-7-Li-6; lithium-; metals-; Orinoco-River-basin; rivers-and-streams; South-America; stable-isotopes; suspended-materials; tributaries-; Venezuela-; weathering-

CC - CATEGORY CODES: 21-Hydrogeology; 02D-Isotope-geochemistry

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

IL - ILLUSTRATION: Refs: 35; illus. incl. 1 table, sketch map.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands

IS - ISSN: 0012-821X

CO - CODEN: EPSLA2

AN - ACCESSION NUMBER: 2002-016646

UD - UPDATE CODE: 200206

Registro 612 de 5614 - GeoRef : 2002-2004/12

TI - TITLE: Secuencias didacticas para la ensenanza de la geologia economica; una reflexion critica

Translated Title: Didactic sequence for the teaching of economic geology; a critical review.

AU - AUTHORS: Celino-Joil-Jose

AF - AUTHOR AFFILIATION: DGGA-IG, Pos-Graduacao de Geoquimica e Meio Ambiente, Salvador, Brazil

SO - SOURCE: Geologia Colombiana. 25; Pages 251-255. 2001.

PB - PUBLISHER: Universidad Nacional de Colombia, Facultad de Ciencias, Departamento de Geociencias. Bogota, Colombia. 2001.

CP - COUNTRY OF PUBLICATION: Colombia

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: Portuguese

LS - LANGUAGE OF SUMMARY: English

AB - ABSTRACT: An alternative methodological framework to the traditional teaching of economic geology is proposed. We intend to give an answer to the didactic difficulties with respect to the learning of economic geology. Geoscience education to future mining engineers has to be thought in this sense with three aims: (1) showing to future citizens the nature of geoscience; (2) beginning to teach to future scientists how to do geoscience; (3) teaching to students some features of the natural world.

DE - DESCRIPTORS: college-level-education; economic-geology; economics-; education-; energy-sources; environmental-management; graduate-level-education; mineral-resources; natural-resources; water-resources

CC - CATEGORY CODES: 26B-Economic-geology,-general,-economics

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

IL - ILLUSTRATION: Refs: 12; illus. incl. 2 tables.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute.

IS - ISSN: 0072-0992

CO - CODEN: GECBA7

AN - ACCESSION NUMBER: 2002-016229

UD - UPDATE CODE: 200206

Registro 613 de 5614 - GeoRef : 2002-2004/12

TI - TITLE: Analisis neotectonico de un area ubicada al oriente del Municipio de Pasca, Departamento de Cundinamarca

Translated Title: Neotectonics east of the Pasca Municipality, Department of Cundinamarca.

AU - AUTHORS: Acosta-G-Jorge-Enrique; Hernandez-Pardo-Orlando

AF - AUTHOR AFFILIATION: INGEOMINAS, Area de Geologia, Santafe de Bogota, Colombia

SO - SOURCE: Geologia Colombiana. 25; Pages 241-249. 2001.

PB - PUBLISHER: Universidad Nacional de Colombia, Facultad de Ciencias, Departamento de Geociencias. Bogota, Colombia. 2001.

CP - COUNTRY OF PUBLICATION: Colombia

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: Spanish

LS - LANGUAGE OF SUMMARY: English

AB - ABSTRACT: The central part of the Andean range, east of the Pasca town, presents a series of geomorphologic features that are typical of active tectonic areas. A morphological analysis has been carried out based on satellite images and areal photos. It was possible to outline two main lineament systems with N10 degrees E and N45 degrees W strikes, respectively, along which a series of geoforms suggesting neotectonic events that had faulted and deformed quaternary deposits. Based on the above information and field control, each lineament was characterized, confirming the presence of the Cajitas Fault and its neotectonic activity.

DE - DESCRIPTORS: active-faults; Andes-; Bogota-Colombia; Cajitas-Fault; Cenozoic-; Colombia-; Cundinamarca-Colombia; Eastern-Cordillera; faults-; imagery-; Landsat-; landslides-; lineaments-; mass-movements; neotectonics-; Northern-Andes; Pasca-Colombia; Quaternary-; remote-sensing; satellite-methods; seismotectonics-; South-America; tectonics-

CC - CATEGORY CODES: 16-Structural-geology

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

MC - MAP COORDINATES: LAT: N041000; N044500; LONG: W0734500; W0743000.

IL - ILLUSTRATION: Refs: 13; illus. incl. geol. sketch maps.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute.

IS - ISSN: 0072-0992

CO - CODEN: GECBA7

AN - ACCESSION NUMBER: 2002-016228

UD - UPDATE CODE: 200206

Registro 614 de 5614 - GeoRef : 2002-2004/12

TI - TITLE: Geoquimica del rubidio-estroncio y edad de las esmeraldas Colombianas

Translated Title: Rubidium-strontium age and geochemistry of Colombian emeralds.

AU - AUTHORS: Romero-Ordonez-Fernando-H; Schultz-Guetter-R-A; Kogi-Kawashita

AF - AUTHOR AFFILIATION: Universidad Nacional de Colombia, Departamento de Geociencias, Bogota, Colombia

SO - SOURCE: Geologia Colombiana. 25; Pages 221-239. 2001.

PB - PUBLISHER: Universidad Nacional de Colombia, Facultad de Ciencias, Departamento de Geociencias. Bogota, Colombia. 2001.

CP - COUNTRY OF PUBLICATION: Colombia

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: Spanish

LS - LANGUAGE OF SUMMARY: English

AB - ABSTRACT: The rubidium-strontium method has been worked to determine the age of some Colombian emeralds. These emeralds have low radiogenic strontium enrichments because of their younger age and their low rubidium content; they also have relatively high primary strontium content. Although the age of the emeralds of geologically younger formations is more difficult to establish, isotope values of these emeralds plotted on a graph of (super 87) Sr/ (super 86) Sr vs (super 87) Rb/ (super 86) Sr is indicative of about 61 to 67 million years as the age of mineralization.

DE - DESCRIPTORS: absolute-age; alkali-metals; alkaline-earth-metals; Andes-; Cenozoic-; Central-Cordillera; concentration-; crystal-chemistry; dates-; Eastern-Cordillera; emerald-; enrichment-; isotope-ratios; isotopes-; Llanos-; metals-; Neogene-; Northern-Andes; Pliocene-; radioactive-isotopes; Rb-87-Sr-86; Rb-Sr; ring-silicates; rubidium-; Santander-Massif; silicates-; South-America; Sr-87-Sr-86; stable-isotopes; strontium-; Tertiary-

CC - CATEGORY CODES: 01B-Mineralogy-of-silicates; 03-Geochronology

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

MC - MAP COORDINATES: LAT: N050000; N070000; LONG: W0720000; W0750000.

IL - ILLUSTRATION: Refs: 56; illus. incl. 3 tables, sketch map.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute.

IS - ISSN: 0072-0992

CO - CODEN: GECBA7

AN - ACCESSION NUMBER: 2002-016227

UD - UPDATE CODE: 200206

Registro 615 de 5614 - GeoRef : 2002-2004/12

TI - TITLE: Condicoes de cristalizacao dos charnockitos igneos no nordeste do Brasil

Translated Title: Crystallization conditions of igneous charnockite in northeastern Brazil.

AU - AUTHORS: Celino-Joil-Jose; Botelho-Nilson-Francisquini

AF - AUTHOR AFFILIATION: Universidade Federal de Bahia, DGGA, IGEO, Bahia, Brazil

SO - SOURCE: Geologia Colombiana. 25; Pages 199-220. 2001.

PB - PUBLISHER: Universidad Nacional de Colombia, Facultad de Ciencias, Departamento de Geociencias. Bogota, Colombia. 2001.

CP - COUNTRY OF PUBLICATION: Colombia

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: Spanish

LS - LANGUAGE OF SUMMARY: English

AB - ABSTRACT: Orthopyroxene-bearing felsic and mafic rocks are important components of the transition zone between the Archean Sao Francisco Craton and the late Proterozoic Coastal Mobile Belt in southeastern Bahia, Brazil. The charnockites have relict magmatic textures. Thermobarometic calculations based on several exchange thermometers and one barometer suggest temperatures between 700 and 800 degrees C and a pressure of 4.5 and 5.5 kbar ( approximately 12-17 km depth) for the generation of these rocks. In the studied rocks there are many textural indications for the instability of minerals used in the exchange thermobarometers, suggesting that the interpretation of temperature and pressure conditions of granulite facies rocks is more accurate when based on the principles of the equilibrium of phases. Field evidence, supplemented by mineralogical and textural data suggests an origin by partial melting of deep continental crust under the dry conditions of granulite facies.

DE - DESCRIPTORS: Archean-; Bahia-Brazil; Brazil-; charnockite-; chemical-composition; chemical-properties; continental-crust; crust-; crystallization-; equilibrium-; facies-; granites-; granulite-facies; igneous-rocks; mafic-composition; mineral-composition; mobile-belts; northeastern-Brazil; partial-melting; physical-properties; plutonic-rocks; Precambrian-; Proterozoic-; Sao-Francisco-Craton; South-America; upper-Precambrian

CC - CATEGORY CODES: 05A-Igneous-and-metamorphic-petrology

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

MC - MAP COORDINATES: LAT: S182000; S160000; LONG: W0383000; W0413000.

IL - ILLUSTRATION: Refs: 66; illus. incl. 6 tables, geol. sketch map.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute.

IS - ISSN: 0072-0992

CO - CODEN: GECBA7

AN - ACCESSION NUMBER: 2002-016226

UD - UPDATE CODE: 200206

Registro 616 de 5614 - GeoRef : 2002-2004/12

TI - TITLE: Caracterizacion geoquimica y petrografia de los cuerpos intrusivos basicos, aflorantes en la region de Caceres y Puerto Romero, departamentos de Cundinamarca y Boyaca, Colombia

Translated Title: Geochemical and petrographic characterization of basic intrusive bodies in the Caceres region and Puerto Romero, departments of Cundinamarca and Boyaca, Colombia.

AU - AUTHORS: Vasquez-Parra-Monica; Concha-Perdomo-Ana-Elena; Moreno-Murillo-Juan-Manuel; Patarroyo-Gama-Pedro

AF - AUTHOR AFFILIATION: Universidad Nacional de Colombia, Departamento de Geociencias, Bogota, Colombia

SO - SOURCE: Geologia Colombiana. 25; Pages 185-198. 2001.

PB - PUBLISHER: Universidad Nacional de Colombia, Facultad de Ciencias, Departamento de Geociencias. Bogota, Colombia. 2001.

CP - COUNTRY OF PUBLICATION: Colombia

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: Spanish

LS - LANGUAGE OF SUMMARY: English

AB - ABSTRACT: In the Caceres-Puerto Romero area, crop out some basic intrusive bodies shaped like sills and dikes, which are intruding the cretaceous sedimentary rocks of La Paja and Simiti formations. In a broad outline, they show "pseudostratification" and a regional trench of N 10-20 degrees E, as remarkable features. The geochemical characterisation carrying through for the analysed samples, shows SiO (sub 2) concentrations between 50 and 57%, belonging to the subalcaline series with sodic tendency and tholeiitic character; geochemically they are gabbros, granodiorites and diorites. Regarding to the petrography, they are composed mostly of intermediate to calcic plagioclase, pyroxenes (augite, diopside and hypersthene) and quartz. Amongst the prevailing textures found in these rocks are ophitic, subophitic and granular. For geochemical characterization and for tectonic environment discrimination were used diagrams developed originally for effusive rocks by different authors. In accordance with the results obtained in this work, it is possible to state that the origin of the basic intrusive bodies took place at the distensive within plate setting, as a consequence of the formation of an intercontinental rift at the Berriasian-Coniacian ages. In this period the sizeable thinning of the continental crust gave rise to a set of very deep faults along which began the rising of the magma as a result of partial melt of the mantle.

DE - DESCRIPTORS: Berriasian-; Boyaca-Colombia; chemical-composition; Colombia-; Coniacian-; correlation-; Cretaceous-; Cundinamarca-Colombia; dikes-; diorites-; gabbros-; geochemistry-; geologic-maps; granites-; granodiorites-; igneous-rocks; intrusions-; La-Paja-Formation; lithostratigraphy-; Lower-Cretaceous; maps-; Mesozoic-; petrography-; plutonic-rocks; relative-age; sedimentary-rocks; Senonian-; sills-; Simiti-Formation; South-America; tectonics-; tholeiitic-composition; Upper-Cretaceous

CC - CATEGORY CODES: 05A-Igneous-and-metamorphic-petrology

DT - DOCUMENT TYPE: Serial; Map

BL - BIB LEVEL: Analytic

MC - MAP COORDINATES: LAT: N040000; N060000; LONG: W0720000; W0750000.

MS - MAP SCALE: 1:50,000

MP - MAP TYPE: geologic-maps

IL - ILLUSTRATION: Refs: 29; illus. incl. 3 tables.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute.

IS - ISSN: 0072-0992

CO - CODEN: GECBA7

AN - ACCESSION NUMBER: 2002-016225

UD - UPDATE CODE: 200206

Registro 617 de 5614 - GeoRef : 2002-2004/12

TI - TITLE: Contexto geologico dos notossuquios (Crocodylomorpha) cretacicos do Brasil

Translated Title: Geologic context of Cretaceous Notosuchia (Crocodylomorpha) of Brazil.

AU - AUTHORS: Carvalho-Ismar-de-Souza; Bertini-Reinaldo-Jose

AF - AUTHOR AFFILIATION: Universidade Federal do Rio de Janeiro, Dept. de Geologia, Rio de Janeiro, Brazil

SO - SOURCE: Geologia Colombiana. 25; Pages 163-184. 2001.

PB - PUBLISHER: Universidad Nacional de Colombia, Facultad de Ciencias, Departamento de Geociencias. Bogota, Colombia. 2001.

CP - COUNTRY OF PUBLICATION: Colombia

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: Portuguese

LS - LANGUAGE OF SUMMARY: English

AB - ABSTRACT: Notosuchians were a peculiar group of small Cretaceous "mesosuchian" crocodilomorphs with a relatively high skull, pre-orbital region laterally compressed, short mandibular fenestra, reduced and specialized dentition, and primitive characters on the palatal region. They have been recovered from continental Cretaceous deposits in South America (Brazil, Uruguay and Argentina), Africa (Niger and Malawi) and Asia (China). In Brazil they have been found in Araripe, Parnaiba and Bauru basins. The first is a rift basin and the last two are wide intracratonic basins, with a high thickness of Cretaceous continental sediments. Apparently the occurrences of notosuchians in Brazil are limited to rocks from Aptian to Upper Cretaceous strata (? Maastrichtian). From the Araripe Basin (Northeastern Brazil, Ceara State) comes Araripesuchus gomesii, found at an Aptian-Albian sequence (Santana Formation) in carbonate nodules, which are interpreted to have been originated in shallow, fresh to brackish water ponds, lying along the coast in a hot and dry climate. There is an unique species of notosuchian from Parnaiba Basin (Northeastern Brazil, Maranhao State), Candidodon itapecuruense, from the Albian Itapecuru Formation. The sequence of siliciclastic strata, where this fossil was found, indicates a channel of a meandering river system. Palynological data suggest a hot and humid climate in that area. The Bauru Basin notosuchians (southeastern Brazil, Sao Paulo State) occur in siliciclastic Upper Cretaceous sediments (Adamantina and Aracatuba formations). The fine quartzose sandstones and siltstones, of probable Coniacian to Campanian age, are interpreted as deposited by braided rivers through a wide alluvian plain and lakes. The climate was hot and dry, in a semi-arid environment. The many environmental settings where notosuchians have been found, meandering river floodplain, braided alluvial plain and shallow ponds, could explain the diversity of this peculiar crocodylomorph group in Brazil.

DE - DESCRIPTORS: Adamantina-Formation; Albian-; Aptian-; Araripe-Basin; Archosauria-; basins-; Bauru-Basin; brackish-water-environment; Brazil-; Chordata-; correlation-; Cretaceous-; Crocodilia-; Diapsida-; fluvial-environment; functional-morphology; intracratonic-basins; Itapecuru-Formation; Lower-Cretaceous; Mesozoic-; morphology-; Notosuchia-; paleoenvironment-; Parnaiba-Basin; Reptilia-; Santana-Formation; siliciclastics-; skulls-; South-America; taxonomy-; teeth-; Tetrapoda-; Vertebrata-

CC - CATEGORY CODES: 11-Vertebrate-paleontology

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

MC - MAP COORDINATES: LAT: S080000; S060000; LONG: W0380000; W0410000.

IL - ILLUSTRATION: Refs: 48; illus. incl. geol. sketch maps.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute.

IS - ISSN: 0072-0992

CO - CODEN: GECBA7

AN - ACCESSION NUMBER: 2002-016224

UD - UPDATE CODE: 200206

Registro 618 de 5614 - GeoRef : 2002-2004/12

TI - TITLE: Distribucion de Amonitas del Barremiano de la Formacion Paja en el sector de Villa de Leyva (Boyaca, Colombia); bioestratigrafia

Translated Title: Distribution of Barremian Ammonites in the Paja Formation, Villa de Leyva, Boyaca, Colombia; biostratigraphy.

AU - AUTHORS: Patarroyo-Pedro

AF - AUTHOR AFFILIATION: Universidad Nacional de Colombia, Departamento de Geociencias, Bogota, Colombia

SO - SOURCE: Geologia Colombiana. 25; Pages 149-162. 2001.

PB - PUBLISHER: Universidad Nacional de Colombia, Facultad de Ciencias, Departamento de Geociencias. Bogota, Colombia. 2001.

CP - COUNTRY OF PUBLICATION: Colombia

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: Spanish

LS - LANGUAGE OF SUMMARY: English

AB - ABSTRACT: In the Barremian sedimentary succession of the Paja Formation in the Villa de Leyva area (Boyaca, Colombia), was found an ammonite fauna that allows to propose a biostratigraphy to correlate with the standard Mediterranean ammonite zones. The Early Barremian contains the Psilotissotia colombiana, Nicklesia pulchella and Pulchellia galeata zones. The Late Barremian Heinzia (Gerhardtia) veleziensis and Colchidites breistrofferi zones. With the proposed biostratigraphy is possible a re-evaluation of Burgls' ideas about the Barremian of Colombia, and to give precision to the vertical distribution of the collected ammonites in four sections near Villa de Leyva. It is confirmed that the lower boundary of the Barremian and the Aptian in Colombia are not yet clearly defined.

DE - DESCRIPTORS: Ammonites-; Ammonoidea-; Aptian-; Barremian-; biostratigraphy-; Boyaca-Colombia; Cephalopoda-; Colombia-; correlation-; Cretaceous-; Invertebrata-; Lower-Cretaceous; Mesozoic-; Mollusca-; Paja-Formation; South-America; Tetrabranchiata-; Villa-de-Leyva-Colombia

CC - CATEGORY CODES: 12-Stratigraphy

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

MC - MAP COORDINATES: LAT: N050000; N063000; LONG: W0720000; W0740000.

IL - ILLUSTRATION: Refs: 35; illus. incl. strat. col., sketch map.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute.

IS - ISSN: 0072-0992

CO - CODEN: GECBA7

AN - ACCESSION NUMBER: 2002-016223

UD - UPDATE CODE: 200206