No. Registros Solicitud 1 5614 colombia

PB - PUBLISHER: Geological Society of America (GSA). Boulder, CO, United States. 1996.

CP - COUNTRY OF PUBLICATION: United-States

PY - PUBLICATION YEAR: 1996

CN - CONFERENCE INFORMATION: Geological Society of America, 28th annual meeting. Denver, CO, United States. Oct. 28-31, 1996.

LA - LANGUAGE: English

AB - ABSTRACT: Permian brachiopod faunas are diverse and abundant throughout South and North America, and are present in both autochthonous basins and allochthonous terranes of the circum-Pacific margin. Current tectonic models posit numerous allochthonous terranes and collisional orogenesis for the Late Paleozoic--Mesozoic of North America and non-collisional (= Andean-type) orogenesis for South America--differences which are confirmed by paleobiogeographic patterns of highly provincial Permian brachiopod faunas. A database of over 250 Permian brachiopod genera from over 100 localities in South and North America is now supplemented with descriptions of new brachiopod faunas from Chile and Colombia. The database was analyzed via parsimony analysis of endemism (PAE), probabilistic similarity and multivariate statistical methods, including cluster, principal components and correspondence analysis. Comparison of results for South and North America reveals: 1) both continents show paleolatitudinally controlled variation in composition and diversity within demonstrably autochthonous basins, 2) the tropical areas of the American Permian had several endemic centers as did the Tethyan region, 3) the number and extent of paleobiogeographic anomalies (= allochthonous terranes) is far greater in North America, and 4) there is no evidence of South American faunas with Tethyan affinity.

DE - DESCRIPTORS: allochthons-; autochthons-; biogeography-; Brachiopoda-; Chile-; Colombia-; data-bases; data-processing; endemic-taxa; Invertebrata-; models-; North-America; orogeny-; paleogeography-; paleolatitude-; paleomagnetism-; Paleozoic-; Permian-; South-America; species-diversity; terranes-; Tethys-; variations-

CC - CATEGORY CODES: 12-Stratigraphy

DT - DOCUMENT TYPE: Abstract; Serial; Conference-Document

BL - BIB LEVEL: Analytic

RF - REFERENCE SOURCE: GeoRef, Copyright 2000, American Geological Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States

IS - ISSN: 0016-7592

CO - CODEN: GAAPBC

AN - ACCESSION NUMBER: 1997-048399

UD - UPDATE CODE: 199716

Registro 4728 de 5614 - GeoRef Disc 4: 1993-1996

BK - BOOK TITLE: Architecture of estuarine reservoirs of the Cretaceous, Caballos Formation Orito Field, Putumayo Basin, Colombia.

BA - BOOK AUTHORS: Amaya-Carlos-Alberto

CP - COUNTRY OF PUBLICATION: United-States

PY - PUBLICATION YEAR: 1996

DG - DEGREE GRANTED: Master's

DI - DEGREE GRANTING INSTITUTION: University of Texas, Austin. Austin, TX, United States. Pages: 106. 1996.

LA - LANGUAGE: English

AB - ABSTRACT: Orito Field occupies an area of 31 mi (super 2) (80 km (super 2) ) in the west-central portion of the Putumayo Basin, Colombia and forms part of an extensive littoral system that dominated sedimentation during Albian-Aptian time. The Caballos Formation represents the oldest Cretaceous unit, and was deposited at the beginning of a retrogradational episode immediately above the eroded Triassic-Jurassic surface. The Caballos Formation has an average thickness of 240 ft (73 m) and is largely composed of fine grained, highly compacted quartzarenites, cemented by quartz and kaolinite. A geologic model integrating all the available information allows the definition of four depositional events in the Caballos. The lowest depositional unit is composed of fluvial deposits with minor tidal influence. These fluvial sands grade upward into estuarine deposits formed in tidal channels and tidal flats, that are in turn overlain by tidal channel deposits, and are finally eroded and overlain by tidal mouth bars deposits. The vertical facies association is the product of a retrogradational episode and represents deposition in a tide-modified estuary, inside which diagenetic processes acted differently modifying the petrophysical properties of the facies that compose the Caballos reservoir in Orito field. Historical production trends of the Caballos reservoir correlate with the major depositional axes defined in this study and allow to delineation of high potential areas for future development, by means of targeted infill drilling and workovers.

DE - DESCRIPTORS: arenite-; Caballos-Formation; clastic-rocks; Colombia-; Cretaceous-; depositional-environment; estuarine-environment; lithofacies-; Mesozoic-; models-; oil-and-gas-fields; Orito-Field; petroleum-; Putumayo-Basin; quartz-arenite; reservoir-rocks; sedimentary-rocks; South-America

CC - CATEGORY CODES: 29A-Economic-geology,-geology-of-energy-sources; 06A-Sedimentary-petrology

DT - DOCUMENT TYPE: Thesis-or-Dissertation

BL - BIB LEVEL: Monograph

IL - ILLUSTRATION: illus.

RF - REFERENCE SOURCE: GeoRef, Copyright 2000, American Geological Institute.

AN - ACCESSION NUMBER: 1997-048714

UD - UPDATE CODE: 199716

Registro 4729 de 5614 - GeoRef Disc 4: 1993-1996

BK - BOOK TITLE: Oligocene-Miocene depositional history of the northern part of the lower Magdalena Basin, Colombia, based on foraminiferal biofacies and seismic stratigraphy.

BA - BOOK AUTHORS: Beltran-Martha-Zoraida

CP - COUNTRY OF PUBLICATION: United-States

PY - PUBLICATION YEAR: 1996

DG - DEGREE GRANTED: Master's

DI - DEGREE GRANTING INSTITUTION: University of Texas, Austin. Austin, TX, United States. Pages: 162. 1996.

LA - LANGUAGE: English

AB - ABSTRACT: Micropaleontological studies and seismic interpretation allow for the reconstruction of the depositional history of Oligocene-Miocene deposits from the northern part of the Lower Magdalena basin, in the northwest of Colombia. Micropaleontological analysis of 283 well-cutting samples from four wells in the southeastern El Plato sub-basin was used to characterize foraminiferal assemblages recovered from Oligocene through Miocene strata. Paleoenvironmental changes are recognized in the three well sections that yielded foraminifera. Three formations are penetrated by the wells. From bottom to top, these are: the Cienaga de Oro, Porquero and San Antonio formations. Foraminifera recovered from the lower Cienaga de Oro Formation were mostly the result of down-hole contamination but, recovery of foraminiferal faunas in the Porquero and San Antonio formations was good to excellent. Biofacies trends are defined using a combination of multivariate and ordination analyses. The Cienaga de Oro Formation represents a shallow deltaic to continental paleoenvironment. A rapid deepening event of at least 500 m occurred near the top of the formation. The Porquero Formation records middle bathyal deposition based on two closely related biofacies within the formation: the Lenticulina americana biofacies (A1), and the Uvigerina capayana biofacies (A2); these two faunal associations are differentiated on the basis of water mass properties. The Ammonia beccarii biofacies (B) within The San Antonio Formation represents shallow marine (inner neritic) deposits. Interpretation of seismic lines indicates that the first and largest deepening event was followed by east-northeast headward erosion of a submarine canyon through west-northwest prograded deltaic deposits. A complex canyon fill history was followed by two different offlaping episodes. Shoaling of the basin at the top of this offlaping complex is expressed by an unconformity.

DE - DESCRIPTORS: assemblages-; biofacies-; biostratigraphy-; Cenozoic-; Cienaga-de-Oro-Formation; Colombia-; Foraminifera-; Invertebrata-; Magdalena-Basin; microfossils-; Miocene-; multivariate-analysis; Neogene-; Oligocene-; paleoenvironment-; Paleogene-; Porquero-Formation; Protista-; San-Antonio-Formation; sedimentation-; seismic-stratigraphy; South-America; statistical-analysis; Tertiary-

CC - CATEGORY CODES: 12-Stratigraphy

DT - DOCUMENT TYPE: Thesis-or-Dissertation

BL - BIB LEVEL: Monograph

IL - ILLUSTRATION: illus.

RF - REFERENCE SOURCE: GeoRef, Copyright 2000, American Geological Institute.

AN - ACCESSION NUMBER: 1997-048716

UD - UPDATE CODE: 199716

Registro 4730 de 5614 - GeoRef Disc 4: 1993-1996

TI - TITLE: Understanding geology as the key to using seepage in exploration; the spectrum of seepage styles.

AU - AUTHORS: Thrasher-Jane; Fleet-Andrew-J; Hay-Stephen-J; Hovland-Martin; Dueppenbecker-Stephan

AF - AUTHOR AFFILIATION: BP Exploration, Research and Engineering Centre, Sunbury-on-Thames, United Kingdom

BK - BOOK TITLE: In: Hydrocarbon migration and its near-surface expression.

BA - BOOK AUTHORS: Schumacher-Dietmar (editor); Abrams-Michael-A (editor)

SO - SOURCE: AAPG Memoir. 66; Pages 223-241. 1996.

PB - PUBLISHER: American Association of Petroleum Geologists. Tulsa, OK, United States. 1996.

CP - COUNTRY OF PUBLICATION: United-States

PY - PUBLICATION YEAR: 1996

CN - CONFERENCE INFORMATION: AAPG Hedberg research conference. Vancouver, BC, Canada. April 24-28, 1994.

LA - LANGUAGE: English

DE - DESCRIPTORS: Arctic-Ocean; Atlantic-Ocean; California-; Colombia-; controls-; diapirs-; faults-; gas-chromatograms; geophysical-profiles; Gulf-of-Mexico; Haltenbanken-; Machar-Field; mass-spectra; migration-; natural-gas; North-America; North-Atlantic; North-Pacific; North-Sea; Norwegian-Sea; offshore-; oil-and-gas-fields; oil-seeps; Pacific-Ocean; petroleum-; petroleum-accumulation; petroleum-exploration; salt-tectonics; seismic-profiles; source-rocks; South-America; spectra-; tectonics-; traps-; two-dimensional-models; United-States; Viking-Graben; Western-Canada-Basin

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

DT - DOCUMENT TYPE: Serial; Conference-Document

BL - BIB LEVEL: Analytic

IL - ILLUSTRATION: Refs: 42; illus. incl. sects., sketch maps.

RF - REFERENCE SOURCE: GeoRef, Copyright 2000, American Geological Institute.

IS - ISSN: 0271-8529

IB - ISBN: 0-89181-345-4

AN - ACCESSION NUMBER: 1997-051861

UD - UPDATE CODE: 199717

Registro 4731 de 5614 - GeoRef Disc 4: 1993-1996

TI - TITLE: Surface geochemistry as an exploration tool in the South Caribbean.

AU - AUTHORS: Thrasher-Jane; Strait-David; Lugo-Ricardo-Alvarez

AF - AUTHOR AFFILIATION: BP Exploration, Research and Engineering Centre, Sunbury-on-Thames, United Kingdom

BK - BOOK TITLE: In: Hydrocarbon migration and its near-surface expression.

BA - BOOK AUTHORS: Schumacher-Dietmar (editor); Abrams-Michael-A (editor)

SO - SOURCE: AAPG Memoir. 66; Pages 373-384. 1996.

PB - PUBLISHER: American Association of Petroleum Geologists. Tulsa, OK, United States. 1996.

CP - COUNTRY OF PUBLICATION: United-States

PY - PUBLICATION YEAR: 1996

CN - CONFERENCE INFORMATION: AAPG Hedberg research conference. Vancouver, BC, Canada. April 24-28, 1994.

LA - LANGUAGE: English

DE - DESCRIPTORS: airborne-methods; aromatic-hydrocarbons; Atlantic-Ocean; biomarkers-; Caribbean-Sea; Cenozoic-; Colombia-; cores-; Cretaceous-; detection-; fragmentograms-; gas-chromatograms; geophysical-profiles; hopanes-; hopanoids-; hydrocarbons-; marine-environment; mass-spectra; Mesozoic-; middle-Tertiary; natural-gas; North-Atlantic; offshore-; oil-seeps; organic-compounds; organic-materials; petroleum-; petroleum-exploration; sampling-; seismic-profiles; source-rocks; South-America; southern-Caribbean-Sea; spectra-; steranes-; terpanes-; terrestrial-environment; Tertiary-; thermal-maturity; triterpanes-

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

DT - DOCUMENT TYPE: Serial; Conference-Document

BL - BIB LEVEL: Analytic

MC - MAP COORDINATES: LAT: N080000; N100000; LONG: W0751500; W0764500.

IL - ILLUSTRATION: Refs: 7; illus. incl. chart, sects., sketch map.

RF - REFERENCE SOURCE: GeoRef, Copyright 2000, American Geological Institute.

IS - ISSN: 0271-8529

IB - ISBN: 0-89181-345-4

AN - ACCESSION NUMBER: 1997-051873

UD - UPDATE CODE: 199717

Registro 4732 de 5614 - GeoRef Disc 4: 1993-1996

TI - TITLE: Tornillos at Galeras Volcano, Colombia; quasi-monochromatic, slowly decaying events.

AU - AUTHORS: Gomez-Diego; Torres-Roberto; Narvaez-M-Lourdes; Seidl-Dieter; Hellweg-Margaret; Rademacher-Horst

AF - AUTHOR AFFILIATION: Observatorio Vulcanlogico de Pasto, Pasto, Narino, Colombia

BK - BOOK TITLE: In: AGU 1996 fall meeting.

BA - BOOK AUTHORS: Anonymous

SO - SOURCE: Eos, Transactions, American Geophysical Union. 77; 46, Suppl., Pages 813. 1996.

PB - PUBLISHER: American Geophysical Union. Washington, DC, United States. 1996.

CP - COUNTRY OF PUBLICATION: United-States

PY - PUBLICATION YEAR: 1996

CN - CONFERENCE INFORMATION: American Geophysical Union 1996 fall meeting. San Francisco, CA, United States. Dec. 15-19, 1996.

LA - LANGUAGE: English

DE - DESCRIPTORS: Andes-; broad-band-spectra; Colombia-; earthquakes-; eruptions-; Galeras-; oscillations-; polarization-; seismic-energy; seismograms-; seismographs-; South-America; spectral-analysis; three-component-seismographs; tornillos-; volcanic-ash; volcanic-earthquakes; volcanoes-; volcanology-

CC - CATEGORY CODES: 19-Seismology

DT - DOCUMENT TYPE: Abstract; Serial; Conference-Document

BL - BIB LEVEL: Analytic

MC - MAP COORDINATES: LAT: N010000; N030000; LONG: W0770000; W0782000.

RF - REFERENCE SOURCE: GeoRef, Copyright 2000, American Geological Institute.

IS - ISSN: 0096-3941

CO - CODEN: EOSTAJ

AN - ACCESSION NUMBER: 1997-056851

UD - UPDATE CODE: 199718

Registro 4733 de 5614 - GeoRef Disc 4: 1993-1996

TI - TITLE: The response of geomorphic systems to climatic and hydrological change during the late glacial and early Holocene in the humid and sub-humid tropics.

AU - AUTHORS: Thomas-Michael-F; Thorp-Martin-B

AF - AUTHOR AFFILIATION: University of Stirling, Department of Environmental Science, Stirling, United Kingdom

BK - BOOK TITLE: In: Global continental changes; the context of palaeohydrology.

BA - BOOK AUTHORS: Branson-J (editor); Brown-A-G (editor); Gregory-K-J (editor)

SO - SOURCE: Geological Society Special Publications. 115; Pages 139-153. 1996.

PB - PUBLISHER: Geological Society of London. London, United Kingdom. 1996.

CP - COUNTRY OF PUBLICATION: United-Kingdom

PY - PUBLICATION YEAR: 1996

CN - CONFERENCE INFORMATION: Global continental changes; the context of palaeohydrology. Southampton, United Kingdom. Sept. 9-12, 1994.

LA - LANGUAGE: English

DE - DESCRIPTORS: Africa-; Amazon-Basin; Asia-; Borneo-; Cenozoic-; changes-; Colombia-; erosion-; Far-East; floodplains-; fluvial-environment; fluvial-features; Ghana-; Holocene-; humid-environment; Indonesia-; Kalimantan-Indonesia; Koidu-Basin; landforms-; last-glacial-maximum; lower-Holocene; Malay-Archipelago; Nile-River; paleoclimatology-; paleoenvironment-; paleofloods-; paleohydrology-; Pleistocene-; Quaternary-; sedimentation-; sediments-; semi-arid-environment; Sierra-Leone; South-America; streamflow-; sub-humid-environment; textures-; upper-Pleistocene; West-Africa

CC - CATEGORY CODES: 24-Quaternary-geology

DT - DOCUMENT TYPE: Serial; Conference-Document

BL - BIB LEVEL: Analytic

IL - ILLUSTRATION: Refs: 85; illus. incl. 2 tables.

RF - REFERENCE SOURCE: GeoRef, Copyright 2000, American Geological Institute.

IS - ISSN: 0305-8719

IB - ISBN: 1-897799-69-1

AN - ACCESSION NUMBER: 1997-062657

UD - UPDATE CODE: 199720

Registro 4734 de 5614 - GeoRef Disc 4: 1993-1996

TI - TITLE: Caracterizacion y estudio reologico de una bentonita colombiana

Translated Title: Characterization and rheology of a Colombian bentonite.

AU - AUTHORS: Pinzo-Bello-J-A; Requena-Balmaseda-J

AF - AUTHOR AFFILIATION: Univ. Nac. Colombia, Santafe de Bogota, Colombia

SO - SOURCE: Boletin de la Sociedad Espanola de Ceramica y Vidrio. 35; 5, Pages 337-344. 1996.

PB - PUBLISHER: Sociedad Espanola de Ceramica y Vidrio. Arganda del Rey (Madrid), Spain. 1996.

CP - COUNTRY OF PUBLICATION: Spain

PY - PUBLICATION YEAR: 1996

LA - LANGUAGE: Spanish

LS - LANGUAGE OF SUMMARY: English

DE - DESCRIPTORS: bentonite-; chemical-composition; clastic-rocks; clay-mineralogy; clay-minerals; Colombia-; differential-thermal-analysis; granulometry-; montmorillonite-; rheology-; sedimentary-rocks; sheet-silicates; silicates-; South-America; thermal-analysis; thermogravimetric-analysis; viscosity-; X-ray-analysis; X-ray-diffraction-analysis

CC - CATEGORY CODES: 01B-Mineralogy-of-silicates

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

IL - ILLUSTRATION: Refs: 14; 2 tables, 1 anal.

RF - REFERENCE SOURCE: GeoRef, Copyright 2000, American Geological Institute. Reference includes data from GEOMINER, Instituto Technologico GeoMineral de Espana, Madrid, Spain

IS - ISSN: 0366-3175

AN - ACCESSION NUMBER: 1997-066171

UD - UPDATE CODE: 199722

Registro 4735 de 5614 - GeoRef Disc 4: 1993-1996

TI - TITLE: Utilizacion del mercurio en la pequena mineria del oro

Translated Title: Utilization of mercury in small scale gold mining.

AU - AUTHORS: Pantoja-Timaran-F

AF - AUTHOR AFFILIATION: Univ. Kosice, Kosice, Slovak Republic

SO - SOURCE: Ingeopres. 42; Pages 32-36. 1996.

PB - PUBLISHER: Entorno Grafico. Madrid, Spain. 1996.

CP - COUNTRY OF PUBLICATION: Spain

PY - PUBLICATION YEAR: 1996

LA - LANGUAGE: Spanish

DE - DESCRIPTORS: Colombia-; conservation-; gold-ores; mercury-ores; metal-ores; mining-; mining-geology; pollution-; recovery-; South-America; utilization-

CC - CATEGORY CODES: 22-Environmental-geology; 27A-Economic-geology,-geology-of-ore-deposits

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

IL - ILLUSTRATION: Refs: 3; 3 plates.

RF - REFERENCE SOURCE: GeoRef, Copyright 2000, American Geological Institute. Reference includes data from GEOMINER, Instituto Technologico GeoMineral de Espana, Madrid, Spain

IS - ISSN: 1136-4785

CO - CODEN: #53452

AN - ACCESSION NUMBER: 1997-066187

UD - UPDATE CODE: 199722

Registro 4736 de 5614 - GeoRef Disc 4: 1993-1996

TI - TITLE: High-resolution sequence stratigraphy of continental strata; a surface-subsurface integration case study, middle Magdalena Basin, Colombia.

AU - AUTHORS: Ramon-Juan-Carlos; Cross-Timothy-A

AF - AUTHOR AFFILIATION: Colorado School of Mines, Department of Geology and Geological Engineering, Golden, CO, United States

BK - BOOK TITLE: In: Geological Society of America, 28th annual meeting.

BA - BOOK AUTHORS: Anonymous

SO - SOURCE: Abstracts with Programs - Geological Society of America. 28; 7, Pages 523-524. 1996.

PB - PUBLISHER: Geological Society of America (GSA). Boulder, CO, United States. 1996.

CP - COUNTRY OF PUBLICATION: United-States

PY - PUBLICATION YEAR: 1996

CN - CONFERENCE INFORMATION: Geological Society of America, 28th annual meeting. Denver, CO, United States. Oct. 28-31, 1996.

LA - LANGUAGE: English

AB - ABSTRACT: A 3-km-thick section of Lower Tertiary continental strata in the Middle Magdalena Basin, Colombia, usually is divided into 4 lithostratigraphic units (formations or operational units). We present an alternative division of these strata into 15 intermediate-scale, 70 to 250-m-thick, chronostratigraphic units interpreted from 1000 m of core, 500 m of outcrop sections (including scintillation profiles), 40 well logs and multiple seismic reflection profiles. These units were defined by stacking patterns and facies successions of small-scale chronostratigraphic units, and each contains multiple facies tracts comprising different facies assemblages and facies succesions. The 15 units were grouped into 8 larger scale chronostratigraphic units which were correlated across the basin in the well-log grid and which were comparable to seismic stratigraphic units resolved on seismic reflection profiles. Division into chronostratigraphic units is the basis for more accurate and higher resolution stratigraphic correlations in the basin, and more accurate representation of facies distributions and juxtapositions within time-bounded stratigrapic units. Several regular, recurring motifs of facies successions were recognized in core from all facies tracts (preserved remnants of depositional environments): channel-splay-lake; splay-wet floodplain-lake-aggradational soil; lake-splay-crevasse channel; channel-lake-soil; channel-splay-lake-soil. These facies succession motifs define symmetric and asymmetric stratigraphic cycles which record stratigraphic base-level cycles. A base-level cycle is a time of unidirectional increase and then decrease of the accommodation/sediment supply (A/S) ratio. These unidirectional trends of increasing and decreasing A/S are recorded by: large-scale stratigraphic geometries; stratigraphic architecture; facies associations, successions and diversity; cycle symmetry; degree of preservation of original geomorphic elements; and petrophysical properties. The turnaround points from base-level fall to base-level rise, and from rise to fall, are the basis for correlation across facies tracts of stratigraphic cycles of all scales. Stacking patterns, long-term changes in facies succession motif, thickness and symmetry changes of a small-scale cycles are used to erect longer term stratigraphic cycles.

DE - DESCRIPTORS: Cenozoic-; chronostratigraphy-; Colombia-; cycles-; depositional-environment; geometry-; geophysical-profiles; high-resolution-methods; lacustrine-environment; levels-; lithostratigraphy-; lower-Tertiary; Middle-Magdalena-Basin; seismic-profiles; sequence-stratigraphy; soils-; South-America; Tertiary-; thickness-

CC - CATEGORY CODES: 12-Stratigraphy

DT - DOCUMENT TYPE: Abstract; Serial; Conference-Document

BL - BIB LEVEL: Analytic

RF - REFERENCE SOURCE: GeoRef, Copyright 2000, American Geological Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States

IS - ISSN: 0016-7592

CO - CODEN: GAAPBC

AN - ACCESSION NUMBER: 1997-066343

UD - UPDATE CODE: 199722

Registro 4737 de 5614 - GeoRef Disc 4: 1993-1996

TI - TITLE: Climate change in South America during the period of the K-T boundary evidenced by delta-13-C values of organic-rich Colombian sediments.

AU - AUTHORS: Jahren-A-Hope; Arens-Nan-Crystal; Amundson-Ronald-G

AF - AUTHOR AFFILIATION: University of California at Berkeley, Ecosystem Sciences Division, Berkeley, CA, United States

BK - BOOK TITLE: In: Geological Society of America, 28th annual meeting.

BA - BOOK AUTHORS: Anonymous

SO - SOURCE: Abstracts with Programs - Geological Society of America. 28; 7, Pages 224. 1996.

PB - PUBLISHER: Geological Society of America (GSA). Boulder, CO, United States. 1996.

CP - COUNTRY OF PUBLICATION: United-States

PY - PUBLICATION YEAR: 1996

CN - CONFERENCE INFORMATION: Geological Society of America, 28th annual meeting. Denver, CO, United States. Oct. 28-31, 1996.

LA - LANGUAGE: English

AB - ABSTRACT: We report the stable isotope composition of organic carbon in a sequence of Cretaceous and Tertiary siltstone and mudstone from Cundinamarca and Boyaca, Colombia. Samples of organic-rich siltstone and mudstone were collected throughout five sedimentary formations within a 150-km radius. These sediments formed in a wet-terrestrial environment, such as a lagoon, swamp or slow stream. The formations span the Upper portion of the Lower Cretaceous to the Lowermost Paleocene, including a Cretaceous-Tertiary (K-T) boundary-crossing section of geologic time. Values obtained from stable carbon isotope combustion analysis [average delta-13-C(PDB)] are the following: Las Juntas Lower Cretaceous (124-131 Ma) -23.4 per mil n = 9; Fomeque Lower Cretaceous (113-124 Ma) -22.7 per mil n = 6; Une Middle Cretaceous (97.5-119 Ma) -21.8 per mil n = 6; Chipaque Middle Cretaceous (88.5-97.5 Ma) -23.7 per mil n = 1; Guaduas K-T boundary (63.6-74.5 Ma) -25.1 per mil n = 13, where n = the number of distinct samples along a stratigraphic time-line. The Guaduas formation, which is terrestrial in depositional environment, is between 1.4 and 3.3 per mil isotopically lighter in stable carbon than other formations of the Cretaceous. The difference between the delta-13-C value of the Chipaque formation and that of the Guaduas implies a shift of 1.4 per mil to more negative values during the period of the K-T boundary; this is comparable with the -1.8 per mil shift in the delta-13-C value of organic carbon in a sequence of sediment found in North America (Schimmelmann and DeNiro, 1984). We will present the data graphically, including all variation, and discuss the implications of these results and their bearing upon theories concerning global geochemical disturbance at the K-T boundary. Cited: Schimmelmann, A. and M. J. DeNiro (1984). Earth and Planet. Sci., 68:392-398.