RF - REFERENCE SOURCE: GeoRef, Copyright 2000, American Geological Institute.
IS - ISSN: 0895-0695
CO - CODEN: EAQNAT
AN - ACCESSION NUMBER: 1994-048018
UD - UPDATE CODE: 199422
Registro 3541 de 5614 - GeoRef Disc 3: 1985-1992
TI - TITLE: Contribution de l'etude des phases fluides et de la geochimie isotopique (super 18) O/ (super 16) O, (super 13) C/ (super 12) C a la genese des gisements d'emeraude de la Cordillere orientale de la Colombie
Translated Title: Fluid phase and (super 18) O/ (super 16) O, (super 13) C/ (super 12) C isotopic geochemistry contribution to the genesis of emerald deposits in the Eastern Cordillera of Colombia.
AU - AUTHORS: Giuliani-G; Sheppard-S-M-F; Cheilletz-A; Rodriguez-C
AF - AUTHOR AFFILIATION: CNRS, ORSTOM, Vandoeuvre-les-Nancy, France
SO - SOURCE: Comptes Rendus de l'Academie des Sciences, Serie 2, Mecanique, Physique, Chimie, Sciences de l'Univers, Sciences de la Terre. 314; 3, Pages 269-274. 1992.
PB - PUBLISHER: Gauthier-Villars. Montrouge, France. 1992.
RF - REFERENCE SOURCE: GeoRef, Copyright 2000, American Geological Institute. Reference includes data from PASCAL, Institute de l'Information Scientifique et Technique, Vandoeuvre-les-Nancy, France
CO - CODEN: IGABBY
AN - ACCESSION NUMBER: 1995-028975
UD - UPDATE CODE: 199511
Registro 3545 de 5614 - GeoRef Disc 3: 1985-1992
BK - BOOK TITLE: Stable isotopic records of venerid bivalve shells; environmental information from the eastern Pacific Ocean and southern Caribbean Sea.
BA - BOOK AUTHORS: Bemis-Bryan-Edward
CP - COUNTRY OF PUBLICATION: United-States
PY - PUBLICATION YEAR: 1992
DG - DEGREE GRANTED: Master's
DI - DEGREE GRANTING INSTITUTION: University of Wisconsin-Madison. Madison, WI, United States. 1992.
LA - LANGUAGE: English
AB - ABSTRACT: Stable isotopic records of venerid bivalve shells from several hydrographically distinct environments in the eastern Pacific Ocean and southern Caribbean Sea appear to record the hydrographic conditions of these regions. Oxygen isotopic profiles reflect the bathymetric distributions and annual variations of temperature and salinity in these regions, whereas carbon isotopic profiles offer information that is as yet uninterpretable concerning specific environmental conditions in the study area. Higher delta (super 18) O maxima and minima generally occur in the isotopic records of shells that lived in deeper waters. This pattern may be useful as an indicator of relative depth of habitat in fossil venerid bivalves. Differences in maxima and minima among depths are pronounced in Pacific shells due to large vertical gradients of temperature and salinity in Pacific environments. Shells of Chione kellettii from progressively deeper habitats in Parita Bay of the eastern Pacific Gulf of Panama exhibit increases in delta (super 18) O maxima from -1.6 per mil at 20 m depth to -0.8 per mil at 33 m and -0.1 per mil at 45 m. Minimum delta (super 18) O from these shells are -3.4 per mil, -2.6 per mil, and -1.7 per mil, respectively. Maximum delta (super 18) O of shells from the vicinity of the Pearl Islands in the Gulf of Panama increases between less than 10 m (-1.0 per mil) and 99 m (0.7 per mil), and minimum delta (super 18) O increase from -3.2 per mil to -2.4 per mil over the depth interval. Caribbean shells exhibit weaker trends in delta (super 18) O maxima and minima than do Pacific shells, due to smaller bathymetric gradients of temperature and salinity in Caribbean environments. Shells from coastal waters of northern Panama and northwestern Colombia exhibit increases in delta (super 18) O maxima over depth intervals of less than 10 m (-1.5 per mil) to 24 m (-1.4 per mil to 47 m (-1.3 per mil), and minimum 5180 values in the shells from these depths are -2.5 per mil, -2.1 per mil, and -2.0 per mil, respectively. In a shell from 68 m, delta (super 18) O maximum and minimum values are -1.6 per mil and -2.4 per mil, ending the trend for shallower depths. Shells from coastal waters of northeastern Colombia and northern Venezuela exhibit an increase in delta (super 18) O maxima from 16 m (- 0.8 per mil) to 27 m (-0.7 per mil) to 55 m (0.2 per mil). Minimum delta (super 18) O does not exhibit a consistent pattern with depth, but does suggest a tendency toward lower values in deeper environments: -2.2 per mil at 16 m, -2.5 per mil at 27 m, and -2.4 per mil at 55 m. In contrast with findings relating to bivalves from temperate waters, the magnitude of shell delta (super 18) O range does not exhibit a clear and consistent directional trend with depth, and is therefore not a reliable depth indicator in these tropical environments. A weak decrease in delta (super 18) O ranges of shells from Parita Bay, from 20 and 33 m (1.8 per mil) to 45 m (1.6 per mil), is opposite the pattern of increasing ranges from less than 10 m (2.2 per mil) to 99 m (3.1 per mil) near the Pearl Islands. Shells from northern Panama and northwestern Colombia record a general decrease in delta (super 18) O range from less than 10 m (1.0 per mil) to 24 and 47 m (0.7 per mil), and a subsequent increase at 68 m (0.8 per mil). A strong trend of increasing delta (super 18) O range occurs in shells from northeastern Colombia and northern Venezuela: 1.4 per mil at 16 m, 1.8 per mil at 27 m, and 2.6 per mil at 55 m. Ranges of shell delta (super 18) O seem to distinguish the annual ranges and interactions of temperature and salinity characteristic of environments within the eastern Pacific and southern Caribbean. Generally, annual growth cycles are more pronounced and delta (super 18) O ranges are greater in Pacific shells, relative to those from Caribbean environments. These patterns may represent a potentially useful tool for reconstructing paleoenvironments of the Isthmus of Panama. At less than 10 m depth, shell delta (super 18) O range is greatest in the Gulf of Panama (2.2 per mil), which exhibits large variations of temperature and salinity and an inverse seasonal temperature-salinity correlation. Temperature and salinity vary less in the Gulf of Chiriqui (1.6 per mil), where temperature and salinity exhibit a roughly positive correlation, and in the coastal waters off the northern coast of Panama (1.0 per mil), where temperature and salinity are not correlated. At 16-24 m depth, shell delta (super 18) O ranges are largest in the Gulf of Panama (3.0 per mil and 2.8 per mil), followed by ranges from the upwelling region off northern Colombia (1.4 per mil) and a non-upwelling area off northern Panama (0.7 per mil). Parita Bay has large and inversely correlated temperature and salinity variations, whereas the other regions have consecutively smaller variations of temperature and salinity that are not correlated. Shell delta (super 18) O ranges from depths of 27-33 m in the Gulf of Panama and the upwelling area off northern Colombia are both 1.8 per mil, indicating similar hydrographic conditions at comparable depths in each environment. At 45-55 m depth, shell delta (super 18) O ranges from northern Venezuela, the Gulf of Panama, and northern Panama are 2.6 per mil, 0.9 per mil, and 0.7 per mil, respectively, illustrating the hierarchy of environmental variability in these environments. The shell delta (super 18) O range from 99 m in the Gulf of Panama is larger than that from 70 m depth in a non-upwelling environment off northern Colombia due to large annual temperature and salinity variations and an inverse temperature-salinity correlation. Carbon isotopic profiles offer much information about an organism and its environment, but interactions of environmental and biological influences are not well understood and difficult to interpret at the present time. Variations in delta (super 13) C may primarily reflect seasonal effects of temperature, freshwater mixing, and phytoplankton productivity, or they may record the significant contributions of biological effects. Cyclic variations in delta (super 13) C tend to be more pronounced in Pacific shells relative to Caribbean individuals, and Caribbean shells from depths of less than 70 m characteristically exhibit greater delta (super 13) C ranges than do Pacific shells from comparable depths. Several Pacific and Caribbean shells exhibit apparent ontogenetic increases or decreases in delta (super 13) C.