SEDIMENTACIÓN DEL MIOCENO SUPERIOR-PLIOCENO EN EL FLANCO NORANDINO DE LOS ANDES CENTRALES VENEZOLANOS
UPPER MIOCENE-PLIOCENE SEDIMENTATION IN THE NORTH FLANK OF VENEZUELAN CENTRAL ANDES
Omar Guerrero; Darcy Jiménez; Maria T. Monsalve y M. Alvarado
Recibido: 11-2-09; Aprobado: 3-3-09.
RESUMEN
La sedimentación del Mioceno Superior-Plioceno en el Flanco Norandino de Los Andes centrales de Venezuela corresponden con los depósitos de la Formación Betijoque, su evaluación sedimentaria se logró mediante la aplicación de técnicas metodológicas para estudio de ambientes fluviales, que toma en cuenta aspectos litoestratigráficos; caracterizando facies, articulando secuencias, estableciendo relaciones geométricas dentro de los cuerpos sedimentarios, por medio del estudio de los litosomas y elementos de arquitectura, lo que permitió establecer su significado sedimentológico y el modelo sedimentario. Los sedimentos de la Formación Betijoque se dividen en tres secuencias sedimentarias de sistemas fluviales desarrolladas dentro de abanicos aluviales progradantes que corresponden con los depositos molásicos de la orogénesis andina, como sigue; Secuencia I: caracterizada por barras y canales con acreción lateral, predominantemente arenosas y algunas gravas en la base de sus depósitos; que corresponden a facies de ríos meandriformes de arena, corresponde con la sección media-distal del abanico aluvial; Secuencia II: cuya característica más resaltante es el incremento en la granulometría de los sedimentos y la presencia de canales y barras de gravas que se identifican con ríos meandriformes de gravas y arenas, corresponde con la parte media l cuerpo del abanico aluvial y la Secuencia III: definida por el incremento en la fracción de los conglomerados que forman depósitos amalgamados típicos de ríos trenzados de gravas, que se relaciona con la media a proximal del abanico aluvial. La articulación vertical y lateral de las secuenciass antes mencionadas define una dinámica sedimentaria de abanicos aluviales en posiciones medios y dístales progradantes en climas subhumedos.
Palabras claves; Abanicos aluviales, Andes Venezolanos, Formación Betijoque, Mioceno Superior-Plioceno, Sedimentología de clásticos.
Abstract
The sedimentation of Upper Miocene-Pliocene in the North-Andean flank of the central Venezuelan Andes correspond
with Betijoque Formation deposits; their sedimentary evaluation was achieved by means of the application of field and laboratory methodological technics for study of fluvial environment that takes into account litoestratigrphics aspects; facies characterizing by means of determine: morphology, granulometry, lithology, color, among others facies elements, sequences articulating, establishing geometric relationships inside the sedimentary bodies, by means of the study of the litosomas and sedimentary architecture elements, what allowed to establish its sedimentological meaning and sedimentary pattern. Betijoque Formation's sediments are divided in three sedimentary sequences of developed fluvial systems inside progradating alluvial fans that correspond with molasics deposits of Andean orogenesis: Sequence I: characterized by bars and channels with lateral accretion, mainly sandy and some gravels in the base of their deposits that correspond to facieses of sand meandrous rivers, it corresponds with the med-end section of the alluvial fan; Sequence II: whose characteristic more resaltante is the increment in the grain of the silts and the presence of channels and bars of gravels that are identified with gravels and sands meandrous rivers, it corresponds with med part of alluvial fan body; Sequence III: defined by the increment in the fraction of the conglomerate that form typical amalgamated deposits of gravels braided rivers that is related with med to proximal part of alluvial fan. Vertical and lateral articulation of the before mentioned sequences defines a sedimentary dynamics of alluvial fans in med and end progradating positions in subhumid climates.
with Betijoque Formation deposits; their sedimentary evaluation was achieved by means of the application of field and laboratory methodological technics for study of fluvial environment that takes into account litoestratigrphics aspects; facies characterizing by means of determine: morphology, granulometry, lithology, color, among others facies elements, sequences articulating, establishing geometric relationships inside the sedimentary bodies, by means of the study of the litosomas and sedimentary architecture elements, what allowed to establish its sedimentological meaning and sedimentary pattern. Betijoque Formation's sediments are divided in three sedimentary sequences of developed fluvial systems inside progradating alluvial fans that correspond with molasics deposits of Andean orogenesis: Sequence I: characterized by bars and channels with lateral accretion, mainly sandy and some gravels in the base of their deposits that correspond to facieses of sand meandrous rivers, it corresponds with the med-end section of the alluvial fan; Sequence II: whose characteristic more resaltante is the increment in the grain of the silts and the presence of channels and bars of gravels that are identified with gravels and sands meandrous rivers, it corresponds with med part of alluvial fan body; Sequence III: defined by the increment in the fraction of the conglomerate that form typical amalgamated deposits of gravels braided rivers that is related with med to proximal part of alluvial fan. Vertical and lateral articulation of the before mentioned sequences defines a sedimentary dynamics of alluvial fans in med and end progradating positions in subhumid climates.
Keywords: Alluvial fans, Betijoque Formation, sedimentary architectural, Upper Miocene, Venezuelan Andes.
Facultad de Ingeniería, Grupo “Terra”-ULA. email:
oguerre@ula.ve; darcycjf@yahoo.es; mariatmonsalve@ula.ve; alvaradom@ula.ve
oguerre@ula.ve; darcycjf@yahoo.es; mariatmonsalve@ula.ve; alvaradom@ula.ve
GEOMINAS, Vol. 37, N° 48, abril 2009 27
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