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ESTUDIO DIAGENÉTICO PRELIMINAR DE LA FORMACIÓN AMAGÁ

2007; Industrial University of Santander; Volume: 29; Issue: 1 Linguagem: Espanhol

2145-8553

Cristina López,

Geological and Geophysical Studies Worldwide

RESUMEN A partir del estudio de seciones delgadas se hace una aproximacion a la diagenesis de la Formacion Amaga (Oligocena Superior- Miocena Inferior), aflorante en el suroeste de Antioquia. La paragenesis diagenetica para las areas Amaga-Angelopolis y Amaga-Palomos es similar. Inicialmente se presenta deformacion mecanica de micas y probablemente caolinitizacion de feldespatos; en la segunda area hay tambien cloritizacion de micas. La cementacion se dio relativamente temprana correspondiendo a cementos peliculares de clorita y hematita y cemento siliceo de poros seguidos por cementos carbonatados de poros y basales. A continuacion se produce la corrosion y diferentes tipos de metasomatismo seguidos por procesos neomorficos. Probablemente siguen pigmentos de oxidos de hierro y disolucion de cementos carbonatados que genera porosidad secundaria, la cual despues es destruida aisladamente por cementos siliceos y carbonatados. En el area de Fredonia-Venecia la compactacion jugo un papel mas notorio, como consecuencia la importancia de los cementos y del metasomatismo asociado, decrece. En la eogenesis priman condiciones anoxicas en las que los carbonatos se encuentran en la zona Me. La mesogenesis correspondio inicialmente a aguas meteoricas, de bajo pH; en estados mas tardios los carbonatos entran en la zona D, iniciandose abundante precipitacion de cementos. En la telogenesis se tienen condiciones alcalinas y oxidantes. Se infiere en general una variacion en los regimenes hidrogeologicos pasando de aguas meteoricas a compactacionales y posiblemente termobaricas. Palabras clave: Formacion Amaga; paragenesis diagenetica; etapas diageneticas; regimenes hidrologicos PRELIMINARY DIAGENETIC STUDY OF THE AMAGA FORMATION ABSTRACT By means of a thin sections analysis is made.a first approach of the diagenesis of the Amaga Formation (upper oligocenelower miocene) that outcrops in the southwest of Antioquia The diagenetic paragenesis of the Amaga-Angelopolis and Amaga-Palomos areas are similar. Initially, mechanical deformation of micas and probably kaolinitization of feldspars occur; in the second area there is too chloritization of micas. Cementation was relatively early corresponding to chlorite and hematite coats and siliceous pore cement followed by carbonate basal and pore cements. Later, corrosion and different types of methasomatism take place followed by neomorphic processes. Probably the next processes are pigmentation by Fe oxides and dissolution of carbonate cements that originates secondary porosity it which is isolately destroyed by siliceous and carbonate cements. In the Fredonia-Venecia area, compaction plays a more notorious role, as a consequence the importance of cements and associated methasomatism, decrease. In eogenesis, prevail anoxic conditions and the carbonates are in the Zone Me. Mesogenesis initially corresponds to low pH metheoric waters; in later stages the carbonates enter in the zone D beginning an abundant precipitation of cements. In telogenesis exist alkaline and oxic conditions. A transition in the hydrologic regimes can be infered passing from metheoric to compactional and possibly thermobaric waters. Key words: Amaga Formation; diagenetic paragenesis; diagenetic stages; hydrologic regimes.