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Abstract
By means of a thin sections analysis is made.a first approach of the diagenesis of the Amagá Formation (upper oligocenelower miocene) that outcrops in the southwest of Antioquia The diagenetic paragenesis of the Amagá-Angelópolis and Amagá-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: Amagá Formation; diagenetic paragenesis; diagenetic stages; hydrologic regimes.
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References
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