| Summary: | Upper Cretaceous pelitic rocks generate most of the oil reserves in Colombia. In Del Magdalena Upper Valley (MUV), the existenceof good quality outcrops and thermal evolution levels that vary from immaturity to the end of the oil generation “window” makes it one of themost appropriate regions for the study of primary migration and generation of oil in Upper Cretaceous. The main objectives of this work wereto study the organic facies of La Luna Formation in an outcrop section called Riacho Bambuca (Bambuca Creek), determine the oil generationpotential and characterize the paleoenvironment. For this research, 24 samples were used in palynofacies analysis (characterization ofthe kerogen components assembly) and in organic geochemistry analysis (Total Organic Carbon – TOC analysis and Rock-Eval pyrolysis,provided by Colombia Oil Institute – ECOPETROL). The palynofacies analysis included the use of microscopy techniques (transmitted whitelight and incident blue light). Furthermore, a Spore Coloration Index (SCI) analysis was made in order to determine the thermal maturationstage. The studied material was composed mainly of an amorphous organic substance, with its fluorescent coloration varying from yellow tobright orange. The palynomorph group is represented by spore morph and dinoflagellate cysts. The ligneous material are present in very lowpercentages; they are mainly opaque phytoclasts. The results of geochemical analysis showed TOC contents ranging from medium to high,excellent potential for the generation of hydrocarbons (PG > 4 mg HC/g of rock), hydrogen index ranging from 329 to 589 mg HC/g, andlow values of oxygen index, characterizing type II kerogen. The low degree of thermal maturation was determined by Spore Coloration Indexvalues ranging from 2,5 to 3,0, Tmax values below 440°C and Hydrocarbon Production Index inferior to 0,2. According to the organic faciesdata, La Luna Formation deposited in a marine environment with facies from disoxic-anoxic distal shelf and suboxic-oxic distal basin; therewas kerogen of excellent quality, and its quantity was adequate for the generation of oil.Keywords: Organic facies; La Luna Formation; Cretaceous; Colombia
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