Sedimentary organic matter maturation stages

The evolution of sedimentary organic matter (OM) under the influence of increasing burial depth and related temperature rise is termed maturation and this process is commonly subdivided into three stages, i.e., diagenegisis, catagenesis, and metagenesis (Figure 1). 

Thermal maturation The alteration of sedimentary organic matter by the effects of heating. Maturation implies that the altered OM reaches a stage where its thermal breakdown will produce liquid or gaseous hydrocarbons. 

Higher temperatures are characteristic of the sedimentary section of the Akfadou area as compared to the Takhoukht area. Temperatures of about 120 °C were reached in Early Devonian sediments. Our model calculations for the end of the Early Carboniferous (about 330 Ma), and before the Hercynian uplift and erosion, give temperatures and maturation levels for the Ordovician, Silurian, and Early Devonian shales consistent with early to main stages of hydrocarbon generation (Table 6.6). Toward the close of the Carboniferous (about 289 Ma), the sapropelic and humic organic matter of the Ordovician, Silurian, and probably Devonian source shales was sufficiently mature to generate both liquid and gaseous hydrocarbons. Silurian and Devonian shales in other areas of the basin are also characterized by considerable potential... 

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