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The distribution of organic facies is a function of the environment of deposition. Within each turbidite facies, diverse depositional regimes are present that affect both the preservation and dispersal of organic matter. Proper identification of turbidite facies can lead to a proper prediction of organic content within a particular turbidite facies or turbidite facies association.
The type section of the Brown's Point formation, a turbidite sequence within the Hoh rock assemblage, demonstrates the correlation between organic facies and turbidite facies, as defined by E. Mutti and F. Ricci-Lucchi. Turbidite facies can be matched to organic facies throughout the entire 4,000 ft (1220 m) thick vertical section. Outer and middle fan turbidite associations have been analyzed and correlated for organic facies lateral continuity.
Distribution of organic carbon concentrations and organic carbon types suggests a dominance of terrestrial input. TAI and Ro analyses reflect a marginally mature thermal maturation level (Ro = 0.5-0.6). Visual kerogen inspection reveals a mixed to structured kerogen with a predominance of type III/IV over type IV kerogen. Overall, maturation indices suggest a gas source with poor source potential for oil. Individual turbidite facies display a significant relationship to the amount, type, and level of maturation of organic matter present within each facies and facies association.
Frontier basin analysis of turbidite sequences can be expedited by proper field identification of turbidite facies and subsequent geochemical analysis of the content, type, and maturation level of the organic matter present within each turbidite facies.
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