During the Late Devonian the South American Platform suffered marine transgressions that
determined the accumulation of dark black-gray shales with high content of organic matter, of
marine origin and in anoxic conditions, associated to the Barreirinha Formation. The
paleoenvironment and potential generator was determined from outcrops in the municipality of
Rurópolis, Pará, identifying five sedimentary facies grouped in the associations of facies of Deep
platform (AF1) and Deep-transitional platform (AF2). These associations indicate the
consequences of the Upper Devonian Transgression occurred in the Gondwana. AF1 presents TOC
levels <3.23%, indicating a high to very high potential generator, while AF2 recorded TOC values
<1%, corresponding to a potential for low to medium hydrocarbons. According to the Rock Eval
pyrolysis data, the Hydrogen Index (IH) shows both values lower than 200 mg HC / g of TOC,
associated to the generation of gas, attributed to AF2, as values between 200 and 300 mg HC / g
of COT for AF1, corresponding to a potential for gas and condensate. Values of Tmax <440 ° C
indicate a stage of immature thermal evolution, while the kerogen is type II and III, associated with
a marine and continental origin, respectively. The biomarkers present a bimodal distribution of nalkanes
(C11-C35), suggesting organic matter deposited in a predominantly marine environment,
but with contribution of material derived from higher plants, corroborated by TAR, C27 / C29,
Hopano/Esterano and MPI- 1. While the CPI, EPO, Pr / n-C17 and F / n-C18 values indicate a low
thermal evolution during an immature stage. This fact is corroborated by the Ts / Tm, Ts / (Ts +
Tm) and the homohopane index, C35 / C31. Therefore, the organic matter is derived from planctonic
organisms and / or seaweed, and to a lesser extent, according to the C27 / C29 ratio of the sterols,
derived from higher plants. The generation of hydrocarbons in AF1 is high to very high, mainly
for gas and condensate, being the result of the influence of diabase sills that modified the conditions
of pressure and temperature to advance with the cracking of organic matter during the Triassic-
Jurassic periods.
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