Biomarkers in Cretaceous sedimentary rocks from the Codó Formation - Parnaíba Basin: Paleoenvironmental assessment

Earlier geological works showed that Codó Formation - CF (Parnaíba Basin, Brazil) has been deposited in the Aptian, and suffered the influence of various transgressive-regressive marine cycles, thus suggesting various depositional environment possibilities from saline lacustrine deltaic to shallow m...

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Bibliographic Details
Published in:	Journal of South American earth sciences Vol. 92; pp. 265 - 281
Main Authors:	da S. Sousa, Edymilaís, Júnior, Gustavo R.Sousa, Silva, Andrenilton F., de A. M. Reis, Francisco, de Sousa, Alek A.C., Cioccari, Giovani M., Capilla, Ramsés, de Souza, Igor V.A.F., Imamura, Paulo M., Rodrigues, Rene, Lopes, José A.D., de Lima, Sidney G.
Format:	Journal Article
Language:	English
Published:	Elsevier Ltd 01-06-2019
Subjects:	4-Methylstigmastane Depositional environment Dinosterane Hopenes Sterenes Depositional environment Dinosterane Hopenes 4-Methylstigmastane Sterenes
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Summary:	Earlier geological works showed that Codó Formation - CF (Parnaíba Basin, Brazil) has been deposited in the Aptian, and suffered the influence of various transgressive-regressive marine cycles, thus suggesting various depositional environment possibilities from saline lacustrine deltaic to shallow marine during sedimentation. Cretaceous potential source rock samples from the CF were investigated to identify diagnostic biomarkers in order to ascertain paleoenvironmental conditions of deposition and thermal evolution of organic matter. The TOC results showed low organic matter (OM) contents and Rock-Eval analysis implying low thermal evolution of organic matter. GC-MS analysis showed a great diversity of biomarkers within the five studied samples. The main features of organic matter composition were: low content of n-alkanes, Ph » Pr, presence of i-25, i-30 (squalane) and gammacerane thus suggesting saline to hypersaline depositional environment. The biomarkers fingerprint showed a full series of ββ hopanes and Δ13(18) hopenes, αααR and βααR steranes, and Δ5 and Δ8(14) sterenes, pointing out immature OM. Several C30 steranes have been detected, among them 4α(methyl)- and 4β(methyl)-24-ethylcholestane, 24-n-propylcholestane and 24-isopropylcholestane (all identified by co-injection) and dinosteranes, which some of them are indicative of a marine depositional system. •Cretaceous potential source rock samples from the Codó Formation (Parnaíba Basin, Brazil).•C30 sterane biomarker: 24-n-propylcholestane and 24-isopropylcholestane.•Indicators of maturity and depositional paleoenvironment.•Evidences of anoxia during the deposition of sediments in Parnaíba Basin.
ISSN:	0895-9811 1873-0647
DOI:	10.1016/j.jsames.2019.03.025