Organic and isotope geochemistry of the Early Cretaceous rift sequence in the Camamu Basin, Brazil: paleolimnological inferences and source rock models

Gonçalves, Fernando do Nascimento

doi:10.1016/s0146-6380(01)00128-0

Cited by 70 publications

(18 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…2007). Molecular parameters of the oil shale in the Songliao Basin are similar to Cretaceous lacustrine source rocks in Brazil (Gonçalves 2002). However, the latter mainly originated from algae and bacteria.…”

Section: Discussionmentioning

confidence: 81%

“…Although the n ‐alkane distribution of some non‐emergent vascular plants commonly maximizes at C 21 , C 23 , or C 25 (Ficken et al . 2000), a dominance of n ‐alkane around n ‐C 23 also indicates input of lipid‐rich algal and/or bacterial biomass (Gonçalves 2002). Thus, a maximum at n ‐C 23 in black shales and oil shales of the K 2 n 1 and K 2 n 2 can be interpreted as indication of mixed algal–herbaceous matter input, whereas a maximum at n ‐C 29 in mudstones of the K 2 n 1 and K 2 n 2 suggests a dominant input from higher plants.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Late Cretaceous paleoenvironment and lake level fluctuation in the Songliao Basin, northeastern China

Wan

Jansa

et al. 2011

Island Arc

View full text Add to dashboard Cite

Study of Late Cretaceous lacustrine sedimentary strata in the eastern Songliao Basin, China revealed that the paleoclimate was relatively arid and hot during sedimentation of the upper Santonian of the Yaojia Formation, but became relatively humid and warm during deposition of the lower Campanian Nenjiang Formation. The upper Yaojia Formation was deposited in a freshwater lake environment, while the lower Nenjiang Formation was deposited in a slightly brackish to brackish environment. The average total organic carbon content in the upper Yaojia Formation is 0.15%, while the hydrogen index is 36 mg HC /g TOC , implying poor source rock for oil generation and the organic matter comprised of a mixture of woody and herbaceous organic matter. In contrast, the hydrogen index of oil shale and black shale of the lower Nenjiang Formation is 619 mg HC /g TOC , and total organic carbon content on average is 3.37%, indicating a mixed algae and herbaceous source of kerogen and an increase in aquatic bioproductivity. The black shale and oil shale have low Pristane/Phytane and C 29 5a,14a,17a(H) -stigmastane 20R/(20R + 20S) ratios, with maximum concentration of n-alkanes at n-C 23 , implying an anoxic depositional environment with algae, bacteria and higher plants providing most of the organic matter. Relatively abundant gammacerane and a higher Sr/Ba ratio in the oil shales suggest the presence of brackish water and development of salinity stratification in the lake. During sedimentation of the upper Yaojia through the lower Nenjiang Formations, the level of Songliao lake increased and a deep-lake environment was formed with bottom waters being oxygen depleted. Concomitantly, as the lake deepened bottom conditions were changing from oxic to anoxic, and the input of organic matter changed from predominantly higher plants to a mixture of bacteria, algae and higher plants providing favorable conditions for oil source rock accumulation.

show abstract

Section: Discussionmentioning

confidence: 81%

Section: Resultsmentioning

confidence: 99%

Late Cretaceous paleoenvironment and lake level fluctuation in the Songliao Basin, northeastern China

Wan

Jansa

et al. 2011

Island Arc

View full text Add to dashboard Cite

show abstract

“…Lake deposits are influenced by tectonics and climate coequally, and the relative balance of tectonic induced potential accommodation with climate induced sediment and water fill control lake occurrence, distribution, and character (Carroll & Bohacs, ; Hao, Zhou, Zhu, & Yang, ). Relatively small size of water reservoirs in lakes results in wider ranges of salinity, pH and redox conditions, and marked variation of biota than in marine systems (Kelts, ; Valero Garcés, Kelts, & Ito, ; Gonçalves, ; Hao et al, ). Therefore, to clarify the organic matter accumulation mechanism in a lacustrine rift basin, it is important to characterize organic matter sources, depositional paleoenvironment, and water column properties.…”

Section: Introductionmentioning

confidence: 99%

Geochemical characteristics, depositional environment, and controlling factors of Lower Cretaceous shales in Chagan Sag, Yingen‐Ejinaqi Basin

et al. 2017

View full text Add to dashboard Cite

The Lower Cretaceous shales of Chagan Sag, Yingen‐Ejinaqi Basin, are considered as the source rocks of hydrocarbons discovered in the sag. Borehole shales from the Lower Cretaceous were subjected to comprehensive geochemical study to evaluate the quality of source rock, to reconstruct the paleodepositional environment and to determine the controlling factors of organic matter enrichment. Content of present‐day total organic carbon, and hydrogen index, averaging 1.4% and 259.2 mg hydrocarbon/g total organic carbon, respectively reveal poor to fair quality of organic matter. Average value of vitrinite reflectance (Ro) of 1.0% indicates mature organic matter. Maceral composition and biomarker analysis provide evidence for a mixed aquatic and terrigeous organic matter input. Based on Sr/Cu, Sr/Ba, and gammacerane index, we propose that organic matter was deposited in closed hypersaline under hot and arid climate conditions. The ratios of V/(V + Ni), and pristane/phytane (Pr/Ph), as well as the presence of β‐carotene suggest a stratified water column with anoxic bottom water condition. Low to moderate productivity as a result of deficient nutrient supply, the excellent organic matter preservation condition under stratified anoxic water column and high sedimentary rate controlled the quality of source rock. In addition, influence of factors such as content of clay minerals on organic matter enrichment cannot be ignored.

show abstract

“…Studies of Lower Cretaceous rift lake deposits in West Africa and Brazil identify organic productivity as a critical factor in deposition of the richest hydrocarbon source rocks, which average 6% total organic carbon (TOC) and contain up to 38% TOC (Gonçalves, 2002;Harris et al, 2004Harris et al, , 2005. The lower rift section, which is relatively lean, is associated with active faulting.…”

Section: Introductionmentioning

confidence: 99%

Soils, slopes and source rocks: Application of a soil chemistry model to nutrient delivery to rift lakes

Harris

Tucker

2015

Sedimentary Geology

View full text Add to dashboard Cite

Organic and isotope geochemistry of the Early Cretaceous rift sequence in the Camamu Basin, Brazil: paleolimnological inferences and source rock models

Cited by 70 publications

References 20 publications

Late Cretaceous paleoenvironment and lake level fluctuation in the Songliao Basin, northeastern China

Late Cretaceous paleoenvironment and lake level fluctuation in the Songliao Basin, northeastern China

Geochemical characteristics, depositional environment, and controlling factors of Lower Cretaceous shales in Chagan Sag, Yingen‐Ejinaqi Basin

Soils, slopes and source rocks: Application of a soil chemistry model to nutrient delivery to rift lakes

Contact Info

Product

Resources

About