A molecular isotopic study of 13C-enriched organic matter in evaporitic deposits: recognition of CO2-limited ecosystems

Schouten, Stefan; Hartgers, Walter A.; López, Jordi F.; Grimalt, Joan O.; Damsté, Jaap S Sinninghe

doi:10.1016/s0146-6380(00)00177-7

Cited by 58 publications

(57 citation statements)

References 31 publications

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“…and (e), the MTTC compounds have almost the same carbon isotope values as pristane and phytane, which is consistent with previous studies [11,13,14,28,29]. For example, the MTTC compounds in Miocene marl in the northern Appenines, Italy, were abnormally enriched with 13 C, and 13 C-enriched pristane, phytane and other photosynthetic primary producer derived biomarkers were also detected in these samples.…”

Section: Comparison Of Stable Carbon Isotope Compositions Of Mttc Comsupporting

confidence: 90%

“…As shown in Figure 5, the same carbon isotope values occur for the different carbon number MTTC compounds in each sample, usually with a difference of lower than 1‰. Similar phenomena have also been reported for MTTC compounds in other zones, such as in the oils sourced from the Jizhong Depression and the source rocks of the Jianghan Basin in China [11,13], the limestones of north Jura in France [14], the Miocene marl in the northern Appenines in Italy [28], and the Miocene/Pliocene sediments from the Sdom Formation, Dead Sea in Israel [29]. The similar carbon isotope values of the different carbon number MTTC compounds may indicate the same biological precursors for these compounds.…”

Section: Comparison Of Stable Carbon Isotope Compositions Of Mttc Comsupporting

confidence: 76%

“…The extremely high  13 C values of primary producer-derived biomarkers were interpreted to result from a localized CO 2 -limited ecosystem. Relatively low CO 2 concentration in a water body leads to the decreasing fractionation of 13 C in autotrophic organisms [28], resulting in the enrichment of 13 C in MTTC compounds and other primary producer-derived biomarkers. Therefore, results suggest that the MTTC compounds could be sourced from photosynthetic primary producers.…”

Section: Comparison Of Stable Carbon Isotope Compositions Of Mttc Commentioning

confidence: 99%

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Stable carbon isotope compositions of isoprenoid chromans in Cenozoic saline lacustrine source rocks from the Western Qaidam Basin, NW China: Source implications

et al. 2011

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Although the distribution of mono-, di-and trimethylated 2-methyl-2-(4,8,12-Trimethyltrideeyl) chromans (MTTCs) is well understood as an indicator of water salinity, their origin and formation mechanism are still ambiguous and under debate. In this paper, abnormally high levels of MTTCs were detected in Cenozoic saline lacustrine source rocks from the Western Qaidam Basin. Using a two-step column chromatography method, the MTTCs and naphthalenes were separated from other aromatic compounds and concentrated in one fraction, so that the stable carbon isotope compositions of these compounds could be accurately measured. Similar carbon isotope ratios for the mono-, di-and trimethylated 2-methyl-2-(4,8,12-Trimethyltrideeyl) chromans in a given sample suggest the MTTCs may share the same biological source(s). The MTTCs from the Western Qaidam Basin have similar carbon isotope compositions to primary producer-derived pristane and phytane. However, the  13 C values for the MTTCs showed significant differences with other primary producers-derived biomarkers (e.g. C 27 and C 29 steranes), probably indicating a distinct microalgae source from specific niches for the MTTC compounds. We speculate that the MTTCs distribution patterns may be controlled by the water chemistry dynamics in niches, which, in turn, is affected by hypersaline bottom water.

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Section: Comparison Of Stable Carbon Isotope Compositions Of Mttc Comsupporting

confidence: 90%

Section: Comparison Of Stable Carbon Isotope Compositions Of Mttc Comsupporting

confidence: 76%

Section: Comparison Of Stable Carbon Isotope Compositions Of Mttc Commentioning

confidence: 99%

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Stable carbon isotope compositions of isoprenoid chromans in Cenozoic saline lacustrine source rocks from the Western Qaidam Basin, NW China: Source implications

et al. 2011

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“…It generally has been accepted that the particular depositional environments and the high productivity of photosynthetic organisms present in saline lakes can cause a decrease in the amount of dissolved CO 2 available for photosynthesis. This further results in a decreased fractionation of 13 C during CO 2 assimilation [46,49,50]. The presence of 13 C-enriched C 25 HBI in the source rocks of the Western Qaidam Basin suggests that diatom blooms occurred in the ecosystem, which can induce a decrease of dissolved CO 2 available for photosynthesis.…”

Section: Significance Of C 25 Hbi Occurrence In Source Rocks Westernmentioning

confidence: 99%

The occurrence and significance of C25HBI in Cenozoic saline lacustrine source rocks from the Western Qaidam Basin, NW China

et al. 2011

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The saline lacustrine deposit of the Oligocene Lower Ganchaigou Formation is the main source rock for the Western Qaidam Basin, NW China. In this study, abundant highly branched isoprenoids with 25 carbon atoms (C 25 HBI) were detected in the upper section of the Lower Ganchaigou Formation. C 25 HBI is a biomarker for diatoms, and can provide information regarding biogeochemical processes during production and preservation of sedimentary organic matter. The carbon isotopic values of C 25 HBI in these source rocks were in the range of -18‰ to -20‰. The relative enrichment in 13 C of C 25 HBI suggests that these isoprenoids were derived from diatom blooms. In this case, the diatoms used HCO 3 -as an additional carbon source to dissolved CO 2 in water column due to their high biological productivity. Conversely, the diatom blooms indicated an abundant nutrient supply to the environment and high primary productivity. Thus, the occurrence of 13 C-enriched C 25 HBI could be an ideal marker for good source rocks. The decreased concentration of CO 2 (aq) in the water column induced by diatom blooms can result in an enrichment in 13 C of organic matter synthesized by primary producers. This may be a possible reason for the occurrence of 13 C-enriched organic matter in the Cenozoic source rocks of the Western Qaidam Basin. Previous studies have shown that the high carbon number n-alkanes sourced from diatoms have no carbon preference. Hence, the sources of n-alkanes in regional source rocks are complex, and should be considered when discussing the sources of organic matter in future studies.

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“…Because CO 2 absorption/degassing, in combination with evaporation and rapid microbial growth, can drive extreme carbon isotope enrichment [44], it further suggests that the carbonates in aeolian sediments from Chinese deserts are secondary salt in origin.…”

Section: Secondary Saltmentioning

confidence: 99%

Aeolian Carbon Salts in the Taklamakan and Badanjilin Deserts in Northwestern China and Their Potential Role in Global Carbon Cycle

Zhu¹

2017

AJBES

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Previous studies have suggested that a significant loop in the carbon cycle may be hidden in the global desert areas (both low latitude and middle latitude). Due to the complexity of salt formation involved in atmosphere-landscape relation, there are few study involved into the pool of secondary carbonates in world desert soils, particularly in arid areas in northern China. Large sandy deserts in the middle latitudes of northwestern China were investigated in this study. The physical and geochemical examinations are carried out into soluble carbon salts in modern and ancient dune sediments from the inland deserts in northwestern China, with the aim to explore the composition of carbon salts in aeolian sediments and their possible environmental implications for global carbon cycle. The results show that the aeolian salt has high alkalinities, which are mainly determined by evaporitic alkaline earth carbonates. The carbonates are secondary salt in origin and are possibly introduced from the atmosphere into the pedosphere by a carbon-fixation process. Owing to the high capability to neutralize atmospheric carbonic acid, large desert area, and the strong potential of carbonate preservation in soil under arid climate, the middle-latitude Chinese deserts can be potentially qualified as a significant contributor to the global carbon cycle. But the low-latitude deserts in tropic areas may be not able to provide such a contribution.

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A molecular isotopic study of 13C-enriched organic matter in evaporitic deposits: recognition of CO2-limited ecosystems

Cited by 58 publications

References 31 publications

Stable carbon isotope compositions of isoprenoid chromans in Cenozoic saline lacustrine source rocks from the Western Qaidam Basin, NW China: Source implications

Stable carbon isotope compositions of isoprenoid chromans in Cenozoic saline lacustrine source rocks from the Western Qaidam Basin, NW China: Source implications

The occurrence and significance of C25HBI in Cenozoic saline lacustrine source rocks from the Western Qaidam Basin, NW China

Aeolian Carbon Salts in the Taklamakan and Badanjilin Deserts in Northwestern China and Their Potential Role in Global Carbon Cycle

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