Carbon Isotope Stratigraphy of the Cambrian System in the Eastern Tarim Basin, China

Abstract

The ultra-deep Cambrian System in the Tarim Basin is an important field for petroleum exploration, while fine division of the Cambrian strata remains controversial. In recent years, carbon isotope stratigraphy of the Cambrian System has been established and widely used. Here, we report an integrated profile of carbonate and organic carbon isotopic values (δ 13 C carb and δ 13 C org ) from cuttings of the Tadong2 Well in the eastern Tarim Basin. Three carbon isotope anomalies of BACE, ROECE and SPICE were recognized on the δ 13 C carb profile. Three apogees and a nadir on the δ 13 C org profile and the onset of ROECE on the δ 13 C carb profile were suggested as boundaries of the present four series of the Cambrian System. Suggested boundaries are easily identifiable on the gamma logging profile and is consistent with the previous division scheme, based on biostratigraphic evidence in outcrop sections. Abnormal carbon cycle perturbations and organic carbon burials during the BACE and SPICE events might be related to the reduction and expansion of a huge dissolved organic carbon reservoir in the deep ocean of the ancient Tarim Basin.

Intense Human Activities Induce the Dynamic Changes of Interaction Pattern Between Karst Water‐Quaternary Groundwater in the Basin‐Mountain Coupling Belt Over the Past 60 Years

“…According to the δ 18 O isotopic balance calculation, the contribution of Quaternary groundwater for Jinci spring water was 11.8% in the 1980s, which was slightly lower than that reported by Wang (1985) (15.5%–18%). According to the study by Wang (1985), Lancun karst groundwater was taken as the end–member of karst groundwater in the basin‐mountain coupling belt.…”

“…According to the δ 18 O isotopic balance calculation, the contribution of Quaternary groundwater for Jinci spring water was 11.8% in the 1980s, which was slightly lower than that reported by Wang (1985) (15.5%-18%). According to the study by Wang (1985), Lancun karst groundwater was taken as the endmember of karst groundwater in the basin-mountain coupling belt. However, considering that the Jinci groundwater and Lancun groundwater belong to different karst spring systems, we introduce Kaihua groundwater, which is little affected by Quaternary groundwater, as the end-member of karst groundwater.…”

Influence of dissolved organic carbon on the Cambrian Ocean: Evidence from the carbon isotopes of the sedimentary rocks of the Eastern Tarim Basin, North‐west China

“…Consequently, we assume that there is a gradient isotope zone in the vicinity of the continental shelf, and the isotope excursions will occur if the sea level significantly fluctuated. It is worth noting that the δ 13 C carb positively drifted at the transition between the Middle Cambrian and Upper Cambrian in the entire Kuruketage region, corresponding to the global Steptoean positive carbon isotope excursion (SPICE) events (Buggisch et al, 2003; Glumac & Walker, 1998; Kouchinsky et al, 2008; Lindsay et al, 2005; Montañez et al, 2000; Ripperdann et al, 1992; Saltzman et al, 1998, 2000; Wang et al, 2022; Zhu et al, 2004; Zuo et al, 2008). The lack of records of this event in Well TD2 is either related to hiatus or local effects on the continental shelf.…”

“…These changes were recorded in isotope stratigraphy curves from the three profiles (Figure 7). The tive carbon isotope excursion (SPICE) events (Buggisch et al, 2003;Glumac & Walker, 1998;Kouchinsky et al, 2008;Lindsay et al, 2005;Montañez et al, 2000;Ripperdann et al, 1992;Saltzman et al, 1998Saltzman et al, , 2000Wang et al, 2022;Zhu et al, 2004;Zuo et al, 2008). The lack of records of this event in Well TD2 is either related to hiatus or local effects on the continental shelf.…”

Sedimentary Environment and Mineralization of the Black Shale Polymetallic Layer in the Early Cambrian, SW China: Constraints from in situ LA‐ICP‐MS Analysis of Pyrite

“…The δ 34 S values of barite at the bottom of the Niutitang Formation in Dahebian range from 36.7‰ to 43.8‰, with an average of 40.3‰(Wu et al, 2009). The δ 34 S values of pyrite and barite at the bottom of the black shale of the Jiumenchong Formation in the Yundong barite deposit are 22.59‰ and 57.32‰, respectively(Wang et al, 2020). This indicates that the sulfur isotopic compositions of the same time are different in different sedimentary areas.…”