Carbon isotope composition and correlation across the Cambrian-Ordovician boundary in Kalpin Region of the Tarim Basin, China

Abstract

Biostratigraphically constrained sequences at the Wushi Yingshan and Kalpin Cement Plant sections (Kalpin Region; Tarim Basin) were densely sampled for geochemical studies. Carbonates across the Cambrian-Ordovician boundary of both sections mainly record negative carbon isotope values. Stable isotope curves show four negative and four positive excursions appearing alternately at the Wushi Yingshan section and five negative alternating with five positive excursions at the Kalpin Cement Plant section. The carbon isotope logs of these two sections are correlated with the international Cambrian-Ordovician boundary key sections: (1) Dayangcha section in China, (2) Green Point section in Canada, (3) Black mountain section in Australia and (4) Lowson Cove section in USA. These correlations suggest that the Cambrian-Ordovician boundary of the Wushi Yingshan section and theKalpin Cement Plant section can be placed within a particular horizon that also corresponds to the observed biostratigraphic units.

Proposed stratotype for the base of the Lawsonian Stage (Cambrian Stage 10) at the First Appearance Datum of Eoconodontus notchpeakensis (Miller) in the House Range, Utah, USA

“…11 is in the Tarim Basin, far western China. Jing et al (2008, fig. 5) used a combination of conodont faunas and carbon-isotope profiles to correlate strata in the Tarim Basin with strata in North China, Australia, Newfoundland, and Lawson Cove, Utah.…”

“…11. However, the correlations of Jing et al (2008) using carbon-isotope profiles indicate that strata that they studied surely do include the Eoconodontus Zone. Their isotopic correlations are discussed in a later section of this report.…”

“…Jing et al (2008, fig. 5) produced a carbon-isotope profile from the Tarim Plateau in far western China and used conodont biostratigraphy to assist their correlations to other areas.…”

Carbon and strontium isotopes and global correlation of Cambrian Series 2-Series 3 carbonate rocks in the Keping area of the northwestern Tarim Basin, NW China

“…Wang and Yang (1994) reported the carbon isotope variations from late Neoproterozoic to Ordovician for the Keping area; however, their data are limited for the Cambrian Series 2-Series 3 interval. In addition, carbon isotope stratigraphic studies of the Neoproterozoic-Cambrian and Cambrian-Ordovician boundaries have been reported by He et al (2007) and Jing et al (2008), respectively.…”

Positive carbon isotope excursions: global correlation and genesis in the Middle–Upper Ordovician in the northern Tarim Basin, Northwest China

“…In addition, Wang (2000) employed d 13 C carb -positive excursions as the proof of marine source rock developing in the Middle-Upper Ordovician. In recent years, some scholars have been engaged in the study of carbon isotope stratigraphy at Cambrian-Ordovician outcrops in the Kalpin and Bachu regions (Jing et al 2008;Hu et al 2010;Wang et al 2011;Zhao 2015). Zhang et al (2014) discussed d 13 C carb curve features of the Ordovician using analyses of cores and cuttings from the Bachu and Tazhong uplifts ( Fig.…”