The Vendian-Cambrian δ13C record, North Iran: evidence for overturning of the ocean before the Cambrian Explosion

Dynamics of the Neoproterozoic carbon cycle

“…The interactions inherent in this system lead naturally to the coincidence of three independent isotopic signals: the onset of quasistatic evolution of the carbon-isotopic records (Fig. 1b) and the negative excursion accompanying it (3)(4)(5); the disappearance of 13 C-enriched secondary biomarkers (18); and the onset of complementarity between the isotopic records of carbonate carbon and oceanic sulfate (31,32). Further correspondences are likely to be found.…”

“…Past changes within the cycle are recorded in the isotopic content of carbonate and organic carbon buried in ancient sediments (2). Extraordinarily large fluctuations occur in the Neoproterozoic [1,000-543 million years ago (Ma)] carbon-isotopic record both immediately preceding the Cambrian diversification of complex animal life (3)(4)(5) and in the Ϸ200 million years before it (6). There is much interest in determining not only the cause of these isotopic events (3-9) but how, if at all, they are related to early animal evolution (10).…”

Significant carbon isotope excursions in the Cambrian and their implications for global correlations

“…The earliest records might be the work in Morocco [1], Siberia [2], and subsequently South China [3]. So far, data of the carbon chemostratigraphy have covered most of the continents [2,[4][5][6][7][8][9][10][11][12][13]. Most of the results are regional, the sampled sections or drilling cores are always limited to parts of the Cambrian System, so carbon isotope data in the Cambrian are inevitably scattered.…”

Stable isotopic study of late Neoproterozoic-early Cambrian (?) sediments from Nagaur-Ganganagar basin, western India: Possible signatures of global and regional C-isotopic events

“…Possibly the most well recognized late Neoproterozoic isotopic perturbation is the one through terminal Neoproterozoic-Nemakit-DaldynianTommotian. δ 13 C carb excursion through this time window has been recorded from Aldan river section (southern Siberia, Magaritz et al, 1986), Anti Atlas mountain in Morocco (Tucker, 1986), Krol Belt in lesser Himalaya (Aharon et al, 1987;Banerjee et al, 1997), Oued Sdas in Morocco (Magaritz et al, 1991), Olenek Uplift in northern Siberia , McKenzie Mountain in north western Canada (Narbonne et al, 1994), Elburz mountain, Iran (Kimura et al, 1997), Meischucun, China and Death Valley in United states (Corsetti and Hagadorn, 2000). Figure 6 is a graphical correlation of the C-isotopic perturbation through N3-P3-N4 from the Bilara Hill section with the C isotopic excursion through late Neoproterozoic-early Cambrian transitional successions in lesser Himalaya (India), southern Siberia, northern Siberia and Morocco.…”

“…4A). Such covariance in the isotopic compositions through time reflects secular changes in the 13 C/ 12 C ratio of aquatic carbon reservoir and can not be an artifact of secondary processes (Knoll et al, 1986;Narbonne et al, 1994;Kimura et al, 1997). The positive excursion of δ 13 C carb may be linked to preferential bio-…”