Astronomically calibrating early Ediacaran evolution

Abstract

The current low-resolution chronostratigraphic framework for the early Ediacaran Period hampers a comprehensive understanding of potential trigger mechanisms for environmental upheavals and their connections to evolutionary innovation. Here, we establish a high-resolution astrochronological framework spanning ~57.6 million years of the early Ediacaran, anchored by the radioisotopic date of the Gaskiers glaciation onset, based on key sections from South China. Constrained by multiple radioisotopic dates, this framework precisely constrains the timing of the Marinoan deglaciation, Ediacaran Negative carbon isotope excursions 1 and 2 (EN1 and EN2), and key fossil assemblages (acanthomorphic acritarchs, Weng'an and Lantian biotas). These dates indicate the rapid termination of the Marinoan glaciation in South China within 10⁶-10⁷ years, while providing robust temporal evidence for the global synchroneity of EN1, EN2, and Marinoan deglaciation. The integrated chronology refines the age model for early Ediacaran biotic evolution, revealing that ecosystems gradually increased in complexity over multi-million-year timescales while global taxonomic diversity remained relatively stable, punctuated by rapid transitions to novel communities coinciding with biogeochemical perturbations.

Fig. 1. Paleogeographic reconstruction of the Ediacaran Period and stratigraphic data.

a Global paleogeography at ~580 Ma. b Paleogeographic reconstruction of the Ediacaran Yangtze Platform (modified from ref. ), showing locations of studied drillcores (red circles). Reprinted from [Gondwana Research, 19, Ganging Jiang, Xiaoying Shi, Shihong Zhang, Yue Wang, Shuhai Xiao, Stratigraphy and paleogeography of the Ediacaran Doushantuo Formation (ca. 635–551 Ma) in South China, 831–849, 2011], with permission from Elsevier. c, d Core photographs from the transitional interval between Members II and III in the ZK68 and WD1 drillcores, illustrating the lithological variations and continuous stratigraphic succession across this boundary. e, f Representative core photographs showing black mudstone from the lower Member II of the ZK68 drillcore and the upper Member II of the WD1 drillcore. g, h Lamination cycles are closely reflected by variations in MS, as demonstrated by the 2142.85–2148.12 m interval in the WD1 drillcore and the 1412.9–1418.1 m interval in the ZK68 drillcore, which serve as two representative examples. The yellow and red curves represent the long eccentricity (e) and short eccentricity (e) cycles, respectively, extracted using a Gaussian filter with a bandpass of 0.46-0.96 cycles/m (e) and 2.78-3.96 cycles/m (e) for WD1, and 1.21-2.25 cycles/m (e) and 6.05–9.47 cycles/m (e) for ZK68. SC South China; NC North China; MS Magnetic susceptibility.

Fig. 2. Stratigraphic correlation between EYC2, WD1 and ZK68 drillcores and time series analyses.

a–p Chronostratigraphy and lithostratigraphy. c–n δ¹³C_carb data. e–m ⁸⁷Sr/⁸⁶Sr ratios. g–l Raw magnetic susceptibility (MS) data. i–k Extraction of ~405 kyr eccentricity cycles from MS data in EYC2, WD1, and ZK68 drillcores using Gaussian filters. EYC2: ~1.47 m cycles (0.675 ± 0.205 cycles/m). WD1: Five subsets: (D2-1) ~ 1.41 m cycles (0.71 ± 0.25 cycles/m), (D2-2) ~ 2 m cycles (0.50 ± 0.38 cycles/m), (D2-3) ~ 2.5 m cycles (0.40 ± 0.30 cycles/m), (D2-4) ~ 1.50 m cycles (0.665 ± 0.185 cycles/m), (D3) ~ 2.74 m cycles (0.365 ± 0.175 cycles/m). ZK68: Seven subsets—(D1) ~ 3.04 m cycles (0.329 ± 0.251 cycles/m), (D2-1) ~ 0.49 m cycles (2.05 ± 0.44 cycles/m), (D2-2) ~ 0.73 m cycles (1.37 ± 0.54 cycles/m), (D2-3) ~ 0.42 m cycles (2.36 ± 0.28 cycles/m), (D2-4) ~ 0.68 m cycles (1.47 ± 0.29 cycles/m), (D2-5) ~ 0.57 m cycles (1.73 ± 0.52 cycles/m), (D3) ~ 2.10 m cycles (0.475 ± 0.155 cycles/m). The CA-ID-TIMS zircon U-Pb ages (in red) of 635.23 ± 0.57 Ma and 632.50 ± 0.48 Ma from ref. and of 580.9 ± 0.4 Ma, 579.63 ± 0.15 Ma and 579.24 ± 0.17 Ma from refs. ^,, and sediment Re-Os date (in green) of 587.2 ± 3.6 Ma from ref. Details on the Gaskiers glaciation in South China are provided in Supplementary Note 4. MS, δ¹³C_carb, and ⁸⁷Sr/⁸⁶Sr data are in Supplementary Datas 1 and 2. Cryo. Cryogenian; NT. Nantuo Formation. EN1 Ediacaran Negative excursion 1; EN2 Ediacaran Negative excursion 2; EP1 Ediacaran Positive excursion 1; WANCE Weng’An Negative Carbon isotope Excursion.

Fig. 3. The radioisotopically anchored astronomical time scales for the early Ediacaran Period.

a, l Astrochronological framework for the lower-middle Doushantuo Formation. b, c, k Tuned δ¹³C_carb data. d–j Tuned ⁸⁷Sr/⁸⁶Sr ratios. f–i Tuned MS series. The ~405 kyr long eccentricity cycles (red curve) were extracted using a Gaussian filter with all passbands: 0.00247 ± 0.00050 cycles/kyr. The “E” in the ZK68 and WD1 drillcores is numbered sequentially from the Member II/III boundary downward, whereas in the EYC2 drillcore, the “E” is numbered from the base of the Doushantuo Formation upward. Age models for the WD1 and ZK68 drillcores are anchored to the CA-ID-TIMS date of 579.63 ± 0.15 Ma (Anchor point 1), marking the onset of Gaskiers glaciation, while that for the EYC2 drillcore is anchored to the astronomically calibrated age of 634.90 ± 0.43 Ma (Anchor point 2) for the Member I/II boundary from the ZK68 drillcore. h The age models are supported by published radiometric dating: 635.23 ± 0.57 Ma, 632.50 ± 0.48 Ma, 587.2 ± 3.6 Ma, 580.9 ± 0.4 Ma^,, and 579.24 ± 0.17 Ma. Detailed information regarding age models and floating ATS is provided in Supplementary Data 2. EN1 Ediacaran Negative excursion 1; EN2 Ediacaran Negative excursion 2; EP1 Ediacaran Positive excursion 1; WANCE Weng’An Negative Carbon isotope Excursion.

Fig. 4. Integrated ocean oxygenation patterns, carbon and strontium isotope curves and their correlation with key fossil records in the early Ediacaran Period.

a Oxygenation pattern for the early Ediacaran ocean based on compiled uranium isotope records and iron speciation data^,,,. b Global diversity (#Genera), fossil ranges, and the key evolutionary events following ref. . See Supplementary Notes 5–6 for a detailed discussion on the age ranges of acanthomorphs, as well as the Lantian and Weng’an biota. c, d Compilation of strontium and carbon isotope records for the early Ediacaran Period and their correlation to fossil ranges. Gray line through δ¹³C_carb and ⁸⁷Sr/⁸⁶Sr data denotes locally weighted scatter plot smoothing. Global paleogeographic reconstructions at ~600 Ma illustrate the final stages of the breakup of the Rodinia supercontinent. Age constraints for the ⁸⁷Sr/⁸⁶Sr ratios and δ¹³C_carb curves are derived assuming constant sedimentation rates between radioisotopic dates and astrochronological tie points, as detailed in Supplementary Datas 4 and 5. OOE Oceanic oxygenation event; A.-W.-T. Appendisphaera grandis–Weissiella grandistella–Tianzhushania spinose; T.-S. Tanarium tuberosum–Schizofusa zangwenlongii; Tc-Cb Tanarium conoideum–Cavaspina basiconica; Tp-Cg Tanarium pycnacanthum–Ceratosphaeridium glaberosom.