Abstract
The timing of marine ecosystem recovery following the End Permian Mass Extinction (EPME) remains poorly constrained given the lack of radiometric ages. Here we develop a high-resolution carbonate carbon isotope (δ13Ccarb) record for 3.20 million years of the Olenekian in South China that defines the astronomical time-scale for the critical interval of major evolutionary and oceanic events in the Spathian. δ13Ccarb documents eccentricity modulation of carbon cycling through the period and a strong obliquity signal. A shift in phasing between short and long eccentricity modulation, and amplification of obliquity, is nearly coincident with a 2% decrease in seawater δ13CDIC, the last of a longer-term stepped decrease through the Spathian. The mid-Spathian shift in seawater δ13CDIC to typical thermocline values is interpreted to record a major oceanic reorganization with global climate amelioration. Coincidence of the phasing shift with the first occurrence of marine reptiles (248.81 Ma), suggests that their invasion into the sea and the onset of a complex ecosystem were facilitated by restoration of deep ocean ventilation linked mechanistically to a change in the response of the oceanic carbon reservoir to astronomical forcing. Together these records place the first constraints on the duration of the post-extinction recovery to 3.35 myr.
Highlights
The timing of marine ecosystem recovery following the End Permian Mass Extinction (EPME) remains poorly constrained given the lack of radiometric ages
The veracity of the new δ13Ccarb record is corroborated by similarity in long-term δ13Ccarb trends between the Majiashan section and other global time-equivalent δ13Ccarb records from South China and elsewhere[2,34,35]
To evaluate potential astronomical cycles preserved in the record and their uncertainties, evolutive average spectral misfit (e-ASM) analysis[36] was performed on the δ13Ccarb record following data preparation by statistically comparing the observed oscillations with theoretical periods from the astronomical models La0437 and La10d38
Summary
The timing of marine ecosystem recovery following the End Permian Mass Extinction (EPME) remains poorly constrained given the lack of radiometric ages. Coincidence of the phasing shift with the first occurrence of marine reptiles (248.81 Ma), suggests that their invasion into the sea and the onset of a complex ecosystem were facilitated by restoration of deep ocean ventilation linked mechanistically to a change in the response of the oceanic carbon reservoir to astronomical forcing. Together these records place the first constraints on the duration of the postextinction recovery to 3.35 myr. We develop a new high-resolution C isotopic record of seawater dissolved inorganic carbon (δ13CDIC) for the end-Smithian through Spathian, utilize it to construct an astrononmical time scale, and in turn, apply it to infer major changes in ocean structure mechanistically linked to the timing of ecosystem recovery
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