Changes in the global carbon cycle occurred as two episodes during the Permian–Triassic crisis

Abstract

Coeval records of ocean, atmosphere, and terrestrial change are crucial to understanding the pattern and causes of global mass extinction across the Permian-Triassic boundary (PTB). However, relationships among changes in different settings remain largely unclear, primarily due to the challenges associated with the correlation among disparate records. Here we compare marine carbon isotopic records with marine and terrestrial environmental and biotic events recorded in sediments from the Meishan PTB section of south China. Timescaled carbonate carbon isotopes exhibit two gradual major shifts across the PTB at Meishan, and these are duplicable elsewhere around the Tethys Ocean. The two shifts are associated with two episodes of enhanced terrestrial weathering indicated by an increased abundance of 13 C-enriched moretanes relative to hopanes and an elevated abundance of black carbon fragments. Key marine events previously reported for the PTB, including photic zone euxinia, faunal mass extinction, and cyanobacterial expansion, also occur as two episodes, coinciding with both of the progressive shifts to negative δ 13 C values and enhanced weathering. The temporal sequence of the duplicable events suggests that the biotic crisis was a consequence of prolonged and episodic changes in the marine and continental systems, and argues against an extraterrestrial impact as the main cause.

High-precision timeline for Earth’s most severe extinction

“…Above this perturbation, δ 13 C (carb) remains at ∼1‰ for the remainder of the Griesbachian. The negative excursion within bed 39 at Meishan was not recognized by Cao et al (11) or Xie et al (17) due to sample spacing, although more closely spaced sampling reported in Song et al (31) recovers it. The second excursion is possibly correlative with one seen in the GK-1 core from the Carnic Alps (32), although this excursion cannot yet be confirmed as a global signal or to be useful in correlation.…”

“…To better understand the relationship between environmental perturbation and biotic response, accurate and precise age models that integrate geochronology, paleontology, and geochemistry must be developed (8,11,16,17). Recognition of astronomically forced sedimentary cycles (Milankovitch cycles) in late Permian and Triassic sedimentary rocks tuned with available geochronology have been used to refine existing age models of the biotic crisis (18)(19)(20).…”

High‐resolution Lopingian (Late Permian) timescale of South China

“…It has been extensively documented that the endChanghsingian mass extinction is associated with a worldwide sharp negative shift of d 13 C. According to the Meishan section (Xu and Yan, 1993;Cao et al, 2002Cao et al, , 2009Riccardi et al, 2006;Xie et al, 2007), both d 13 C carb and d 13 C org began to decrease at the base of Bed 23, which is nearly at the base of the Clarkina yini Zone. The most negative value is at the topmost part of Bed 24 within the Clarkina meishanensis Zone, which is immediately below Bed 25 of 252.25 AE 0.06 Ma and associated with the most severe biotic mass extinction.…”

Geomicrobial functional groups: A window on the interaction between life and environments

“…Thus, nutrient exchange in the water column can trigger a series of biogeochemical processes among different GFGs, which significantly affect marine environments. The presence of a variety of GFGs and the associated marine environmental changes across the Permo-Triassic boundary represented such a case in Earth history [130,131,165,174].…”

“…end Permian and end Cretaceous), in addition to the associated major climate change [165,166]. Stanley [167] proposed that the dominant cause for carbon isotope excursions was associated with the Phanerozoic mass extinctions is change in the respiration rate of marine bacteria.…”