High-resolution SIMS oxygen isotope analysis on conodont apatite from South China and implications for the end-Permian mass extinction

Abstract

Understanding the interplay of climatic and biological events in deep time requires resolving the precise timing and pattern of paleotemperature changes and their temporal relationship with carbon cycle variations and biodiversity fluctuations. In situ oxygen isotope analyses of conodont apatite from South China enables us to reconstruct high-resolution seawater temperature records across the Permian-Triassic boundary (PTB) intervals in the upper slope (Meishan), lower slope (Shangsi), and carbonate platform (Daijiagou and Liangfengya) settings. Constrained by the latest high-precision geochronological dates and high-resolution conodont biozones, we can establish the temporal and spatial patterns of seawater temperature changes and assess their potential connections with the carbon cycle disruption and biodiversity decline. We find a rapid warming of~10°C during the latest Permian-earliest Triassic that postdated the onset of the negative shift in δ 13 C carb by~81 kyr (thousand years), the abrupt decline in δ 13 C carb by~32 kyr and the onset of mass extinction by~23 kyr, which contradicts previous claims that the extreme temperature rise started immediately before or coincided with the onset of mass extinction. Our new evidence indicates that climate warming was most likely not a direct cause for the main pulse of the end-Permian mass extinction (EPME), but rather a later participant or a catalyst that increased the pace of the biodiversity decline. In addition, a prominent cooling is recorded in the earliest Changhsingian, with the main phase (a drop of~8°C in~0.2 Ma) confined to the lower part of the Clarkina wangi zone and synchronous with the positive limb of the carbon isotope excursion (CIE) around the Wuchiapingian-Changhsingian boundary (WCB) in Meishan and Shangsi. Further long-term and high-resolution studies from other sections are needed to confirm the full contexts and underlying dynamics of the WCB "cooling event".

Oxygen isotope homogeneity assessment for apatite U‐Th‐Pb geochronology reference materials

“…In geological studies, the various compositions of trace elements (eg, REEs, Sr, Fe, Mn, and halogens) and oxygen isotopes of apatite can be effectively integrated to trace the source and evolution of hydrothermal (including ore‐forming) fluids, igneous petrogenesis, and thermal‐chronological evolution . Apatite is also a key constituent in bones, teeth, and fish scales, analysing which in the fossil record can shed light on a variety of paleo‐environmental parameters . For instance, oxygen isotopic compositions in biogenic apatites have been widely used as a proxy for reconstructing seawater temperatures and major glaciation events in the past .…”

“…Apatite is also a key constituent in bones, teeth, and fish scales, analysing which in the fossil record can shed light on a variety of paleo‐environmental parameters . For instance, oxygen isotopic compositions in biogenic apatites have been widely used as a proxy for reconstructing seawater temperatures and major glaciation events in the past . Apatite oxygen isotopes have been measured using the fluorination technique and secondary ion mass spectrometry (SIMS) .…”

“…For instance, oxygen isotopic compositions in biogenic apatites have been widely used as a proxy for reconstructing seawater temperatures and major glaciation events in the past . Apatite oxygen isotopes have been measured using the fluorination technique and secondary ion mass spectrometry (SIMS) . The fluorination technique gives high precision data, but it is sample destructive and requires a relatively large sample size, typically from ~0.2 to 2 mg .…”

“…[18][19][20][21] Apatite is also a key constituent in bones, teeth, and fish scales, analysing which in the fossil record can shed light on a variety of paleo-environmental parameters. 22,23 For instance, oxygen isotopic compositions in biogenic apatites have been widely used as a proxy for reconstructing seawater temperatures and major glaciation events…”

“…[22][23][24][25][26][27] Apatite oxygen isotopes have been measured using the fluorination technique and secondary ion mass spectrometry (SIMS). 18,22,23,[27][28][29][30][31] The fluorination technique gives high precision data, but it is sample destructive and requires a relatively large sample size, typically from~0.2 to 2 mg. 1,[32][33][34] In recent years, many studies have found that the oxygen isotopic compositions of many apatite samples are not uniform even in the micrometre scales, and complexity is also brought by inclusions and cracks in the apatite grains. 22,23,27 Meanwhile, SIMS can measure oxygen isotopic compositions with high spatial resolution, but the matrix effect represents a major technical limitation.…”