Climate cooling has been commonly considered as one of the most plausible triggers of the Great Ordovician Biodiversification Event (GOBE). However, the details of coeval sea-surface temperature (SST) variation during and after the biodiversification peak are still unclear owing to lack of continuous, high-resolution palaeotemperature records. Here, we report the first high-resolution in situ secondary ion mass spectrometry conodont apatite oxygen isotope (δ18Oapatite) curve from the Kalpin Shuinichang and Dawangou sections (the auxiliary Global Stratotype Section and Point (GSSP) for the base of the Upper Ordovician Series) to reconstruct the detailed Ordovician palaeotemperature history in the Tarim Basin, northwestern China. The new oxygen isotope data, based on mono-generic specimens, reveal a similar first-order variation trend to published records from other palaeocontinents, which is thus suggestive of a global signal. A −0.7‰ δ18Oapatite shift (c. 3.2°C warming) is identifiable in the Dawangou Formation (early–middle Darriwilian). This is followed by a long-term +2.2‰ positive shift in δ18Oapatite (c. 10°C cooling) in the overlying strata spanning the Saergan and the Kanling formations (late Darriwilian–Sandbian), probably indicating a global climatic signal. Examining the coeval marine 87Sr/86Sr records, the early–middle Darriwilian minor δ18Oapatite decrease is coincident with the onset of a long-term negative 87Sr/86Sr excursion, possibly indicating a slight climate warming in response to increasing volcanic degassing in the context of accelerating spreading of mid-oceanic ridges. In contrast, the following long-term positive δ18Oapatite excursion, in parallel with persistent 87Sr/86Sr drop, probably indicates a major climate cooling initially caused by the rapid tropical continental weathering, which in turn may have reduced the continental radiogenic Sr influx.

Supplementary material: Three supplementary tables (S1, S2, and S3) indicating the in-situ oxygen isotopic results of conodont apatite from the Kalpin Shuinichang-Dawangou composite section, Qinghu standard, and Durango standard, respectively are available at

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