The Kuanyinchiao Formation (Hirnantian, Upper Ordovician), yielding the typical Hirnantia fauna, has commonly been accepted as representing cool-water sediments deposited during the glacial interval in the Hirnantian Global Boundary Stratotype Section and Point (GSSP) region of South China. Recent investigation reveals that the uppermost carbonate-dominated part of this formation yields a warm-water rugose coral fauna with Silurian affinities at many localities of northern Guizhou Province, which substantially differs from the underlying cool-water fauna. This suggests that these carbonates were probably postglacial warm-water sediments, rather than having formed during the Hirnantian glacial interval as previously thought. Such a conclusion is consistent with the evidence from the associated brachiopod fauna, i.e., the Dalmanella testudinaria – Dorytreta longicrura community, which is similarly distinct from the underlying typical Hirnantia fauna. The sedimentological data show warm-water features at the same level (e.g., the presence of oolitic grains), also supporting this new interpretation.