An approximately 250 m thick polydeformed and polymetamorphosed, isotopically unusual, variegated marble (locally termed the ‘Leivset marble’) shows a great lateral extent in the Scandinavian Caledonides. Its extremely 13C-depleted primary nature (−7.9 ± 1.2 ‰ on average, n = 93) makes the Leivset marble unique. This, together with a high Sr content (up to 8740 ppm) that buffered 87Sr/86Sr ratios between 0.70802 and 0.70872, suggests correlation with the worldwide Shuram–Wonoka isotopic event occurring within the 600–550 Ma time interval during the Ediacaran (Vendian) period. Despite a high-grade deformation and metamorphism, the Leivset marble has retained its original carbon and strontium isotope ratios. A combination of the variegated colour with unusually low δ13Ccarb can potentially be used for stratigraphic correlations in high-grade, non-fossiliferous, marble-dominated terranes across the Caledonian orogenic belt in Baltica and Laurentia. Isotope chemostratigraphy has identified a prominent cryptic stratigraphic discontinuity and suggests that the Ediacaran Leivset marble was tectonically juxtaposed above low-grade, Llandovery-age, fossiliferous marbles during the Scandian orogeny.