Carbon-isotope stratigraphy of the Lower Ordovician succession in Northeast Greenland: Implications for correlations with St. George Group in western Newfoundland (Canada) and beyond

The Lower Ordovician sequence on the Ella Ø Island in Northeast (N-E) Greenland is a thick shallow marine platform carbonate sequence (∼ 1415 m thick) and constitutes the major part of the Kong Oscar Fjord Group. It consists, from bottom to top, of the Antiklinalbugt, Septembersø, and Cape Weber formations, which are believed to be respectively coeval with the Watts Bight, Boat Harbour, and Catoche formations of the St. George Group in western Newfoundland, Canada. Samples were collected from outcrops at high-resolution intervals and micritic materials were extracted by microdrilling after screening their petrographic and geochemical criteria to evaluate the degree of preservation. The δ13C and δ18O values of well preserved micrite microsamples range from −5.2‰ to 0.5‰ (VPDB) and from −10.3‰ to−6.5‰ (VPDB), respectively. The δ13Ccarb profile of the sequence reveals few negative shifts, which vary between ∼ 2 and 4.7‰ and are associated with unconformities/disconformities, thus reflecting the effect of significant sea-level changes. The δ13C shifts can be correlated with counterparts on the St. George Group and also on the global Lower Ordovician δ13C profiles around the early Tremadoc (∼ 2.3‰) and late Tremadoc–early Arenig (∼ 4.7‰).