Brief communication: Rb-Sr dating and provenance of ice-drafted dropstones from the mid-Atlantic ridge at mid-latitudes (36°12’N; 33°53’W)

Abstract. Understanding past iceberg activity during the Quaternary is key to constraining the spatial pattern and dynamics of ice sheets, as well as the amount and distribution of freshwater released during iceberg melting. These mechanisms significantly influence global climate and are primarily constrained by the records of ice-rafted deposits concentrated around ~40–50° N. The significance of iceberg transport at lower latitudes and its potential impact on the Atlantic Ocean circulation remain poorly constrained. In this study, we document three ice-rafted dropstones recovered from the Mid-Atlantic Ridge at mid-latitudes (~36°12’N), which could originate from various localities within the Laurentia or Baltica cratons. Their latitude of deposition is consistent with areas of low‑iceberg concentration during Heinrich events, according to published numerical models of iceberg transport and melting. The samples form a calc‑alkaline magmatic series (monzogranite, granodiorite, and tonalite) and yield in‑situ Rb–Sr ages of ~1700–1630 Ma. This suggests that they derive from the Late Paleoproterozoic Labradorian arc‑accretion orogeny exposed in eastern Canada. This provenance further suggests a relatively low‑altitude iceberg source in the Gulf of Saint Lawrence, favoring iceberg transport to lower latitudes.