Evolution of neodymium isotopic signature of seawater during the Late Cretaceous: Implications for intermediate and deep circulation

摘要: Neodymium isotopic compositions (eNd) have been largely used for the last fifty years as a tracer of past ocean circulation, and more intensively during decade to investigate circulation Cretaceous period. Despite growing set data, patterns still remain unclear this In particular, identification deep-water masses their spatial extension within different oceanic basins are poorly constrained. study we present new eNd data inferred from Nd isotope composition fish remains Fe–Mn oxyhydroxide coatings on foraminifera tests, along with residual (partly detrital) fraction recovered DSDP Sites 152 (Nicaraguan Rise), 258 (Naturaliste Plateau), 323 (Bellinghausen Abyssal Plain), ODP 690 (Maud Rise) 700 (East Georgia Basin, South Atlantic). The presence abundant authigenic minerals in sediments at detected by XRD analyses may explain both middle rare earth element enrichments spectra evolution that mirror bottom waters two sites. results point towards close correspondence between water values late Turonian Santonian. Since these sites also similar those other proto-Indian sites, propose existence common intermediate mass early mid-Cretaceous. would extended central part Atlantic eastern beyond Kerguelen Plateau. Furthermore, south north Rio Grande Rise–Walvis Ridge complex (Sites 530) indistinguishable Campanian, suggesting since least. This view is supported reconstruction Turonian, highlighting likely deep breach Rise proto-Walvis time. Thus possible austral despite potential barriers. Comparison seawater residue Nicaraguan suggests westward through Caribbean Seaway Maastrichtian Palaeocene North Pacific. reduced Pacific influence Atlantic, was responsible uniform, less radiogenic after 80 Ma. Additionally, our document an increasing trend observed several Palaeocene, which pronounced Although origin increase unclear, it might be explained contribution material upper northern By sinking depth, redistributed some extent signatures exchanges.