Pb and Nd isotopes in NE Atlantic Fe-Mn crusts: Proxies for trace metal paleosources and paleocean circulation

摘要: Abstract We report high precision Pb isotopic data (2σ ≤ 100 ppm) together with Nd isotopes on depth profiles from two Fe–Mn crusts the eastern Atlantic basin. The provide a 13 Ma record of changes in North Deep Water (ENADW), and over past 8 for Mediterranean Outflow (MOW). isotope ratios records display gradual systematic changes, tracking each other through time. highly precise also resolve, first time, all three single crust, exhibit well-defined binary mixing lines space. Tropic Seamount crust shows that has been dominated by throughout last Ma. further demonstrate change provenance to occurred at 4 This is shown distinctive compositions components time intervals 4–0 13–8 Consideration systematics show present, endmember correspond NADW Southern Component (SCW). quasi-cyclic character 206Pb/204Pb variations, as well age progressive proportions SCW endmembers, appear reflect deep water circulation. In particular, strengthening signal associated since 3–4 both western basins implies advection into operation During period Ma, entirely different sources existed Atlantic. radiogenic unradiogenic component may have originated Norwegian–Greenland seas low 206Pb/204Pb—high eNd ocean or Tethys. suggestion supported evidence paleoceanographic studies indicating importance Greenland–Scotland ridge activity Miocene production, presence δ13C mass Ocean, derived either locally flowing via Lion (65GTV) demonstrates MOW switched predominantly internal, (European) prior mainly external (Saharan) after increase seen following end Messinian reflects enhanced input Saharan dust column “Saharan” about matches documented aridity dustiness sub-Saharan regions coincides re-establishment exchange between Messinian. Although and, lesser extent, are distinct during (6.5–5 Ma), there no clear shutdown stronger this period. fact similar observed, an even higher amplitude ENADW record, feature whole From 3 ago, source appears not only but world oceans, it ubiquitously must be conveyed around globe circulation atmosphere. While closure Panama gateway played important role these global source(s) and/or fluxes oceans ago events, conjunction, such emergence ridge, were probably influential.