RESPONSE OF BERYLLIUM AND RADIOGENIC ISOTOPE RATIOS IN NORTHERN ATLANTIC DEEP WATER TO THE ONSET OF NORTHERN HEMISPHERE GLACIATION

摘要: We present time-corrected ratios of cosmogenic 10 Be to continent-sourced 9 from two Fe–Mn crusts located in the northwest Atlantic vicinity origins Northern Deep Water (NADW). These initial Be/ represent those ambient seawater at time crust deposition and are constant through last 7 Ma. Previously published isotope records radiogenic Nd Pb isotopes these show a decrease e an increase 206 Pb/ 204 over 5 changes consistent with gradual strength NADW production, Labrador Sea component NADW, or increased erosional input into Sea. Since residence thus advective length scales dissolved deep water lie between Pb, should, contrary what has been observed, vary phase if variations accounted for by paleo-circulation. The observed therefore most likely be explained flux terrigenous matter area Sea, which was possibly associated ice rafting selective leaching isotopes. An that contributes is also possibility, but based on data presented here large-scale thermohaline circulation can discounted as cause tracer variations.