Is strontium isotope record a strict proxy for chemical weathering rates during the late Miocene (Ocean Drilling Program Site 758A)?

The strontium isotope ratios are examined in the shells of planktic foramin ifer Orbulina universa in 20 samples from the late Miocene (8.03-6.36 Ma) s equence of Ocean Drilling Program (ODP) Site 758A, northeastern Indian Ocea n. The Sr isotope ratios increased between 7.91 and 7.36 Ma and in the late st Miocene (6.48-6.36 Ma) reflecting high riverine flux from increased chem ical weathering and high precipitation in the Himalayan region, The Sr-87/S r-86 values decreased during 7.36 to 6.48 Ma coincident with the main phase of Chron-6 negative carbon shift. The carbon shift reflects high delivery of nutrients to the oceans. This contradicts the use of Sr isotope record a s a strict proxy for global chemical weathering rates. The Sr isotope ratio should be used with great care in understanding the climatic-tectonic conn ections.