We present a Sr chemostratigraphic reference section for the late middle to
late Miocene (14-5 Ma) from Ocean Drilling Program site 926 on the Ceara R
ise. This site combines a precise, orbitally tuned timescale with a high se
dimentation rate (15 m/m.y.), continuous deposition, and excellent biostrat
igraphic control. The Sr isotope curve is based on measurements of cleaned,
planktonic foraminifera at 100-200 kyr sample intervals and it illustrates
periods of rapid change in Sr-87/Sr-86 alternating with periods of little
change. Chemostratigraphically-defined ages for these intervals can be dete
rmined within +/-0.8 m.y. and +/-1.6 m.y, respectively. There is excellent
correlation with the published curve for site 588 [Hodell and Woodruff, 199
4]; however the curve for site 747 [Oslick et al., 1994] exhibits less stru
cture, which may be due to small errors in age estimates related to slow se
dimentation rates, high-latitude fauna and an interval of complicated magne
tics. Late Miocene data compare favorably with data from site 758 [Farrell
et al., 1995].