INTRODUCTION

The lanthanide or rare earth elements ([REE]; ⁵⁷La to ⁷¹Lu) form ions that are nearly all trivalent with gradually decreasing ionic radii. The notable exceptions are Ce⁴⁺ and Eu²⁺, stable respectively, under suitable oxidizing and reducing conditions. Ranging continuously in behavior from the incompatible light rare earth elements (LREE; La-Sm) to the selectively compatible heavy rare earth elements (HREE; Gd-Lu), comparisons among REE are facilitated by normalizing the analyses to a reference standard such as chondrite. However, for sedimentary rocks, the North American Shale Composite (NASC; Taylor and McClennan, 1985; Condie, 1991) is preferred as representative of the average upper crust of the earth. Compared to this reference, some fractionation effects may enhance light over heavy REE, and the effects can be quantified by the ratio of normalized La_n/Lu_n >1 or La_n/Lu_n <1, respectively (Holser, 1997). Enhancement of the middle rare earth elements (MREE) may occur relative to both LREE and HREE. More significant deviations from normal concern anomalous amounts of Ce and Eu. An anomalous Ce value may be quantified as a ratio to Ce^*, the anticipated value for Ce³⁺, by interpolating adjacent trivalent REE values such that Ce_an = Ce_n/Ce^*. Whereas modern oceans show marked depletion (negative anomaly) of Ce because of prevalent oxidation to Ce⁴⁺ (Elderfield, 1988), much of the sedimentary record of REE geochemistry reportedly (Holser, 1997) supplies an equivocal signal with respect to redox conditions in contemporaneous seawater. Here, the REE composition and distribution is evaluated in a 447-m-thick continuous interval of sedimentary core from Site 1014 in the Tanner Basin, and the possible link with diagenesis is examined along a highly productive continental margin (Emery, 1960; Shipboard Scientific Party, 1997).