Foraminifer preservation quality in samples analyzed ranges from moderate to excellent in Paleocene and Eocene samples. All Paleogene planktonic foraminifers are white, rather than translucent, and most show (other than where noted) tabular microstructure and no obvious chamber infillings or overgrowths. At Site 1260, the frequent occurrence of sugary surface textures in middle Eocene foraminifers suggests some degree of recrystallization, but no infilling or encrusting secondary calcite was noted in samples picked for stable isotope measurements. The approximate temporal resolution of Paleogene samples with preservation deemed good enough for isotopic analyses is 500 k.y. from Sites 1257 and 1260 and 1 m.y. from Site 1258. For Cretaceous samples analyzed, resolution is much coarser, ranging from ~1 m.y. at Site 1260 to 4 m.y. at Site 1257.
Sample preservation in the Cretaceous samples analyzed was generally good to excellent. In two Cretaceous samples (207-1260B-37R-1, 10–16 cm, and 207-1260B-39R-1, 115–122 cm), spar infilling was observed in the outermost chamber of about 10% of Hedbergella delrioensis. These individuals were avoided when picking for stable isotope analyses. Foraminifers with excellent preservation display translucent tests without obvious overgrowths or recrystallization. Such foraminifers display surface features such as pores, keels, and pustules that look similar to those on modern foraminifers captured in plankton tows. In contrast, foraminifers with good preservation were mostly opaque (usually white) but without evidence of recrystallization, overgrowth, or infilling. Foraminifers with moderate preservation also show no evidence of infilling or recrystallization, but do display a sugary surface texture that may be evidence of minor overgrowth.