Texas A&M University, United States

In this data report we present results from stable isotope measurements (delta (super 13) C and delta (super 18) O) on bulk sediment at several sites located on a transect along a subduction margin offshore Costa Rica (Ocean Drilling Program Sites 1039, 1040, and 1253). Comparison of stable isotope compositions (delta (super 13) C and delta (super 18) O) of the pelagic carbonates Subunit U3C between the reference sites (Site 1039 and 1253) and the underthrust section (Site 1040) reveals similar delta (super 13) C values and minor differences in delta (super 18) O values within four specific intervals. Isotope stratigraphy was then used to further constrain the shipboard age models based on bio- and magnetostratigraphy. The resulting age models are in agreement with those derived from biostratigraphy and confirm that the sedimentation rate of the lower Subunit 3C is roughly constant on the order of 50 m/ m.y. This is in contrast with the postulated very high sedimentation rates at approximately 12.7 Ma and lower sedimentation rates ( approximately 18 m/m.y.) in the lower part of the section between 16 and 13 Ma, as suggested by shipboard magnetostratigraphic datums.