Publication Date:
2024-01-09
Description:
An Oligocene-basal Miocene (Zones P19-P22/N4) oxygen and carbon isotope stratigraphy is presented based on mixed benthic foraminiferal faunas and different species of planktic foraminifers from Eastem Indian Ocean ODP Hole 758A. Lack of covariance in planktic and benthic delta18O ratios indicates that many Oligocene sea level fluctuations, including the major fall at 30 Ma, are not of glacio-eustatic origin. Delta18O values suggest that test morphology is a poor indicator of preferred depth habitat of Oligocene planktic foraminifers. Also, some groups show considerable shifts in preferred depth habitat. Reconstructed surface water temperature was nearly constant during the investigated period, but even assuming a large Antarctic icecap, values are unrealistically low, 18°-20°C. Most likely, water masses with markedly different oxygen isotopic composition existed, this poses great problems for quantitative temperature reconstructions.
Planktic foraminiferal species show similar delta13C ratios, indicating well-mixed surface waters. This contrasts with the strong oxygen isotopic gradient, which suggests well-stratified surface waters. During the Oligocene the difference in delta13C ratio between the average ratio of planktic foraminiferal species and the benthic foraminifers (Delta delta13C P-B') shows an inverse relation with the known circulation intensity record and thus with productivity. This Delta delta13C pattern is interpreted as being caused by the presence of younger bottom waters at this site during periods with lower temperatures and/or larger Antarctic ice sheets.
Keywords:
121-758A; Catapsydrax dissimilis, δ13C; Catapsydrax dissimilis, δ18O; Catapsydrax spp., δ13C; Catapsydrax spp., δ18O; Catapsydrax unicavus, δ13C; Catapsydrax unicavus, δ18O; Comment; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Fohsella kugleri, δ13C; Fohsella kugleri, δ18O; Foraminifera, benthic δ13C; Foraminifera, benthic δ18O; Foraminifera, planktic δ13C; Foraminifera, planktic δ18O; Globigerina binaiensis, δ13C; Globigerina binaiensis, δ18O; Globigerina euapertura, δ13C; Globigerina euapertura, δ18O; Globigerina galavisi, δ13C; Globigerina galavisi, δ18O; Globigerina sellii, δ13C; Globigerina sellii, δ18O; Globigerina tripartita, δ13C; Globigerina tripartita, δ18O; Globorotaloides suteri, δ13C; Globorotaloides suteri, δ18O; Indian Ocean; Jenkinsella spp., δ13C; Jenkinsella spp., δ18O; Joides Resolution; Leg121; Mass spectrometer Finnigan MAT 251; Ocean Drilling Program; ODP; ORDINAL NUMBER; Sample code/label
Type:
Dataset
Format:
text/tab-separated-values, 418 data points
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