Publication Date:
2024-07-23
Description:
Stable isotope analyses and scanning electron micrographs have been carried out on six planktonic forminifera species, Pulleniatina obliquiloculata, Globorotalia tumida, Sphaeroidinella dehiscens, Globigerinoides ruber, Globigerinoides sacculifer and Globigerinoides quadrilobatus from eleven box-cores taken at increasing depths in the equatorial Ontong-Java Plateau (Pacific). This allows us to describe the way dissolution affects the microstructures of the tests of the different species and to quantify the changes of isotopic composition. We may conclude that:
1) dissolution effects on test morphology and stable isotope compositions are species dependent, species with a similar habitat showing a similar trend;
2) the shallow water, thin-shelled species are the first to disappear: scanning electron microscope (SEM) work shows alteration of outer layers. Deep water, thick-shelled species are present in all samples: SEM work shows breakdown and disparition of inner layers;
3) for all species there is a similar trend towards increasing delta18O values with increasing water depths and increasing dissolution. This effect may be as high as 0.6 ‰ per thousand meters for Globorotalia tumida;
4) below the lysocline, around 3500 m, it appears that 13C/12C ratios slightly increase towards equilibrium values for thick shelled species: G. tumida, P. obliquiloculata and S. dehiscens.
14C dates and isotope stratigraphy of two box-cores show that all samples are recent in age, and exclude upward mixing of glacial deposits as an important factor.
Keywords:
BC; Box corer; DEPTH, sediment/rock; Elevation of event; ERDC; ERDC-079BX; ERDC-088BX; ERDC-092BX; ERDC-120BX; ERDC-123BX; ERDC-125BX; ERDC-128BX; ERDC-129BX; ERDC-131BX; ERDC-136BX; ERDC-141BX; Event label; Globigerinoides quadrilobatus, δ13C; Globigerinoides quadrilobatus, δ18O; Globigerinoides ruber, δ13C; Globigerinoides ruber, δ18O; Globigerinoides sacculifer, δ13C; Globigerinoides sacculifer, δ18O; Globorotalia tumida, δ13C; Globorotalia tumida, δ18O; Isotope ratio mass spectrometry; Latitude of event; Longitude of event; Pulleniatina obliquiloculata, δ13C; Pulleniatina obliquiloculata, δ18O; Sphaeroidinella dehiscens, δ13C; Sphaeroidinella dehiscens, δ18O; Thomas Washington
Type:
dataset
Format:
text/tab-separated-values, 92 data points
