Deciphering the Variability in Mg/Ca and Stable Oxygen Isotopes of Individual Foraminifera
Journal
Paleoceanography and Paleoclimatology
Journal Volume
34
Journal Issue
5
Pages
755-773
Date Issued
2019
Author(s)
Abstract
©2019. The Authors. Foraminifera are commonly used in paleoclimate reconstructions as they occur throughout the world's oceans and are often abundantly preserved in the sediments. Traditionally, foraminifera-based proxies like δ 18 O and Mg/Ca are analyzed on pooled specimens of a single species. Analysis of single specimens of foraminifera allows reconstructing climate variability on timescales related to El Niño–Southern Oscillation or seasonality. However, quantitative calibrations between the statistics of individual foraminifera analyses (IFA) and climate variability are still missing. We performed Mg/Ca and δ 18 O measurements on single specimens from core top sediments from different settings to better understand the signal recorded by individual foraminifera. We used three species of planktic foraminifera (Globigerinoides ruber (s.s.), T. sacculifer, and N. dutertrei) from the Indo-Pacific Warm Pool and one species (G. ruber (pink)) from the Gulf of Mexico. Mean values for the different species of Mg/Ca versus calculated δ 18 O temperatures agree with published calibration equations. IFA statistics (both mean and standard deviation) of Mg/Ca and δ 18 O between the different sites show a strong relationship indicating that both proxies are influenced by a common factor, most likely temperature variations during calcification. This strongly supports the use of IFA to reconstruct climate variability. However, our combined IFA data for the different species only show a weak relationship to seasonal and interannual temperature changes, especially when seasonal variability increases at a location. This suggests that the season and depth habitat of the foraminifera strongly affect IFA variability, such that ecology needs to be considered when reconstructing past climate variability.
Subjects
climate variability | individual foraminifer analyses | Mg/Ca | planktic foraminifera | δ O 18
Other Subjects
annual variation; calcium; climate variation; core analysis; El Nino-Southern Oscillation; magnesium; oxygen isotope; paleoclimate; planktonic foraminifera; proxy climate record; reconstruction; stable isotope; warm pool; Atlantic Ocean; Gulf of Mexico; Indian Ocean; Pacific Ocean; Foraminifera; Globigerinoides ruber
Type
journal article