Relative abundance of major benthic foraminiferal assembalges and total organic carbon content at IODP Site U1391 during the past 1.3 myr
Description
R-mode cluster analysis of foraminiferal census data from the >250 μm fraction reveals six associations. Two of them are closely related to productivity. Association A is composed of miliolids and Cibicidoides pachyderma. Association B consists of Shpaeroidina bulloides, agglutinated taxa, Uvigerina peregrina parva and Lenticulina. Periods of high productivity are marked by high relative abundance of Association B, while low productivity is marked by the dominance of Association A. The faunal record indicates higher productivity during the interglacial periods and the interstadial stages, supported by the reliable productivity proxy—the total organic carbon content (TOC) of the sediments. The relative abundance of Association B is significantly correlated with ETP (a normalized and summed record of three Earth’s orbital parameters) in the ~41-kyr obliquity band, suggesting that the Earth’s obliquity is probably the primary driver of variability in ocean productivity off the Portuguese margin.