Palaeoecological significances of deep-sea benthic foraminifera from Cascadia Margin, North East Pacific Ocean

Abstract

The strong relationship between benthic foraminifera’s habitat and morphological characteristics to their surrounding environment are dominant component in marine community. This study attempts to understand the significance of benthic foraminifera in ecological importance and paleoceanographic reconstructions at Cascadia Margin, NE Pacific Ocean during the Pleistocene. The quantitative analyses of deep sea benthic foraminifera, particularly Bulimina exilis, Cibicides kullenbergi, Elphidium batialis, Epistominella exigua and Uvigerina proboscidea generally show higher abundances in the studied interval. The Gas Hydrate Stability Zone in the Cascadia Margin at ∼1200 ka to 162 ka (GHSZ; ∼240–70 mbsf) is related to low temperature and high-pressure conditions which are responsible for lower abundances of benthic foraminifera across that interval. The Alaska Current, North Pacific Current and California Current, also known as Eastern Boundary Currents (EBC), play a major role in the transportation of suspended sediments and coastal upwelling throughout the coast across the ∼650 to 450 ka and ∼35 to 2 ka intervals. The relative abundance rate of benthic foraminiferal community decreases with increasing core depth, indicating the influence of less ventilated and nutrient-enriched North Pacific Intermediate Water (NPIW). The present study also signifies the disappearance of benthic faunas throughout the Early–Middle Pleistocene Transition (EMPT, 1250–700 ka, Clark et al., 2006) period due to increased cyclic seasonality and decreased food supply, with few species (Bolivina alata, Bolivina spathulata, Cibicides wuellerstorfi, Epistominella exigua, Gavelinopsis lobatulus and Uvigerina peregrina) being exceptions.