North Pacific palaeoceanography: late Quaternary coiling variations of planktonic foraminifer Neogloboquadrina pachyderma

Intraspecific coiling variations of the planktonic foraminifer Neogloboquadrina pachyderma (Ehrenberg) form an important micropalaeontological technique for the palaeoclimatic interpretation of late Cenozoic mid-latitude marine sediments. In all the modern oceans, this species preferentially coils dextrally in subtropical to temperate latitudes and sinistrally in subpolar to polar latitudes^1,2. Plankton^3-5 and surface sediment studies^6-20 of the North Pacific clearly associate sinistral populations with subarctic water masses and dextral populations with temperate subtropical regions. Here we show that down-core ratios of sinistral to dextral coiling, when correlated with oxygen isotopes, indicate major late Quaternary southward advances of the subarctic boundary (polar front) and the Oyashio Current during oxygen isotope stages 2,4 and 6.