Multi-proxy records showing significant Holocene environmental variability: the inner N. Iceland shelf (Hunafloi)

Over the last 50 yr the N. Iceland margin has seen dramatic changes in temperature and salinity associated with the relative dominance of warm Atlantic water versus cold Arctic or Polar waters. We report a study of Holocene environmental changes to assess the sensitivity of this area on a longer timescale. We present sedimentologic, isotopic, and biotic (coccolith) proxies from a 5.5 m piston core, B997-330PC, that was retrieved from a small basin on the inner N. Iceland shelf. Seven AMS dates indicate a relatively constant rate of sediment accumulation which averaged 55 cm/kyr. Sampling resolution of our proxies varied between 16 and 90 yr/sample. Our data indicate substantial variability in environmental conditions over the last 10,000 cal yr. Total carbonate content and coccolith concentrations track each other and indicate that the early Holocene was a time of low net carbonate accumulation. Net accumulation of carbonate reached maximum values in the mid- to late Holocene (4-2 cal ka) but there has since been a substantial decrease with a minima during the Little Ice Age. North Atlantic Drift coccolith species show peaks in accumulation rates at 2 and similar to 8 cal ka, and low influx between 3.5 and 6 cal ka. Reworked Neogene coccoliths occur also similar to 8 ka and coincide with light delta(18)O values in the epifaunal foraminifera Cibicides lobatulus. Principal component analysis indicates considerable covariance between biotic, isotopic, and sedimentological parameters. Three axes explain 84% of the variance in the data set and define three groups of interrelated variables. A major change occurs ca. 5 cal ka after which conditions become more variable with a 1.5 kyr cyclicity. (C) 2002 Elsevier Science Ltd. All rights reserved.