Palynological evidence for late Quaternary climate and marine primary productivity changes along the California margin

Abstract

AbstractA high‐resolution sedimentary record of dinoflagellate cysts from Ocean Drilling Program Hole 1017E (off Point Conception, California margin) reflects how marine primary productivity has changed in response to major shifts in climate and ocean circulation along the California margin over the past 42 kyr. Throughout the studied sequence, dinoflagellate cyst assemblages are dominated by upwelling‐related taxa, signifying the continued presence of coastal upwelling on the margin during the late Quaternary. The cyst record suggests that marine primary productivity was enhanced during the Holocene and Bølling, and to a lesser extent, during the late glacial and most Dansgaard‐Oeschger events, while an apparent reduction in primary productivity can be seen during the Younger Dryas. The best analogue technique, based on a modern dinoflagellate cyst assemblage database from the northeast Pacific, was used for quantitative reconstruction of past sea surface conditions. It points to dynamic changes in annual marine primary productivity (~235–331 g C m−2 yr−1) and sea surface temperature (~10.1–12.6°C in winter; ~13.1–14.3°C in summer), while sea surface salinity appears to be confined to a narrower range (~32.9–33.4 in summer). Our results also indicate noticeable climate variability during the Holocene in this region.