Coccolithophores as palaeoecological indicators for shifts of the ITCZ in the Cariaco Basin during the late Quaternary

Abstract

Mertens, K. N. J. M., Lynn, M., Aycard, M., Lin, H.-L. and Louwye, S. 2009. Coccolithophores as palaeoecological indicators for shifts of the ITCZ in the Cariaco Basin during the late Quaternary.ABSTRACT: Coccoliths were studied from the ODP Hole 1002C and core PL07-39PC in the Cariaco Basin. Increases in Emiliania huxleyi are synchronous with decreases of Gephyrocapsa oceanica and vice versa. A new index (GEX) based on the relative abundances of these two taxa is proposed, and correlates with various other proxies. It is shown that GEX can serve as upwelling proxy. This confirms that the Intertropical Convergence Zone shifted north during the Bølling/Allerød, south during the Younger Dryas and back north during the Preboreal. The upwelling proxy shows few discrepancies with the terrigenous record.

Evidence for a prolonged retroflection of the North Brazil Current during glacial stages

“…This is also inferred from low abundances of Florisphaera profunda, a lower photic zone coccolithophore associated with a deep nutricline. As the thermocline and nutricline depths vary concurrently, it is found that the abundance of F. profunda provides a reliable indicator of fluctuations in thermocline depth at the Ceara Rise (Kameo et al, 2004;Mertens et al, 2009).…”

30 000 years of productivity and salinity variations in the late Quaternary Cariaco Basin revealed by dinoflagellate cysts

“…Heinrich events are denoted according to their cited ages (Hemming 2004) with respect to the Cariaco Basin age model for Hole 1002C. Sedimentation rates and accumulation rates are discussed in Mertens et al (2008) and range between 32 and 170 cm/kyr.…”

“…3–4 °C, based on Mg/Ca, Lea et al (2003) and alkenones, Herbert & Schuffert (2000)), and are of similar magnitude as salinity changes (1.2–2.4‰, based on paired Mg/Ca −δ 18 O; McConnell 2008), changes in dinoflagellate cyst assemblages will be mainly related to changes in productivity. However, recent research has shown that dinoflagellate cyst morphology changes with salinity, and, more particularly, process length of Lingulodinium machaerophorum shows a linear relationship to salinity, as shown by studying cultures (Hallett 1999) and surface sediments (Mertens et al 2008).…”

Cell Wall Evolution and Diversity

“…A coccolith consists of an organic base plate to which calcite is complexed Mackinder et al 2010). Coccolith production has major ecological significance as it is responsible for up to 89 % of the total burial flux of calcium carbonate to ocean sediments (Mertens et al 2009). The production of the coccolith in some taxa (e.g., Emiliania) initiates in the Golgi apparatus and a Golgi-derived coccolith vesicle (CV).…”