TY - JOUR
T1 - Late Barremian to early Aptian calcareous nannofossil paleoceanography and paleoecology from the Ocean Drilling Program Hole 641C (Galicia Margin)
AU - Tremolada, Fabrizio
AU - Erba, Elisabetta
AU - Bralower, Timothy J.
N1 - Funding Information:
This research used samples and data provided by the Ocean Drilling Program (ODP). ODP is sponsored by the US National Science Foundation (NSF) and participating countries under management of Joint Oceanographic Institutions (JOI) Inc. This work was sponsored by the NSF through Biocomplexity (Evolution and Radiation of Eukaryotic Phytoplankton Taxa project) grant no. OCE-0084032 to Paul G. Falkowski and MIUR-Cofin-2003 to I. Premoli Silva. J. Sessa and J. Bonelli (Pennsylvania State University) are warmly thanked for their assistance with statistical analyses. D. Nichols and two anonymous reviewers provided helpful comments.
PY - 2006/12
Y1 - 2006/12
N2 - Calcareous nannofossil assemblages at Site 641C (Galicia Margin, North Atlantic) were investigated in order to determine changes in fertility and temperature of surface waters. Taxa such as Zeughrabdotus spp. <3.5 μm, Biscutum constans, Discorhabdus rotatorius and Diazomatolithus lehmanii, which thrived in higher fertility conditions, are particularly abundant across the CM0 interval as opposed to those with oligotrophic affinities such as Watznaueria spp. and Nannoconus spp., which are generally reduced in abundance. The abundances of nannoconids are much lower than those observed in Tethyan sections, indicating higher fertility conditions. Slumpings and low recovery prevent the identification of the onset of the "nannoconid crisis", but a sharp drop in nannoconid abundances, observed prior to the CM0 interval, correlates with the "nannoconid decline" observed in several Tethys sections.The normalized ratio between low and high fertility taxa (Fertility Index) was used to characterize the nannofossil assemblages in terms of productivity changes. The highest values of the Fertility Index were observed across magnetic chron CM0. The paucity of cold water taxa such as Seribiscutum spp. and Repagulum parvidentatum suggests warm water conditions throughout the deposition of upper Barremian-lower Aptian sediments on the Galicia Margin.
AB - Calcareous nannofossil assemblages at Site 641C (Galicia Margin, North Atlantic) were investigated in order to determine changes in fertility and temperature of surface waters. Taxa such as Zeughrabdotus spp. <3.5 μm, Biscutum constans, Discorhabdus rotatorius and Diazomatolithus lehmanii, which thrived in higher fertility conditions, are particularly abundant across the CM0 interval as opposed to those with oligotrophic affinities such as Watznaueria spp. and Nannoconus spp., which are generally reduced in abundance. The abundances of nannoconids are much lower than those observed in Tethyan sections, indicating higher fertility conditions. Slumpings and low recovery prevent the identification of the onset of the "nannoconid crisis", but a sharp drop in nannoconid abundances, observed prior to the CM0 interval, correlates with the "nannoconid decline" observed in several Tethys sections.The normalized ratio between low and high fertility taxa (Fertility Index) was used to characterize the nannofossil assemblages in terms of productivity changes. The highest values of the Fertility Index were observed across magnetic chron CM0. The paucity of cold water taxa such as Seribiscutum spp. and Repagulum parvidentatum suggests warm water conditions throughout the deposition of upper Barremian-lower Aptian sediments on the Galicia Margin.
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U2 - 10.1016/j.cretres.2006.04.007
DO - 10.1016/j.cretres.2006.04.007
M3 - Article
AN - SCOPUS:33751116126
SN - 0195-6671
VL - 27
SP - 887
EP - 897
JO - Cretaceous Research
JF - Cretaceous Research
IS - 6
ER -