Distribution patterns of benthic foraminifera across the Ypresian-Lutetian Gorrondatxe section, Northern Spain: Response to sedimentary disturbance

作者：Ortiz Silvia^*; Alegret Laia; Payros Aitor; Orue Etxebarria Xabier; Apellaniz Estibaliz; Molina Eustoquio

来源：Marine Micropaleontology, 2011, 78(1-2): 1-13.

DOI：10.1016/j.marmicro.2010.09.004

• Benthic foraminifera
• Sedimentary disturbance
• Organic matter
• Turbidites
• Eocene
• Gorrondatxe

We present a study of benthic foraminiferal assemblages from an Ypresian-Lutetian distal submarine fan system in the lower bathyal Gorrondatxe section (Basque-Cantabrian Basin, northern Spain). The objective of our study is to analyze the benthic foraminiferal distribution patterns and their response to sedimentary disturbance and related factors.
Assemblages contain a high percentage of allochthonous taxa, such as asterigerinids and other shallow water taxa, which were transported downslope by turbidity currents.
Detailed quantitative analyses, supported by R-mode cluster and Detrended Correspondence Analyses (after removing allochthonous taxa from the foraminiferal counts) allowed us to identify 6 assemblages that are divided into two groups related to the turbidite content in the Gorrondatxe section. Assemblages 1, characteristic of the turbidite-poor intervals with low sedimentary disturbance, include assemblage la (with highly diverse common middle-lower bathyal calcareous taxa) assemblage 1b (with common agglutinated taxa, mainly trochamminids), and assemblage 1c (characterized by calcareous taxa that are also common in the turbidite-rich interval).
2a (characterized by the dominance of infaunal bolivinids and epifaunal cibicids), assemblage 2b (typified by moderate to low diversity and dominated by deep-infaunal Globobulimina species), and assemblage 2c (typified by very abundant suspension-feeding astrorhizids). The high abundance of bolivinids and Globobulimina species may be related to an enhanced input of low-quality organic matter transported by turbidity currents to the seafloor, representing different stages of recolonisation after disturbance and different energy regimes. High current activity was probably responsible for the abundance of cibicids, while moderate to low diverse and high dominance assemblages characterize the recolonisation of the substrate after disturbance.
We conclude that sedimentary disturbance and other related factors such as current activity, resuspension of sediments at the seafloor, and supply of organic matter (and its quality) played an important role in the distribution of benthic foraminifera in the Gorrondatxe section. The identification of allochthonous taxa emerges as an essential aspect of the study of environments with sedimentary disturbance.

• 出版日期2011-1