Biological response to Milankovitch forcing during the late Albian (Kirchrode I borehole, northwestern Germany)

We studied the biological response to orbital forcing in marine Upper Albia n sediments recovered from the 245 m-long Kirchrode I borehole in the Lower Saxony basin in northwestern Germany. Results from quantitative analysis o f planktonic and benthic foraminifera, of calcareous nannofossils, and radi olaria were used for this study. Spectral analysis in the depth domain indi cates for the high sedimentation rate part of the Upper Albian dominant per iods with wavelengths of 10-13 m, 5-6 m, and 2-3 m, which we interpret to r epresent the biological response to orbital forcing in the Milankovitch fre quency bands eccentricity, obliquity, and precession, respectively. In addi tion, a low amplitude 40-50 m cycle was found, which would represent the lo ng-term eccentricity variation of roughly 400 ka. Microfossil cyclicity doe s not change significantly within the whole core indicating sedimentation r ates of 11-12 cm/ka on an average, with variations between 3.5 and 13 ka). Microfossils show greater variability in their abundance changes than the p hysical and chemical parameters and also greater power in the higher-freque ncy bands (obliquity and precession). While most of the planktonic foramini fer species studied are dominated by variations in the obliquity, most bent hic foraminifer species show an additional strong influence of precession. These differences in the cyclicity of the abundance changes are interpreted as reflecting a stronger influence of low latitude water in the deep water s of the Late Albian Lower Saxony basin than in the shallow waters. This ba sin was part of a wide, 'Boreal' epicontinental sea, which was connected to the Tethys to the south via the Polish strait and via the Paris basin, and which was connected with the North Atlantic and Arctic to the north. In an alogy to results from analysis of data from the Late Neogene, strong effect s of precession interpreted as being more characteristic for changes/influe nces triggered in the low latitudes and those of obliquity to be more chara cteristic for influences from the high latitudes. The presence of a relatively strong eccentricity cycle, not only in the com pound parameters, but also in the abundance changes of single species durin g the Late Albian means that there must have been a non-linear response to orbital forcing and internal feedbacks. (C) 2001 Elsevier Science B.V. All rights reserved.