Variability of Neogene Continental Climates in Northwest Europe - a detailed Study based on Microfloras

Authors : Torsten Utescher, Abdul R. Ashraf, Andreas Dreist

Pages : 289-314

Doi:10.3906/sag-1209-103

View : 21 | Download : 6

Publication Date : 9999-12-31

Article Type : Makaleler

Abstract :This study presents a detailed continental palaeoclimate record for the Neogene of Northwestern Europe. Palynomorph samples from continental to marginal marine deposits in 5 correlated sections from the Lower Rhine Basin (NW Germany) covering the time-span from Burdigalian to Zanclean are analysed. Independent time-control in the sections is provided by sequence stratigraphy. Based on 1470 microfloras 3 temperature (mean annual temperature, warm and cold month mean) and 4 precipitation variables (mean annual precipitation, mean monthly precipitation in the driest, wettest and warmest month) are quantified using the Coexistence Approach, a method employing climate requirements of Nearest Living Relatives of fossil taxa. In face of known limitations in climatic resolution of microflora-based data, present results confirm the major trends in continental Neogene climate evolution of Northwestern Europe as previously reconstructed from macroflora and, in addition, reveal climate change on shorter time scales. Our data suggest a distinct coupling of continental climate with the marine environmental system. Phases of eustatic sea-level lowstand connected to Neogene glaciation events (Mi events) are mirrored in the continental curves. The continental records also show cyclicity at different scales and amplitudes. Small-scale climate variability we observe in the Mid-Miocene and the Tortonian most probably is paced by eccentricity (100 kyr cycles), in the later part of the Langhian and early Serravallian 400 kyr cycles are expressed as well. Along the time-span regarded climate variability is characterized by non-proportional changes of climate variables. During the Miocene, cooling - mainly expressed by a decrease in winter temperature - commonly was connected to drying. A substantial shift of the climate system is indicated for the Pliocene where warm periods tended to be summer-dry, at the same time higher amplitudes of short-term changes point to decreasing climate stability.
Keywords : Neogene, continental palaeoclimate, orbital cycles, palynomorphs, climate variability, Northwest Germany, Lower Rhine Basin