Flora and vegetation of the Quaternary temperate stages of NW Europe: Evidence for large-scale range changes

摘要

Oxygen isotope records from deep marine sediments provide ample evidence that large scale fluctuations in global climate have occurred since about 2-6 Ma (the Gauss-Matuyama boundary, e.g. Shackleton 1987; Ruddiman & Raymo 1988). These climatic fluctuations have resulted in alternating periods of cold, cool and warm conditions in NW Europe which can be clearly identified, albeit in fragmentary fashion, from terrestrial sedimentary sequences. The degree of climate change during the Pleistocene has been variable in magnitude and frequency with earlier cyclicity (over the periods 14 Ma -2-0 Ma and 0-9 Ma - 14 Ma) having a shorter wavelength and amplitude than later cyclicity. During the period between 0-9 Ma and 14 Ma isotopic fluctuations suggest a predominant 41,000 year cycle (Ruddiman ef al. 1986) whilst from 0.9Ma to the present the cold stages occur over 100,000 year intervals (Shackleton & Opdyke 1976). Figure 1 shows an oxygen isotope record and the inherent complexity of climate change since 2-6 Ma.