LATE CRETACEOUS EARLY TERTIARY PALEOCLIMATES OF NORTHERN HIGH-LATITUDES - A QUANTITATIVE VIEW

Analyses of plant community structure, vegetational and leaf physiognomy, and growth rings and vascular systems in wood provide qualitative and quantitative data that can be combined to define non-marine palaeoclimatic parameters with better resolution than is available from other, principally sedimentological, methods. Application of these techniques to Cenomanian through Paleocene floras from high palaeolatitudes (75°-85°N) indicates a polar light regime similar to that of the present. Plant data suggests Cenomanian sea level mean annual air temperatures (MATs) of 10°C, and MATs of 13°C, 5°C and 6-7°C in the Coniacian, Maastrichtian, and Paleocene respectively. Evapotranspirational stresses at sea level were low and precipitation was in most part uniform throughout the growing season in the Cenomanian, with possible seasonal drying occurring by the Maastrichtian. Maastrichtian winter freezing was likely, but periglacial conditions did not exist at sea level. Permanent ice was likely above 1700 m at 75°N in the Cenomanian, and above 1000 m at 85°N in the Maastrichtian. These near-polar data provide critical constraints on global models of Late Cretaceous to early Tertiary climates. -Authors