A COMPARISON OF GCM SIMULATED CRETACEOUS GREENHOUSE AND ICEHOUSE CLIMATES - IMPLICATIONS FOR THE SEDIMENTARY RECORD

Two General Circulation Model simulations of mid-Cretaceous climate ar e presented, one representing a 'greenhouse' and the other representin g an 'icehouse' world. Through a comparison of 'greenhouse' and 'iceho use' palaeoclimates, differences in processes which are intrinsically linked with climate, such as continental weathering and snow and ice a ccumulation, may be observed. A number of conspicuous and discrete cli matic differences can be seen between the two simulations, which may b e translated into a number of identifiable signatures in the sedimenta ry record. The climate at mid-high latitudes in the 'icehouse' simulat ion was more arid than the 'greenhouse' simulation and could result in deposition of smectite-dominated clay suites. In contrast, the climat e of low latitudes of the 'icehouse' simulation resulted in a moister climate than the 'greenhouse' simulation, which could affect the weath ering regimes and result in deposition of kaolin-dominated clay suites . Thus cool climate episodes do not necessarily result in a global inc rease in aridity. The 'icehouse' simulation predicts a small permanent icecap at high latitudes, which could account for the origin of drops tones in marine sediments. Furthermore, a sea-level fall as a conseque nce of an accumulation of ice at high latitudes may also increase cont inentality and surface albedo which may also contribute to the causes of the drier climate at high latitudes. Hurricanes are likely to be mo re frequent in 'greenhouse' than 'icehouse' climates. Mid-latitude dep ressions, also important for generating storms, are likely to be both intense and frequent during 'icehouse' and 'greenhouse' periods of the middle Cretaceous. (C) 1998 Elsevier Science B.V. All rights reserved .