Paleogeographic maps provide the minimum information needed to model global atmospheric circulation, that is, the size and distribution of landmasses, oceans, epeiric seas, and mountains. Numerical atmospheric circulation models require data, e.g., sea surface temperature, that are frequently unavailable in the rock record. Therefore, models of past atmospheric circulation must rely on paleogeography as the primary data base. The technique of modeling circulation on the basis of paleogeography alone is qualitative and necessitates some assumptions about certain parameters, e.g., the equator-to-poles temperature gradient. However, this technique has proved viable for the Paleozoic, and therefore it has been used to construct global circulation models for the Mesozoic and C nozoic. The evolution of the circulation patterns since the Permian included, among other features: (1) the breakup of the Permian and Triassic cross-Pangea temperature gradient; (2) the destruction of the Permian monsoonal circulation and its eventual re-establishment late in the Cenozoic; and (3) the re-establishment of circum-polar winds, which last occurred in the Devonian. The circulation models are tested with data on the distribution of climatically controlled sediments, e.g., coals, evaporites, and carbonates, and with biogeographic patterns. The limitations of the qualitative modeling technique can be determined by comparing the late Cenozoic circulation maps with those generated by more quantitative techniques.

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