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What evidence suggests that Pangea had rainy seasons in its dry interior?
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Pangea
Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins near the end of the Permian Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.
While Pangea is widely characterized by its arid interior, paleoclimatologists have identified evidence suggesting the existence of short, seasonal rainy periods within these dry regions.1
This evidence is primarily found in the geological record, which includes:
- Fluvial and Deltaic Deposits: The presence of braided fluvial (riverine) sediments, clay-rich deltaic deposits, and red beds of alluvial and fluvial origin indicates periods of significant water flow and precipitation.2
- Monsoonal Climate Patterns: Scientists resolve the apparent contradiction between arid indicators (such as evaporites and dune deposits) and these water-borne sediments by postulating a monsoonal climate. Under this model, cross-equatorial monsoonal winds would have transported moist air from large bodies of water into the continental interior, resulting in strong, seasonal rainfall.21
These seasonal rains were distinct from the more humid conditions found near the edges of the supercontinent, where the Tethys Sea provided a consistent source of humid tropical air.1