Tertiary petrified forests at Kujulik Bay and Unga Island, Alaska Peninsula, show that growth rings in individual petrified stumps are thicker on one side of the stumps than the other, as do recent trees. Explanations for preferential growth of tree rings include (1) direction of prevailing winds, (2) downslope direction, and (3) direction of prevailing sunlight. The third explanation is considered most plausible for the Kujulik Bay and Unga Island petrified forests. Because these forests lived in the Northern Hemisphere, their directions of prevailing sunlight (and therefore preferential growth) should have been to their paleosouth. As such, the petrified forests at Kujulik Bay (late Eocene to early Oligocene) and Unga Island (late Miocene) suggest paleosouth was located, respectively, to S38 ± 14°W and S44 ± 15°W.

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