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Belasky, Paul, 1994

Permian paleogeography of the tropical Pacific region: A biogeographic approach to the determination of longitude

Bibliographic Reference

Belasky, Paul, 1994, Permian paleogeography of the tropical Pacific region: A biogeographic approach to the determination of longitude: University of California, Los Angeles, Ph.D. dissertation, 381 p., illust.


Suspect terranes in western North America contain Permian taxa which were endemic to the Tethyan region. According to one hypothesis, the rocks containing these faunas were transported across the Paleopacific Ocean by plate motion during the Mesozoic. An alternative explanation is that the Tethyan species crossed the Paleopacific Ocean in much the same way as modern Indo-Pacific corals migrated into central America. Trend-surface analysis of modern and Permian biogeographic data and probabilistic estimates of taxonomic diversity and similarity constitute a new approach to understanding the origin of these faunas and constraining the paleolongitude of the terranes which contain them. The gradual decline in diversity of modern coral genera eastward across the Pacific Ocean represents a measure of longitude that may be used to find the location of an island if its paleomagnetically derived latitude and the value of coral diversity are both known. Thus, the locations of thirty five Pacific islands were constrained with an average error of 1,900 km. This technique was applied to data on Permian colonial and complex solitary rugose corals. Results indicate that South China was the center of diversity of the Tethyan coral province and was located near the Permian equator and the western margin of the Paleopacific Ocean. The eastern boundary of the Tethyan coral province was situated 1,500 km - 2,000 km west of the North American craton at the equator. The Eastern Klamath and Stikinia terranes were located in general proximity to one another and at a maximum distance of 6,700 km west of the North American craton during the Early Permian, whereas the Wrangellia and Alexander terranes were situated to the southeast of Stikinia and up to a 5,000 km west of the craton, though probably considerably closer. The Late Permian location of the Cache Creek terrane is regarded as exotic with respect to North America, as is the location of the Eastern Klamath terrane, which was constrained to an area 3000 km-5800 km west of the craton and bounded by latitudes 11$\sp\circ$N and 21$\sp\circ$N. In addition to Permian corals, the proposed method of reconstruction can be applied to other faunas of Tethyan or Indo-Pacific affinity and to other Circum-Pacific terranes. However, its application is recommended for those time intervals of the Phanerozoic during which the continental barriers prevented warm water from the Tethys from entering the Paleopacific Ocean from the east and gave rise to strong eastward decline in temperature across the tropical Pacific basin.

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