Tectonic and Paleogeographic Setting of a New Latest Cretaceous Floristic Province in North America

Abstract

The latest Cretaceous (Santonian to Maastrichtian) Normapolles and Aquilapollenites floristic provinces are well known; they occupied the southeastern part and most of the northern and western parts, respectively, of North America. The continental margin floristic province of this paper differs from the other two provinces because of its largely endemic pollen species, its abundance of Proteacidites group pollen, and its generally low abundance or lack of pollen of the Aquilapollenites, Callistopollenites, Normapolles, wind-pollinated? triporate, and angiosperm monosulcate groups. Characteristic features and geographic distribution of the continental margin province are based on previously described assemblages from British Columbia and newly examined assemblages from California. Latest Cretaceous sediments of this province rest on rocks of the Wrangellia terrane and the Coast Plutonic Complex in southwestern British Columbia, on the Salinian terrane of the La Panza Range, and on the Stanley Mountain terrane of the southeastern San Rafael Mountains, all of which have been translated northward at least 2000 km since the Campanian according to paleomagnetic data. Thus, latest Cretaceous floras of the continental margin province were isolated from floras to the east partly because of oceanic and mountain barriers but probably also because they formed in more tropical climates than most floras of the other two provinces.