Late Cretaceous pollen from the Salinian(?) suspect terrane at Pigeon Point, San Mateo County, California

Abstract

The Companion to Maastrichtian Pigeon Point Formation is confined to southwestern San Mateo County, California; the formation is spatially isolated from similar Upper Cretaceous sedimentary rocks. The basement on which the formation rests is not exposed, but the Pigeon Point block is thought by most authors to be part of the Salinian suspect terrane. Reconstructions based on paleomagnetic data have indicated that the Pigeon Point block originated at the continental margin and was then transported some 2,500 km northward since deposition of this formation, but other studies suggest that the Pigeon Point Formation instead may have originated well within the southwestern part of the North American continent.This report describes the flora from two samples of the Pigeon Point Formation; at least 16 angiosperm pollen species have been found, as well as several potentially significant species of spores and gymnosperm pollen. A comparison of this flora with those from Upper Cretaceous suspect terranes of California and British Columbia, and from autochthonous Upper Cretaceous sedimentary units in the Central Valley of California and the Western Interior region of New Mexico, shows that the Pigeon Point flora belongs to the continental margin floristic province, and the most similar known flora in that province is from an upper Campanian to lower Maastrichtian unit lying on the Salinian terrane in the La Panza Range of San Luis Obispo County. The Pigeon Point flora cannot be used to prove or disprove the hypothesis that the Pigeon Point Formation rests on Salinian basement, but the flora does suggest that when the formation was deposited, the Pigeon Point block did not lie at a latitude as far north as the present United States.

Clast Provenance Constraints, Late Cretaceous Pigeon Point Formation, California

“…A palynologic study by Frederiksen (1990) suggested that the Pigeon Point Formation was deposited at a latitude south of the present United States, which is consistent with the paleontologic studies.…”

“…These tonalites could have provided part of the detritus to the accretionary area at The paleolatitude inferred by location PP1 satisfies the warm--temperate to subtropical climate required by the molluscan assemblages (Elder and Saul, 1993) and is also consistent with the latitude suggested by palynological studies Frederiksen (1990). It is too far north to support the paleomagnetic restoration suggested by Whidden et al (1998).…”