Reports

Southern Hemisphere Origin of the Cretaceous Laytonville Limestone of California

Science  21 Mar 1986:
Vol. 231, Issue 4744, pp. 1425-1428
DOI: 10.1126/science.231.4744.1425

Abstract

New paleomagnetic, paleontologic, and stratigraphic data from outcrops of the Laytonville Limestone (101 to 88 million years old) support a Southern Hemisphere origin. A paleomagnetic megaconglomerate test is statistically significant and suggests magnetization at 14° ± 5° south, predating Late Cretaceous to Eocene (70 to 50 million years ago) accretion. Rapid Kula plate movement or the existence and demise of a now vanished oceanic plate (or both) are required to accommodate the greater than 50° of poleward displacement implied by the paleomagnetic data. This rapid motion brings into question the validity of a "speed limit" for absolute plate velocity based on present-day plate motions.

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