Ocean Drilling Program, United States

Coring in Hole 1213B on the south flank of Shatsky Rise recovered sedimentary rocks (chalk and claystone) of earliest Cretaceous (Berriasian) age. Because few samples of this age are available for the Pacific plate, this recovery provides an opportunity to use paleomagnetism to determine a value for the paleolatitude of the site and of the Pacific plate for Berriasian time. A total of 22 vertically oriented samples were measured, yielding consistent alternating-field demagnetization results and low paleoinclination values consistent with magnetization near the equator. Samples can be grouped by inclination sign to produce a magnetic stratigraphy. If negative inclinations are assumed to represent reversed polarity (i.e., the site was magnetized north of the equator), the result is consistent with the Berriasian reversal timescale, which contains more reversed polarity (Chrons M16r-M18r) than normal polarity. Likewise, the assumption of a Northern Hemisphere magnetization produces a paleoinclination (9.1 degrees +13.6 degrees /-14.2 degrees ; N = 17) and paleolatitude (4.6 degrees +7.2 degrees /-6.9 degrees ) that is consistent with independent Pacific paleomagnetic data of Late Jurassic and Early Cretaceous age. This paleolatitude implies that the Pacific Apparent Polar Wander Path trends southward from this time until the mid-Cretaceous.