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Journal Article
Pringle, Staudigel H, Gee J.  1991.  Jasper Seamount: Seven million years of volcanism. Geology. 19:364-368.   10.1130/0091-7613(1991)019<0364:jssmyo>2.3.co;2   AbstractWebsite

Jasper Seamount is a young, mid-sized (690 km super(3)) oceanic intraplate volcano located abut 500 km west-southwest of San Diego, California. Reliable super(40)Ar/ super(39)Ar age data were obtained for several milligram-sized samples of 4 to 10 Ma plagioclase by using a defocused laser beam to clean the samples before fusion. Gee and Staudigel suggested that Jasper Seamount consists of a transitional to tholeiitic shield volcano formed by flank transitional series lavas, overlain by flank alkalic series lavas and summit alkalic series lavas. Twenty-nine individual super(40)Ar/ super(39)Ar laser fusion analyses on nine samples confirm the stratigraphy: 10.3-10.0 Ma for the flank transitional series, 8.7-7.5 Ma for the flank alkalic series, and 4.8-4.1 Ma for the summit alkalic series. The alkalinity of the lavas clearly increases with time, and there appear to be 1 to 3 m.y. hiatuses between each series. The age data are consistent with the complex magnetic anomaly of Jasper; however, the dominant reversed polarity inferred from the anomaly suggests that most of the seamount formed at ca. 11 Ma, prior to the onset of Chron C5N.

Gee, J, Varga R, Gallet Y, Staudigel H.  1993.  Reversed-polarity overprint in dikes from the Troodos ophiolite: Implications for the timing of alteration and extension. Geology. 21:849-852.: Geological Society of America   10.1130/0091-7613(1993)021<0849:rpoidf>2.3.co;2   AbstractWebsite

Paleomagnetic analysis of dikes from the Troodos ophiolite indicates the presence of a well-defined reversed-polarity overprint, an unexpected result given the currently accepted Cenomanian-Turonian age (88-91 Ma) suggesting formation during the Cretaceous Long Normal Period (83-118 Ma). This reversed- polarity component was apparently acquired prior to tectonic tilting of the dikes, implying that extensional tectonism occurred significantly (>5 m.y.) off axis. Alternatively, the paleomagnetic and field observations may be reconciled if parts of the ophiolite are significantly younger.