A two part study was carried out on the North Atlantic (Blake-Bahama region) Jurassic magnetic quiet zone sea floor spreading record. In the first part of the study, Talwani models of oceanic Layer 2a basalt were compared to on shipboard and MAGSAT data profiles. Three basic models were considered: a rapid reversal model based on the Handschumacher and Gettrust (1986) Jurassic polarity times cale, normal polarity, and reversed polarity. All models were considered at various intensities. In the second part of the study, paleointensity determinations were made on layer 2a basalt samples from Deep Sea Drilling Project (DSDP) Site 417D and Site 534. Site 417D is located on M-sequence anomaly Mo and Site 534 is located in the Jurassic magnetic quiet zone. Thellier (1977) and Shaw et al., (1984) methods were used to determine ancient field strength. Results of the modeling indicated that the Jurassic quiet zone is best modeled by constant normal polarity and 25 to 50% of M-sequence intensity. M-sequence anomalies M24 and M25 were best modeled by an envelope of decreasing intensity up to 75% from M24 to the Jurassic quiet zone. Thermal and alternating field demagnetization of basalt samples indicated that there is no significant difference in viscous remanent magnetization between the Cretaceous and Jurassic rocks. Site 417D samples (Cretaceous) had more complex magnetizations than Site 534 samples, indicating less stable magnetization. Paleointensity values for samples with Jurassic magnetizations were up to 50% less intense than the non-Jurassic magnetizations. However, paleointensities were very high and scattered. Too few results were obtained to conclude firmly the Jurassic field was lower in intensity. Because only one sample (130-2) exhibited an early Cretaceous magnetization, no conclusions were drawn about the Cretaceous field.

West: -80.0000 East: 20.0000 North: 75.0000 South: .0000

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Provider: SEDIS Publication Catalogue

Data set link: http://sedis.iodp.org/pub-catalogue/index.php?id=1992-060124 (c.f. for more detailed metadata)

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