HR: 1340h
AN: T13A-1131    [Abstracts]
TI: A Robust Compilation of the Pacific M-anomaly Geomagnetic Polarity Sequence
AU: Sager, W W
EM: wsager@tamu.edu
AF: Department of Oceanography, Texas A&M University, College Station, TX 77843, United States
AU: * Tominaga, M
EM: mtominaga@ocean.tamu.edu
AF: Department of Oceanography, Texas A&M University, College Station, TX 77843, United States
AB: The current M-anomaly geomagnetic polarity time scale (GPTS) is mainly based on the Hawaiian lineation set in the Pacific Ocean. Furthermore, existing studies of this GPTS rely on a relatively small number of magnetic profiles. This limited basis is contrary to the fact that the GPTS is assumed to represent a global reversal record. Compiling an anomaly record from a larger array of magnetic profiles from all ocean basins is desirable because consistency and repeatability support the global nature of each polarity reversal. We present a new compilation of the M-anomaly GPTS derived from a Pacific-wide set of Late Jurassic to Early Cretaceous anomalies as a first step toward a global model. The anomalies were collected from three lineation sets (Hawaiian, Japanese, and Phoenix) across the western Pacific basin and resampled for subsequent modeling. Both inverse and forward calculations were applied to estimate polarity reversal boundaries. Polarity block models were established within each lineation set separately to allow examination of variability among the different lineation sets. Subsequently, a composite polarity block model was constructed by normalizing and averaging the block models from the three lineation groups. The large number of magnetic profiles used in this study allows us to compute errors and test coherence in anomaly correlations. Consistency and repeatability of most of Mesozoic anomalies are excellent amongst the three lineation sets, except for the pre-M25 anomalies. The difficulties with pre-M25 anomaly correlations raise the question whether we can construct a reliable GPTS model for this time period. Owing to lack of reliable direct dating of the M-anomalies on ocean crust, the composite model has few age calibration points. Nevertheless, the polarity block models from this study are a better foundation for future GPTS models. Our compilation represents a wider and statistically more robust analysis of anomalies, giving a more reliable record of changes in the Earth's geomagnetic field.
DE: 1517 Magnetic anomalies: modeling and interpretation
DE: 1520 Magnetostratigraphy
DE: 3005 Marine magnetics and paleomagnetics (1550)
DE: 8157 Plate motions: past (3040)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting