Magnetic polarity stratigraphy: Stochastic properties of data, sampling problems, and the evaluation of interpretations

A statistical model has been derived which can be used either to test the interpretation of a given magnetic stratigraphy or to make time estimates from the paleomagnetic data. The model is based on the presently accepted statistical properties of the earth's magnetic field and the stochastic nature of the paleomagnetic sampling process. Given knowledge of the number of paleomagnetic sites, the distribution of the sites, an estimate of the geologic time span sampled, and the mean length of the magnetic polarity zones, the expected success of the sampling program can be calculated and compared with its actual performance. In a number of test cases the theoretical results have agreed with realized results. The mean time span for polarity intervals in the late Neogene has been established from existing data at 120,000 years. Once the mean time span for polarity intervals has been established, estimates for stratigraphic time span can be made by means of the statistical model. Of three models studied, a time uniform sampling program is the most efficient for establishing a local magnetic polarity stratigraphy; the least efficient strategy is an exponential distribution of samples.

[1]  N. Opdyke,et al.  Magnetic polarity stratigraphy and ages of Siwalik group rocks of the potwar plateau, Pakistan , 1982 .

[2]  P. Gingerich,et al.  Magnetic Polarity Stratigraphy and Biostratigraphy of Paleocene and Lower Eocene Continental Deposits, Clark's Fork Basin, Wyoming , 1981, The Journal of Geology.

[3]  E. Lindsay,et al.  Magnetic polarity zonation and biostratigraphy of Late Cretaceous and Paleocene continental deposits, San Juan Basin, New Mexico , 1981 .

[4]  A. Cox.  A stochastic approach towards understanding the frequency and polarity bias of geomagnetic reversals , 1981 .

[5]  D. P. Elston,et al.  Reversal chronology from a 7.9‐ to 11.5‐M.Y.‐old volcanic sequence in central Arizona: Comparison with ocean floor polarity record , 1980 .

[6]  G. B. Dalrymple,et al.  Revised geomagnetic polarity time scale for the interval 0–5 m.y. B.P. , 1979 .

[7]  N. Opdyke,et al.  Magnetic polarity stratigraphy and vertebrate paleontology of the upper siwalik subgroup of northern Pakistan , 1979 .

[8]  A. Mussett,et al.  Preliminary observations on the palaeomagnetic stratigraphy of the area west of Lake Baringo, Kenya , 1978, Geological Society, London, Special Publications.

[9]  N. Watkins,et al.  Magnetostratigraphy of eastern Iceland , 1977 .

[10]  W. Lowrie,et al.  Upper Cretaceous–Paleocene magnetic stratigraphy at Gubbio, Italy V. Type section for the Late Cretaceous-Paleocene geomagnetic reversal time scale , 1977 .

[11]  W. Roggenthen,et al.  Upper Cretaceous–Paleocene magnetic stratigraphy at Gubbio, Italy IV. Upper Maastrichtian-Paleocene Magnetic Stratigraphy , 1977 .

[12]  N. Opdyke,et al.  The extension of the magnetic time scale in sediments of the central Pacific Ocean: Earth and Planet , 1974 .

[13]  M. Kono.  Geomagnetic polarity changes and the duration of volcanism in successive lava flows , 1973 .

[14]  N. Opdyke,et al.  Upper Miocene to Recent magnetic stratigraphy in deep-sea sediments , 1970 .

[15]  C. Harrison.  What is the true rate of reversals of the Earth's magnetic field?☆ , 1969 .

[16]  A. Cox.  Lengths of geomagnetic polarity intervals , 1968 .