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Internal Consistency of Independently Correlated Paleomagnetic Sections and the Reliability of Their Correlation to the Global Magnetic Polarity Time Scale in Cases of Nonuniform Accumulation Rates

TALLING, PETER J., University of Southern California, Los Angeles, CA, R. S. HOBBS, Exxon Company USA, Houston, TX, D. W. BURBANK, University of Southern California, Los Angeles, CA, T. F. LAWTON, New Mexico State University, Las Cruces, NM, and S. P. LUND, University of Southern California, Los Angeles, CA

An 8 X 1 km panel of well-exposed strata along the eastern flank of the Gunnison Plateau, Central Utah, provides insight into Latest Cretaceous to early Tertiary deposition and its controls, notably a small backthrust that syntectonically rotates strata locally along the panel's base. Paleomagnetic stratigraphies provide a unique tool to produce well-constrained dates for the strata that otherwise is terrestrial, fossil deficient, and free of direct volcanic input. It also provides the possibility of detailed local and regional correlation in an area characterized by impressively abrupt facies changes.

Two magnetic sections were sampled at either end of the panel. Most samples were weak, good exposure; however, they allowed correlation of the sections using marker beds. This produces an independent test of the internal consistency and probable validity of the two magnetostratigraphies. Preliminary data suggest the lower parts of the sections correlate well.

Detailed sedimentologic and pedogenic investigations suggest there are significant accumulation-rate fluctuations present in the sections. Given (1) the discovered reversal pattern, (2) the lack of absolute time control, and (3) the observation that the relative duration of magnetozones may be distorted by unsteady sediment accumulation, correlations to the global magnetic polarity time scale may be tenuous. The extent to which detailed sedimentologic knowledge may constrain accumulation-rate fluctuations and help reduce the uncertainties in correlation will be examined.

 

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)