CHANNELL, J.E.T., Department of Geology, University of Florida, Gainesville, FL; E. ERBA, Dipartimento di Scienze della Terra, Universita di Milano, Milano, Italy; and M. NAKANISHI and K. TAMAKI, Ocean Research Institute, University of Tokyo, Tokyo, Japan

ABSTRACT: Correlation of M-sequence Polarity Chrons to the Geologic Timescale in Italian Land Sections: Implications for the Constant Spreading Rate Timescale Model

The correlation of Late Jurassic and Early Cretaceous polarity chrons to nannofossil and calpionellid biostratigraphies in Italian land sections provides the basis for the correlation of M-sequence polarity chrons to geologic stage boundaries. This correlation is now well defined for the Tithonian to Aptian, having been replicated in many sections, but still poorly defined for pre-Tithonian time. The biostratigraphic resolution in Italian middle Jurassic sections has been recently improved by detailed nannofossil studies. This has resulted in improved biostratigraphic correlation of polarity chrons in this interval.

Comparison of the polarity patterns from Italian land sections with Hawaiian and Japanese block models derived from oceanic magnetic anomalies implies that the spreading rates and land section sedimentation rates were fairly constant for the Early Cretaceous. However, a spreading rate change in the Hawaiian lineations at about M12 is implied by comparison of Hawaiian block model with the Japanese block model and land section data.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.