20. PALEOMAGNETIC CONSTRAINTS ON THE AGE OF LOWER CRETACEOUS CORES FROM DEEP SEA DRILLING PROJECT SITE 535, SOUTHEASTERN GULF OF MEXICO1

Cretaceous deep-water limestones from Site 535 have low intensities of magnetization, but stable inclinations (37.8° ±7.3) that can readily be isolated after demagnetization to 25 oersteds. The magnetic stratigraphy of the studied por-tion (sub-bottom depth 354.0-515.5 m) shows only two reverse samples, which may be the result of misorientation. The micropaleontological dating of this section as Albian to Hauterivian had implied that several reversals from the M anomaly sequence would be observed. The presence of only normally magnetized samples suggests instead that the studied portion is completely within the Cretaceous long normal zone (Santonian to Aptian). Thus the paleomagnetic data indicate that the micropaleontological dates are too old, a contention supported by postcruise ammonite studies