(Table 1) Oxygen and carbon isotopes and calcium carbonte of bulk carbonate at DSDP Hole 72-516F

A detailed oxygen and carbon isotope study of the upper Maestrichtian-lower Paleocene section of Hole 516F from the Rio Grande Rise reveals that large isotopic anomalies are clearly associated with the Cretaceous/Tertiary boundary. Across the Cretaceous/Tertiary boundary, the total carbonate content reaches a maximum exceeding 80% before rapidly decreasing in covariance with the carbon isotope record. This strong covariance between d13C and percent CaCO3 suggests either a significant reduction in primary productivity or a rapid shoaling of the calcium carbonate compensation depth. Importantly, the d13C record 2 Ma after the Cretaceous/Tertiary boundary remained depleted in 13C by at least 0.5 per mil compared to the late Maestrichtian.

Geochemical analyses of ODP Leg 135 samples

Statistical analysis of X-ray fluorescence data acquired during Leg 135 indicates that this instrument produces data of comparable precision to good land-based laboratories. We also examined contamination of certain elements caused by crushing during the use of the tungsten carbide apparatus. Although the concentrations of most elements are not altered during crushing, the powders prepared on the ship should not be used in subsequent studies where key elements of the investigation include W, Co, Ta, Pb, and low levels of Nb.

(Table 1) Heavy fraction minerals in bottom sediments of the Markov Deep, Mid-Atlantic Ridge

An additional ore field in the central part of the MARhas been discovered. Together with previously discovered Logachev (14°45'N) and Ashadze (12°58'N) ore fields, the new ore field constitutes a cluster with preliminarily estimated total ore reserve of >10 Mt, which is comparable with large continental massive sulfide deposits.