Carbonate Dissolution on the Western Flank of the East Pacific Rise
The study of a series of closely spaced radiometrically dated cores down the west flank of the East Pacific Rise at 17°S reveals a very sharp elevation boundary separating cores which show little evidence of dissolution effects from those which have lost more than 95% of their CaCO<sub>3</sub> to dissolution. This transition occurs over an interval of no more than 80 meters and lies at about 3950 meters depth. Cores from below this boundary have a CaCO3-rich layer a few tens of centimeters thick at their tops. It is not possible to say definitely whether this zone results from a kinetic lag in dissolution or a brief downward shift in the elevation of the compensation level at the peak of the last glacial period. C14 dates do, however, preclude the possibility that this layer was deposited in postglacial time. Solution attack on the foraminiferal tests contained in this layer demonstrates that the compensation level now lies within a few meters of where it has on the average over the last several hundred thousand years.
Figures & Tables
This volume represents some of the papers presented at the SEPM Research Symposium GeologicHistory of the Oceans at the Annual Meeting, March 1971, in Houston, Texas. Knowledge of oceanic sediments has been acquired in two ways: 1) directly by sampling and observation, and 2) indirectly through seismic investigations. Until the past decade, direct sampling and observation techniques could only provide information on the surficial materials of the ocean floor. The development of the piston corer has permitted oceanographic vessels to sample the upper 20 meters, and more recently the upper 30 meters, of the ocean floor, but such cores rarely penetrate the Pleistocene and enter older sediments. Until recently, most knowledge of the deeper sedimentary materials in the ocean basins was obtained through seismic reflection studies. The purpose of this volume is to present a number of observations, ideas, interpretations, and speculations which will be of value in considering the meaning of the increasing volume of data from older deep sea deposits.