Pyrolysis-mass spectrometry and multivariate data analysis of Venezuela Basin sediments

Abstract

Pyrolysis-mass spectrometry was used to analyze the distribution of the organic material in the upper 40 cm of Venezuela Basin sediments. Box cores from three different provinces were obtained: pelagic (carbonate), turbidite and hemipelagic. With the aid of a relatively straightforward multivariate technique, the spectrographic data were investigated and the geological layers differentiated. These layers were in general agreement with those determined through the visual, X-ray and geochemical analyses of the same cores. The organic material in the pelagic core was poorly mixed, and a gradual alteration of this material with depth had taken place. The spectral pattern characteristic of the uppermost (youngest) layers was similar to those obtained from carbohydrate and/or fatty acid standards, whereas those from the deepest (oldest) layers resembled non-proteinaceous nitrogen containing material. The turbidite and pelagic layers in the turbidite core could be well differentiated according to their origin. A so-called iron-enriched layer in the core could readily be identified as consisting of pelagic rather than turbidite material. Analysis of the organic material from the hemipelagic core showed a strong change in the material at a depth of 12 cm.