Abstract

The building blocks for scientific endeavors such as Geology, Geochemistry and Oceanography are the observations resulting from field work. These field observations or experiences have given us the basic descriptions upon which to work. The descriptions themselves, however, are not the end product. We wish to explain how such an arrangement is possible; we strive to determine the mechanism or mechanisms which may be operative thereby giving us the product which has been described. One possible method available to us in our search for representative factual information on these mechanisms is that of laboratory experimentation.

The specific problem to be discussed concerns the inclusion of organic material into marine sediments. Both sedimentary minerals and organic material are found in the sea, the water column representing a temporary place of residence. The sediment particles pass through the water column to become a part of the marine bottom deposits. The organic material has three routes to follow; it can be incorporated into the living organisms of the sea, be decomposed into its ultimate products, or find its way into the bottom deposits. The point of interest here is the latter, and there are two basic ways for sea borne organic material to become a part of the deposits, by settling out as discrete particles or by being removed from the dissolved state in an association with organic particles. The settling of discrete particles is readily observed by fragmental inclusions in deposits. The association of dissolved organic compounds with minerals in the sea has been concluded but hardly demonstrated. Likewise, the mechanism for such an association has been inferred but remains essentially unsubstanciated.

Because of the complexity of the mineral-organic association in an aqueous system and the difficulty or impossibility of investigating such an association in the sea itself, controlled laboratory experiments represent one possible means of approach. The investigation to be discussed revolves about the ecological and geochemical significance of organic material in sedimentary deposits and is based on the use of radioactive tracer methods devised for elucidating the mechanisms of mineral-organic associations.

The minerals used in these studies were montomorillonite, illite, kaolinite and quartz. The specific organic compounds, all reported to exist in sea water or natural deposits, include carbohydrates, monoamino-di carboxylic acids and monoamino-monocarboxylic acids. The effects of organic and mineral concentration and species, chlornity, temperature, settling rate and pH were all considered.

The results of this preliminary experimental program demonstrate that minerals settling through a water column remove dissolved organic compounds from solution and incorporate them into the resulting sediment deposits. This association is not a random system, but follows a definite differential selection process primarily dependent upon mineral types, i. e. "active surface area," and molecular weight, structure and functional groups of the organic compound. Chlorinity, temperature, settling rates, and pH have secondary effects upon the system. The results cannot be explained on the basis of a classical adsorption phenomona, but rather indicate the development of a partially non reversable complex clay organic gel.