Most sediments have been developed in association with some forms of biological activity. Thus the changes in distribution and the corresponding function of the organic matter in solubilization, complex formation, translocation, and subsequent recrystallization of secondary minerals must be considered in studying diagenetic processes during the post-deposition interval. An undisturbed core 120 ft long was obtained from the fresh-water environment of the Atchafalaya basin and studied. A deep boring from a brackish environment of the lower Mississippi delta was included for comparison. The organic matter in the sediments was hydrolyzed with 6N HCl for 12 hr; the clear hydrolysates separated were neutralized with NaOH. The soluble forms of total hydrolyzable-N, ^agr-amino ac d-N, hexosamine-N, and NH⁺₄-N were determined quantitatively by a simple micro-steam distillation technique. The results showed that, in the Atchafalaya basin, the ^agr-amino acid-N was higher in lacustrine environments (145 µg/g at 30-ft and 81 µg/g at 120-ft depths) and lower in well-drained swamps (68 µg/g at 67-ft and 49 µg/g at 96-ft depths). The distribution of hexosamine-N ranged from 95 µg/g at 30-ft to 36 µg/g at 120-ft depths. In the lower Mississippi delta core, the ^agr-amino acid-N decreased sharply from 220 µg/g at the surface of a brackish-marsh environment to only 20 µg/g in a prodelta environment at a depth of 100

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ft, whereas the hexosamine-N increased from 130 µg/g to 380 µg/g at the same levels. This suggests that the ^agr-amino acid and hexosamine compounds were well preserved even to 100-ft depth and that their distribution was related to the initial environments of deposition. It was also found that in the fresh-water environment the percent organic-C was nearly parallel with the percent of < 5µ fine clay and that the C/N ratio was related closely to the percent of total cementing minerals (such as FeCo₃, MnCO₃, CaCO₃, Fe- and Mn-oxides) which accumulated with depth. In addition, organic-N was found in the nodules. This demonstrates one of the important roles of soluble organic matter in the translocation or diffusion and subsequent redepo ition or recrystallization of various minerals during the diagenetic process.

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