SECT. 3] BASIN SEDIIVrENTATION AND DIAGENESIS 593 



hand, has black mud in the stagnant zone (Redfield, 1958) while the Black Sea 

 appears to have predominantly gray sediments. The fine sediments in the south- 

 ern California basins are generally an olive green color, although the Santa 

 Monica basin, where sedimentation is most rapid, has dark gray-green clays. 



No satisfactory explanation has yet been given for the color differences, and 

 it is the author's opinion that many factors are involved. Those of significance 

 may be the kinds and proportion of clay minerals, such as illite and chlorite, 

 and the presence of higlily pigmented organic matter, ferrous salts, large 

 quantities of CaCOs, hydrotroilite and pjTite. Of great importance may be the 

 total amount of iron available, either in solution or particulate. A high iron 

 content will bind the H2S very rapidly to form black hydrotroilite. It would be 

 expected that high iron would be related to areas with great run-off and perhaps 

 a high content of volcanic rocks. We should, therefore, expect the color to be 

 darker closer to the soiu"ce. Estuaries, lagoons and marshes fed by streams 

 usually contain black sediments. 



f. Rate of deposition 



The rate of sedimentation in basins is dependent on distance from sources, 

 type and amount of material delivered into the basin and on the agents 

 of transport. Many of the older data are not reliable because of uncertainties 

 in the age determinations for the sediments. Other values were based on 

 estimates of annual supply by rivers, run-off and wave erosions. Many of the 

 earlier results were given in thickness accumulated per year; this has the added 

 problem of neglecting compaction. 



The most reliable work on relative rates so far published was carried out by 

 Emery (1960) on the southern Cahfornia basins. The results. Fig. 3, show a 

 decrease in rate with distance from shore of all sediment components studied 

 with the exception of calcium carbonate. These rates are given in mg/cm^/year 

 for a column of sediment neglecting the turbidity-current deposits, and are 

 based on i^Q -age-dating techniques. 



3. Diagenesis in Sediments 



A . Types of Organic Matter 



The extensive work of Trask (1932, 1939) has contributed much to our 

 knowledge of the organic content of various marine sediments. The composition 

 of organic matter is different in different environments and also changes with 

 depth of burial. Because of the complexities involved, no agreement has yet 

 been reached as to what the average carbon content of the organic matter in 

 sediment is. Emery and Rittenberg (1952) suggested that for southern Cali- 

 fornia basins an average organic content of 1.7 times the organic carbon best 

 fitted the observed data. 



The carbon to nitrogen ratio also varies with sediment type, with depth of 

 burial and with the analytical procedure. Trask obtained an average C/N of 8.0 

 while Emery and Rittenberg found a C/N of 13.0. The uncertainty of the 



