Foraminiferal lysocline

The foraminiferal lysocline (FL) was defined by Berger (1968) as the depth where the predominant type of foraminifera shifts in surface sediments, because of dissolution, from "soluble" to "resistant" species ( 50% change in ratio). To determine the depth of the foraminiferal lysocline, three conditions must be met (Parker and Berger, 1971) ... 

There must be sufficient topographic relief so that sediment samples from both above and below the foraminiferal lysocline can be obtained. 

Figure 7. The depth distribution of the Ro and calcite saturation levels, the foraminiferal lysocline and the calcium carbonate compensation depth in the Western and Eastern Atlantic Ocean (after Ref. 40)...

Figure 9. Relationship between the distance from equilibrium (1 — Q) of seawater with respect to calcite and the amount of dissolution which is estimated to have occurred. (A) Adelseck s (11) experimentally determined amount of dissolution (B) Berger s (12) minimum loss estimate for the amount of dissolution at the Ro level and foraminiferal lysocline.

The distribution patterns of coccoliths and foraminifera differ significantly in deep-sea sediments (Schneidermann, 1973 Roth et al, 1975). In most sediments the more easily dissolved coccoliths are missing. Even in areas where the overlying water is supersaturated with respect to calcite (e.g., 3,000 m in the Atlantic Ocean Schneidermann, 1973), significant dissolution of coccoliths has been observed. Solution-resistant coccoliths, however, may survive in sediments in which all foraminiferal tests have been dissolved. Schneidermann (1973) used these characteristics to create additional subdivisions of the region near the CCD, and Roth et al. (1975) emphasized that coccolith and foraminifera solution indices can be used in a complementary manner. Coccoliths are good indicators of dissolution above the lysocline, whereas foraminifera are better indicators of dissolution below the lysochne. 

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