432
Fig. 19.7. Concentrations of
isorenieratene in a Black Sea
core covering the past
8000 years. Redrawn from
Repeta (1993)
~
}
10
20
30
S. Wakeham
Box core 5 (119 isorenieratene mg roc-I)
1
2
The highly unsaturated nature of carotenoid pigments such as isorenieratene renders these compounds remarkably reactive. In anoxic sediments, they preferentially
accumulate in macromolecular fractions, usually through loss of double and incorporation of inorganic sulphur (Sinninghe Damste et al. 1990; Wakeham et al. 1995).
Sulphurization (inter- and intra-molecular cross-linking between S and C) may provide a mechanism that protects otherwise labile molecules from degradation by
sequestration into a less reactive polar macromolecule. Chemical release of S-bound
{3,f3-carotane and octahydroisorenieratene (II and III, Fig. 19.6), fully and partially unsaturated derivatives of isorenieratene, by desulphurization of polar macromolecular
material extracted from Black Sea sediments produced a historical record (Sinninghe
Damste et al. 1993) similar to that derived from isorenieratene described above. Diagenesis and ultimately catagenesis of isorenieratene generates a wide range of aromatic and S-containing isoprenoids (Koopmans et al. 1996a) that can being applied
as indicators of photic zone anoxia in ancient environments. In the Messinian (upper
Miocene) evaporitic sequence of the Veno del Gesso Basin (Italy), distributions of Sbound isorenieratane (a derivative of isorenieratene) and the pentacyclic triterpenoid
gammacerane have been used to reconstruct the palaeo depositional environment
(Fig. 19.8). Gammacerane is thought to derive from anaerobic bacterivorous ciliates
living at or just below the chemocline and is an indicator of water column stratification; isotopic evidence suggests that the ciliates were feeding on sulphur bacteria that
produced isorenieratene (Sinninghe Damste et al. 1995b). In sequences where both
isorenieratane and gammacerane were present, the water column was stratified and
the chemocline was in the photic zone. When gammacerane was present but iso-
Fig. 19.7. Concentrations of
isorenieratene in a Black Sea
core covering the past
8000 years. Redrawn from
Repeta (1993)
~
}
10
20
30
S. Wakeham
Box core 5 (119 isorenieratene mg roc-I)
1
2
The highly unsaturated nature of carotenoid pigments such as isorenieratene renders these compounds remarkably reactive. In anoxic sediments, they preferentially
accumulate in macromolecular fractions, usually through loss of double and incorporation of inorganic sulphur (Sinninghe Damste et al. 1990; Wakeham et al. 1995).
Sulphurization (inter- and intra-molecular cross-linking between S and C) may provide a mechanism that protects otherwise labile molecules from degradation by
sequestration into a less reactive polar macromolecule. Chemical release of S-bound
{3,f3-carotane and octahydroisorenieratene (II and III, Fig. 19.6), fully and partially unsaturated derivatives of isorenieratene, by desulphurization of polar macromolecular
material extracted from Black Sea sediments produced a historical record (Sinninghe
Damste et al. 1993) similar to that derived from isorenieratene described above. Diagenesis and ultimately catagenesis of isorenieratene generates a wide range of aromatic and S-containing isoprenoids (Koopmans et al. 1996a) that can being applied
as indicators of photic zone anoxia in ancient environments. In the Messinian (upper
Miocene) evaporitic sequence of the Veno del Gesso Basin (Italy), distributions of Sbound isorenieratane (a derivative of isorenieratene) and the pentacyclic triterpenoid
gammacerane have been used to reconstruct the palaeo depositional environment
(Fig. 19.8). Gammacerane is thought to derive from anaerobic bacterivorous ciliates
living at or just below the chemocline and is an indicator of water column stratification; isotopic evidence suggests that the ciliates were feeding on sulphur bacteria that
produced isorenieratene (Sinninghe Damste et al. 1995b). In sequences where both
isorenieratane and gammacerane were present, the water column was stratified and
the chemocline was in the photic zone. When gammacerane was present but iso-