TEMPORAL CHANGES IN THE DISTRIBUTION OF C(33)CYCLOHEPTENODPEP AND 17-NOR C(30)DPEP IN ROCKS

C33 cyclohepteno DPEP is a common component in the porphyrin assemblag es of certain thermally immature marine rocks. This compound is unstab le and decomposes on standing. 17-nor C30 DPEP, a diagenetic product o f chlorophyll c, is present in minor amounts in the vanadyl porphyrin fractions of many marine sediments. It is the major porphyrin within c ertain sections of Monterey Formation. This unusual occurrence of a la rge proportion of this compound within certain sections of the Montere y Formation may indicate a change in the depositional environment, whi ch favoured the loss of the acrylic acid chain of chlorophyll c. It ma y also indicate blooms of certain algae rich in chlorophyll c.