Published 1995 as part of Studies in Geology 40
Copyright © 1995 The American Association of Petroleum Geologists.  All Rights Reserved.
 

The distribution of organic carbon in marine sediments is commonly characterized by cyclicity at different time scales. A detailed analysis of such cyclicity in three case studies of Liassic and Kimmeridgian age in England and of Cenomanian age in the northwestern Atlantic Ocean shows that specific processes playing at different time scales control the storage of organic matter. Two scales are distinguished: (1) large-scale trends (>3 m.y., 2nd- and 3rd-order cycles) are caused by plate tectonics affecting paleogeography and topography, long-term eustatic sea level, and climatic changes ("ice-house" and "green-house"); they define the storage of organic matter worldwide by influencing productivity and ventilation of deep water; and (2) small-scale trends (<3 m.y., 4th- and 5th-order cycles) are caused by orbitally induced high-frequency glacio-eustatic and other oceanographic and/or climatic changes. If general conditions are favorable, the impact of these changes is a high-frequency signal of oxygenation/dilution cycles, whose particular expression strongly depends on the local sedimentary environment. 

A consequence of the orbitally induced climatic/oceanographic control of high-frequency sedimentary cycles is that it has a regional (to worldwide)