ABSTRACT

The age and significance of sequence boundaries on Jurassic to Early Cretaceous rifted continental margins in three ocean basins have been documented. The margins are the Santos basin in the South Atlantic, the Grand Banks in the North Atlantic, and the Beaufort Sea in the Arctic Ocean. Large industry data bases were used for the interpretation of each area. Megasequence boundaries separate the major phases of basin evolution, for example syn-rift and post-rift. Boundaries developed with an average periodicity of 49 m.y. Sequence boundaries define the component parts of each megasequence and developed with a modal periodicity of 10-15 m.y. Out of 27 total boundary ages, most (16) are developed on just one margin. Only two possible age ranges overlap on all three margins. Eighty percent of the megasequence boundaries and 50% of the sequence boundaries show a direct causal connection with coeval faulting and/or folding. The rest of the boundaries appear as unstructured surfaces separating transgressive and/or regressive sedimentary wedges and are interpreted to result from changes in the rate of basin subsidence, sediment input, and long-term eustatic sea level. These data do not support theories advocating synchronous worldwide boundary development resulting from periodic, short-term falls in global eustatic sea level. Only in like basins of the same age, with identical subsidence and sediment input rates, are boundaries likely to develop synchronously. Hence, the concept of global synchroneity of sequence boundary development may well be an illusion created by the similarity in age of the majority of basins studied. As a result of this study, it seems wise discard the global approach to basin analysis.

First Page Preview

First page PDF preview
You do not currently have access to this article.