Episodic post-rift subsidence of the United States Atlantic continental margin

Abstract

Sediment thickness, paleobathymetry, and chronostratigraphy from COST wells offshore from Georgia and New Jersey indicate periods of rapid subsidence superimposed on the slower thermal subsidence of the continental margin. Rapid subsidence occurred during the Coniacian-Santonian, the Eocene and, in the COST wells off New Jersey, since the end of early Miocene. Once the maximum effects of water and sediment loading, compaction, and thermal cooling are removed, the residual vertical movements caused by tectonic and sea-level fluctuations can be analyzed. Because no global sea-level change can account for all residual movements, we propose that tectonism, variously amplified by loading, is responsible for the observed episodes of rapid subsidence. Synchroneity of subsidence with sea-floor–spreading changes in the North Atlantic suggests a unified cause for these events. Recognition of episodic subsidence may have implications for fault timing, petroleum potential, and global sea-level effects on passive margins.