Continental drift and the global pattern of sedimentation

The breakup of Pangaea through rifting and separation of the continents has special implications for the global pattern of sedimentation. The important initial conditions of Pangaea are area, elevation, the nature of the drainage and climate. The development of interior uplifts associated with rifting caused significant reorganization of drainage systems. Rifting and continental breakup result in unique sediment sequences on passive margins. The initial rift valleys were probably occupied by stratified fresh water lakes due to the equable Mesozoic climate, and during this phase might have accumulated about 7.5×10²¹ g of organic carbon; this would be 14% of the earth's total organic carbon concentrated on only 0.3% of the earth's surface. The sediments rich in organic carbon are expected to be typically overlain by evaporites. Sedimentation on the continental shelf is a complex interplay of thermal subsidence, sea level changes, sediment supply and isostatic adjustment. Beyond the shelf break, sedimentation rates in the world ocean appear to change significantly with time; during the Aptian-Albian, Campanian-Maastrichtian, Middle Eocene and Late Miocene-Quaternary overall sedimentation rates were about an order of magnitude higher than during the intervening periods. This variation is likely to be related to changing sediment supply responding to changes in sea level.