The geological evolution of the tropical Atlantic basin over the past 170 million years is linked to immense stratigraphic and climatic change. The pattern, and development, of stratigraphic change needs to be understood for sensible exploitation of the petroleum and mineral resources created in the basin over this time. Many of these changes were primarily controlled by variations in the upper ocean circulation with particular emphasis on the link between palaeo-upwelling and oceanic productivity. Thus, much effort is currently being devoted to quantifying the extent, timing, and strength of palaeo-upwelling.
Recent palaeogeographic and palaeoclimatic reconstructions are used to force a reduced-gravity upper ocean model for selected time slices, covering the period from the middle Jurassic to the present day. This numerical model has been validated by comparison between modern upwelling predictions and satellitederived estimates of productivity. The simulated circulation, through quantitative model to borehole data comparison, enables us to address a number of issues in the sedimentary and climatic record. Major examples to be quantified include: 1) the likely time of initiation and strength of coastal upwelling along the African and South American coasts, 2) the relative importance of basin stagnation with oceanic anoxic events, versus upwelling with primary productivity, for the creation of the extensive black shale deposits, 3) the applicability of palaeocean modelling to source rock determination and hence possible palaeobathymetric reconstruction by comparing model-upwelling with organic-rich deposits and faunal evidence.
AAPG Search and Discovery Article #90925©1999 AAPG Foundation Grants-in-Aid