Abstract: Phanerozoic Paleoenvironment and Lithofacies Maps of the Circum-Atlantic Margins

Ford, David; Jan Golonka; and Robert Pauken - Mobil, New Exploration and Producing Ventures

Thirty-one maps were constructed which depict the plate tectonic configuration, paleogeography and lithofacies for Phanerozoic time intervals from the latest Precambrian (Tommotian) through the Neogene (Messinian). These maps were constructed for the world comprising 300 continental plates and terranes, but are reprojected here to illustrate the circum-Atlantic margins. The relative position of the continents through time is largely derived from PLATES and PALEOMAP software.

Generally, the individual maps illustrate the conditions present during the maximum marine transgressions of a higher frequency cyclicity within the Sauk, Tippecanoe, Kaskaskia, Absaroka, Zuni, and Tejas megasequences of Sloss. The relative sea-level cyclicity, chronostratigraphy, and regional unconformities provide the basis to partition the higher frequency depositional cycles into subdivisions (supersequences) ranging from 11 to 39 my. Most of these time slices represent a single supersequence. However, some combine two supersequences since few data were found which clearly differentiate the individual time-slices. Data for the maps were derived from geologic reports, maps and stratigraphic columns and other paleogeographic interpretations regarding tectonics, basin formation, and deposition. The 20 mapped paleoenvironments are distinguished by colors: 3 separate colors for continental, erosional; 6 for continental, depositional; 4 for marginal marine; 7 for marine. The paleolithofacies are depicted by 21 patterns.

These maps illustrate the Phanerozoic geodynamic evolution of the Earth. The relationship of the continental configuration, lithofacies, tectonics and climate, from the time of the disassembly of Rodinia to the assembly and break-up of Pangea, is clearly depicted on this series of reconstructions. The distribution of lithofacies shows the cyclicity of climatic change from "greenhouse" to "icehouse" associated with continental assembly and disassembly. From a regional perspective, the facies in basins along the circum-Atlantic margin reflect various stages of rifting and passive margin development. The inversion caused by ridge pushing played an important role in the basin evolution and has influenced the distribution of lithofacies for appropriate time slices.

The power of the maps is realized in their application as an aid to the visualization of the relationships of regional basin development, sedimentation and erosion to the deposition of potential source-rock, reservoir and seals. Also, when combined with models of paleoclimate and wind-driven oceanic circulation, the paleogeographic maps can be used to predict the controls on the distribution of specific lithofacies within the basins.

AAPG Search and Discovery Article #90933©1998 ABGP/AAPG International Conference and Exhibition, Rio de Janeiro, Brazil