Mass-balanced paleogeographic reconstructions

Paleogeography, paleotopography, and paleobathymetry of a closed erosion-depositional system can be reconstructed by restoring sedimentary masses to elevated surfaces in a drainage basin based on the inverse of present erosion equations and adjusting for isostasy, sea level changes, sediment compaction, and thermal subsidence. The erosion-deposition history of the northwestern Gulf of Mexico margin and its western-central North American source area during the Cenozoic is used to explore the sensitivity of mass balance reconstructions, and changes in assumptions concerning erosion rate parameters and sea level. Analysis of the distributions of sedimentary material and mass-balanced paleogeographic reconstructions of the study area indicate the following specific results: 1) most of the Pleistocene sediment in the Gulf of Mexico is not of glacial origin but is derived from the high plains and reflects uplift of the Rocky Mountains and High Plains since the Late Pliocene; and 2) paleoshorelines predicted from mass-balanced reconstructions using theHaq et al. (1987) global sea level curve do not match the shoreline indicated by sedimentary sequences and suggest that the amplitude of sea level changes in the Gulf coast is between one-fourth and three-fourths, most likely one-half, that of the published eustatic sea level curve