Paleogeography Applied to Exploration: ABSTRACT

Abstract

Paleogeography, the mapping of seas, shorelines, rivers, deltas etc., at some time in the past, is a valuable tool in exploring for reservoir rocks in the Cretaceous section of the Rocky Mountain region. Paleogeographic mapping is accomplished by means of stratigraphic studies to determine two essential factors--environment of deposition and correlation. Classification of the Rocky Mountain Cretaceous rocks into four broad facies (Inland, Shoreline, Sandy Offshore, and Shaly Offshore) is a useful device which aids in the study of the complex intertonguing of varying lithologies. An understanding of shoreline movements (transgression and regression) is the key to correlation in the Cretaceous section. The End_Page 112------------------------------ Cretaceous sequence of most of the Rocky Mountain region can be considered to be the result of superimposition of many paleogeographic settings. Analysis of a hypothetical time-stratigraphic unit shows the variation in location, shape, and size of potential reservoir rocks deposited in various paleogeographic locations. In one example, correlation of an inland facies and an offshore facies suggests an intervening shoreline facies. Paleogeographic considerations are fundamental in stratigraphic analysis and consequently paleogeography is the base on which stratigraphic exploration is built. End_of_Article - Last_Page 113------------