ABSTRACT: A Method of Constructing Chronostratigraphic Diagrams (Wheeler Diagrams) from Well Logs: An Example from the San Juan Basin, New Mexico

John W. Robinson, David W. Valasek

Conversion of a well log section into a chronostratigraphic diagram can be one of the most important steps an explorationist can take in understanding complex interrelationships of time and space on the geologic record. To this end, a method has been devised that allows a simple check of the degree to which chronostratigraphy has been employed. A depositional dip well log section is constructed using a

datum horizon correlated along the section that represents an approximate regional time significant surface. Detailed correlation of third-order to fourth-order (Exxon Scale) progradational cycles used in this example portray a regressive to transgressive depositional sequence. An interpretation of facies distribution of individual timebounded units is constructed on an overlay of the original log section. Finally, a graphical depiction of the time/space domain is generated by sequentially transferring the lithostratigraphic interpretation onto a Wheeler Diagram with each progradational cycle hung from its top time boundary. If the proper chronostratigraphic framework was employed, facies will rise as you shift basinward along the section. If the facies do not rise, alternative correl tions must be made or alternative interpretations of facies architecture must be considered. An example is given from the Gallup Sandstone (Coniacian) of the San Juan basin, New Mexico.

AAPG Search and Discovery Article #91002©1990 AAPG Rocky Mountain Section Meeting, Denver, Colorado, September 16-19, 1990