GEOLOGIC MAP OF THE NORTH CASCADES, WASHINGTON: PROGRESS REPORT ON A COMPILATION

Comprehending the geology of a large and complex area has always been problematic for the earth scientist as well as the layman. As our detailed knowledge increases for specific areas, the integration of geologic units and structural interpretations over a broad region becomes more and more confusing to all but the connoisseur. Smaller scale regional compilations can help. With the coming of the digital age, compilation of geology has become less onerous. We have compiled digital data available for 8 1:100,000-scale geologic maps between 120° and 122° west longitude and 47° and 48° north latitude for portrayal at 1:200,000. We constructed a regional stratigraphic scheme that is expressed in a database with two tables: source-map units and regional units. Correlations are expressed as the relation (in a database sense) between the two tables. The regional stratigraphy is strongly hierarchical; by moving to a higher level in the hierarchy we have grouped related units, doing most of the generalization work required by the scale change. We have draped the geology over a shaded-relief model of the North Cascades providing a useful visual base which we have enhanced with digital cultural data edited and adjusted for the scale. In order to make this map of interest to the specialist and non-specialist, we are writing two map explanations. A conventional description of map units will be lithologically concise, but weighted with references to the original data sources. A second explanation will expand the description of map units, simplifying geologic jargon and explaining the formation of the units and their place in the geologic story.