THE ALASKA GEOLOGIC MAP DATABASE – A MODEL FOR INTEGRATING MULTIPLE GEOLOGIC MAPS

As part of a national effort, the National Surveys and Analysis project (or NSA), we created a set of integrated spatial and non-spatial geologic databases as an analytical tool. Our focus was to facilitate mineral resource assessment and tectonic analysis. Published in 2015, the geologic map of Alaska is one of several derivative publications from these databases.

From the beginning, we recognized the integration of multiple disparate Alaska quadrangle-based maps was going to require a database design that integrates similar map units. To this end, we created a non-spatial database that contained the map unit descriptions from each source map (both bedrock and surficial maps). Each map unit description was assigned attributes to characterize it as originally described and to link it to other correlated or similar map units. Additionally, we included related tables of specific map unit attributes (lithology and age) to foster analysis of the map data for a variety of purposes. Ultimately, nearly 20,000 map unit descriptions from hundreds of published maps were compiled into about 1,500 regional units. Concurrently, spatial databases were being created of each source map using a common structure and containing attributes that connected these databases back to both their original descriptions and newly defined regional units. Maps could then be created showing either the original source geology or the regional geology using the same dataset. Designed to be a “living” database, an updated version 2 of the Alaska map is in preparation, reflecting new mapping and revised interpretations.

Two additional efforts to demonstrate the flexibility and utility of the design were undertaken. The regional units were linked to the published geologic map of Yukon, Canada, allowing a common presentation of the mapping and facilitating analysis of that map also. A bigger test was to apply the data structure and common related tables (lithology and age) to the geology of the Greater Antilles in the Caribbean. Starting with the same regional units table, we were able to incorporate the Greater Antilles map units by adding additional regional units where needed. Some units are common across all of these maps (Eocene granite, for example), whereas other map units are regionally unique.