Northern Guam geospatial information server
About this map:
This geologic map is the result of work by Siegrist, H.G. and Reagan, M., under auspices of Water and Environmental Research Institute of the Western Pacific (WERI). It is an update and revision of the original Geologic Map of Guam by Tracey et al. (1964). Reinterpretation and revision of the map utilized a wealth of new data, including radiometric dating of selected volcanic rocks and a thin-section study of new limestone specimens. The work resulted in a single 1:50,000-scale map, as well as nine 1:24,000 scale maps, corresponding to the USGS 7.5-minute quadrangles that cover the island of Guam. The maps were published in early 2008 and are available for download from the WERI website (http://www.weriguam.org/locally-sponsored-research/guam-hydrologic-survey/page/geologic-maps.html). The 1:50,000 scale map shown here was scanned and georeferenced as Digital Raster Graphics (DRG).