Skip to main content


Amy K Gilmer

Research Geologist

Geosciences and Environmental Change Science Center

Office Phone: 303-236-1636
Fax: 303-236-5349
ORCID: 0000-0001-5038-8136

Supervisor: Margaret E Berry
USGS Geochron is a database of geochronological and thermochronological dates and data. The data set contains published ages, dates, analytical information, sample metadata including location, and source citations. The following analytical techniques are represented in the data set: 40Ar/39Ar, K-Ar, U-Th-Pb, Sm-Nd, Rb-Sr, Lu-Hf, fission track, and luminescence. This data set incorporates data previously hosted in the National Geochronological Database (Sloan and others, 2003), as well as data from published journal articles and ScienceBase data releases. These data are primarily from the United States, but data from other parts of the world are also included.
The dataset includes whole-rock geochemistry, phenocryst/mineral trace element compositions, zircon U–Pb geochronology, and zircon in situ Lu–Hf isotopes for intrusions associated with the Oligocene Platoro caldera complex of the San Juan volcanic locus in Colorado features numerous exposed plutons, both within the caldera and outside its margins, enabling investigation of the timing and evolution of postcaldera magmatism. Intrusion and , coupled with new document distinct pulses of magma derived from different depths beneath the caldera complex. Fourteen intrusions, the Chiquito Peak Tuff, and the dacite of Fisher Gulch were dated, showing intrusive magmatism began after the 28.8 Ma-eruption of the Chiquito Peak...
Geochronological data provide essential information necessary for understanding the timing of geologic processes and events, as well as quantifying rates and timescales key to geologic mapping, mineral and energy resource and hazard assessments. The USGS’s National Geochronological Database (NGDB) contains over 30,000 radiometric ages, but no formal update has occurred in over 20 years. This project is developing a database with a web-based user interface and sustainable workflow to host all USGS-generated geochronological data. This new geochronological database consists of (1) data from the existing NGDB; (2) published literature data generated by the USGS; and (3) more recent data extracted from ScienceBase...
This U.S. Geological Survey (USGS) data release provides U-Pb zircon data and geochronology for Proterozoic rocks in the Needle Mountains of southwestern Colorado and for Proterozoic rocks sampled from drill cores from Wyoming, Montana, and Nebraska. Samples from the Needle Mountains were collected in order to constrain the polyphase tectonic evolution of the area. Drill core samples are part of a larger characterization of the age and geochemical character of basement terranes in the United States.
This geologic map depicts and briefly describes geologic units underlying Petroglyph National Monument and immediately adjacent areas in Bernalillo County, New Mexico. The Monument is underlain dominantly by Quaternary basalts of the Albuquerque Volcanoes volcanic field, a series of basin-filling volcanic flows and associated vents from a monogenetic volcanic highland along the eastern margin of the Llano de Albuquerque. This compilation builds on data of previously published geologic maps and reports but includes new interpretive synthesis of volcanic stratigraphy and a unified representation of Quaternary surficial deposits overlying volcanic deposits within the Monument and areas immediately adjacent. This geologic...
View more...
ScienceBase brings together the best information it can find about USGS researchers and offices to show connections to publications, projects, and data. We are still working to improve this process and information is by no means complete. If you don't see everything you know is associated with you, a colleague, or your office, please be patient while we work to connect the dots. Feel free to contact