GM-86 — Geologic Map of the Navajo Peak 7.5-Minute Quadrangle, Rio Arriba County, New Mexico

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By: Groughnour, Rebecca L.; Kelley, Shari A.; Aby, Scott B.; Krupnick, Jon M., 2026, scale 1:24,000

Geologic map of the Navajo Peak Quadrangle, Chama Basin, north-central New Mexico

The Navajo Peak Quadrangle is located in the Chama Basin of north-central New Mexico. The Rio Chama and the Chama River Canyon Wilderness bisect the map area, where the river has cut a deep, rugged canyon into gently folded Triassic-to-Cretaceous sedimentary rocks. Along the western boundary, the eastern edge of the Gallina Mountain dome exposes Permian to Cretaceous rocks dipping 20–60° east. Quaternary terrace, piedmont, and landslide deposits record the history of the Rio Chama’s downcutting.

A notable discovery during mapping was the identification of rounded lag gravels discontinuously capping the highest mesa surfaces adjacent to the Rio Chama. These deposits generally include clasts of Proterozoic quartzite, metaconglomerate, granite, gneiss, schist, and pegmatite ranging from 1–30 cm in diameter. One deposit 335 m above the river — between Dark Canyon and Mine Canyon — also contains andesitic and basaltic clasts. The source of these gravels remains an active research question with implications for understanding Quaternary landscape evolution along the Rio Chama.

The correlation of the red rock unit between the Jurassic Todilto Formation and the Westwater Canyon Member of the Morrison Formation has long been debated — variously mapped as the basal Recapture Member or tied to the older Summerville Formation and Bluff Sandstone of Utah. Notably, Allosaurus tracks are preserved in this unit in Dark Canyon. The unit transitions from well-cemented stacked channel sandstones in the north to siltier, weakly cemented sandstones to the south, possibly reflecting a shift from the sandy Salt Wash megafan member to the floodplain Recapture member of the Morrison Formation. This facies change may also affect groundwater aquifer productivity in the unit.

https://doi.org/10.58799/GM-86

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File Name	Size	Last Modified
GM-86_NavajoPeak.pdf	27.48 MB	05/01/2026 03:56:27 PM
GM-86_NavajoPeak.ppkx	27.23 MB	04/06/2026 10:49:53 AM
GM-86_NavajoPeak_Report.pdf	2.11 MB	05/01/2026 03:56:34 PM

Notes:

Geologic mapping of this and other 7½-minute quadrangles in New Mexico is being cooperatively funded by the USGS through the STATEMAP program and with matching funds from the Bureau. For a list of quadrangles in this series, please visit the Open-file Geologic Map (OF-GM) page or try our search page for geologic maps of any series.

These maps are open-filed as they become available, initially as PDF files of scans of the hand-drawn linework and later as full color maps and GIS products. Following cartographic production and editorial review, these maps may be published within our GM-series or be included in larger maps of regions of particular interest.

These maps are subject to frequent revisions and may be unavailable when being revised. Map Reference dates show the time of initial compilation; Map Revision dates, when given, indicate the most current version of the map; Last Modified dates for files may not accurately reflect the time the map was last revised.

FONTS
- Many of our Geologic Maps use the USGS FGDC Fonts. If you are accessing the GIS files, please download these fonts and install them on your computer before opening the GIS Project. This will ensure you get the correct symbology for the features in the map.

GeMS
- Additionally many of our Geologic Maps are in the USGS GeMS Data Model. There are a few places where the NMBGMR varies from GeMS. These variations are as follows:
  - This is an Open-File Geologic Map and has not undergone the highest level of external peer review of publication so that we can get the geologic information out in as timely a manner as possible. This geologic map is presented “as is.”
  - The New Mexico Bureau of Geology and Mineral Resources (NMBGMR) has created this GeMS compliant geodatabase or as near as we can get from our understanding and needs.
  - FGDC_Symbols data table added to geodatabase. This is used to provide consistent descriptions of the symbols used in the database and their definition and for building the Explanation of Map Units legend.
  - In the DMU the Symbol field is used as a complete legend description of each map unit and heading, and as such, is a combination of the HierarchKey, ParagraphStyle, MapUnit, FullName, and Description fields so that the legend can be made in the layout with all of this pertinent information sorted as the author intends.
  - As such, the Symbol field in MapUnitPolys, MapUnitLines, and MapUnitPoints is not calculated off of the DMU Symbol field as described in the GeMS documentation. It is instead a human-readable version of the Label field where we record the capital geologic time letters as plain text instead of FGDCGeoAge font symbols in addition to any ?, /, or + used in the “label” field. The map unit symbology based on the MapUnit field can be found in an accompanying style file.
  - ObservedMapUnit field added to the following point feature classes: GenericPoints, GenericSamples, OrientationPoints, and GeochronPoints. This is only required for the Stations feature class in GeMS.
  - Label field has been added to DataSourcePolys.

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