Road Log Day 3 Mid-tertiary Alkalic Igneous Activity in Northeastern New Mexico — The Eagle Rock Dike: Third-day Road Log from Capulin, US–64/NM–325 Intersection, to the I–25 Intersection of the Eagle Rock Dike
— Frank C. Ramos, Matthew J. Zimmerer, and Kate E. Zeigler

On this last morning of the 2019 New Mexico Geological So-ciety Fall Field Conference, we will visit and explore the Eagle Rock (or Tinaja) dike, which is well exposed at a roadcut along I–25 south of Raton, NM. The caravan of personal vehicles will travel ~98 miles from Clayton through Des Moines and Capulin following the Day 1 Road Log. This road log (Fig. 3.1) starts when we leave Capulin and drive towards Raton (at the mile 54.5 point of the Day 1 Road Log). Prior to reaching Des Moines, we will stop at the US–64/87 rest stop to use the restrooms and stretch if needed before an additional ~1 hour drive to the Eagle Rock dike. The caravan will re-enter US–64 heading west from the rest stop towards Capulin and Raton. Along the way, we will drive through late Cenozoic rocks associated with the Raton-Clayton volcanic field and sedimentary rocks associated with the Raton basin. Before entering downtown Raton, the caravan will turn south onto I–25 towards Las Vegas, NM. We will stop ~16 miles south of Raton taking the Tinaja exit (#435), where we will park along the I–25 South entrance ramp, the ranch access road to the right of the stop sign, and the I–25 exit ramp if needed. Flaggers will direct participants where to park. From there, we will take a short hike north up a moderately steep slope to the top of Eagle Rock dike, a well-exposed basanitic dike (alkali-element rich, mafic igneous rock). The dike is ~24 Ma, grey in color, and variably metamorphosed country rocks composed of Pierre shale. The origins of the dike are unclear. It may be related to local alkalic, Chico Sill complex volcanic rocks present south and southeast of this location (Eagle Tail Mesa). Alternatively, the dike may be related to the Latir/Questa area located to the west in the southern Rocky Mountains.