Geologic Formations

The Salinas Pueblo Missions National Monument in central New Mexico is a testament to the geology that underlies the region. The Early Permian was a time when the continents were not separate, but a single supercontinent called Pangea. New Mexico was equatorial with the Hueco seaway to the south and floodplains covering the areas surrounding Mountainair. As the environment changed, so did the rocks.

The geology in central New Mexico is marked by a distinct carbonate bed, which is the result of rising sea levels. As the Hueco Seaway to the south encroaches on central New Mexico, the area becomes a semi-arid coastline. changing sea levels create carbonate layers and near-shore sands, while expansive tidal flats result in large deposits of gypsum, a mineral that precipitates from evaporating water bodies (also known as an evaporite).

Between 20 and 15 million years ago, the Rio Grande rift began to form to the west, allowing molten rock to make its way towards the surface in the form of dikes. These dikes can be found in abundance beneath Gran Quivira. After these molten intrusions, the geology in the area is at a standstill until nearly 45 thousand years ago when lakes covered the Estancia basin, forming Lake Estancia. Each of the three park units were close to its shores until it finally dried up.

The most recent geology of this area is what most would look at and call dirt, much of it deposited from erosion of the Manzano Mountains and the underlying Permian bedrock. The park units of Abó and Quarai looked very different 280 million years ago, with seasonal monsoons bringing iron-rich sediment from higher elevations to the rivers that meandered through the plains. The Abo Formation gradually became the Arroyo de Alamillo Formation, recording a much drier environment with wind-swept sand dunes and the occasional riverbed.

Paleontology of the Abo Formation in New Mexico has been studied for several decades, with footprints and trackways being the most common animal fossils found within park boundaries. The Yeso Group, previously thought to be not fossiliferous, has seen trackways, plants, marine, and even skeletal fossils in these formations.