Quaternary history of the Estancia Valley, central New Mexico
— Frederick W. Bachhuber

The Estancia valley lies within a closed physiographic and structural basin near the geographic center of the state of New Mexico (fig. 1). This arid valley presently has a deficit water budget of 122 cm annually which precludes the existence of natural perennial-water bodies. Geomorphic, sedimentologic, and paleontologic evidence, however, indicates that major climatic oscillations occurred during the Quaternary.

 

The geologic history of the Estancia valley has been synthesized over a period of almost 80 years following Keyes' (1903) observation that the valley contained ". . . evidences of the existence of old lakes." Keyes and other researchers in the valley believed that the pluvial system, while of considerable areal extent and water depth, did not overflow into adjacent basins. Consequently, it was assumed that the lake system never evolved into a fresh-water body.

 

The highest elevations (over 3,050 m; 10,000 ft) within the Estancia valley occur along the western rim of the watershed; whereas, the lowest elevations (1,842 m; 6,045 ft) are found along the central topographic axis. Along the valley axis series of wind-excavated playas, arranged in an elliptical pattern, are incised into the valley floor (fig. 1). The deflation basins are cut into lacustrine sediment exposing a complex stratigraphic sequence of up to 10.5 m in thickness. In the southeastern corner of the basin a broad, gently-sloping saddle, termed the topographic sill, separates the Estancia valley from the Pinos Wells basin. Presently, the topographic sill has a minimum elevation of 1,929 m (6,330 ft), rendering a total topographic closure of 87 m.