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General Description. Fossils collected in pit about 30 km west of Magdalena and 1 km north of US Route 60 (Morgan and Lucas 2005). Probable late Wisconsin beach deposits of the intermediate lake level at 6975'.
Discussion. Fauna associated with fish vertebrae; abundant small, low-spired gastropods; very small pelecypods; sparse high-spired gastropods; and charophyte oogonia. Data from Robert Weber, New Mexico Bureau of Mines.
White Lake is part of a larger feature, Pleistocene Lake San Agustín. The San Agustín Plains consist of three sub-basins that held lakes during the Pleistocene (C-N Lake, Lake San Agustín, and White Lake), and these apparently merged into a single large lake at times during the Pleistocene.
Satellite view of the San Agustín Plains and the surrounding region. 1, Magdalena Mountains; 2, San Mateo Mountains; 3, San Agustín Plains; 4, Pie Town; 5, Very Large Array; 6, Magdalena Ridge Observatory. The vertical line separates Catron Co. on the left from Socorro Co. on the right. The deepest part of the basin is the bluish area at the southwestern end (diagonally down and right from the word "Catron"). White Lake is in the vicinity of the Very Large Array.
Three cores from the deepest basin (southwestern part of the Plains) have given paleoecological data. The more recent (the so-called Auger Site) was reported by Magraf et al. (1983). The dates from the Markgraf site were 15,040 ± 200 at about 1.3 m and 18,300 ± 300 at about 2 m (depths are approximate). The results, compared to dates from the two earlier cores, suggest (not surprisingly) that deposition rates varied between sites and between depths, with the extremes being 0.12 mm/y and 0.43 mm/y.
Markgraf et al. (1983), based on pollen, algae, diatoms, and ostracods, distinguished four major paleoenvironmental phases in the approximately 18,000-year Auger Site:
18,000-15,000 BP. Open pine/spruce woodland with lesser amounts of juniper, much sagebrush and grass, composites, and some saltbush. Spruce and sagebrush indicate the interval was of a cool, continental climate with a predominance of winter precipitation.
15,000-10,000 BP. Pine/spruce/juniper woodland with similar herbaceous growth but less sagebrush.
10,000-5,000 BP. Pine and juniper woodland. Fir and spruce were at low concentrations. Herbaceous vegetation was largely of grasses.
5,000-present. Modern saltbush/greasewood playa vegetation with pine and juniper on the surrounding slopes.
The algal and ostracod data indicated that at 18,000 BP, there was a temperate freshwater lake with an extensive, open-water environment. The dominant ostracod now lives in the high-lands of central Mexico, while another ostracod is of semiarid areas of the northern U.S. and central Canada. Markgraf et al. suggest that occurrence of these together suggest that the Mexican species cannot take the low wintertime temperatures current.
At an estimated 17,000 BP, the lake became shallower, with species of benthic diatoms becoming dominant and the ostracods suggesting increased salinity. There are abundant macrofossil remains of Engelmann Spruce needles at the auger site (spruce now is beyond the drainage basin, but there is a large stand about 14 miles to the southwest). Continued presence of a lake in the basin is indicated throughout the 17,000 to 10,000-year period. From about 10,000 to about 8,000 BP, a freshening of water is suggested, followed by increasing salinity thereafter. After 5,000 years ago, conditions seem to have been similar to those of today, with only ephemeral, fluctuating, shallow lakes.
Presumably, the sequence was similar at the White Lake section.
Ambystoma mavortium—Barred Tiger Salamander (Harris 1993c)
Scaphiopus/Spea—Spadefoot (Harris 1993c) (cf.)
Anaxyrus/Ollotis—Common Toads (Harris 1993c) (cf.)
Lithobates sp.—Leopard Frogs (Harris 1993c)
Podiceps/Podilymbus—Grebe (Harris 1993c)
Anas (size A. acuta)—Dabbling Duck size of Northern Pintail (Harris 1993c) (cf.)
Branta—Canadian Goose (Harris 1993c) (?)
Mammuthus sp.—Mammoth (Morgan et al. 2009)
Microtus pennsylvanicus—Meadow Vole (Harris 1993c)
Ondatra zibethicus—Common Muskrat (Harris 1993c)
Peromyscus sp.—White-footed Mice (Harris 1993c)
Sylvilagus sp.—Cottontail Rabbit (Morgan et al. 2009)
Literature. Harris 1993c; Markgraf et al. 1983; Morgan and Lucas 2005; Morgan et al. 2009.
Last Update: 7 Jul 2010