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An Equable Glaciopluvial in the West: Pleniglacial Evidence of Increased Precipitation on a Gradient from the Great Basin to the Sonoran and Chihuahuan Deserts

Published online by Cambridge University Press:  20 January 2017

Philip V. Wells
Philip V. Wells*
Affiliation:
Division of Biological Sciences, University of Kansas, Lawrence, Kansas 66045
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Abstract

Dated macrofossil evidence documents the widespread occurrence of woodland in what are now desert lowlands of southwestern North America from the last pleniglacial (ca. 20,000 yr B.P.) to late glacial/Holocene transition (12,000–8000 yr B.P.). The composition of the Pleistocene woodlands indicates that they had already differentiated geographically in modern form, though immensely more extensive than today. The pinyon-juniper woodland (Pinus monophylla, Juniperus osteosperma) of the Mohave Desert province had not yet penetrated the central Great Basin, but extended from southern Nevada south through the vast lowlands of the Mohave and westernmost Sonoran Deserts to southeastern California and Baja California. The strongly xerophytic Mohavean woodland was characterized by a very well-marked altitudinal and latitudinal zonation with juniper-Joshua tree (Yucca brevifolia) sorting out below pinyon-juniper woodland, and with live oaks restricted to the upper level along the lower Colorado River drainage. Southeastward, the Sonoran Desert province was similarly zoned, but with the more slender-leaved Pinus edulis var. fallax as pinyon and with more live oaks in the upper zone. However, the pleniglacial woodland of the Chihuahuan Desert province was almost unzoned, inasmuch as the less xerophytic species of pinyon and live oaks prevailed over the entire span of available elevation; the pinyon was the very slender-leaved P. cembroides var. remota.

The overall paleozonation indicates a strong northwest-to-southeast gradient of increasing summer rain with decreasing distance from the monsoonal source area over the Gulf of Mexico, as at present, but augmented pluvially along the same gradient. A key piece of evidence is the counterintuitive latitudinal-zonational anomaly between about 30 and 40° N in southwestern North America; the lower limits of modern vegetational zones are depressed with decreasing latitude (e.g., ca. 500 m lower at 34° than at 36° N). The axis of the gradient actually extends from northwest to southeast, paralleling the monsoonal gradient of increasing summer rain, which no doubt causes the apparent anomaly. During the Wisconsinan glacial, the latitudinal anomaly was greatly steepened, a fact requiring a pluvial increase in precipitation over the Southwest. The monsoonalpluvial pattern is supported by the Neotoma record of a northwest-to-southeast gradient of increasing diversity of evergreen oaks requiring summer rain, and by a parallel segregation of pinyon species. Equability of seasons during the last glacial is also suggested by the Neotoma macrofossil data.

Type
Research Article
Information
Quaternary Research , Volume 12 , Issue 3 , November 1979 , pp. 311 - 325
Copyright
University of Washington

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References

Antevs, E., (1954). Climate of New Mexico during the last glacial-pluvial. Journal of Geology. 62, 182-191.Google Scholar
Axelrod, D.I., (1950). Evolution of desert vegetation in western North America. Carnegie Institution of Washington Publication. 590, 215-306.Google Scholar
Axelrod, D.I., (1958). Evolution of the Madro-Tertiary geoflora. Botanical Review. 24, 433-509.Google Scholar
Brakenridge, G.R., (1978). Evidence for a cold, dry full-glacial climate in the American Southwest. Quaternary Research. 9, 22-40.CrossRefGoogle Scholar
Daubenmire, R.F., (1943). Vegetational zonation in the Rocky Mountains. Botanical Review. 9, 325-393.CrossRefGoogle Scholar
Flint, R.F., (1971). Glacial and Quaternary Geology. Wiley, New York. Google Scholar
Galloway, R.W., (1970). The full-glacial climate in the southwestern United States. Annals of the Association of American Geographers. 60, 245-256.Google Scholar
Haller, J.R., (1965). The role of 2-needle fascicles in the adaptation and evolution of ponderosa pine. Brittonia. 17, 354-382.CrossRefGoogle Scholar
Lanner, R.M., (1974). Morphology of pinyon pine needles from fossil packrat middens in Arizona. Forest Science. 20, 207-211.Google Scholar
Leighly, J., (1956). Weather and climate. Zierer, C.M., California and the Southwest. Wiley, New York. Google Scholar
Leskinen, P.H., (1970). Late Pleistocene Vegetation Change in the Christmas Tree Pass Area, Newberry Mountains, Nevada. M.S. thesis. University of Arizona, Tucson. Google Scholar
Leskinen, P.H., (1975). Occurrence of oaks in late Pleistocene vegetation in the Mojave Desert of Nevada. Madrono. 23, 234-235.Google Scholar
Little, E.L., (1966). A new pinyon variety from Texas. Wrightia. 3, 181-187.Google Scholar
Little, E.L., (1968). Two new pinyon varieties from Arizona. Phytologia. 17, 329-342.Google Scholar
Loew, O., (1876). Report on the geographical distribution of vegetation in the Mohave Desert. Wheeler, G.M., U.S. Geographic and Geological Surveys West of the 100th Meridian. Annual Report Chief of Engineers. 442-444 Washington, D.C..Google Scholar
Malde, H.E., (1964). Patterned ground in the western Snake River Plain, Idaho, and its possible cold-climate origin. Geological Society of America Bulletin. 75, 191-208.Google Scholar
Martin, P.S., (1963) The Last 10,000 Years. Univ. of Arizona Press, Tucson. Google Scholar
Meinzer, O.E., (1922). Map of Pleistocene lakes of the Basin and Range Province and its significance. Geological Society of America Bullectin. 33, 541-552.Google Scholar
Nichol, A.A., (1952). The natural vegetation of Arizona. University of Arizona, College of Agriculture, Technical Bulletin. 127, 189-230.Google Scholar
Rothrock, J.T., (1878). Reports upon the botanical collections. Report upon United States Geographical Surveys West of the One Hundredth Meridian. Vol. 6, Government Printing Office, Washington, D.C. Google Scholar
Shreve, F., (1951) Vegetation of the Sonoran Desert. 1-192 Carnegie Institute of Washington Publication 591.Google Scholar
Spaulding, W.G., (1977). Late Quaternary vegetational change in the Sheep Range, southern Nevada. Journal of the Arizona Academy of Science. 22, 3-8.Google Scholar
Trelease, W., (1924). The American oaks. National Academy of Sciences Memoirs. 20, 1-255.Google Scholar
Troughton, J.H., Wells, P.271., Mooney, H.A., (1974). Photosynthetic mechanisms and paleoecology from carbon isotope ratios in ancient specimens of C4 and CAM plants. Science. 185, 610-612.CrossRefGoogle ScholarPubMed
Van Devender, T.R., (1973). Late Pleistocene Plants and Animals of the Sonoran Desert: A Survey of Ancient Packrat Middens in Southwestern Arizona. Ph.D. dissertation. University of Arizona, Tucson. Google Scholar
Van Devender, T.R., (1977). Holocene woodlands in the southwestern deserts. Science. 198, 189-192.Google Scholar
Van Devender, T.R., Wiseman, F.M., (1977). A preliminary chronology of bioenvironmental changes during the paleoindian period in the monsoonal Southwest. Paleoindian Lifeways. Johnson, E., The Museum Journal. Vol. 17, West Texas Museum Association, Texas Tech University, Lubbock, 13-27.Google Scholar
Wells, P.272., (1965). Vegetation of the Dead Horse Mountains, Brewster County, Texas. Southwestern Naturalist. 10, 256-260.Google Scholar
Wells, P.273., (1966). Late Pleistocene vegetation and degree of pluvial climatic change in the Chihuahuan Desert. Science. 153, 970-975.CrossRefGoogle ScholarPubMed
Wells, P.274., (1969). Preuves paléontologiques d'une 275égétation tardi-Pleistocène (datée par le 14C) dans les régions aujourd'hui désertiques d'Amérique du Nord. Revue de Géographie Physique et de Géologie Dynamique. 11, 335-340.Google Scholar
Wells, P.276., (1970). Vegetation of the Southwest between 14,000 and 9,000 years ago: The macrofossil record. American Quaternary Association Abstracts of the First Meeting. 1, 147-148.Google Scholar
Wells, P.277., (1976). Macrofossil analysis of wood rat (Neotoma) middens as a key to the Quaternary vegetational history of arid America. Quaternary Research. 6, 223-248.Google Scholar
Wells, P.278., (1977). Quaternary vegetational history of arid America. Xth INQUA Congress Abstracts. Birmingham, England (August, 1977) 499.Google Scholar
Wells, P.279., (1978). Postglacial origin of the present Chihuahuan Desert less than 11,500 years ago. Wauer, R.H., Riskind, D.H., Transactions of Symposium on the Biological Resources of the Chihuahuan Desert Region. paper read at Alpine, Texas, October 16, 1974. 67-83 Washington, D.C..Google Scholar
Wells, P.280., Berger, R., (1967). Late Pleistocene history of coniferous woodland in the Mohave Desert. Science. 155, 1640-1647.CrossRefGoogle ScholarPubMed
Wells, P.281., Hunziker, J.H., (1976). Origin of the creosote bush (Larrea) deserts of southwestern North America. Annals of the Missouri Botanical Garden. 63, 843-861.CrossRefGoogle Scholar
Wells, P.V., Jorgensen, C.D., (1964). Pleistocene wood rat middens and climatic change in Mohave Desert: A record of juniper woodlands. Science. 143, 1171-1174.Google Scholar
West, R.C., (1964). Natural Environment and Early Cultures. Wauchope, R., Handbook of Middle American Indians. Vol. 1, University of Texas Press, Austin. Google Scholar
Woodbury, A.M., (1947). Distribution of pigmy conifers in Utah and northeastern Arizona. Ecology. 28, 113-126.Google Scholar