Late holocene behavior of Chaco and McElmo Canyon drainages (Southwest U.S.): A comparison based on archaeologic age controls

Abstract

Two outwardly similar shallow‐canyon drainages of the Four Corners region of the Colorado Plateau (southwestern U.S.), McElmo Creek (SW Colorado) and Chaco Wash (NW New Mexico), expose late Holocene units which have been dated by numerous remains of the puebloan Anasazi culture (A.D. 500–1300). The stratigraphic sequences, though composed of similar sediment facies, show markedly different evolutions. The McElmo Canyon sequence consists of two units separated by an unconformity that apparently represents an arroyo that migrated 5 km upstream in 200 years, suggesting a slow “complex response” model. The dated Chaco Canyon sequence includes an arroyo channel fill seemingly cut simultaneously through a 9–14 km reach, which began filling simultaneously throughout about 100 years later. Base level control seems to have been temporarily controlled by a large eolian sand dune damming Chaco Wash, probably during a dry period. The two entrenchment chronologies do overlap, but the resemblance of either record to published regional chronostratigraphies is minimal. The differences among these regional chronologies suggest that great variety existed among fluvial sequences in prehistory, perhaps more than is seen in present‐day drainages of the region. The contrasting fluvial histories correspond to an equally marked difference in cultural responses, especially in water‐control technology. The strongest obvious similarity between the sequences is probable anthropogenic influence, which is a consequence of using cultural remains for establishing chronological control. A strong influence of climate change is less obvious but still probable if lags in the system and possible intraregional paleoclimatic differences are included in the analysis. © 2004 Wiley Periodicals, Inc.

Millennial-scale dynamics of valley fills over the past 12,000 14C yr in northeastern New Mexico, USA

“…It is unknown whether these age reversals are caused by old wood or by the reworking of previously deposited charcoal. A fi nal complication in interpreting alluvial history comes from the complex geomorphic responses of different streams and different reaches of the same stream to the same environmental drivers Schumm, 1975, 1981;Force, 2004). We dealt with these actual and potential problems as follows.…”

Erosion, storage, and transport of sediment in two subbasins of the Rio Puerco, New Mexico

“…Similar timing of incision over a broad geographic area supports an allogenic (climatic) control for arroyo cutting (Karlstrom and Karlstrom, 1987;Karlstrom, 2005;Daniels, 2008). However, nonsynchroneity of cutting episodes for some basins in the Holocene indicates that factors other than climatic change may contribute to the timing of arroyo incision (Patton and Schumm, 1981;Patton and Boison, 1986;Karlstrom and Karlstrom, 1987;Elliott et al, 1999;Force, 2004). The recent arroyo cutting episode in the late nineteenth and early twentieth centuries has generally been attributed to three causes: (1) climate change (Leopold and Snyder, 1951;Balling and Wells, 1990;Hereford, 2002), (2) human factors such as overgrazing (Thornthwaite et al, 1942;Cooke and Reeves, 1976) and dam failures (Love, 1997), and (3) intrinsic geomorphic processes and thresholds (Schumm and Hadley, 1957;Pederson 2000).…”

“…Late Quaternary studies in the Southwest that support this model include work by Force (2004). By contrast, several studies do not fi nd support for time-transgressive alluvial stratigraphy in paleoarroyos (Karlstrom and Karlstrom, 1987;Hereford, 2002).…”

Chronostratigraphic and Paleoenvironmental Evidence for Marsh Habitats during the Early Pueblo I (A.D. 700–900) Occupation of Ridges Basin, Southwest Colorado, USA

“…For example, Force et al. () and Force (), working near Chaco Canyon National Monument in northern New Mexico, suggested that Chaco Wash was intermittently dammed by eolian processes to form the so‐called “Chaco Lake” during the Pueblo II occupation there. Researchers then related cultural development at Chaco Canyon, measured by building construction, to the influence of lacustrine conditions on alluvial aggradation, channel cutting, and irrigation.…”