Climatic influences on Quaternary alluvial stratigraphy and terrace formation in the Jemez River valley, New Mexico
John B. Rogers and Richard A. Smartt
Quaternary alluvium preserved within the Jemez River valley of the southwestern Jemez Mountains records net incision punctuated by periods of fluvial aggradation and equilibrium (relative stability). Quaternary incision of at least 192 m yields an average incision rate of at least 12 cm/ka within San Diego Canyon. Incision has been interrupted by 5 major valley-filling events that preceded Qt1-Qt4 terrace formation and includes the alluvium beneath the present valley floor, and by 4 minor aggradation and equilibrium periods preceding Qt5-Qt9 terrace formation. The alluvium beneath Qtl-Qt4 may record similar cycles of climate-driven incision, equilibrium, aggradation, equilibrium and incision. We hypothesize that incision is initiated during interglacial-glacial transitions and continues into glacial times; equilibrium facies (boulder lags) coincide with interglacial and (late) glacial conditions; and aggradation begins during glacial-interglacial transitions. Evidence for this hypothesis is derived from fill stratigraphy, chronology provided by the presence of Lava Creek B ash, paleoecological inferences, and analogy with the modern floodplain of the Jemez River. The hypothesis successfully predicts the stratigraphy beneath the modern floodplain and suggests a more precise way of estimating the age of terraces and terrace deposits based upon correlation with established climate records.
- Rogers, John B.; Smartt, Richard A., 1996, Climatic influences on Quaternary alluvial stratigraphy and terrace formation in the Jemez River valley, New Mexico, in: The Jemez Mountains Region, Goff, Fraser; Kues, Barry S.; Rogers, Margaret Ann; McFadden, Les D.; Gardner, Jamie N., New Mexico Geological Society, Guidebook, 47th Field Conference, pp. 347-356.