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

摘要: We studied the alluvial histories of eight small ( 2 ) watersheds in uplands northeastern New Mexico. The data come from radiocarbon-dated sections exposed banks arroyos and permanent-channel streams. Results show that nine periods valley aggradation separated by incision episodes occurred over past 12,000 14 C yr. These millennial-scale cycles rough synchrony within different drainages. Parts some coincided with well-known climatic fluctuations. For example, during Younger Dryas chronozone, 11,000–10,000 yr B.P., fills persisted incised states early Holocene peak Milanko-vitch summer insolation. Incision Medieval Warm Period (ca. A. D. 1000–1300), Little Ice Age (A.D. 1300–1880), last century. Changes precipitation tied to strength North American Monsoon system probably drive these incision: when is strong, more frequent thunderstorms cause increased flooding watersheds. Wetter summers decades centuries allow forest vegetation spread, which reduces sediment input hillslopes at same time floods are eroding fills. Aggradation occurs less frequent, large correspondingly rare. Prolonged drought cover, increases erosion slopes causes accumulate valleys. In turn, controlled fluctuating sea-surface temperatures. geomorphic we describe may reflect a previously unrecognized, climate oscillation important shaping landscapes southern Great Plains.