In Search of "Organ III" Strata-a Sedimentary Record of the Medieval Warm Period (ca. AD 900 to 1300)
The period AD 900 to 1300, internationally referred to as the Medieval Warm Period, is a critical time for the archaeological record of the Southwestern USA. During the Medieval Warm Period both alluvial and eolian sedimentation increased, but not to the magnitude of the middle Holocene (the Altithermal) or since Historical erosion began in the middle 1850s (the end of the Little Ice Age). Locally, the term "Organ III" has been given to the Medieval Warm Period allostratigraphic unit. It is a subtle unit stratigraphically between Altithermal sediments (Organ I) and Historical sediments. Diagnostic features for identifying these three units include the following: Organ I has distinct carbonate filaments and strong pedogenic structure; Organ III has very faint carbonate filaments and weak pedogenic structure; Historical deposits have no carbonate and sedimentary layers. The Organ III stratum is most obvious in geomorphic settings with contrasting parent materials or where an occupational surface underlies the Organ III unit. In addition to its archaeological significance, the Organ III unit provides information about the relative magnitude of current climate change as compared to prehistoric climate change.
Ed L. Frederickson, Curtis H. Monger, and Katie Laney. "In Search of "Organ III" Strata-a Sedimentary Record of the Medieval Warm Period (ca. AD 900 to 1300)" 16th Biennial Mogollon Archaeology Conference. Las Cruces, New Mexico. Oct. 2010.
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