Soil-geomorphic relations of lamellae in eolian sand on the High Plains of Texas and New Mexico.

摘要

Clay lamellae are ubiquitous features in sands in a wide variety of settings around the world. Most studies of lamellae focus on: (1) a few or individual locales or on (2) formation by experimental methods in the laboratory. This study reports on lamellae from eight localities in three late-Quaternary dune fields on the Southern High Plains of northwest Texas and eastern New Mexico. Most lamellae observed are alluvial and they increase in number and thickness through time. A few (1-3) thin (1-2 mm) lamellae formed in Historic sediments. Lamellae are more numerous (3-12) and thicker (3-5 mm) in older late Holocene (<1000 14C years BP) and middle Holocene (<7600 14C years BP) sands. Soils that formed through the late Pleistocene and into the early Holocene (14 300-7600 14C years BP) or soils that formed throughout the Holocene can exhibit as many as 30 lamellae or lamellae of 10-12 mm thickness. The micromorphology of the lamellae shows that argillans on sand grains are thicker, more laminated, more continuous, and cap and link more grains through time. Other variables affect lamella morphology. Within individual dunes, the lamellae are best expressed where the sand is thickest; they decrease in number and thickness as sand thins. The lamellae also form only in clean, well-drained sand. Poor drainage and/or bioturbation result in formation of a continuous argillic horizon encasing lamellae..