Changes in quantity and compositon of crystalline clay across E-BH boundaries of Alaquods

Theories of Spodosol formation emphasize chemical rather than particle tran slocation. However, some studies have presented evidence for particle as we ll as chemical migration in the formation of Bh horizons. In addition, abun dant data for Florida Alaquods show that Bh horizons have significantly hig her clay content than do eluvial and common subjacent horizons. This bulge in clay content has genetic implications if it is: partially attributable t o crystalline clay because it would be evidence suggesting that colloidal m igration (lessivage) has occurred. This study was conducted to compare the amount and composition of crystalline clay contained in Bh and adjoining ho rizons of Alaquods. Data for more than 200 Alaquod profiles available from the Florida Cooperative Soil Survey database and complementary data generat ed for six of these profiles selected randomly from the pool were statistic ally analyzed. Pre-existing data included organic C; pyrophosphate-extracta ble C, Fe, and Al; citrate-dithionite extractable Fe and Al; and particle s ize distribution (pipette). Complementary data included particle size (cent rifugal separation) and clay mineralogy (by X-ray diffraction and different ial scanning colorimetry), each following: H2O2, and ammonium oxalate pretr eatment. Particle size data in conjunction with mineralogy confirmed a sign ificant increase in resistant secondary phyllosilicates from the E to the B h horizon, consistent with a physical redistribution of clay particles from the E to the Bh horizon. A possible source of these particles is sand grai n coatings, which are absent from Alaquod E horizons but present in E horiz ons of most other sandy soils on better drained adjacent landforms. Noncrys talline Al in grain coatings may be the source of Al accumulated in the Bh horizons of these soils, rather than weatherable minerals, which are nearly absent in the upper 2 m.