SURFICIAL DEPOSITS IN CENTRAL PRINCE EDWARD ISLAND: THEIR ORIGIN AND SOIL GENESIS

MacLean, B.

The retreat of the continental glaciers from Central Prince Edward Island left a landscape characterized by highly variable  deposits. These deposits have previously been mapped as weathered bedrock and glacial till. This thesis examined these deposits and attempted to determine their origins more precisely.  Eight sites were selected and each deposit was fully described in the field, and when necessary, studies on particle size distribution, stone shape and roundness, stone orientation and imbrication and micromorphology were conducted. Initial field investigations revealed the complex nature of the surficial deposits. Most of the deposits located on the higher e1evations were either sandy and loose,  or formed on dense clay rich material. Stone orientation and imbrication analysis revealed that many of the deposits had been moved down- slope, indicating either solifluction or soil creep. The analysis of the particle size distributions of the surficial material and the unconsolidated bedrock samples differentiated between deposits that  had weathered in situ and deposits that had been transported. However, it could not differentiate between basal till, ablation till or material that had moved either by solifluction or soil creep. Stone shape and roundness analysis proved to be more effective in separating these deposits. Deposits formed as basal till contained more spherical shaped stones with low roundness, while the stones in ablation till were also spherical but had higher roundness values. From stone shape and roundness analysis it was not possible to deter- mine those deposits that had undergone solifluction or soil creep, since the effect of these processes on pebble geometry is not known.  Soil micromorphology analysis was conducted on only two profiles. The process of in situ weathering was evident in one of the profiles, confirming the findings of the other analysis.  Soil texture was found to be a dominant factor affecting the genesis of the soil. In loose, coarse textured soils, translocation of Fe and AI was the dominant process, while in the compact fine textured soils, clay translocation was also important. The coarse , textured soils were classified as Orthic Rumo-Ferric Podzols, while the fine textured soils were classified as Brunisolic Gray Brown Luvisols or Podzolic Gray Brown Luvisols.