ALMANDINE GARNET SAND GRAINS ORIGIN AND DISTRIBUTION ALONG THE MAINE AND MASSACHUSETTS COASTLINE

Almandine garnet rich sands can be found on some of the natural beaches of the New England coastline. The garnet rich sand presents itself visually as thin layers on the surface and subsurface as pink and purple sand. At Crescent Beach, a survey of the beach shows that the almandine rich sand can only be visually distinguishable in the subsurface on and behind the berm of the beach in the backshore region leading into the attached marsh. In some areas, a thin layer is visible on the surface in the foreshore region, but is visually indistinguishable in the sub-surface. Visually distinguishable layers can be examined that lead further under the attached marshland.

The almandine garnet sand is being exposed by the erosion of the marshland behind the beach due to the current trend in sea level rise and storm surges. Once revealed, the almandine sand is redistributed in the backshore region of the beach.

The almandine garnets were originally transported from outcrops of mica schist in the Green Mountains and White Mountains of Vermont, Maine and Canada by the advancing Laurentide ice sheet. Once the Laurentide ice sheet began to retreat, large amounts of sediment, which included the almandine garnet grains, were deposited as glaciomarine deltas. A combination of glacial melt and declining sea level contributed subsequent sediment transportation of portions of the deltas, depositing the sediment into their current position along the coastline.