Abstract

Unequal spacing of nearly vertical joints and sheeting in hornblende granite at Monument Cove, Maine, forms large tabular blocks which accumulate as talus on the backbeach. The blocks are subsequently rounded by wave action to form a pocket boulder and cobble beach. Measurements of the talus blocks and boulders indicate that the initial structurally controlled, bladed and elongate habits are manifested in the boulders; however, as abrasion progresses, more compact (spherical) and more platy (discoidal) boulders evolve. The data suggest that the greatest change is toward compactness and that the ultimate clast shape at Monument Cove would be spherical. The orientations of the L-I planes and the L-axes of the rounded clases were also measured. The L-I planes are well oriented, dipping mainly offshore. The L-axes orientations form three main clusters, one subparallel to the shoreline, one down the dip of the beach, and one oblique to the shoreline. The latter two clusters lie within the modal dip of the L-I planes.

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