ABSTRACT

The barrier-beach shoreline near Michael River, Labrador, is ice-bound for more than 6 months each year. The contemporary beachface deposits record a complete yearly cycle as follows. The lowermost unit (d), a well-laminated fine- to medium-grained sand, and the overlying unit (a), a graded sequence of well-mixed sand and gravel near the bottom and medium-grained laminated sand at the top, represent foreshore accretion during summer and fall. Unit a is overlain by unit b, a laminated, fine- to medium-grained sand deposit, containing contorted and disrupted laminae and intrabedded "sand clasts," features which characterize middle to upper foreshore deposits that have accreted under freezing conditions. The cycle is completed by unit c, a mixed gravel and sand deposit that resembles ice rafted and ice-push deposits which form on cold-climate beaches during spring break-up of nearshore ice. Unit b is considered to be the "freeze-up deposit" formed during early winter, and unit c the subsequent "break-up deposit" which accumulated during spring. Unit c is overlain by unit d, a well-laminated foreshore sand which marks the beginning of the next cycle.

The fact that freeze-up and break-up events are recorded in a yearly cycle of beachface accretion indicates that such deposits could have been preserved in the rock record. If the cyclic sequence, recorded in the beachface near Michael River, were encountered in ancient rocks it could be a good indicator of paleo-climatic summer-winter seasonal conditions.