Actual development of the chenier coast of suriname (South America)

Abstract

The Holocene coastal plain of Suriname is a chenier plain. Its actual sedimentological development has been studied during three field-work periods (1966, 1967/1968, 1972). Clay is the predominant sediment in this low- to medium-energy environment. It accumulates in extensive shoreface-attached mudflats (sometimes considered as giant mudwaves), which migrate continuously to the west due to deposition of slingmud at their west side and simultaneous erosion of the east side. In between the mudflats cheniers may develop. Thin-section analysis of the clay deposits revealed that they are built up of an alternation of thick clayey laminae and thin laminae of silt and fine sand. The clayey laminae chiefly show a unistrial plasmic fabric. Disturbaces in the upper zone are caused by bioturbation. Two types of cheniers can be distinguished. One type contains fine sand which has been winnowed out of the pelite deposits. Since this sand is brought from the shelf the chenier formation begins at approximately mean low-water level. Longshore bars are formed and these are driven shoreward by wave action. The other type is built up of medium to coarse sand supplied by a local river. It is transported westward by beachdrift in a narrow zone around the mean high-water line. These cheniers develop therefore at or just above the mean high-tide level. The sedimentary structures of both types of cheniers have many characteristics in common. However, each type also has its own distinct features.