Geologic framework as a factor controlling coastal morphometry and dynamics. Curonian Spit, Lithuania

The geologic framework is an important factor worth consideration when analyzing the development of seacoasts. The different coastal responses to hydrometeorological and anthropogenic factors depend on the composition and amount of original coast-forming sediments. The impact of sediment composition on morphometric parameters is best observed in areas where sand unrepresentative of the adjacent coastal sectors appears on beaches with a relatively uniform lithological composition. These areas are referred to as lithological anomalies. Large amounts of coarse-grained sand, uncharacteristic of the adjacent coastal sectors of the Curonian spit, accumulated in the area of the strait that existed in the Post-Littorina Late Subboreal (3.7-2.5 ka BP) time south of the Juodkrantė settlement. Due to accumulation of coarse sand, the beach in this sector is narrow and has a higher slope, and the ridge is lower and with a smaller volume of sand than in the adjacent coastal sectors. The specific sand composition and morphology of this coastal sector are responsible for different coastal dynamics during storms. During extreme storms, beach erosion in this coastal sector is minimal (sometimes even accretion takes place) compared with other sectors where beach erosion is rather substantial. Meanwhile, during periods of relatively calm weather, i.e. times of expected regeneration of the cross profile, this sector stands out for active erosion processes.