Beach Gravels as a Potential Lithostatistical Indicator of Marine Coastal Dynamics: The Pogorzelica–Dziwnów (Western Pomerania, Baltic Sea, Poland) Case Study

Abstract

The petrographic composition and grain shape variability of beach gravels in the Pogorzelica–Dziwnów coast section (363.0 to 391.4 km of coastline), southern Baltic Sea, Poland were analyzed herein to characterize the lithodynamics and trends of seashore development. Gravels were sampled at 0.25 km intervals, in the midpart of the berm, following an early-autumn wave storm and before beach nourishment. Individual variations in petrographic groups along the shore were investigated. Gravel data were compared and related to coastal morpholithodynamics, seashore infrastructure, and geology of the study area. The contribution of crystalline rock gravels (igneous and metamorphic) was observed to increase along all coast sections, whereas the amount of less resistant components (limestones, sandstones, and shales) usually declined. This effect is explained by the greater wave crushing resistance of igneous and metamorphic components, compared with sedimentary components. Similarly, the gravel grain shape (mainly elongation or flattening) was observed to change, depending on resistance to mechanical destruction, or due to the increased chemical weathering in mainly the limestones, marbles, and sandstones. Observed increase in contribution of discoid and ellipsoid grains is a potential indicator of depositional trends along the coast sections investigated. On the other hand, increased contents of spheroidal and spindle-shaped grains may be related to erosional trends, where intensive redeposition and mechanical reworking of gravels occurs. However, due to the great number of coastal embankments, the petrographic composition and shape parameters of beach gravels do not always clearly indicate the dominant direction of longshore bedload transport. Increased amount of eroded limestone located east of Pogorzelica indicate increased erosion of glacial tills. These sediments are deposited, building the shallow foreshore, with additional redeposition of morainic material towards the shore.

Lithostatistical variability of beach gravels along the Polish coast of Baltic Sea: The Pogorzelica–Dziwnów dataset (363.0–391.4 km)

“…Among several lithostatistical parameters, the ‘gravel shape’ indices are useful for interpreting coastal dynamics, as well as the potential processes of material deposition-redeposition [6] . When assessing the intensity of shore erosion, lithodynamics of the coastal zone may be subject to rank-based evaluation based on several parameters, including ‘flatness index’, ‘roundness index’, or ‘weight index’ [ 7 , 8 ].…”

GIS-based methodology for mapping and modeling microbialite deposits in high mountain lakes and wetlands of Central Andes (Catamarca, Northwestern Argentina)

“…2). These morphologies were determined through visual evaluations, supported by the concepts proposed by Seul et al (2020). Based on their textural and lithological characteristics, Villafañe et al (2021a) indicates the presence of three types of internal structures (zones) in Las Quinoas oncoids: A nucleus zone made up of various lithologies in the central part of the samples, a well-laminated zone where the lamination is continuous around the nucleus, and a poorlylaminated zone in the external part of the sample where the lamination is interrupted by the presence of clastic material.…”