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

Cyprian Seul,Tomasz Kozłowski,Roman Bednarek,Łukasz Maciąg

doi:10.3390/geosciences10090367

Cyprian Seul, Tomasz Kozłowski + Show 2 more

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https://doi.org/10.3390/geosciences10090367

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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.

Highlights

Lithodynamic processes at the land–sea interface result in different morphologies of the coastal zone, dominated by elevated cliff sections or coastal dunes
These forms may reflect the history of development of the coastal zone, where swash hydrodynamics steer the intensity of erosion and accumulation processes [1,2]
The major aims of the study are to determine the petrographic composition of beach gravels, compare these with similar initial data for gravels collected from cliff sections, map coast sections compare these with similar initial data for gravels collected from cliff sections, map coast sections affected and accumulation processes, and thelink results morphodynamics estimated affectedby byerosion erosion and accumulation processes, andlink thetoresults to morphodynamics by applying nongeological methods, accounting for the presence of coastal protection structures

Summary

Introduction

Lithodynamic processes at the land–sea interface result in different morphologies of the coastal zone, dominated by elevated cliff sections or coastal dunes. These forms may reflect the history of development of the coastal zone, where swash hydrodynamics steer the intensity of erosion and accumulation processes [1,2]. The spatial and temporal changes with the coastal sediment budget are usually related to increased cliff and beach erosion and redeposition of sedimentary material [3]. One or more gravel ridges may exist in the subaerial profile

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