LITHOLOGY AND HYDRODYNAMICS OF THE BLACK SEA ODESSA COAST UNDERWATER PART

Abstract

Problem Statement and Purpose. The results of lithological studies, including granulometric analysis, are needed to identify the conditions of sedimentation and distribution of rock fragments by size. They are an indicator of the sedimentation processes dynamic structure peculiarities. The study of the sediment regime is important for the development of measures related to the protection of shores from erosion. The aim of the work is to identify the lithological features of the bottom sediment types distribution on the protected section of the Odessa coast near Cape Maly Fontan. Data & Methods. The materials for this work were obtained in the field research in the summer 2019 in the coastal zone between the hydrobiological station of Odessa I. I. Mechnikov National University, and Cape Malyj Fountain. Three measuring profiles were made perpendicular to the shoreline at 1200 m towards the sea to a depth of 18 m. 35 samples were taken from the upper layer of bottom sediments. Field samples processing was performed in the Problem Research Laboratory of Engineering Geology of the Sea Coast, Reservoirs and Mountain Slopes of Odessa I. I. Mechnikov National University. Granulometric classification was performed. Excel, Statistica, Golden Software Surfer programs were used to process the results. Results. Underwater relief analysis showed that the coastal part is an abrasive terrace, on which ancient landslides relics are widespread. There are 7 main lithological types of bottom sediments detected. The largest areas covered by fine-grained loamy sands and shell detritus with gravel, pebbles and sand. Analysis of distribution curves and cumulative curves of granulometric distribution showed that coarse sediments are characterized by multi-vertex distribution curves and stepwise stretched cumulative curves, which indicates the heterogeneity of sediments in granulometric distribution. For fine-grained material, which is well sorted, the distribution curves are almost single-vertex, and the cumulative curves have a large steepness and a simple, non-stepped shape. There are three hydrodynamic detected in bottom sediments lithology according on statistical parameters of grain size. Outer marine part with depth more than 15 meters characterized by low hydrodynamic processes and presented by good-sorted sands and silt. The central part of polygon in 4–15 meters depth covered by shell detritus with gravel and pebble of carbonate rocks and connected with rocky extrusions after coastal landslides. The feature of this part is active hydrodynamic processes. The rocky extrusions presented like natural breakwater and due to waves braking and collection of different types of sediments. The coastal part in 2–4 m depth in front of constructed breakwater leads to decreasing of wave energy and sedimentation of good-sorted sands.