On the origin of both a recent and submerged tombolo on Prvić Island in the Kvarner area (Adriatic Sea, Croatia)

Čedomir Benac,Igor Ružić,Neven Bočić

doi:10.4154/gc.2019.14

Čedomir Benac, Igor Ružić + Show 1 more

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https://doi.org/10.4154/gc.2019.14

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Abstract

This paper analyzes the origins of two tombolos (one recent and another fossil/submerged) on the southwestern coast of Prvic Island, which is located in the Kvarner area in the northeastern part of the Adriatic Sea. A recent tombolo on Cape Pipa was formed by the erosion of Quaternary deposits and Palaeogene siliciclastic rocks. The submerged tombolo is much bigger, clearly visible on the sea bed toward the southwest. The conditions for forming a submerged and recent tombolo have occurred during a slow rise and then stagnation of sea level of the Adriatic Sea in the Holocene. The sea flooded the fossil tombolo probably in the final part of a period of rapid sea-level rise at the beginning of the Holocene when a large proportion of the Quaternary sediments were eroded. Waves from the northwest (tramuntana) and southeast (jugo) refract and diffract around the tombolo. The nourishment of the beach body happens permanently on both sides of the cape. Accumulated sediments are protected by resistant rocky blocks of breccia on the peak of Cape Pipa, acting as a natural tombolo. Due to the fact that wave directions are perpendicular to the beach coastline, they do not generate longshore currents that would erode sediment in beach bodies around Cape Pipa. Therefore, the recent tombolo is probably stable in the present climatic and oceanographic conditions in the Kvarner area.

Highlights

Sea level is a global boundary with weathering and erosional pro cesses prevailing above it, whereas the accumulation of sediments occurs below it
This paper analyzes the origins of two tombolos on the southwestern coast of Prvić Island, which is located in the Kvarner area in the northeastern part of the Adriatic Sea
Cape Pipa is formed by sea erosion of the Palaeogene siliciclastic rocks which are partially covered with younger cohesive sediments, probably of Quaternary age (Fig. 3)

Summary

Introduction

Sea level is a global boundary with weathering and erosional pro cesses prevailing above it, whereas the accumulation of sediments occurs below it. In accordance with sea level changes during geo logical history, the intensity and location of erosion and accumu lation of sediments changed (COWELL & THOM, 1997). Remnants of the effects of sea level changes have been found on the coastal and submarine relief in the Kvarner area in the north eastern part of the Adriatic Sea (BENAC & JURAČIĆ, 1998). This paper analyses the origins of two tombolos (one recent and one submerged) and their conditional dependence on the Ho locene sea level rise. Both tombolos are located on the southwest ern coast of Prvić Island in the Kvarner area, in the northeastern part of the Adriatic Sea (Fig. 1A). A tombolo is a depositional geomorphological landform (sandbar, barrier or spit) that joins an island or a barrier with ei ther the mainland or another island, resulting from longshore drift or the migration of an offshore bar toward the coast (WARD, 2004)

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