Abstract
Detailed multi-beam bathymetry, sub-bottom acoustic, and side-scan sonar observations of submerged canyons with tufa barriers were used to characterize the Zrmanja River karst estuary on the eastern Adriatic coast, Croatia. This unique karst environment consists of two submerged karst basins (Novigrad Sea and Karin Sea) that are connected with river canyons named Novsko Ždrilo and Karinsko Ždrilo. The combined use of high-resolution geophysical data with legacy topography and bathymetry data in a GIS environment allowed for the description and interpretation of this geomorphological setting in relation to the Holocene sea-level rise. The tufa barriers had a predominant influence on the Holocene flooding dynamics of the canyons and karst basins. Here, we describe the possible river pathways from the basins during the lowstand and the formation of a lengthening estuary during the Holocene sea-level rise. Based on the analyzed morphologies and the relative sea-level curve for the Adriatic Sea, the flooding of the Novsko Ždrilo occurred 9200 years before present (BP) and Karinsko Ždrilo was flooded after 8400 years BP. The combination of high-resolution geophysical methods gave an accurate representation of the karst estuarine seafloor and the flooding of semi-isolated basins due to sea-level rise.
Highlights
The rapid development of swath acoustic techniques has enabled seabed mapping at high spatial resolutions and accuracies
This study investigated a unique karst geomorphological setting that was recognized along the Croatian karst on the eastern Adriatic coast; it consists of two canyon-type outlets (Novsko Ždrilo and Karinsko Ždrilo) connecting two semi-isolated basins (Novigrad and Karin Seas) to each other and the open sea
During the last glacial maximum (LGM) lowstand, the Novigrad and Karin Seas acted as karst poljes, i.e., interior valleys [14]
Summary
The rapid development of swath acoustic techniques has enabled seabed mapping at high spatial resolutions and accuracies. The results of the high-resolution acoustic technologies, such as multibeam echosounder (MBES) bathymetry, MBES backscattering, sub-bottom profiling (SBP), side-scan sonar (SSS), and their derivatives, represent an excellent platform for geomorphological and geological classifications of the seabed [1,2,3]. Backscatter data of the acoustic intensity scattered by the seabed collected during MBES surveys [7] gives us valuable information about bottom-type sediment characteristics [1,8]. GIS-based classification techniques and packages for MBES bathymetry and MBES backscattering data have become numerous and available, and have undergone significant development and improvements in the past decade [7,9,10,11,12]. Sub-bottom profiles, Water 2020, 12, 2807; doi:10.3390/w12102807 www.mdpi.com/journal/water
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