Variation of sedimentation rate in the semi-enclosed bay determined by 137Cs distribution in sediment (Kaštela Bay, Croatia)

137Cs Sediment Profiles as a Tracer of Marine Sedimentation Processes in a Semi-Enclosed Bay Affected by Anthropogenic Releases—Example of Kaštela Bay (Adriatic Sea, Croatia)

“…In its west part, it is connected to Trogir Bay through the narrow Trogir Channel between the mainland and the Čiovo Island, while in the southeast, it is connected to the Split and Brač Channels through a wide passage between the Split peninsula and Čiovo Island. Despite their connection, Kaštela Bay, the Split, and Brač Channels are separate marine basins defined by different ecological characteristics and terrestrial influences [22]. The Bay is 14.8 km long and 6.6 km wide [41].…”

“…Its total area is approximately 60 km 2 , and the average depth is 23 m, with a maximum depth of 45-50 m at the Bay's entrance, and the volume is estimated to be about 1.4 km 3 [26,32,35]. According to the bathymetric and morphological characteristics, two clearly different parts of the Bay can be differentiated: the deeper central-east part and the shallower west part [22] (Figure 1). The only permanent surface stream that flows into the Bay is the Jadro River, bringing the majority of the freshwater into the Bay [35,42].…”

“…The area is generally built of two types of sediments. The hinterland of the Bay and the Čiovo Island are built of upper Cretaceous limestones, while the coastal area is mostly built of flysch and flysch-like rocks deposited in Eocene [22,[43][44][45].…”

“…These two stations were selected to represent different sedimentary environments, where KC stands for the shallow parts of the Bay, and KK stands for the deep parts. Granulometric analysis was performed using a combination of sieving and Casagrande's areometric method [22]. The sediment was first wet-sieved on a sieve with a 0.063 mm mesh.…”

“…It should be noted that the ideal and undisturbed profiles of this shape are characteristic of Croatia and other countries in which 137 Cs fallout originating from the Chernobyl accident was more significant than from atmospheric nuclear weapons testing. Such profiles with characteristic marker peaks are used for sedimentation rate estimation and the radiometric dating of sediments [4,21,22]. However, disturbed or non-ideal 137 Cs profiles, which cannot be used for sedimentation rate estimation and dating, as well as sediments in which no 137 Cs was detected, can still give useful information about sedimentation processes such as erosion, resuspension, resedimentation, focusing, mixing, etc.…”