engleski

Late Holocene relative sea-level change and palaeoearthquakes at the Elafiti islands (Southern Adriatic, Croatia)

Littoral rims built by the coralline rhodophyte Lithophyllum byssoides are a particularly precise archive of relative sea-level histories (Laborel et al., 1983, 1994). Their vertical precision, in the microtidal environment, comes from the restricted environmental conditions of the alga as their living range is constrained around sea-level (Pérès and Picard, 1952, 1964). The temporal component is obtained through 14C dating. For construction of precise geochronologies from marine-derived carbon samples accurate calibration of radiocarbon dates is needed. In order to approach the 14C reservoir effect of the alga different studies have been engaged using samples of known age from museum collections (Faivre et al., 2015, 2019). The corrections of the marine radiocarbon reservoir effect (MRE) and local R (deviations from global average marine reservoir age of ocean surface waters) are fundamental particularly for the short, late Holocene sea- level and palaeoenvironmental chronologies. The Elafiti islands are located along the southern part of the eastern Adriatic coast between Dubrovnik and the Pelješac peninsula (Fig. 1). The island group consists of five major islands including the studied Lopud and Koločep islands. Studying algal rims together with tidal notches and Lithophaga lithophaga borehole upper limits, two elevated palaeoshorelines have been distinguished on Lopud, Koločep and Grebeni islands and islets. Detailed survey of relative sea-level markes allowed the distinction of seismotectonically uplifted sectors of coast. The established high-resolution geochronology based on 77 radiocarbon dates, enables to separate coseismic uplift events from periods of interseismic subsidence. Two successive major earthquakes affected approximately 5 km of coasts, in the Pelješac- Dubrovnik fault zone, with an uplift amplitude between 40 and 80 ± 15 cm per event (Fig. 2). The earlier, older events, caused larger displacements (60-80 cm), while the later, younger events, revealed on average lower displacements (40-55 cm) corresponding to the 1520 AD quake and the 1667 Dubrovnik earthquake (Fig. 2). The cumulative offsets increase from 0.57 ± 0.15 m at Lopud (Faivre et al., 2021a) to 1.00- 1.25 ± 0.15 m at Koločep and Grebeni (Faivre et al., 2021b). After correction for local coseismic displacements, the sea-level trends were quantified with full consideration of the available uncertainty at Lopud island (Faivre et al., 2021a) what allow us to approach the drivers of relative sea-level change in the Southern Adriatic. This high-resolution study confirmed the precision of L. byssoides bioconstructions not only in studies of relative sea-level variations but also in the studies of palaeoearthquakes in seismotectonically active areas. Also, thanks to high resolution geochronology of algal rims, we were able to approach the morphogenesis and trace the evolution of tidal notches in the studied area. This research was supported by Croatian Science Foundation project HRZZ-IP-2019-04-9445 – Relative sea-level change and climate change along the eastern Adriatic coast – SEALeveL.

Lythophilum rims ; Tidal notch ; Lithophaga lithophaga boreholes ; Palaeoearthquakes ; Palaeoshoreline ; Coseismic movements ; Dubrovnik ; Central Mediterranean Coastal geomorphology

nije evidentirano