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Algal rims as markers of 2ka relative sea-level change and climate change in the Eastern Adriatic

The sea level changes at varying rates in time and space are the result of the interplay of three principal contributions: eustatic, glacio-hydroisostatic and tectonic. The first is global and time dependent, while the other two also vary according to location. Within the studies of late Holocene relative sea-level change along the Croatian Adriatic coast, different markers (e.g. archaeological, geomorphological, sedimentological) have been used till now. However, most of the methods used do not provide enough precision needed for a real step forward. Due to the short studying period the error bars are too large to enable precise conclusions. Here we present new data obtained using bioconstructions as sea-level markers. Fossil bio-constructions have proven to be precise sea-level indicators in microtidal environments. Radiocarbon dating of algal rims created by alga Lithophyllum byssoides (Lamarck) Foslie (formerly L. lichenoides Philippi) allow us to study the relative sea-level change with higher precision and consistency. Under favourable conditions Lithophyllum byssoides build up reef like bio-constructions just above the biological mean sealevel which can be dated by radiocarbon. The 14C ages of algal carbonates formed in the marine environment have been corrected for the Marine Reservoir Effect. Algal rims from different locations along the Eastern Adriatic have been analysed and related to phases of relative sea-level changes during last two thousand years. In the Central Adriatic large algal rims grew during two relatively colder periods: the Dark Ages Cold Period and the Little Ice Age while in the Northern Adriatic the rims were formed during the Medieval Climate Anomaly. The obtained results are further systematically related to other available sea-level markers.

algal rim; sea-level change; climate change; Adriatic

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