Ivona Ivkić Filipović, M.Geol.
Paleolimnology is a scientific discipline that focuses on past conditions and processes in lake basins (Last & Smol, 2001). Paleolimnologists use physical, chemical and biological indicators in lake sediments to determine the paleoenvironment and evolution of lake systems. Lakes are temporary inland water bodies characterized by sedimentation of autochthonous and allochthonous material derived from the catchment area. The accumulation of material leads to a progressive shallowing of lakes, and the end of their natural cycle is marked with cessation of lake sediment deposition (hence „temporary“). Lake environments are often marked by high rates of sedimentation due to a large catchment:lake area ratio. Furthermore, lakes are especially sensitive to environmental changes governed by climatic variations and human influences. Finally, lake sediments are often well-preserved within the relatively enclosed basins. Such undisturbed, fine-layered lake sediments can provide very valuable and continuous paleoenvironmental and paleoclimatic records (Cohen, 2003) (Figure 1). The most common types of lakes in the world are glacial, tectonic, fluvial, coastal and volcanic crater lakes, while the most common lakes in Croatia are karst lakes.
Figure 1. Sedimentation scheme in a lake environment. Main factors controlling the lake sedimentation are geology of the catchment area, climate and anthropogenic influences. Lake sediments are usually drilled with a floating platform and piston corer, while lake sediments core in the karst poljes can be obtained by percussion drilling (modified from Barker (2009) & Bloesch (2004)).
Karst lakes are terrestrial water bodies connected with groundwater through an underground karstic system (Cohen, 2003). They are often formed as a result of the collapse of rocks and/or unconsolidated material into an underground cave. Thus, they are dolines (sinkholes) filled with water. Karst lakes in Croatia are often associated with karst poljes (karst fields), where they form permanent (e.g. Red Lake and Blue Lake near the city of Imotski) or ephemeral lakes (Prološko Blato in Imotsko polje, Bribir-Ostrovica polje). Also, karst poljes often host Quaternary paleolakes, which are dried out naturally or artificially for irrigation purposes (e.g. Prološko Blato, Bokanjačko Blato, Nadinsko Blato). A very important group of karst lakes in Croatia are those associated with karst rivers and tuffa barriers (Plitvice Lakes, Visovac Lake). Along the eastern Adriatic coast there are several lakes connected with the Adriatic Sea through a karstic underground, whose evolution and deepening were influenced by the Holocene sea-level rise (Velo Blato and Kolansko Blato on the Pag island, Vrana Lake, Veliko Lake and Malo Lake on the Mljet island, etc.). Thus, karst lakes in Croatia represent favorable environments for multidisciplinary paleolimnological research, which can provide valuable insight into climate variations during the Quaternary, sea-level changes, tectonics, geomorphological processes and recent human impact.
Figure 2. Geomorphology of the Prološko Blato in Imotsko polje (Dalmatian hinterland). Prološko Blato is a karst wetland characterized with seasonal inundation. Detail paleolimnological research showed that the Prološko blato consist of the Late Quaternary paleolake sediments in western part, and modern Prološko Lake in eastern part. Geomorphological study of the Prološko Lake showed that it formed as a results of collapsing of the eastern border of the polje built of Cretaceous limestones, i.e. it is a collapse doline (sinkhole) filled with water, which has a function of an estavelle.
The goal of doctoral thesis is to reconstruct paleoenvironmental changes of karst lakes using paleolimnological research methods. Focus is set on two paleolakes within karst poljes (Prološko Blato in Imotsko polje and Bribir-Ostrovica polje), whose evolution can be tracked during the Holocene. These lakes have distinctive morphological features (Figure 2), and are characterized by authigenic carbonate sedimentation rich in macro- and microfossils remains, especially ostracods, a very popular group of microfossils often used in paleoenvironmental research. Ostracods can often ensure the information on climatic variations, such as changes in precipitation and temperature. The results of this research will fill the gap in our knowledge regarding the evolution of karst poljes in the Dinarides since the Last Glacial Period, which was controlled by abrupt climate change during the Pleistocene and Holocene transition, by geomorphological processes and anthropogenic activity.
Literature:
Barker, P. (2009). Paleolimnology. In V. Gornitz (Ed.), Encyclopedia of Paleoclimatology and Ancient Environments (pp. 738–743). Springer.
Bloesch, J. (2004). Sedimentation and lake sediments formation. In P. E. O’Sullivan & C. S. Reynolds (Eds.), The Lakes Handbook: Limnology and Limnetic Ecology (Volume 1, pp. 197–229). Blackwell Publishing.
Cohen, A. S. (2003). Paleolimnology: The History and Evolution of Lake Systems. Oxford University Press, Inc.
Last, W.M., & Smol, J. P. (2001). An introduction to physical and geochemical methods used in paleolimnology. In William M. Last & J. P. Smol (Eds.), Tracking Environmental Change Using Lake Sediments Vol 2: Physical and Geochemical Methods (p. 504). Kluwer Academic Publisher.
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Ivona Ivkić Filipović, M.Geol.
PhD student at the Faculty of Mining, Geology and Petroleum Engineering, who conducts her research at the Croatian Geological Survey. Doctoral disseration focuses on paleolimnological reconstruction of karst lakes in Croatia, through which she will specialize in sedimentological and geomorphological processes, and micropaleontological analyses of ostracods as paleoenvironmental indicators.
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ResearchGate: https://www.researchgate.net/profile/Ivona-Ivkic-Filipovic
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