Tectonic geomorphology and palaeoenvironments of north Peloponnese, Greece : the Pheneos polje case study
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Date
2024-02-02
Authors
Γρουμπού, Μαρία
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Abstract
This thesis project involves the study of the Pheneos palaeolake in north Peloponnese, Greece, which has been recorded in historical archives. The main scope of the thesis is to investigate the step-like scarps on the south margins of Pheneos polje believed to be the relict shorelines of the palaeolake. Moreover, the palaeoenvironmental conditions that prevailed in the palaeolake were also investigated, as well as the possible role that tectonics played in the formation of the basin and the evolution of the palaeolake.
High resolution orthophotos and Digital Surface Models from the study area were examined to locate and map the step-like scarps on the south margins of Pheneos polje and to investigate the possible role of tectonics. Sixty-eight sediment samples were collected and analyzed from Pheneos palaeolake for micropalaeontological analysis. The samples were mostly collected from the south margins that correspond to the palaeoshorelines of the lake and from natural sections across a natural stream that runs across the polje. Charophytes and ostracods were used for the palaeoenvironmental interpretation of Pheneos palaeolake. To place our material in a chronological frame the Amino Acid Racemization (AAR) dating method was employed on opercula of Bithynia.
The main findings of the present thesis show that the step-like scarps on the margins of the polje are alterations of coarse-grained gravels and fine grained material rich in gravels deposited in lacustrine palaeoshorelines. It seems that at least four different palaeoshorelines have prevailed in Pheneos polje and left their micropalaeontological and geomorphological traces during the different fluctuation levels of the palaeolake. The AAR dating results point to a mid-late Holocene age for the herein studied material. The micropalaeontological results illustrate for the first time the presence of five charophyte and ten ostracod taxa from Pheneos palaeolake. Moreover, the micropalaeontological results support that significant changes regarding the trophic status, temperature, and hydrodynamics of Pheneos lake took place during the mid-late Holocene. Based on the ecological requirements of the living charophyte and ostracod species, up to three limnological conditions were distinguished: 1) stable and permanent lake with cold and oligotrophic waters dominated by Nitellopsis obtusa, Candona neglecta, and Ilyocypris inermis which prevailed in the first and second palaeoshorelines and have been dated as the most recent 2) meso-eutrophic lake with warmer waters dominated by Chara vulgaris and Chara sp. and which are hosted in palaeoshorelines 3 and 4 and which consist the oldest limnological state 3) ephemeral lake with an annual cycle rich in Sphaerochara prolifera which prevailed at approximately 710 m altitude. The geomorphological evidence suggests that orthophoto maps and digital surface models of 4 cm spatial resolution are excellent for detecting and mapping palaeoshorelines. Finally, tectonics seem to have played an important role in the deepening of the polje and the formation of the palaeoshorelines.
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Keywords
Micropalaeontology, Palaeolimnology, Palaeoshorelines, Charophytes