This study deals with the analysis of the glacial processes that have affected the relief of Mt Chelmos in northern Peloponnesus, Greece during middle and Late Pleistocene. The goal was to compile a combined geomorpho...This study deals with the analysis of the glacial processes that have affected the relief of Mt Chelmos in northern Peloponnesus, Greece during middle and Late Pleistocene. The goal was to compile a combined geomorphological-geological map of the study area which would enable the chronological stratification of the glacial landforms cropping up on Mt. Chelmos. Chronological stratification was further aided by optically stimulated luminescence(OSL)dating. The map served as the basis upon which the reconstruction and discussion on the phases of the Middle-Late Quaternary paleoclimatic history of Mt.Chelmos have been made. A sophisticated semiautomated method was first used to analyze the Digital Elevation Model(DEM), combined with Aster,Quickbird and ALOS imagery in order to identify glacial and periglacial, as well as karstic features.Then, these features along with other nonrecognizable features from the remote-sensing images were documented in the field. In this way, several glacial landforms were identified, such as moraines and cirques, indicating extended glaciation phases during the middle and Late Pleistocene. Additionally,a ground moraine located at an altitude of 1900-2050 m, within the Spanolakos glacial valley, was dated using the OSL-dating method. The resulting ages indicate a phase of glacier advance/stabilization during MIS-5 b(89-86 ka), which is in consistence with pollenrecord evidence from Greece and the Mediterranean.elevations above the floors of the highest cirques on Mount Tymphi(Hughes 2004). These glacial landforms postdate the youngest moraines on Mount Tymphi(Tymphian Stage MIS 5 d-2), and it has been argued that they might be Younger Dryas in age(Woodward and Hughes 2011) although this has not been confirmed by radiometric dating(Hughes et al. 2006 d).Recent field observations throughout the mountains of central Greece(Leontartitis and Pavlopoulos, unpublished data) demonstrate that the glaciation extent has been underestimated in several locations. In particular, it has been claimed that evidence of glaciation is present only in mountains that exceed 2200 m in altitude(Woodward and Hughes 2011). However, in Evritania(e.g. Mt Chelidona, Mt Kaliakouda, South Agrafa) as well as in Thessaly(Agrafa-also mentioned by Hunt and Sugden 1964), several glacial landforms such as glacial cirques and wellpreserved extensive moraine complexes have been confirmed for the first time, following some minor reports from the pioneer geographer Mistardis(1937 a). In many occasions, these mountains do not exceed 2000 m. Moreover, evidence for extensive glaciation phases has also been found in the mountains of southern central Greece. These findings confirm the early reports for Mt Parnassus(Mistardis 1937 a; Pechoux 1970), Mt Giona and Mt Vardousia(Mistardis 1937 a). Dating of the glacial landforms found in the above-mentioned, onceglaciated mountains is of great importance for understanding the missing links between Northern Greece and Peloponnesus. These links can finally contribute to the clarification of striking contradictions emerging from both areas.In the mountains of Peloponnesus(e.g.Taygetos, Chelmos, Erymanthos) several researchers have identified glacial landforms(Philippson 1892; Maull 1921; Mistardis 1937 a,b,c,1946; Mastronuzzi et al. 1994; Pope et al. 2017).The first studies on Mt Chelmos report cirques,moraines, perched boulders and ice-moulded bedrock which are generally attributed to Quaternary glaciers(Philippson 1892; Maull 1921;Mistardis 1937 a,b,c, 1946), while Mastronuzzi et al.(1994) date them to Late Pleistocene age. However,the geochronology and the palaeoclimatic context of this glacial evidence have been only partly explored so far. In particular, the only systematicstudy that has been conducted on Mt Chelmos is by Pope et al.(2017). Their results(based on cosmogenic-36 Cl dating of glacial boulders) showed that quite extensive moraine complexes are the result of glacier advance/stabilization during two phases in Late Pleistocene, at 40-30 ka and 13-10 ka respectively, and a glacial retreat phase during23-21 ka.The first glacial advance stage suggests that the local Late Pleistocene Last Glacial Maximum(LGM) predates the global LGM during 23-21 ka and is in accordance with evidence from other mountains across the Mediterranean(Pope et al.2017), namely northern Spain(Serrano et al. 2012 a,b), the Italian Apennines(Federici et al. 2012) and Turkey(Sarikaya et al. 2014) opening up a new perspective on the study of the Tymphian Stage.Practically, as the latitude difference of the two mountains(Mt Chelmos and north Pindus/Mt Tymphi) is relatively small, any differences in the extent of glaciations should mainly be attributed to precipitation differences rather than temperature differences, implying a relatively wet climate in southern Greece during these periods. This kind of information is very useful for circulation models and generally for the reconstruction of the palaeoclimate of the eastern Mediterranean. However, at this stage it is not possible to compare the findings from the two mountains as the glacial record of Mt Tymphi lacks chronological constraints for the period between MIS-5 d and MIS-2(Tymphian Stage and Younger Dryas).The stage of glacier retreat(23-21 ka) in Mt Chelmos, around the global LGM(22-20 ka), is consistent with evidence of dry conditions around the LGM from northern Greece(Pope et al. 2017),as mentioned above. Finally, the last glacial advance phase(13-10 ka) probably corresponds to the Younger Dryas(12.9-11.7 ka), being consistent with evidence from Montenegro(Hughes et al.2010, 2011) and the Italian Maritime Alps(Federici et al. 2012). This is of great significance since there is no obvious agreement on the severity of the climatic deterioration during the Younger Dryas in the eastern Mediterranean(Hughes et al. 2003;Pope et al. 2017). According to some researchers,the Younger Dryas event is scantly represented in the eastern Mediterranean pollen records and cannot be perceived as a sudden deterioration of climatic conditions(Bottema 1995; Lawson et al.2004). On the other hand, there are authors claiming that the Younger Dryas is characterized by cold and arid conditions, as seen from sea–land correlations of pollen records in the eastern Mediterranean(Rossignol-Strick 1995).The goal of this paper is to further study the glacial history of Mt Chelmos in an effort to complete the chronostratigraphical framework of Quaternary glaciation phases in the mountains of Greece. With this intention, we compiled a combined geomorphological-geological map that enables the chronological stratification of the glacial sedimentary units that have already been identified and dated on Mt Chelmos. Additionally,new evidence on the glacial history of Mt Chelmos is presented through relative and numerical(OSL-Optically Stimulated Luminescence) dating. Finally,the geomorphological map serves as the basis upon which the reconstruction/correlation and discussion on the phases of the Middle-Late Quaternary palaeoclimatic history of Mt. Chelmos can be made.展开更多
文摘This study deals with the analysis of the glacial processes that have affected the relief of Mt Chelmos in northern Peloponnesus, Greece during middle and Late Pleistocene. The goal was to compile a combined geomorphological-geological map of the study area which would enable the chronological stratification of the glacial landforms cropping up on Mt. Chelmos. Chronological stratification was further aided by optically stimulated luminescence(OSL)dating. The map served as the basis upon which the reconstruction and discussion on the phases of the Middle-Late Quaternary paleoclimatic history of Mt.Chelmos have been made. A sophisticated semiautomated method was first used to analyze the Digital Elevation Model(DEM), combined with Aster,Quickbird and ALOS imagery in order to identify glacial and periglacial, as well as karstic features.Then, these features along with other nonrecognizable features from the remote-sensing images were documented in the field. In this way, several glacial landforms were identified, such as moraines and cirques, indicating extended glaciation phases during the middle and Late Pleistocene. Additionally,a ground moraine located at an altitude of 1900-2050 m, within the Spanolakos glacial valley, was dated using the OSL-dating method. The resulting ages indicate a phase of glacier advance/stabilization during MIS-5 b(89-86 ka), which is in consistence with pollenrecord evidence from Greece and the Mediterranean.elevations above the floors of the highest cirques on Mount Tymphi(Hughes 2004). These glacial landforms postdate the youngest moraines on Mount Tymphi(Tymphian Stage MIS 5 d-2), and it has been argued that they might be Younger Dryas in age(Woodward and Hughes 2011) although this has not been confirmed by radiometric dating(Hughes et al. 2006 d).Recent field observations throughout the mountains of central Greece(Leontartitis and Pavlopoulos, unpublished data) demonstrate that the glaciation extent has been underestimated in several locations. In particular, it has been claimed that evidence of glaciation is present only in mountains that exceed 2200 m in altitude(Woodward and Hughes 2011). However, in Evritania(e.g. Mt Chelidona, Mt Kaliakouda, South Agrafa) as well as in Thessaly(Agrafa-also mentioned by Hunt and Sugden 1964), several glacial landforms such as glacial cirques and wellpreserved extensive moraine complexes have been confirmed for the first time, following some minor reports from the pioneer geographer Mistardis(1937 a). In many occasions, these mountains do not exceed 2000 m. Moreover, evidence for extensive glaciation phases has also been found in the mountains of southern central Greece. These findings confirm the early reports for Mt Parnassus(Mistardis 1937 a; Pechoux 1970), Mt Giona and Mt Vardousia(Mistardis 1937 a). Dating of the glacial landforms found in the above-mentioned, onceglaciated mountains is of great importance for understanding the missing links between Northern Greece and Peloponnesus. These links can finally contribute to the clarification of striking contradictions emerging from both areas.In the mountains of Peloponnesus(e.g.Taygetos, Chelmos, Erymanthos) several researchers have identified glacial landforms(Philippson 1892; Maull 1921; Mistardis 1937 a,b,c,1946; Mastronuzzi et al. 1994; Pope et al. 2017).The first studies on Mt Chelmos report cirques,moraines, perched boulders and ice-moulded bedrock which are generally attributed to Quaternary glaciers(Philippson 1892; Maull 1921;Mistardis 1937 a,b,c, 1946), while Mastronuzzi et al.(1994) date them to Late Pleistocene age. However,the geochronology and the palaeoclimatic context of this glacial evidence have been only partly explored so far. In particular, the only systematicstudy that has been conducted on Mt Chelmos is by Pope et al.(2017). Their results(based on cosmogenic-36 Cl dating of glacial boulders) showed that quite extensive moraine complexes are the result of glacier advance/stabilization during two phases in Late Pleistocene, at 40-30 ka and 13-10 ka respectively, and a glacial retreat phase during23-21 ka.The first glacial advance stage suggests that the local Late Pleistocene Last Glacial Maximum(LGM) predates the global LGM during 23-21 ka and is in accordance with evidence from other mountains across the Mediterranean(Pope et al.2017), namely northern Spain(Serrano et al. 2012 a,b), the Italian Apennines(Federici et al. 2012) and Turkey(Sarikaya et al. 2014) opening up a new perspective on the study of the Tymphian Stage.Practically, as the latitude difference of the two mountains(Mt Chelmos and north Pindus/Mt Tymphi) is relatively small, any differences in the extent of glaciations should mainly be attributed to precipitation differences rather than temperature differences, implying a relatively wet climate in southern Greece during these periods. This kind of information is very useful for circulation models and generally for the reconstruction of the palaeoclimate of the eastern Mediterranean. However, at this stage it is not possible to compare the findings from the two mountains as the glacial record of Mt Tymphi lacks chronological constraints for the period between MIS-5 d and MIS-2(Tymphian Stage and Younger Dryas).The stage of glacier retreat(23-21 ka) in Mt Chelmos, around the global LGM(22-20 ka), is consistent with evidence of dry conditions around the LGM from northern Greece(Pope et al. 2017),as mentioned above. Finally, the last glacial advance phase(13-10 ka) probably corresponds to the Younger Dryas(12.9-11.7 ka), being consistent with evidence from Montenegro(Hughes et al.2010, 2011) and the Italian Maritime Alps(Federici et al. 2012). This is of great significance since there is no obvious agreement on the severity of the climatic deterioration during the Younger Dryas in the eastern Mediterranean(Hughes et al. 2003;Pope et al. 2017). According to some researchers,the Younger Dryas event is scantly represented in the eastern Mediterranean pollen records and cannot be perceived as a sudden deterioration of climatic conditions(Bottema 1995; Lawson et al.2004). On the other hand, there are authors claiming that the Younger Dryas is characterized by cold and arid conditions, as seen from sea–land correlations of pollen records in the eastern Mediterranean(Rossignol-Strick 1995).The goal of this paper is to further study the glacial history of Mt Chelmos in an effort to complete the chronostratigraphical framework of Quaternary glaciation phases in the mountains of Greece. With this intention, we compiled a combined geomorphological-geological map that enables the chronological stratification of the glacial sedimentary units that have already been identified and dated on Mt Chelmos. Additionally,new evidence on the glacial history of Mt Chelmos is presented through relative and numerical(OSL-Optically Stimulated Luminescence) dating. Finally,the geomorphological map serves as the basis upon which the reconstruction/correlation and discussion on the phases of the Middle-Late Quaternary palaeoclimatic history of Mt. Chelmos can be made.
