Fluvial geomorphology is affected by physical conditions which allow its adaptation due to high dynamics and environmental influences. Fluvial morphological changes are manifested as a result of tendency of the river ...Fluvial geomorphology is affected by physical conditions which allow its adaptation due to high dynamics and environmental influences. Fluvial morphological changes are manifested as a result of tendency of the river system to maintain its physical balance. Our study area is the upper and middle flow part of Vouraikos river and surrounding area, near the NW border of Chelmos mountain in Northern Peloponnese, near the town of Kalavrita, at an altitude of 800 m. The area is part of the Skepasto basin, constituting of a graben with a general E-W direction that was developed NW of Kalavrita. The area comprises of Mesozoic, Upper Triassic-Jurassic limestone and dolomite of the Tripolitsa unit External Hellenides and Plio-Pleistocene fluvio-lacustrine sequences, while its tectonic structure is characterized mainly by normal faults. The geomorphological landscape is characterized by alluvial deposits and important geomorphological features including fluvial terraces, alluvial fans, fluvial scarps and their main rill washes. This area has been a place of major human activity as shown by the findings of many uncovered artifacts and a settlement. Through a paleographic reconstruction, detailed field investigations, in combination with the compilation of geomorphological maps using GIS software and archaeological evidence found in the area, we attempted to reconstruct the fluvial evolution of Vouraikos river and identify the major geomorphological factors that led to, and influenced it. Finally, the link between cultural activities and sedimentary processes is also studied. The recorded environmental variations had a great impact on the geomorphological shaping and instability of Kalavrita plain and Vouraikos river and are being reflected on the buried settlement. Sediment fluxes were high enough to form strath terraces, while local tectonics aided in the strath and fill terrace creation. Smaller and younger strath terraces, formed during increased sediment supply periods, when the valley was at a higher level.展开更多
[ Objective] The aim was to study the natural environment of Karst mountain areas in northern Guangdong. [ Method] Through the col- lection of topography, climate, soil and vegetation data in the Karst mountain areas ...[ Objective] The aim was to study the natural environment of Karst mountain areas in northern Guangdong. [ Method] Through the col- lection of topography, climate, soil and vegetation data in the Karst mountain areas of Northern Guangdong, combined with field investigation, the natural environment of Karst mountain areas in northern Guangdong was analyzed. [ Result] The Karst topography of the area is widely distributed. Most places were in subtropical climate zone, with high temperature and rainfall in the same period, and abundant precipitation. There was a large area of contiguous distribution of limestone with dissolution area. Vegetations included typical limestone evergreen and deciduous broadleaved mixed forest, limestone shrub and grassy slopes in mountain and hill. Limestone vegetation had typical limestone mixed evergreen broadleaf forest, limestone shrub, limestone hilly mountain grass slope. [ Conclusion] The study provided theoretical basis for the protection of natural environment of Karst mountain areas in northern Guangdong.展开更多
The morphology and internal structure of the Horaine Bank(Bay of Saint-Brieuc,NW France)are described based on multibeam echosounder and high-resolution seismic datasets coupled with vibro-core data.The Horaine Bank s...The morphology and internal structure of the Horaine Bank(Bay of Saint-Brieuc,NW France)are described based on multibeam echosounder and high-resolution seismic datasets coupled with vibro-core data.The Horaine Bank shows large-scale bedforms in the lee of a submerged rocky shoal,which allowed defining it as a Banner Bank.The internal structure of the sandbank reveals four seismic units(U1-U4)on a Cambrian basement(U0).The basal unit U1 is interpreted as reworked lowstand fluvial sediments those infilled micro incised valleys during a rise in sea level.This unit is overlain by paleo-coastal barrier sand-spit(U2)whose development was controlled by swell in the context of a rapid rise in sea level.The successive prograding unit(U3)is interpreted as flooding deposits in continuity with unit U2.The unit U4 is characterized by oblique reflectors oriented in two opposite directions.This last unit,dated post 3500 yr BP,corresponds to migrating dunes superimposed on the bank and observable in the high-resolution bathymetric data.The strong correlation between tidal currents and the apparent clockwise migration of dune crests suggests the presence of a tidal gyre controlling the present-day dynamics of most of the Horaine bank dunes.This study proposes a new model for the construction of banner banks characterized by the gradual transition of a sand spit to a banner bank during marine transgression and ensuing hydrodynamic variability.展开更多
文摘Fluvial geomorphology is affected by physical conditions which allow its adaptation due to high dynamics and environmental influences. Fluvial morphological changes are manifested as a result of tendency of the river system to maintain its physical balance. Our study area is the upper and middle flow part of Vouraikos river and surrounding area, near the NW border of Chelmos mountain in Northern Peloponnese, near the town of Kalavrita, at an altitude of 800 m. The area is part of the Skepasto basin, constituting of a graben with a general E-W direction that was developed NW of Kalavrita. The area comprises of Mesozoic, Upper Triassic-Jurassic limestone and dolomite of the Tripolitsa unit External Hellenides and Plio-Pleistocene fluvio-lacustrine sequences, while its tectonic structure is characterized mainly by normal faults. The geomorphological landscape is characterized by alluvial deposits and important geomorphological features including fluvial terraces, alluvial fans, fluvial scarps and their main rill washes. This area has been a place of major human activity as shown by the findings of many uncovered artifacts and a settlement. Through a paleographic reconstruction, detailed field investigations, in combination with the compilation of geomorphological maps using GIS software and archaeological evidence found in the area, we attempted to reconstruct the fluvial evolution of Vouraikos river and identify the major geomorphological factors that led to, and influenced it. Finally, the link between cultural activities and sedimentary processes is also studied. The recorded environmental variations had a great impact on the geomorphological shaping and instability of Kalavrita plain and Vouraikos river and are being reflected on the buried settlement. Sediment fluxes were high enough to form strath terraces, while local tectonics aided in the strath and fill terrace creation. Smaller and younger strath terraces, formed during increased sediment supply periods, when the valley was at a higher level.
基金Supported by Guangdong Excellent Innovational Youth Training Program(LYM11126)National Natural Science Fund(30870469,31170486)
文摘[ Objective] The aim was to study the natural environment of Karst mountain areas in northern Guangdong. [ Method] Through the col- lection of topography, climate, soil and vegetation data in the Karst mountain areas of Northern Guangdong, combined with field investigation, the natural environment of Karst mountain areas in northern Guangdong was analyzed. [ Result] The Karst topography of the area is widely distributed. Most places were in subtropical climate zone, with high temperature and rainfall in the same period, and abundant precipitation. There was a large area of contiguous distribution of limestone with dissolution area. Vegetations included typical limestone evergreen and deciduous broadleaved mixed forest, limestone shrub and grassy slopes in mountain and hill. Limestone vegetation had typical limestone mixed evergreen broadleaf forest, limestone shrub, limestone hilly mountain grass slope. [ Conclusion] The study provided theoretical basis for the protection of natural environment of Karst mountain areas in northern Guangdong.
文摘The morphology and internal structure of the Horaine Bank(Bay of Saint-Brieuc,NW France)are described based on multibeam echosounder and high-resolution seismic datasets coupled with vibro-core data.The Horaine Bank shows large-scale bedforms in the lee of a submerged rocky shoal,which allowed defining it as a Banner Bank.The internal structure of the sandbank reveals four seismic units(U1-U4)on a Cambrian basement(U0).The basal unit U1 is interpreted as reworked lowstand fluvial sediments those infilled micro incised valleys during a rise in sea level.This unit is overlain by paleo-coastal barrier sand-spit(U2)whose development was controlled by swell in the context of a rapid rise in sea level.The successive prograding unit(U3)is interpreted as flooding deposits in continuity with unit U2.The unit U4 is characterized by oblique reflectors oriented in two opposite directions.This last unit,dated post 3500 yr BP,corresponds to migrating dunes superimposed on the bank and observable in the high-resolution bathymetric data.The strong correlation between tidal currents and the apparent clockwise migration of dune crests suggests the presence of a tidal gyre controlling the present-day dynamics of most of the Horaine bank dunes.This study proposes a new model for the construction of banner banks characterized by the gradual transition of a sand spit to a banner bank during marine transgression and ensuing hydrodynamic variability.
