A Reseach Of Coastal Geomorphological Features And Causes On The North Coast Of Haitan Island In Fujian

Quaternary stratas were divided into Tianbao formation of Lower Pleistocene,Tongan formation of Middle Pleistocene,Longhai formation of Upper Pleistocene,Dongshan formation of Lower Holocene,Changle formation of Middle Holocene,Jiangtian formation of Upper Holocene in Fujian Province.Three main stages of Mid-Pleistocene vermiculated red soils in southern China include the formation of the homogeneous matrix of a red soil,development of the white veins within the soil profile,and formation of juxtaposed textural features.There was great difference in the reconstruction modes of sea level changes during the late Quaternary of Fujian coastal areas.The ""O1d Red Sand" was a common product caused by wind transportation of coastal aeolian sand and laterization in the later period since the Last interglacial in the south coast of China.The Haitan Island of Fujian locates on the west of Taiwan Strait,complex and diverse geomorphological types on the north coast of Haitan Island.The Quaternary sediments difference in the aspects of lithology,sedimentary thickness,sedimentary facies and relatively complete Quaternary sedimentary sequences of long timescale,may providing good recording materials to answer these questions.In this paper,based on the principle of coastal geomorphology,sedimentology,geology and petrology,we focused on judging the coastal geomorphological features and causes on the north coast of Haitan Island on the basis of field observation and sampling,collecting geological,topographic maps and high-resolution Google Maps,indoor experimental analysises,comprehensive analysis and regional comparison.Some preliminary conclusions are achieved:(1)The rocky coast is composed of intrusive granite and volcanic rock on the north coast of Haitan Island.Marine erosion geomorphology development,the main types of marine erosion geomorphology including:cliff,sea cave,sea arch,shore platform,sea stack and so on.Granite rock was granitic magma intruded in tectonic movements and then experienced uplifting,especially the fault block uplifting,its upper weathered mantle was eroded and exposed to the earth's surface.Granite rock was formed in Late Yanshan epoch.Volcanic rock was formed after the magma spewed the earth's surface and condensation in the process of volcanic activity,it was inferred that volcanic rock was formed in Late Jurassic epoch.Igneous rock development of typical stone-egg landscape.(2)At the early stage of evolution of rocky coast,coastal cape suffered erosion and developed into cliff;With the further evolution of rocky coast,large-scale bench and cliff formed at the headland;With the erosic.of cape,forming rectification coast of gritty coast alternated with rocky coast;When cliff was eroded back to the gulf shoreline,headland had been completely eroded,forming the broad bench.Under the protection of the broad bench,cliff was no longer eroded,forming relatively stable coast and flat rocky rectification coast.(3)The main types of sandy coast geomorphology including:sandy beach,platform and tiebar.Sandy beaches were classified as cape-bay and straightened sandy beaches.The grain-size characteristics of sandy beaches were closely related to orientation of the coastline,wave energy and tidal range,topography and provenance condition.The Jingsha platforms were mainly caused by aeolian deposit since the Last interglacial.The degree of weathering of third laterite platform was higher than second and first laterite platform,the latter suffered intensive wave erosion in later geomorphic evolution period.(4)In the early geomorphic evolution of soft-cliff in Jingsha,development of the aeolian "Old Red Sand" deposits under the background of the warm-wet climate in the Last interglacial.Jun Mountain subjected to intense physical weathering and produced a large number of clastic rock under Last Glacial Maximum(LGM)of the cold dry climate,developed piedmont diluvial layer and covered the base level of denudation of "Old Red Sand" during the climate transition phase of postglacial period.Long-term erosion of wave,tidal power causing shoreline erosion back to the south under the background of rising sea level fluctuations since postglacial,development into present soft-cliff landscape.(5)The soft-cliff in Liushui recorded the rise and fall of sea-level alternately during early Pleistocene of Quaternary,LS deposited alternately by shallow sea and continental sediment and composed geomorphic basis of the tiebar.Converted continental sedimentary environment since the late mid-pleistocene and development of multi layers of "Old Red Sand" deposits under the background of the warm-wet climate.LS also development into soft-cliff landscape under the background of rising sea level fluctuations since late glacial epoch.The geomorphic evolution process of modern times in LS was mainly wave and sand erosion effect and the shoreline erosion back to the south under strong wave erosion.(6)Although the difference of early sedimentary formation process was obvious between JS and LS soft-cliff,the geomorphic evolution process of soft-cliff was similar under the background of rising sea level fluctuations since postglacial.In general,the evolution process of soft-cliff on the north coast of Haitan Island was drived by internal and external force of crustal movement,climatic change,sea-level change and wave action.(7)The main controling factors of geomorphic evolution on the north coast of Haitan Island including:geological structure,lithology,sea level change and the impact of coastal tide,wave and wind.Geological structure shaped the distribution pattern of coastal landscape on a macro level.Lithology was the material basis of coastal landscape.Sea level change,coastal tide,wave and wind were on the basis of macro distribution pattern of coastal landscape to affect further the geomorphic evolution.