| Coastal plain, closely related to the development of marine economy, has become thefocus of the world. The coastal city is at the forefront of China’s economic development in theregion, bring more than70%medium-sized cities and more than12%GDP. Shandong Yantai,as a typical coastal mountain plains city, has become the focus of urban planning andconstruction. It has a very large potential of development and resources utilization. The entireurban landscape undergoing tremendous changes is rapidly changing. In this paper, the studyarea is located in the heart of the new district of Yantai, therefore, recognize the sedimentarycharacteristics and evolution of sedimentary environment of sediments in the study area, ableto better exploitation of coastal resources, better building blue, civilization, happy new Yantai.In this paper, based on particle size analysis, using the graphical method, depositionsusceptibility profile analysis and comprehensive analysis of the sediments. The use of all thenumerical analysis, the study area Quaternary Holocene coastal plain sedimentary sequencestratigraphy, depositional granularity characteristics and evolution of sedimentaryenvironment has been systematically studied to provide a reference for the comprehensivestudy of the specific depositional environment. Jiaodong Peninsula coastal plains ofQuaternary Holocene small, regional analysis of environmental studies, engineering,architecture, hydrogeology, geological disasters investigation has important significance forlocal economic development services, public welfare latest geological information for thepublic, so that geological research work to better serve the public life and social development.1. Holocene Quaternary stratigraphic division. In this paper, a comprehensivecross-sectional study of sedimentary coastal plain area were stratified analysised. Tectonic riftgeological foundation Holocene coastal plain coastal study area changes, the underlying layerof Quaternary soil mica schist and granite. Geomorphic units in the study area are littoral,fluvial sedimentary units of interaction (Alluvial, alluvial geomorphic units), the thicknessof each rock got big change, continuity, uniformity is poor, the analysis may be GuangdangRiver, Xin’an River, river diversion to its impact. Spatial variation of its Holocenestratigraphic thickness of performance: from southwest to northeast direction, that graduallythicken from land to ocean formation. Bedrock buried within a certain depth, shallow depth,from top to bottom is sand, silty clay, sand, silt, coarse sand, fine sand, silty clay, clay and mica brecciated schist, sedimentary sequence with diversified general soil thickness of12~22m, as alluvial, alluvial plain type geomorphic units, more than soft soil bearing capacity isless than100kpa. Multi unconsolidated sediments overlying the bedrock surface and thinnerthan shallow sedimentary structure is relatively simple. More general study area containingsilt or silty sediment thickness mostly2~5m, the thick up to8m, coastal plains and riverterraces larger is the main distribution area. Holocene sea-level changes since the study areais the main cause, the first comprehensive analysis of the sedimentary environment4,5and9layers of marine sediments, Layer3environment paralic sedimentary facies.2. Sedimentary facies analysis. This paper focuses on Holocene sediment particle sizecharacteristics of the study area. Based on previous studies, according to the particle sizefrequency curve characteristics, particle size cumulative probability curves, all the featuresand size parameters curve characteristics and other aspects elaborated particle characteristicsand sedimentary environment changes, the study area derived sediment deposition sourceswith multiple derived, more complex composition, sedimentary layers is also more volatileenvironment. Coastal Plain study area Quaternary Holocene sediments mainly have fourkinds of genetic types, namely: fluvial deposits, eolian deposition, shore lacustrine sedimentsand marine sediments. Sedimentary environments are interactive. Coastal plain of the studyarea to accumulate in marine sediments locally lacustrine sedimentary shore,river,floodplain,river to river on both sides of an alluvial terraces, alluvial-based, tilt piedmont plains andhilly areas with low and Alluvial based, along with the entire study area varying degrees ofaeolian deposition. At the same time based on previous research on the Shandong Peninsula innortheastern transgression range, comprehensive particle size analysis,14C dating andcontour, drawing on the results of previous studies of Shandong Peninsula Holocenetransgression, and to map out the study area Holocene sea invaded range.3. Paleoclimate analysis. This article speculated that the ancient climate changes throughthe sediment magnetic susceptibility analysis. This article is just the change of the magneticsusceptibility were measured sediment core, while climate change reference in the study areaduring the course of the study of other scholars provided for comparison. It can be seen that,if the weather is warm temperate period, then increasing the relative susceptibility more; if theclimate in the cold period, the relative susceptibility is reduced more. This coastal sediments,provided by the land-based sources of iron mineral ingredients, quantities and under certain circumstances, is closely related to chemical changes in heat and cold, dry climate of mutualconversion of arising. Especially in alternating cold and warm climate changes frequently, inan unstable period, we can see that there is a greater susceptibility changes accordingly. Thisis a positive correlation between the change in the overall change in magnetic susceptibilityand grain size. But according to comparison found that different sediments interpreteddepositional environment is different. For example, in river sediments, in a certain degree orextent, magnetic susceptibility can be used as the main basis for the deposition of dynamicconditions and hydrodynamic major strength of proxies, but does not directly reflect thechanges in climate. In lake sediments, comprehensive research and this paper has been formedon the previous experimental results obtained sediment sedimentary section, magneticsusceptibility can change on lake depositional environment and play an indirect role insensitive instructions, to indicate climate change proxies. In the sand sediments, magneticsusceptibility can directly reflect changes in wind strength and direction, and can be used as areference paleoclimate analysis. In marine sediments, the size of the magnetic mineralconcentration of exogenous changes in coastal sediments affect susceptibility.Based on the above research, the paper speculated that the sedimentary environment inthe study area were analyzed the evolution of the coastal plain. Early Holocene, about12~8kaBP, widely developed in the study area coastal region alluvial flood strata, formingalluvial flood plain, according to the aforementioned sediment facies characteristics, thisperiod is still terrestrial environment, paleoclimate cool and slightly dry. Middle Holocene,about8~2.5kaBP, study area and more marine layer top surface elevation in4~5m,5m orless above sea level along the coast now constitute the largest Holocene transgression, the seaalong the river channel, the Gulf was planar invasion, arriving alluvial plains and denudedhills leading edge of the ancient warm and humid climate. After the formation of theHolocene high sea level (about6~5kaBP a more modern form of ancient sea surface height1~3m), and about4kaBP, sea level fluctuations relative decline, coupled with the riveraggradation, about2.5kaBP, the sea withdrew from the study of basic area, is the coastalplain formed. Late Holocene coastal plain in the study area is alluvial-fluvial and alluvialplain depositional environment, fluvial and lacustrine strata development, early late Holocenecool slightly wet, late late Holocene climate change as reflected in line now East Asianclimate change law. |
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